# Tag Info

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.

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 ...

19

As suggested by OrganicMarble in a comment, nitrogen is miscible with oxygen (you can thus make liquid air). According to NASA Technical Paper 2464, this is a major concern because using "enriched air" instead of pure oxygen as the oxidizer degrades the performance of the engine: The transfer of liquid oxygen (LOX) from a storage vessel to a rocket engine ...

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 ...

7

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_{...

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

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

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 ...

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

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 ...

4

(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 ...

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 ...

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.

3

Publications with atmospheric pressure data on Mars are rather scarce. This publication about seasonal cycles at Gale Crater shows the chart below with the atmospheric pressure ranges near the landing site of the Mars rover Curiosity. The width of the band is an indication of how the pressure varies throughout each sol. The seasonal ups and downs ...

2

This supposed to go in comments because it's not a complete answer but I got to put it here. I'm considering rocket scales based upon LEO payload. Micro - payload to LEO in few kgs, Small - payload to LEO in few hundreds of kgs. medium - payload to LEO in few tons. heavy - payload to LEO in few tens of tons. ultra heavy - payload to LEO in few hundreds of ...

2

From the Apollo Document NASA TN D-6724 APOLLO EXPERIENCE REPORT - LUNAR MODULE ENVIRONMENTAL CONTROL SUBSYSTEM a large descent-stage gaseous oxygen tank (approximately 48-pound capacity at 3000 psi) and two ascent-stage gaseous oxygen tanks (approximately 2.4-pound capacity each at 900 psi). A pressure regulator was used to reduce the high pressure ...

1

A spacesuit is designed to be strong in tension, not compression. Most parts of a space suit are soft. If you try to suck all the air out of a space suit at sea level, the suit will simply compress flat. Sea level air pressure is 14.7 pounds per square inch. So every square foot of space suit would have to hold back a force of 2000 lbs. You would need ...

1

The shuttle/ISS suit is protected from excessive crush loading by a negative pressure relief valve (NPRV). This valve opens when the outside pressure exceeds the inside pressure by a certain amount (the source does not give the value) and allows gas to flow into the suit. This could come into play during repressurization of the airlock. The following image ...

1

For a pressure fed engine, the propellants entering the combustion chamber are at a significantly lower pressure than the propellant tank pressure - otherwise they wouldn't flow the right way. You'd have to do something to increase the pressure of the fluid that was headed back up to the tank ullage, otherwise your pressurization line would flow the wrong ...

1

Unfortunately there is no simple equation to calculate the chamber pressure. One major complication is that the chamber temperature depends on the chemical reaction rate of the propellants, which is a function of the temperature, making it an iterative process. See How do you determine what the temperature will be in the combustion chamber of a rocket ...

1

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 ...

1

The thickness is set by MMOD protection requirements. Simplified calculation for the wall thickness required by the pressure vessel: $\sigma_\theta = \dfrac{Pr}{t}$ $\sigma$ = Young's modulus: 70 GPa p = pressure: 105 Pa r = radius: 2200 mm t = thickness $t = \dfrac{Pr}{\sigma_\theta}$ t = 0.003 mm which seems too low to me. Apply a safety factor ...

1

tl;dr: How could the 2018-08-30 Soyuz MS-09 / ISS leak be so slow? Answer: By being about 2 millimeters in diameter! @DavidHammen's comment converts 0.8 mbar/hr to about 0.8 m^/hr air loss rate presumably at standard conditions. Let's see how that's done, how it checks against "a 2mm hole" and what it means if there were no response of any kind (...

1

The wikipedia page has a engine mass value of 35 kg, but its not references anywhere, so I would take that value with a pinch of salt. Some aspects of an electric pump fed engine are discussed in the thesis below, and may answer some of your questions, but no information has been officially released and available on the public domain. https://www....

1

Usually the pump raises the kinetic head along with pressure head because injector needs a lot of injection speed also, so why not have them ready at the pump instead of converting later? The whole of LPRE is centered around the main combustion chamber hitting a certain pressure, and all of the plumbing, including the pumps, are tailored to hit that goal. ...

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