154 votes
Accepted

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. ...
Uwe's user avatar
  • 49k
138 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 ...
David Hammen's user avatar
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67 votes
Accepted

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 ...
Tom Spilker's user avatar
  • 18.3k
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
  • 953
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 ...
Russell Borogove's user avatar
47 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 ...
gerrit's user avatar
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42 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 ...
Andrew is gone's user avatar
39 votes
Accepted

Person falling from space

Your question is under-specified (you don't give the size or posture of your subject), so I'm assuming an average-sized woman falling in the classic face-down skydiver posture. I'm also modeling this ...
Mark's user avatar
  • 15.3k
34 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 ...
uhoh's user avatar
  • 149k
33 votes
Accepted

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. (You could, of course, carry ...
Russell Borogove's user avatar
33 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 ...
gerrit's user avatar
  • 11.6k
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 ...
Hobbes's user avatar
  • 128k
30 votes

What stages of distress occur to a person when there is a small hull breach in space?

To understand subjective symptoms of a hull breach, it is important to remember that respiratory drive (the sensation of shortness of breath) is driven by blood CO2 level, not blood O2 level. As long ...
Woody's user avatar
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29 votes
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How does Titan have hydrogen in its atmosphere?

How does Titan have Hydrogen in it's atmopshere? Hydrogen is a trace gas in Titan's atmosphere (0.099% per the wikipedia article on Titan's atmosphere). Titan's scant amount of hydrogen in its ...
David Hammen's user avatar
  • 74.8k
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 ...
Dragongeek's user avatar
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27 votes
Accepted

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 ...
SE - stop firing the good guys's user avatar
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 ...
Dragongeek's user avatar
  • 18.8k
24 votes
Accepted

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 ...
Blake Walsh's user avatar
  • 4,221
24 votes
Accepted

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 ...
awksp's user avatar
  • 1,079
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 ...
DrSheldon's user avatar
  • 48k
23 votes
Accepted

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 ...
GremlinWranger's user avatar
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 ...
Uwe's user avatar
  • 49k
21 votes
Accepted

When did planetary scientists realize Venus' surface pressure was almost 100x that on Earth? How did they find out?

The early Venera probe hulls were designed for an atmospheric pressure of 25 bar. Barometers were designed for 10 bar. This was in line with what was then assumed to be the surface conditions. At the ...
Hobbes's user avatar
  • 128k
21 votes

Are rockets faster than airplanes?

A rocket isn't automatically fast - a small firework rocket may be no faster than a car. The important point is that rockets carry their own oxidiser and aren't limited by the need to interact with ...
Robin Bennett's user avatar
21 votes
Accepted

Are there any short-term survivable locations in the solar system, outside of Earth?

As already commented by Fred, Venus is your best bet. Not at surface level – both temperature and pressure are way too high there – but at ca. 50 km elevation, where both are actually quite similar to ...
leftaroundabout's user avatar
20 votes

Could we breathe an atmosphere that is not nitrogen based?

Yes, we don't require nitrogen to breathe. For example, NASA astronauts used to use a pure oxygen environment. The complication with this environment was the risk of fire. For more information: Why ...
called2voyage's user avatar
  • 23.7k
20 votes
Accepted

Has the Earth's red atmosphere rim ever been photographed?

As discussed here, very few satellites have ever orbited at a higher altitude than the moon, making images from lunar orbiters our highest imagers of eclipses from orbit. In fact, in order to get a 1:...
Jack's user avatar
  • 9,976
19 votes
Accepted

How can an *increase* in atmospheric temperature cause an *increase* in the atmospheric mass density?

The key concept is that for a satellite at a fixed altitude, when the atmospheric temperatures below its altitude increase, atmospheric expansion pushes more atmosphere up above the satellite! At the ...
Tom Spilker's user avatar
  • 18.3k
19 votes

When did planetary scientists realize Venus' surface pressure was almost 100x that on Earth? How did they find out?

The determination that Venus has a hellish surface is a great example of scientific detective work and its close association with technological advances that allow better and better measurements. In ...
Tom Spilker's user avatar
  • 18.3k

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