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40

As Organic Marble hints, there is about 140 degrees Celsius between kerosene's freezing point and oxygen's boiling point; there's no temperature at which both are liquid. Even if the propellants were more thermally compatible, putting your fuel and oxidizer in the same tank is a really dangerous idea. Typically, propellant tanks are pressurized with helium ...


25

At a pressure of 1 bar, the temperature of liquid boiling oxygen stabilizes at 90 K. For sub-cooling of LOX, the temperature should be lower. It is possible to cool LOX by forced evaporation by a pressure lower than 1 bar. But the LOX tank in a rocket should be as light as possible. If the pressure inside the tank is substantially lower than outside, extra ...


22

Because it will almost certainly go KABOOM. Intimately mixed fuels and oxidizers are pretty much indistinguishable from explosives, and in particular, LOX intimately mixed with flammable hydrocarbons is wildly dangerous -- rather than being something you can handle, it tends to be set off by shock, vibration, or adiabatic compression that can be caused by ...


21

Excess capacity was needed in the storage sphere to allow for multiple attempts in a launch campaign. Much of the propellant was recovered during a scrub but not all. The storage spheres were loaded from waves of tanker trucks and it was a lengthy process - weeks to several months. It would have been embarrassing to run out of propellant after a series of ...


20

As small amounts of LOX boil off heat is removed from the remaining volume. Boiloff actively cools the fluid and helps keep the remainder liquid. Rockets typically have vents to aid in managing the boiloff rate and fluid feed lines to replace lost fluid while waiting on the pad. During flight the consumption rate outpaces any boiloff losses and it is not an ...


18

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 difference is quite small compared to the larger LOX temperature difference, and the fuel is only there for 35 minutes. There likely isn't a need to cool the RP-1 ...


15

N2O4/UDMH is the choice if you need a non cryogenic storable hypergolic fuel. But UDMH is toxic and carcinogenic and should be avoided if possible. UDMH is also corrosive. LOX/UDMH is not storable (cryogenic LOX) and not hypergolic. There are a lot other fuels to be combined with LOX and they are not toxic or carcinogenic and thus easier to handle. There ...


14

...is the tank within a tank a sound engineering concept for rocket stages? I take this to mean that you are not talking about pressurant bottles or other small devices submerged in the propellant tanks. Instead you mean the large primary propellant tanks. Then, No, this is not a good idea. It doesn't need to be a double-walled, or "dewar-flask" tank....


14

Edit Jan 2, 2017: Well, it was a COPV bottle after all. There were buckles in some liners where super-cooled liquid oxygen pooled. From NASAspaceflight article, quoting the results of the investigation: Each stage of Falcon 9 uses COPVs to store cold helium which is used to maintain tank pressure, and each COPV consists of an aluminum inner liner with ...


11

There is indeed a ratio of fuel to oxidizer that yields complete combustion, called the stoichiometric ratio. This produces the most thermal energy from combustion, but for a few different reasons, specific engines run at different ratios, most often on the fuel-rich side. As it happens, a very similar question came up a few days ago which explained some ...


11

Calculating how much LOX is lost is going to be an interesting calculation, but I'm not sure we have the data for that. Instead, I'll be focussing on the other part of your question: Is the loss replaced by tanker trucks or by a liquid oxygen plant near the launch site? The ball-shaped structures near pad 39A are storage tanks for liquid propellants. It'...


10

Cavitation is boiling, in this case it is caused by reduced pressure in the wake of blades. A boiling point is a combination of 2 factors; heat and pressure. If you can't do anything about the reduced pressure you can manipulate the other factor, which is the temperature. A liquid can stay in it's liquid state at a lower pressure if it is colder. I think the ...


8

To answer your first question: one of the main problems with using the oxidizer in general is oxidizing of the cooling channels. Any hot oxidizer has this problem, but oxygen definitively has this issue to the extreme, which is why earlier engines using the oxidizer as regenerative coolant have been with different oxidizers than oxygen (see for example the ...


7

The shuttle external tanks used liquid level sensors. You can see them on the left side of each tank in this schematic. Source: Page 95 of the old Press Manual Related sensors gained notoriety late in the program when the liquid hydrogen low level sensors, which were used as a safety system to cut off the main engines at fuel depletion, started indicating &...


7

At low temperatures, the activation energy for pure CH4 O2 oxidization is about 170kj/mole. (See figure 1 here) That’s about 1.8eV per atomic reaction. 1.8eV can be provided by 688nm red light, or any shorter wavelength. So generally, visible light can initiate reactions. I can’t quantify how many photons/cm2 it’ll take to start a runaway reaction from ...


7

There was a large difference in their size, and at the time, they were developed by two entirely different companies. In general, the propellant combination of a rocket engine does not determine its thrust, just as an internal combustion engine running on diesel fuel may power anything from a lawnmower to a tractor-trailer truck. The LR87 was developed by ...


6

Hard to prove a negative, but no, there is no provision for storing LOX on the ISS. The coldest thing up there is the MELFI, the Minus Eighty Degree Laboratory Freezer (for) ISS. Oxygen (and nitrogen) is stored as a high pressure gas in the tanks fitted to the outside of the US airlock. (The dog-house shaped objects around the airlock in the picture ...


6

The reason you go with UDMH/NTO F/O pair is storability, i.e. the ability of your rocket or missile to be stored, fully fueled straight from the factory, in a silo or stand on a launch rack for an extended amount of time, possibly years or even decades, and ready to use at a moment's notice, and spontaneous combustion upon contact with no ignition, meaning ...


6

Partial answer: I can identify the manager responsible for the decision, and the date, but not the reason why. LC-39 was the sole topic at a meeting of the Launch Operations Working Group on 18-19 July [1962] that brought together 113 representatives from LOD, MSFC, and the launch vehicle contractors: Boeing, North American, Douglas, and General Electric. ...


6

A not up to date answer but in 1972 J Clark in Ignition writes that cryogenic Oxygen+Ozone was investigated and found to be relatively stable* before use but having some exciting properties for any leftovers in pipes or tankage at end of run due to preferential evaporation of the Oxygen concentrating Ozone until it decomposed explosively. This could be ...


5

Liquid oxygen mixed with carbon powder has been used as an explosive for mining, see 1, 2. But there has been an explosion in a helium purifier 3. The use for mining required safe explosives, the rate of spontaneus self-ignitions should be very, very low. The charges should explode only when triggered by a detonator, but not when handling them or by static ...


5

Check out this article and the sources cited: Simulation of LOX reorientation using magnetic positive positioning https://link.springer.com/article/10.1007/BF02908417 Looks like it has been studied. Also this: The abstract of the apparently not paywalled Simulation of magnetic positive positioning for space based fluid management systems (https://doi.org/10....


5

LOX is paramagnetic, not fully magnetic. What does that mean? It takes an extremely large magnet to have any effect at all. The only design consideration which would need to occur at all would be to not have a powerful magnet near the thruster valve, or really anywhere near it. There would serve no real useful purpose for this, and thus it isn't required. ...


5

A cryogenic geyser occurs when a volume of cryogenic liquid inside e.g. a pipe suddenly boils, propelling the liquid/gas mixture through the pipe and into its destination at high speed. The pipe can then refill (potentially causing a water hammer), and the process may repeat. If it does, you have cryogenic geyser cycling. So it's not so much a filling ...


5

This answer is based mostly on the NPSH link Organic Marble shared (http://www.pumpschool.com/applications/NPSH.pdf) and the various properties you can infer about subcooled LOX. Subcooling lowers vapor pressure, which helps prevent bubble formation. Subcooling densifies the propellant, which allows lower fluid velocities at the same mass-flow rates, which ...


5

The answers on the reddit thread you linked are essentially correct. The camera angle is the only difference between the two images, making the flare appear further away. As you mention, Delta IV and Heavy use cryogenic hydrogen and oxygen as propellants at approximately -255°C and -185°C respectively. As these are loaded into the tanks in the lead up to ...


5

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 against 1G at the engines using the same structural elements that must handle several Gs in flight anyway so ground based support are largely 'free' other than ...


5

Sources here and here, see also Supply of liquid oxygen (LOX) maintained on the ISS? Kept cold using “space”, or refrigerator? A quick check via google for "liquid oxygen with hydrogen peroxide" shows that there is a product containing a 34% hydrogen peroxide solution in water which is given the name "liquid oxygen", which is a misnomer. It is not actually ...


5

The liquid oxygen was delivered from a remote location (likely Hawaii). The source doesn't state but it would have to be by ship. You might recall that the very first Falcon 1 launch attempt was scrubbed because a LOX valve opened in the storage facility and blew off too much LOX. Then Based on the ensuing discussion after the abort, the team expects ...


4

Just to mention one facet of this multifaceted problem, any electrical field potential that exists (i.e. items that aren't on a common bias electrically) can and usually will at some point create an arc (spark) when it discharges. Coupling and de-coupling of interfaces, feedlines, etc especially would be a danger if their electrical fields are uneven. Also, ...


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