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 ...
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  • 10.8k
117 votes

What can the KSP game actually teach about spaceflight and orbital mechanics, and what are its limitations?

In my former job I was writing educational software. In short, it's exactly what you described: we offered a paid version of what you could get for free by looking out on the internet, going to class,...
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  • 12.2k
98 votes

What can the KSP game actually teach about spaceflight and orbital mechanics, and what are its limitations?

In several press conferences, employees of NASA or private space firms have been asked if they played KSP, and some answered with "Yes". NASA used patched conics to find candidate orbits for ...
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  • 6,770
93 votes
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Would it be easier to put humans on Venus rather than Mars?

Technically, yes, it would be easier to put people on Venus. You need less of a kick for the interplanetary trip and slowing down is trivial with that dense atmosphere...one of the Pioneer Multiprobe ...
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89 votes

What led NASA et al. to decide the ISS should be a zero-g station when the massive negative health and quality of life impacts of zero-g were known?

Reliability. Any rotating station needs non-rotating components: solar panels need to face the Sun, radiators need to be shadowed, docking points need to be non-moving, and so on. Making a rotating ...
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  • 11.5k
86 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, ...
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  • 1,319
85 votes

Why are we trying to build a base on Mars before the Moon?

At the moment, there are a few groups trying to reach Mars, and a few groups who are trying to reach the Moon. Mars One has grabbed headlines lately, SpaceX states Mars colonization as its long term ...
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  • 20.8k
71 votes
Accepted

Why was this Saturn rocket elevated for launch?

Your picture is not of a Saturn V, it's of a Saturn IB. The purpose of the elevated platform (known as the "milkstool") is to lift the rocket up so that it can be launched from Pad 39B using the same ...
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  • 11.5k
70 votes
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Why did the Space Shuttle fly upside-down normally

The main reason is heat rejection. NASA was asked this very question, and the answer was identified. Basically, the waste heat from the shuttle is expelled via the cargo bay doors. You don't want to ...
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  • 118k
68 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 ...
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  • 46.5k
67 votes
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Why do ISS crew members often cross their arms?

It's about as standard procedure as crossing your legs when you're sitting. Arms in microgravity, without conscious effort to keep them by your body, will tend to extend the elbows to the sides - ...
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  • 52.6k
66 votes
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Why can't we use the same radiation shielding in Mars that we used when going to the moon?

Radiation exposure is a cumulative risk. The more radiation you receive, the more likely you are to develop cancers. The Apollo missions took no more than two weeks to complete; the astronauts ...
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66 votes

Why can't we use the same radiation shielding in Mars that we used when going to the moon?

In addition to what Russell Borogove says about cumulative risk you're operating under a false assumption--that there was shielding on the Apollo capsules. Not only did the Apollo capsules not have ...
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64 votes

Why do astronauts wear spacesuits during launch?

Are there failure modes that cause loss of pressure but not rapid, unplanned disassembly? Yes. The 3-man crew of Soyuz 11 died when a valve was jolted open, venting out all the cabin air supply. ...
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61 votes
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Why does the ascent stage of Apollo 11's lunar module look like it's made of paper?

Like everything else, the ascent and descent stages were built to be as light as possible. But because they knew they would operate only in a vacuum, many things really didn't need to be sturdy, nor ...
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  • 20.8k
61 votes

Why were the SpaceX Crew-1 astronauts backed up by guards with automatic weapons?

Why were the SpaceX Crew-1 astronauts backed up by guards with automatic weapons? A NASA crew launch is a highly-visible symbol of US national pride. I mean, the slogan for the whole campaign is ...
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58 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 ...
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  • 46.5k
57 votes

Why has the ISS not been left unmanned?

The ISS is a science laboratory -- a National Lab in fact. Leaving it uncrewed would take away a huge portion of the science productivity without substantially impacting the cost to operate it. Why ...
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  • 16.8k
57 votes
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Are all modern astronauts at least passable phlebotomists?

By my count, the OP asks three questions. I'll anecdotally answer two of them ("Is it something that most or all astronauts are capable of doing, or are there just a few "designated drivers&...
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  • 3,130
56 votes
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Why do they have a Snellen eye chart on the ISS?

Eyes do strange things in microgravity (when you consider they're deformable bags of fluid, this isn't too surprising). This report outlines the changes that can be identified after just a short ...
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  • 7,406
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 ...
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56 votes
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Why aren't spacecraft and spacesuits pressurised to 2.5 psi (17 kPa) of pure oxygen?

The sum of all partial pressures in the lungs must add up to the ambient pressure. The composition of gas inside the lungs includes the vapor pressure of H₂O at body temperature which is about 0.9 psi....
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  • 6,450
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 ...
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54 votes

Why do ISS crew members often cross their arms?

Offered as a supplement to @SF's answer: This shows the fully relaxed arm position obtained by a sleeping astronaut. From here
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54 votes

What led NASA et al. to decide the ISS should be a zero-g station when the massive negative health and quality of life impacts of zero-g were known?

I'll add one or two more items to Mark's excellent list. Stability - large rotating platforms (and they have to be large to produce useful artificial gravity) are subject to all sorts of precession. ...
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53 votes
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If the ISS had an emergency, how long would it take to get a rocket to it?

A brand new rocket to be launched will have to be assembled, and that's a long process, though I do not know how long. But if it's for an emergency, you may find ready rockets. After the Columbia ...
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  • 4,224
53 votes

After the Crew Dragon's success, does Boeing's Starliner still offer value?

Commercial Crew awarded two providers for dissimilar redundancy. This is exactly why NASA decided to select two partners in the commercial crew effort. Having dissimilar redundancy is key in NASA’s ...
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50 votes
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Can we write with chalk on blackboard in space?

There's no scientific reason against using a chalkboard, zero gravity isn't an impediment as making a mark is dependent on pressure between the chalk and the board. The reasons for not using chalk are ...
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  • 18.9k
49 votes

Would it be easier to put humans on Venus rather than Mars?

As others have already pointed out, getting humans to Venus would be marginally easier than getting them to Mars. Let's consider survival on Venus in a little more detail though. Although there haven'...
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49 votes

How did the Apollo guidance computers deal with radiation?

TL;DR: It was so busy getting stuff done, it didn't care. Being old, slow, massive and inefficient (by any modern standards, not by those in 1965) is a huge benefit when it comes to radiation hardness....
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  • 12.8k

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