Questions tagged [engine-design]
Questions regarding the design or design process for a propulsion system.
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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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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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What modifications constituted the ‘reorificing’ of F-1 engines on later Saturn V flights?
The topic of uprating the Saturn V’s first stage engines appears to have been widely discussed, and yet there is little agreement as to how it was done.
Early Rocketdyne F-1 engines quote lower ...
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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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How much cheaper are pressure fed engines compared to other cycles (e.g. staged combustion, gas generator, electric pump-fed)?
It's well known that pressure fed engines are mechanically simpler, and therefore cheaper than pump-fed cycles (although pressure fed has worse performance). However, I haven't found any sources that ...
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What kind of forces and response times/accelerations are needed to gimbal a mid-sized nine-engine rocket's engines?
This answer explains that the gimbaling actuators on each of the nine Rutherford engines on the Electron rocket are in fact electrically powered DC brushless motors. Currently it's not known if they ...
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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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Low-pressure pump-fed rocket engine?
I saw the above suggested in LEO on the Cheap. In P.130 it says:
A compromise between high-performance/lightweight pump-fed vehicle designs
and cost-optimized pressure-fed vehicles with heavier ...
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Engine configuration for lander
Which is a more stable lander design:
1.Single central engine.
2.Multiple engines located near the corners
Following is the design for Tianwen-1, the Chinese Mars lander:
And following is the design ...
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Does Rocket Lab's Rutherford have margin for uprating with improved battery technology?
We've seen with SpaceX's Merlin engines that the initial design had a lot of headroom for subsequent increases in chamber pressure and mass flow rate (from supercooling and densification) to gain ...
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What is the droplet size that is desirable for pintle injectors?
The pintle injectors tend to generate droplets after impingement of the fuel and the oxidiser stream and I understand that the droplets will be premixed.
In such a case, even a larger premixed ...
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Pulse Rocket Engine
How feasible would a rocket engine that ignited fuel in fast, high pressure pulses be.
This type of engine would be especially applicable for low thrust burns such as for the raising of a small ...
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How much propellant is "wasted" in the gas generator power cycle?
The gas generator power cycle is an open cycle, with pre-burner exhaust vented after driving the turbine instead of contributing to thrust as in more advanced power cycles.
What percentage of the ...
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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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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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What do the RD numbers of Russian rocket engines mean?
Most Russian rocket engines have a name on the form of for example RD-107 (РД-107).
But apart from different engines having different numbers, how is the number chosen?
All RD-2xx engines appears to ...
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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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Why doesn't a regeneratively cooled engine crack due to differential expansion induced by thermal gradients?
A liquid rocket engine with regeneratively cooled chamber walls and nozzles would definitely be one among those components experiencing the steepest thermal gradients (Chamber wall inner - $3000 K$ ...
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Electromagnetic engines in heavy radiation regions
What sorts of peculiarities might affect an electromagnetic rocket (VASIMR or Magneto-Inertial Fusion) crossing Jupiter's radiation belts? Could all of that energy fry a magnetic thrust chamber and ...
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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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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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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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Where would one find information on the fuel properties (temp, max ISP) of non-conventional rocket fuels?
Yesterday's Starship landing saw at least one Raptor burning copper. Given that copper oxidizes with oxygen at the temperatures and pressures found in a Raptor combustion chamber, what properties does ...
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Will you be having rubber or wax with your peroxide? (hybrid engine fuel tradeoffs)
Hybrid engines offer some practical advantages and some budgetary ones that can offset lower ISP, including potentially safer solid fuel to store and non cryogenic storage of some oxidizers like ...
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Can the bleed-off fuel in an open expander cycle be substituted for another liquid?
In all expander cycles, fuel is used as the working fluid to generate the pressure difference necessary to drive the pumps. This makes sense in a closed expander cycle as it'll eventually be used in ...
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Why use nozzle extensions for ULA's Vulcan; why not make them this long in the first place?
This answer to What is the difference between the Vulcan 562 configuration and the Vulcan 5H2 ("Heavy") configuration? explains that the 2nd stage nozzles were modified by extending them, ...
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Merlin combustion chamber pressure
What is the combustion chamber pressure for Merlin?
I mean the average and the maximum
The Raptor engine was tested with a maximum 330 bar. I would like to compare them
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Where could I find more propellant combustion charts for more different/more broad examples/numbers?
So after asking how I could calculate this kind of propellant combustion charts for different fuels/oxidizers and other ratios and other stuff and getting some really good answers, especially from ...
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Storage density of a Deuterium-Helium 3 fusion pellet
in a series I am working on I will be using a D-He3 fusion drive system (similar to the one in the expanse according to Project RHO). I am under the assumption that the fuel will be stored in a pellet ...
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What is the function of this Merlin engine's tube, and why is it getting red hot?
In the video of the recent SpaceX Starlink launch, one view of the Falcon-9 2nd stage engine shows a cane-shaped tube that glows red hot at the "handle" end and seems to get hotter over time....
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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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Hypergolic slugs with gaseous reactants
Based on points raised in this question about hypergolic slugs.
My understanding of a hypergolic slug is that it is a solid or a liquid on a paper patch placed in the combustion chamber and it will ...
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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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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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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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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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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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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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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 "...
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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 ...
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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. ...
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What are some common exit pressures for liquid propellant engines?
Most engines are overexpanded at launch so that they reach peak efficiency at altitude. It’s easy to find values for thrust, specific impulse, expansion ratio, chamber pressure, etc, but I’m trying to ...
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Layout of regenerative cooling tubing?
In F1, and space shuttle engines (I think), the regenerative cooling tubing goes through the inner wall of the nozzle. The russian engines (RD-180 and likes) seem to have smooth inner and outer ...
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How to overcome the challenge of igniting kerosene using spark plugs?
Discussions in this question and its answer, concerning the use of spark plug ignition for Kero/GOx system outlines the energy limitations of spark plugs to ignite the mixture.
But Ignition Transient ...
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Is it undesirable for LOx to splash on the walls of combustion chamber?
Typically, there are annular ports on the injector plate to introduce fuel to cool the combustion chamber. Why is LOx not used for cooling despite it being extremely cold?
Given there will be a lot ...
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Which is preferred for liquid atomization - gas & liquid shear or liquid & liquid shear?
For generating a spray of droplets, liquid need to be disintegrated/atomized through shear forces.
Typical injectors in IC engines and aircraft use shear between gas & liquid at the phase ...
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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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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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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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How is gaseous fuel injected in Raptor engine's combustion chamber?
If liquid fuel and oxdizer is injected in a rocket combustion chamber, the mixture will be moving relatively slow before reaching the nozzle, preventing the flame front from escaping outside the ...
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