United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-83-116 Dec. 1983
Project Summary
Design of a Remotely Controlled
Hovercraft Vehicle for
Spill Reconnaissance
Keith Souter, Gerald Seemann, Henry Gustafson, and Roy Furr
This program was undertaken to
design a prototype of a remotely con-
trolled vehicle for reconnaissance use in
hazardous material spill and release
environments and to assemble and test
a much simplified prototype.
The characteristics of past hazardous
material spills were evaluated to deter-
mine the type of vehicle best suited for
the reconnaissance duty and to develop
the vechicle's performance standards.
Based on the conditions present at a
"typical spill," the desired vehicle capa-
bilities, and the level of operator skill
reasonably expected, the vehicle selec-
ted was a ground-effect machine (GEM)
or hovercraft.
A skirted-hovercraft design was
chosen over a peripheral-jet design
because of power requirements. The
proposed 8-ft diameter, 3OO-lb hover-
craft is designed to clear obstacles
approaching 18 in. in height using only
4 HP versus the 15 HP required by a
peripheral-jet craft. The body of the
vehicle has a sandwich-panel construc-
tion, using Nomex™ honeycomb filler
between Kevlar™ face-sheets to yield a
corrosion-resistant structure of high
strength and an acceptable stiffness-to-
weight ratio. High technology but state-
of-the-art batteries and electric DC
motors can drive a propulsion system
that gives the vehicle an estimated 1.5-
hr in-flight endurance at maximum
power output and an effective operating
range of 1 /2 mile. Greater heights could
be attained by some design changes
and by operating at higher power levels
for shorter times (acceptance of shorter
reconnaissance periods at greater cost
per period). The design also includes a
television camera (high or low level
lighting; visible, IR, UV) and a variety of
gas sensors for remote reconnaissance
of a spill or waste release area. In the
half-scale prototype (4-ft OD), a small
gasoline 1C engine provided sufficient
lift to clear 3-in. barriers; yaw was
controlled with two battery-powered
thrusters. An 8-mm cine camera was
mounted on the unit, which was maneu-
vered by an RF (radio frequency) link.
This Project Summary was developed
by EPA's Municipal Environmental Re-
search Laboratory. Cincinnati, OH, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
This report describes the conceptual
design of a prototype remotely controlled
reconnaissance vehicle for use in a
hazardous environment. The work was
performed for EPA's Oil and Hazardous
Materials Spills Branch, Edison, New
Jersey.
In recent years, hazardous materials
spills and releases have increased in
frequency, severity, and distribution with
a concomitant increase in loss of life,
injuries, and property damage. This prob-
lem is expected to be exacerbated in the
coming years.
Determination of the nature and source
of a spill is the critical first step in
controlling the situation. Further, in some
spill or release situations, the nature
and/or origin of the spill cannot be
determined because of conditions caused
by the spilled material (chemical haze,
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fire, etc.) or obstructions at the spill site.
Reconnaissance of a spill site involves
considerable risk when personnel must
enter a potentially lethal environment.
The U.S. Environmental Protection
Agency's Municipal Environmental Re-
search Laboratory recognized the need
for a remotely operated device that could
be sent into a spill area to provide
information on the nature of the spill and
to provide a means of stopping or neutral-
izing the spill or release. In response to
this need, the Department of Fire, City of
Oxnard, Oxnard, California, was awarded
a grant to design a device that could
achieve such a goal without endangering
workers. The Department of Fire chose
Developmental Sciences, Inc. (DSI), as its
prime contractor to perform the technical
work on this program. DSI has been
involved extensively in the manufacture
of remotely piloted vehicles and has acted
as a prime contractor to the Army, Air
Force, Navy, and NASA on various un-
manned vehicle programs.
The ultimate goal of the complete
program was the construction, testing,
and actual use of a full-scale system. The
intermediate goals were the description
and design of a full-scale device and the
production and testing of a stripped-down,
half-scale prototype. Funding limitations
permitted achievement of only the inter-
mediate goals. Thus, only the design and
specification of the full-scale system and
the configuration and operation of a half-
scale model are discussed in the project
report.
Discussion
Vehicle Selection
Existing data on hazardous substance
spill and release situations, as well as the
input from discussions with fire depart-
ments and other agencies that have
experienced large spills, were analyzed to
isolate certain spill characteristics that
would determine the design of the vehicle
and the performance standards. Based on
the results of this review, the following
conclusions were reached:
1. The vehicle must, in noway, accentu-
ate the existing hazard, especially by
introducing a source of sparks into a
flammable environment.
2. The vehicle should have a range of
approximately 1/2 mile, an endur-
ance of 1 /2 hr, and should be able to
traverse a 20° slope and 18-in. high
obstacles.
3. The vehicle should be compact and
easily maneuvered.
4. Operator skill levels should be rela-
tively low.
5. Maintenance and repair require-
ments should be minimal.
6. The vehicle should provide some form
of remote chemical analysis (e.g., gas
meters, explosion meters).
It was further concluded that remote
reconnaissance was the single most
desirable capability of the device. The
ability to perform certain spill mitigating
tasks, while very useful, was determined
to be an impractical goal in light of the
large variance in corrective measures
necessary for specific spills. Specifically,
mechanical actions by the device can only
be accomplished when the vehicle can
provide the required reaction (Newton's
third law), which means that there must
be the extra power capacity to provide
high, instantaneous torque and/or thrust,
a requirement that severely complicates
design and adds excessive weight.
Three classes of vehicles were consid-
ered for use as a remote reconnaissance
device.
The first class considered was ground-
based vehicles including wheeled,
tracked, and even "walking" vehicles or
robots. The tracked vehicles were rejected
primarily because of their inability to
traverse large "muddy" areas that may be
caused by large volume spills. A highly
modified version of a commercially avail-
able "all terrain vehicle" (ATV) was also
considered. Although ATV's can travel
over large areas and with heavy payloads,
they were rejected because the ATV must
travel through the spill, which would be
undesirable or impractical under certain
conditions. It was also judged that an ATV
would be more valuable as a cleanup tool
rather than as a reconnaissance vehicle,
and that ATV manufacturers could meet
any demand for modified vehicles that the
cleanup industry might be willing to pay
for. Walking devices (and robots) were
(1978) emerging as state-of-the-art sys-
tems and could be expected to become
available for spill reconnaissance and
cleanup by the private sector.
The second class of vehicle considered
was ground-effect machines (GEM) or, as
they are commonly referred to, hovercraft.
This type of vehicle offers a major advan-
tage in that it can traverse a wide range of
terrains with minimal ground contact.
These features not only minimize the
degree of corrosion resistance necessary
but also reduce the risk of spark genera-
tion caused by the striking of hard objects
by the vehicular components of the other
classes.
The third class of vehicle considered
was free-flying craft, such as remotely
controlled helicopters of ducted-rotor
design, "model" airplanes, and lighter-
than-air crafts (blimps). While this class
offered reconnaissance capability, the
complexity and cost of the devices, cou-
pled with the level of operator skill
required to operate such vehicles, elimi-
nated them from consideration. In partic-
ular, small radio-guided aircraft cannot
hover or move at the low speeds neces-
sary for detailed reconnaissance at short
distances. Blimps present serious prob-
lems in maneuverability and in stability in
crosswinds and up-and-down-drafts.
As a result of the analysis, it was
concluded that the GEM or hovercraft
would be best suited for this particular
application.
Vehicle Conceptual Design
The two basic hovercraft designs are
the peripheral-jet hovercraft and the
skirted hovercraft (Figure 1). The peri-
pheral-jet design was eliminated because
of the high power requirements for
obtaining sufficient ground clearance to
move above sizeable objects. The skirted
design, on the other hand, allows the
craft to pass over substantial obstacles
without the need for the larger, power-
consuming "daylight" clearance neces-
sary in a peripheral-jet machine. The
skirted hovercraft provides comparable
performance with a smaller power unit.
Note that operation only in the ground-
effect mode is being considered. The
lifting and traversing thrust is obtained by
action against the ground plane. Opera-
tion beyond the ground-effect mode re-
quires action against the atmosphere
(including the expelled thrusting gas
itself), i.e., operation in a rocket mode,
where much greater power is required for
flight and for hovering at high altitudes.
Vehicle Components
Power
An electrical source power was chosen
to drive the propulsion system. Consider-
ation was given to other systems, includ-
ing pneumatic and liquid nitrogen
engines. Applying recent advances in
battery and DC electric motor technol-
ogies, a lightweight system consisting of
graphite composite batteries (450 watt-
hr/lb)andbrushless, selenium-cobalt DC
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Solid Hull
A) Peripheral-jet
Height of daylight gap must at
least equal obstacle height.
//////////// / / / / / / / / / / / /////////////// /• /
B) Skirted
Skirt deforms to absorb obstacles
under craft without large daylight clearance.
Figure 1. Basic peripheral-jet and skirted hovercraft concepts.
electric motors was designed. The system
requires only 4 Ib of total weight for each
horsepower produced. Thrust, braking,
and yaw movements are provided by two
20-in. diameter, variable/reversible pitch,
ducted rotors.
Control
An on-board autopilot is included in the
design because of the complexity and
frequency of the commands necessary to
keep the hovercraft on course. The auto-
pilot's function is to make changes in the
direction and magnitude of thrust to
compensate for varying terrain and wind
conditions. This feature frees the operator
to concentrate on controlling the craft's
forward speed and lift and operating
ancillary equipment such as TV camera
and samplers. Depending chiefly on the
type of TV imaging desired, the GEM will
be controlled and transmit data by RF or
microwave links as determined by the
bandwidth needed. Operations will be
essentially line-of-sight.
Camera and Sensors
The remote reconnaissance capability
is provided by an on-board TV camera
(mounted on pan/tilt gimbals) and meter-
type gas/vapor sensors or detector tubes.
The use of these sensors will allow the
operator to "man" gas/vapor concentra-
tions, thus aiding in locating the spill or
leak.
Performance objectives for the pro-
posed prototype are given in Table 1.
Table 1. Prototype Vehicle Performance
Characteristics
Characteristic
Requirement
Maximum velocity
Maximum grade
capability
Wfps
20 degrees
Maximum crosswind
(at forward velocity
of 4 fps) 25 knots
Maximum obstacle
height 18 in.
flange (from
command post) 0.5 mile
Endurance (new
batteries, maximum
power consumption) 1.5 hr
Turning circle
diameter 0 in. *
* The vehicle can rotate, in place, about its own
axis.
Construction/Test of a Half-
Scale GEM Hovercraft
Concomitant with the design study for
a full-scale GEM, a simplified, half-scale,
skirted model was constructed and tested.
The unit was powered by a low HP gaso-
line 1C engine (with explosion-initiation
protection equipment on the exhaust) to
drive the lift fan and two, small, battery-
powered DC electric motors to power
opposed thruster rotors. The unit was
controlled by an RF link adapted from
those used with model airplanes. There
was no auto-pilot. A super 8-mm cine
camera was mounted on the system,
which resembled a large "Frisbee" (ca.
30 cm [12 in.] high) with a top hat in the
center. The unit was maneuvered about a
warehouse at about 7.5 cm (3 in.) above
the floor. Subsequently, a portable B/W
TV camera was installed (fixed mount)
and signal was returned to the operating
console with a thin, lightweight, trailing
co-axial cable. The model operated in
such a manner as to reinforce the design
and operational expectations for the full-
scale system.
The full report was submitted in fulfill-
ment of Grant No. R-805365 by the City of
Oxnard and its subcontractor Develop-
mental Sciences, Inc., under the sponsor-
ship of the U.S. Environmental Protection
Agency.
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Henry Gustafson and Roy Furr were with the City of Oxnard, Oxnard, CA 90303;
Keith Souter and Gerald Seemann were with Development Sciences, Inc., City
of Industry. CA 91744, when the project was performed.
John E. Brugger is the EPA Project Officer (see below).
The complete report, entitled "Design of a Remotely Controlled Hovercraft
Vehicle for Spill Reconnaissance," (Order No. PB 84-124 904; Cost: $8.50,
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650'
The EPA Project Officer can be contacted at:
Oil & Hazardous Materials Spills Branch
Municipal Environmental Research Laboratory—Cincinnati
U.S. Environmental Protection Agency
Edison, NJ 08837
frUS GOVERNMENT PRINTING OFFICE 1984-759-015/7250
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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