![[Apollo 17 Lunar Roving Vehicle]](/planetary/image/as17_146_22367.jpg)
The Lunar Roving Vehicle (LRV) was an electric vehicle designed to operate in the
low-gravity vacuum of the Moon and to be capable of traversing the lunar surface,
allowing the Apollo astronauts to extend the range of their surface extravehicular
activities. Three LRVs were driven on the Moon, one on Apollo 15 by astronauts
David Scott and Jim Irwin, one on Apollo 16 by John Young and Charles Duke, and
one on Apollo 17 by Gene Cernan and Harrison Schmitt. Each rover was used on three
traverses, one per day over the three day course of each mission. On Apollo 15
the LRV was driven a total of 27.8 km in 3 hours, 2 minutes of driving time. The
longest single traverse was 12.5 km and the maximum range from the LM was 5.0 km.
On Apollo 16 the vehicle traversed 26.7 km in 3 hours 26 minutes of driving. The
longest traverse was 11.6 km and the LRV reached a distance of 4.5 km from the LM.
On Apollo 17 the rover went 35.9 km in 4 hours 26 minutes total drive time. The
longest traverse was 20.1 km and the greatest range from the LM was 7.6 km.
![[Apollo 15 Lunar Roving Vehicle]](/planetary/image/as15_88_11901.jpg)
The Lunar Roving Vehicle had a mass of 210 kg and was designed to hold a
payload of an additional 490 kg on the lunar surface. The frame was 3.1 meters
long with a wheelbase of 2.3 meters. The maximum height was 1.14 meters. The
frame was made of aluminum alloy 2219 tubing welded assemblies and consisted of
a 3 part chassis which was hinged in the center so it could be folded up and hung
in the Lunar Module quad 1 bay. It had two side-by-side foldable seats made of
tubular aluminum with nylon webbing and aluminum floor panels. An armrest was
mounted between the seats, and each seat had adjustable footrests and a velcro
seatbelt. A large mesh dish antenna was mounted on a mast on the front center of
the rover. The suspension consisted of a double horizontal wishbone with upper
and lower torsion bars and a damper unit between the chassis and upper wishbone.
Fully loaded the LRV had a ground clearance of 36 cm.
![[Apollo 17 Lunar Roving Vehicle]](/planetary/image/as17_147_22526.jpg)
The wheels consisted of a spun aluminum hub and an 81.8 cm diameter, 23 cm wide
tire made of zinc coated woven 0.083 cm diameter steel strands attached to the
rim and discs of formed aluminum. Titanium chevrons covered 50% of the contact
area to provide traction. Inside the tire was a 64.8 cm diameter bump stop frame
to protect the hub. Dust guards were mounted above the wheels. Each
wheel had its own electric drive, a DC series wound 0.25 hp motor capable of
10,000 rpm, attached to the wheel via an 80:1 harmonic drive, and a mechanical
brake unit. Manuevering capability was provided through the use of front and
rear steering motors. Each series wound DC steering motor was capable of
0.1 hp. Both sets of wheels would turn in opposite directions, giving a
steering radius of 3.1 meters, or could be decoupled so only one set would be
used for steering. Power was provided by two 36-volt silver-zinc potassium
hydroxide non-rechargeable batteries with a capacity of 121 amp-hr. These were
used to power the drive and steering motors and also a 36 volt utility outlet
mounted on front of the LRV to power the communications relay unit or the TV
camera. Passive thermal controls kept the batteries within an optimal
temperature range.
![[Lunar Roving Vehicle Deployment]](/planetary/image/lrv_display.jpg)
A T-shaped hand controller situated between the two seats controlled the four
drive motors, two steering motors and brakes. Moving the stick forward
powered the LRV forward, left and right turned the vehicle left or right, pulling
backwards activated the brakes. Activating a switch on the handle before
pulling back would put the LRV into reverse. Pulling the handle all the way
back activated a parking brake. The control and display modules were situated
in front of the handle and gave information on the speed, heading, pitch, and
power and temperature levels. Navigation was based on continuously recording
direction and distance through use of a directional gyro and odometer and
inputting this data to a computer which would keep track of the overall
direction and distance back to the LM. There was also a Sun-shadow device which
could give a manual heading based on the direction of the Sun, using the fact
that the Sun moved very slowly in the sky. The image at left shows a diagram
of the layout of the control and display module, the Sun-shadow device is at
top center between the heading and speed readouts.
![[Lunar Roving Vehicle Deployment]](/planetary/image/lrv_deployment_art.jpg)
Deployment of the LRV from the LM quad 1 by the astronauts was achieved with a
system of pulleys and braked reels using ropes and cloth tapes. The rover was
folded and stored in quad 1 with the underside of the chassis facing out.
One astronaut would climb the egress ladder on the LM and release the rover,
which would then be slowly tilted out by the second astronaut on the ground
through the use of reels and tapes. As the rover was let down from the bay
most of the deployment was automatic. The rear wheels folded out and locked in
place and when they touched the ground the front of the rover could be unfolded,
the wheels deployed, and the entire frame let down to the surface by pulleys.
The rover components locked into place upon opening. Cabling, pins, and tripods
would then be removed and the seats and footrests raised. After switching on all
the electronics the vehicle was ready to back away from the LM. The image at right
shows an earlier version of the planned deployment which does not exactly match
the final sequence, note for example that the rover is facing away from the LM
after deployment.
![[Lunar Roving Vehicle]](/planetary/image/lrv_s71_00166.jpg)
The original cost-plus-incentive-fee contract to Boeing (with Delco as a major
sub-contractor) was for $19 million and called for delivery of the first LRV by
1 April 1971, but cost overruns led to a final cost of $38 million. Four lunar
rovers were built, one each for Apollos 15, 16, qnd 17, and one that was used for
spare parts after the cancellation of further Apollo missions. There were other
LRV models built: a static model to assist with human factors design, an
engineering model to design and integrate the subsystems, two 1/6 gravity models
for testing the deployment mechanism, a 1-gravity trainer to give
the astronauts instruction in the operation of the rover and allow them to
practice driving it, a mass model to test the effect of the rover on the LM
structure, balance and handling, a vibration test unit to study the LRV's
durability and handling of launch stresses, and a qualification test unit to
study integration of all LRV subsystems. The LRV was developed in only 17
months and yet performed all its functions on the Moon with no major anomalies.
Harrison Schmitt of Apollo 17 said, "....the Lunar Rover proved to be the
reliable, safe and flexible lunar exploration vehicle we expected it to be.
Without it, the major scientific discoveries of Apollo 15, 16, and 17 would not
have been possible; and our current understanding of lunar evolution would not
have been possible."
Apollo home page
Apollo 15 lunar surface mission
Apollo 16 lunar surface mission
Apollo 17 lunar surface mission
Lunar Rover Operations Handbook
Lunar Roving Vehicle - Air and Space Museum
The Human Rover Challenge - NASA
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