Questions tagged [engine-design]

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

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26 votes
4 answers
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Does the NK-33 engine require subcooled kerosene so cold that it turns to wax?

It was mentioned in this answer and in several other places on the internet that the kerosene fuel used by NK-33 engines needed to be subcooled enough so that it reached the same density as the LOX, ...
uhoh's user avatar
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36 votes
9 answers
14k views

Why do rocket nozzles flare?

Why do rocket nozzles open wider at the end than, let's say, get narrower? Let me explain: A jet engine works by having this amazing thing called a combustion chamber. The combustion chamber ignites ...
Frank's user avatar
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7 votes
4 answers
2k views

What kind of engine does this Isp = 1600 refer to? Is it cubesat-friendly?

These two good answers (one and two) to the question "Is there a maximum Isp for 'exothermic chemical reaction rockets?'" put the limits around 500-550 seconds for the limits of practical ...
uhoh's user avatar
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5 votes
1 answer
3k views

What are the two very large "blue" cylinders attaching to the combustion chamber of each Rutherford Engine?

The NASA Spaceflight article Rocket Lab’s Electron rocket set for inaugural flight from New Zealand mentions the upcoming opening of a 10 day launch window: Rocket Lab, a U.S.-based launch service ...
uhoh's user avatar
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3 votes
2 answers
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What performance specification would be lower for Krypton than for Xenon in Hall effect thrusters?

The Ars Technica article SpaceX scrubs first attempt to launch 60 Internet satellites [Updated] (found here) discusses the use of Krypton rather than Xenon in the Starlink Hall effect ion thrusters: ...
uhoh's user avatar
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12 votes
1 answer
11k views

Rocket Engine Plumbing: Still don't understand the Full Flow Staged Combustion Cycle

I just found this incredible video KSP Doesn't Teach: Rocket Engine Plumbing and ran through it a few times. It's very helpful in the way it outlines the various issues first, and then designs the ...
uhoh's user avatar
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14 votes
2 answers
3k views

Disposition of the Oxidizer Tank in Rockets with Autogenous Pressurization

A little while ago, Ars Technica did a big story on the Firefly rocket under development. http://arstechnica.com/science/2014/11/firefly-space-systems-charges-full-speed-toward-low-earth-orbit/2/ A ...
AlanSE's user avatar
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13 votes
4 answers
3k views

Do rocket engines have shock absorbers?

With a million pounds of thrust and many g of acceleration and a significant fraction of a g of vibration, connecting the engine to the rocket can't be trivial. At launch the mass is very high and ...
uhoh's user avatar
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11 votes
3 answers
3k views

What are the phases of ignition (and flameout) of a liquid fuel engine?

As I observed ignition of several rocket engines (Shuttle, AMDE, Lynx Suborbital, Saturn V) they all come through a couple phases - emitting various vapors, unfocused flame, etc, before the proper "...
SF.'s user avatar
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33 votes
7 answers
17k views

Why are Rocket engines at the base of the rocket?

I don't know much about Rockets, but all that I have seen, from the Saturn V to SpaceX's Falcon 9 have the engine at the bottom. Doesn't this make the Rocket really unstable, like balancing a pencil ...
Deep's user avatar
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27 votes
8 answers
21k views

Why aren't linear aerospike engines in common use?

Linear aerospike engines are an old idea that seem so full of promise. Why are they not widely used today by the likes of Boeing, SpaceX, etc.?
Travis Bear's user avatar
14 votes
3 answers
4k views

Did any rockets use differential throttling instead of gimbal?

It seems the standard approach to control of rockets during launch is either vernier thrusters, or gimbals on the main engines. Sure that works, and is quite efficient, but I wonder about a simpler ...
SF.'s user avatar
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12 votes
1 answer
988 views

Why does the core stage of the Ariane 5 produce more thrust in vacuum?

In listening to a youtube video that was discussing the Ariane 5, the narrator noted briefly in passing that the Vulcain 2 engine produced more power thrust in a vacuum than it did at sea level. Not ...
RoboKaren's user avatar
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6 votes
4 answers
1k views

Can a solar sail be added to an ion engine and work better?

Has there been a concept vehicle that uses both solar sails and ion engines? Does the added mass of each system increase or reduce the spacecrafts total delta V capabilities? Inspired by S.F. As S.F....
Muze's user avatar
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4 votes
1 answer
2k views

How do you determine what the temperature will be in the combustion chamber of a rocket engine?

I am guessing it is dependent on the fuel and oxidiser and the chamber pressure but is there an equation that would calculate the chamber temperature?
Edward Jane's user avatar
71 votes
10 answers
55k views

Why is SpaceX considering Methane as fuel for their next engine, the Raptor?

Currently, SpaceX has developed the Merlin 1 family (1B (Falcon 1), 1C (Falcon 9 v1.0), 1D (Falcon 9 v1.1/F9-R/Falcon Heavy), vacuum versions and sealevel versions) which are LOX/RP1 based. (75-...
geoffc's user avatar
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12 votes
1 answer
10k views

How are rocket nozzles made?

How are rocket nozzles made?? Is it a huge chunk of metal that they cut down or is it a "pipe" that they reshape? Or something else??
Dat Ha's user avatar
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12 votes
3 answers
12k views

How is chamber pressure determined for rocket engines?

I've been looking for this for quite some time now, and I can't find anything other than calculations where they already assume a chamber pressure. So my questions are two: What are the equations for ...
mariohm1311's user avatar
5 votes
2 answers
5k views

How can phenolic (resin?) handle rocket engine nozzle temperatures?

I just saw @OrganicMarble's survey answer that bravely tackles the wide variety of technologies used to make different types of rocket nozzles. One item caught my eye: Nozzles may also be made of ...
uhoh's user avatar
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5 votes
2 answers
244 views

How to calculate these engine parameters on my own?

I am a space enthusiast and am intrigued mostly by rockets. I recently found a book HOW to DESIGN, BUILD and TEST SMALL LIQUID-FUEL ROCKET ENGINES and have been fiddling around with rocket engine ...
StarshipGood's user avatar
4 votes
1 answer
3k views

What is the 'Summerfield criterion' regarding rocket exhaust expansion

In this answer to Why do the shapes of these two exhaust plumes from an Atlas V 411 look different? the 'Summerfield criterion' is mentioned, saying: Historically, the Summerfield criterion was used, ...
OrangePeel52's user avatar
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2 votes
1 answer
383 views

Could a CubeSat be propelled by this low-tech electromagnetic propulsion system?

I have come up with a conceptual idea for a low-tech electromagnetic propulsion system for a CubeSat, and I would like to know if it would create (on a theoretical basis) a net force strong enough to ...
user avatar
38 votes
6 answers
9k views

Why did it take so long for methane to be used as a rocket propellant?

SpaceX have put methane on the map as a rocket fuel, but they weren't the first to consider its use. The first experiments in building a rocket engine that uses methane date back to 2007. Now methane ...
Hobbes's user avatar
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36 votes
3 answers
13k views

Why are rocket engines operating above 100% often considered nominal?

It was brought to the attention of the community that right before the crash of Antares the commentator noted: "Main engines at 108%" It was noted that other engines were also reported to work at ...
user avatar
33 votes
9 answers
7k views

Is it common and good engineering for a pair of cables to be easily plugged into each other's connectors in modern spacecraft

Space News's Human error blamed for Vega launch failure Analysis of the telemetry from the mission, along with data from the production of the vehicle, led them to conclude that cables to two thrust ...
uhoh's user avatar
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22 votes
2 answers
3k views

Are nuclear-powered engines the way to go for space exploration?

I often think about the future of humanity and how to achieve it. Despite criticism, the USA and USSR achieved significant scientific breakthroughs, such as: putting the first man in space landing ...
Artem Ruchkov's user avatar
18 votes
1 answer
3k views

Why the non-symmetric design of rocket nozzles?

Although I have seen many perfectly symmetric nozzles, I have also seen designs such as this (Virgin Galactic) which is only symmetrical about one axis: Why is this?
Jonny's user avatar
  • 303
15 votes
1 answer
3k views

Why was the Apollo CM main engine thought to be unreliable on Apollo 13?

When Apollo 13 had most of its internal systems destroyed by an explosion, NASA decided that the best course of action would be to fire the main engine on the dark side of the moon to send the capsule ...
user avatar
14 votes
1 answer
3k views

Are MMH and UDMH interchangeable?

Can Monomethylhydrazine and Unsymmetrical dimethylhydrazine be used one in place of another for the class of the existing orbital maneuver engines (with reduced performance may be)? Such as Shuttle's ...
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13 votes
1 answer
1k views

Why does the YF-75D nozzle have such a strong spiral pattern?

Why does the YF-75D nozzle material have such a strong spiral pattern? Is it a result/biproduct of a manufacturing process only, or does it have some specific function? edit: The last, cropped ...
uhoh's user avatar
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7 votes
1 answer
1k views

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 ...
uhoh's user avatar
  • 149k
6 votes
2 answers
2k views

Pro/cons of burning propellant in stochiometric ratio?

Several questions and answers here speak of stochiometric ratio. I do understand it is convinient for efficiency (greater ISP). I also read somewhere (I am unable ro find again the reference, it was ...
Manu H's user avatar
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6 votes
1 answer
401 views

Is there a way to make liquid fueled rockets not lose efficiency with decreasing throttle?

As far as I know liquid fueled rockets suffer from lowered efficiency when using less than full throttle since the pressure of combustion is lowered and so thermodynamic efficiency. Could a variable ...
Krzysztof Broda's user avatar
6 votes
1 answer
368 views

Why do some engines have so many little tubes, and others, not so much?

This comment about the Houston Space Center's Rocket Garden drew my attention to the cropped image below, from that link. I'm under the impression that some liquid propellant engines don't have a ...
uhoh's user avatar
  • 149k
6 votes
2 answers
607 views

How do spherical SRB's compare to long skinny ones? What do their thrust curves look like?

Most SRBs are long and skinny, probably because most are used low in Earth's atmosphere where aerodynamic drag is large. But here are some very short SRBs, one seemingly spherical except for the ...
uhoh's user avatar
  • 149k
3 votes
1 answer
608 views

When this F9 2nd stage engine suddenly moves upon shutdown, is it moving along the rocket's axis?

The GIFs are made from frames of the live broadcast of SpaceX JCSat-16 2nd stage around the time of the second engine cut-off (SECO-2). It looks like the engine moves outward axially as the thrust ...
uhoh's user avatar
  • 149k
3 votes
1 answer
2k views

Problems with the "How to Design, Build and Test Small Liquid-Fuel Rocket Engines" text

For those that have read or consulted the text: How to Design, Build and Test Small Liquid-Fuel Rocket Engines (Rocketlab/China Lake). Otherwise, see steps 10-13 here: https://risacher.org/rocket/...
Luke Jarboe's user avatar
3 votes
1 answer
1k views

Why is the Merlin 1D Vacuum nozzle bigger than the Merlin 1D nozzle?

I know that the Merlin 1D is used in the Falcon first stage, and the Merlin 1D Vacuum in the second stage, but I can't find any information as to why the nozzle has to be bigger in vacuum. I guess ...
user21731's user avatar
2 votes
4 answers
3k views

In the context of calculating mass flow rate from thrust and Isp, how would an additional efficiency be defined?

In this answer I show a quickie derivation for calculating a mass flow rate of a rocket from a known thrust and Isp. A comment there says: That assumes 100% efficiency and ignores the fuel ...
uhoh's user avatar
  • 149k
1 vote
2 answers
813 views

How does the Space Shuttle's SSME engine's thrust vary after ignition?

After writing the question Do Blue Origin's BE-3 engines need to run for 7 seconds to “warm up”?, I took a look at the YouTube video SSME ignition sequence (found in What are the small gas jets at the ...
uhoh's user avatar
  • 149k
37 votes
4 answers
8k views

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 ...
The Rocket fan's user avatar
28 votes
1 answer
4k views

How realistic would the Sea Dragon engine be to produce given today's technology?

Just learned of the Sea Dragon proposal from back in 1962. From the Wikipedia entry The first stage was to be powered by a single enormous 80,000,000 pounds-force (360 MN) thrust engine burning RP-...
Ezra Bailey's user avatar
  • 2,890
25 votes
2 answers
5k views

Why do pressure fed engines have combustion instabilities?

Reading about the Sea Dragon idea, I came upon this argument against it, which sounds compelling, but relies on more detailed knowledge than I have: Those are to be pressure-fed to avoid "...
AlanSE's user avatar
  • 16.2k
25 votes
1 answer
3k views

What is a "Major Component Failure" referred to in news reports about the unsuccessful Space Launch System core stage test firing?

In reporting about the unsuccessful green run of the SLS core stage, Ars Technica mentions About 50 seconds into what was supposed to be an 8-minute test firing, the flight control center called out, ...
Organic Marble's user avatar
21 votes
7 answers
13k views

Can ion thrusters be scaled up?

All ion thrusters are quite small. Having read through the more approachable information about them, as they use physics pretty beyond me, I don't understand what it is about them that makes it ...
kim holder's user avatar
  • 21.3k
18 votes
4 answers
4k views

Performance of a pumpless liquid rocket engine

Basically all rockets that I know of have a pump feeding fuel and oxidiser into the combustion chamber. The turbopump is one of the most complicated and expensive components of the entire rocket. If a ...
Ingolifs's user avatar
  • 6,428
17 votes
1 answer
8k views

What are the advantages of Ox-rich staged combustion?

In the context of staged combustion, I understand that burning ox-rich creates complications associated with having hot, high pressure, oxidizer. Some engines, notably the RD-170 and RD-180 family run ...
randomUsername's user avatar
16 votes
2 answers
4k views

Why aren't expander cycle engines used on lower stages?

Looking at the simplicity of BE-7, I was wondering why dual closed expander cycle engines are not used more commonly and, as far as I know, are not used as lower stage engines at all. A commonly ...
irakliy's user avatar
  • 615
14 votes
1 answer
2k views

Changes made to ISRO GSLV-D5's CUS and FBTP since GSLV-D3's LH2/LOX CUS failure to sustain ignition?

The launch of the ISRO GSLV-D5 launching India's GSAT 14 advanced communications satellite (weighing 1,980 kg) is slated for 19th of August, 2013, flying in the GSLV Mk.2 configuration with an Indian-...
TildalWave's user avatar
  • 75.9k
14 votes
1 answer
2k views

What is that second (smoke) exhaust on a rocket engine for?

In this video of a Korea Aerospace Research Institute (KARI) rocket engine test, you can clearly see a second exhaust where thick smoke comes out. Is this an essential part of the engine, or just an ...
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