59 votes
Accepted

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....
SE - stop firing the good guys's user avatar
50 votes
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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 ...
Organic Marble's user avatar
50 votes
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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, ...
GremlinWranger's user avatar
45 votes
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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 ...
Russell Borogove's user avatar
43 votes
Accepted

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, ...
pericynthion's user avatar
  • 10.1k
42 votes
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Why did it take so long for methane to be used as a rocket propellant?

Or am I wrong and have there been attempts to build a methane rocket in the past? Well, if there were, I figured that John D. Clark's famous book Ignition! (1972, free online copy) would be the place ...
Ilmari Karonen's user avatar
38 votes

Why did it take so long for methane to be used as a rocket propellant?

The three main competitors for liquid fuel choices to date have been: Hypergolics - easiest to get started with Kerosene/LOX - Good thrust, low performance, but dense LH/LOX - Best performance, ...
geoffc's user avatar
  • 79.3k
37 votes
Accepted

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 ...
Thorondor's user avatar
  • 486
36 votes

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 ...
Organic Marble's user avatar
34 votes
Accepted

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 ...
Organic Marble's user avatar
32 votes
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Was the third shuttle engine any different from the others?

The engines themselves were identical within manufacturing tolerances, but there were some installation differences, mostly due to "packaging" constraints in the crowded aft compartment of the shuttle....
Organic Marble's user avatar
30 votes
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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 ...
SF.'s user avatar
  • 54.9k
30 votes
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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 ...
SF.'s user avatar
  • 54.9k
26 votes
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How realistic would the Sea Dragon engine be to produce given today's technology?

Has any research into actually producing anything larger than the F1 been seriously carried out? The M-1 was a hydrogen engine just a little larger than the F-1. Parts of it were built and tested and ...
Russell Borogove's user avatar
26 votes
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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 ...
Josh King's user avatar
  • 2,391
26 votes

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 ...
GremlinWranger's user avatar
25 votes
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Why is the SABRE engine curved?

According to Mark Hempsell, formerly Future Programmes Director at Reaction Engines Ltd., now CEO of Hempsell Astronautics Ltd., explaining the reason for SABRE's curved nacelle over at ...
TildalWave's user avatar
  • 76.5k
25 votes
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What is that second (smoke) exhaust on a rocket engine for?

That is the exhaust of the turbopump drive. They burn a small amount of propellant, those exhaust gases are used to drive the turbopump that pumps the propellant and oxygen to the engine. There are ...
Hobbes's user avatar
  • 126k
25 votes

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 ...
David Hammen's user avatar
  • 73.2k
24 votes

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 ...
ikrase's user avatar
  • 8,627
22 votes
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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 ...
Tom Spilker's user avatar
  • 18.2k
22 votes
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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 ...
Russell Borogove's user avatar
21 votes
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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 ...
Organic Marble's user avatar
21 votes
Accepted

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 ...
Russell Borogove's user avatar
21 votes
Accepted

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 ...
Anton Hengst's user avatar
  • 10.6k
21 votes

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..." ...
Organic Marble's user avatar
20 votes
Accepted

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 ...
T.J. Tarazevits's user avatar
19 votes

Why don't rockets drive the turbopump from the combustion chamber?

You've got it slightly incorrect. Staged combustion engines pre-burn the propellants at a higher, not lower pressure than the main chamber. The exhaust from the preburner isn't pumped into the main ...
Organic Marble's user avatar
19 votes

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 ...
Everyday Astronaut's user avatar
18 votes

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 ...
Organic Marble's user avatar

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