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 ...


35

The Space Shuttle used liquid hydrogen, contained in the external tank along with liquid oxygen. While the Falcon rockets do use liquid oxygen, they do not use liquid hydrogen. Keeping the liquid hydrogen cool was the primary driver for the foam. The Orbiter was mounted alongside and below the the top of the external tank. The Falcon payload is mounted at ...


31

Most commercial commodity specifications for hydrocarbons such as gasoline, kerosene, Diesel fuel, jet fuel, naptha, mineral spirits, etc are fairly broad. RP-1 is kerosene that meets some particular specifications that are important for use as a rocket fuel, but not so important for burning it in gas turbines or diesel engines. The specifications for RP-1 ...


24

Really, there is nothing particularly special about it. Any liquid flowing through pipes in the engine wall will carry heat away from the engine as it heats up. Obviously, some liquids will be more effective than others. (Also, some propellants won't work because they'll either clog the pipes or explode, but RP-1 is especially formulated to avoid this). With ...


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 ...


18

The problem is not the foam breaking off per se, but the fact that the orbiter was below the fuel tank and got hit by the falling foam. The Dragon capsule is on top of the stack, it can't be hit by a piece of foam that comes off the booster.


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 $\...


13

Until Masten Space Systems reveals the exact composition of the propellants, we can only speculate on the combinations they used. Based on what you have presented in question we can rule out options one by one, but we cannot be 100% sure – especially for fuels because if we miss the oxidizer, we’ll miss the fuel as well. The smoking gun here is a sentence “...


13

As described in this QA, the upper stages of the Saturn V could fire their J-2 engines at different mixture ratios. The second stage would switch from 5.5:1 (oxidizer mass to fuel mass) for higher thrust, to 4.5:1 for higher fuel efficiency partway through the ascent. The third stage would normally start at 4.5:1 and switch to 5:1 partway through the burn,...


12

Do all chemically-fueled rockets need foam insulation? Not all, but some do. Generally the small subset of ones that utilize hydrogen fuel. The hydrogen-fueled Delta IV uses essentially the same insulating foam as shuttle did. Photo from clickorlando.com The hydrogen-fueled SLS uses a similar foam. Photo credit NASA This question Insulation on rockets--...


11

The 1976 NASA monograph Liquid Rocket Disconnects, Couplings, Fittings, Fixed Joints, and Seals defines "couplings" as Couplings are manually actuated separable connectors that require more than a few seconds for engagement or disengagement. and lists the following types: Flanged Threaded: Dynamic swivel couplings Shape memory alloy is not ...


10

The Falcon 9 burns somewhere around \$200k-300k in propellant (stated to be \$200k in 2015, but the vehicle's grown in size since then). For non-expendable launches, it puts about 16000 kg into orbit, so that's about \$20/kg. Starship burns cheaper methane fuel, and propellant cost is estimated at about \$500k/launch when purchased in volume. Total payload ...


9

The volumetric heat capacity of liquids is much higher than that of gases. You need much more energy to heat a certain volume of water than the same volume of air. The density of liquids is much bigger than that of gases, that is why they can transport much more heat energy. Therefore a liquid flowing through a pipe takes away much more heat than a gas ...


9

What is the theoretical fuel cost to launch 1 kg of payload to orbit on an ideal rocket (rocket with 0 kg dry mass)? We can use the rocket equation to get a rough idea of the fuel required. $$\delta V = v_e ln \frac{m_0}{m_f}$$ $\delta V$ required to reach LEO is 9.4 km/s $v_e$ is the exhaust velocity of the rocket, 3 km/s is pretty good for a chemical ...


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 ...


6

RP 1 fuel was red dyed for a thermal stability experiment on JP-8 and RP-1 fuel of various ratios. High Reynolds Number Thermal Stability (HiReTS) testing device. There are several factors that set the HiReTS machine apart from other thermal stability tests. The red dye of RP-1 was used to detect the various effects of parameters like temperature and ...


6

We have the capability to launch this already, so it is feasible, just very expensive when there are better alternatives. A spacecraft as you describe isn't just 50 tons of solar panels, you need a huge structure to hold them on, huge amounts of maneuvering fuel to align the spacecraft, extremely powerful gyros, and other elements that would have to be super-...


6

Partial answer because based on a simulation doesn't address the secondary question about changes with throttling The paper CFD SIMULATION OF A LIQUID ROCKET PROPELLANT (LH2 /LOx) COMBUSTION CHAMBER shows a "flame front" in the sense that majority of the combustion reactions take place in a relatively small area of the combustion chamber. (zero ...


5

Because it's 'free' energy for the taking! In a rocket, you have liquid fuels that need to be vaporized to burn correctly. To vaporize a liquid, you need to add heat energy to it: specifically its latent heat/enthalpy of vaporization, which is quite considerable. The enthalpy causes zero practical temperature increase: the substance is still the same ...


5

Nitrogen Dioxide is a chemical that forms an equilibrium with Dinitrogen Tetroxide, which in the world of rocketry is often just called "Nitrogen Tetroxide" so as to increase the amount of confusion. If you have a tank of one, it will change between being one or the other based on temperature or pressure. This is one of the commonly used hypergolic storable ...


5

PS to previous comment about refrigeration in the X-15. It had none, keeping weight absolutely minimal precluded it. Temperature was far more of an issue for the LOX than for the NH3. During captive carry to launch the LOX was replenished from a supply in the B-52 carrier aircraft; otherwise some degree of boil-off occurred. A special case of venting LOX was ...


4

In contrast to Tristan's answer, which claims that propyne performance is “probably” worse than saturated hydrocarbons currently used due to higher average mass of combustion gasses, propyne (methylacetylene) is actually superior in terms of Isp and according to this source is 4th performing fuel among all hydrocarbons, while propadiene (allene) being 2nd. ...


4

Solid rockets have very high "density specific impulse," that is, they produce a lot of thrust per unit volume, so an equivalent liquid stage of the same diameter would be somewhat longer, but not prohibitively so. There are a few extant liquid-propellant engines that produce similar thrust to the Vega first stage that could be used. The hydrogen-...


3

The critical pressure ratio for a de Laval nozzle is $$\left(\frac{P_0}{P_{atm}}\right)_{crit} = \left(\frac{\gamma+1}{2}\right)^{{\gamma}/({\gamma-1})}$$ Where $P_0$ = stagnation pressure in chamber $P_{atm}$ = atmospheric (back) pressure $\gamma$ = ratio of specific heats for the gas $(P_0 / P_{atm})$ must exceed this critical value in order for a de ...


3

Just to propose something specific in an answer: I would first guess Gallinstan (by mass: 68.5% Ga, 21.5% In, 10.0% Sn), at least if we're talking about near-room-temperature applications: Supposedly, it melts at -19°C, and has about a μPa or less vapor pressure at 500°C. (This is much lower than Hg, but I don't know if it's lower than pure gallium because ...


3

tl;dr: I see that comments below the question by the OP argue against this being a deal-breaker problem but I'm going to point it out anyway as a partial answer. Any engine using "sand" as a reaction mass will have to avoid any significant production of silica nanoparticles so large that they are not accelerated in the nozzle. Assuming a perfect, ...


3

The history of rocket fuel development has been dominated by getting them to work at the range of temperatures we want. For instance finding a fuel that is liquid enough to work in the Arctic, and not so volatile that it can't be stored at reasonable pressure in the desert. Unfortunately, kerosene freezes well above the boiling point of oxygen. It might be ...


3

to put it in 3 words "it will explode." you see fuel burns with oxidiser and mixing the two in the same storage will well let me make it in steps: you ignite the engine... the flame flows into the tank... that burns too... in a closed space... rapidly... which causes the tank to burst... and then you have no more rocket. ):


3

Just two short comments on the other excellent answers: Wall cooling is not free: What happens is that you (can) have a significant reduction in chamber pressure (depending on chamber size), reducing your thrust and efficiency. There may also be some second order effects on combustion efficiency when heat is removed from the process. So if we could run an ...


2

Yes! There are various studies conducted on the viability of fatty acids / parrafins / biodiesels as rocket fuels. Bio rocket fuel is an actual thing! This study shows that virtually any lipid-based feedstock, or raw material with a fat source -- including what is perceived as low-quality feedstock like cooking grease -- and turn it into virtually any ...


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