148 votes
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Could we breathe an atmosphere that is not nitrogen based?

We can breathe pure oxygen for unlimited time if the pressure is not too high; about 0.4 bar is okay. Breathing pure oxygen at 1 bar is possible for some hours, but a longer time may damage the lungs. ...
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135 votes

Why did it take so long to notice that the ozone layer had holes in it? Which satellite provided the data?

I believe the discovery was made by orbiting satellite, but I'm not sure which one. That is not the case. Look at the author affiliation for the article to which you linked. The three authors of that ...
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  • 64.2k
122 votes
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What will be the effect if we stand on Jupiter?

(*) Jupiter, for all intents and purposes, doesn't have a solid surface to stand on. Not any more than you could say that Earth's atmosphere has it, before you hit Terra Firma. It's an enormous ball ...
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77 votes

Why is the breathing atmosphere of the ISS a standard atmosphere (at 1 atm containing nitrogen)?

Am I not considering something? Yes. You are not considering Mir, Soyuz, and the Space Shuttle. The International Space Station is a multinational program, jointly led by the US and Russia. While ...
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67 votes
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Why not increase contact surface when reentering the atmosphere?

I've done a lot of work on this subject with researchers and engineers at JPL, NASA Langley, and NASA Ames. There are some interesting things that come out of high-fidelity CFM (Computational Fluid ...
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64 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 ...
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53 votes
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Is it harder to enter an atmosphere perpendicular or at an angle

“Bouncing off the atmosphere” is a misleading turn of phrase. When returning to the Earth from the Moon, a spacecraft is on an elliptical orbit with the high end somewhere around the moon’s altitude ...
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44 votes
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What impact will the deorbiting of thousands of satellites have on the atmosphere?

Not much research has been done on this question in recent years, but some researchers are worried enough to research into wooden satellites. The question on the environmental impact of deorbiting ...
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41 votes
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How do we know what the atmospheric pressure on Mars is?

TFB's answer is correct that both Vikings made barometric measurements (and it is what the question asked for!), but it's worth noting that the atmosphere had been measured before surface instruments ...
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  • 7,406
38 votes
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Could the Moon keep an atmosphere?

It can keep an atmosphere, and in fact does. The atmosphere is something akin to a high grade Earth-based vacuum. But that's probably not what you are looking for. Okay, so what would happen with, ...
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  • 118k
33 votes

What impact will the deorbiting of thousands of satellites have on the atmosphere?

The mass of Earth's atmosphere is 5E+18 kg and the Troposphere alone has 3/4's of that. With an average height of 13 km that makes its volume $4 \pi r^2 h$ or about 6.6E+18 m^3. If we break up one ...
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  • 148k
32 votes

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

It's not the temperature that matters, it's the heat transfer. The density of the atmosphere up in the thermosphere is very very thin. There simply isn't nearly enough mass to transfer any ...
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  • 11.2k
31 votes

Are rockets faster than airplanes?

Rockets are much faster than airplanes for most of their flight. Here's a graph of a Space Shuttle launch: The red line is speed. It's in ft/s, 1000 ft/s is 1097 km/h. So At about 45 seconds, the ...
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  • 121k
30 votes
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Are there any known atmospheres that would support traditional combustion engines?

The short answer is no -- an internal combustion engine needs to pull oxygen from the air to operate, and no solid bodies in the solar system have that kind of atmosphere. Venus' atmosphere is ...
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29 votes

Why is the breathing atmosphere of the ISS a standard atmosphere (at 1 atm containing nitrogen)?

Rory mentions oxygenation rate which is an excellent point but there's additional reasons why not keep ISS atmosphere at a lower pressure - thermal convection and air cycling. Pressure at roughly one ...
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  • 75.5k
28 votes

Would the national flag planted by astronauts on Mars need an upper horizontal pole like the ones on the Moon?

Short answer: Yes. Mars is not windy enough to properly wave most flags. Long answer: In storm conditions, a flag constructed out of a very light material would be able to properly wave. If we take a ...
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27 votes

Is it more challenging to put an airship in the Uranian than in the Venusian atmosphere?

Buoyancy is a big problem. To stay aloft, the average density of the balloon envelope, lifting gas and gondola must be <= the density of the surrounding atmosphere. The pressure inside a balloon ...
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27 votes
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Why do some meteors explode in air?

The Chelyabinsk meteor was travelling at over 65,000 km/h when it hit the brunt of the atmosphere 23 km high in the air. This is 60 times the speed on sound! NASA estimates that the meteor's mass at ...
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27 votes

If someone built a vacuum tunnel through the atmosphere, could you have an orbit with a sea level perigee?

No, unless your structure is located directly on the equator and your satellite follows a perfectly circular orbit, atmospheric "orbits" aren't possible, even in a vacuum tunnel. Because the ...
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26 votes
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How could a hot lander enter Titan's atmosphere without setting its hydrocarbons ablaze?

In order for a combustion process to happen, you do not only need fuel, you also need an oxidizer. On Earth, that is usually the oxygen in the air. In Titan's atmosphere, there is no oxygen. This ...
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23 votes
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Maximum survivable atmospheric pressure

Based on saturation diving operations, it looks like the limits are as follows: Compressed air: Nitrogen narcosis limits you to around four times Earth's atmospheric pressure. Any gas mix: Hydreliox ...
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  • 11.5k
23 votes
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Bounce off the atmosphere at reentry?

Yes, a capsule cannot literally bounce off the atmosphere and its kinetic energy must be reduced by an encounter with the atmosphere, rather it would just pass through the atmosphere and back into ...
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  • 4,153
23 votes

In simple terms, how does the way space suits manage breathable gas differ from how scuba gear does it?

Intravehicular spacesuits are worn inside the cabin in case of emergencies, particularly during ascent and descent. The Mercury suits were manufactured by Goodrich. Nearly all other IV suits have ...
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  • 46.5k
22 votes
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Air in International Space Station

Several approaches are taken. Cargo vehicles bring up Oxygen and other atmospheric components (Nitrogen, etc). The Russian segments life support system works different and independant of the US side,...
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22 votes
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What concentration of oxygen in a planetary atmosphere would be indicative of life?

I would argue that no specific level of molecular or atomic oxygen in atmosphere is indicative of carbon-based life (i.e. life as we know it on Earth). A planet could have oxygen rich atmosphere which ...
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22 votes
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Is the "airship to orbit" mission profile feasible?

Nearly all balloons that have been constructed have been for flights from the surface to altitude. That requires a structure that can survive tethered at the surface in a range of wind speeds in high-...
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22 votes

Why does Titan have an atmosphere?

The mass of Titan is 1,345 · 1023 kg, but the mass of the Moon is 7,349 · 1022 kg. The gravity at the surface is 1,35 m/s² for Titan and 1,62 m/s² for the the Moon. But the surface temperatures are ...
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22 votes
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Self-sustainable Hermetically Sealed System: Humans & Plants

This is being done with biosphere 2 and several similar projects and found to be very complicated. Specifically in a small sealed system there is little buffering or inertia available if one element ...
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21 votes
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How strong and "hot" is the wind on the payload after the fairing is deployed at ~110km?

Launch vehicle operators (or at least the major ones) all seem to drop their fairings such that the heat produced by the remaining atmosphere remains below 1135 W/m$^2$. Not all the operators provide ...
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