The Apollo Lunar Module was the lander portion of the Apollo spacecraft built for the US Apollo program to achieve the transit from moon orbit to the surface and back. The module was also known as the LM from the manufacturer designation (yet pronounced "LEM" from NASA's early name for it, Lunar Excursion Module).
The Lunar Roving Vehicle (LRV) or lunar rover was a type of surface exploration rover used on the Moon during the Apollo program. It is also known by its popular nickname of moon buggy. The rover enabled the Apollo astronauts to drive from the vicinity of their lander on the moon to make geological observations and collect rock and soil samples. Three of the Apollo missions brought LRVs to the Moon.
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The 6.65 m³ module was designed to carry a crew of two. The total module was 6.4 m high and 4.3 m across, resting on four legs. It consisted of two stages — the descent stage module and the ascent stage. The total mass of the module was 15,264 kg with the majority of that (10,334 kg) in the descent stage. Initially unpopular because the many delays in its development significantly stretched the projected timeline of the Apollo program, the LM eventually became the most reliable component of the Apollo/Saturn system, the only one never to suffer any failure that significantly impacted a mission, and in at least one instance (LM-7 Aquarius, see Apollo 13) greatly exceeded its original design requirements.
History: The Apollo Lunar Module came into being because NASA chose to reach the moon via a lunar orbit rendezvous (LOR) instead of a direct ascent or Earth orbit rendezvous (EOR) (see Choosing a mission mode for more information on the available rendezvous types). Both a direct ascent and an EOR would have involved the entire Apollo spacecraft landing on the moon; once the decision had been made to proceed using LOR, it became necessary to produce a separate craft capable of reaching the lunar surface.
The LM contract was given to Grumman Aircraft Engineering and a number of subcontractors. Grumman had begun lunar orbit rendezvous studies in late 1950s and again in 1962. In July 1962 eleven firms were invited to submit proposals for the LM. Nine did so in September, and Grumman was awarded the contract that same month. The contract cost was expected to be around $350 million. There were initially four major subcontractors — Bell Aerosystems (ascent engine), Hamilton Standard (environmental control systems), Marquardt (reaction control system) and Rocketdyne (descent engine).
The primary guidance, navigation and control system (PGNCS) on the LM was developed by the MIT Instrumentation Laboratory. The Apollo Guidance Computer was manufactured by Raytheon. A similar guidance system was used in the Command Module. A backup navigation tool, the Abort Guidance System (AGS), was developed by TRW.
To learn lunar landing techniques, astronauts practiced in the Lunar Landing Research Vehicle (LLRV), a flying vehicle that simulated the Lunar Module on earth. A 200-foot-tall, 400-foot-long gantry structure was constructed at NASA Langley Research Center; the LLRV was suspended in this structure from a crane, and "piloted" by moving the crane. (The facility is now known as the Impact Dynamics Research Facility, and is used for aircraft crash tests.)
The first LM flight was on January 22, 1968 when the unmanned LM-1 was launched on a Saturn IB for testing of propulsion systems in orbit. The next LM flight was aboard Apollo 9 using LM-3 on March 3, 1969 as a manned flight (McDivitt, Scott and Schweickart) to test a number of systems in Earth orbit including LM and CSM crew transit, LM propulsion, separation and docking. Apollo 10, launched on May 18, 1969, was another series of tests, this time in lunar orbit with the LM separating and descending to within 10 km of the surface. From the successful tests the LM successfully descended and ascended from the lunar surface with Apollo 11.
In April 1970, the lunar module Aquarius played an unexpected role in saving the lives of the three astronauts of the Apollo 13 mission (Commander James A. Lovell Jr., CSM pilot John L. Swigert Jr., and LM pilot Fred W. Haise Jr.), after an electrical short circuit caused an oxygen tank in that mission's service module to explode. Aquarius served as a refuge for the astronauts during their return to Earth, while its batteries were used to recharge the vital re-entry batteries of the command module that brought the astronauts through the Earth's atmosphere and to a safe splashdown on April 17, 1970. The LM's descent engine, designed to slow the vehicle during its descent to the moon, was used to accelerate the Apollo 13 spacecraft around the moon and back to Earth. After the accident, the LM's systems, designed to support two astronauts for 45 hours, were shown to have actually supported three astronauts for 90 hours.
The Lunar Modules for the final three Apollo Missions (Apollo 15, Apollo 16, and Apollo 17) were significantly upgraded to allow for greater landing payload weights and longer lunar surface stay times. The descent engine power was improved by the addition of a ten-inch extension to the engine nozzle, and the descent fuel tanks were increased in size. The most important cargo on these missions was the Lunar Roving Vehicle, which was stowed on Quadrant 1 of the LM Descent Stage and deployed by astronauts after landing. The upgraded capability of these so-called "J-Mission" LMs allowed three day stays on the moon.
Lunar Module specifications
The Lunar Module was the portion of the Apollo spacecraft that landed on the moon and returned to lunar orbit. It is divided into two major parts, the Descent Module and the Ascent Module.
The Descent Module contains the landing gear, landing radar antenna, descent rocket engine, and fuel to land on the moon. It also had several cargo compartments used to carry among other things, the Apollo Lunar Surface Experiment Packages ALSEP, Mobile Equipment Cart (a hand-pulled equipment cart used on Apollo 14), the Lunar Rover (moon car) used on Apollo 15, 16 and 17), surface television camera, surface tools and lunar sample collection boxes. It also carried the majority of the LM's battery power and oxygen, along with the single water tank needed to both cool the electronics and provide the astronauts with enough drinking water for a two- to three-day stay. Also, on the ladder of the descent stage is attached a plaque.
The Ascent Module contains the crew cabin, instrument panels, overhead hatch/docking port, forward hatch, reaction control system, radar and communications antennas, guidance and navigation systems (both a primary and a redundant backup system), thermal control system (an ice sublimator), ascent rocket engine and enough fuel, battery power, and breathing oxygen to return to lunar orbit and rendezvous with the Apollo Command and Service Modules. During ascent from the lunar surface, the lunar rock and soil samples were also carried in the Ascent Module, as much as 238 pounds on Apollo 17.
The Apollo LM Truck was a stand-alone LM descent stage intended to deliver up to five metric tons of payload to the Moon for an unmanned landing. This technique was intended to deliver equipment and supplies to a permanent manned lunar base that was never built. As originally proposed, it would be launched on a Saturn V with a full Apollo crew to accompany it to lunar orbit and then guide it to a landing next to the base; the base crew would then unload the "truck" while the orbiting crew returned to earth.
The development and construction of the lunar module is dramatized in the miniseries From the Earth to the Moon episode entitled "Spider" (a nickname for the LM).
The Lunar Roving Vehicle (LRV) or lunar rover was a type of surface exploration rover used on the Moon during the Apollo program. It is also known by its popular nickname of moon buggy. Three of the Apollo missions brought LRVs to the Moon.
History:The original cost-plus-incentive-fee contract to Boeing (with Delco as a major sub-contractor) was for 19M USD and called for delivery of the first LRV by April 1, 1971, but cost overruns led to a final cost of 38M USD. Four lunar rovers were built, one each for Apollo missions 15, 16, and 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 Apollo Lunar Module (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."
The LRVs did experience some minor problems, however. The rear fender extension on the Apollo 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 Apollo 17 LRV broke when accidentally bumped by Eugene Cernan with a hammer handle. The crew taped the extension back in place, but due to the dusty surfaces, the tape did not adhere and the extension was lost after about one hour of driving, causing the astronauts to be covered with dust. For the second EVA (extra-vehicular activity), a replacement "fender" was made with some EVA maps, duct tape, and a pair of clamps from inside the Lunar Module - nominally intended 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.
The colour television camera mounted on the front of the LRV could be remotely operated by Mission Control in two axis pans and zoom. This allowed far better television coverage of the EVA than the earlier missions. At the conclusion of the astronauts' stay on the surface the Commander drove the LRV to a position away from the Lunar Module so that the camera could record the ascent stage launch.
NASA's rovers have been abandoned and thus belong to the list of artificial objects on the Moon. Also on that list are the Soviet Union's unmanned rovers named Lunokhod 1 and Lunokhod 2.
Specifications: The Apollo Lunar Roving Vehicle 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.
Weight and payload: The Lunar Roving Vehicle had a weight of 463 lb (210 kg) and was designed to hold a payload of an additional 1,080 lb (490 kg) on the lunar surface. The frame was 10 feet (3 m) long with a wheelbase of 7.5 feet (2.3 m). The maximum height was 3.75 feet (1.1 m). 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 14 inches (35cm).
Wheels and power: The wheels consisted of a spun aluminum hub and a 32 inch diameter, 9 inch wide tire made of zinc coated woven 0.033 inch diameter steel strands attached to the rim and discs of formed aluminum. Titanium chevrons covered 50 percent of the contact area to provide traction. Inside the tire was a 25.5 inch 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 (200 W) motor capable of 10,000 rpm, attached to the wheel via an 80:1 harmonic drive, and a mechanical brake unit. Maneuvering capability was provided through the use of front and rear steering motors. Each series wound DC steering motor was capable of 0.1 hp (100 W). Both sets of wheels would turn in opposite directions, giving a steering radius of 10 feet (3 m), or could be decoupled so only one set would be used for steering. They could also free-wheel in case of drive failure. Power was provided by two 36-volt silver-zinc potassium hydroxide non-rechargeable batteries with a capacity of 121 A·h. 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.
Control and navigation: Lunar Rover diagram. (NASA)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.
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.
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