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57 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....
Woody's user avatar
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38 votes
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How could the 2018-08-30 Soyuz MS-09 / ISS leak be so slow?

The ISS is at 1 bar, i.e. 1 kgf/cm2, or 10 gramsf/mm2. So the pressure on that 2 mm hole is 31.4 gramsf, well within the range a human finger can handle. Also, the ISS is really big compared to the ...
Hobbes's user avatar
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38 votes

When staying indoors, can missing gravity be replaced with blowing air?

in a building or closed vehicle on another planet, maybe air pressure could be used to imitate gravity There is no need to imitate gravity on another planet, because planets have gravity. Of course, ...
Jörg W Mittag's user avatar
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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If there's a hole in Zvezda module, why didn't all the air onboard immediately escape into space?

It would take around 7 hours to depressurize the ISS through a bullet hole. See http://www.spaceacademy.net.au/flight/emg/spcdp.htm Smaller holes will take longer. A tiny crack might take days to even ...
Innovine's user avatar
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20 votes

How could the 2018-08-30 Soyuz MS-09 / ISS leak be so slow?

This is the image of the hole (news source, although the image is from NASA) The hole is 2mm in diameter. Even with a total vacuum on the other side, you're not talking a lot of volume getting ...
Machavity's user avatar
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18 votes
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Why does the Falcon 9 use turbopumps as well as helium pressurisation system?

Pumps are great at creating positive pressure, hundreds of bars. But with tank at ~1 bar, atmospheric pressure, they can only create a grand total of 1 bar of suction - can't go more vacuum than ...
SF.'s user avatar
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18 votes

If there's a hole in Zvezda module, why didn't all the air onboard immediately escape into space?

The pressure difference between the inside and outside of the ISS is one atmosphere. This is the same pressure difference between the bottom of a 10 meter tank of water and the outside at sea level or ...
GremlinWranger's user avatar
18 votes

Is a dome really the most efficient way to contain gas in a vacuum?

It all depends on the material. A dome/balloon is mechanically same thing as an arch, just loaded in the opposite way. The material of a balloon is all under tension, the material of a masonry arch is ...
TooTea's user avatar
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16 votes

When staying indoors, can missing gravity be replaced with blowing air?

While not strong enough to produce "artificial gravity" in a microgravity environment such as an orbital space station (eg ISS), it should still be noted that air circulation, and ...
Dragongeek's user avatar
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15 votes

What keeps the pressure stable inside the ISS?

Wikipedia has a good overview of the ISS's ECLSS. This paper also includes some details. In particular, the Atmosphere Control and Supply (ACS) The ACS subsystem provides cabin atmosphere pressure ...
0xDBFB7's user avatar
  • 2,249
14 votes

Why aren't spacecraft and spacesuits pressurised to 2.5 psi (17 kPa) of pure oxygen?

A mix of 79 % nitrogen and 21 % oxygen at a pressure of 1 atm, 14.7 psi or 1.01 bar is more fireproof than pure oxygen at a pressure of 0.21 atm, 3.087 psi or 0.212 bar. The partial pressure of oxygen ...
Uwe's user avatar
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13 votes

What is the deepest place on Mars? Do humans need pressurized suits there?

Is there any particular deep areas of Mars in which a person could survive with only an oxygen supply without a pressurized suit? No. Hellas Planitia is the lowest point on Mars, the basin floor is ...
Rob's user avatar
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13 votes
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why do under-expanded engines have less than ideal thrust?

The hard part is that $P_e$ isn't a completely independent variable. As the gas expands past the throat, thermal energy is being converted into kinetic energy. The gas cools down and speeds up. So ...
BowlOfRed's user avatar
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13 votes

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

Supplementary answer For your timeline, it's important to note that the pressure drop is not even remotely linear. The flow through the leak is large at first because the differential pressure is ...
Organic Marble's user avatar
12 votes

If there's a hole in Zvezda module, why didn't all the air onboard immediately escape into space?

It is easy to conduct simple home experiments, or even do them as thought experiments to determine the answer to this question. Think of a child's balloon. Inflate the balloon with air whilst holding ...
Brian Tompsett - 汤莱恩's user avatar
11 votes
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Do lower pressure pressure-fed rockets get more Delta-V?

First of all: great observation! This is indeed the reason why pressure fed rocket engines are limited in possible chamber pressure, the added weight from the tanks isn't worth it at a certain point. ...
Ruben's user avatar
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9 votes
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What is the deepest place on Mars? Do humans need pressurized suits there?

To Or how deep would one have to be in Mars not to need a pressurized suit? and starting with @Rob's values and Planetery-Science.org's scale height of about 10.8 km to at least roughly ballpark ...
uhoh's user avatar
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8 votes

What effects did the different air pressure and air composition in certain spacecraft have on astronauts?

The partial pressure of oxygen (ppO2) should be higher than about 0.16 bar and lower than about 0.4 to 0.5 bar for longer exposition of some days up to a week. So breathing pure oxygen for a week is ...
Uwe's user avatar
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7 votes
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How to drink water on Mars?

Nobody is going to drink the water on Mars directly. It has to be filtered first. On the Apollo spacesuits, food and drink was carried internally. The port was for emergencies only. The moonwalkers ...
Hobbes's user avatar
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7 votes
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Can exit pressure of nozzle be less than atmospheric pressure?

Sure! That's called "overexpansion" because the flow is expanded too much to match the ambient pressure. ME 239: Rocket Propulsion: Over- and Under-expanded Nozzles and Nozzle ...
Organic Marble's user avatar
7 votes

How is the pressure within the gas generator determined?

"If the pressure in the combustion chamber has to be exceeded by the pressure provided by the pumps, is it also exceeded by the pressure in the gas generator. " Just to be clear, there's no &...
Organic Marble's user avatar
7 votes

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

6.) If noise was occurring from any source, would it become more silent as time goes on... or just stop all together at some point? Yes it would become quieter for two reasons; as cabin pressure ...
uhoh's user avatar
  • 149k
6 votes

How does the chamber pressure affect the performance of a Rocket Engine?

Yes, it is absolutely true. On this graph you can see the ISPs (aka exhaust velocity) at different mixture ration and chamber pressure. The higher the pressure the higher the velocity and thus delta/...
Antzi's user avatar
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6 votes

Temperature and pressure of rocket exhaust

The temperature and pressure inside the engine's combustion chamber is very high -- in the ballpark of 3400º C and 100 atmospheres for the Falcon Heavy's Merlin engines. However, the bell-shaped ...
Russell Borogove's user avatar
6 votes
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Is the risk of depressurization greater in atmosphere than in orbit?

Ascent and descent are relatively dynamic. Large amounts of energy are being transformed and redistributed very rapidly and violently. On ascent in particular, there is the potential for the booster ...
Russell Borogove's user avatar
6 votes

Why does the Falcon 9 use turbopumps as well as helium pressurisation system?

In a turbopump feed system it is still necessary to pressurize the tanks slightly (10 to 50 lb/in2) in order to prevent pump cavitation. Rocket Propulsion Elements, Sutton, 4th edition, p. 223 ...
Organic Marble's user avatar
6 votes

Can propellant tanks in a pressure-feed rocket be pressurized by burning the propellant inside those same tanks? Recipe for Ka-BOOM?

You have a big problem with hydrolox or metholox--the combustion products condense out at far above the temperature of the liquid in the tank. Thus you get no pressure. Even with Aerozine/nitrogen ...
Loren Pechtel's user avatar
6 votes

Upper limit of human comfort in higher atmospheric pressures?

I can’t answer your question with a specific pressure, since symptoms depend on the individual, the rate of descent, time at depth and lifetime exposure to high pressure. Symptoms from high pressure ...
Woody's user avatar
  • 22.4k
6 votes

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

There was a famous incident in 1966 when an engineer named Jim LeBlanc was testing a space suit in a vacuum chamber and it lost pressure. The pressure loss was fairly rapid but not abrupt. His ...
Mark Foskey's user avatar
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