MAY 1985
DEVELOPMENT OF AN ADJUSTABLE BUOYANCY
BALLOON TRACER OF ATMOSPHERIC MOTION
Phase II. Development of an Operational Prototype
ATMOSPHERIC SCIENCES RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NC 27711
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DEVELOPMENT OF AN ADJUSTABLE BUOYANCY
BALLOON TRACER OF ATMOSPHERIC MOTION
Phase II. Development of an Operational Prototype
B. D. Zak and H. W. Church
Sandia National Laboratories
E. W. Lichfield
Technadyne Engineering Consultants
M. D. Ivey
Telemetries Southwest
Interagency Agreement DW930214
Project Officers
J. S. Irwin and R. 6. Lamb
Meteorology and Assessment Division
Atmospheric Sciences Research Laboratory
Research Triangle Park, NC
ATMOSPHERIC SCIENCES RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NC 27711
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NOTICE
The information in this document has been funded by the
United States Environmental Protection Agency under Inter-
agency Agreement OW930214 to Sandia National Laboratories.
It has been subject to the Agency's peer and administrative
review, and it has been approved for publication as an EPA
document. Mention of trade names or commercial products
does not constitute endorsement or recommendation for use.
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ABSTRACT
An Adjustable Buoyancy Balloon Tracer of Atmospheric
Motion is a research tool which allows one to follow
atmospheric flows in both the horizontal and the vertical.
including the weak sustained vertical motion associated with
meso- and synoptic-scale atmospheric disturbances. The design
goals for the Tracer Balloon being developed here specify a
lifetime > 3 days, tracking range .> 1000 km. a ceiling
altitude >. 5.5 km (500 mb). and the capability to respond to
mean vertical flows as low as 1 cm/s. The Tracer Balloon is
also to measure and telemeter selected meteorological
variables, to be sufficiently inexpensive to permit use in
significant numbers, and to be serviced by a ground system
capable of handling several Tracers at a time. While the
Tracer has applications throughout the atmospheric sciences.
the immediate motivation for this effort is to meet the need
to evaluate the accuracies of air pollution transport models,
to establish source-receptor relationships to distances of
order 1000 km. and to assess the inherent limits on the
predictability of source impacts at long distances. In Phase
I of this project, titled "Systems Design and Demonstration of
Feasibility." the authors proposed a generic design for such a
system, subjected the design to theoretical analysis.
constructed a testbed prototype, and conducted a series of
tests with that prototype to evaluate the concept. In Phase
II of the project, the subject of this report, the authors
developed an operational prototype designed to meet the
desired specifications. A limited number of test flights of
the operational prototype were conducted south of Albuquerque,
New Mexico, in a nearly vacant 350-square-mile (900 km2)
area laced with dirt roads. Flights were made using each of
the three currently available control algorithms. Analysis of
the data indicated that, in each case, the control system
functioned properly. In Phase III of the project.
improvements are planned in electronic design, packaging.
control algorithms, and in the accompanying ground support
system. In addition, an extensive flight program will be
conducted to assure that all the design goals are met. and to
gain experience with this new atmospheric research tool.
111
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CONTENTS
Abstract iii
Figures vi
Acronyms vii
Acknowledgements viii
1. Introduction 1
2. Operational Prototype Design 4
a. Buoyancy Control Concept 4
b. Buoyancy Control Strategies 6
c. Balloon Envelope 8
d. Payload 12
e. Ground Support System 22
f. Inflation Shelter 22
3. Experimental Program 26
a. Balloon Envelope 26
b. Indoor System Tests 30
c. Free Flight Tests 30
4. Future Work 47
a. Required Changes 47
b. Improvements 49
c. Tests 53
5. Discussion and Conclusions 55
References 60
APPENDICES
A. Federal Aviation Regulations, Part 101 61
B. Summary of Relevant Equations from Phase I 66
C. Second Generation Balloon Design 70
D. Rate of Descent on Cutdown 74
E. Electric Match Safe Operating Procedure 80
F. Operational Prototype Schematic Diagrams 85
G. Control Program 96
H. Argos Data Frame 99
I. Determination of Balloon Volume vs Superpressure 100
J. Test Description Provided to the FAA 103
K. Launch Procedures and Checklists Ill
L. Data from Test Flights 115
v
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FIGURES
2-1 Buoyancy Control Principle 5
2-2 Phase I Testbed Prototype Balloon Tracer 9
2-3 Top Fitting and Cutdown Device 11
2-4 Block Diagram of Operational Prototype Payload .... 13
2-5 System Assembly Drawing 14
2-6 Buoyancy Adjustment Subsystem 15
2-7 Vertical Anemometer, Sensor Package, and Command
Receiver 17
2-8 Timer Cutdown. Interface, and Microcomputer Boards. 19
2-9 Argos Antenna 20
2-10 Main Payload Package, Side A 23
2-11 Main Payload Package. Side B 24
2-12 Ground Support System 25
2-13 Inflation and Launch Shelter 27
3-1 Strain vs Superpressure 31
3-2 Volume vs Superpressure 32
3-3 Indoor -Test of Operational Prototype 33
3-4 Map of Experimental Area 35
3-5 Launch Site 36
3-6 Balloon in Shelter after Weighoff 38
3-7 Tracer Moments After Launch 39
3-8 Recovery of Tracer from Flight 1 40
3-9 Data From Flight 1 41
3-10 Data From Flight 2 43
3-11 Inflated Balloon Being Returned 44
3-12 Data From Flight 3 45
3-13 Aerial Photo Mosaic Showing Flight History 46
4-1 New Payload Packaging and Deployment Concept 52
VI
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ACRONYMS
ADAS - Atmospheric Data Acquisition System
AGL - (Altitude) Above Ground Level
AIR - Atmospheric Instrumentation Research (Inc.)
ASCII - American (National) Standard Code for Information
Interchange
CVB - Constant Volume Balloon
DOE - U. S. Department of Energy
EPA - U. S. Environmental Protection Agency
FAA - Federal Aviation Administration
FAR - Federal Aviation Regulations
HF - High Frequency
MSL - (Above) Mean Sea Level
NCAR - National Center for Atmospheric Research
NOAA - National Oceanic and Atmospheric Administration
PC - Personal Computer
PLT - Physical Lagrangian Tracer
PROM - Programmable Read Only Memory
PTT - Platform Transmitter Terminal (Argos)
RAM - Random Access Memory
VII
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ACKNOWLEDGEMENTS
The authors would like to thank and to acknowledge the
contributions of the following individuals:
J. S. Irwin and R. G. Lamb of the U.S.E.P.A. for
their continued support, guidance, and encouragement.
E. Martin, C. Ready, and B. Newmark of Technadyne for
their assistance and cooperation in many ways.
G. Brown and S. Sawyer of Sandia Labs for assistance
in the field, and for invaluable assistance in
reporting, respectively.
E. J. Graeber of Sandia for suggesting a very clever
design for the cutdown device.
D. Call of Atmospheric Instrumentation Research for
the loan of prototype digital sondes for evaluation.
V. Lally and other members of the Global Atmospheric
Measurements Group at NCAR for their advice and moral
support.
Mr. and Mrs. S. Longo, owners of the land from which
the test flights were launched, for their warmth and
hospitality.
The Valley Improvement Association. Tierra Grande
Subdivision, and G. W. Burris for permission to use
the land in the Rio Communities over which they
exercise respective control.
A. Garde of the Valley Improvement Association for
permission to reproduce a map of the Rio Communities
area.
W. Halleck and F. Zaccaria of the Federal Aviation
Administration for their cooperation in facilitating
the flight test program.
This research was funded by the U.S. Environmental
Protection Agency in part through the National Acid
Precipitation Assessment Program.
Vlll
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1. INTRODUCTION
An Adjustable Buoyancy Balloon Tracer of Atmospheric Motion is a
physical Lagrangian tracer (PLT) — an airborne instrumentation
system that follows the flow of air in its vicinity, and that can be
tracked electronically. For decades, researchers have sought a
Lagrangian tracer to aid in understanding the dynamics of the
atmosphere, and more recently, to cast light on long-range air
pollution: acid deposition, regional haze and oxidant episodes, and
associated ecological effects. Advances in microelectronics,
satellite communications, and battery technology have now made such a
tracer system feasible. The present effort is primarily motivated by
the need to establish source-receptor relationships to distances of
order 1000 km, to evaluate the accuracies of air pollution transport
models, and to assess the inherent limits on the predictability of
source impacts at that distance. In a more basic sense, however, it
addresses a broad underlying need for a convenient means of following
atmospheric flows.
The need for a physical Lagrangian tracer has led to extensive
work with constant volume balloons (CVBs) which has been reviewed by
Tatom and King (1977) and by Zak (1983). CVBs follow the horizontal
motions of the volume of air in which they are embedded, but not the
vertical motions. Coupled with wind shear, this characteristic
limits their usefulness. In 12 hours, a CVB may become separated by
as much as 1300 km from the air mass in which it was initially
embedded (Danielson, 1961).
PLTs are necessarily balloon-borne systems, and consequently
must operate under Federal Aviation Regulations Part 101: Moored
Balloons, Kites, Unmanned Rockets, and Unmanned Free Balloons. The
purpose of this regulation is to strictly limit the hazard to air
navigation which such systems might otherwise represent. Part 101 so
For a detailed discussion of the meaning of the term
"Lagrangian" and of how the concept depends upon the spatial
scale of application, see Zak (1983).
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dominates the design of the Tracer that it is included here for
reference as Appendix A. Under this regulation, the U.S. weather
services, together with the weather services of other nations around
the world coordinated by the World Meteorological Organization,
routinely launch hundreds of radiosonde balloons twice daily.
Radiosondes measure the meteorological conditions aloft from the
surface to beyond 20,000 m above many major airports and certain
other selected sites.
It is an explicit design goal that the Tracer Balloon operate
under the exemption clauses of FAR 101, as do radiosondes. Under
these clauses, if a balloon system carries a payload which meets
certain conditions regarding weight, density, and strength of
suspension, the system is exempt from most of the other provisions of
the regulation. This is important principally because one of those
other provisions precludes operating non-exempt balloon systems in
clouds, or even in the vicinity of clouds. This provision would
severely limit the usefulness of a Tracer Balloon which was not
exempt.
Because safety is a major consideration, certain safety features
are incorporated in the Tracer Balloon design beyond those specified
by FAR 101. For instance, even though the Federal Aviation
Administration (FAA) does not require it, when the Tracer Balloon is
flown at altitudes available to other aircraft, it will carry an FAA
transponder. In this way, the FAA will see the Tracer on radar as
prominently as a commercial airliner, and can control air traffic
accordingly.
The intended uses also provide other Tracer Balloon design
goals:
Lifetime > 3 days.
Tracking range > 1000 km.
Telemetry of relative vertical air motion, pressure,
temperature, and humidity.
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Ground system capable of handling several Tracer
Balloons at a time.
Capable of establishing specified ascent and descent
rates under radio command.
Capable of reaching altitudes up to 5.5 km (500 mb).
Capable of following mean vertical flows as low as
1 cm/s with acceptable fidelity.
Sufficiently inexpensive to permit use in significant
numbers on an expendable basis.
As currently planned, the project is divided into four phases:
Phase I: Systems Design and Demonstration of
Feasibility.
Phase II: Development of an Operational Prototype.
Phase III: Tests and Refinement of the Operational
Prototype System.
Phase IV: Addition of Elements Necessary to Create a
Practical Research Tool.
Phase I was initiated in fall, 1983, and ran through calendar year
1984. The results were reported by Zak et al (1986). The Phase I
report gives the chain of reasoning and the experimental data which
led to the operational prototype design described in the following
section. Phase II spanned calendar year 1985. The results are
presented in this report. Phase III is scheduled to begin during
spring of 1986, and will extend into 1987. The timing and duration
of Phase IV will be determined by budgetary considerations, and the
needs of the National Acid Precipitation Assessment Program.
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2. OPERATIONAL PROTOTYPE DESIGN
a. Buoyancy Control Concept
Balloon systems obey Archimedes' Principle: A body immersed
in a fluid is buoyed up by a force equal to the weight of the fluid
displaced. This implies that a balloon system will be in equilibrium
when the weight of the air it displaces is equal to the weight of the
system.
Constant volume balloon systems have a unique characteristic.
The equilibrium condition is met only at one well-defined altitude,
and the CVB seeks that altitude. If it should find itself above the
equilibrium altitude, the CVB will experience a net downward force
due to gravity because the ambient air is less dense at the higher
altitude, and the volume of air displaced is fixed. Likewise, if it
should be below its equilibrium altitude, it will experience a net
upward force, since the buoyancy force exceeds the gravitational
force. Thus, CVBs tend to oscillate around their equilibrium
altitude, the oscillations driven by atmospheric turbulence. In
atmospheric flows which have zero average vertical velocity, CVBs
naturally follow the horizontal flow at their equilibrium altitude.
However, in flows in which the vertical component is significant, a
CVB will not adequately follow the overall flow.
The Tracer Balloon is a modified CVB. It is designed to sense
its deviation from the mean vertical flow, and to adjust its buoyancy
to keep its average vertical motion relative to the air surrounding
it near zero. Thus, the Tracer follows both horizontal and vertical
flows.
The buoyancy adjustment principle used in the Tracer was first
put forward by V. E. Lally of the National Center for Atmospheric
Research (NCAR) almost twenty years ago (Lally, 1967). He proposed a
CVB with an inner bladder, or ballonet, to contain the lift gas
(helium). The remainder of the CVB was to be filled with air (Figure
2-1). A system of pumps and valves was included to allow air to be
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Figure 2-1. Buoyancy Control Principle. The outer skin of the
balloon is made of a material which expands very little as the
internal pressure increases. A thin polyethylene inner balloon, or
"ballonet", keeps the helium lift gas separate from the air ballast.
A pump (P) permits more ballast air to be taken on. A valve (V)
permits ballast air to be vented. The total volume remains nearly
constant, so pumping or yalving changes the average density of the
system, and thus its altitude.
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pumped in or to be released, respectively increasing the mean density
of the balloon and thereby decreasing its equilibrium altitude, or
decreasing the mean density and thus increasing the equilibrium
altitude. Lally's concept was adopted for the Tracer Balloon.
Previously, it had been tried by the French on stratospheric balloons
with some success, but was not developed further (Blamont et al,
1974).
In Phase I, we examined the behavior in a standard atmosphere of
an adjustable buoyancy balloon of the type proposed by Lally. A
summary of the equations derived to describe its behavior is given in
Appendix B.
b. Buoyancy Control Strategies
For a workable Tracer, it is also necessary to in-
corporate a means of sensing deviation from the mean vertical air
flow. Two approaches are considered here. Both have advantages and
disadvantages. The first is to measure the vertical air velocity
relative to the Tracer Balloon, and to integrate that velocity with
time to obtain relative vertical displacement. The second is to take
advantage of the near-adiabatic nature of atmospheric flows, and to
use potential (or equivalent potential) temperature as the control
parameter.
The first approach is very direct. It yields the desired
information with few if any assumptions. On the other hand, it
places very stringent demands upon the vertical velocity measurement.,
If the measurement involves an average systematic bias of only 1 cm
per second consistently in the same direction, the control system
will create a relative vertical displacement which grows linearly
with time at the rate of 36 m/hour. On the other hand, if the same 1
cm/s error is entirely random, the total expected error in a 72 hour
flight may be less than 40 m (Zak et al, 1986) . since measurement
error is nearly always a mix of both random and systematic, the
details of the measurement, which determine the proportions of the
mix, are very important. Unacceptable bias may also be present under
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some meteorological conditions, but not others. For instance, in
rain, a propeller-type vertical anemometer would surely give a
grossly biased result.
Use of the near-adiabatic character of atmospheric flows poses
less of a measurement problem. In the absence of liquid water and of
diabatic heating or cooling, the potential temperature is conserved -
- that is, trajectories are isentropic (Holton, 1979). Potential
temperature is given by:
6 « T(1000/P)Ra/Cp (2-1)
Here T is the ambient temperature, P the ambient pressure, R the gas
Si
constant for unsaturated air, c the specific heat at constant
pressure for air, and Ra/c = .286. In a standard atmosphere, the
vertical gradient of potential temperature at sea level is 3.3 x 10~3
degrees Kelvin per metre. So, if one controls potential temperature
to plus or minus a tenth of a degree, the altitude would be
controlled to +31 m, quite adequate for our purposes.
However, diabatic effects do occur. In the region of interest
below 5.5 km, they are strongest near the surface, and decrease with
height above ground. Throughout most of the troposphere, diabatic
heating and cooling is of order one degree Kelvin per day (Wallace
and Hobbs, 1977). Depending upon meteorological conditions, this
change may be net heating, net cooling, or interim variation with no
net gain or loss. One would expect the diabatic effects to occur
primarily during convective mixing. In the absence of a means of
taking these effects into account, they would limit the accuracy with
which an isentropic Tracer Balloon would reflect air motion.
In the presence of liquid water, condensation and evaporation
occur with the result that potential temperature is no longer
conserved even if the flow is adiabatic. However, "equivalent
potential temperature" is conserved in wet processes (Holton, 1979;
Wallace and Hobbs, 1977). It could be used as the altitude control
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parameter in the presence of liquid water. The equivalent potential
temperature is given by:
0e * 6 exp (Lqs/cpT) (2-2)
where L is the latent heat of condensation, and q_ is the saturation
mixing ratio of water vapor in air at the ambient temperature and
pressure.
The operational prototype currently incorporates three control
algorithms selectable by radio command. The control parameters for
these algorithms are, respectively, relative vertical displacement,
potential temperature, and ambient pressure. In a stable (non-
convective) atmosphere, in the absence of liquid water, the potential
temperature control algorithm is most appropriate. In a stable but
saturated atmosphere, an algorithm yet to be written using equivalent
potential temperature would be most appropriate. In a convective
atmosphere, the gradient of the potential temperature with altitude
goes to zero. Hence, under convective conditions, potential
temperature is not a satisfactory control parameter. Rather,
relative vertical displacement becomes the control parameter of
choice. Under convective conditions, over reasonably flat terrain,
even the constant pressure control algorithm may be satisfactory.
The question of the most appropriate control strategy to adopt
under different meteorological conditions is quite complex. It was
discussed at some length in the Phase I report, especially in
Appendix J (Zak et al, 1986). It is an area that will continue to
receive attention in Phases III and IV. We will return to it in
Section 4.
c. Balloon Envelope
A second generation balloon envelope has been designed
(Appendix C). However, five first generation balloons remained after
the conclusion of Phase I (Figure 2-2). Consequently, as an economy
measure, first generation balloons were used in the operational
8
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Figure 2-2. Phase I Testbed Prototype Balloon Tracer. It
incorporated the same first generation balloon as did the operational
prototype flown during Phase II.
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prototype system. They were designed and fabricated to our
specifications by Raven Industries of Sioux Falls, South Dakota.
Their nominal characteristics are:
Shape: Sphere
Volume: 12.5 m
Diameter: 2.9 m
Material: 3.0 mil polyester (bilaminated)
Ballonet: 1.0 mil polyethylene
Weight: 4.4 kg
The inner polyethylene balloon/ or ballonet, is attached to the outer
polyester (mylar) balloon only at a helium fill fitting located at
the top. The bottom fitting is a 16.5 cm diameter external nylon
plate fastened with screws to a nylon ring inside the outer balloon.
The nylon plate was modified to accept two plastic fittings for air
lines, and electrical leads to accommodate a pressure sensor assembly
inside the balloon. The plate can be removed, leaving a 11.4 cm
aperture which provides access to the inside of the outer balloon.
In the testbed prototype constructed for Phase I, the top
fitting on the balloon was closed by a simple screw-on cap. In the
operational prototype, a mating fitting was added that incorporated a
pair of cutdown devices, and a helium fill line made of "layflat"
polyethylene tubing. The cutdown fitting, the attached helium fill
line, and an experimental version of the cutdown device is shown in
Figure 2-3. In the cutdown device, a polyethylene membrane stretched
across an aperture forms a seal for the helium. A pair of electric
matches are mounted in such a way that if either one is actuated, a
hole is burned in the membrane, and the helium is allowed to flow
out. This results in a controlled descent (Appendix D). The flame
from the electric match is totally contained within the cutdown
device. Nevertheless, a Safe Operating Procedure was required to
cover the use of electric matches in this way (Appendix E). The
portion of the device which holds the stretched membrane is adapted
10
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from an inexpensive, commercially-available liquid sample cell used
in spectroscopy laboratories.
d. Payload
The operational prototype payload consists of the following
elements:
- Buoyancy adjustment subsystem
Sensor subsystem
Microcomputer
Interfaces
Cutdown timer
Argos platform transmitter terminal
- Argos antenna
Radio command receiver
Command decoder
Command antenna
Backup cutdown package
Tracking aids
Batteries
Each of these elements is discussed below. A block diagram of the
payload is given in Figure 2-4. More detailed schematic diagrams of
individual circuit boards are included in Appendix F. An assembly
drawing of the operational prototype is given in Figure 2-5. Note
that the vertical anemometer and the sensor package are mounted at
opposite ends of a long styrofoam boom which allows the measurements
to be made at positions where the influence of the balloon itself is
negligible.
The buoyancy adjustment subsystem is shown in Figure 2-6. It
makes use of the same type of Gilian pumps used in the testbed
prototype, but here three pumps are used rather than two. This
increases the pumpdown speed obtainable by about fifty percent. The
actual pumpdown speed — the rate at which the equilibrium altitude
can be lowered — is determined both by the temperature lapse rate,
and by the pressure head against which the pumps must work, the
"superpressure." With thirty millibars superpressure, in a standard
atmosphere the calculated pumpdown speed with three pumps is about 15
cm/s. The relevant equations are included in Appendix B.
12
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14
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The same Klippard valves are used here as in the testbed
prototype. The actuator, however, has been modified. In the testbed
prototype, these mechanical valves were directly actuated by a servo.
In the operational prototype, the servo drives a cam, and the cam
actuates the valves. This arrangement has the advantage that the
servo only requires power while the cam is turning — while the state
of the valves is being changed. At other times, the servo draws no
current. This modification results in significant power savings.
The sensor subsystem consists of two elements. The first is an
aspirated sensor assembly which measures ambient pressure,
temperature, and humidity. It is a modified AIR Inc. prototype
digital radiosonde. The assembly outputs data in ASCII format. The
transmitter normally in place has been deleted, and the assembly has
been housed in a styrofoam package normally used for a tethersonde,
rather than a radiosonde. The tethersonde package makes provision
for aspiration. Aspiration is important in the Tracer Balloon
application because inadequate natural ventilation takes place.
The second element of the sensor subsystem is the vertical
anemometer. It makes use of a stock 22.9 cm (9 in) diameter expanded
styrofoam Gill propeller from R. M. Young Inc., and a slightly-
modified Spaulding Instruments Cl rotation sensor. The Spaulding
sensor is a photoelectric type which gives both rate and direction of
rotation. It is modified only in that dust seals normally present
were removed to minimize friction. An anemometer of this type was
originally designed for Sandia by MacCready (1981), It has a
starting speed under 2 cm/s, and a measurement threshold of under 3
cm/s. This starting speed and low velocity performance should allow
relative vertical velocity measurements averaged over minutes to be
made down to 1 cm/s or less. Even at very low intensities of
turbulence, the instantaneous relative vertical air velocities are
likely to be considerably higher than the average over a few minutes.
The sensor package and the vertical anemometer are shown in
Figure 2-7.
16
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The heart of the control system is an Intel 8052AH BASIC
microcomputer. It contains 4 K bytes of random access memory (RAM)
and 4 K bytes of programmable read only memory (PROM). The control
program is written in BASIC, and was entered into the microcomputer
from a terminal. After testing, it was transferred to PROM.
Thereafter, when the pay load was powered up, the program self-loaded
and ran. A listing of the control program used during the field
tests is given in Appendix G.
The Intel 8052AH requires a variety of interfaces to other
system elements. Those interfaces are combined on the same board
with an up-down counter which is part of the vertical anemometer.
The cutdown timer automatically actuates the cutdown device
after a preselected period. However, the timer can be reset to zero
by radio command. In normal operation, the timer reset command is
sent at frequent intervals. As long as those commands are received
at intervals not exceeding the preselected period, automatic cutdown,
is avoided. If, on the other hand, radio communication with the
Tracer is lost for a period exceeding that which has been
preselected, the Tracer is automatically removed from the sky. This
arrangement avoids the possibility of the Tracer becoming a derelict
in the event that radio communication is lost. Figure 2-8 shows the
cutdown timer, the interface board, and the microcomputer.
The Argos platform transmitter terminal (PTT) was made by
Telonics, of Mesa, Arizona. It is uniquely compatible with the
flight control microcomputer. It is controlled by ASCII input
commands. The first ASCII byte specifies the identification code of
the PTT and the way the data are to be processed for transmission.
The next 32 bytes are the data to be transmitted. Eight codes are
programmed into each PTT. The computer controls which code or codes
are used. The Argos data frame used here is given in Appendix H.
The Argos antenna is a high gain device designed originally at NCAR
for use on high altitude balloons (Figure 2-9). A detailed
description of the entire Argos satellite-based data collection and
18
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platform location system was included in the Phase I report as
Appendix H (Zak et al, 1986).
The radio command receiver is a unit designed and built for our
application by Hock Engineering of Boulder, Colorado. It operates on
13.8035 MHz, a frequency to which Sandia has access. It has a one
microvolt sensitivity. The receiver (packaged in styrofoam) is shown
in Figure 2-7. The command receiver antenna is a quarter wavelength
wire.
The commands are electronically encoded at the transmitter, and
decoded at the receiver. The encoder/decoder circuit pair are
commercially available components designed for use in television
remote control systems. Since they are mass produced, they are quite
inexpensive. The commands currently available are:
-Activate cutdown
-Reset cutdown timer
-Initiate control in pressure mode
-Initiate control in potential temperature mode
-Initiate control in relative vertical motion mode
-Increment current value of control parameter
-Decrement current value of control parameter
-Turn on pumps
The encoder/decoder pair is capable of incorporating many more
commands with minimal changes.
For the field tests, a backup command cutdown package was
mounted near the balloon top fitting. It made use of a model
aircraft radio control receiver to actuate one of the electric
matches on command independent of the cutdown timer and the main
command system.
21
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The tracking aids were not flown on the operational prototype
Tracer during the short flights conducted to date. Consultation with
the FAA suggested that for flights under 300 m above ground level
(AGL) in the test area, there was no need for them. They were
procured, nevertheless. The FAA transponder with encoding altimeter
is a unit made by Terra Corporation of Albuquerque. This unit
appears to be the lightest and lowest power drain unit on the market.
Two different lightweight strobe lights were obtained for nighttime
use. A decision has not yet been made as to which would be
preferable.
The batteries were lithium thionyl chloride units in AA, C, and
D cell sizes procured from Altus Inc. They are reported to have
excellent low temperature characteristics. This property will be
necessary in order to meet the 5.5 km (500 mb) altitude design goal.
At this altitude, low temperatures will be encountered. Preliminary
tests with the batteries have been conducted down to -18 C.
Each side of the main electronics package is shown in Figures
2-10 and 2-11, respectively.
e. Ground Support System
The ground support system for the operational prototype
tests is shown in Figure 2-12. It consists of a Handar Argos
downlink receiver and decoder, an HP85 PC, a command encoder, a Swan
command transmitter, and an antenna coupler mounted in a 5 m
Airstream trailer. The HP85 converts the Argos data stream from
hexadecimal to decimal form, formats it, and prints it out on its
integral thermal printer. It also archives the data on its integral
magnetic tape cassette recorder. An Argos antenna, and a vertical
command antenna were mounted on a crank-up tower on the trailer.
f. Inflation Shelter
Inflation of the Tracer Balloon in the field without
suitable shelter would be very difficult. Consequently, a modular
22
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SERVO AND
VALVE ASSEMBLY
VALVE/PUMP
SERVO CONTROLLER
GILIAN
PUMPS
COMMAND
DECODER
Figure 2-10. Main Payload Package, side A.
23
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ARGOS
PTT
DIGITAL INTERFACE
AND ANEMOMETER
UP/DOWN COUNTERS*^
INTEL 8052AH
BASIC
MICROCOMPUTER
INTERCONNECT
BOARD AND
BUFFERS
SPACE FOR
TIMER/CUTDOWN
BOARD
(Not in place)
Figure 2-11. Main Payload Package, Side B.
24
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•O
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inflation and launch shelter was designed and built (Figure 2-13).
It makes use of a specially-fabricated bed for a 2 1/2 ton truck.
The bed was built for balloon launch for an earlier DOE project. It
is 16' long, and has 4' sides constructed so that they fold down and
are supported level with the truck bed, forming a 16' by 16' square
area. A 12' x 12' x 12' prefabricated plywood shelter assembled from
reinforced panels was built to mount on the expanded truck bed. The
back surface of the shelter consists of two full-height hinged doors
for moving balloons in and out. The balloon fits comfortably inside
the 12 foot cube. For transport to and from a launch site, the
shelter is disassembled to its constituent panels, and carried on the
truck with the sides and tailgate in the normal upright position. Of
course, this shelter is only required when no other suitable indoor
space is available near the launch site.
3. Experimental Program
Testing and refinement of the operational prototype system were
assigned to Phase III in the project plan. However, it was felt that
at least a minimal test program was necessary as part of Phase II to
demonstrate that the operational prototype developed here was in fact
functional.
a. Balloon Envelope
Although the balloon system had been tested in Phase I,
thought had not been given to how best to fill, check out, and weigh
off the balloon system preparatory to launch. As long as only low
altitude flights were contemplated, the fill was non-critical.
However, if one desires to fill the balloon so that maximum altitude
can be attained, and so that day-night temperature cycling and dew
accumulation can be overcome, then the fill procedure becomes much
more critical.
The procedure we developed is based upon Appendix F of the Phase
I report. Knowing the volume of the balloon, the weight of the
26
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I
-------
balloon, the weight of the payload, and the desired superpressure at
liftoff, an equation presented there gives the "required lift." That
equation is replicated as B-13 in Appendix B. Helium is put into the
ballonet with the outer balloon slack until a digital scale indicates
that the required lift has been reached. The balloon is fastened to
a weight on the digital scale. As helium is put into the balloon,
the reading on the digital scale declines to a value equal to the
magnitude of the weight on the scale plus the weight of the balloon
itself minus the required lift.
Next, the outer balloon is inflated with air using an auxiliary
external pump until an external manometer indicates that the desired
superpressure has been reached. At this point, the digital scale
should indicate that the remaining lift is essentially equal to the
weight of the payload. If the payload were attached, the balloon
would be approximately neutrally buoyant. Unfortunately, the lift of
a constant volume balloon depends not only on the volume of the
balloon and the amount of helium it contains, but also on the
pressure and temperature of the ambient air. Hence, any changes in
ambient temperature or pressure which occur while the fill process is
taking place need to be accommodated by "fine tuning" to obtain the
desired final lift. This can be done in two ways: adjustment of the
amount of helium contained in the ballonet, or adjustment of the
amount of air contained in the outer balloon. To simultaneously
obtain specified values for both the lift and the superpressure
requires that both be adjusted. However, .it is felt that the initial
superpressure need only be accurate to within a few millibars.
Hence, fine tuning can be accomplished with air alone if desired.
The fill procedure outlined above was used in the field test program
and was found to be adequate.
Balloon checkout was accomplished by weighing off the balloon,
and recording the lift and the superpressure, as well as the ambient
pressure and temperature. Twenty four or more hours later, the same
parameters were measured again. In the absence of significant leaks,
the new values of superpressure and lift were related to the old by
the gas law and Archimedes' Principle.
28
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The first balloon to be inflated for the test program was found
to be defective. There was a serious leak between the inner ballonet
and the outer constant volume balloon. Within a matter of a few
hours, the helium which had been put into the ballonet had diffused
throughout the outer balloon, leaving the ballonet slack. The
decision was made to attempt repair. The ballonet was removed from
the outer balloon and filled with air. A hole about 2 cm in diameter
was found in the ballonet. It apparently was made when the ballonet
was inserted in the outer balloon during the manufacturing process.
The hole was patched with special balloon repair tape, and the
balloon reassembled. In the process of reassembly, silicone vacuum
grease and "liquid gasket" sealing material were added at selected
interfaces where the original design appeared to have inadequate
seals. The reassembled balloon was inflated and checked out
perfectly. No residual leaks could be detected.
Once it was established that the repaired balloon was good, the
relationship between superpressure and expansion of the outer balloon
skin was investigated. At the beginning of the experimental program,
'it was thought that, properly calibrated, a strain gauge mounted on
the skin of the balloon might provide an adequate measure of
superpressure. If this were true, it would simplify the payload. A
resistive strain gauge can be accommodated through a spare channel on
the AIR sensor package; another aneroid pressure sensor cannot.
The strain gauge tried was a spring-loaded linear potentiometer
with a range of 0-9.5 K ohms for a travel of about 1 cm. The gauge
was fastened to a flexible plastic fixture which in turn was fastened
to the skin of the inflated balloon. A 2 cm wide strip of mylar
about 50 cm long was connected to the pull rod of the strain gauge,
and the far end of the strip fastened to the skin of the balloon.
The strip and its attachment points were mounted in the center of a
gore, along a polar circumference. The linkage was adjusted so that
initially the resistance of the strain gauge was near the center of
its range when the superpressure was about 40 mb.
29
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The balloon superpressure was cycled a number of times up to 80
mb, and back to zero. Measurements were made using an external pump,
an external manometer, and a digital ohmmeter to read the strain
gauge. This was done with the balloon attached to a weight on the
digital scale. The scale readings were recorded as well. The
information obtained allows one not only to observe how strain varies
with superpressure, but how balloon volume does as well (Appendix I).
The results are shown in Figures 3-1 and 3-2. The hysteresis
exhibited by the strain gauge measurements is sufficiently severe
that the resistance of the strain gauge does not provide accurate
information on superpressure. Although it was not positively
confirmed, it appeared that the ambient temperature also enters into
the relationship between superpressure and strain.
After evaluating the data, a decision was made to abandon the
strain gauge, and to make direct measurements of the balloon
superpressure. This was done on the later flights using a standard
AIR radiosonde package mounted on the inside of the balloon bottom
fitting, and operated independent of the main payload.
b. Indoor System Tests
The Phase II plan called for the operational prototype
Tracer to be exercised first in the elevator shaft of the solar tower
at Sandia — the 7 m square by 52 m high chamber used to test the
Phase I system. Unfortunately, the solar tower was not available
when the operational prototype was completed. A new heat exchanger
system was being installed. Consequently, initial system tests were
performed in a hanger on Kirtland Air Force Base instead (Figure
3-3). The modest height of the hanger limited the tests to
confirming that the Tracer properly responded to radio commands to
change its equilibrium altitude.
c. Free Flight Tests
The site chosen for the initial flight testing of the
operational prototype Tracer was a large open area about 60 km south
30
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r-H
r-
'«H
10
20
30
40
50
80
Figure 3-1. Strain vs Super-pressure. Starting at zero
superpressure, the data marked by triangles were taken first,
followed by the data marked by Xs, and then that marked by diamonds,
Note that the strain gauge saturates at 9.5 K ohms.
31
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i
10
i
»
i
30
i
40
aoaO
TO
_
90
Figxare 3-2. Voltnae vs S\operpressvire for the Tracer Balloon. It is
clear from the data that the constant volume assumption is only a
rough approximation. Variation of volume with superpressure is a
major reason why passive "constant volume" balloons are not ideal
tracers.
32
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Figure 3-3. Indoor Test of Operational Prototype. The payload is
connected with a line to a weight on a digital scale on the floor
immediately below it.
33
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of Albuquerque known as the Rio Communities. Some years ago, a
number of developers subdivided this land, put in rudimentary roads,
and offered it for sale. With the exception of a few small
communities along the periphery, the land is still largely vacant.
It forms a reasonably flat area of roughly 350 square miles (900 Ion2)
laced with dirt roads. It slopes from the western edge which is near
the Rio Grande River, up to the base of the Manzano Mountains on the
east. Permission for use of the land for the tests was obtained from
the concerned land owners associations. A map of the area is given
in Figure 3-4.
Once the experimental site was chosen, other arrangements could
be made. Because the operational prototype Balloon Tracer was
designed to fall under the exemption clauses of FAR 101, no
coordination with the FAA was formally required. As a matter of good
practice, however, liaison was established with both the FAA
Albuquerque Approach Control, and with the FAA Albuquerque Air Route
Traffic Control Center (Appendix J). It was also learned that one
edge of the experimental area was routinely used by helicopters and
C130s from the 1550th Combat Crew Training Wing based at Kirtland.
Liaison was therefore established with the 1550th as well through its
commanding officer and its Training Management Center.
The launch site itself was located on land owned by Mr. and Mrs.
S. Longo, very near the center of the experimental area. The
inflation shelter was reassembled in place at the launch site. The
16' Airstream trailer containing the ground support system was parked
next to it (Figure 3-5).
Successful launch of the Tracer Balloon is a fairly complex
undertaking. Many actions must be taken in proper sequence. To
assure that those actions would in fact be properly taken, procedures
and checklists were developed (Appendix K).
On December 5, the weather criteria for a test flight of the
Tracer Balloon were met. Surface winds were extremely light. The
balloon itself had been inflated in the shelter and prepared for
34
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Add 4 miles to compute Albuquerque
distances via Interstate 25.
^"- ~i3 -—*_'--J ""i «^ "^ " ^ J.*-i 9 2";
Launch Site
Figure 3-4. Map of Experimental Area,
35
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o
•H
•P
(0
iH
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C
0)
flj
b
0)
•H •
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0)
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w
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36
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launch over the previous few days. On the morning of the flight,
final weigh off was done as part of the launch procedures
(Figure 3-6). The Tracer Balloon was launched at 10:41 am
(Figure 3-7). The pressure control algorithm was used for the entire
flight. The Tracer remained aloft for 2 hours and 20 minutes, and
was recovered about 4 miles from the launch site (Figure 3-8). The
control algorithm functioned properly. The most relevant data are
given in graphical form in Figure 3-9.
After removal of the payload, an attempt was made to return the
balloon fully inflated to the launch site by fastening it to the bed
of the four-wheel-drive pickup used as a chase vehicle. Even though
all five attachment points on the balloon were used, this attempt
failed. The balloon got away when the pickup had gone only a few
tens of metres. The terrain in the landing area was quite rough.
The very rough ride put large stresses on the load patches at the
attachment points on the balloon. All five load patches tore off,
freeing the balloon. The balloon without payload rose rapidly to an
estimated altitude of 1500 m AGL at which it burst. The estimated
superpressure at burst was between 150 and 200 mb, about double the
maximum operational superpressure of 80 mb. After it burst, the
balloon envelope was visually tracked as it came down. The top
fitting and the cutdown device which had been left attached were
recovered intact from the remains of the balloon envelope about three
miles from the point at which the balloon escaped.
The loss of the balloon envelope was not considered a major
setback. In project planning, the assumption had been made that the
balloon envelope would not be recovered intact in normal use. It now
appears that if the balloon is deflated upon recovery, the balloon is
likely to be reuseable.
A new balloon was inflated and prepared for use on the next test
flight. This time, no leaks were found. The payload was also
modified to accomodate the superpressure measurement, and to overcome
a flaw which had been found in the way sensor data was entered into
the microcomputer. On December 16, weather conditions were again
37
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-------
Figure 3-7. Tracer Moments After Launch.
39
-------
I
I
o
-------
no-
o. MO
1 •»
UM hi control prMvar*
n\tUn tmiiimlmir Motion
pump- -i-l
valve--I
M
•10
•no
•840
•OBO
•30
10
1000
time - hrs
Figure 3-9. Data From Flight 1. Control parameter was pressure.
The Tracer was launched with positive buoyancy. In the top graph,
note that it overshot the control pressure level, and then pumped
itself back down to it. Note also that the landing site was
significantly higher than the launch site.
41
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suitable for test flights. The first launch took place at 7:38 am.
Shortly after launch, the system was put into the constant potential
temperature control mode by radio command. As soon as the Tracer
climbed above the surface inversion, it was entrained in the
surviving elevated nocturnal jet and took off to the southeast at
high speed towards rising terrain. The flight was terminated by the
cutdown timer at about 0.4 hrs elapsed time when difficulty was
experienced in getting the timer reset command to the payload from
the ground station. The relevant data are given in graphical form in
Figure 3-10. Here the data record ends before flight termination.
Because the second flight was short and was terminated early in
the day, the decision was made to conduct another flight as soon as
preparations could be completed. This time, using a different
method, the fully-inflated balloon was successfully returned to the
launch point (Figure 3-11). The defect noted in the command system
was investigated, but in the time available, could not be diagnosed
and cured. Hence, it was decided to conduct a final flight with the
intent of allowing the cutdown timer to terminate the flight at 30
minutes after launch. This flight duration was chosen to assure that
the Tracer Balloon would not be carried by the winds beyond the
limits of the testing area. This was necessary to avoid the Tracer
being carried either into mountainous or otherwise inaccessible
terrain.
At 3:34 pm, the third flight was launched. After climbout, the
tracer was put under the control of the zero-relative motion control
algorithm by radio command. It too functioned properly. The winds
were quite light, so the balloon traveled' only a few miles during the
half hour flight. The cutdown timer terminated the flight as
planned. For the third time, the Tracer was brought down with no
damage to either the balloon or the payload. The data from the third
flight are given in Figure 3-12.
Tabular data from all three flights are given in Appendix L. An
aerial photo mosaic of the test area showing the launch point and all
three landing points is given in Figure 3-13.
42
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cu
1
10
•H
-too
«••
f 40-
UM i* omtrol potential tamp.
pump- -cl
1-
0- i • » «
-i-
UO (Ufl 020 0X8
alanrad time - hr»
0.*> OJtt
•MO
'870
B80
•10
—10
100
M
0
—40
-100
•z
•I
•0
-t
46
40
30
040
Figure 3-10. Data From Flight 2. Control parameter after launch was
potential temperature. The data record ends before the final
descent.
43
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Figure 3-11. Inflated Balloon Being Returned after Flight 2,
44
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•80
1-
Us* l> control prwnurv
upp«r Ua» l« potential temp.
dMh«d ]lam 1* control value
nUUr* v«rtieal
pump- -t-1
valve= -1
0.0 0.1 0.2 0.3 0.4 OS
eiaosed time - hrs
o.e
0.7
830
040
BOO
MO
25
SO
15
to
•6
200
0
-200
-400
-600
-600
-1000
-2
40
30
SO
10
aa
Figure 3-12. Data From Flight 3. Control parameter after launch was
relative vertical motion.
45
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Figure 3-13.
launch site;
Aerial Photo Mosaic Showing Flight History.
L1-L3 are the respective landing sites.
LS is the
46
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4. Future Work
a. Required Changes
Certain changes are required to eliminate flaws in the
operational prototype Tracer system which were discovered during the
experimental program.
In the first flight, the temperature data showed discontinuities
of several degrees that clearly could not reflect reality. While at
first the temperature sensor was suspected, the problem was
ultimately traced to the input port of the 8052AH BASIC
microcomputer. The port through which the sensor data are input is
normally used as a keyboard input. It was discovered that the 8052
automatically converts bytes coming into this port corresponding to
lower case ASCII letters to bytes corresponding to upper case ASCII
letters. Nowhere in the literature supplied with the 8052 is this
mentioned, but the fact was established unambiguously by laboratory
test. Since this port was used here to handle digital data rather
than keyboard alphanumeric data, this conversion is unacceptable.
When the data falls in certain ranges, it results in an offset of the
data received by the 8052 from that sent to it. Note that the
temperature data in Figure 3-9 has been appropriately corrected. The
anomaly did not affect the buoyancy control of the Tracer because the
pressure control algorithm was used on flight 1, and by chance, the
ambient pressure did not fall into an affected range. A temporary
fix was implemented for flights 2 and 3 by biasing sensor outputs so
that the data were not affected, and by removing the bias
subsequently in the onboard software. This works satisfactorily only
when the data fall into relatively narrow and predictable ranges as
was the case for the recent field tests. In Phase III, however, the
problem must be eliminated. Intel now makes a version of the 8052
which is not subject to this anomaly.
Mention was made earlier of the fact that a strain gauge mounted
on the skin of the balloon did not give an adequate measure of
balloon superpressure. While the strain gauge sensor was operative
47
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on flight l, it was replaced with an independent AIR airsonde package
for flights 2 and 3. This expedient was acceptable only because the
test flights were short, and the Tracer Balloon remained in line of
sight of the ground station. The independent telemetry from the 403
MHz sonde could thus be received. In Phase III, it will be necessary
to replace the independent sonde inside the balloon with another AIR
digital sonde similar to the one on which the sensor package is
based. The output from this second digital sonde will then be input
to the 8052 microcomputer, and the relevant data on conditions inside
the balloon incorporated into the Argos data stream. It will then be
recoverable either directly with an Argos downlink receiver, or
through the satellite link.
Mention was also made of a problem with the radio command
system. While it checked out perfectly in the laboratory, it was
found to have a much shorter effective range than anticipated — of
the order of a few miles, rather than a few thousand miles. The
first thought was that the command receiver on the Tracer payload
might have inadequate sensitivity, but subsequent laboratory tests
established that the command receivers have excellent sensitivity.
It now appears that the fault lay not with the operational prototype
Tracer payload at all, but with the ground station. A single
sideband transmitter which was on hand from another project was
modified for use as the command transmitter. The modification
converted it from single sideband to frequency modulation. The
command transmitter appears to be distorting the encoded command
waveform. It is speculated that as long as the command signal
saturates the command receiver, the distortion is effectively
suppressed by the receiver. At greater distances, however, the
receiver is not saturated, and the command decoder does not recognise
the distorted commands. If the fault does lie in the command
transmitter as now suspected, the most cost-effective fix will be to
purchase more suitable command transmitters in Phase III. They are
estimated to cost <$1000 each.
48
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b. Improvements
We begin considering the improvements needed with the balloon
envelope. Major improvements were already incorporated into the
design of the second generation balloon (Appendix C). During Phase
III, a number of such balloons will be procured and used for the
latter part of the Phase III test program. The earlier tests will
still be conducted using first generation balloons since there are
four such balloons remaining.
One of the needed improvements not included in the second
generation balloon design concerns the cutdown device. The current
device functions well, but it is extremely difficult to mount the
electric matches. A more convenient design will be developed.
For flights which may encounter high relative humidity or rain,
it will also be necessary to treat the skin of the balloon to
minimize water adhesion, tally's group at NCAR has identified a
number of surface treatments which appear to work. Prior to applying
a given treatment, a laboratory study will be done to determine which
candidate treatment works best.
Finally, the poor visibility of the balloon envelope itself is
of concern from an air safety point of view. Bright orange
or red banners of appropriate material will be attached to the
balloon at the proposed location of the drip skirt on the second
generation balloon.
The chief improvement needed in the electronics design beyond
eliminating the data transfer glitch is to increase the amount of
memory available to the microcomputer. The present system has 4 K
bytes of both RAM and PROM. The entire program is limited to about
200 lines of BASIC code. With this constraint, it was not even
possible to calculate relative humidity from the sensor data. That
calculation had to be sacrificed to stay within the overall memory
capacity. Even so, the current control algorithms are quite simple.
They check to see if the control parameter falls within a predefined
49
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band centered on the selected value. If it does, nothing is done. If
it doesn't, the pump or valve is actuated as appropriate for a fixed
time — one Argos cycle, approximately 42 seconds. At the beginning
of the next cycle, another check is performed, and so on.
With the current control program, the control algorithm to be
used must be selected by radio command. In the improved control
program made possible by more memory, the system itself will choose
the appropriate control algorithm depending upon the meteorological
environment of the Tracer. We plan to quadruple the memory to 16 K
bytes of RAM and PROM. The cost in dollars, weight and power
consumption are all quite small. This will permit each control
algorithm to be more sophisticated, will permit self-selection of the
appropriate control algorithm, and will accommodate additional
control algorithms as well.
The command system needs certain improvements as well as
debugging. The 13.8035 MHz frequency is available to Sandia in the
Albuquerque vicinity, and in selected other areas around the country.
It is not, however, available nationwide. Launch would be very
complicated if instead of the command transmitter being in the field,
it were located in Albuquerque. What is needed is another command
frequency which is available nationwide, and which has similar long
range radio propagation characteristics. We propose to modify the
receivers so that they listen for commands on both frequencies
simultaneously. The command system will also be modified to
accommodate more commands, including "initiate control in equivalent
potential temperature mode," and "suspend control."
The Terra Corporation FAA transponder currently uses about 5
watts of power continuously. This power consumption should be
brought down. One of the major power consumers in the transponder is
a heater circuit in the encoding altimeter. The heater power
consumption can be decreased by providing better insulation for the
pressure sensor. Elimination of panel lights, and other similar
modifications will also be implemented.
50
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An entirely new element should be added to the payload. It is a
radio beacon of the type used for animal tracking. Such beacons are
extremely light in weight, and use very little power. If each Tracer
Balloon were equipped with such a beacon, recovery of the payload
would be greatly facilitated, even if the recovery operation were not
mounted until days after the Tracer Balloon had come down. In light
of the limited resources available to this project, it is imperative
that payloads be recovered after each test flight. In Phase II,
recovery posed no problem because the flights were short. In Phase
III, flights hundreds of kilometres long may be undertaken. The
recovery problem will be greatly exacerbated unless beacons are
included. Argos data will indicate where a payload is to within a
kilometre or two. The beacon will allow the recovery crew to
pinpoint it.
Finally, payload packaging is an area where major improvements
can and should be made. A new design concept for packaging and
deploying the payload is shown in Figure 4-1. Here, the vertical
anemometer and the sensor package are no longer mounted on a
styrofoam boom. Rather, they are mounted on much smaller rods
attached to the balloon skin at the equator. The balloon itself is
used as a structural element to facilitate getting the sensors at
least 50 cm out beyond the balloon equator. In addition, with the
exception of the transponder and the strobe, the other payload
packages are attached to the skin of the balloon with Velcro. Here
too, the balloon skin becomes a structural element. The net effect
of the proposed changes is to markedly simplify the deployment of the
payload. This in turn will simplify the launch procedure, and
minimize the probability of the Tracer Balloon getting snared by
trees or power lines.
With regard to the ground support system, certain improvements
should also be made. Of course, the command transmitter must be able
to accommodate both command frequencies now seen to be necessary. In
addition, the HP85 computer needs to be replaced with a more powerful
PC, one that can log data on a hard or floppy disk, and that can talk
to a central computer system through a modem. The PC will also be
51
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Figure 4-1. New Payload Packaging and Deployment Concept. System
Elements: A. Vertical Anemometer; B. Argos Antenna; C. Sensor
Package; D. Buoyancy Control Subsystem; E. Main Electronics Package;
F. Batteries and Beacon Transmitter; G. Command Receiver and Cutdown
Package; H. Drip Skirt; I. FAA Transponder and Strobe Light.
52
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directly coupled to the command encoder and command transmitter so
that the cutdown timer reset commands can be sent automatically.
In addition to improvements in the ground support system, a
second independent station will be built for location at another
site. This is to assure, insofar as possible, that radio command
contact be maintained with the Tracer Balloon.
c. Tests
The goal of the test program is to check every significant
aspect of the performance of the Tracer Balloon system. Tests will
either confirm proper performance, or reveal flaws which, once
identified, will be remedied. While resources may limit how thorough
the test program can be, it is nevertheless important to keep this
goal in mind. There are three categories of tests which can be used
to achieve this goal:
Laboratory tests
Solar tower tests
Free flight tests
Benchtop laboratory tests are used to confirm proper function
of individual components and subsystems under the ambient conditions
found in the laboratory. Such tests are the first step. If a system
element doesn't function properly in the lab, it is highly unlikely
to perform properly in the field. Next, environmental chamber tests
are required to resolve questions regarding whether the sensors and
the payload as a whole function properly over the whole range of
interest of temperature, pressure, and relative humidity. In free
flight tests, questions regarding the accuracy of the data returned
from the Tracer cannot be adequately resolved because the atmosphere
is an uncontrolled environment, and we have no independent check on
the data. Consequently, a program of chamber tests will be
undertaken in Phase III.
53
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There are seme tests, specifically those bearing on the
performance of the vertical anemometer, which cannot easily be
addressed in either laboratory chambers or in free flight. To answer
these questions, the solar tower is ideal. The operational prototype
tracer system or a selected part thereof may be run up and down in
the relatively quiescent air of the tower. The integrated relative
vertical air motion data obtained from the vertical anemometer can
then be compared with the vertical position versus time record
obtained with a laser distance measuring device. If the air in the
tower has negligible vertical motion, the two sets of data should be
compatible. Provided that the solar tower is available in an
appropriate time frame, the required tests of vertical anemometer
performance will be done in Phase III.
Finally, we come to free flight tests. While these offer the
most dramatic evidence of proper function, they are also the most
expensive. Consequently, flight testing will be carefully planned to
get the most out of the experiments within the budgetary constraints.
The aspect of the system to be addressed in the flight tests is the
performance of the buoyancy control program under several different
meteorological and other environmental conditions: stratified
atmosphere, well-mixed atmosphere, convective activity, obstructing
terrain, low altitude, high altitude, cloud, rain, day, night, and
transition periods. In Phase III, the control program will consist
of several control algorithms, and software determining the automatic
onboard selection of the algorithm to be used on the basis of the
sensor data. The Phase III flight program will consist of a
graduated series of short (<10 km), intermediate (<100 km), and long
(>100 km) flights, launched most probably from the Phase II test site
south of Albuquerque.
Phase IV testing will be limited to answering the questions
which have not been adequately addressed in Phase III, and to
checking the performance of those elements added to the system in
Phase IV to make the Tracer Balloon a practical research tool.
54
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5. Discussion and Conclusions
The stated design goals for the Adjustable Buoyancy Balloon
Tracer form a useful frame of reference for evaluating the current
status of the effort.
Operates under the exemption clauses of FAR 101.
FAR 101 permits up to 12 Ibs (5.45 kg) of payload, as long as the
payload is distributed in packages weighing no more than 6 Ibs
2 2
(2.73 kg) each, which meet a 3 oz/in (13.2 g/cm ) areal density
limit, and which are connected by a "rope or other device for
suspension" that requires a force of no more than 50 Ibs to part.
The weight of the operational prototype Tracer payload as flown was
4.72 kg, well under the 5.45 kg limit. The Phase III operational
prototype mechanical design is expected to be about a kilogram
lighter. The operational prototype payload met the other exemption
conditions of FAR 101 as well.
Lifetime > 3 days
Available battery power determines the Tracer effective lifetime.
The major power drain on the Tracer was the set of three Gilian
pumps. At 45 mb superpressure, the pumps consume about 1 watt each.
If one assumes that they would be on about 1/3 of the time, in a 72
hr flight, they would require 72 watt hours of energy. During the
test flights, the pumps were on a greater fraction of the time
because the "dead zones" (where no action is taken) in the control
algorithms were intentionally made very small. The power for the
pumps is supplied by lithium batteries with an energy density of 0.43
watt-hours/g (195 watt-hours/lb). Two D cells in series (to get the
required voltage) can supply approximately 100 watt-hours of energy,
more than enough for the pumps. The D cells weigh 117 g each.
The main electronics package including the sensors requires
about 1.4 watts continuously. Over 72 hours, the need is for 100
watt-hours of energy. Again, 2 D cells will fulfill that need. The
55
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battery complement is completed by 3 C cells for the Argos PTT and 2
AA cells for the cutdown device. Because of the low duty cycle, the
Argos PTT has a low energy requirement. The cutdown device fires
just once, independent of the length of flight. The C cells weigh 58
g, and the AA cells, 21 g each. Thus, for a 72 hour flight, the
battery complement for the operational prototype as flown would weigh
684 g. That is just 118 g more than the battery complement included
in the Tracer for the Phase II test program.
Accommodating the FAA transponder is another matter. Although
it is not required by FAR 101, it is highly desirable that it be
carried on any flights above 300 m AGL. It weighs about 800 g
including the encoding altimeter, and draws about 5 watts average
power. If the transponder were unmodified, it would require 8 D
cells weighing a total of 936 g to operate continuously for 72 hours.
If the weight savings in the Phase III mechanical design slightly
exceeded the anticipated 1 kg, the FAA transponder and its battery
complement could just be accommodated within the 5'. 45 kg total
payload limit. However, it appears that the minor modifications
described earlier could halve the power drain,, reducing the weight of
the batteries to 468 g. If those modifications are made, there
should not be a problem in accommodating the transponder, and even
the strobe light with its battery complement (estimated weight,
250 g) on a 3 day flight.
Tracking range > 1000 km
Argos tracks world wide.
Telemetry of relative vertical air motion, pressure,
temperature, and humidity.
The Argos PTT easily accommodates these variables and can accommodate.
several others if desired.
56
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Ground system capable of handling several Tracers at a
time.
Argos can handle 200 PTTs in its field of view at a time. The
existing command system can accommodate different codes to address
each of several Tracers. If a 2 site, 2 frequency HF command system
is established as planned, command communication should be reliable
over more than 1000 km.
Capable of establishing specified ascent and descent rates
under radio command.
With appropriate additional commands implemented, the equilibrium
altitude could be modified over a broad range of rates.
Capable of reaching altitudes up to 5.5 km (500 mb).
With an appropriately-sized second generation balloon, the balloon
should pose no problem. If any problem exists, it is likely to be
the inability of some component to operate at the low temperatures
encountered at that altitude (20-25 degrees below zero Celsius). The
pumps and the batteries have been operated in a freezer at -18 C,
but the entire payload must be checked in an environmental chamber.
Should some existing component fail the test, a substitute with
better low temperature performance will be found.
Capable of following mean vertical flows as low as 1 cm/s
with "acceptable" fidelity.
An experimental test would involve comparison of the trajectory of
the Tracer Balloon with that of a gaseous or fine particle tracer
released in its vicinity. There is good reason to believe that this
specification would be met based on the arguments presented in the
Phase I report, and the performance observed to date.
57
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Sufficiently inexpensive to permit use in significant
numbers on an expendable basis.
This goal is inexact. We choose to address it as in Phase I by
considering the likely cost of the elements of an operational Tracer
procured in small numbers (<10) , and in large (>50) .
Cost Elements Cost Each f$K)*
>50
CVB with Ballonet 1.5 1.0
Buoyancy Adjustment Subsystem 0.5 0.3
Sensors 0.6 0.4
Microcomputer 0.2 0.2
Argos PIT 1.5 1.0
Command Receiver and Decoder 0.5 0.3
FAA Transponder and Strobe 1.0 0.8
Batteries 0.2 0.2
Miscellaneous Hardware 0.2 0.2
Assembly Labor 1.0 0.5
TOTAL 7.2 4.9
*CY86 Dollars
These cost estimates reflect the actual experience in building
the operational prototype Tracer. They are a bit lower than the
estimates made in the Phase I report, in spite of the fact that these
numbers are given in CY86 dollars, and the Phase I estimates were
given in CY84 dollars. The costs in quantity are approximate, and
merely project typical quantity procurement savings.
In field experiments, it is reasonable to expect a 50% return
rate of the payloads if they carry a message offering a reward and
giving a return address. The balloon envelope itself would not
likely be recovered. With these assumptions, in quantity, the
Tracers would cost approximately $3.0 K per use.
58
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On the other hand, the payloads are of sufficiently high value
that it would be economically attractive to actively seek to recover
them. Incorporation of a radio beacon of the type used to track
animals would make successful recovery highly likely, and would only
add $0.2 K to the cost of the payload. On the assumption that it
would take a two man crew a day to find each, the cost of recovery
per payload would be about $500. A recovery effort would reduce the
cost per Tracer use to $1.5-2.0 K. Some fraction of the time, the
balloon envelope itself would also be recovered in reuseable
condition. This would further reduce the cost per use.
Either with or without a recovery effort, the cost of a field
program using Tracer Balloons would likely be dominated by the cost
of maintaining a launch crew in the field, not by the cost of the
Tracers.
At the end of the Phase I report, the authors concluded that an
Adjustable Buoyancy Tracer Balloon meeting the design goals is both
technically and economically feasible. Phase II has confirmed that
conclusion.
59
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REFERENCES
Blament, J., Heinsheimer, T., and Pommereau, J. (1974). "New Method of
Study of the Dynamics of the Stratosphere - Principle and First Results,"
Acadetnie des Sciences (Paris). Contptes Rendus (B) 228. 249.
Danielson, E.F. (1961). "Trajectories: Isobaric, Isentropic, and Actual,"
J. Meteor. 18, 479.
Holton, J.R. (1979). An Introduction to Dynamic Meteorology. Second
Edition, Academic Press, New York, NY.
Lally, V.E. (1967). Superpressure Balloons for Horizontal Soundings of
the Atmosphere. National Center for Atmospheric Research Technical Note
NCAR-TN-28, Boulder, CO.
MacCready, P.B. (1981). "Turbulence and the Local Flow Field. The AV
Experiment on DaVinci I, in Final Report on Project DaVinci: A Study of
Long Range Air Pollution Using A Balloon-Borne Lagran&ian Measurement
Platform. Vol. 2: Reports of Participants in DaVinci I. B.D. Zak Ed.,
Sandia National Laboratories Report SAND78-0403/2, Albuquerque, NM.
Morris, A.L. (1975). Scientific Ballooning Handbook. National Center for
Atmospheric Research Technical Note NCAR-TN/1A-99, Boulder, CO.
Tatom, F.B. and King, R.L. (1977). Constant Volume Balloon Capabilities
for Aeronautical Research. NASA Contractor Report NASA CR-2805,
Huntsville, AL.
Wallace J.M. and Hobbs, P.V. (1977). Atmospheric Science, an
Introductory Survey. Academic Press, New York, NY.
Zak, B.D. (1983). "Lagrangian Studies of Atmospheric Pollutant
Transformations," in Trace Atmospheric Constituents: Properties.
Transformations, and Fates. Volume 12 in series. Advances in Environmental
Science and Technology. S.E. Schwartz, Ed., John Wiley and Sons, New
York, NY.
Zak, B.D., Church, H.W., Jensen, A.L., Gay, G.T., and Ivey, M.D. (1986).
Development of an Adjustable Buoyancy Balloon Tracer of Atmospheric
Motion. Phase I: Systems Design and Demonstration of Feasibility. U.S.
Environmental Protection Agency Report PB85-185817/AS; Sandia National
Laboratories Report SAND 85-0288.
60
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APPENDIX A
FEDERAL AVIATION REGULATIONS PART 101:
MOORED BALLOONS. KITES, UNMANNED ROCKETS.
AND UNMANNED FREE BALLOONS
The following is a reprint of the FAA regulation
most relevant to the adjustable buoyancy balloon.
61
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Part 101—Moored Balloons, Kites, Unmanned Rockets,
and Unmanned Free Balloons
Subpart A—General
f 101.1 Applicability.
(a) This Part prescribes rules governing
the operation, in the United States, of the
following:
(1) Except as provided for in § 101.7 of
this Part, any balloon that is moored to the
surface of the earth or an object thereon
and that has a diameter of more than 6
feet or a gas capacity of more than 115
cubic feet.
(2) Ezcept as provided for in § 101.7 of
this Part, any kite that weighs more than
5 pounds and is intended to be flown at
the end of a rope or cable.
(3) Any unmanned rocket except—
(i) Aerial firework displays; and
(ii) Model rockets—
(a) Using not more than 4 ounces
of propellant;
(&) Using a slow-burning propellant;
(c) Made of paper, wood, or break-
able plastic, containing no substantial
metal parts and weighing not more than
16 ounces, including the propellant; and
(d) Operated in a manner that does
not create a hazard to persons, property,
or other aircraft.
(4) Except as provided for in § 101J of
this Part, any unmanned free balloon that—
(i) Carries a pay load package that
weighs more than four pounds and has a
weight/size ratio of more than three ounces
per square inch on any surface of the
package, determined by dividing the total
weight :n ounces of the payload package
by the area in square inches of its smallest
surface;
(ii) Carries a payload package that
weighs more than 6 pounds;
Ch. J (Amdt. 101-4, tit. 1/20/74)
(iii) Carries a payload, of two or more
packages, that weighs more than 12
pounds •' or
(iv) Uses a rope or other device for
suspension of the payload that requires
an impact force of more than 50 pounds to
separate the suspended payload from the
balloon.
(b) For the purposes of this Part, a
"gyroglider" attached to a vehicle on the sur-
face of the earth is considered to be a kite.
1101.3 Waivers.
No person may conduct operations that re-
quire a deviation from this Part except under
a certificate of waiver issued by the Adminis-
trator.
1101.5 Operations in prohibited or restricted
areas.
No person may operate a moored balloon,
kite, unmanned rocket, or unmanned free bal-
loon in a prohibited or restricted area unless
he has permission from the using or controlling
agency, as appropriate.
[8 101.7 Hazardous operations.
[(a) No person may operate any moored
balloon, kite, unmanned rocket, or unmanned
free balloon in a manner that creates a hazard
to other persons, or their property.
[(b) No person operating any moored bal-
loon, kite, unmanned rocket, or unmanned free
balloon may allow an object to be dropped
therefrom, if such action creates a hazard to
other persons or their property.]
Subpart B—Moored Balfoons and Kites
i 101.11 Applicability.
This subpart applies to the operation of
moored balloons and kites. However, a person
62
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operating a moored balloon or kite within a
restricted area must comply only with §101.19
and with additional limitations imposed by the
using or controlling agency, as appropriate.
1101.13 Operating limitations.
(a) Except as provided in paragraph (b) of
this section, no person may operate a moored
balloon or kite—
(1) Less than 500 feet from the base of
any cloud;
(2) More than 500 feet above the surface
of the earth;
(3) From an area where the ground
visibility is less than three miles; or
(4) Within five miles of the boundary of
any airport.
(b) Paragraph (a) of this section does not
apply to the operation of a balloon or kite
below the top of any structure and within 250
feet of it, if that shielded operation does not
obscure any lighting on the structure.
i 101.15 Notice requirements.
No person may operate an unshielded moored
balloon or kite more than 150 feet above the
surface of the earth unless, at least 24 hours
before beginning the operation, he gives the
following information to the FAA ATC
facility that is nearest to the place of intended
operation:
(a) The names and addresses of the
owners and operators.
(b) The size of the balloon or the size and
weight of the kite.
(c) The location of the operation.
(d) The height above the surface of the
earth at which the balloon or kite is to be
operated.
(e) The date, time, and duration of the
operation.
1101.17 lighting and marking requirements.
(a) No person may operate a moored bal-
loon or kite [between sunset and s\mrise] un-
less the balloon or kite, and its mooring lines,
are lighted so as to give a visual warning equal
to that required for obstructions to air navi-
gation in the FAA publication "Obstruction
Marking and Lighting".
(b) Xo person may operate a moored bal-
loon or kite [between sunrise and sunset] un-
less its mooring lines have colored pennants or
streamers attached at not more than 50-foot
intervals beginning at 150 feet above the sur-
face of the earth and visible for at least one
mile.
1101.19 Rapid deflation device.
No person may operate a moored balloon
unless it has a device that will automatically
and rapidly deflate the bflloon if it escapes
from its moorings. If the device does not
function properly, the operator shall im-
mediately notify the nearest ATC facility of
the location and time of the escape and the
estimated flight path of the balloon.
Subpart C—Unmanned Rockets
f 101.21 Applicability.
This subpart applies to the operation of un-
manned rockets. However, a person operating
an unmanned rocket within a restricted area
must comply only with subparagraph 101.23
(g) and with additional limitations imposed
by the using or controlling agency, as appro-
priate.
f 101.23 Operating limitations.
No person may operate an unmanned
rocket—
(a) In a manner that creates a collision
hazard with other aircraft;
(b) In controlled airspace;
(c) Within five miles of the boundary of
any airport;
(d) At any altitude where clouds or ob-
scuring phenomena of more than five-tenths
coverage prevails;
(e) At any altitude where the horizontal
visibility is less than five miles;
(f) Into any cloud;
(g) Within 1,500 feet of any person or
property that is not associated with the op-
erations; or
(h) [Between sunset and sunrise.]
1101.25 Notice requirements.
No person may operate an unmanned rocket
unless, within 24 to 48 hours before beginning
the operation, he gives the following informa-
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PART 101 MOORED BALLOONS. KITES. UNMANNED BOCKETS, AND UNMANNED FREE BALLOONS
tion to the FAA ATC facility that is nearest
to the place of intended operation:
(a) The names and addresses of the
operators.
(b) The number of rockets to be operated.
(c) The size and weight of each rocket.
(d) The maximum altitude to which each
rocket will be operated.
(e) The location of the operation.
(f) The date, time, and duration of the
operation.
(g) Any other pertinent information
requested by the ATC facility.
Subpart D—Unmanned Fre« Balloons
I 101.31 Applicability.
This subpart applies to the operation of
unmanned free balloons. However, a person
operating an unmanned free balloon within a
restricted area must comply only with § 101.33
(d) and (e) and with any additional limita-
tions that are imposed by the using or control-
ling agency, as appropriate.
I 101.33 Operating limitations.
No person may operate an unmanned free
balloon—
(a) Unless otherwise authorized by ATC,
in a control zone below 2,000 feet above the
surface, or in an airport traffic area;
(b) At any altitude where there are
clouds or obscuring phenomena of more than
five-tenths coverage,
(c) At any altitude below 60,000 feet
standard pressure altitude where the hori-
zontal visibility is less than five miles;
(d) During the first 1,000 feet of ascent,
over a congested area of a city, town or set-
tlement or an open-air assembly of persons
not associated with the operation; or
(e) In such a manner that impact of the
balloon, or part thereof including its pay-
load, with the surface creates a hazard to
persons or property not associated with the
operation.
I 101.35 Equipment and marking require-
ments.
(a) No person may operate an unmanned
free balloon unless—
(1) It is equipped with at least two pay-
load cut-down systems or devices that oper-
ate independently of each other;
(2) At least two methods, systems, de-
vices, or combinations thereof, that function
independently of each other are employed for
terminating the flight of the balloon enve-
lope; and
(3) The balloon envelpe is equipped
with a radar reflective device(s) or material
that will present an echo to surface radar
operating in the 200 MHz to 2700 MHz
frequency range.
The operator shall activate the appropriate
devices required by subparagraphs (1) and (2)
of this paragraph when weather conditions are
less than those prescribed for operation under
this subpart, or if a malfunction or any other
reason makes the further operation hazardous
to other air traffic or to persons and property
on the surface.
[(b) No person may operate an unmanned
free balloon below 60,000 feet standard pres-
sure altitude between sunset and sunrise (as
corrected to the altitude of operation) unless
the balloon and its attachments and payload,
whether or not they become separated during
the operation, are equipped with lights that are
visible for at least 5 miles and have a flash
frequency of at least 40, and not more than 100,
cycles per minute.]
(c) No person may operate an unmanned
free balloon that is equipped with a trailing
antenna that requires an impact force of more
than 50 pounds to break it at any point, unless
the antenna has colored pennants or streamers
that are attached at not more than 50-foot in-
tervals and that are visible for at least one
mile.
(d) No person may operate [between sunrise
and sunset] an unmanned free balloon that is
equipped with a suspension device (other than
a highly conspicuously colored open para-
chute) more than 50 feet long, unless the.
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MOORED BALLOONS, KITES, UNMANNED ROCKETS, AND UNMANNED FREE BALLOONS PART 101
suspension device is colored in alternate bands
of high conspicuity colors or has colored pen-
nants or streamers attached which are visible
for at least one mile.
! 101.37 Notice requirements.
(a) Prelaunch notice. Except as provided
in paragraph (b) of this section, no person
may operate an unmanned free balloon unless,
within 6 to 24 hours before beginning the
operation, he gives the following information
to the FAA ATC facility that is nearest to the
place of intended operation :
(1) The balloon identification.
(2) The estimated date and time of
launching, amended as necessary to remain
within plus or minus 30 minutes.
(3) The location of the launching site.
(4) The cruising altitude.
(5) The forecast trajectory and esti-
mated time to cruising altitude or 60,000
feet standard pressure altitude, whichever
is lower.
(6) The length and diameter of the bal-
loon, length of the suspension device, weight
of the payload, and length of the trailing
antenna.
(1) The duration of flight.
(8) The forecast time and location of im-
pact with the surface of the earth.
(b) For solar or cosmic disturbance in-
vestigations involving a critical time element,
the information in paragraph (a) of this sec-
tion shall be given within 30 minutes to 24
hours before beginning the operation.
(c) Cancellation, notice. If the operation
is canceled, the person who intended to con-
duct the operation shall immediately notify
the nearest FAA ATC facility.
(d) Launch notice. Each person operating
an unmanned free balloon shall notify the
nearest FAA or military ATC facility of the
launch time immediately after the balloon is
launched.
§ 101.39 Balloon position reports.
(a) Each person operating an unmanned
"free balloon shall—
(1) Unless ATC requires otherwise, mon-
itor the course of the balloon and record its
position at least every two hours; and
(2) Forward any balloon position re-
ports requested by ATC.
(b) One hour before beginning descent,
each person operating an unmanned free bal-
loon shall forward to the nearest FAA ATC
facility the following information regarding
the balloon:
(1) The current geographical position.
(2) The altitude.
(3) The forecast time of penetration of
60,000 feet standard pressure altitude (if
applicable).
(4) The forecast trajectory for the bal-
ance of the flight.
(5) The forecast time and location of
impact with the surface of the earth.
(c) If a balloon position report is not
recorded for any two-hour period of flight,
the person operating an unmanned free balloon
shall immediately notify the nearest FAA
ATC facility. The notice shall include the
last recorded position and any revision of the
forecast trajectory. The nearest FAA ATC
facility shall be notified immediately when
tracking of the balloon is re-established.
(d) Each person operating an unmanned
free balloon shall, notify the nearest FAA
ATC facility when the operation is ended.
65
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APPENDIX B
SUMMARY OF RELEVANT EQUATIONS
FROM PHASE I
Standard Atmosphere
Most of the relationships derived in Phase I of the
project assumed a standard atmosphere. For reference, the
expressions used to represent the pressure P. density p. and
temperature T of the air as a function of altitude z below the
tropopause in a U.S. Standard Atmosphere are given below
(Morris. 1975):
Mg
P = PQ (1 - | z)aR (B-l)
o
n <*
p = PQ (1 - | z) (B-2)
o
T = TQ (1 - I z) (B-3)
o
where
g = 9.807 m/s2. acceleration due to gravity.
M = 28.96 kg/(kg - mol). average molecular weight
of air,
P0 = 1013.25 millibars or 1.01325 x 105 N/m2(Pa).
R = 8314.3 J/K (kg - mol), universal gas constant;
if pressures expressed in mb. then 83.143,
T0 = 288.15 K,
z = altitude in m MSL, or more strictly,
"geopotential meters".
a = 6.5 x 10~3 K/m. standard lapse rate,
P0 = 1.2250 kg/m3.
Mg
aR = 5.255.
66
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g.
T0 = 2.256 x 10-5 m-l
Other Definitions
gross lift (Newtons); if divided by the
acceleration due to gravity, units become kg
(force) ,
gross lift of a slack balloon (Ps = 0).
gross required lift to make system neutrally
buoyant at initial altitude ZQ and super-
pressure
m = mass of balloon system exclusive of gas in
balloon (kg),
Pa = ambient pressure of air at balloon altitude,
typically expressed in mb,
P5 = absolute gas pressure in balloon, typically
expressed in mb,
Ps = superpressure = P^ - Pa; typically
expressed in mb,
Pso = superpressure at altitude zo; initial
superpressure,
S = pumping or valving flow rate (m3/s).
V = volume of balloon (m3) (presumed constant).
z = the equilibrium altitude of the balloon in m
above mean sea level (MSL) ,
zm = maximum altitude attainable; ceiling altitude,
z0 = altitude at which superpressure is set to Pso,
pa = density of the ambient air at the altitude of
the system (kg/m3).
Pb = average density of gas contained in balloon
(kg/m3).
Y = lapse rate = -dT/dz (K/m)
67
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Pumpdown Velocity (vp)
The rate at which the equilibrium altitude of the balloon
(z) can be changed by pumping or valving in a standard
atmosphere:
V - || = -1.042 X 104 | (1 - 2.256 X 10~5Z) (B-4)
In a nonstandard atmosphere, with an arbitrary lapse rate
Y, the pumpdown velocity is given by:
,, = -ST /(V (3.416 X 10~2 - Y)) (B-5)
P a
Change of Equilibrium Altitude Resulting from an
Increment in Payload Mass
From B-4 and B-5, one can infer the change in equilibrium
altitude dz resulting from an increment dm in payload mass.
Talcing on additional air ballast is equivalent to increasing
the payload mass. Here dm = Spa dt. so
dZ -8.506 X 10 ,, „ _c, „ ir.-5 .-3.255 ,., ,.
•r- = 7} (1 - 2.256 x 10 z) (B-6)
in a standard atmosphere, or
~ = -2.871 T 2 / (P V (3.416 X 10~2- Y)) (B-7)
Oul 3 d
in an arbitrary atmosphere.
Superpressure As A Function of Equilibrium Altitude
and
PS = 2.396 X 104 yd- 2.256 X 10~5z) (B-8)
' --541 v (B-9)
68
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Using the expression for Ps, one can evaluate C.
VP
C = - S2 - (B-lO)
4 -5
2.396 X 10 (1 - 2.256 X 10 ZQ)
Effect of Temperature Swing on Balloon Pressure
_K 4
AP = 3.52 ((1 - 2.256 x 10 z) + 83.14 rr) AT .„ ...
V (.0— 1 i. ;
Energy Required for Pumpdown per Unit Altitude Change
dW/dz is expressed in Joules/m; note that 1 Joule/s is a
Watt.
,„ 9.60 x 10~3Port V
M __ so
dz -5 (B-12)
(1 - 2.256 x 10 ZQ)
Required Lift LR
To fill the balloon properly, one first puts in helium
until the gross lift is measured to be Lg as given below.
Then, one seals the inner balloon, and inflates the outer
balloon with air. until the desired initial superpressure
Pso is reached. At that point, the balloon system, after
attachment of the payload, should be approximately neutrally
buoyant.
P V
LR = ( m + M -^- ) g (B-13)
Ceiling Altitude zm
_ 0.2350
2.256 X 10-5
If the balloon was filled optimally, then Ls becomes Lg, the
required lift.
69
-------
APPENDIX C
SECOND GENERATION BALLOON DESIGN
Letter dated October 17. 1984. from Robert M. Enderson.
Raven Industries. Inc.. to Sandia National
Laboratories. Attention Bernard Zak.
70
-------
RAVEN INDUSTRIES, INC.
RAVEN
PC Bo> 100? S'0o« Palis SoutnO*Kota5~i "-'OC~
TewiWon* i605. 336 2T50 TWX91Q-660 0306
October 17, 1984
Sandia National Laboratories
Applied Atmospheric Research Division
Albuquerque, NM 87185
Attention: Mr. Bernard Zak
Subject: Raven Industries, Inc. Letter Proposal
No. ATD 1084122 For a Variable Density Balloon
Dear Mr. Zak:
Raven is pleased to present this proposal in response to your
requirement as discussed during your visit on 29 August.
The basic requirement is for a superpressure balloon capable of
supporting a twelve pound payload at an altitude of 500 mb.
Additional related requirements are as follows:
- vent fitting at top apex
- full volume bladder
- 3.5 inch inside diameter base fitting
(capable of inserting persons arm)
- helium inflation through base fitting
- handling lines
- rain skirt
Raven proposes balloon Model No. S-P3.0-D11.2. The balloon has a
diameter of 11.2 feet and is proposed to be fabricated from
polyester film. The balloon would be fabricated from twelve
gores and incorporate a polyurethane film bladder.
Design details of the proposed balloon are discussed in the
following paragraphs.
BALLOON MATERIAL
Polyester film with a thickness of 3.0 mils is the primary film
proposed. Raven has this film in stock, and for economic reasons
it has to be the primary choice. The computed stress at a
superpressure of 80 mb. is 12992 psi, slightly higher than the
targeted stress of 12000 psi.
Applied Technology Division / Electronic Systems Division ' Plastics D'vision ' Sportswear Division
71
-------
Raven will attempt to locate a stock source of film of a heavier
gauge than 3.0 mils before the balloon design is finalized. If a
heavier gauge film, up to 4.0 mils, can be located and at
acceptable cost, the design will be modified as necessary. A
slightly larger balloon would result. A 4.0 mil film would
reduce the stress to approximately 10000 psi.
BLADDER MATERIAL
The proposed bladder material is 1.0 mil polyurethane film. The
urethane film is proposed over polyethylene because of its lower
helium permeability rate. The measured helium permeability rate
of 1.5 mil polyethylene is 5.58 liters/mV24 hours, that of 1.0
mil urethane film 3.83.
The selection of urethane film is contingent upon acceptable
deployment of the bladder being obtained in tests. Polyethylene
will be utilized if deployment of a urethane film bladder is
unacceptable.
The bladder will be secured to the sphere with the vent fitting
at the top apex. This configuration will be the same as in the
similar balloons previously supplied.
The bladder will incorporate an inflation tube that will be
accessible through the base fitting and of a compatible diameter.
Inflation of the balloon/bladder assembly through the base
fitting will alleviate the necessity of turning the balloon via
the handling lines and the associated stress. The inflation tube
can be sealed with a single overhand knot when the inflation is
completed.
BASE FITTING
A basic requirement of the end fitting is that it is of a size
sufficiently large to allow a persons arm to be extended into the
balloon. This will require a minimum inside diameter of the
fitting of approximately 3.5 inches. This diameter will be more
than adequate to accommodate the 2.25 inch X 4.0 inch involved
circuit board.
A threaded fitting and a clamp configuration for securing the
fitting to the balloon will both be evaluated. The fitting, with
either basic configuration, will incorporate a threaded cap.
LOAD SUSPENSION
The load suspension will consist of three load patches installed
on the surface of the main shell with suitable nylon lines
extending to a confluence point.
72
-------
Two load patches will additionally be installed near the top of
the balloon for handling the balloon. The strength of the
patches will be increased over those previously supplied.
RAIN SKIRT
The balloon will incorporate a rain skirt. The skirt will be
installed at a 120° included angle location.
TERMINATION
The proposed balloon will incorporate a 3-wire twisted conductor
from the base to the top of the balloon.
The proposed price for the balloon is $1,537.00 each in a
quantity of ten. The price is F.O.B. Sioux Falls, S.D. Terms
are net thirty days.
Included in the price is an allowance for engineering and
testing.
If you have any questions regarding this proposal, please contact
me.
Sincerely,
RAVEN INDUSTRIES, INC.
Robert M. Enderson
Sales Engineer
Applied Technology Division
RME/js
73
-------
APPENDIX D
RATE OF DESCENT ON CUTDOWN
The cutdown system on the operational prototype Tracer uses
an electric match to melt a hole in a membrane which seals an
exhaust port on the helium-containing ballonet. After the
cutdown device fires, the helium vents through the resulting
hole which is typically about 1 cm2 in area. Venting is
initially driven by the superpressure in the balloon and.
consequently, is fairly rapid. However, as long as any
superpressure remains, the volume of the outer balloon is
approximately constant. Provided that the pump is not in
operation, venting of helium decreases the mass present in the
balloon, decreasing the average density of the contained gas.
This causes the equilibrium altitude of the Tracer Balloon to
rise slightly. Only after the superpressure reaches zero and
the volume of the balloon begins to shrink does the system
become negatively buoyant and begin to fall. The calculation of
descent rate starts at the point at which the superpressure
reaches zero.
To examine the behavior of the balloon as lift is lost, we
apply Newton's second law to the vertical motion:
mv
Here Fz is the net vertical force on the system, rav is the
virtual mass of the system (the actual mass plus the mass of
entrained air), and z is the altitude. As the balloon begins
descending, there are three components of Fz: the gross
lift, the force due to gravity, and the drag force acting on
the balloon.
F2 = L - mg * paC
Here L is the gross lift, m is the actual mass of the balloon
system, AD is its cross sectional area, and CD is a drag
coefficient. The gross lift L is given by
L - (pa - pb) V g (D-3)
In a slack balloon such as we assume for descent (Ps = 0).
this is equivalent to
L = (Pa - PHe> vHe 9 (D-4)
74
-------
where pfje is the density of helium, and Vjje is the
volume of helium contained in the balloon. The volume of air
contained in a slack balloon does not affect gross lift.
Note that the density of a gas is proportional to its
molecular weight. Hence, assuming that the helium in the
balloon is in thermal equilibrium with its surroundings.
pHe = 2879? pa (D~5)
(pa * PHe} = '862 pa (D~6)
Furthermore, the behavior of the volume of helium in the
balloon is given by the gas law
VHe
where n^e is the number of kg-moles of helium in the balloon
and the "a" subscript as elsewhere indicates the ambient
values of the respective variables.
Assuming a standard atmosphere, we may substitute the
appropriate expressions into D-4 and obtain
L = 0.862 n., M g (D-8)
rte
This is the interesting and well-known result that as long
as the helium in a zero-pressure balloon is in thermal
equilibrium with its surroundings, the gross lift depends only
on the amount of helium contained, not on the altitude.
We assume that the balloon comes to rest at its zero
superpressure equilibrium altitude. Then at t = 0,
L - mg = 0. and we need only concern ourselves with changes in
the net lift. Ln:
L = L - mg (D-9)
dL dn
- = °-862
75
-------
We may evaluate dnge/dt using the gas law (D-7), provided
that we note that nne = nHe (Ta. Pa. VHC). and that
Ta = Ta(z); Pa = Pa(z); VHe = VHe (z.t).
Thus.
dnHe 8nHe dz 8nHe
dt ~ 3z dt + 3t (D-ll)
We also know from the physics involved that 3nfje/3z = 0;
the number of moles of helium in a slack balloon is independent
of altitude if time is held constant.
Hence,
dnHe 8nHe
dt ~ 3t (D-12)
Making use of (D-7) and the above relationship, we find
IV Pa 8VHe
dt = RTa 3t (D-13)
Morris (1975) gives an expression for the rate of escape of
helium through an orifice of area A under assumptions which are
reasonable for the present case:
3V
-gS£ = -12.3 CA V
Here C is an orifice coefficient between 0.5 and 1. Making
use of equation D-7. we find:
_ ,, . _ , „_ 1/6
dt ' 8Ta at ' -12'3 CS (M > "He ' (D_15)
The net lift becomes:
t
(t) = f dLn = -10.6 MgCA / (=~) nu1/6dtl (D-16)
L dF / M ^e
76
-------
Substituting into equation D-l. we find:
',j.r.
This is a fairly complex integro-differential equation which
can be solved numerically if desired. However, it is
worthwhile to make some approximations to get an intuitive
understanding of the descent rate.
Consider a simpler case, the case examined in Chapter Six
of the Phase I report, in which the term containing the
integral is taken to be constant, as is the product
This simpler equation can be written as
-mLg + bv2 = % d? (D-18)
where m^ is the net buoyant mass of the system, b is a
redefined drag coefficient, and mv is as before, the virtual
mass, and v = dz/dt.
The solution to this equation, starting from rest relative
to the air. is known:
v = VT tanh fit (D-19)
where v-j is the terminal velocity:
m g
r- (D-20)
Here b = C . and
This solution implies a characteristic relaxation time T to
reach (1 - 1/e) of terminal velocity VT:
VT
T « 0.75 -^-^ (D-22)
77
-------
In these terms,
f "
/ (jj^
= 10.6 MCA () n dt' (D-23)
o
Neither (pa/M) nor nne change very rapidly, so we may
approximate the expression by taking these factors outside the
integral sign. Then
5/6
mL = 10.6 MCA (jp) r^e'6 t (D-24)
Consider descent from 5.5 km (the design goal ceiling
altitude) in a standard atmosphere. Under our assumptions, at
t = 0, (pa/M)5/6 = 4.48 x 10-2, nHe = .818. and thus
for a 1 cm2 hole with an orifice coefficient of l. m^ =
1.125 x 10-3 t. This expression for m^ implies that
initially, the negative buoyancy is accumulating at a rate of a
little over 1 g per second.
Consider the situation at 1000 seconds (16.7 minutes) after
cutdown activation. We assume CD = 0.5, and use the initial
values for (pa/M)5/6 and n^e. as well as for the
balloon cross-sectional area and pa. Then mL (1000) =
1.125 kg, b(1000) = 1.14. and v-rdOOO) = 3.11 m/s. These
results are consistent with the assumptions.
We obtain an estimate of the total time for descent from
5.5 km by extending the assumptions made above beyond 1000
seconds, and by assuming that at all times, v = VT -- that
is, that the relaxation time T is negligible. Since at 1000
seconds, we find that T is less than 4 seconds, this
assumption is reasonable.
Thus we have:
and
VT = -9.84 x 10 t (D-25)
ZQ - Z = 6.56 X 10 2 t3/2 (D-26)
78
-------
For z0 = 5.5 km. and z = 0. we find t = 1916 seconds (32
minutes), raL = 2.16 kg. and VT = 4.31 m/s (14.1 ft/s).
This is to be compared with a rate of descent of a personnel
parachute of about 6 m/s. Cutdown from lower altitude would.
of course, result in lower time to touchdown and lower terminal
velocity at touchdown.
Finally, it is worthwhile to note that this result is
relatively insensitive to the assumptions that (pa/M)5/6
and n^l/6 are constant and equal to their initial values at
5.5 km. The assumptions influenced the result through the
terminal velocity, v«p. After expanding the expression for
VT. one finds that the terminal velocity is directly
proportional to (nue/Pa)1''12' which decreases only
about 7% from 5.5 km to sea level.
79
-------
APPENDIX E
SOP NO. 29400 8512
Originating Org. 6324
Safe Operating Procedures
for
Handling and Using Electric Matches
in
Balloon Cutdown Devices
I. i/St:
J. B. Stieglerf(6320) Date
^
D. Host (3442)
Date
B. D. Zak (6324)
Date
D. Joe (3442)
Date
80
-------
1.0 References
Federal Aviation Regulations, Part 101 (Appendix A)
2.0 General
2.1 Scope
This SOP covers the handling of electric matches for
use in both free and tethered balloon cutdown devices.
Federal Aviation Regulations (FAR 101) specify the
conditions under which cutdown devices must be carried by
balloons. Pursuant to these regulations, a convenient
cutdown device utilizing electric matches has been
developed.
2.2 Location
Cutdown devices will be deployed whenever and wherever
balloons requiring them are to be used. It is expected
that those cutdown devices will henceforth use electric
matches.
3.0 Description of Hazardous Materials
3.1 The electric matches we plan to use are from
Atlas Powder Company, and are designated "electric match.
12" leads, without tube." These are available from Woodard
Explosives at 3305 Coors Blvd.. SW. in Albuquerque, for
less than $1 each. Electric matches of similar
characteristics are made by a number of manufacturers of
pyrotechnic devices. They are interchangeable.
81
-------
3.2 Electric matches consist of a small nodule of
readily combustible material deposited on a bridgewire.
The nodule consists of material similar to that
incorporated in friction matches, and is between the size
of a paper and a wood match head. The match is lit by
passing approximately a half amp of electric current
through the bridgewire. The hazard associated with the
flame resulting from lighting the match is the same as the
hazard associated with striking a friction match.
Nonetheless, electric matches are technically considered
class C explosives.
3.3 There are two main sources of hazard associated
with electric matches. The first is that they are
electrically operated, and hence may be inadvertently lit
more easily than friction matches. The second would arise
from storing large numbers in close proximity and in an
inappropriate container. Under those conditions, should
one match be inadvertently lit, all might go off. If the
container were not designed to stop flame propagation to
surrounding combustible materials, a significant fire
hazard would be created.
4.0 Personnel
4.1 The personnel authorized to work with electric
matches for balloon cutdown are given in Appendix B.
Additions to this list of authorized personnel may be made
as necessary from time to time.
4.2 Each individual on the list in Appendix B shall
sign and date this SOP in the space provided to acknowledge
that he or she has reviewed and understands the provisions
of this document.
82
-------
4.3 Enforcement of the requirements of this SOP shall
be the responsibility of the individual operating the
balloon system equipped with an electric match cutdown
device.
5.0 Storage
Electric matches will be stored in "Mound" cases.
These cases, developed by the Mound Laboratory, are
specifically designed to safely contain class C
explosives. Electric matches contained within a Mound case
will not be required to be stored in an explosives igloo.
According to explosives expert Paul Cooper (7132), the
hazard associated with electric matches contained in a
Mound case is negligible, and does not justify the major
inconvenience of igloo storage.
6.0 Transportation
Electric matches may be hand carried on any public or
private means of transportation in a Mound case with the
exception of commercial passenger aircraft. Means of
shipment must also exclude commercial passenger aircraft.
Shipment will be controlled by Transportation Division
3423, in accordance with U.S. Department of Transportation
regulations.
7.0 Fire Hazard Control
The cutdown devices shall be designed so that the
flame associated with the electric match is completely
contained in the device itself, and cannot propagate to
other combustible materials in the vicinity.
-------
8.0 Misfire Procedures
In the unlikely event of a misfire, the defective
electric match will be removed from the cutdown device and
destroyed. A match which has misfired does not represent a
special hazard. Ignition with a friction match will
suffice.
84
-------
APPENDIX F
OPERATIONAL PROTOTYPE
SCHEMATIC DIAGRAMS
85
-------
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95
-------
APPENDIX G
CONTROL PROGRAM
10 REM COM-D
20 Kl=l : K2=840 : K3=15 s K4=10000
30 T9=2 : T8=0 : Vl=0 : V2=0
40 DIM R(27) : ONERR 200
50 TIME=0 : CLOCK 1 : ONTIME 20,2500
170 REM ** PRT-2 **
190 DBY(38)=DBY(38).OR.l
200 REM ** SEN-1A **
205 PRINT "SENSOR"
210 N=0
220 C-l
230 P*DBY(35).AND.001H
240 IF P=0 THEN GOTO 230
250 A=GET
260 IF C>5 THEN GOTO 320
270 IF A=42 THEN GOTO 300
280 IF C>4 THEN GOTO 320
290 GOTO 220
300 C=C+1
310 GOTO 230
320 N=N+1
330 IF N>27 THEN GOTO 390
340 R(N)=A
350 P=DBY(35).AND.001H
360 IF P=0 THEN GOTO 350
370 A=GET
380 GOTO 320
390 IF R(l)=8 THEN GOTO 410
400 GOTO 200
410 FOR M=l TO 9 : S=0
420 FOR N=l TO 3 : Q=N+(M-1)*3
430 S=S*128+R(Q) : NEXT N : R(M)=S : NEXT M
440 REM SENSOR 10057
450 C0=283.9377 : Cl=3347.001 : C2=12490
460 C3=-14672.46 : C4=8112.58 : C5=-1795.773
470 C6=-14817.31 : C7=262.0390 : C8=7765.842
480 U1=(R(2)-R(4))/(R(1)-R(4))
490 02=(R(3)-R(4))/(R(1)-R(4})
500 P=CO+C1*U1+C2*01**2+C3*U1**3+C4*U1**4+C5*U1**5
510 P=P+C6*U1*U2+C7*U2*U1**2+C8*U1*U2**2
520 Al=100000 : A2=10000
530 M1=R(6)*A1/(R(5)-R(6))-A2
540 M2=A1*R(7)/(R(5)-R(7))-M1
542 M2=M2-19600
550 M3=A1*R(8)/(R(5)-R(8))-M1
560 M4=A1*R(9)/(R(5)-R(9))-M1
570 Rl=14000
580 L1=LOG(M2/R1) : L2=L1*L1 : L3=L2*L1
590 T5=1/(.0032987+L1*4.7764E-04+L2*3.0029E-06+L3*1.5108E-06)
600 T1=T5
610 REM ** COMPUTE P-TEMP **
620 T2=T1*(1000/P)**.286
810 H=M3 : P1=P : T9=l
1000 REM * PRT-3 *
1010 FOR N=l TO 4
96
-------
1020
1030
1040
1050
1060
1200
1210
1220
1230
1240
1250
1260
1270
1280
1290
1300
1310
1320
1330
1340
1350
1360
1370
1380
1390
1400
1500
1510
1520
1530
1540
1550
1560
1570
1600
1610
1630
1660
1700
1710
1730
1760
1800
1810
1815
1820
2000
2010
2020
2030
2040
2050
2060
2070
2080
R(N)=A*16**(N-1)
GOTO 1300
GOTO 1330
GOTO 1360
GOTO 1370
GOTO 1360
GOTO 1370
THEN
THEN
GOTO 1360
GOTO 1370
GOTO 1360
GOTO 1370
A=0
A=4
A=8
P=N-1 : PORT1=128+P
PORT1=P : PORT1=15
A=PORT1 : PORT1=128+P
NEXT N
Z=R(1)+R(2)+R(3)+R(4)
REM ** PRT-4 **
IF Kl=l THEN GOTO 1270
IF Kl=2 THEN
IF Kl=3 THEN
IF Kl=4 THEN
IF Kl=5 THEN
GOTO 1270
IF P1>K2+1 THEN
IF PKK2-1 THEN
GOTO 1350
IF T2K3+0.1
GOTO 1350
IF 2>K4+500 THEN
IF Z3 THEN R(10}=0
R(11)=K1 : R(12)=T8
FOR N=13 TO 16 : R(N)=0 : NEXT N
REM ** S-TEL **
PORT1=255 : PORT1=160
FOR N=l TO 10 : A=SIN(N) : NEXT N
PORT1=255 : BAUD 1200 : Q=48 : PRINT fCHR(Q),
FOR N=l TO 16 : A=R(N)
IF A<0 THEN A=A*(-1) : B=INT(A/256)
C=INT(A-256*B) : PRINT fCHR(B), : PRINT #CHR(C),
NEXT N
REM * VIEW *
FOR N=l TO 16 : A=INT(R(N)}
IF A<0 THEN A=A*(-1) : PRINT A, : NEXT N
PRINT : T8=0 : D=0
REM *PRT-6A*
IF T9=2 THEN GOTO 200
PORT1=145 : PORT1=17
PORT1=31 : A=PORT1
PORT1=145 : A=A-16
PORT1=146 : PORT1=18
PORT1=31 : B=PORT1
PORT1=146 : B=B-16
C=A+16*B
97
-------
2082 IF C=D THEN GOTO 2090
2084 D=C : GOTO 2000
2090 IP O128 THEN GOTO 2260
2100 IF C=64 THEN GOTO 2250
2110 IF C=32 THEN GOTO 2240
2120 IF C=16 THEN GOTO 2200
2130 IF C=8 THEN GOTO 2160
2140 IF C=4 THEN Kl=5
2145 IF C=l THEN GOTO 2280
2150 IF C=0 THEN GOTO 2300
2155 GOTO 2270
2160 IF Kl=l THEN K2=K2-1
2170 IF Kl=2 THEN K3=K3-1
2180 IF Kl=3 THEN K4=K4-500
2190 GOTO 2270
2200 IF Kl=l THEN K2=K2+1
2210 IF Kl=2 THEN K3=K3+1
2220 IF Kl»3 THEN K4=K4+500
2230 GOTO 2270
2240 Kl=3 s K4=Z : GOTO 2270
2250 Kl=*2 : K3=T2 : GOTO 2270
2260 Kl=l : K2=P1 : GOTO 2270
2270 PORT1=16*3+128
2280 T8=C : PRINT "COMMAND"
2300 IF T9-3 THEN GOTO 2460
2305 FOR N=l TO 20 : M=SIN(N) : NEXT N
2310 PORT1=255
2320 GOTO 2000
2460 T9=2 s RETI
2500 REM TIME INTERUPT
2510 A=TIME
2520 ONTIME A+42,2500
2530 IF T9=2 THEN GOTO 2550
2540 T9=2 : RETI
2550 T9=3 : Kl=5 : Tl=0
2560 Pl=0 : T2*0 : H=0
2570 GOTO 1000
REM
98
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APPENDIX H
TRACER BALLOON: ARG05 DATA FRAME ASSIGNMENT
A typical data frame transmitted by the Tracer balloon light be:
F64CBA 00 B6 SO 56 OB 58 01 92 IB F9 01 8B 03 48 00 OB
01 FF 20 5E 01 1C 00 01 00 00 00 00 00 00 00 00
These data, excepting the identification number, are hexadecimal-encoded
sensor data.
Data word no.
1
2,3
4,5
6,7
8,9
10,11
12,13
14,15
16,17
18,19
20,21
22,23
24,25
26 to 33
Value in example
F64CBA
OD.B6
20,56
OB, 58
01,92
1B.F9
01,88
03,48
00,06
01,FF
20,5E
01,1C
00,01
All 00
Control Codes:
1= Pressure
2= Potential temp.
3= Vertical anem . count
4= Pump only
Assignment
Identification number
Elapsed time since launch (sec.)
Pressure (•bftlO)
Air temp. (deg. Kelvin*10)
Humidity (sensor resistance, ohmsftlO)
Potential temp. (deg. KelvinttlO)
Strain (ohms/100))
Vertical anemom. (revolutions*50)
Count of pump cycles
Count of valve cycles
Current control value
Control code
Last command code
Not assigned
Last Command Codes:
128= Control on pressure
64s Control on potential temp
32s Control on vert, anem. count
16- Increment current parameter
8s Decrement current parameter
4- Pump only
2= Reset cutdown timer
1= Cut down command
99
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APPENDIX I
Determination of Balloon Volume vs Superpressure
The volume of the balloon as a function of superpressure
was determined using a digital scale, a manometer, a ther-
mometer. and a barometer. The digital scale used here had a
20 kg capacity, and 1 g resolution. The wall-mounted
manometer was made from tygon-tubing and a metre stick. The
manometer fluid was ethylene glycol (antifreeze). The
superpressure measurements were adjusted for the density of
the ethylene glycol. All measurements were made in quiescent
air so that stable readings could be obtained on the scale.
First, the balloon itself (empty) and the attachments
which were to be in place during the test were weighed, and
the weight recorded. Next, a weight of magnitude greater than
the buoyant force the balloon could generate when filled with
helium was placed on the scale. In this case, a concrete
block was used. Its weight was recorded.
Next, the balloon was attached to the weight on the scale,
and the ballonet was partially filled with helium until the
measured lift Ls was approximately egual to the "required
lift" LR (Equation B-13).
Ls' is given by
Ls = (mw + mb - ms)g (1-1)
Here mw = mass of weight (kg), m^ = mass of balloon
(kg), and ms = scale reading (kg). At this point, the lift
is given by Equation D-8.
Ls = (1 - MHe/M)nHe Mg = 0.862 nHe Mg (1-2)
This expression assumes that the gas in the balloon is in
thermal equilibrium with its surroundings, and that the balloon
is slack.
The gross lift depends only on how much helium is in the
balloon, independent of how much air is also present. Since
Ls is effectively measured by the scale, this equation allows
to be measured. Throughout all subsequent measurements.
remains fixed.
Next, the manometer was attached to the outer balloon, and
an auxiliary pump used to inflate the outer balloon with air.
100
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No significant change in scale reading occurred until the
superpressure became non-zero. Then the reading on the
manometer (which reads superpressure) and the reading on the
scale both began to rise. Periodically, the scale reading, the
superpressure. the ambient pressure, and the ambient
temperature were all recorded. This data allowed the volume of
the balloon to be determined as a function of superpressure.
The derivation of the relationship is as follows:
The lift is given by
L - (pa - Pb)Vg (1-3)
where pa, the density of the displaced ambient air can
be calculated from the gas law and the measured values of
ambient pressure pa and temperature T:
pa = MPa/(RT) (1-4)
Pb, the density of the gas in the balloon is given by
the mass of that gas divided by the volume.
pb = (nHe MHe + nA M)/V (1-5)
where nA = number of kilogram moles of air in the
balloon. Expanding, we find
nA - Pav/ |