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90 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 ...
Mark's user avatar
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60 votes

Why are all space initiatives designed to get to space overnight when in Nature all extreme feats are achieved in a gradual process

Imagine you have a very heavy book and a bookcase, and your goal is to put the book on the top shelf of the bookcase. How much time would you spend doing that? Maybe five seconds, maybe fifteen. Would ...
Magma's user avatar
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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
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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. ...
Carl Witthoft's user avatar
52 votes

What would be the (most difficult) challenge to make a 10,000 year satellite?

LAGEOS satellites This has, in a way, already been done, with the Laser Geodynamics Satellite (LAGEOS) satellites. LAGEOS satellites, (the second of which was launched from the shuttle on mission ...
Organic Marble's user avatar
43 votes
Accepted

Why isn't there research to build a standard lunar, or Martian mobility platform?

NASA have deployed 4 rovers to Mars, and are working on the fifth. ESA is working on nr. 6. Sojourner: tiny, limited. Spirit and Opportunity (MER): much larger than Sojourner. No reuse possible. ...
Hobbes's user avatar
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42 votes
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Why is SpaceX building the Big Falcon Ship before the Big Falcon Rocket?

Neither has much financial purpose without the other. A BFR cannot perform any useful function without an upper stage, and that is the BFS. Since the whole platform is a major investment in a new ...
Saiboogu's user avatar
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41 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?

It's a good question, followed by many relevant responses so far. I'll focus on the physiology aspects. Research had been conducted for decades prior to ISS launch on creating artificial gravity ...
rugged orb's user avatar
32 votes

Why is SpaceX building the Big Falcon Ship before the Big Falcon Rocket?

Elon Musk stated in a news conference after the Falcon Heavy launch that the BFS will be the focus because they think they understand designing booster rockets pretty well, and thus they decided to ...
PearsonArtPhoto's user avatar
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32 votes

Why does the heatshield have to be on the outside?

To answer the title: Why does the heatshield have to be on the outside? Because most materials commonly used in spacecraft construction melt at the temperatures encountered during reentry. And most ...
Hobbes's user avatar
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31 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?

There was a proposal to add an experimental rotating habitat: Nautilus-X. One of those wonderfully tortured backronyms: Non-Atmospheric Universal Transport Intended for Lengthy United States ...
Schwern's user avatar
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31 votes

How realistic is the 1 kg/km² solar sail in "Death's End"?

A solar sail with an areal density of $1~\mathrm{kg}/\mathrm{km}^2 = 1~\mathrm{mg}/\mathrm{m}^2 =0.001~\mathrm{g}/\mathrm{m}^2$ is impossible by known materials science because graphene has an areal ...
WaterMolecule's user avatar
30 votes

Apollo: what was the big deal?

what has ALWAYS impressed the heck out of me is the sheer magnitude of scale involved... not physical size (although its size was truly impressive) but rather the huge number of complex problems that ...
BradV's user avatar
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26 votes
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How realistic would the Sea Dragon engine be to produce given today's technology?

Has any research into actually producing anything larger than the F1 been seriously carried out? The M-1 was a hydrogen engine just a little larger than the F-1. Parts of it were built and tested and ...
Russell Borogove's user avatar
24 votes

What would be the (most difficult) challenge to make a 10,000 year satellite?

The problems would be many to transmit a radio signal for 10,000 years. However there is nothing about a 10,000 year lifetime that would violate physics. It would just be extremely difficult ...
Mark Adler's user avatar
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23 votes
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Overcoming the speed of light thanks to ion thrusters

The expression $v_e = \sqrt{\frac{2Vq}{m}}$ is a non-relativistic approximation. This is quite valid when the exhaust velocity is small compared to the speed of light, which is the case for ion ...
David Hammen's user avatar
22 votes

What would be the (most difficult) challenge to make a 10,000 year satellite?

To complement, not attempt to replace, the other answers, I would like to propose a difficulty I see nobody having mentioned so far, but which could potentially be very problematic over such long time ...
user's user avatar
  • 7,330
21 votes

Apollo: what was the big deal?

It was fractally hard. Everything they did was Voltroning hard problems together to solve other hard problems. And this was all done in a coordinated way on an incredibly tight timescale. The long ...
fectin's user avatar
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20 votes
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How does the Saturn V Dynamic Test Stand work?

I can answer the Shuttle part. The test in question was the Mated Vertical Ground Vibration Test (MVGVT). Here's how the stack looked in the test stand. Five configurations were tested Liftoff ...
Organic Marble's user avatar
20 votes
Accepted

How hot do rocket engine nozzles get?

Direct measurement is difficult; I've seen some optical methods used but can't put a hand on them at the moment. Here are some calculated inner and outer wall temperatures for the Space Shuttle Main ...
Organic Marble's user avatar
20 votes

How realistic is the 1 kg/km² solar sail in "Death's End"?

There is a extensive summary report on possible improvements of solar sail materials: "Ultra-Thin Solar Sails for Interstellar Travel - Phase I Final Report" December 1999, Dean Spieth, Dr. ...
asdfex's user avatar
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17 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?

O'Neil cylinders have a very large minimum radius of several kilometers for a reason, or several reasons in fact. One can't just spin up a small station to simulate gravity and expect a person to be ...
DKNguyen's user avatar
  • 369
17 votes

Apollo: what was the big deal?

Additionally, while computers did exist, there was no Finite Element Analysis or modelling software. A lot of the engineering was done on slide rules, intuition, iterative testing, and ultimately ...
Criggie's user avatar
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16 votes
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How does a space probe differ from a satellite in terms of materials used and size?

The big difference is in weight. Satellites in Earth orbit can be much heavier than deep space probes, simply because it takes a lot of energy to launch something into an Earth-escape trajectory. ...
Hobbes's user avatar
  • 128k
16 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?

The other answers are good, but I think we miss something. Imagine a spacewalk around a rotating space station. With the current technology, we do need regular spacewalks. Everything dropped doesn't ...
fraxinus's user avatar
  • 2,519
16 votes

Why does the heatshield have to be on the outside?

To answer some other aspects: In the case of Starship, is the existing steel strong enough (to be non-ablative!), or would a different type of material be necessary? The melting point of most steel ...
ikrase's user avatar
  • 8,873
15 votes

What would be the (most difficult) challenge to make a 10,000 year satellite?

The biggest challenges are going to be what people have already mentioned - the funding (don't skirt over that comment, you did ask for the challenges), an energy source for 10,000 years, and how to ...
Andy's user avatar
  • 5,178
15 votes

Why do pressure fed engines have combustion instabilities?

The issue with Sea Dragon and pressure instability is that the likelihood of pressure instability increases exponentially as the size of the combustion chamber and nozzle diameter increases linearly. ...
Israel Walker's user avatar
15 votes

Are and should satellites use wireless communication internally, rather than cables?

Radio may reduce some complexity, but it will introduce problems that wiring doesn't have. Limited bandwidth. Interference. You can separate wiring so it doesn't influence each other. Can't do ...
Hobbes's user avatar
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15 votes
Accepted

Why is Electron painted in black?

It's not painted black. It just happens to be that color. Omitting paint saves weight. On 2017 May 24, Rocketlab itself tweeted: Why a black rocket? Carbon composite materials are black! Paint is ...
Camille Goudeseune's user avatar

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