Questions tagged [engine-design]

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

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Is there a significant reason why pintle injectors are only used in single configuration?

All of the resources I've managed to track down thus far about pintle injectors concern engines which only use a single, large central pintle for the entirety (or vast majority) of propellant supply ...
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8 votes
1 answer
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What is the purpose of the shrouds surrounding these rocket engines?

While researching the purpose of some rocket engine components, I came across several images of perforated shrouds surrounding the combustion chambers of rocket engines. I was highly curious about ...
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4 votes
1 answer
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Do monopropellants have a characteristic length?

I was reading about calculating thrust chamber geometry, and a key tool seems to be the characteristic length, L*. The engine I'm modelling (hypothetically! please don't take down the question) uses ...
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7 votes
0 answers
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What are the negatives associated with Thrust-augmented Nozzles aka Afterburning Rocket Engines?

An interesting comment here introduced me to the concept of Thrust-augmented Nozzles aka Afterburning Rocket Engines. The pubs I've read on it so far introduce the concept as a way to provide good ...
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3 votes
1 answer
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Insights about launch vehicle engine configuration

When dealing with launch vehicles (specifically heavy lifters), there have been a number of different mindsets in terms of engines. The Saturn V used some absolutely massive engines, which was great ...
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Reference request: Rocketdyne Document R-3896-4 "F-1 Rocket Engine Illustrated Parts Breakdown"

Various sections of the Rocketdyne F-1 document R-3896 can be found scattered about the web, but I can't find R-3896-4. It's described as R-3896-4 F-1 Rocket Engine Illustrated Parts Breakdown This ...
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4 votes
1 answer
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Discrepancy in local Mach behavior between CEA and other sources

I'm exploring some designs using the NASA CEA (Chemical Equilibrium with Applications) code and I ran into a discrepancy between CEA predicted values for local Mach number at the exit plane and values ...
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1 answer
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Would pressure oscillations at the inlet of a liquid engine turbo-pump subside at the outlet, or would they get amplified?

Would pressure oscillations at the inlet of a liquid engine turbo-pump subside at the outlet, or would they get amplified? What are the factors that decides the change in the amplitude of pressure ...
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How is a desired chamber pressure achieved in a liquid rocket engine

Before everyone responds that this has been asked before, I have read through every relevant post I could find here and believe my question has not been clearly covered. I also understand that "...
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3 votes
1 answer
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Where do the numbers 101,972 and 3,600 come from in terms of Thrust-Specific Fuel Consumption (TSFC or SFC)?

Online, on sites such as Wikipedia's for Specific Impulse and Thrust-specific fuel consumption, there are these units: 101,972/x g/(kN·s) and 3,600/x lb/(lbf·hr) Perhaps 3600 comes from the number of ...
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-2 votes
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Would the ship using the Alcubierre drive need to use conventional propulsion to move during warp? Or would the space-time "wave" push it?

I have found various explanations on how the warp drive works. And right now I'm confused. First I thought warp drive works by expanding space-time behind you, and contracting it in front of you. I ...
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3 votes
2 answers
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From which NASA publication originates/where can I find the color version of this SSME flow diagram?

Sorry to ask such a similar question as the last one, but I already marked that one as answered. My friend who works at the Endeavour exhibit in LA found this diagram left on the ground after a ...
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6 votes
1 answer
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What limits pressure buildup in SRB's?

According to st. Robert's Law, propellant burn rates increase with pressure. When an SRB is ignited, propellant starts to burn, making the pressure rise in the combustion chamber. The flow through the ...
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Rocket Lab Archimedes engine injector and reusable charecteristics [closed]

From what has been said, the Archimedes engine isn't particularly ambitious WRT its ISP, however Rocket Lab have said it would be highly reusable, which is interesting. Does anyone know of any special ...
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4 votes
3 answers
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How to read this Cassini Main Engine Operating Box (oxidizer vs fuel tank pressures)?

The extremely cool NASA JPL video Triumph at Saturn (Part I) is really worth a watch and/or listen. At about 34:32 it covers the period just before SOI (Saturn ...
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7 votes
2 answers
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How "big" is a 2 megawatt preburner?

Reaction Engines recently announced a milestone completion in their SABRE development program: we have tested the engine’s advanced hydrogen pre-burner at energy delivery levels in excess of two ...
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A question about Nozzle/Extension/Skirt Size

In many rocket engines i see that the thrust chamber and a small part of the nozzle are one piece. Does anyone knows if there's a formula which determines what portion of the nozzle is A ? and how ...
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2 votes
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Does electric fuel pumping scale well for rockets?

The Electron launch vehicle first stage has nine Rutherford engines In addition to adapting the single-engine-out-friendly nine engine configuration from the Falcon-9, the rocket carries a significant ...
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3 votes
1 answer
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How Intuitive Machines' engines "crank out unmatched performance in the space domain" allowing "transit of Van Allen belts once, unlike competitors"?

According to https://www.intuitivemachines.com/propulsion LOX/Methane Engines Our LOX/Methane engines are unique for in-space propulsion, in that they offer safety in handling and testing here on the ...
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What "unique control system" modulated GOCE's thrust to compensate for variable atmospheric drag? How did it know how to modulate it?

This answer to How much time did the longest maneuver last? says: The GOCE satellite mission (Gravity Field and Steady-State Ocean Circulation Explorer) lasted 55 months (4.6 years) of largely ...
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2 votes
1 answer
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Fan powered turbo-pump for low altitude/missile engines

There are many different liquid rocket engine power cycles, forxing propellant into the combustion chamber with tank pressurisation, gas generators, and heat exchangers, amongst others. Instead of ...
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6 votes
1 answer
198 views

Does anyone know the stay time, or what characteristic length should be used, for a LOX/LCH4-fuelled rocket engine?

Just what it says on the tin. I need to know either the "stay time" (Ts) or characteristic length (L*) that would be used to figure combustion chamber dimensions used with a LOX/LCH4-...
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2 votes
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Calculating total burn time for a rocket under constant acceleration with two propellant consumption rates

I tried posting this question on the Physics side of StackExchange but didn't get any response after a week, presumably because it was lost within the broadness of physics in general, so I'm hoping ...
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1 answer
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Does a cryogenic liquid propellant engine exist capable of using multiple fuels?

For example, a rocket engine which can use both liquid methane and liquid hydrogen.
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3 votes
1 answer
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What makes CAPSTONE-1's eight hydrazine thrusters so "super small, high-performance"? How do they work without any tank pressurization?

The NASA Ames Feature Innovative Propulsion System Gets Ready to Help Study Moon Orbit for Artemis says: CAPSTONE’s journey to the Moon will take about three months, starting with its launch to low-...
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3 votes
0 answers
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Making sense of rocket engine thrust calculation [closed]

Recently I've been trying to design a hypothetical rocket engine using the mass flow rate, exit mach, temperature, and pressure calculations provided by NASA's own website. I've come to know quite ...
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5 votes
0 answers
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Tory Bruno mentioned "unsolvable combustion instability" of "large methane engines". What, why, how?

Relevant tweet, an hour ago: https://twitter.com/torybruno/status/1405210138189864960?s=19 a Tweeted Question: Why wasn't methane used in the 2000s, when it was readily available unlike the time ...
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1 vote
1 answer
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If building a liquid propellant rocket engine, with bi propellants, how does the dimensions of my Combustion chamber, affect the efficiency?

If building a liquid propellant rocket engine, with bi propellants, how does the dimensions of my Combustion chamber, affect the efficiency ? but also what is the best C* dimensions for an earth sea ...
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2 votes
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Designing a catalyst for use in catalytically hypergolic fuel mixtures using nitrous oxide

The use of hydrogen peroxide with hydrocarbons such as RP1 has long been a popular choice, not least of all for its hypergolic properties when paired with a catalyst bed. This motor design, catalysing ...
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4 votes
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What are the various ways that hybrid rocket engines are "turned on" or ignited?

I want to know the more complex side of hybrid rocket engines. I already know most of the basics like Newtons third law and oxidizer. But I want to learn more of the complex stuff. I know they are &...
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12 votes
1 answer
3k views

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?

Question: 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? Are there fundamental engineering ...
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14 votes
1 answer
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Why did each F-1 engine have dual fuel feedlines?

Each F-1 engine had two fuel feedlines connecting it to the fuel tank as shown in these contemporary photographs and drawings. The corresponding LOX system only had one feedline. The engine had a ...
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2 votes
1 answer
163 views

What expansion ratio is the best for mars surface level engines?

What expansion ratio is the best for mars surface level engines? For launches from Earth, first stage nozzles are much shorter than second stage nozzles because of Earth's high sea-level pressure. For ...
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2 votes
1 answer
129 views

What was the volume of the Rocketdyne F-1 engine's main combustion chamber?

In the specifications of the F-1 available online, I can find its dimensions, weight, thrust, etc. but I couldn't find what was the volume of its main combustion chamber. Is this information available?...
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How could I find the pressure and/or the Isp at the exit of a rocket nozzle if I have data for the throat and comb. chamber?

I've been looking at this for some time and working with CEA which will only give me data points for the pressure, temperature, Isp, etc. for the Injection, Combustion Chamber End, and the Throat; but ...
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2 votes
1 answer
83 views

Need help on rocket nozzle equation

I saw this earlier post about a guy who needed help with his equation, but I was wondering about how they got one of his numbers. They said that their foot-pound/pound/degree Rankine (the gas constant ...
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1 vote
0 answers
58 views

Pressurant gas line design considerations

I am trying to understand the constraints on pressurant gas line sizes and lengths. For a static volume, the lines can be small in diameter because there is no significant flow velocity and therefore ...
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3 votes
0 answers
109 views

Injector design - LOX vs nitrous oxide

What will be the main design differences between using liquid oxygen and liquid nitrous oxide as oxidizer in a bi-propellant rocket engine? What liquid/gas properties (vapor pressure etc.) play the ...
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3 votes
1 answer
727 views

Open source liquid rocket engine

Is there an open source bi-propelant liquid rocket engine that would have all the documentation, computations, test results and 3D design files (CAD) freely accessible?
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2 votes
1 answer
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Potential Fusion Drive system calculation issue

I will start off by saying that this is an entirely hypothetical drive system with plenty of handwaving and optimistic physics. My question I think is fairly simple and may just be something that ...
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5 votes
1 answer
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How is the pressure within the gas generator determined?

The fact that pressure fed engines need their tanks to be at an even higher pressure has always confused me a little, but it's got me thinking; does the same logic apply to gas generator engines. If ...
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4 votes
1 answer
137 views

Is there a relation between combustion instabilities and chamber pressure?

Is there a relation between the combustion chamber pressure, and either an increase or decrease in both high and/or low frequency combustion instabilities. If so, how has this influenced engine design,...
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3 votes
1 answer
121 views

Cooling the nozzle extension of a nuclear salt water rocket (NSWR)

The nuclear salt water rocket(NSWR) uses a plutonium salt (at least to my understanding) dissolved in water as its fuel. The mixture is kept stable by filling the fuel tank with boron carbide, which ...
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3 votes
1 answer
532 views

ISP losses associated with exhaust vane TVC

What is the impact of exhaust vanes, such as those in the A4 and Redstone rockets, on exhaust velocity and overall ISP? As well as this, what is the relationship between ISP losses and the width of ...
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3 votes
1 answer
63 views

attitude thrusters sharing a common combustion chamber

Most smaller satellites and other larger but simpler space craft with a less demanding mass fraction tend to use cold gas thruster, importantly with a common or as few as possible pressure vessels, ...
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4 votes
1 answer
271 views

What were/are the stingiest and most generous vacuum nozzle? (records for the smallest and largest expansion ratios)

Vacuum nozzles are huge compared to their sea-level or atmospheric counterparts, as can be seen by comparing the first stage engines on an Electron or Falcon-9 to their second stages, where a big ...
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5 votes
1 answer
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Are nuclear thermal engine designs limited to about twice the Isp of existing chemical rocket engines? If so, why; what's the limiting factor?

Discussion below With Ultra Safe Nuclear engines and hydrogen propellant, how far to Mars could you get and still be able to return to Earth in an emergency? including a comment that suggests that the ...
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1 vote
0 answers
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Why are rocket engines shaped like a bell rather than a gun barrel? [duplicate]

When blasting matter out of a spacecraft engine for thrust, it seems like you'd want as much velocity in one direction as possible. Why do spacecraft engines (e.g., Apollo CSM) have big bell-shaped ...
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3 votes
1 answer
279 views

Rocket engine with lowest Isp to reach orbit

Which engine with the lowest possible specific impulse has reached orbit propelling a given rocket? There is a page at Wikipedia that compares orbital engines but some engines are missing Isp value ...
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4 votes
1 answer
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Ultra Safe Nuclear Technologies (USNC-Tech) has delivered a design concept to NASA, but what does NASA consider a "design concept" to be?

The 19-Oct-2020 Press Release Ultra Safe Nuclear Technologies Delivers Advanced Nuclear Thermal Propulsion Design To NASA begins: SEATTLE, Oct. 19, 2020 /PRNewswire/ -- Ultra Safe Nuclear ...
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