Questions tagged [engine-design]

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

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11
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4answers
1k views

Performance of a pumpless liquid rocket engine

Basically all rockets that I know of have a pump feeding fuel and oxidiser into the combustion chamber. The turbopump is one of the most complicated and expensive components of the entire rocket. If a ...
12
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1answer
925 views

Viking Lander descent engine design feature

The Viking Lander Terminal Descent Engine (3 per vehicle) was a ~600 lbf monopropellant hydrazine engine with an unusual exhaust system of 18 small nozzles. Multiple sources state that the reason ...
7
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5answers
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What sort of analysis was performed before “modern” computing and the invention of finite element analysis and computational fluid dynamics?

I am not sure if this question is appropriate for this SE - Ideally this should be posted in Engineering SE but as far as I'm aware it does not exist! (I can only assume that the scope of engineering ...
5
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2answers
601 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 ...
2
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0answers
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Where could I find more propellant combustion charts for more different/more broad examples/numbers?

So after asking how I could calculate this kind of propellant combustion charts for different fuels/oxidizers and other ratios and other stuff and getting some really good answers, especially from ...
9
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3answers
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Why are stages not connected by the engine nozzle? Why are interstages used?

First, a clarification: I understand the aerodynamic reasons that interstages are used, and I understand that the shockwaves that would be generated without an interstage would wreck the rocket. My ...
22
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2answers
6k views

If rocket engines only need fuel and oxidizer, then why there are so many pipe lines on the engines?

If fuel and oxidizer are pumped by turbines to the combustion chamber, then why there are so many pipes around? It should only have a two-cylinder shaped turbine assembly. I doubt there are other ...
7
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1answer
148 views

Which are good resources to learn more about the components of a rocket engine?

A detailed and annotated image of a SpaceX raptor engine (found on a SpaceX website) illustrates that in addition to the major components (e.g. pumps, inlets, combustion chamber, nozzle), there are ...
3
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0answers
229 views

What is the function of this Merlin engine's tube, and why is it getting red hot?

In the video of the recent SpaceX Starlink launch, one view of the Falcon-9 2nd stage engine shows a cane-shaped tube that glows red hot at the "handle" end and seems to get hotter over time....
10
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2answers
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Is the concept of the Epstein Drive based on actual theorized scientific research which is considered plausable?

I've always found it interesting when we see real life taking its cues from fictional arts, especially when it comes to Science Fiction technology. There are plenty of examples of classic books, TV ...
3
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3answers
193 views

What (if anything) limits the efficiency of a rocket engine?

Humans have developed lots of rockets. I observe that in most cases to increase the payload capacity we just increase the amount of fuel. Is it not possible to exponentially increase the efficiency ...
3
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2answers
90 views

How to calculate these engine parameters on my own?

I am a space enthusiast and am intrigued mostly by rockets. I recently found a book HOW to DESIGN, BUILD and TEST SMALL LIQUID-FUEL ROCKET ENGINES and have been fiddling around with rocket engine ...
23
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2answers
3k views

Why do pressure fed engines have combustion instabilities?

Reading about the Sea Dragon idea, I came upon this argument against it, which sounds compelling, but relies on more detailed knowledge than I have: Those are to be pressure-fed to avoid "...
3
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0answers
37 views

Storage density of a Deuterium-Helium 3 fusion pellet

in a series I am working on I will be using a D-He3 fusion drive system (similar to the one in the expanse according to Project RHO). I am under the assumption that the fuel will be stored in a pellet ...
3
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1answer
227 views

Does engine purging cause dry run of turbo pump in a liquid rocket engine? If it occurs, what is the implication?

Does engine purging in a liquid rocket engine cause dry run of the turbopump? If so, does that have any implication for the design, health, maintenance, or operation of the pump? How do we calculate ...
0
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1answer
64 views

Pressure withstanding capability

As you can see in this pic, F-1 rocket engine consists of 15 main components. Now, how is it possible to keep all the components together intact in high pressure situations like when the rocket is in ...
11
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1answer
660 views

Why does the core stage of the Ariane 5 produce more thrust in vacuum?

In listening to a youtube video that was discussing the Ariane 5, the narrator noted briefly in passing that the Vulcain 2 engine produced more power thrust in a vacuum than it did at sea level. Not ...
16
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1answer
1k views

What is an “exhausterator” and what does it do?

I laughed when I first saw the word "exhausterator" mentioned, I scratched my head when I saw it the second time, and I came here after the third. Besides making me feel like maybe technobabble isn't ...
4
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2answers
277 views

How do spherical SRB's compare to long skinny ones? What do their thrust curves look like?

Most SRBs are long and skinny, probably because most are used low in Earth's atmosphere where aerodynamic drag is large. But here are some very short SRBs, one seemingly spherical except for the ...
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0answers
94 views

Why was circa 600 volts used for DAWN's ion propulsion?

This answer estimates that the DAWN spacecraft's solar-electric propulsion accelerated about 3 milligrams of Xe+1 per second, using roughly 1350 Watts of electrical power. I estimate that 3 mg/sec of ...
6
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1answer
143 views

What is the thickness of a rocket nozzle?

For a university project, I'm working on optimisation of a Falcon-9-like launch vehicle, and one element of that is varying expansion ratios of the engines. This will impact on the engine mass, but to ...
5
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1answer
314 views

What's the actual oxidizer/fuel ratio in the combustion chamber of the Vulcain?

I'm working on a simple exercise on the Vulcain, but I'm having a hard time figuring out what the real O/F ratio is, in the combustion chamber. I need the mixture ratio in the chamber to calculate the ...
8
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2answers
4k views

How is chamber pressure determined for rocket engines?

I've been looking for this for quite some time now, and I can't find anything other than calculations where they already assume a chamber pressure. So my questions are two: What are the equations for ...
9
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1answer
5k views

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

What was the correct procedure to stop the descent engine on the Apollo 11 LEM? When the LEM had a contact light on Apollo 11, there was some terminology spoken that I'm assuming is important (and ...
5
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1answer
254 views

Is there anything fundamentally wrong with 'autogenous expander cycle`?

This question is a spinoff from here. To set the context, here is my understanding of the expander cycle: Closed expander cycle is very efficient, perhaps more efficient than staged combustion cycle....
0
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1answer
67 views

Calculations needed to full-design a rocket

Suppose I want to put a cubesat in Titan's orbit (saturn's moon). and I want to calculate what rocket power I need, how do I calculate it? Where do I begin? total mass of the probe or delta-v needed? ...
2
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1answer
45 views

Are regneratively cooled nozzles still modeled as isentropic flow?

In a regeneratively cooled nozzle, there is a transfer of heat from the expanding exhaust to the nozzle (and then into the propellant cooling the nozzle). This is clearly not an adiabatic process. Is ...
27
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1answer
3k 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-...
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0answers
47 views

What is the load path for thrust in a rocket engine? [duplicate]

This may be a duplicate of this question but I wasn't sure if I could hijack that one to clarify or regenerate interest there. What is the distribution of axial force in a combustion chamber? My ...
6
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1answer
270 views

Trade-offs in developing larger engines vs using more smaller engines

Looking to explore the inverse point of this question: What challenges are there for more, smaller liquid fuel engines instead of one large? As stated in the answer to the above question, fewer, ...
4
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1answer
184 views

Why were later Russian engines inferior to the NK-33?

In terms of thrust-to-weight ratio the NK-33 engine developed for the Soviet N-1 rocket was by far the best in the world at the time, with a thrust-to-weight ratio of 137. But subsequent Russian ...
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0answers
134 views

Would this 'hybrid expander cycle' engine be practical?

This is another attempt at making closed expander cycle a bit more efficient (the first attempt was here). The design combines some elements of both the open and the closed expander cycles (hence the "...
4
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1answer
2k views

How to seal the connection between the combustion chamber and outer shell in this rocket engine model?

Here is rocket engine drawing. The combustion chamber made from copper and the outer shell from stainless steel. The coolant, either water or gasoline will be between With either pressurised water or ...
2
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0answers
92 views

How is this engine put together? [duplicate]

I'm going through How to DESIGN, BUILD and TEST SMALL LIQUID-FUEL ROCKET ENGINES and am confused how their sample engine is physically built together. This is a picture of their assembly where the ...
2
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1answer
1k views

Problems with the “How to Design, Build and Test Small Liquid-Fuel Rocket Engines” text

For those that have read or consulted the text: How to Design, Build and Test Small Liquid-Fuel Rocket Engines (Rocketlab/China Lake). Otherwise, see steps 10-13 here: https://risacher.org/rocket/...
4
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1answer
149 views

Saturn V and Atlas Engines exhaust issues

This is a follow up question to "Organic Marbles" answer to my earlier question about the atlas rocket exhaust nozzle, regarding the Apollo F1 thrust nozzles having metal baffles/fins inside to ...
9
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1answer
821 views

Atlas Rocket Burning Hose

I was just watching The Right Stuff for the 100th time,and I've always wondered what is that hose spewing flame/burning propellant out of the bottom of the rocket. It's definitely not an engine,and ...
3
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1answer
180 views

Why is ESA developing the Vinci engine rather than buying RL10Bs?

The Vinci engine seems very very similar to the RL10B. Both are hydrolox expander-cycle engines with 465 s Isp and extendible nozzles with a ~250:1 expansion ratio. The biggest difference is that the ...
14
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1answer
798 views

Why aren't expander cycle engines used on lower stages?

Looking at the simplicity of BE-7, I was wondering why dual closed expander cycle engines are not used more commonly and, as far as I know, are not used as lower stage engines at all. A commonly ...
9
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2answers
566 views

As of January 2020, what is the single longest duration firing executed with a Raptor engine?

Can someone cut through the woo for me? As of January 2020, what is the single longest duration firing executed with a Raptor engine? Have any successfully run for full mission duration? Sourced ...
4
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1answer
263 views

What percent of fuel is consumed in powering the turbopumps? [closed]

The RD-170 consumes 5,300 lbs of fuel per second, including oxidizer. The turbopump produces 230,000 hp. If one assumes that roughly 1 lb of fuel is required to generate 1 lb of thrust (obviously this ...
0
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0answers
142 views

How do toroidal and linear aerospike nozzles compare?

What are the pro's and con's of toroidal and linear aerospike engines with respect to each other? When does one choose one design over the other? A linear aerospike is characterized by multiple ...
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 ...
3
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1answer
227 views

Why did the Agena-D leak oxidiser when starting its engine?

The Agena-D upper stage, although extremely reliable, had a tendency to leak some of its RFNA oxidiser when starting its Bell 8096 engine; although not a problem for a stock Agena-D, it did cause ...
29
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3answers
8k views

Why doesn't the US use European rocket engines?

US Companies have been using Russian rocket engines for their rockets for a long time, even during sanctions. But as I was going through the European rocket launches, I felt European rocket engines ...
0
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2answers
240 views

Why was the reusability of the SSMEs so poor, and why was this considered acceptable given their purpose to launch a reusable vehicle?

The Space Shuttle Main Engines operated for around 8.5 minutes in every Shuttle launch, yet were removed from the orbiter after each flight and went through an overhaul, parts often being traded from ...
4
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1answer
103 views

Quantitative plots of v, T, p, vs position from chamber through nozzle to ambient for a few canonical modern engines?

In this answer I showed the schematic diagram of a basic de Laval nozzle and representative plots of how temperature, pressure and and velocity would behave. It can be used as a rough representation ...
2
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2answers
191 views

Would a nuclear turbojet with a chemical afterburner be a suitable intermediate between a pure nuclear turbojet and a nuclear thermal rocket?

NOTE: This is not the place to question the fundamental viability of nuclear propulsion in aircraft and spacecraft. For context, in a spaceplane, the higher speeds you can attain under air-breathing ...
30
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3answers
5k views

Why cool engines with fuel as opposed to oxidizer?

As I was watching Tom Mueller describe the Merlin engine, he said that the RP-1 propellant is pumped through ribs in the nozzle to regeneratively cool the engine. Also, a video about Copenhagen ...
15
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1answer
3k views

Why was the Apollo CM main engine thought to be unreliable on Apollo 13?

When Apollo 13 had most of its internal systems destroyed by an explosion, NASA decided that the best course of action would be to fire the main engine on the dark side of the moon to send the capsule ...

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