Stowage And Deployment Subsystem

Considerable thought, engineering and testing went into the development of the Lunar Roving Vehicle (LRV) Stowage and Deployment Subsystem. This subsystem design had to preclude premature deployment under the violent forces and loads that would be encountered during the Saturn V launch and potential hard LM landings on the Moon. A premature deployment inside the Saturn V or at LM landing could potentially have caused LRV and/or LM structural damage and proven disastrous. Yet the system also had to be ''astronaut (user) friendly'' to reliably facilitate easy deployment of the LRV once the LM was safely on the lunar surface and lunar exploration (astronaut egress and subsequent science gathering) had begun.

Boeing proposed, and NASA accepted, an automatic means of LRV deployment early in the LRV program. Early deployments of a zg gravity LRV simulator showed that the dynamics of rapid LRV automatic deployment using hinges, springs and latches was such that no single deployment of the LRV was repeatable. That made it unreliable. In November/December 1969, Boeing performed qualification testing of

Used Hops Picker Equipment
A fully-automatic deployment system was deemed too complex and NASA chose to go with a semi-automatic deployment system with the involvement of the astronauts. (NASA)

their automatic deployment system, during which the /6 gravity LRV simulator was deployed from a simulated LM in all extreme corners (eight positions) of the expected lunar deployment envelope. The Boeing automatic system successfully deployed the /6 gravity LRV in all these positions, but no single deployment from any of these Lunar Module positions could be repeated exactly.

Eugene Cowart had joined Boeing in 1956 and was one of the senior engineers on the LRV program. He was promoted to chief engineer for the LRV later in the program. He was present during a presentation of the proposed deployment system to MSFC Director Eberhard Rees.

"The deployment was a complicated proposition, because it had to deploy from the Lunar Module in various angles,'' Cowart remembered. "The original design had it coming out like a switchblade knife. When you pulled the lever the springs literally unwound. We had a big presentation to show that thing. Dr. Eberhardt Rees and others came over to see it in the Hick Building in Huntsville where the mockup was at the time. I remember someone pulled the lever, it made a hell of a noise and hung up halfway down. And I remember Rees saying, 'I don't think it will work like that!' And I said, 'Oh no, it's not going to work like that.' In any event, we changed that so it was lowered down.''

Due to the non-repeatability of the automatic deployment system, Dr. Eberhardt Rees, then Director of the Marshall Space Flight Center, instructed NASA's Structures and Propulsion Laboratory to assist Boeing in the qualification (design changes) of the automatic deployment system and also to design a 'backup' deployment system for the LRV in case the automatic system could not be qualified. MSFC structures and propulsion design personnel designed a semi-automatic LRV deployment system. The design consisted of adding a pulley on the end of a shaft with a worm gear to the existing Boeing-designed deployment system. This design meant that the LRV could be deployed under total astronaut control; i.e., the astronaut could stop the deployment at any point to assess the deployment process and make corrections to the hardware as required. The MSFC design was demonstrated to John Young and Charles Duke using a plywood wall and a 1/6 gravity LRV simulator. They pulled the deployment tapes and successfully lowered it to the floor. MSFC personnel also designed a tool for them to use to unlatch the wheel/chassis latch pins in case any of the pins got stuck during the deployment.

As ''users'', astronaut involvement was of crucial importance. They would be called upon to make sure the LRV was properly deployed and readied for its traverses on the Moon, so the easier it was for them to do this critical portion of the mission, the greater the likelihood of mission success. Engineering and Management discussions over the pros and cons of a fully automatic deployment versus a semiautomatic deployment emphasized the deployment repeatability of the semiautomatic system. The automatic system simply encountered too many chances for failure and this would effectively have scuttled the LRV mission. Astronauts John Young and Charles Duke were actively involved in many aspects of the LRV's design where it required astronaut interface.

''It seemed to me'' stated Charlie Duke, ''that crew involvement in the rover's deployment would be better and we would have better control with the semiautomatic deployment as opposed to no control of the deployment with the fully automatic system. So we helped the LRV design engineers do that.'' With astronaut concurrence and encouragement, the MSFC semi-automatic deployment design was selected.

The LRV was designed to be stowed in a very confined space (one of the four bays on the Lunar Module). This meant that the LRV had to be ''folded in on itself'' by having all four wheels in a ''tucked in'' position and then the forward and aft chassis, including the wheels, folded in over the center chassis. On the lunar surface, the LRV had to be safely lowered from the LM bay, the forward and aft chassis had to unfold and lock, and the four wheels had to ''un-tuck'' and latch before the LRV was in contact with the lunar surface. After contact, the LRV had to be disconnected from the LM/deployment system. Then, further LRV set-up could commence in preparation for the LRV mission. The goal was to have the LRV deployed in

Boeing technicians conduct electromagnetic compatibility tests on the Qualification Test

Unit at the Manned Spacecraft Center in Houston, Texas. (NASA)

Boeing technicians conduct electromagnetic compatibility tests on the Qualification Test

Unit at the Manned Spacecraft Center in Houston, Texas. (NASA)

fifteen minutes. It had to be able to deploy with the LM tilted as much as 14.5 degrees from its vertical axis in any direction, with the bottom of the descent stage anywhere from 35 cm to 160 cm above the lunar surface. The support and deployment system included lower support arms, with latches, cables, pulleys, pin retraction mechanisms, telescoping tubes, a push-off rod, and straps or deployment tapes. The deployment sequence began with the mission commander, (standing on the LM ladder) pulling a handle and releasing the three pins which secured the LRV to the LM. The spring-loaded push-off rod then moved the still-folded LRV away from the top of the LM storage bay by about 12 cm, where it was stopped by two steel cables and the main chassis rotation pins were latched into the lower support arms. The telescoping tubes provided mechanical support and control to ensure that the LRV was deployed clear of the LM. To prevent the LRV from inadvertently rolling under the LM, the telescoping tubes were ''one way'', having locking latches to preclude telescoping inwards.

The commander would then descend the ladder and would be joined by his crewmate. Together, they would deploy the LRV from the LM. One astronaut would pull on a nylon tape that would slowly lower the LRV to the lunar surface while the other astronaut would monitor the deployment and pull on his deployment cable attached to the LRV chassis, if required, to assist in the outward motion of the LRV from the LM. At roughly 45 degrees, release pins on the aft chassis automatically pulled. The aft chassis then deployed and the wheels and suspension unfolded and locked into position. At approximately 73 degrees, the center chassis would unlatch from the support arms and the forward chassis (attached to the telescoping tubes) would deploy and lock into position. The astronaut to the left of the LRV would then pull on that deployment tape, allowing the forward portion of the LRV to be lowered to the lunar surface. Then a lanyard would be pulled to release the telescoping tubes from the LRV. The astronauts could then move the LRV away from the LM and orient it for driving away. There were "barber pole'' indicators to verify that the chassis locking pins were fully engaged.

Many vibration and deployment tests were performed at Boeing and MSFC to ensure the system worked properly and reliably. Astronauts practised Lunar Rover deployments at Kennedy Space Center and at MSFC using the deployment trainer. The best justification for all this testing is the fact that there was never a failure of any LRV to deploy on the lunar surface, nor throughout its subsequent use to gather science and samples. All three LRV missions were a total success and the astronauts of these missions were elated with the use and performance of the vehicle.

On 6 April 1971, a final Lunar Roving Vehicle Design Certification Review presentation was made to MSFC management. As Boeing chief engineer for the LRV, Eugene Cowart spoke on the vehicle's design and systems, which took up the majority of the review. The initial requirements for the LRV were shown, along with the actual targets achieved. The required weight was 400 pounds (181.9 kg); actual weight was 493.81 pounds (223.9 kg). The operational capability of 78 hours was achieved. The required top speed was 16 kph; actual speed was 14 kph. The desired range was 120 kilometers; actual would be 92 kilometers. The target payload capability of 440 kilograms was exceeded; the LRV's actual payload capability was 482 kilograms. It met or exceeded the slope climbing and stability requirements, as well as the crevasse and obstacle negotiation parameters. Most impressive was the delivery of Flight Unit No. 1. It had a target date of 1 April 1971 for delivery to NASA; it arrived two weeks early, on 14 March 1971.

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