Questions tagged [engine-design]
Questions regarding the design or design process for a propulsion system.
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Can coking be avoided by pumping fuel after shutdown?
As I understand it, coking in kerolox engines occurs when the engine shuts down and fuel flow stops, causing fuel still in the coolant channels to overheat and decompose.
Can this problem.be avoided ...
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Does an overexpanded nozzle behave like a suction cup?
It is generally said that, to obtain optimal specific impulse, a nozzle should be just the right size that the exhaust pressure is equal to the ambient pressure. Quoting this answer, a relevant ...
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What are the major tradeoffs for a launch vehicle having either one 400 kN engine or eight 50 kN engines?
Given the problem of choosing to build and launch a small rocket to put a smallsat into orbit with either of these two configurations, what are the major tradeoffs between them?
For specific issues ...
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What was the exhaust pressure of the Saturn V? [duplicate]
I am trying to write some code to simulate rocket launches, and I am doing a proof of concept using the Apollo 11 as a model, to fill my values. When calculating thrust I am using the equation:
F=m⋅Ve+...
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How to calculate the tank boost system for the displacement feed system?
There is a liquid rocket engine running on two components: highly concentrated hydrogen peroxide and kerosene, fuel vapor is ...
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Combustion stability for the second stage of Sea Dragon
I was listening to a video about SHLV's (Super Heavy Launch Vehicles), and Sea Dragon's first stage engine was mentioned.
In terms of combustions stability, the suggested fix would be large combustion ...
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Rough values for the staytime or characteristic length of the combustion chamber of an oxygen/methanol rocket engine?
I'd like to have some idea of the staytime or characteristic length of the combustion chamber of an oxygen/methanol rocket engine.
Are there sources for this, or a way to estimate it?
I've tried, but ...
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Contraction Ratio Impact on Performance for Liquid Rocket Engine
How does one go about calculating the necessary contraction ratio (combustion chamber/nozzle throat cross sectional areas) of an engine with these parameters known...
thrust
nozzle throat area
mass ...
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Multi-stage combustion products?
Okay so I've never seen anything about this before, and that's probably for a very obvious, very simple reason I am far too dim to think of, but here goes:
Most combustion reactions in rocket chambers ...
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How to find the correct size and angle for a conical nozzle on a rocket engine? [closed]
So I need to know the equations for finding the size and angle for a conical nozzle. I am making a rocket engine and I decided the conical nozzle would be the easiest to build. The rocket is going to ...
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How do spacecraft protect their engines from micrometeroids?
A meteoroid impact on an engine bell can easily rupture a coolant pipe. Or it can create an imperfection in the backing plate from where cracks can form. Or it can destroy an injector. All of these ...
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SSME/RS-25:; Why arent high pressure and low pressure pumps coaxial?
The Space Shuttle Main Engine low pressure pumps to prevent cavitation at the main pumps. This pumps were driven by separate turbines fed by high pressure fluid from the main pumps. Why? It just adds ...
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SSME/RS-25: why seal between LOX pump and preburner?
Both the the fuel and oxidiser preburners ran fuel rich. In order to prevent the preburner gas from entering the LOX pump and blowing it up, they had this complex double seal with a gas purged void in ...
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Why will the Raptor not face the same turnaround issues as Space Shuttle engines?
The RS-25's notoriously slow, expensive turnaround was blamed on its complexity. The Raptor appears about as complex.
Both use regenerative cooling.
Both use preburners to drive turbopumps.
While the ...
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How does SpaceX Raptor deliver a more benign turbine environment?
Raptor has been claimed to be able to deliver "long life ... and more benign turbine environments".
https://en.wikipedia.org/wiki/SpaceX_Raptor
The Raptor has hot oxygen flowing out of the ...
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Does methalox fuel have a coking problem at all?
Methane was chosen for SpaceX Raptor because it has less coking problem that kerosene. But does it completely eliminate it? If not, how much less severe is it?
I googled 'thermal decomposition of ...
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Can a spinning water film cool an engine cheaper and better than ablative?
Ablative cooling us an incredibly simple way to cool a liquid rocket engine, when compared to regenerative cooling. But ablatively cooled engines are (presumably) hard to refurbish.
Why not inject a ...
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Do smaller engines have a higher thrust to weight ratio?
For a given chamber pressure and shape,
thrust is proportional to nozzle area, which is proportional to the square of dimensions
mass is proportional to the volume, which is proportional to the cube ...
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Why do the Titan SRBs have an angled engine bell?
Looking at pictures of Titan rockets with solid rocket boosters, the bell is at an angle. Why would they do that?
https://historicspacecraft.com/Rockets_Titan.html
https://en.wikipedia.org/wiki/...
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Recent GPS III Launch Intended or Unplanned Venting?
Between 14:01 and 14:14 in the following video, there is a significant gas vent happening behind the engine bell:
Is this working as intended, or does that appear to ...
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What is a bimodal or multimodal space rocket engine? Especially a nuclear-powered one?
I can't seem to find a specific answer anywhere....
I wonder if it means using the radioactive fuel to power the electronic equipment, purely via natural decay, but also using the same fuel to power a ...
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Why did the Soviet Union decide to use 30 small engines instead of a few large ones on the N1?
The N1 was a big disappointment after exploding on every single launch attempt. From what I have read, it seems like most of the attempts went wrong because one of the 30 engines exploded causing a ...
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How to find the average ambient pressure during rocket ascent?
I am trying to find the average ambient pressure that my rocket will flight through during its ascent to then determine the most optimum conditions in my combustion chamber and nozzle.
I have ...
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Equations evaluating engine performance
What kind of equation would best evaluate a rocket engine's performance in foreign atmospheres such as Mars?
Does it matter that specific impulse does not consider air resistance? Should I focus on ...
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What engine cycle does the RS-88 and its hypergol derivative use?
A comment on this question Orange lines coming from rocket engine nozzle? stated in part
The RS-88 is not a full flow engine and there is not a visible bypass exhaust. ... Perhaps they eject the ...
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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 ...
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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 ...
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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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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 ...
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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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