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Questions tagged [engine-design]

Questions regarding the design or design process for a propulsion system.

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6
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1answer
481 views

What are the issues and concerns related to turbopump blade cracks and manned spaceflight?

While the WSJ headline sounds ominous: Congressional Investigators Warn of SpaceX Rocket Defects, Quartz's SpaceX needs to redesign its engine to ensure it is safe for human spaceflight seems to be a ...
5
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1answer
279 views

How to prevent melting too much paraffin in a hybrid LOX-paraffin rocket?

In a hybrid LOX rocket, only the flow of LOX may be controlled. The amount of paraffin melted by heat is determined by the very complex heat transfer from gas to solid paraffin. If the mixture of ...
3
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1answer
806 views

Is it possible to estimate the nozzle characteristics of the Rocketdyne HG3 engine?

Boeing and the Marshall Space Flight Centre brought to pass many studies of improved Saturn V launch vehicles. The rockets proposed under the MLV and ELV projects would feature longer stages for more ...
3
votes
1answer
255 views

How is the Rocketdyne J-2S area ratio larger than that of the J-2?

The standard J-2 engine measures 3.38 metres in total length, with a nozzle exit diameter of 2.03 metres, to support its 27.5:1 expansion ratio. However, these dimensions are apparently identical for ...
7
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3answers
3k views

Overcoming pressure differential to feed fuel into rocket engines

When pumping fuel and oxidizer into a rocket engine, I presume the pump must create more pressure than the inside of the combustion chamber, otherwise the liquid would back-flow. Is this right? Then ...
4
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1answer
187 views

Build an engine that burns tholins

My idea is to send an hypothetical lander/rover to Titan, and recover from this some samples of rocks... To create a very efficient engine, I suppose to carry only liquid oxygen, and burn the ...
7
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1answer
469 views

Rocket Throttle vs. Jet Throttle

One of the drawbacks of jet engines is that they suffer from turbo lag, whereby a throttle change will take some amount of time to translate to a change in thrust due to the momentum of the turbine ...
9
votes
1answer
579 views

What was the maximum thrust of the Rocketdyne F-1 engine?

Reading through several old reports, I have come across studies conducted by MSFC on improved Saturn V designs with greater payload capacity, and with uprated engines. As a result of increasing launch ...
11
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1answer
634 views

Why does the YF-75D nozzle have such a strong spiral pattern?

Why does the YF-75D nozzle material have such a strong spiral pattern? Is it a result/biproduct of a manufacturing process only, or does it have some specific function? edit: The last, cropped ...
4
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4answers
1k views

What kind of engine does this Isp = 1600 refer to? Is it cubesat-friendly?

These two good answers (one and two) to the question "Is there a maximum Isp for 'exothermic chemical reaction rockets?'" put the limits around 500-550 seconds for the limits of practical chemical ...
23
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3answers
18k views

What's so special about SpaceX's Raptor rocket engine with 300 Bar chamber pressure?

What allows the Raptor engine to have a high chamber pressure of 300 Bar? Compared to other rocket engines which have been or that are now operational, it has the highest chamber pressure. What does ...
4
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0answers
206 views

How much propellant is “wasted” in the gas generator power cycle?

The gas generator power cycle is an open cycle, with pre-burner exhaust vented after driving the turbine instead of contributing to thrust as in more advanced power cycles. What percentage of the ...
3
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1answer
1k views

What is the 'Summerfield criterion' regarding rocket exhaust expansion

In this question the 'Summerfield criterion' is mentioned. Saying that 'Historically, the Summerfield criterion was used, where the minimum pressure in a nozzle must be greater than 0.35...0.4*...
10
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1answer
6k views

Rocket Engine Plumbing: Still don't understand the Full Flow Staged Combustion Cycle

I just found this incredible video KSP Doesn't Teach: Rocket Engine Plumbing and ran through it a few times. It's very helpful in the way it outlines the various issues first, and then designs the ...
12
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4answers
1k views

SpaceX's ITS - why gimbal only the inner cluster?

Does anyone know the reason why, in SpaceX's newly-announced ITS launch vehicle, only the inner cluster gimbals, and not the whole engine system?
2
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2answers
407 views

Some examples of pressure fed engines used on launch vehicles

Are there any examples of pressure fed engines used on launch vehicles? I already know of the ones on the wikipedia page which include Firefly Space Systems OTRAG (rocket) Quad (rocket) of Armadillo ...
4
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1answer
398 views

Detonation Liquid rocket engine

What is the detonation liquid rocket engine (LRE)? How does this work? How is it better than the average rocket engine? Russian scientists have successfully tested the first detonation liquid ...
3
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1answer
455 views

When this F9 2nd stage engine suddenly moves upon shutdown, is it moving along the rocket's axis?

The GIFs are made from frames of the live broadcast of SpaceX JCSat-16 2nd stage around the time of the second engine cut-off (SECO-2). It looks like the engine moves outward axially as the thrust ...
3
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3answers
1k views

Limiting factors of liquid rocket engine thrust

What are the limitations for the 1st stage liquid fueled rocket engines that are currently in widespread use, what are the factors that limit their total thrust? Why can't you just inject more and ...
24
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1answer
2k views

How realistic would the Sea Dragon engine be to produce given today's technology?

Just learned of the Sea Dragon proposal from back in 1962. From the Wikipedia entry The first stage was to be powered by a single enormous 80,000,000 pounds-force (360 MN) thrust engine burning RP-...
14
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1answer
2k views

What is that second (smoke) exhaust on a rocket engine for?

In this video of a Korea Aerospace Research Institute (KARI) rocket engine test, you can clearly see a second exhaust where thick smoke comes out. Is this an essential part of the engine, or just an ...
6
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2answers
4k views

How is a rocket engine started?

I understand the basic principle of how a rocket engine works, but what I cannot find any info about is how do they initiate the whole process. Can someone please explain to me what gives the turbo-...
11
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4answers
2k views

Do rocket engines have shock absorbers?

With a million pounds of thrust and many g of acceleration and a significant fraction of a g of vibration, connecting the engine to the rocket can't be trivial. At launch the mass is very high and ...
10
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1answer
1k views

If it is difficult for Merlin engine to have deeper throttling, could it be as an option a different engine at the center of the rocket?

In the landing procedure for the first stage of the Falcon 9 one concern is that : Merlin 1D throttling at its lowest level still generates more thrust than the empty mass of the first stage. So ...
7
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5answers
784 views

Would reusability affect the performance of a rocket engine compared to a single launch version of that rocket engine

Reusability of the rocket engines, which are the most expensive part of the rocket, is very important to keep low cost of the space rockets and in this way making reality the space programs considered ...
9
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1answer
709 views

Has any work been done on alternatives to rolling element bearings in rocket turbopumps?

Specifically: Using some high pressure gas (before or after combustion) as a fluid bearing. A superconducting maglev bearing, possibly using fuel as coolant. Any related work is also welcome.
3
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2answers
1k views

Can someone tell me the effect on performance of overexpanded nozzles?

I understand that underexpanded nozzles lose efficiency, due to untapped potential in the gas before exiting the nozzle, but what happens to overexpanded nozzles? I understand that the pressure of the ...
4
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2answers
448 views

Is it possible to keep fuel and oxidizer tanks pressurized during flight by heating up their contents using exhaust gases?

This could be done by leading tapped-off exhaust gases through heat-exchangers in the tanks (being careful that the exhaust gases don't freeze and block the pipe). I'm imagining this as an ...
8
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3answers
951 views

Why not use tap-off gas for repressurization for a simple rocket engine cycle?

In a tap-off cycle, combusted gases are extracted from the combustion chamber and routed to the turbines, which then drive fuel/oxidizer pumps. In a pressure-feed cycle, fuel/oxidizer is fed into the ...
3
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1answer
339 views

In turbopump designs where no propellant is dumped overboard what causes efficiency loss in engines?

In some turbopump designs, propellant is burned and used to power the pumps; then it is dumped overboard. This causes a reduced specific impulse, because not all all the propellant is expelled through ...
27
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4answers
4k views

Does the NK-33 engine require subcooled kerosene so cold that it turns to wax?

It was mentioned in this answer and in several other places on the internet that the kerosene fuel used by NK-33 engines needed to be subcooled enough so that it reached the same density as the LOX, ...
4
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1answer
268 views

How often can liquid hydrogen engines be restarted?

A proposal for lunar development, LunarCOTS, relies on a reusable shuttle running on LH2 and LOX to work. It lands, is refueled on the lunar surface, and then takes off again. Presumably it could sit ...
6
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1answer
302 views

Could oxygen be used in a resistojet in a vacuum environment?

Resistojets heat a compressed gas or vaporize a liquid to expand it through a nozzle for thrust. They improve a bit on the performance of cold gas thrusters. This experimental water resistojet managed ...
18
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2answers
3k views

Was the third shuttle engine any different from the others?

The space shuttle used three SSME, organized in a triangle with two next to each other closest to the external tank, and one on top of those. I am pretty sure the first two engines were close to ...
5
votes
1answer
578 views

Falcon 9 engine ignition sequence

On the space shuttle, engine ignition was delayed for the main engines. Not all of them were started at once, presumably to avoid vibrations. How does that work for the Falcon 9? I imagine that the ...
10
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3answers
2k views

What are the phases of ignition (and flameout) of a liquid fuel engine?

As I observed ignition of several rocket engines (Shuttle, AMDE, Lynx Suborbital, Saturn V) they all come through a couple phases - emitting various vapors, unfocused flame, etc, before the proper "...
13
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4answers
12k views

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

As I understand it, liquid-fueled rockets typically burn some amount of their fuel in a separate low-pressure combustion chamber, and then use the combustion products produced to drive the turbopump. ...
8
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1answer
1k views

Multiple engines vs one engine with multiple combustion chambers

What is the fundamental difference between a construction of n engines vs one engine with n combustion chambers? For example, Energia rocket used four boosters, each with a 4-chamber RD-170 engine, ...
7
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2answers
529 views

What challenges are there for more, smaller liquid fuel engines instead of one large?

Some questions popped up about difficulties of creating throttleable liquid fuel engines. I wonder why the obvious alternative isn't more common: multiple engines, from which only some will be lit; ...
20
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1answer
5k views

Why is the SABRE engine curved?

Why is the Reaction Engines Limited SABRE (Synergistic Air-Breathing Rocket Engine) curved along it's length?     Illustration of the SABRE engine with the pre-cooler heat ...
9
votes
3answers
482 views

How are nuclear thermal reactors designed for cosmic rays in space?

I was reading about thorium reactors here. It says 'Th-232 is fissionable with fast neutrons of over 1 MeV energy'. Most cosmic rays have lots more energy than that. I haven't found a reference for ...
32
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6answers
6k views

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

SpaceX have put methane on the map as a rocket fuel, but they weren't the first to consider its use. The first experiments in building a rocket engine that uses methane date back to 2007. Now methane ...
6
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0answers
457 views

What upgrades does the Merlin 1D need to increase its time between overhauls to 1000 hours?

This is a question I've been pondering for the last few weeks after I back-calculated the details of the Merlin 1D engine. Just as a thought exercise, I wanted to see what upgrades the Merlin 1D would ...
5
votes
1answer
408 views

Is a fluorine/hydrogen engine feasible for use in space? [duplicate]

Fluorine is a bit more efficient chemically than oxygen. It has never been used as a launcher oxidizer because it and its exhaust products are so toxic. That's as much I've heard about it anyway. But, ...
18
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1answer
3k views

Why design new rocket engines instead of using the existing types?

Already in the 1960s rocket engines seem to have achieved near maximum chemical efficiency. What are the reasons for new designs being in demand? How much better could a new engine design be than the ...
6
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1answer
130 views

Is pogo oscillation a risk in hybrid motors?

Is pogo oscillation accounted for in design of hybrid motors? I'm thinking particularly about hybrids that use Nitrous Oxide as the oxidizer because the weird triple point effects that one experiences ...
6
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1answer
674 views

What's the nature of hoop stresses on a rocket nozzle?

On a rocket nozzle, are the stresses (namely hoop stresses) from pressure differentials compressive or tensile? Obviously, in a combustion chamber, the pressure inside is greater than outside. As ...
6
votes
1answer
5k views

What is the procedure to stop the descent engine on the Apollo 11 LEM?

What is the correct procedure to stop the descent engine on the Apollo 11 LEM? When the LEM has a contact light on Apollo 11, there is some terminology spoken that I'm assuming is important (and ...
11
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1answer
3k views

What is the temperature inside a methane/oxygen rocket engine?

Assuming a simple rocket engine, with a combustion chamber and de laval nozzle, fueled by liquid methane and liquid oxygen, what temperature must the combustion chamber, choke and nozzle withstand? ...
28
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7answers
12k views

Why are Rocket engines at the base of the rocket?

I don't know much about Rockets, but all that I have seen, from the Saturn V to SpaceX's Falcon 9 have the engine at the bottom. Doesn't this make the Rocket really unstable, like balancing a pencil ...