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303 votes
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How did the Apollo computers evaluate transcendental functions like sine, arctangent, log?

Since the Apollo 11 code is on GitHub, I was able to find the code that looks like an implementation of sine and cosine functions: see here for the command module and here for the lunar lander (it ...
supinf's user avatar
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198 votes
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Apollo image lighting

This is the Apollo 11 photo designated AS11-40-5925, a popular shot with moon landing deniers. The camera is facing generally north-north-west. The sun is low in the sky, about 10º-15º above the ...
Russell Borogove's user avatar
168 votes
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How did Apollo 16 capture this full photograph of the Moon's far side?

The photo (frame 3021) appears to have been taken from an approximate altitude of 1180 KM, on the return journey to Earth. We infer it was taken on the return journey as frame 3005 was taken after ...
Leorex's user avatar
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156 votes

If the astronauts on Apollo 11 had landed safely on the moon but could not take off, would there have been a rescue mission?

The following is a speech written for President Nixon, in the event that the Apollo 11 mission did not succeed. Fate has ordained that the men who went to the moon to explore in peace will stay on ...
Fred's user avatar
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107 votes
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Which Apollo "mystery" was said to be finally solved by a better rendering engine?

NVIDIA rendered Aldrin descending to the surface and discovered that, just as the conspiracies claimed, it couldn't be reproduced with direct light from the sun as the sole light source. Of course, as ...
Tom Goodfellow's user avatar
102 votes
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What was Apollo 13's "Little Jolt" after MECO?

The film gets this mostly right. Merely taking the thrust, and, therefore, the acceleration of the rocket down to zero wouldn't throw the astronauts forward; there are a couple of other effects at ...
Russell Borogove's user avatar
99 votes
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Why did some Apollo missions carry a grenade launcher?

They were part of an active seismic imaging experiment (archived version on wayback) By setting up a seismometer and setting off surface explosions of known size, you can get a lot of information ...
Russell Borogove's user avatar
88 votes
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Could "peak Apollo levels" of support have gotten NASA astronauts to Mars in the 1980's?

If you want to get really bummed out for 'what could have been', check out the Wikipedia page for List of manned Mars mission plans. The earliest plan to get to Mars was written by von Braun in 1948, ...
David Morris's user avatar
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81 votes
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How did the Lunar Module dock with the rest of Apollo 11 and what is the "CSM"?

The Apollo spacecraft consists of three major parts: The Command Module (CM), a conical module where the three crew members live during launch from Earth and travel to and from the moon, and which re-...
Russell Borogove's user avatar
80 votes
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What if Apollo Lunar Rover failed on the Moon?

The track for the Lunar Rover was planned not to exceed the maximum walking distance back to the LM. The astronauts could drive away from the LM to the maximum distance and then drive a circle around ...
Uwe's user avatar
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78 votes
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Did a flight controller ever answer Flight with a no-go?

One thing to note is that these polls of the room are largely for-the-record - in other words, if a flight controller was sitting on a problem that would prevent the accomplishment of a major ...
Organic Marble's user avatar
72 votes
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How did the Apollo Lunar Module ascent engine prevent gas bubbling through fuel?

The ascent engine was normally fired when the LM was sitting on the moon's surface, so the tankage was subjected to about 1/6 $g$, more than sufficient to separate the dense liquid fuel from the ...
Russell Borogove's user avatar
71 votes

How did NASA prevent third parties from spoofing Apollo communications?

The signal from the Moon was received using giant parabolic antennas, e.g. the 64-m dish at the Parkes observatory. These have very good sidelobe rejection so they won't pick up any Earthbound signals....
Hobbes's user avatar
  • 128k
71 votes

Was planting UN flag on Moon ever discussed?

No. Planting a flag was the idea of NASA's "Mr. Fix-It", Jack Kinzler, less than 4 months before Apollo 11's launch: Kinzler believed that the people of the United States would also want to see an ...
DrSheldon's user avatar
  • 48.1k
71 votes

How often is duct tape used during crewed space missions?

Gray tape was used during the Apollo missions, although only mentioned specifically by that name twice. The stowage manifests have several entries for tape. Although "duct tape" or "gray tape" is ...
DrSheldon's user avatar
  • 48.1k
69 votes
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How did NASA choose who descended in the LEM during the Apollo missions?

During the Apollo era, Deke Slayton, as chief of the astronaut office, was the primary decision maker when it came to choosing who was assigned to which crews. Slayton was chosen for the Mercury ...
Russell Borogove's user avatar
68 votes

How did Apollo missions solve the cosmic radiation problem?

While cosmic radiation is a problem, it's the same as with radiation on Earth: the risk is cumulative. The levels were low enough that missions of 1-2 weeks at this level did not pose a big health ...
Hobbes's user avatar
  • 128k
65 votes

Why didn’t the Spacecraft used for the Apollo 11 mission melt in the Earth’s Atmosphere?

Although the temperature at altitude can be several thousands of degrees, the atmosphere is so thin it does not transfer heat efficiently. Wikipedia explains it very well - The highly diluted gas ...
david_c's user avatar
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60 votes
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Did the Saturn V rocket have any purely aesthetic features that didn't serve an actual function?

I don't know of any features on the Saturn V that are solely aesthetic in purpose. The flags and USA markings come closest, but they are ostensibly there to identify the origin of the vehicle. The ...
Russell Borogove's user avatar
59 votes
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Did Apollo carry and use WD40?

It's hard to prove a negative, but the answer seems to be NO. It's not in D-7434 Stowage and the Support Team Concept, which has tables by location of the typical inventory stowed in the cabin. It's ...
DrSheldon's user avatar
  • 48.1k
58 votes
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Why is there a Saturn V in the background of this Gemini-Titan launch?

The photo is of the launch of Gemini 11 on September 12, 1966. The Saturn V in the background is SA-500F, a "Facilities Integration Vehicle". This was a nearly complete Saturn V that was ...
Russell Borogove's user avatar
56 votes

If the astronauts on Apollo 11 had landed safely on the moon but could not take off, would there have been a rescue mission?

The Apollo lunar module was battery powered, so could only maintain a livable environment for a few days (this was a major concern for Apollo 13, since the crew was reliant on the LM after the ...
Russell Borogove's user avatar
55 votes
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Could the Saturn V actually have launched astronauts around Venus?

It takes surprisingly little delta-v to reach Venus for a flyby -- about 3850 m/s from LEO instead of the 3200 m/s or so required to get to the moon -- so while the payload would have to be reduced ...
Russell Borogove's user avatar
55 votes
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Was "Apollo" an acronym for "America’s Program for Orbiting Lunar and Landing Operations"?

From a pre-launch press release for Apollo 11: Among the many missions conceived at that time was a manned journey to the Moon and back. Dr. Silverstein himself named it "Apollo" after one ...
PearsonArtPhoto's user avatar
  • 121k
55 votes

Apollo: what was the big deal?

There was no one breakthrough that made it possible. The "big deal", in the mind of the world, was just that an obviously very hard thing was accomplished. And, if you doubted how hard it ...
Mark Foskey's user avatar
  • 11.4k
54 votes

How did Apollo missions solve the cosmic radiation problem?

They didn't, which is why the Apollo astronauts saw blinding flashes inside their eyes during the mission and then had a much higher probability of suffering from cataracts later in life. The flashes ...
Robert Longson's user avatar
54 votes
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Apollo 14-17 - Why didn't they keep the Lunar Module docked as a lifeboat for the way back to Earth?

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 ...
Eugene Styer's user avatar
  • 1,852
53 votes
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Why did the Lunar Module have such an irregular shape? Didn't it add weight and complexity?

The reasons for the LM having the shape that it had is pretty well explained in Chariots For Apollo, in particular chapter 6. That chapter also has this picture of the evolution of the LM design: (...
Ludo's user avatar
  • 14.5k
52 votes

How often is duct tape used during crewed space missions?

When I was in shuttle Endeavour's cockpit in May 2008 (the Orbiter was in the Orbiter Processing Facility) I noticed this duct tape applied to the aft Multifunction Display Unit. (personal photo) Two ...
Organic Marble's user avatar
50 votes

How do we know the Apollo Moon landings are real?

As belief in conspiracy theories is associated with the rejection of science, it is likely that this answer will be rejected by many at the outset. If you doubt the reliability of science, perhaps you ...

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