20 July 1969
102:42:08 Duke: Roger. Copy. (Pause) Eagle, Houston. You’re Go for landing. Over.
102:42:13 Armstrong (on-board): Okay. 3000 at 70.
102:42:17 Aldrin: Roger. Understand. Go for landing. 3000 feet.
102:42:19 Duke: Copy.
102:42:19 Aldrin: Program Alarm. (Pause) 1201
102:42:24 Armstrong: 1201. (Pause) (On-board) Okay, 2000 at 50.
102:42:25 Duke: Roger. 1201 alarm. (Pause) We’re Go. Same type. We’re Go.
102:42:31 Aldrin: 2000 feet. 2000 feet.
102:42:33 Armstrong: (On-board) (With some urgency in his voice, possibly as he sees West Crater) Give me an LPD (angle).
102:42:34 Aldrin: Into the AGS, 47 degrees.
102:42:35 Duke: Roger.
102:42:37 Armstrong (on-board): (Confirming Buzz’s LPD readout) 47. That’s not a bad looking area. (Garbled) Okay. (Pause) 1000 at 30 is good. What’s LPD?
102:42:41 Duke: Eagle, looking great. You’re Go. (Long Pause) Roger. 1202. We copy it.
102:43:01 Aldrin: 35 degrees. 35 degrees. 750. Coming down at 23 (feet per second).
102:43:07 Armstrong (on-board): Okay.
102:43:07 Aldrin: 700 feet, 21 (feet per second) down, 33 degrees.
102:43:10 Armstrong (on-board): Pretty rocky area.
102:43:11 Aldrin: 600 feet, down at 19.
102:43:15 Armstrong (on-board): I’m going to…
102:43:16 Aldrin: 540 feet, down at…(LPD angle is) 30. Down at 15. (Pause)
102:43:26 Aldrin: Okay, 400 feet, down at 9 (feet per second). 58 (feet per second) forward.
102:43:32 Armstrong (on-board): No problem.
102:43:33 Aldrin: 350 feet, down at 4.
102:43:35 Aldrin: 330, three and a half down. (Pause)
102:43:42 Aldrin: Okay, you’re pegged on horizontal velocity.
102:43:46 Aldrin: 300 feet (altitude), down 3 1/2 (feet per second), 47 (feet per second) forward. Slow it up.
102:43:52 Aldrin: 1 1/2 down. Ease her down. 270.
102:43:58 Armstrong: Okay, how’s the fuel?
102:44:00 Aldrin: Eight percent.
102:44:02 Armstrong (on-board): Okay. Here’s a…Looks like a good area here.
102:44:04 Aldrin: I got the shadow out there.
102:44:07 Aldrin: 250 (feet altitude), down at 2 1/2, 19 forward. (Pause)
102:44:13 Aldrin: Altitude-velocity lights.
102:44:16 Aldrin: 3 1/2 down, 220 feet, 13 forward. (Pause)
102:44:23 Aldrin: 11 forward. Coming down nicely.
102:44:25 Armstrong (on-board): Gonna be right over that crater.
102:44:24 Aldrin: 200 feet, 4 1/2 down.
102:44:26 Aldrin: 5 1/2 down.
102:44:29 Armstrong (on-board): I got a good spot (garbled).
102:44:31 Aldrin: 160 feet, 6 1/2 down.
102:44:33 Aldrin: 5 1/2 down, 9 forward. You’re looking good.
102:44:40 Aldrin: 120 feet.
102:44:45 Aldrin: 100 feet, 3 1/2 down, 9 forward. Five percent (fuel remaining). Quantity light.
102:44:54 Aldrin: Okay. 75 feet. And it’s looking good. Down a half, 6 forward.
102:45:02 Duke: 60 seconds (of fuel left before the ‘Bingo’ call).
102:45:04 Aldrin: (Velocity) light’s on.
102:45:08 Aldrin: 60 feet, down 2 1/2. (Pause) 2 forward. 2 forward. That’s good.
102:45:17 Aldrin: 40 feet, down 2 1/2. Picking up some dust.
102:45:21 Aldrin: 30 feet, 2 1/2 down. (Garbled) shadow.
102:45:25 Aldrin: 4 forward. 4 forward. Drifting to the right a little. 20 feet, down a half.
102:45:31 Duke: 30 seconds (until the ‘Bingo’ call).
102:45:32 Aldrin: Drifting forward just a little bit; that’s good. (Garbled) (Pause)
102:45:40 Aldrin: Contact Light.
102:45:43 Armstrong (on-board): Shutdown
102:45:44 Aldrin: Okay. Engine Stop.
102:45:45 Aldrin: ACA out of Detent.
102:45:46 Armstrong: Out of Detent. Auto.
102:45:47 Aldrin: Mode Control, both Auto. Descent Engine Command Override, Off. Engine Arm, Off. 413 is in.
102:45:57 Duke: We copy you down, Eagle.
102:45:58 Armstrong (on-board): Engine arm is off. (Pause) Houston, Tranquility Base here. The Eagle has landed.
102:46:06 Duke: (Momentarily tongue-tied) Roger, Twan…(correcting himself) Tranquility. We copy you on the ground. You got a bunch of guys about to turn blue. We’re breathing again. Thanks a lot. (Source: NASA Official Transcript)
It began life as a rough model constructed of paperclips and wood. It was the first true spaceship, designed for operations exclusively outside the Earth’s atmosphere. It had a 100% mission completion rate and on one flight, was the slender thread that brought three astronauts back safe to Earth. It was built by the legendary Grumman Ironworks at Bethpage New York. It was the Lunar Excursion Module (LEM) later known as just the Lunar Module or LM. And thirty-eight years ago today, it was the vehicle that put the first men on the Moon.
Early in the decision-making process of how to get to the moon, two concepts were being considered – direct ascent to the moon or Earth-Orbit Rendezvous (EOR). In the first case, the moon landing would be accomplished by a single vehicle, shedding stages along the way. This would have required enormous lift capability (the Nova rocket) for launch from Earth and still have considerable mass for the return launch from the Moon. Alternately, EOR would launch components into Earth orbit where they would be assembled into a single vehicle which again, would land on the Moon. Like direct ascent, it would also have a substantial mass to both safely land on the Moon and launch to return to Earth. A guerilla-approach by supporters of the Lunar Orbit Rendezvous (LOR) eventually gained acceptance. One Saturn V would launch a spacecraft that was composed of modular parts. A command module would remain in orbit around the moon, while a lunar module would descend to the moon and then return to dock with the command module while still in lunar orbit. In contrast with the other plans, LOR required only a small part of the spacecraft to land on the Moon, thereby minimizing the mass to be launched from the Moon’s surface for the return trip. Now it was just a matter of designing the lunar lander…
The LEM 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 LEM. 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).
Early configurations of the LEM included a forward docking port as it was believed the LEM crew would be active in docking with the Command /Service Module. Early designs included large curved windows. Configuration freeze did not start until April 1963 when the ascent and descent engine design was decided. In addition to Rocketdyne a parallel program for the descent engine was ordered from Space Technology Laboratories in July 1963, and by January 1965 the Rocketdyne contract was cancelled. As the program continued there were numerous redesigns to save weight (including "Operation Scrape"), improve safety, and fix problems. For example initially the module was to be powered by fuel cells, built by Pratt and Whitney but in March 1965 they were paid off in favor of an all battery design. The initial design had the LEM with three landing legs. Three legs, though the lightest configuration was the least stable if one of the legs were damaged during landing and the most stable, 5, was too heavy. The compromise was four landing legs. As features were dropped for weight consideration, the shape became more angular until it emerged as the LEM we all have come to know and love.
Despite these actions, lunar module costs had not leveled off by late spring. In-house cost control and forecasting had also begun to deteriorate, aggravating the problems already encountered. After a ten-day review, a review team reported its findings to company corporate officers and NASA officials with substantial recommendations on program management, costs, subcontractor control, and ground support equipment. To bring about the kind of cost forecasting and control that NASA wanted, Grumman adopted "work packages" – breaking the program down into manageable segments, with strict cost budgets, and assigning managers to ride herd on each package. By linking tasks to manpower, program managers could better judge and control work in progress. This approach was a real departure from the commodity-oriented approach used by Grumman until that time.
On top of the contracting difficulties, the LEM was running into technical and engineering difficulties with the navigation system, the rendezvous radar and the ascent engines. The former were the source of considerable weight gain and yielded questionable performance and reliability. The latter, however, was causing grave concern as test runs had shown tendencies to rough running and excessive nozzle erosion. The problem was eventually solved though by combining efforts by Rocketdyne and Bell into a new engine which subsequently ran exceptionally well. Other challenges were likewise overcome.
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. The next flight would be the most famous – Apollo 11.
July 19, 1969. Apollo 11 passes behind the Moon and fires its Service propulsion engine in order to enter lunar orbit. In the several orbits that followed, the crew got passing views of their landing site, the southern Sea of Tranquility about 20 km (12 mi) southwest of the crater Sabine D. The landing site was selected in part, because it had been characterized as relatively flat and smooth by the automated Ranger 8 and Surveyor 5 landers, as well as by Lunar Orbiter mapping spacecraft. It was therefore unlikely to present major landing or extra-vehicular activity (EVA) challenges.
The one of the two remaining flight article LMs is LM-2, found today in the Smithsonian:
Oh, and the Soviets also had their design:
but it went nowhere…
- Specifications: (Baseline LM)
- Ascent Stage:
- Crew: 2
- Crew cabin volume: 6.65 m³ (235 ft3)
- Height: 3.76 m (12.34 ft)
- Diameter: 4.2 m (13.78 ft)
- Mass including fuel: 4,670 kg (10,300 lb)
- Atmosphere: 100% oxygen at 33 kPa (4.8 lb/in2)
- Water: two 19.3 kg (42.5 lb) storage tanks
- Coolant: 11.3 kg (25 lb) of ethylene glycol/water solution
- RCS (Reaction Control System) Propellant mass: 287 kg (633 lb)
- RCS thrusters: 16 x 445 N; four quads
- RCS propellants: N2O4/UDMH
- RCS specific impulse: 2.84 kN·s/kg
- APS Propellant mass: 2,353 kg (5,187 lb)
- APS thrust: 15.6 kN (3,500 lbf)
- APS propellants: N2O4/Aerozine 50 (UDMH/N2H4)
- APS pressurant: 2 x 2.9 kg helium tanks at 21 MPa
- Engine specific impulse: 3.05 kN·s/kg
- Thrust-to-weight ratio: 0.34 (in Earth gravity – The thrust was less than the weight on Earth, but enough on the Moon)
- Ascent stage delta V: 2,220 m/s (7,280 ft/s)
- Batteries: 2 x 296 Ah silver-zinc batteries
- Power: 28 V DC, 115 V 400 Hz AC
- Descent Stage:
- Height: 3.2 m (10.5 ft)
- Diameter: 4.2 m (13.8 ft)
- Landing gear diameter: 9.4 m (30.8 ft)
- Mass including fuel: 10,334 kg (22,783 lb)
- Water: 1 x 151 kg storage tank
- Power: 2 x 296 Ah silver-zinc batteries (secondary system)
- Propellants mass: 8,165 kg (18,000 lb)
- DPS thrust: 45.04 kN (10,125 lbf), throttleable to 4.56 kN (1025 lbf)
- DPS propellants: N2O4/Aerozine 50 (UDMH/N2H4)
- DPS pressurant: 1 x 22 kg supercritical helium tank at 10.72 kPa.
- Engine specific impulse: 3050 N·s/kg
- Descent stage delta V: 2,470 m/s (8,100 ft/s)
- Batteries: 4 x 400 A·h silver-zinc batteries
- Ascent Stage:
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