Questions tagged [engines]

Questions regarding equipment used to propel a spacecraft or a rocket. Questions about attitude control jets should be tagged "attitude".

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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 ...
Organic Marble's user avatar
8 votes
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536 views

Is thermal soakback from the engine a problem for rocket stages? Especially ones that complete several burns over several hours (e.g. S-IVB, Centaur)?

Thermal soakback is a phenomenon whereby a hot, operating engine transfers heat into the spacecraft, usually conduction through the engine mounts. I've only ever seen this problem discussed with RCS ...
dasvitek's user avatar
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Would we include the main engine shield if we were designing the Cassini orbiter today?

The Cassini spacecraft flew two bipropellant main engines for major trajectory changes, each with a nominal thrust of 445N (100 lb for us Americans). The engines were located at the aft end of the ...
John McCarthy's user avatar
7 votes
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197 views

What performance can be expected from chemical rockets under Venusian atmospheric conditions?

Is it feasible to use either solid or bipropellant liquid rocket engines to lift off from the surface of Venus? "Reference datum" air pressure on Venus is around 9.3 MPa; even on the top of, say, ...
Russell Borogove's user avatar
6 votes
0 answers
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What are the various ways that rockets measure the instantaneous thrust of each engine?

@DavidHammen's answer to Engine failure: how to detect? mentions thruster sensors. This intrigued me and so I thought I'd ask about how this is done. Thrust is a critical parameter to know in real ...
uhoh's user avatar
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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 ...
Anonymous Person's user avatar
5 votes
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180 views

Orange lines coming from rocket engine nozzle?

This image of a test-fire of the RS-88 ethanol/LOX engine from Wikipedia. It is apparent that there are these orange lines extending from inside the nozzle into the plume. What is it, and why is this ...
WarpPrime's user avatar
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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 ...
Sebastyen Laroche's user avatar
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266 views

What is this ring-shaped part falling from Starship SN9 after launch?

The picture shown is a screenshot during the recent launch of SpaceX's SN9 from a live stream, and I noticed that a black ring fell off the exhaust/engine. It only shows up for around a frame or two ...
Philip.P's user avatar
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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 ...
Abdullah is not an Amalekite's user avatar
5 votes
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188 views

Why does kerosene need inducer?

We see inducers before the main kerosene turbopump in engines such as F1 and RD180. Given the property of kerosene having extremely low vapor pressure (~0.007 bar around room temperature), is this ...
Meatball Princess's user avatar
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179 views

Why does Orion's Jettison Motor, have four nozzles but eight Attitude Control Motors arranged in an octagon?

Spaceflight 101's Orion Spacecraft Overview shows the following tests for the escape system. Why are there eight ACS thrusters arranged octagonally? Is it just to reduce cosine losses or does this ...
uhoh's user avatar
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301 views

Purging process of a rocket engine

Does spacex purge Falcon 9 engines after landing ? If so, which gas is used for purging?
Vasanth C's user avatar
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1 answer
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What is the O/F mixture ratio and the ISP for the SuperDraco Engine by SpaceX?

Is it safe to assume a mixture ratio of 2.16 with an ISP of 313 s for the NTO/MMH, SuperDraco Engine manufactured by SpaceX? I am referencing the 2.16 propellant mixture ratio, and estimating or ...
user28833's user avatar
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What are the arms for under the nozzle of NASA engine tests?

When NASA tests rocket engines at the Stennis Space Center, the engines have two arms under the nozzle. When the engines start these arms swing out of the way of the exhaust. What are these arms for? ...
Tom's user avatar
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How is the stainless-steel tubing in rocket engines brought into the correct shape?

Some American rocket engines have TCA's (thrust chamber assemblies) built after a certain scheme: A combustion chamber, including part of the nozzle, made of several dozens of stainless steel tubes ...
Angel Sachse's user avatar
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171 views

What is the largest number of rocket engines ever successfully used on a single craft as of 2022?

A fully stacked Starship was rolled to the pad this week for testing. The byline caught my eye, though (emphasis mine) SpaceX moves a massive rocket with 33 engines to its launch pad for tests No ...
Machavity's user avatar
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How many turbine blades, engine seals and bearings do reusable rocket engines have and how are they inspected?

From previous year statements of SpaceX representatives, the most difficult and longest part of used F9 booster refurbishment are inspections of the most volatile parts of the booster's nine Merlin ...
David Cage's user avatar
4 votes
0 answers
126 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 ...
user3184199's user avatar
4 votes
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203 views

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 ...
SE - stop firing the good guys's user avatar
4 votes
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164 views

Cooling an aerospike spike via "fuel diversion"?

My question is, could an aerospike be cooled via diverting a very small quantity of your fuel (fuel used since it has a higher heat capacity than oxidizer and won't, you know, turn your engine into an ...
YuccaWorks's user avatar
4 votes
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70 views

Atmospheric retro-propulsion performance of aerospike nozzles?

I’m thinking about the use of single toroidal aerospike engine for a reusable upper stage with propulsive landing capability and this question came to mind. Do aerospike nozzles even capable of retro ...
Aungmyintmyat Hane's user avatar
4 votes
0 answers
381 views

How do single-nozzle staged combustion rockets control roll?

Related: How do single engine rockets control roll? While many single-nozzle rockets are gas generator powered & can deflect the pump exhaust asymmetrically to produce a torque, staged combustion ...
Anton Hengst's user avatar
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What main engine used in a series of environmental satellites has failed more than once (according to the GAO)?

A GAO report on NASA's ongoing projects can be found here. On page 70 while discussing the Lucy mission, it says the ... main engine was the same model used on a series of environmental ...
Organic Marble's user avatar
4 votes
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729 views

If the J-2X is too powerful for SLS, why was it appropriate for Saturn V?

Reading an article about new engines for the SLS (Summary: There is no plan what to do once the current SSME's are expended), they mention that the J-2X is too powerful for the upper stage of SLS. ...
geoffc's user avatar
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3 votes
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146 views

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 ...
Muhammad Ahsan's user avatar
3 votes
0 answers
113 views

How do ablatively cooled rocket engines compare to regeneratively cooled ones, in terms of mass?

Assuming equivalent thrust and single continuous burn duration, is there a figure that roughly tells the difference in mass between these two engines cooling methods? This question focuses on first ...
user721108's user avatar
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3 votes
0 answers
197 views

What is the cause of soot in the plume of the Raptor engine?

Though the Raptor engine burns quite clean, it was clear from some early test flights that it did produce some visible soot: There have been differing explanations for the exact cause of/source of ...
quinnkenri's user avatar
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3 votes
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Why aren't Dual Engine Centaurs used anymore?

The last DEC flew in 2004 (excluding Starliner) on an Atlas II. Why aren't they used today for commercial payloads (again, barring Starliner)? I understand that DEC is more expensive than SEC as it ...
WarpPrime's user avatar
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3 votes
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99 views

(Possibly fictional) Can you locate this mysterious Project Orion design with NERVA engines as RCS?

Some years ago, I happened to see a drawing of a hypothetical Project Orion (the Nuclear Pulse Propulsion one) type spaceship, that had the notable (and highly questionable, IMO) feature of having a ...
ikrase's user avatar
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3 votes
0 answers
139 views

Why are hydrogen pumps much more powerful than oxygen pumps in rocket engines?

In many rocket engines I've seen, hydrogen pumps seem to be 3 - 4 times more powerful than oxygen pumps while pumping about 5 times less mass. Why is that? Part of this is probably driven by relative ...
irakliy's user avatar
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3 votes
0 answers
432 views

Can expander cycle engines fueled by methane or propane be practical?

It seems like all expander cycle engines currently in operation or in development use liquid hydrogen as fuel. The answer to this question indicates that RP1 won't work for EC engines because of its ...
irakliy's user avatar
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3 votes
0 answers
411 views

Problems with shutting off "torch igniter" during the operation of combustion chamber

With reference to the presentation pp 76, where SSME's Augmented Spark Igniter is said to have their flame "On" even after the main combustion chamber ignition, is to prevent the blowback from the ...
Vasanth C's user avatar
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3 votes
0 answers
226 views

Why would "Breakthrough Starshot" need photon thrusters?

Found here (italics added, bold in source): Nanocrafts are gram-scale robotic spacecrafts comprising two main parts: StarChip: Moore’s law has allowed a dramatic decrease in the size of ...
user721108's user avatar
  • 4,290
2 votes
0 answers
102 views

Help with designing nozzle geometry for compressed air thruster

I am designing a compressed air thruster with a conical nozzle geometry. The general design consists of a compressed air tank, pneumatic tubing, and then the actual chamber with the nozzle. The ...
Kyle's user avatar
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2 votes
0 answers
106 views

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 ...
Abdullah is not an Amalekite's user avatar
2 votes
0 answers
964 views

What is the difference between a spin up test and a spin prime test?

What is the difference between a spin up test and a spin prime test? And if there is no difference, why not just use the first of those two terms, it being more descriptive?
tedtoal's user avatar
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2 votes
0 answers
94 views

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 ...
Organic Marble's user avatar
2 votes
0 answers
122 views

How unusual is it to test vacuum engines at sea level?

How are vacuum optimized engines tested without disintegrating them? is an excellent question as it's attracted quite a number of informative and diverse answers. @Uwe's answer informs us that there ...
uhoh's user avatar
  • 149k
2 votes
0 answers
86 views

What happens to ablative nozzles after a test fire?

For example RS-68 engine If you make a test fire of an ablative nozzle engine then the fire will consume the coating of that nozzle. That means you have to replace the coating or the entire nozzle. ...
Joe Jobs's user avatar
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2 votes
0 answers
64 views

What are the nuclear energy challenges specific to the moon?

What are moon specific hurdles to a fission reactor? low gravity no atmosphere Apparently it's more difficult to shed heat in a vacuum. Are some coolants more advantageous on the moon than others? ...
Nicholas Saunders's user avatar
2 votes
0 answers
42 views

Anyone know of a "N71" Hall Effect Thruster currently in production or development?

In a NASA Goddard Q&A transcript for an upcoming proposal, the NASA representative mentioned that the mission designers were considering the "N71" Hall Effect Thruster as an option for an upcoming ...
Terrance Yee's user avatar
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2 votes
0 answers
57 views

Real-Time Launch Statistics for the Demo-2 Mission

Is it possible to view the statistics such as pounds thrust and pressure of the Dragon Spacecraft's engines in real time. I'm not sure if Space-X or NASA has a part of their website dedicated to this, ...
mbezos1996's user avatar
2 votes
0 answers
302 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 "...
irakliy's user avatar
  • 615
2 votes
0 answers
127 views

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 ...
zephyr0110's user avatar
  • 2,911
2 votes
0 answers
64 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. ...
Rajath Pai's user avatar
  • 1,251
2 votes
0 answers
178 views

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 ...
karthikeyan's user avatar
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2 votes
0 answers
185 views

What are the maintenance benefits of SABRE engine technology for SSTO launchers?

What are the maintenance benefits of the SABRE engine over all the other engines being considered for the propulsion concepts for SSTO Reusable launchers?
Olly's user avatar
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1 vote
0 answers
89 views

Single shaft turbopump vs two turbopumps

What are the pros and cons of using same turbopump for fuel and oxidizer and using 2 different pumps for both?
Rocketsss's user avatar
1 vote
0 answers
114 views

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 ...
PedrohSpaceWolfy's user avatar