Questions tagged [engine-design]

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

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What are better ways to deliver heat directly to propellant in a Thermal Rocket design for use in launch than UV such as in the Nuclear Lightbulb?

Most advanced, high-power engine concepts that I came across aren’t suited for atmospheric launch, so I got curious about what kinds of engines could launch a very heavy craft from the surface of a ...
9 votes
1 answer
526 views

What is the area of the SSME nozzle knowing only thrust at sea level and in vacuum?

Looking at the SSME Wikipedia RS-25 Space Shuttle Engines, the data shown that the thrust at sea level ($F_{sl}$) is 1.816*10$^6$ N, while the thrust in vacuum ($F_{vac}$) is 2.278*10$^6$ N. Knowing ...
2 votes
1 answer
57 views

Discrepancies in thrust chamber dimensions for RL10

I've recently been developing some automated scripts in Python for the purpose of calculating engine parameters. I've been using the RocketCEA interface library, which links to NASA's Chemical ...
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3 votes
0 answers
71 views

How Spacex's Raptor Rocket Engine starts?

How does the Spacex Raptor rocket engine start? What are the different stages of startup? Is the propellant pressure in the tanks sufficient to drive the turbopumps and ignite the preburners and then ...
2 votes
0 answers
73 views

Paraffin wax in solid motors

Paraffin wax is often used in (at least hypothetical) hybrid motors, mostly with N2O or HTP. Could it not, however, be used in a conventional configuration? Running at O/F of 12.4, 60 bar chamber ...
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2 votes
1 answer
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Question Deriving Mass Flow Rates for an Engine

I am trying to follow the calculations made in this blog post for a $50$ lbf. IPA/Nitrous Oxide engine, but cannot seem to get the values the author made for their propellant flow rates. Since the ...
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2 votes
1 answer
113 views

Estimations for Gas-Side Wall Temperature Within Rocket Engines

I'm in the process of reading Modern Engineering for Design of Liquid Propellant Rocket Engines and am stuck on this one example given in chapter 4 on the ...
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7 votes
1 answer
991 views

Is there an ultimate break-even point with rocket nozzle length or expansion ratio in a vacuum?

I know that in an atmosphere, you don't want your expansion ratio to be too high, or it will cause some big problems, and that vacuum engines are restricted by the space they have to fit in, but if we ...
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2 votes
1 answer
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How to calculate catalyst bed geometry (length/radius) for a monopropellant thruster?

Catalyst design is central to the development of monopropellant thrusters and hence, ignoring its importance, as I have realised, is not very good practice. My question is if the mass flow rate, bed ...
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4 votes
1 answer
408 views

Inconsistencies in calculating exhaust velocity

I'm quite sure this is either a small or just plain stupid mistake but my anxiety is getting the better of me. when calculating exhaust velocity this is the equation used: however I keep getting ...
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5 votes
1 answer
113 views

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 ...
4 votes
1 answer
171 views

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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8 votes
0 answers
171 views

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 ...
3 votes
1 answer
124 views

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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6 votes
1 answer
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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 ...
4 votes
1 answer
112 views

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 vote
1 answer
48 views

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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4 votes
1 answer
211 views

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 "...
3 votes
1 answer
230 views

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 ...
-1 votes
1 answer
112 views

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 ...
3 votes
2 answers
191 views

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
209 views

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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1 vote
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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
170 views

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
2k views

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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4 votes
0 answers
93 views

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 ...
2 votes
0 answers
125 views

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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3 votes
0 answers
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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
92 views

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
311 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
1 answer
322 views

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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5 votes
1 answer
333 views

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
321 views

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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7 votes
1 answer
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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
147 views

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 ...
2 votes
0 answers
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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
0 answers
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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 &...
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 ...
2 votes
1 answer
173 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 ...
2 votes
1 answer
188 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 ...
2 votes
1 answer
111 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 ...
0 votes
0 answers
63 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 ...
3 votes
0 answers
142 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
987 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
147 views

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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