# Tag Info

43

The squat end of the spectrum has little to do with solids versus liquids and everything to do with aerodynamics. Spherical tankage is most weight-efficient, so you'd expect squat stages in cases where aerodynamics don't dominate such as your Mars Ascent Vehicle (flying where atmospheric drag is on the order of 1% what it is for Earth ascent) or the Apollo ...

34

Off the top of my head I can think of several failures caused by miscabling. On Apollo 6 the signal to shutdown a malfunctioning second stage engine was cabled to a different engine, resulting in two shutting down instead of one. See: Apollo 6, reason for premature engine shutdown of two engines of second stage of Saturn V? The system used to release a ...

34

tl;dr Each engine reports a self-test status to the vehicle it's attached to. "MCF" is one of the possible statuses and indicates that the engine controller has detected a serious - but not catastrophic - failure within the engine. Details The Space Shuttle Main Engines (SSMEs) aka RS-25s transmit data to the vehicle they are attached to using a ...

26

Not in flight but this 1996 NASA lesson learned document lists multiple instances of mis connected cables during ground assembly and test including on Galileo. It in turn references JPL documents attempting to avoid re-occurrence, unclear if ESA has a similar document/process. The concept here is keyed connectors, many mil spec connectors come in multiple ...

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 ...

18

Apparently, at least one OTRAG rocket test used diesel. OTRAG's intended fuel was kerosene with a nitric acid/$N_2O_4$ blend for oxidizer, so I would guess they used a similar oxidizer with diesel. Most large rocket engines pass the fuel through tubes surrounding the combustion chamber for cooling; normal kerosene and other common hydrocarbon fuels tend to &...

18

The reaction mass is included in the bomb a.k.a. "pulse unit" The original project designed bombs with a reaction mass made of tungsten. The bomb's geometry and materials focused the X-rays and plasma from the core of nuclear explosive to hit the reaction mass. In effect each bomb would be a nuclear shaped charge. A preliminary design for a ...

17

This was done for load balancing purposes. The turbopump arrangement was as follows: the LOX pump at the top the fuel pump in the middle the turbine at the bottom The fuel was fed from two sides of the pump, and there were also two outlets. In this way, any fluctuation in input or output pressure was balanced, avoiding sideways forces acting on the pump ...

13

Not flight related, but everyday: Flammable gas cylinders have left hand threads. Oxygen, and other oxidizing gasses have right hand threads. The two examples I can think of involve propane and acetylene tanks. (I think that small propane cylinders now have a unique right handed thread for connecting to barbecues) On a different tack: Firehose couplings ...

12

The material of the bomb is the reaction mass. When a nuclear explosive is detonated in vacuum, the material of the bomb, and anything immediately adjacent to it, gets vaporized and accelerated at high velocity in every direction away from the center of the explosion. Organic Marble's answer describes how this can be optimized to make most of the vaporized ...

11

If you were able to change a booster rocket engine nozzle's area ratio at will, you would want it to expand, not contract1. Best performance is achieved when the exit plane pressure matches the ambient pressure. As the rocket ascends, the ambient pressure drops, and more expansion is needed, not less. Why don't they do this? The usual aerospace reasons: ...

11

Partial answer: This engine from the 1970s vintage Viking Lander is a liquid engine featuring one combustion chamber and many nozzles. (you can ignore the red arrow, it's from another question). The reason for this design was to prevent exhaust plume erosion of the Martian surface below the lander, to prevent degradation of the science results. Source ...

9

This is literally where Murphy's Law, "Anything that can go wrong will go wrong", came from. If you design a parts so they can be fitted incorrectly, they will be fitted incorrectly. "Murphy" is Edward Murphy Jr.. He was an aerospace engineer working on rocket sleds. In 1948 he suggested installing strain gauges to measure the force of ...

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

Sutton edition 7 mentions them without too much detail Jet vanes are pairs of heat-resistant, aerodynamic wing-shaped surfaces submerged in the exhaust jet of a fixed rocket nozzle. They were first used about 55 years ago. They cause extra drag (2 to 5% less Is; drag increases with larger vane deflections) and erosion of the vane material. Graphite jet ...

8

First time answering here, so let me know if I need more detail. I worked as an engineer in the avionics testing lab for Space Shuttle for about 5 years, and I have personally witnessed incorrect cables connected multiple times, sometimes resulting in permanently damaged equipment. It's actually not that difficult to mix up your cabling. With most of the ...

8

For solid core engines, yes, that's their limit. If so, what is the limiting factor? The exhaust velocity (and hence specific impulse) is linked to the heat of the propellant. The propellant can't get any hotter than the fuel elements. Why can't they easily go higher? Cos your fuel elements would melt and blow out of the back of the rocket in an ...

7

This is the same or similar unphysical stuff as before. Then for 40W power inside cavity, the calculated Thrust T=20.44mN. There is no propellant here. If 40 Watts were in the form of photons, then the thrust would be $P/c$ = 133 nanoNewtons. This generates 105 more momentum per unit time that it's allowed to. What's the final word; does the EmDrive ...

7

It is better to use keyed or polarized cable connectors that could not be inserted to a wrong socket or in a wrong rotation. But what should be done with the second stage of the Saturn V used for Apollo 6? When a fuel line ruptured, two instead of one of the five engines were shutdown because some cables were switched between two engines. So the connectors ...

7

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 modifications were unique and were accomplished under the contract; assemblies that were changed were the pump, turbine, thrust control, injector, and thrust chamber. ...

6

Do not have the maths skills to generate an example rocket engine turbine/pump system from first principles but the Wikipedia page indicates that efficient operation both as a pump and a turbine requires the plates to be close enough together to achieve laminar flow and that the fluid path make several circuits around the disks (to maintain laminar rather ...

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 ...

6

"If the pressure in the combustion chamber has to be exceeded by the pressure provided by the pumps, is it also exceeded by the pressure in the gas generator. " Just to be clear, there's no "if" about this ==> "the pressure in the combustion chamber has to be exceeded by the pressure provided by the pumps" Addressing "is ...

6

An exhaustive 42 seconds of googling reveals this on Stellar Exploration's website: As part of early R&D for a NASA funded deep space nano-satellite mission we have designed, built, and tested a miniaturized hypergolic bipropellant thruster. It provides 3 N of thrust with 285 sec specific impulse. The propellant is pressurized with gear pumps, allowing ...

5

Your question is very general, so a general answer is that, a valve or valves control the flow of propellants to the turbine that drives the pump. An engine controller determines the proper valve setting based on sensor readings from the engine. For the case of the Space Shuttle Main Engine During the engine run phase, the MOV, MFV, and CCV are switched to ...

5

According to the JAXA page about the rocket, it's a solid-fuel motor: The propellant, a pre-formed grain, polyurethane composite with a low burning rate... By polyurethane composite I assume they mean HTBP plus ammonium perchlorate and aluminum powder, since that's what JAXA generally uses for solid rockets. Since it's a solid rocket stage, the motor ...

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 ...

4

Partial answer. At least not for a main engine for an orbital rocket, as the Rutherford engine is currently the only such engine using an electric pump. And it uses batteries. However, conclusively ruling out all smaller secondary thrusters and propulsion systems is much harder. Electric feed pumps are beneficial for reducing complexity by not having to ...

4

From my (probably) similarily rough understanding of L*, it's a minimum size required for propellants to stay long enough in the chamber to mix properly. If the distance is shorter than that, you will experience problems with combustion instability. As such, having a length that's too large is certainly not as bad as too short, although the engine is then ...

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