53

The book 'Ignition!' tells the history of propellant research and has this to say about ozone from page 112 available here For it has its drawbacks. The least of these is that it's at least as toxic as fluorine. (People who speak of the invigorating odor of ozone have never met a real concentration of it!) Much more important is the fact that it's ...


25

The helium is used to continuously re-pressurise the propellant and LOx tanks as they are emptied. It is stored in a COPV inside the body of the LOx tanks to keep the He at a lower temperature (and higher density) to maximise loading capacity. The helium is cycled around the Merlin engine to be heated before being fed into the tanks. This has two main ...


20

Ozone is not stable, storing in liquid form as a solution in LOX requires stabilizers. It will oxidise most metals. A gaseous mixture of ozone and oxygen may decompose explosively. And it is poisonous in low concentrations. Nobody wants such boiloff gases at the launch pad. See https://en.wikipedia.org/wiki/Ozone


17

Solid fuel ramjets exist The problem for a launch system is you would need a lot of oxidiser anyway — ramjets only start to produce thrust from Mach 1.5–2. They also start to lose thrust above Mach 4–5. Add onto this the huge amount of intake air that would be needed for a system with a high thrust/weight ratio and the complexity of ...


14

A good pressurizing gas needs to satisfy a few basic properties: it needs to stay gaseous at the temperatures and pressures your fuel and oxidizer are stored at, so that it won't just condense out when injected into the tanks; it needs to be inert enough to be safe to mix with both the fuel and the oxidizer (since if you're going to have two different ...


11

This depends on what "better" is. But let us talk about fluorine. The main point of using it is that turning your hydrogen into $HF$ gives more energy than getting $H_2O$ for pure hydrogen, that gives a small improvement of $I_{sp}$. However, for fuels containing carbon, like JP1, (or perhaps RP-1 or JP4. JP1 has some unfortunate properties for rocket ...


9

MON according to Wikipedia: Mixed oxides of nitrogen (MON) are solutions of nitric oxide (NO) in dinitrogen tetroxide/nitrogen dioxide (N2O4 and NO2). The addition of a small amount of nitric oxide (1%-10%) makes the oxidizer less corrosive, but slightly less powerful as well, and changes the freezing point of the liquid. MON3 means 3% nitric oxide by ...


9

The problem in making propellant on Venus, is surely in finding the fuel, rather than the oxidizer. Oxygen can be made by electrolyzing $\text{CO}_2$ if necessary and while $\text{S}_2\text{O}_8^{2-}$ is a very strong oxidizer, meaning that it will oxidize lots of things, the mass of the sulphur atoms means that pure oxygen is probably a better rocket fuel ...


8

If the question is whether such a system is feasible, the answer is yes, it is 100% feasible, because STS used this exact system. The LOX and LH2 tanks in the ET were pressurized on the pad by GSE-supplied helium. After SSME start the tanks were pressurized by gaseous propellants tapped from the engines. From the 1985 NASA shuttle press reference: ...


7

You'd need a complex intake: it has to be closed during ignition, with a large closing force (otherwise you'd have half the thrust going out the intake), then it has to move out and keep changing its position as speed increases (to keep the shockwaves coming off the inlet cone in the correct position), then after about (handwaving) 30 seconds it has to close ...


7

According to the super-detailed and very informative NASA-CR 165404 Fuel/Oxidizer-Rich High-Pressure Preburners, the primary advantages of hydrocarbon-fueled oxidizer-rich staged-combustion engines is that "carbon formation, coking, and the attainment of ignition are no longer issues." (page 133) This useful rocket engine cycle overview presentation from ...


7

It's always by mass but there's one additional problem that rockets pretty much never use stoichiometric oxygen to fuel ratio (O/F) that you'd expect if you calculated molar mass of propellant components an their ideal exhaust product(s). So the source should mention that somewhere if they're using stoichiometric ratios, typical O/F or even quoting some ...


7

Peroxydisulfates and acid itself would be a bad choice for rocket oxidizers for several reasons: H2S2O8 is actually a solid with melting point of 65°C, therefore unsuitable for liquid fueled rockets, In pure form acid is even more aggressive and corrosive than sulfuric acid, it's like sulfuric acid on steroids. It can explode in contact with organic ...


6

The safety-related costs of developing, testing, and fueling fluorine-oxidized rockets outweigh the costs of building slightly bigger and less efficient rockets using hypergolics or LOX. In launcher stages, hydrolox is only 5% less efficient by Isp than hydrogen-fluorine; the higher density of fluorine makes for more compact tankage, though, which means ...


6

First we have to go back to the chemical equations, and this time, include the standard enthalpy of combustion. Hydrogen: 2 H$_2$ + O$_2$ → 2 H$_2$O + 572 kJ/mol Methane: CH$_4$ + 2 O$_2$ → CO$_2$ + 2 H$_2$O + 889 kJ/mol Dodecane: 2 C$_{12}$H$_{26}$ + 37 O$_2$ → 24 CO$_2$ + 26 H$_2$O + 15,026 kJ/mol Ethanol: C$_2$H$_5$OH + 3 O$_2$ → 2 CO$_2$ + 3 H$_2$O + ...


6

HTP has been used as an oxidizer before. Kind of. See BLACK ARROW and the rest of the British keroxide. Turns out HTP by itself isn't a great oxidizer, but when you catalyze its decomposition into water and O2, you get lots of dry steam and hot O2, the latter of which is an excellent oxidizer. In fact, it's so hot, it's basically hypergolic. But there's ...


5

I probably shouldn't answer this question, then again I can't vote to close because it is to broad and ambiguous, so I will try and give an suitable answer to help the OP out. First aspect: What is the propellant? Different propellants can be piped at different rates mostly related to their chemical volatility. If your propellant was water for instance, ...


5

The use of MON, as distinct from N2O4, arose because the latter can cause stress corrosion cracking (SCC) of titanium alloys. This was first observed in the 1960's during the development of the Apollo systems. The mechanism for SCC is believed to relate to the presence of oxygen in N2O4. Addition of nitric oxide (NO) to the propellant eliminates O2 by ...


5

They're subcooling the LOX in order to get more oxygen in the tank. The lower temperature translates to something like 3% more oxygen (by weight) in the same volume. When the LOX warms up, it expands so tank pressure will rise rapidly unless you vent the oxygen. So if you use subcooled oxygen, a launch delay will leave you with less oxygen than you need. ...


5

Normal vehicles that use LOX, use it at the normal temp (-183C) and what they do is let the LOX boil off, and refill it right up to the latest possible moment their hardware allows. The Falcon 9 1.1 Full Thrust (or whatever it is finally called) uses the LOX supercooled to -207C which is a different problem. The answer is unclear and is obviously something ...


5

In describing an instance of an autogenous pressurization system, Appendix E of A Review of United States Air Force and Department of Defense Aerospace Propulsion Needs (downloaded from: http://www.nap.edu/catalog/11780.html) states: [Vapor Pressurization] utilizes the internal energy of a liquid stored in a closed container to perform the work required ...


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 ...


4

Yes, "Liquid Air Cycle Engine" (LACE) is the proper nomenclature for this "camel" concept, and it has been studied before. Some incarnations have gone into early design by space agencies. NASA GTX Reference Apparently, a LACE had been seriously considered as something which would be the next design step after the X-33. I still find this a little confusing, ...


4

Compression will by it's nature heat things up. Storing air while in flight would tend to heat the system up. Keeping rockets cool is a major challenge, so an increase of heat would likely impact things even further. Yes, you could get some improvements in the air breathing portion of the flight. But you gain a significant amount by launching outside of the ...


4

Keep in mind that for bipropellant chemical rockets, fuel-rich combustion is generally preferred: it keeps temperatures more manageable than stoichiometric combustion, and tends to produce simpler molecules in the exhaust, which leads to less kinetic energy held in vibrating intra-molecular bonds and more kinetic energy going straight down the nozzle. ...


4

Helium is a noble gas, meaning it does not react with other atoms. In fact, it is the least reactive of them all. No compounds containing helium has ever been found, although some of the heavier noble gasses have formed unstable compounds. As helium can not be part of any molecule, it can not release chemical energy in any way thus failing to be an oxidizer. ...


4

"On The Shoulders of Titans" suggests that the oxidizer leakage was simply the natural outcome of allowing the oxidizer to flow into the (open-ended) combustion chamber prior to the fuel: The problem was rooted in NASA's original specification for a Gemini target vehicle able to start and stop its main engine five times during a mission, in contrast to ...


3

There aren't many atomic or diatomic gases at room temperature: H, N, O, F, Cl and the noble gases. noble gases are expensive F and Cl are corrosive oxygen reacts with propellants, so can only be used to pressurize an oxygen tank H is flammable/explosive that leaves N and the cheapest of the noble gases, He. Compound gases also exist (e.g. CO2) but they ...


3

Besides pure oxygen, several other oxidizers in theory have better performance with hydrocarbon fuels, but none of them are used because of stability, toxicity and price issues. But let mention some of them: Ozone O3. It's allotrope of oxygen with enthalpy of formation 142,67 KJ/mol (2.97MJ/kg) which can bust combustion energy up to 30% depending on fuel ...


3

A good way to get a feel for the relative strengths of various oxidizers is to compare their standard reduction potentials. Fluorine is one of the most potent oxidizers known, with a reduction potential of +2.87 V. Here are some others that you might find relevant: S$_2$O$_8$$^2$$^-$, +2.01 V H$_2$O$_2$, ...


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