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Questions tagged [pressure]

Pressure is the force applied perpendicular to the surface of an object per unit area over which that force is distributed.

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

It's pretty common to see some artist or even engineer come up with an idea of a lunar or Martian colony with a big ol' glass dome up top. And we seem to have been doing this since the 60's. But ...
4 votes
1 answer
74 views

Pressure Term in Rocket Thrust Equation

In the rocket thrust equation, as well as the thrust due to the mass flow rate of the exiting propellant, there is also an additional pressure term included. However I have noticed that this term is ...
10 votes
2 answers
714 views

Do lower pressure pressure-fed rockets get more Delta-V?

I was playing around with the math for getting a pressure-fed rocket to orbit and came across something that I haven't seen addressed anywhere. In a pressure-fed rocket, the chamber pressure of the ...
2 votes
1 answer
240 views

How to design a Blowdown or Pressure Regulated pressurization system for a spacecraft?

I am trying to develop a simple tool to size a pressurization system for a spacecraft using either a blowdown pressurization system (BD) or a pressure regulated (PR) pressurization system. Though I ...
0 votes
0 answers
60 views

Is the turbopump outlet pressure higher or lower than the combustion chamber pressure? [duplicate]

I always thought turbopump outlet pressure was higher, but when I asked chatGPT, it said the chamber pressure is higher in open cycle rocket engines. Now I am confused because how would that work if ...
3 votes
2 answers
424 views

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

Pressure-fed liquid fuel rocket engines use pressurized propellant tanks to deliver propellant to the combustion chamber, rather than pumps. This eliminates the mass, cost and complexity of the gas ...
18 votes
4 answers
4k views

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

I'm working on a short sci-fi game and I'm curious about how the effects of a hull breach in a confined area play out. For perspective, let's say a very confined space of 100 cubic feet of normal, ...
3 votes
1 answer
90 views

Aerostats in the outer solar system

Having read a lot lately about some preliminary studies of aerostat options on Venus and Earth (Semirigid gas bags filled with N2/O2 to allow for a dual breathable/lifting gas - sorry no source on ...
6 votes
1 answer
1k views

Upper limit of human comfort in higher atmospheric pressures?

At what atmospheric pressure, assuming an earth-like atmospheric composition, do humans start to feel uncomfortable? I am not asking for the max survivable pressure, but the point where long term ...
7 votes
3 answers
359 views

Can we dig for air pressure on Mars?

Digging 8km under the lowest point on Mars will get us Mount Everest conditions for air pressure. I was thinking of two ways of doing said title: Nuclear powered bulldozers working around the clock ...
14 votes
5 answers
4k views

Why do pump and pressure fed liquid engines need to operate at high pressures?

There is apparently some confusion as to why pump or pressure fed liquid rocket engines need to operate at high pressure to product significant thrust, based on the comments to this question about ...
1 vote
1 answer
232 views

How to find the average ambient pressure during rocket ascent?

I am trying to find the average ambient pressure that my rocket will flight through during its ascent to then determine the most optimum conditions in my combustion chamber and nozzle. I have ...
5 votes
1 answer
1k views

Can exit pressure of nozzle be less than atmospheric pressure?

This is kinda dumb question .I got 5psi pressure at outlet of the nozzle from open motor software. Is that possible because its less than atmospheric pressure 14.7 psi? Am i missing out something?
0 votes
0 answers
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Analytical representations for thrust in underexpanded flow (P_e>P_a) [duplicate]

I am familiar with the ideal thrust equation: $F=\dot{m}U_e +(P_e-P_a)A_e$ When $P_a$ is greater than $P_e$, you have thrust losses, and the equation accounts for that. When $P_a=P_e$, you achieve ...
10 votes
3 answers
5k views

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

As I was watching Ad Astra (Great movie, but where does the gravity come from?), I had the idea that in a building or closed vehicle in a low gravity location, maybe air pressure could be used to ...
6 votes
2 answers
2k views

Does chamber pressure have the same impact on ISP for different types of engines?

From this answer I understand that higher chamber pressure means higher ISP - but is this always the case for similar engines? For example: I noticed that a lot of upper-stage engines have pretty low ...
4 votes
3 answers
309 views

How to read this Cassini Main Engine Operating Box (oxidizer vs fuel tank pressures)?

The extremely cool NASA JPL video Triumph at Saturn (Part I) is really worth a watch and/or listen. At about 34:32 it covers the period just before SOI (Saturn ...
4 votes
1 answer
771 views

How is a desired chamber pressure achieved in a liquid rocket engine

Before everyone responds that this has been asked before, I have read through every relevant post I could find here and believe my question has not been clearly covered. I also understand that "...
1 vote
1 answer
56 views

Would pressure oscillations at the inlet of a liquid engine turbo-pump subside at the outlet, or would they get amplified?

Would pressure oscillations at the inlet of a liquid engine turbo-pump subside at the outlet, or would they get amplified? What are the factors that decides the change in the amplitude of pressure ...
24 votes
2 answers
6k views

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

Today 1 atm (101.3 kPa, 14.7 psi) with sea level composition is most commonly used on spacecraft to avoid fire hazards like in Apollo 1 (not that it would have helped the Apollo 1 crew as they couldn'...
7 votes
1 answer
3k views

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

I am under the assumption that higher chamber pressure results in increase in exhaust velocity. Is this true?
11 votes
1 answer
3k views

What keeps the pressure stable inside the ISS?

I'm doing research on life support systems for the design of a Martian scientific base, and I'm having trouble finding information about the specifics racks that keep pressure stable inside the ISS. I ...
4 votes
1 answer
136 views

What is the planned Nuwa city atmosphere?

Nuwa is a proposal for a large-scale permanent Martian settlement. What is the planned atmospheric composition of Nuwa city's air? Will it be 15psi Oxygen/nitrogen, and trace gases or low partial ...
3 votes
0 answers
273 views

What is the inlet and outlet pressure of Merlin LOX/RP-1 turbopump?

I got the inlet and outlet pressure of Saturn V engines turbopumps here, but I couldn't find the turbopump pressure of the Merlin engine of Falcon 9.
4 votes
0 answers
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What equation is being used- chamber pressure v.s. mass flow rate? (Cold-gas thruster)

I am doing a project on cold gas thrusters and have seen a couple of graphs relating chamber pressure against mass flow rate. I can't seem to find the equation that relates these two parameters to ...
0 votes
0 answers
71 views

Pressurant gas line design considerations

I am trying to understand the constraints on pressurant gas line sizes and lengths. For a static volume, the lines can be small in diameter because there is no significant flow velocity and therefore ...
4 votes
1 answer
193 views

Is there a relation between combustion instabilities and chamber pressure?

Is there a relation between the combustion chamber pressure, and either an increase or decrease in both high and/or low frequency combustion instabilities. If so, how has this influenced engine design,...
5 votes
1 answer
497 views

How is the pressure within the gas generator determined?

The fact that pressure fed engines need their tanks to be at an even higher pressure has always confused me a little, but it's got me thinking; does the same logic apply to gas generator engines. If ...
5 votes
0 answers
192 views

Low-pressure pump-fed rocket engine?

I saw the above suggested in LEO on the Cheap. In P.130 it says: A compromise between high-performance/lightweight pump-fed vehicle designs and cost-optimized pressure-fed vehicles with heavier ...
12 votes
4 answers
10k views

Why do pressure-fed systems have to be pressurized with helium or nitrogen?

This is something I just don't understand. The way I see it, propellant can be pressurized all on its own in the tank. Just pump a lot of the stuff in there and make sure the tank is strong enough. ...
1 vote
0 answers
193 views

what is the ISP loss associated with pressure fed engines

Numerically, what is the approximate loss of overall system specific impulse associated with pressure-fed rocket engines, not only as a result of the low chamber pressure but also of the additional ...
2 votes
1 answer
580 views

Chamber pressure of a gas pressure fed liquid rocket motor

I am studying rocketry and am currently learning about pump fed vs gas pressure fed propulsion systems. Upon reading about gas pressure systems, I googled the formula to find the chamber pressure for ...
5 votes
1 answer
605 views

How do pressure fed and pump fed systems compare at different scale of rockets

Rocket Design is all about optimising mass, within cost constraints while accepting a certain amount of risk. Both pressure fed and pump fed systems have their pros and cons, but how do they compare ...
1 vote
1 answer
1k views

How to drink water on Mars?

There are craters filled with water on Mars as shown below. If fresh water is found, how would astronauts drink the water? Can the Apollo a spacesuit food/drink port be used to equalize the pressure ...
2 votes
2 answers
2k views

Pressure levels inside rocket liquid oxygen tanks?

What is the pressure levels inside rocket liquid oxygen tanks, at launch time? The question is for the minimum and maximum (known) levels of pressure inside such tanks. I am asking for any rocket ...
1 vote
1 answer
2k views

How does one determine the optimal CH4:O2 ratio in a methane-LOX rocket engine?

The SpaceX Raptor uses a 78:22 O2:CH4 ratio. It also has combustion chamber pressures higher than any other rocket engine ever built. My questions are: What's the math / chemistry that determines ...
10 votes
3 answers
4k views

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

The ISS is leaking through a hole in the Zvezda module that still hasn't been found. However, as with all pressurized chambers, shouldn't all air instantly run out through the hole into the vacuum of ...
3 votes
0 answers
228 views

How strong is the Starship bottom bulkhead?

I am wondering how much of a role does the pressurization of the propelant tanks play in making them withstand the engine thrust. What I am getting at is how much would the pressure offset or balance ...
7 votes
2 answers
2k views

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

Falcon 9 first stage use turbopumps as well as helium pressurisation system. Isn't the turbopumps enough to pump in the propellants to the combustion chamber?
3 votes
0 answers
261 views

Merlin combustion chamber pressure

What is the combustion chamber pressure for Merlin? I mean the average and the maximum The Raptor engine was tested with a maximum 330 bar. I would like to compare them
2 votes
0 answers
212 views

Design of propellant tanks of a rocket [duplicate]

I understand that the propellants (e.g. LOX & LH2) are stored in a rocket tank which is pressurized by Helium or a neutral gas, so as to push the propellants towards the tank outlet, to the turbo-...
4 votes
2 answers
4k views

ISS Destiny Module inner wall: thickness set by internal atmospheric pressure or by mass density needed for meteor shielding?

In their 2006 paper Christiansen et al. describe the "stuffed Whipple shield" wall of the ISS's Destiny Module. The outer skin, the Whipple shield's "bumper" layer, is a thin layer of aluminum (alloy ...
10 votes
1 answer
1k views

why do under-expanded engines have less than ideal thrust?

I've been looking into rocket propulsion a bit and got stumped on something. I read that the thrust generated by an engine can be determined by the following: $$ F = \frac{w}{g}v_{e}+A_{e}(P_{e}-P_{a})...
1 vote
2 answers
267 views

Can we create a vacuum inside an EVA suit when the outside is pressurized, will it implode?

EVA suits are specially designed spacecrafts for astronauts during spacewalks. I can say for sure, it can handle the following cases of pressurization of the system: Pressurized inside, but vacuum ...
2 votes
1 answer
1k views

Nozzle Exit Pressure Too High?

I've been doing some simple rocket science for fun, and I wanted to calculate the specifications of the Lunar Module Descent Engine (LMDE). The LMDE uses Aerozine-50 (UDMH) and Dinitrogen Tetroxide($...
0 votes
0 answers
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Rocket Combustion

How is the chamber pressure is arrived at for a given combustion temperature and mixture ratio ? Based on the mixture ratio, the value of gamma and temperature can be found out, using chemical ...
6 votes
1 answer
481 views

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

The Mercury and Gemini spacecraft, and in space the Apollo spacecraft, didn't pressurize their cockpits to 1 atm with Earth-like atmospheric composition; instead, they used pure oxygen at much lower ...
2 votes
1 answer
1k views

How can I calculate the density of Mars' atmosphere during dust storms?

I have been searching to try to estimate the air density of the atmosphere on Mars during a dust storm. I am trying to use this dynamic pressure equation to calculate the pressure on a theoretical ...
1 vote
1 answer
96 views

Pressure queries on turbopumps

In the turbopump used in liquid rockets, the stagnation pressure rise is definite. But then the question comes: Whether static pressure rises or dynamic pressure rises or both rise? If both rise ...
3 votes
2 answers
421 views

What was pressure and temperature of LM oxygen tanks?

After analysing comments in related question How cryogenic oxygen was heated up for CM cabin repressurization? It appears that LM had oxygen stored as either gas or supercritical fluid but not at ...