30
votes
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The principle behind regenerative cooling?
You are missing how heat is distributed in exhaust.
Most of propellant ejected through the nozzle never makes contact with the nozzle surface or walls of the combustion chamber, and as result never ...
- 55.3k
27
votes
Why is the hot part of Webb's MIRI cryocooler in the 300K area?
It IS passively cooled, there is no other way to get rid of heat in space (except if you evaporate some coolant, which JWST tries not to do)...
So the cryocooler has a radiator attached to it to ...
- 3,765
23
votes
Why is an inflatable balloon inside a fuel tank not used to prevent fuel from "sloshing around"?
They do!
Many propellant tank, especially those required to work in zero-g environments, do use just such a bladder-inside-a-tank for the fuel. Typically monopropellants for thrusters.
It completely ...
21
votes
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What is the advantage of using Helium over Nitrogen when used for pressurising LOx?
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 "...
- 1,900
19
votes
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What's the difference between cryogenic and Liquid propellant?
Cryogenic propellants are a subset of liquid propellants1.
Cryogenic just refers to materials kept at very low temperatures. Cryogenic propellants are those such as hydrogen, oxygen, or methane, that ...
- 170k
18
votes
Falcon-9's subcooled LOX is continuously refrigerated in-situ, what about its subcooled RP-1?
RP-1 isn't cryogenic actually. The subcooling for RP-1 is only to cool it to slightly below the freezing point of water, 20 F. At that temperature, no extreme cooling is required. The temperature ...
- 122k
16
votes
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How does SpaceX plan to deal with boiloff on the trip to Mars?
This is a really good question and the answer is probably not 100% known, even by SpaceX at this moment.
No doubt they will have some active cooling to minimize boil off.
Structurally there are ...
- 80.2k
13
votes
Why can’t cryogenic propellants be storable, at least on the ground, via refrigeration?
I performed a feasibility study for a Soyuz launch site on Christmas Island many years ago in support of the Asian Pacific Space Center. One of their press releases talking about the project is here: ...
- 2,304
12
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How was the Centaur stage fueled in the Space Shuttle?
It was filled through the "T-0 umbilicals" (referring to the time of disconnect).
LO2 through an umbilical on the Orbiter boattail, LH2 through one in the midbody.
This schematic shows the plumbing ...
- 187k
12
votes
How are fuel tanks filled with cryogenic hydrogen?
The existing answers do not accurately describe the procedure for the Space Shuttle system (or, I believe, for Apollo, but I am not 100% sure of that - see note at end of answer). The propellant ...
- 187k
11
votes
How does SpaceX plan to deal with boiloff on the trip to Mars?
I think the most important factor in avoiding boiloff is not using hydrogen.
The atmospheric boiling points of the chosen propellants are as follows:
Substance
Boiling point
Oxygen
90 K (-183 °C, -...
- 2,868
11
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Accepted
Why do Ariane rockets not have ice break off on liftoff?
Ariane 5 does not shed ice at liftoff. The first stage is covered in foam insulation that prevents ice buildup.
In this image, the insulation is the brown stuff. Later Ariane 5 versions switched to ...
- 128k
11
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Why is the hot part of Webb's MIRI cryocooler in the 300K area?
Answer: the MIRI cryocooler CCA is located in JSWT Region 3 (the hottest part of JWST at 300K) because CCA’s two compressors and their electronics consume a lot of electricity and therefore generate ...
- 24.8k
10
votes
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How difficult is it to convert a hypergolic based Moon human lander to a cryogenic one?
There will likely be significant differences in the required tankage, if nothing else.
The paper Lunar Lander Conceptual Design shows a comparison between landers with similar payload requirements ...
- 187k
9
votes
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Has solidifying liquid propellant been considered for space exploration?
The melting point of hydrogen isn't much lower than its boiling point (6K), so the temperature isn't necessarily that much of an obstacle. However, using solid fuel requires either melting it, or ...
- 4,578
8
votes
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Propellant boil-off in zero G
Different stages use different means; Centaur uses(used) a thermodynamic vent mixer system for its LH2 tank.
This device served to keep the bulk propellant well mixed, and ensured that only gas was ...
- 187k
8
votes
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How will Robotic Refueling Mission-3's liquid methane tank remain full for six months without any boil off?
Image from the informative presentation Progress on the RRM3 Cryogen Demonstration System
The cryocoolers were commercial units, electrically powered Sunpower Cryotel CT 11 watt units. There is a ...
- 187k
8
votes
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ULA's ACES upper stage with IVF - Why are they using internal combustion engines?
What a fantastic question! I learned a lot researching this one.
The use of a simple piston-in-cylinder engine on an ultra high
performance in-space stage seems to be out of place in a technology
...
- 11.2k
7
votes
Does the NK-33 engine require subcooled kerosene so cold that it turns to wax?
There is no problem running Kerosene and Oxygen on the same turbopump shaft, at any temperature. provided both are liquid, the density variations are not sufficient to make any practical difference to ...
- 2,868
7
votes
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Filling the propellants in the rocket tanks
Short answer, they let some boil to keep the rest cool and also 'waste' some to cool the plumbing and tanks before loading.
The bulk cryogenics are made by compression, not cooling and from that ...
- 23.4k
7
votes
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How cryogenic oxygen was heated up for CM cabin repressurization?
Unsurprisingly, it worked exactly like it did in shuttle.
To assure uniform flow, the capillary restrictors are coiled around a
warm water-glycol line to increase the oxygen temperature.
Page 2....
- 187k
7
votes
In a rocket engine, do the propellants come out as liquid or gas if they’re cryogenic?
It's possible to inject in either state, but far more common to inject as liquid state so that one can design the oxidizer and fuel streams to intersect each other, creating a large splash fan where ...
- 2,304
7
votes
How difficult is it to convert a hypergolic based Moon human lander to a cryogenic one?
A lander with storable propellants needs to keep them at close to room temperature, for a minimum of several days. A hydrolox system will take up much more volume due to the low density of LH2, and ...
- 10.9k
7
votes
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Does a cryogenic liquid propellant engine exist capable of using multiple fuels?
The RL10 has been experimentally fired on methane and propane as well as hydrogen. This did entail modifications to several components of the engine; for the methane version:
Fuel component ...
- 170k
7
votes
What's the difference between cryogenic and Liquid propellant?
A cryogenic liquid is a very cold liquid. The term is now generally used for gases that cannot be liquefied by pressure alone at room temperature, or to put it another way gases that have critical ...
- 10.1k
5
votes
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Air-launching an Electron-like LOX-based rocket from a plane; technical challenges?
A mostly un referenced list would include:
Needing to design rocket structure to bear load horizontally pre launch as well as vertically under thrust. Classic rocket design supports the rocket ...
- 23.4k
5
votes
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ULA's plan for LH2/LOX 2nd stage that can maintain propellant for an extended period of time?
The ACES stage is designed for a lifetime of weeks, not years.
The tanks will be simply stacked on top of each other. There's no plan to place the LH tank inside the LOX tank.
ACES design is ...
- 128k
5
votes
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Liquid Helium (4.2K) sealed, then raised to sub-LOX temperature (~70K) - what is the new pressure?
We don't need to look into the phase diagram here, because it doesn't matter on which path we reach a certain end point. We can safely assume that we heat up the helium at constant pressure and then ...
- 15.1k
5
votes
Autogenous pressurization with sub-cooled propellant
Once the tanks are no longer full, there's no point in keeping the propellants subcooled. When you start the engines, you just have to control the rate at which the tank and propellant warm up, to ...
- 128k
5
votes
Accepted
What methods are proposed for storing cryogenic fuels (esp. hydrogen) in space for months or years?
NASA had a zero boil-off tank on the ISS for some time, but they haven't updated much of that page unfortunately. With CRS-16 they sent the third in a series of robotic missions to the ISS that is ...
- 623
Only top scored, non community-wiki answers of a minimum length are eligible