59
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Why did the Soviet Union decide to use 30 small engines instead of a few large ones on the N1?
Developing new engines takes time, and time was a precious resource in the Moon race.
The major problem with making larger engines is the problem of combustion instability of large combustion chambers....
52
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Why do rocket nozzles flare?
The purpose of this nozzle is to achieve maximum acceleration of the flow to obtain the highest possible exit velocity.
The shape of convergent / divergent (de Laval) nozzles is dictated by the ...
- 188k
50
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If rocket engines only need fuel and oxidizer, then why there are so many pipe lines on the engines?
While an ideal engine would just ingest fuel and oxidizer and produce exhaust gas real world engines will have some combination of regenerative cooling, film cooling, turbine exhaust, hydraulic power, ...
- 23.4k
45
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Why can solid rockets be both the skinniest and most spherical launch vehicles while liquid fuel rockets have a more limited range of aspect ratios?
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 ...
- 170k
43
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Why cool engines with fuel as opposed to oxidizer?
Whatever you use as a coolant will become hot. Hot oxygen will (a) vaporize, making the plumbing somewhat more difficult, and (b) react with and erode (or maybe even ignite) the cooling channels, ...
- 10.1k
37
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Would a grinding machine be a simple and workable propulsion system for an interplanetary spacecraft?
The main engineering challenge in implementing your proposal is that in order to be competitive with a chemical rocket engine, the grinding wheel must rotate at an extremely high velocity. A typical ...
- 486
36
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Is it common and good engineering for a pair of cables to be easily plugged into each other's connectors in modern spacecraft
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 ...
- 188k
36
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What is the maximum number of times a liquid rocket engine has detonated/ exploded during development?
Since my job at one point in my career was writing a real-time simulation of the Space Shuttle Main Engine so that the Nexus of Evil could fail it in creative ways, I've spend some time studying the ...
- 188k
33
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What is a "Major Component Failure" referred to in news reports about the unsuccessful Space Launch System core stage test firing?
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 ...
- 188k
30
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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
30
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Performance of a pumpless liquid rocket engine
The performance of a rocket engine - its specific impulse - is directly proportional to the velocity of exhaust gas (and nothing else!). That velocity is achieved by releasing the combustion products ...
- 55.3k
29
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Did any rockets use differential throttling instead of gimbal?
The first stage of the Soviet N-1 moon rocket (Block A) used this type of differential thrust system. It had 30 engines in 2 rings. The outer ring of 24 engines used differential thrust control to ...
- 2,469
27
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Why Doesn't the cooling system on a rocket engine burn the fuel?
It's inside a pipe with no air, oxygen, or another oxidizer.
The fuel in the cooling channel is contained, it's not exposed to air or oxygen. As such, it can't ignite. There's no way for it to burn.
...
- 9,188
26
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Why do rocket nozzles flare?
The gas at the narrowest part (the throat) of a convergent-divergent nozzle used in a rocket engine is ideally moving at the Mach 1, the speed of sound. This creates a choked flow condition. After the ...
- 75.7k
26
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Is it common and good engineering for a pair of cables to be easily plugged into each other's connectors in modern spacecraft
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 ...
- 23.4k
24
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Using of the rocket propellant for engine cooling
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 ...
- 9,188
22
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How are rocket nozzles made?
There are many kinds of nozzles, and many ways to manufacture them. Here is a sampling.
Actively cooled nozzles such as the the SSME and F-1 nozzles were constructed by fabricating the individual ...
- 188k
22
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Why aren't expander cycle engines used on lower stages?
It seems to me you've got two questions: 1) Why can open-expander-cycle engines be larger than closed-? and 2) Why aren't there more expander-cycle sea level engines? Your question[s] shows you are ...
- 11.2k
22
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Why do the Titan SRBs have an angled engine bell?
As Ohsin comments above, the SRB nozzles are canted to direct the thrust approximately through the rocket's center of mass. This prevents any imbalance in thrust between the SRBs from creating a ...
- 170k
21
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Benefit of Raptor Engines
A few different factors contribute to the Raptor's higher thrust:
The specific impulse -- force delivered per mass of propellant consumed -- of methane-LOX combustion is generally higher than ...
- 170k
21
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Have Air-breathing Engines ever been used on a reentry vehicle, could they be?
As @OrganicMarble alluded to, the Buran Soviet shuttle was designed with turbojet engines (see here; and here, under "The engines") to extend the range of possible landing locations given the re-entry ...
- 18.3k
21
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Why are stages not connected by the engine nozzle? Why are interstages used?
There is a misunderstanding in your question
"The engine bell(s) already support the entire compressional stress generated by the weight of the stages above it when the engine is firing..."
...
- 188k
20
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What's so special about SpaceX's Raptor rocket engine with 300 Bar chamber pressure?
The Raptor is a full-flow staged combustion methalox engine. There is a lot of new technology in that sentence.
Staged Combustion
Fuel and/or oxidizer is ignited to run a turbine that spins a ...
- 3,857
19
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Would a grinding machine be a simple and workable propulsion system for an interplanetary spacecraft?
I don't know if it has ever been considered by anyone.
In my view, this is not a good idea for at least the following reasons:
It is equivalent to mechanically throwing things retrograde. See this ...
- 5,505
18
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Have Air-breathing Engines ever been used on a reentry vehicle, could they be?
I don't believe any vehicles equipped with air-breathing engines have flown to space and returned. Some test vehicles for Buran had jet engines installed, but they did not fly to space. In this ...
- 188k
18
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Why is SpaceX's Raptor's design so simple in comparison to SSME?
I wouldn't draw any conclusions based on diagrams alone, SSME is very well-known to the public, so we have a more detailed diagram. That doesn't mean that the actual engine is more or less complex, ...
- 1,336
18
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Why does the core stage of the Ariane 5 produce more thrust in vacuum?
It's because the ambient atmospheric pressure affects the thrust generated by the engine.
(Image source)
An engine nozzle has a "design altitude" at which the pressure of the exhaust at the exit ...
- 188k
18
votes
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Have there been rocket engines designed for diesel? What ISP theoretically possible?
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.
...
- 170k
18
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Using nuclear detonations for propulsion
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 ...
- 188k
17
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SpaceX's ITS - why gimbal only the inner cluster?
The main issue is one of size. Each engine bell requires space and with 42 that is a lot of space.
In order to gimbal there needs to be room for the bell to actually move, which means you need to ...
- 80.2k
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