124

According to LMA790-3-LM Apollo Operations Handbook: Lunar Module LM 10 and Subsequent Volume I, section 2.3.6: The landing gear must be deployed before descent engine firing. If not deployed, the landing gear would be in the path of the descent engine plume and would be damaged. The manual also mentions that the landing gear is deployed with explosive ...


76

All the lunar landings were performed with the sun low in the sky behind the LM, between 5º and 14º above the horizon at the landing site. This provided several advantages: The sun wouldn't be in the crew’s eyes during any portion of the descent (they’d start out oriented feet forward, lying on their backs looking upward, during the braking phase, and ...


52

Without the descent stage, you have a far less capable lifeboat. Looking at Wikipedia, the ascent stage had two batteries with a total capacity of 592 Amp-Hours (some of which would have been used in the ascent), while the descent stage had four batteries with a total of 1660 Amp-Hours (raised to 2075 Amp-Hours for Apollo 15-17). So most of the power that ...


43

After these 25 second would have ended, the LM still had enough fuel to ascend with both of its stages right back to the Service module. In other words, the LM was designed to be able to take off from the Moon surface with BOTH stages, even right after touching the surface, in case something would have gone wrong. Then, why using two stages which surely ...


42

Some pictures from Apollo 11 of the landing gear – struts, footpads and contact probes. Three Apollo 12 images: Two Apollo 14 footpad images: An Apollo 16 image: The two probes bend straight up on the left of the left and right footpad. I found no Apollo 17 images with visible contact probes. So yes, some contact probes did bend and stick out sideways. ...


41

These were the "1202" and "1201" program alarms, which were warning signals that the lunar module's computer was becoming overloaded. During Apollo 11's descent to the moon, the crew left the LM's rendezvous radar, which was used to find their way back to the command module, switched on in the "SLEW" mode, so it would be ready ...


41

A controller on Earth, Ed Fendell, manually operated the camera by radio control, knowing the time of liftoff and the ascent trajectory expected and referring to a time-and-angle chart without watching the video feed in real time! According to Fendell: Now, the way that worked was this. Harley Weyer, who worked for me, sat down and figured what the ...


38

It is correct that the probe on the forward footpad was omitted to avoid interfering with the ladder: The probe located on the forward landing gear was deleted because of a concern that the failed probe could interfere with crewmen descending the LM ladder. [p. 8] There was more than one probe for redundancy. In particular, there was no electrical ...


36

In addition to the "single-serving" mechanical features that Uwe's answer describes, the guidance programming for the LM's onboard computer doesn't support any ascent flight on the descent stage. In particular this means you'd have to go to the manual throttle mode, P67, to lift off, then switch back to P66 to land again. The switch to P66 would ...


34

The Lunar Module was designed for a single landing. The contact sensors under the footpads of the landing gear did bend and stick out sideways during a landing. They could not be reused for another landing. The contact sensors were needed to prevent stopping the engine too early. The distance between footpads and ground could not be seen through the LM ...


31

Most of the Apollo photo libraries have a few shots of the surface under the descent engine bell; I think A14 has some interesting ones: The disturbance of the soil is very subtle; compared with the surface further out, I see more 1-2cm-sized pebbles, suggesting that smaller particles have been blown away from under the engine. The lack of a massive blast ...


29

The Apollo LM had three independent propellant supplies: tankage in the descent stage usable by the descent engine, tankage in the ascent stage for the ascent engine, and in the ascent stage for the reaction control system (RCS) thrusters. Prior to the initiation of descent and landing, only the RCS would be used, and very little of it. During the ...


29

I'll ignore the thermal, radiation, and other considerations, and consider only the general performance characteristics of the LM. The nominal "fully automatic" descent profile for the Apollo LM required about 2080 m/s of delta-V, with a small amount of additional propellant budgeted for a manual approach and other contingencies. This is the ...


28

The command module was more spacious and comfortable. Below and behind the crew couches was a space called the "lower equipment bay", which was where, among other things, the personal hygiene equipment was; it afforded a small amount of privacy for bathroom duties. Crew could either sleep in their crew couch or in a sleeping bag attached underneath the ...


28

The primary purpose of every Apollo Moon landing mission was to land on the Moon. Once the vehicle had passed safety checks and had made the lunar orbit insertion burn, the next step was to separate the Lunar Module from the Command and Service Module. If these steps did not happen the mission would have been a deemed loss of mission failure. Aside: There's ...


27

Lets have a look into Apollo By The Numbers: There was a lot of unused fuel (Aerozin 50) and oxidizer (nitrogen tetroxide) remaining in the descent stage of the Apollo 13 LM, 55 %. No need to use the fuel in the ascent stage. The LM fuel was not used for a single burn, five burns were neccessary, the last about five hours before splash down. DPS– Descent ...


27

There were shock absorbing structures within the landing legs. If the primary shock absorbing strut would be maximally compressed by a hard landing, the lower end of the ladder would be directly above the foot pad. PRIMARY STRUT The upper end of the primary strut is attached to the outboard end of the outrigger; the lower end has a ball joint for the ...


26

Was the lunar module also used to perform a barbecue roll? Yes, although it took them a while to get there, according to the Apollo Flight Journal. Starting at about 7 and a half hours after the accident, the crew began rotating the spacecraft periodically 90 degrees at a time to approximate the effect of the passive thermal control roll: 063:24:52 Lousma: ...


25

Early conceptual designs suggested that two stages would save weight. Another issue came up that made a single-stage lander unreliable. Pressurizing the fuel and oxidizer tanks of the lunar module was a considerable engineering challenge. Because of the temperature changes that happen during launch and Earth orbit, the tanks were kept unpressurized until ...


25

If surviving lunar nights are difficult to ensure the survival of the electronics, say on lunar rovers, in the low temperatures, The temperature itself is not the primary reason. Lunar nights are difficult to survive because you have 14 days of darkness. If you want to design a solar-powered rover that can store enough energy to stay warm for 14 days, ...


22

From Status of the JWST Sunshield and Spacecraft found in @Antzi 's answer: Most of the electronics is on the "hot side" but there needs to be some conventional electronics on the cold side (beside the cooled IR sensor chips). Small thermal environments on the cold side are equipped with heaters to provide mini-environments at normal operating temperature ...


20

What happened: With just seven and a half minutes remaining before they were set to touch down on the moon, Armstrong and Aldrin reported a program alarm. "It's a 1202." The 1202 alarm indicated that the guidance computer was being overloaded with tasks. It was having trouble completing its work in the cycling time available. "We looked down at ...


19

Regardless of consumables, the main concern with the descent module was the RTG. Each Apollo LM carried a small nuclear device containing nearly 4 Kg of plutonium that was to be left on the moon, a compact nuclear generator that would power the experiments left on the moon for years. See PAGE 67 of the original press release at NASA The reentry of Apollo ...


19

There is a very nice Apollo 14 image, a combination of the two images 9254 and 9255: From the Apollo 14 lunar surface journal, see. Another Apollo 12 ALSJ image:


18

Can someone find the descent rate profile that Duke is referring to here? Did LMPs look at a cheat sheet during the descent, or would they memorize key altitude-versus-ROD reference points? I think what you are looking for is on page 11 of the Apollo 16 LM Timeline Book. This is the checklist used by the crew during landing. The numbers in the 200 ft box ...


18

The most familiar issue is that the Apollo 10 LM was still above its target weight by a couple of hundred pounds. A safe landing would have been physically possible, but not with the desired propellant margins. However, the lighter Apollo 11 LM had already been completed and delivered 4 months prior to the flight of Apollo 10 -- the production and assembly ...


17

Supplementary answer (these answers cover it well, but there are a few other things of interest): For anyone interested in the details of this issue, the book Sunburst and Luminary by Don Eyles has, I think the definitive treatment. Eyles was the LEM descent guidance software programmer! Eyles explains that the problem was actually found on the ground ...


17

Source: Me. I currently work as a systems engineer on JWST. JWST will operating from the 2nd Lagrange Point (aka L2), which is approximately 1.5 million km (or 930,000 miles) past the Earth in Sun-Earth line. This is approximately 4x the distance from the Earth to the Moon. This distance, in addition to its lissajous orbit, ensure it will not encounter ...


17

Landing and ascent accelerations were low - 1/3 to 1/2 gee typically. A restraint system was provided, but really more to hold the crew down to the floor, than to support them. Sources Physics of lunar launch Apollo experience report - descent propulsion system LM Handbook


17

"Could be flown" is a clear yes, "could be flown to a landing" is another story. Most of the points you are listing can be accomplished using the backup system in the LM, the Abort Guidance System (AGS). I'll be using the LM Apollo Operations Handbook Volume I as the main source for all your specific points. An attitude / attitude rate reference is ...


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