37

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 hole. It takes a long time for hundreds of m3 to evacuate through a 2 mm hole.


29

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 cause a noticeable pressure drop. The ISS is not 100% leak-proof, so some small amount of air needs to be added on a regular basis to top it up. Further, the ...


20

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 through that hole. I used this calculator with a pressure gradient of 101kPa (ISS standard) and 0.1 kPa through a 2mm hole and got a water flow rate of ~0.1 cubic ...


18

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 vacuum, can't create a negative density, can only go from original to zero - and 1 bar of pressure is a pretty meager amount, when this kind of flows is involved. ...


18

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 minimum legal water pressure in the UK The behavior of air and water in detail is different but a first order approximation of fluid behavior VS hole size will ...


15

Interesting and non-trivial questions. Most propellants are not self-pressurized because as soon as the engines turn on the pressure would drop precipitously as the tanks quickly emptied and the propellant was unable to vaporize fast enough to keep up. LOX, RP, and H2 are the most common launch vehicle liquid propellants and none vaporize fast enough to ...


13

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 about 7,152 m (23,465 ft) deep and the pressure is 1.16 kPa (0.168 psi). The average surface pressure of Mars is 0.6 kPa (0.087 psi). The highest point, Olympus ...


13

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 if you shorten the nozzle (creating an underexpanded flow), there is greater pressure at the exit (good). But the exhaust speed $v_e$ is lower (bad). The $\...


12

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 the neck of the balloon with your fingers: Now relax the pressure on the neck of the balloon very slightly. You will find that the air leaks out of the ...


9

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 an answer: altitude (km) pressure (kPa) -7.15 1.16 0. 0.6 25. 0.03 $$P(h) = P_0 \exp\left( -\frac{h-h_0}{h_{...


8

The most basic answer is that pressure gives you velocity, and velocity gives you energy. A rocket engine becomes more efficient the faster the particles making up the thrust gases are leaving the rocket through the nozzle. Simple projectile physics: $$E = \dfrac{1}{2}mv^2$$ The energy of a mass, such as a stream of rocket exhaust (and, by Newton's ...


8

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 possible when the total pressure is not above 0.4 bar. See also my answer to the question How long were the Apollo astronauts allowed to breathe 100% oxygen at ...


7

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 from Apollo 13 onwards had a drink bag installed inside the suit which allowed them to drink when wearing the pressure suit on the Moon. Shepard and Mitchell ...


7

Given that you are using a liquid propellant you cannot rely on its own compressibility to achieve the required pressure. Liquids do not compress very well. This is especially true as you need a high pressure for your thruster and to make it worse: usually you do not want this pressure to change through the time of engine usage. Therefore, the common ...


6

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 nozzle of a rocket engine expands the exhaust stream, which both cools it and reduces its pressure. Ideally, for best performance, you want the exit pressure to ...


6

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 to disassemble itself in an uncontrolled manner, which could easily cause major damage to the crew capsule; descent and reentry is a little safer, but the forces ...


6

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 Configurations It has a negative effect on the thrust shown in this equation: $$Thrust = \dot{m}V_e +(p_e-p_0)A_e$$ if exit pressure ($p_e$) is less than ambient ($p_0$) the ...


6

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 Different vehicles have used stored onboard gas (typically helium) or autogenous propellants to provide this pressurization. Further reading: Why does the Falcon 9 ...


6

"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 "if" about this ==> "the pressure in the combustion chamber has to be exceeded by the pressure provided by the pumps" Addressing "is ...


5

Since the pressure in space is never completely zero i will need a value for the ambient pressure for moving on with the design. Looks like you only consider the Isp to get the area, and your model always gives bigger Isp with bigger area. As soon as you're interested in something else - mass of the nozzle, for example - or the model of the nozzle is ...


5

It's not really that the leak was slow, more that it took some time to manifest: Another source told the news agency the worker did not report the error and instead applied a sealant of some sort. After two months in orbit, the sealant apparently dried out, the source said, and was expelled by the cabin air pressure, opening up a leak. (The article is ...


5

(Partial answer) The LEM had ... ... four oxygen supplies : two, in the descent stage, provide oxygen during the descent and lunar- stay phases of the mission: two, in the ascent stage, during the ascent and rendezvous phases of the mission. The caution and warning limit values can tell us the range of pressures expected to be nominal. An ...


5

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. Which is why we have pump fed rocket engines. Question 1: Some equations from Ideal Rocket Theory: Specific Impulse is the equivalent velocity divided by ...


5

According to the Flight Manual, the Saturn V upper stage LOX tanks were maintained at 38-41 psi (2.6-2.8 bar). The first-stage LOX tanks were kept at lower pressure, 20-24 psi (1.4-1.7 bar). It appears those values may have varied slightly on different flights.


4

Probably it will not work. The problem is that gas molecules have a wide distribution of velocities; most molecules in a gas are not really close to the rms velocity. Over the course of billions of years we should expect faster molecules to escape. At some point all the molecules have become "faster" at one time or another and make a run for it. To ...


4

On most of Mars, the air pressure is ~600 Pa, which means any exposed ice will sublimate. You'd have to seal the ice in with a layer of another material. Also, if you were to evaporate ice to a pressure of 1 bar, you'd have an atmosphere consisting entirely of water vapor. You'd have continuous rain inside your cavern. The next question would be if humans ...


4

The ullage in the space shuttle external tank liquid oxygen tank was pressurized by ground-supplied helium to its flight pressure level of 20-22 psig (1.4 - 1.5 bar) at 2 minutes and 55 seconds before liftoff. Before that its vent/relief valve was open and the tank was approximately at ambient pressure. After liftoff ullage pressure was maintained at the ...


4

According to the Nuwa Concept Technical Report, the habitat atmosphere will be 30% oxygen by volume at 75kPa (~11 psi), with the balance being nitrogen, argon, and CO2. Agricultural modules will be kept at lower pressure with a CO2-rich mix.


3

Yes, the chamber pressure in a pressure-fed engine must be lower than the propellant supply pressure. For example, the space shuttle Orbital Maneuvering System engine operated at a chamber pressure of ~130 psi and was fed from tanks pressurized to ~250 psi. Another issue that is going to limit the thrust from that demonstration engine is that it doesn't ...


3

Sutton, 4th edition, page 288 gives: $\dot w = C_d A \sqrt {2g \rho \Delta p} $ so, trivial to arrange for $\Delta p $....but you have to get $C_d $ somehow. Sutton gives the following chart This is probably OK for estimation. Real-world it's probably first CFD and then measured experimentally.


Only top voted, non community-wiki answers of a minimum length are eligible