Experiment Operations During Apollo EVAs

Experiment: Lunar Rover Vehicle

Acronym: LRV


This view of the LRV from Apollo 16 shows the crewman at the front and the tool carrier at the left (AS-16-108-17729). See other views of the LRV (1) and (2). Compare the antenna on the LRV to the erectable antenna.

PI/Engineer: NA
Other Contacts:

Apollo Flight Nos.: 15, 16, 17
Apollo Exp't No. NA

Discipline: rovers

Weight: 200 kg; Could carry 490 kg of payload, including 2 astronauts, PLSS's, tools, equip't, & 27 kg of lunar samples each trip
Dimensions:
3.1 m long, 1.83 m wide, 1.14 m high; 2.3 m wheelbase

Manufacturer: Boeing

Description/Purpose:
This rover was used to extend the range of the astronauts so that a greater variety of terrain could be visited. It had a 90 inch wheelbase, was 81 inches wide, and weighed 455 lbs empty. Its gross operational weight was 1535 pounds with crew, equipment, and payload. Power was supplied by two 36 V silver zinc batteries with sufficient power for a range of 65 km at speeds up to 17 km/h, although a top speed of 22 km/h was obtained on A-16. If either battery failed the other could carry the entire load. Four separate motors, one at each wheel, drove the vehicle, but any wheel could be cut out to "free-wheel" if its drive mechanism developed problems. All the driving functions were controlled by a T-handle mounted between the seats. The vehicle had four wheel, double Ackerman steering. It could climb over obstacles 30 cm high, climb and descend slopes of 25 degrees, and park on slopes of up to 35 degrees. Speeds of 10 kph were attained within 3 vehicle lengths. Going in reverse was possible with one dismounted crew member confirming the general condition of the surface to be covered, but this was not often done.

Unloading from the LM:
For deployment, some thermal blankets needed to be removed from the LM and one of the crew had to climb the ladder to pull a "D-ring", then descend the ladder. Both crew then had to apply a steady pull on deploy cables and tapes until the wheels were on the ground. After it was on the ground, the crew actually picked it up and turned it 90deg. The fenders, seats, seat belts, and console then had to be deployed on it. On A-15 there were some problems with deployment and checkout, but they were quickly solved. It took 26.5 minutes rather than the 17 planned. A-16 also had to lock some pins to complete deployment.

On A-15, during the first traverse the front steering did not work, but the rear steering allowed them to complete the EVA without problems. While going downhill with any speed and the front wheels locked in the straight ahead position they did a "180" turn when they tried to maneuver. On the second and third EVA the front steering became operable. This rover covered 27.9 km by its odometer, corresponding to a map distance of ~ 25.3 km. Its average speed was 9.6 km/hr, and speeds up to 12 km/hr were attained over level terrain. The A-16 LRV covered 27 km. The A-17 LRV covered ~35 km. The longest traverse was on A-17, where it covered 19.5 km during EVA 2.

Transporting by foot or MET: NA

Loading/unloading tools/exp'ts on LRV:
A loading and unloading time was allotted for putting tools and equipment on the LRV. Checklists existed for these procedures.

Site selection:
An operational constraint on the use of the LRV was that the astronauts must be able to walk back to the LM if the LRV were to fail at any time during the EVA. Thus, the traverses were limited in the distance they could go at the start and at any time later in the EVA. Therefore, they went to the furthest point away from the LM and worked their way back to it so that, as the life support consumables were depleted, their remaining walk back distance was equally diminished. A Buddy Secondary Life Support System was carried on the LRV to share cooling water from one PLSS to the other if one failed.

Deploying experiment: see above.

Check-out of experiment:
The CDR took the LRV for a test spin around the LM to the vicinity of the MESA after deployment. The tools and other equipment needed on the EVA were loaded from the MESA and Quad III onto the LRV.

Operation of experiment:
On A-15, the seat belts were difficult to fasten. Pre-launch adjustments did not properly account for the reduced gravity in combination with the pressurized suits, and the belts were too short. This was corrected for A-16 & 17 by measuring the settings on the KC-135. Detailed procedures for off-load, set-up, power-up, navigation alignment, stopping at traverse sites, navigation updates, mal-functions, and close-outs are provided in the Final Surface Procedures documents.

Repairs to experiment:
The rear fender extension on the A-16 LRV was lost during EVA2 at station 8 when Young bumped into it while going to assist Duke. The dust thrown up from the wheel covered the crew, the console, and the communications equipment. High battery temperatures and resulting high power consumption ensued. No repair attempt was mentioned. The fender extension on the A-17 LRV broke when accidentally bumped by the CDR with a hammer handle. The crew taped the extension back in place, but because of the dusty surfaces, the tape did not adhere and the extension was lost after about 1 hour of driving, allowing the astronauts to be covered with dust. For the second EVA, a replacement "fender" was made with some EVA maps, duct tape, and a pair of clamps from inside the LM - nominally used for the moveable overhead light. This repair was later undone so that the clamps could be brought back inside for launch. The maps were brought back and are now on display at the National Air and Space Museum. The abrasion from the dust is evident on some portions of the makeshift fender.

Recovery/take-down of experiment: NA

Stowing experiment for return: NA

Loading/unloading samples on LRV:
Sample containers and tools were attached at the rear of the LRV.

Loading of exp't/samples into the LM: NA

Stowing of package once in the LM: NA

Sampling operations - soil, rocks:
Some of the tools and sample collection bags (see Lunar geology - tools) attached to a tool carrier which attached to the back of the LRV to aid in sampling. Also, on A-17 only, there was a new sampling device (LRV soil sampler, see Geology - Tools) that allowed for the collection of samples while seated in the LRV. Thus, A-17 is the only LRV-aided mission with samples collected between stations.

Trenching: NA

Raking:
The rake was carried in the rear-mounted tool carrier.

Drilling: NA

Coring: NA

Navigating/recognizing landmarks:
The requirements for the rover were that it display vehicle heading, bearing to the last point of initialization (usually the LM), speed (km/h), total distance traveled (km), and distance to the LM (km). It did not need to have pitch, roll, X and Y coordinates, or time, although a pitch indicator was present on all LRVs. At the start of a traverse the astronauts oriented the system's navigational gyroscope with reference to the sun. It took nearly two minutes for the gyro to reach operating speed. The navigation system was said to be accurate to within 100 meters of range. At the end of EVA 1 on A-15 when the crew returned to the LM they estimated its bearing at 15deg, but the navigation system said it was at 34deg, indicating some drift, but the range accuracy may still have been correct.

On A-15, dust was kicked up on acceleration of the LRV and when crossing the rims of soft craters. Little of the dust impacted on the LRV itself or on the crew, and it did not cause any problems with visibility or operation of the vehicle, although frequent cleaning of the lunar communications relay unit (LCRU) was required to prevent overheating of the TV circuits. No dust accumulation was noted in the wire wheels, but a thin layer of dust eventually covered most of the vehicle.

Minor operational problems were caused by thin layers of dust on the camera lenses and dials, gnomon color chart, navigation maps, and LCRU mirror. The dust was easily brushed off, however, the dust was so prevalent that, during part of the mission the crew reported that, to set the lens, dust had to be wiped from the camera settings every time they took a picture.

The A-16 crew commented that the map holder on the LRV was worthless and got in the way. Instead, they wedged a map in between the camera and a staff. The maps did not reflect the topography very well. They also lost their navigation unit during the return of the 2nd EVA due to inadvertently hitting a protected switch. They got it back for the 3rd EVA.

One experiment, the SEP experiment, recorded navigational information from the LRV onto a tape recorder for analysis of its data. The navigation unit of the LRV was also used to orient the transmitting antennas of the SEP on A-17 and to align the geophones of the ASE on A-16 by leaving tracks along the proper direction.

On A-17, the crew got 7370 meters away from the LM on EVA 2, the furthest of any crew. The CDR commented that, because of the inability to travel on a straight line for very long periods of time, he primarily did not navigate on a heading. Rather, he navigated to points defined by bearing and range, those points being the planned jogs in the traverse, or for samples, or LSPE charge deploys, or stations. It worked well, and was why they never followed their tracks back to anywhere. Because of the low pressure exerted by the wheels on the soil, the average depth of the tracks was only ~1 1/4 cm, varying from near 0 to 5. On one occasion, because of its light weight, the LRV had a tendency to slide sideways down a rather steep slope as soon as the A-15 crew stepped off the vehicle. Maneuvering the vehicle on slopes did not present any serious problems. It was reported that the vehicle could be controlled more easily upslope than downslope; and, when the vehicle was traversing along slope contours, the wheels on the downslope side tended to dis-place to soil laterally and to sink more than the wheels on the upslope side. On A-17, the bouncing from craters at times caused a feeling of nearly overturning while traveling cross-slope, and the crew did reduce their speed somewhat as a result.

On A-16, the crew climbed slopes of up to 18deg in the LRV and thought that it was approaching its limit of slope-climbing ability. Tests on Earth predicted a maximum of 19deg to 23deg. In general, they had no serious operational problems on slopes.

Were there any hazards in the experiment?
i.e. hazardous materials (explosive, radioactive, toxic), sharp objects, high voltages, massive, bulky, tripping hazards, temperatures?
Dust kicked up by the wheels covered the astronauts, especially when the fender broke off. Both crewmen on A-17 commented that the restraint system on the LRV was inadequate, especially on slopes.

Was lighting a problem?
Driving down sun or into the sun was difficult due to visibility problems. The A-16 crew could go no faster than 4 or 5 kph and still ran right over some craters because they could not see them until they were on top of them. Boulders could be seen and avoided.

Were the results visible to the crew? NA

Would you recommend any design changes?
The seat belt design was changed for the later flights to account for the lower g. The restraint system design could be improved further, especially for driving on slopes. The A-15 crew recommended a bar, such as in a kiddie ride, which would lock in place to restrain the crew, or push out of the way easily. This had been considered but not accepted due to the weight penalty vs. seat belts. The time advantage vs. working the seat belts might be worth it, however. For A-17, fender extension stops were added based on the loss of the fender extension on A-16. The sighting device on the antenna could be improved by opening up the light passage through it to improve the visibility of Earth.

Were any special tools required? No.

Was the orientation of the experiment (i.e. horizontal/vertical) important? Difficult?
Driving on slopes left the "down-slope" crew member feeling precarious. The lunar communications relay unit (LCRU), a high gain antenna mounted on the LRV, had to be oriented at each station for television transmission to Earth. TV was cut off while moving, but voice communication was maintained over the low gain antenna. The low gain antenna for A-17 had to be aimed at Earth due to the location of this landing site. This was done by "dialing in" a reciprocal heading for antenna aiming from that being driven. The other sights were more sub-Earth and could use a vertically pointing antenna. Orientation of the high gain antenna was accomplished with an optical sighting device, but this presented a very dim image of Earth which was hampered by the helmet visor. The use of signal strength, as indicated on the AGC control meter, was an acceptable back-up alignment technique.

Was the experiment successful?
The LRV worked very well and extended the operable range of the crew on EVA.

Were there related experiments on other flights? NA

Where was it stored during flight? LM quadrant I.

Were there any problems photographing the experiment?
The television camera on the LRV was operable from Earth, allowing the ground to observe a "station" in panorama while the astronauts were doing field work. The camera which was to film the "grand prix" on EVA 2 of A-15 did not operate because the film magazine was faulty.

What pre-launch and cruise req'ts were there?
power, thermal, late access, early recovery?

What was different between training and actual EVA?
The Earth trainer had rubber tires and could support its own weight in 1 g. The flight article would have collapsed in 1 g if the crew sat on it. Since the handling characteristics of the LRV could not be fully tested on Earth, a "grand prix" test was performed by the CDR on A-15 & 16. The trainer provided adequate simulation, the major difference was the necessity to pay constant attention to the lunar terrain in order to have adequate warning of obstacles, especially in adverse lighting situations. Braking required ~2 x the 1 g distance. Steering was not as responsive between 8 - 10 kph with hard-over inputs.

What problems were due to the suit rather than the experiment?
The suit used for the last 3 flights was able to bend at the waist, allowing the astronaut to sit on the LRV. This also allowed them to kneel, which assisted some experiment deployment and sample collection.

Any experiences inside the LM of interest from the experiment/operations viewpoint? NA

References:

Mission Reports for Apollo 15, 16, and 17

Final Lunar Surface Procedures - Apollo 16, March 16, 1972, MSC

Final Lunar Surface Procedures - Apollo 17, November 6, 1972, MSC

Apollo Program Summary Report, section 4.8.2 Lunar Roving Vehicle, JCS-09423, April, 1975.

Apollo 15 Technical Crew Debriefing, 14 August 1971, in JSC History Office.

Apollo 16 Technical Crew Debriefing, 5 May 1972, in JSC History Office.

Apollo 17 Technical Crew Debriefing, 4 January 1973, in JSC History Office.

"Lunar Sourcebook - A User's Guide to the Moon" G. Heiken, D. Vaniman, and B. French, Eds., Cambridge University Press, Cambridge, 1991.

Personal communication from John Young, 1 April, 1993.

Personal communication from Jack Sevier, 18 May 1993.

Personal communication from Eric Jones, 3 August 1993.