Questions tagged [engine-design]

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

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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 ...
13
votes
1answer
2k 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 ...
0
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1answer
61 views

What is a typical sea-level engine nozzle/expansion ratio? What about vacuum engines?

On a sea-Level engine, what is the average nozzle ratio? What about an upper-stage vacuum engine?
3
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5answers
1k views

Could rockets launched from the ground use wings in the stages?

Could a slower or smaller rocket take advantage of lift if all the stages had wings? Could the stages reduce splashdown impact forces by using a spinning seedpod-like design (as shown in the image ...
26
votes
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, ...
2
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0answers
38 views

Deep throttling in sea level engines

In this excellent answer, asked for merlin engines deep throttling in first stage and produced here. To help you understand where the cross over point is, here is some math for understanding the ...
25
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8answers
16k views

Why aren't linear aerospike engines in common use?

Linear aerospike engines are an old idea that seem so full of promise. Why are they not widely used today by the likes of Boeing, SpaceX, etc.?
9
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3answers
923 views

Why is SpaceX's Raptor's design so simple in comparison to SSME?

What is especially striking to me is how simple Raptor is in configuration compared to SSME. The Raptor doesn't have an LP fuel or oxygen pump. What's even more surprising, if we are to compare the ...
1
vote
1answer
51 views

Why would the ideal mass flow rate be less than that of real life?

Comparing the mass flow rate at the throat using the below theory, I find that the mass flow rate isn't accurate but isn't always larger than that of the engine specs (ideal assumptions ). What ...
2
votes
1answer
114 views

Why did Virgin Galactic decide to use a hybrid engine vs liquid on their space ship?

To me, it seems like their business case is very dependent on rapid reuse. With this in mind, using a hybrid engine that would need to be replaced every flight seems very counter intuitive vs a liquid ...
1
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0answers
390 views

Rao contour nozzle: Calculate throat and exit angle?

The Rao nozzle formula is an empiric formula for a parabolic nozzle used in pretty much all nozzles today. The problem is it depends on the throat and exit-angle of the nozzle, which varies with ...
3
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1answer
111 views

Why does the RL10 engine have a pipe sticking out of the side on the Centaur rocket?

The RL10 is a expander cycle engine so the pipe can’t be for a gas generator.
0
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1answer
54 views

What impacts do the rocket engine cycles have on the sizing of the components and effectively the engine?

For a given performance requirement, combustion pressure, propellant mixture, etc. How can one vary between the various engine power cycles such as gas generator, staged combustion, expander, and how ...
1
vote
2answers
95 views

Is the RD0146 an open or closed cycle engine?

RD0146 has been in the latest family of engines being developed from both Russia and US(Pratt and whitney). However, there is a lack of clarity in estabishing whether the expander cycle engine is open ...
3
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1answer
361 views

What is meant by chamber pressure in rocket engines?

Is "chamber pressure" the pressure at the tip of the injector, or the pressure before combustion inside the chamber, or the pressure after combustion inside the chamber?
3
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1answer
141 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 ...
2
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0answers
42 views

Are there any staged combustion cycle rocket engines under 1000 kN? Is it easier to produce larger engines with this type of engine cycle?

I found that most engines developed with staged combustion cycles are inherently quite powerful. Are there any engines which was developed with the staged combustion cycle with a thrust under 1 MN. ...
2
votes
1answer
100 views

Is it possible for one to adapt engine data for different fuels wrt liquid rocket engines

Liquid Rocket engine design is quite complicated and idealised and assumed theories rarely get sufficient validation. In an effort to verify/validate newer/untested fuels to be used in engine designs, ...
4
votes
0answers
59 views

Maximum speed of rocket propellant flow?

In reading this question (Limiting factors of liquid rocket engine thrust), it prompts me to ask if there is an upper limit in how fast the propellant/oxidizer can be pumped into a combustion chamber ...
1
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1answer
108 views

What parameters drive the development effort and cost of a liquid rocket engine for orbital launchers(LEO - GEO)?

The development cost for a rocket engine drives the cost for a launcher and can be attributed to some basic parameters Apart from the few below, what others may be critical to developing and designing ...
7
votes
2answers
199 views

Do any rocket engines besides the F1 need/require baffles?

The F1 engine required baffles on the injector plate to control combustion instabilities so that it wouldn't blow itself up. Was that unique? Or do other engines also have baffles for the same reason? ...
5
votes
1answer
169 views

What are some of the important parameters to scaling a liquid rocket engine

Liquid Rocket Engines can be clustered together on a stage but their performance, weight and size largely decide and constrain the design of the launcher. Data on the newer smaller launcher engines ...
-4
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1answer
151 views

Magnetic force-driven propulsion system for an interplanetary/interstellar spacecraft

I have come up with a conceptual idea of a magnetic force-driven space propulsion system. What I believe is very unique about this propulsion system concept is that its working principle should not ...
11
votes
1answer
658 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 ...
1
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1answer
106 views

Kerosene engine film cooling

So it is clear that kerosene fueled engines use two fluids for film cooling via injection in the combustion chamber, throat, or nozzle. (That is "true film cooling" and not just a fuel rich outer ring ...
1
vote
2answers
145 views

Saturn I's four outer engines' gas generator exhaust, why not vent to the side like the four inner engines?

At about 04:58 in Scott Manley's new video NASA Might Be Giving Away A Saturn I Rocket - Here's Why I Love This Vintage Booster he says: So the four engines in ...
1
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2answers
108 views

Whats the difference between cryogenic and cryo storable rocket engines

I've read about cryogenic storable liquid rocket engine but since it doesn't refer to its fuel, I want to understand the difference between a cryogenic and a cryo-storable engine. The term cryo-...
2
votes
2answers
122 views

Is it possible to use hybrid propulsion to drive the turbopump?

Turbopump are driven either by a preburner or by an electrical engine (OK this technology is quite new and currently in 2019 only used on the Rutherford engine). If I understand correctly, using ...
0
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0answers
291 views

How was the Stabilo crewed re-entry vehicle supposed to work? A tractor engine with four nozzles?

ARCA Space's webpage for the Stabilo program has a description and an image. Hydrogen peroxide monopropellant? Reaction closer to the crew than the nozzle? With thrust at the top, it seems that ...
1
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2answers
110 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 veracity of nuclear propulsion in aircraft and spacecraft. For context, in a spaceplane, the higher speeds you can attain under air-breathing ...
1
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1answer
223 views

Could a CubeSat be propelled by this low-tech electromagnetic propulsion system?

I have come up with a conceptual idea for a low-tech electromagnetic propulsion system for a CubeSat, and I would like to know if it would create (on a theoretical basis) a net force strong enough to ...
0
votes
1answer
65 views

Could LNG fuel be used to pressure feed itself into combustion chamber?

In pressure fed cycle a high pressure gas tank contents are exhausted into the fuel and oxidizer tanks to essentially push them into the combustion chamber. Could a portion of the fuel from an LNG ...
4
votes
1answer
265 views

Why can't an expander-cycle engine be built to use RP-1 or other non-cryogenic fuels?

The expander cycle family of rocket-engine power cycles involve using waste heat from the engine's combustion chamber and/or nozzle to vapourise some or all of the engine's fuel, and using the now-...
8
votes
1answer
506 views

What is the job of the acoustic cavities inside the main combustion chamber?

I am new to rocket engines. I was looking at an image of RS-25 engine's MCC and found these acoustic cavities, and I want to know how they work. Can somebody please explain their working principle? ...
1
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0answers
197 views

Orbit to Orbit Transport Stage

Would it be faster or cheaper to have a lander, SSTO, and/or SpaceX Mars rocket to rendezvous connect with a more efficient engine or "transport stage" or another lander, SSTO? When the spacecraft ...
-1
votes
1answer
85 views

Was the Titan SRM thrust vs time curve engineered to allow for acceleration switches to initiate staging sequence events?

This answer describes the timing between the Titan III Stage 0 (SRM's) and Stage 1 events. The Titan first stage ignited just prior to SRM separation: Titan Stage I ignition occurs at ...
8
votes
1answer
258 views

Why is multi-spool pump very rare on rockets?

The only one I know of is the LP LOX pump on RD-0120. A multi-spool design is already a default for jet engines, which are basically turbine-driven air pumps. A multi-spool pump can save at least the ...
8
votes
1answer
349 views

Why don't all SSME turbopumps gimbal with the engine?

The SSME low-pressure pumps (both fuel and oxidizer) are mounted to the vehicle structure and don't gimbal. The high-pressure pumps are gimbaling with the engine, so the propellant lines between low-...
5
votes
2answers
109 views

Does adding a nozzle increase peak pressure in a rocket?

If I had two charges of the same solid propellant both in the same geometry and casing, and added a de laval nozzle to one, while the other would have just a simple hole for an exhaust, upon firing, ...
0
votes
1answer
71 views

Exit pressure value for vacuum nozzle [duplicate]

What value of exit pressure should I use in the design equations for a small liquid rocket engine nozzle for 200km-500km operating conditions? Since using zero as a value is not possible or else ...
0
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0answers
47 views

Exit pressure for Rocket Lab Curie engine

What do you think the exit pressure for rocket lab curie engine could be?and the area ratio as well? its a kickstage engine and it is said that it has about 25lbf thrust.
7
votes
5answers
798 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 ...
5
votes
1answer
176 views

What is the requirement of spacer rings in solid rocket motors in sounding rockets?

I saw this report SOLID ROCKET MOTOR DESIGN L-CLASS, here as shown in FIGURE-8, they have charged the motor with grain segments with spacer rings in between. Can`t we charge the motor without any ...
2
votes
2answers
335 views

Would a self-winding watch work in space without gravity?

Could a watch that winds itself with a pendulum work in space with no gravity? Could a pendulum or the self winding part be modified to work off the movements of the wrist in a microgravity ...
1
vote
2answers
587 views

What performance specification would be lower for Krypton than for Xenon in Hall effect thrusters?

The Ars Technica article SpaceX scrubs first attempt to launch 60 Internet satellites [Updated] (found here) discusses the use of Krypton rather than Xenon in the Starlink Hall effect ion thrusters: ...
1
vote
1answer
92 views

What Constitutes A Combustion Chamber?

I have been reading about combustion chambers and noticed they seem to just be an empty space with the fuel and oxidizer coming in one end and the nozzle at the other end. If the shape below were ...
6
votes
1answer
298 views

Understanding Von Braun's Math: Theoretical Isp

I've just read Wernher Von Braun's Project Mars: A Technical Tale, and I'm trying to understand the math in the back. I can follow some of what he's doing, but other parts I just can't tell where his ...
4
votes
1answer
181 views

Could a chemically propelled craft travel directly between Earth and Mars spaceports?

If in the near future we manage to build out some infrastructure in space--including robotic asteroid mining so that we can get water without pushing it up a gravity well--are LOX/LH2 rockets powerful ...
3
votes
0answers
94 views

Why did the nozzles on the SRB's igniter initiator point toward the grain of the main igniter while the main igniter's nozzle pointed straight down?

How did the shuttle designers make those decisions? What made it a better decision to point the exhaust of the igniter initiator toward the main igniter's grain at an angle? What made it a better ...
4
votes
1answer
1k views

What are the two very large “blue” cylinders attaching to the combustion chamber of each Rutherford Engine?

The NASA Spaceflight article Rocket Lab’s Electron rocket set for inaugural flight from New Zealand mentions the upcoming opening of a 10 day launch window: Rocket Lab, a U.S.-based launch service ...