Questions tagged [engine-design]
Questions regarding the design or design process for a propulsion system.
259
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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 ...
2
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0answers
43 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 ...
4
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1answer
130 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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110 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
138 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
800 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
152 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 ...
4
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1answer
191 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....
12
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1answer
511 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
530 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
250 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 ...
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0answers
84 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 ...
3
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1answer
201 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 ...
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2answers
186 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 ...
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1answer
77 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?
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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 ...
1
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1answer
56 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
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1answer
121 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 ...
3
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1answer
122 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.
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2answers
101 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 ...
2
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0answers
46 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. ...
4
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0answers
66 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 ...
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1answer
105 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, ...
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1answer
60 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 ...
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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 ...
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2answers
227 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
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1answer
180 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 ...
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1answer
178 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 ...
1
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1answer
111 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 ...
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2answers
161 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 ...
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2answers
132 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
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2answers
128 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 ...
4
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1answer
346 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-...
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1answer
67 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 ...
8
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1answer
516 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? ...
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1answer
230 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 ...
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2answers
167 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 ...
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1answer
92 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 ...
6
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2answers
115 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, ...
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48 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.
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1answer
87 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 ...
5
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1answer
199 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 ...
8
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1answer
269 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 ...
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1answer
93 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 ...
4
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1answer
184 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 ...
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2answers
736 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:
...
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108 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 ...
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1answer
182 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 ...
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3answers
1k 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 ...
8
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1answer
384 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-...
