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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6 votes
1 answer
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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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2 votes
0 answers
48 views

Why would you want a low turbine temperature in an expander bleed cycle engine?

In a paper by Sippel et al. [1] the following statement is made on page 2: "Consequently the LE-5B turbine drive gas temperature has been successfully reduced [w.r.t. the LE-5A engine]." ...
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4 votes
0 answers
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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 ...
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5 votes
2 answers
1k views

Are nozzle plugs taken out before launch or are they ejected upon ignition?

Inspired by this question. For most orbital launch vehicles, do their engines have nozzle plugs installed and what happen to them at launch? Are they manually removed during the prelaunch/rollout or ...
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3 votes
1 answer
442 views

What's this inside the RD-0120?

There is a decent shot of the RD-0120's inside in this video: I guess it's something covering the injector plate or even the combustion chamber since the SSME's injector looks very differently: Also,...
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8 votes
1 answer
775 views

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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3 votes
1 answer
153 views

Where is the gas generator on the RS-68?

Wikipedia notes that the RS-68 uses a gas generator cycle. I've already seen a couple of photos of the RS-68 and I do not see any gas generator exhaust pipe or a pipe leading into the nozzle. So where ...
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1 vote
1 answer
158 views

What is the point of having a central rocket engine when it receives performance losses?

Recently I asked this question about center engine performance and received an excellent answer from @OrganicMarble. The first sentence of the answer is If anything, the flow field interactions hurt ...
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7 votes
0 answers
96 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 ...
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-3 votes
2 answers
246 views

Why isn't oil used for rockets? [closed]

Most people know that when you add oil to a fire, it grows rapidly and becomes more powerful. So, why isn't added into the propellant just before it comes out of the engine?
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5 votes
2 answers
1k views

Resources on Coking?

I'm trying to do some background research on the coking process that occurs in rocket engines, but haven't found any resources that fit what I'm looking for. To be more specific, I'm just looking for ...
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4 votes
1 answer
152 views

Do engines in the middle of an engine cluster get impulse benefits?

Presumably the rocket engines in the center of an engine cluster would be surrounded by lower-pressure exhaust from the outer engines so essentially the "atmospheric pressure" around the ...
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3 votes
1 answer
116 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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1 vote
1 answer
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Cold Gas Thruster to space engineering challenges

I have seen this question. The natural extension of this question would be - could you lift a human or an equivalent payload to LEO with cold gas thruster only? For numbers, take 100 kg mass for the ...
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12 votes
1 answer
294 views

What does it mean to tune the Saturn F-1 engine to a frequency, and how is the tuning done?

Chapter 10 of Chariots For Apollo remarks the following in discussing the pogo problem of Apollo 4 and 6 and the role of the first stage F-1 engines in that: The mission analysts later discovered ...
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7 votes
0 answers
80 views

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 ...
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0 votes
2 answers
1k views

How do second stage rockets ignite their engines?

When launching, the fuel mixes and then ignites when it hits oxygen in our atmosphere. How does a second stage ignite once in the vacuum of space?
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1 vote
0 answers
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Comparison of F-1 and RD-170 rocket engines

The F-1 was the most powerful single-nozzle engine ever flown and the RD-170 the most powerful multiple-nozzle engine ever flown. Both engines use kerosin and LOX. The NK-33 was a smaller engine using ...
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11 votes
3 answers
3k views

Is a Raptor 2's thermal output really comparable to that of a nuclear power plant?

After about 01:10:10 in the 2022-02-10 SpaceX Starship Update part of Musks answer to Tim Dodd's question about Raptor 2 development: The only remaining issue that ...
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4 votes
1 answer
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Why aren't ejectable engine blocks in use today?

Related to my previous question regarding expending the RS-25s. Why aren't engine blocks, especially those expensive RS-25s on the SLS, made ejectable from the fuel tank assembly and parachute to be ...
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4 votes
1 answer
1k views

Why isn't NASA planning on saving some of the RS-25Ds due to their historical significance?

A while ago, Scott Manley made a video about the Artemis program and how NASA will expend all its Block II RS-25D engines through the SLS's first four launches. Why isn't NASA planning on putting some ...
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33 votes
7 answers
6k views

How do satellite motors keep themselves cool and lubricated?

I'm a high-schooler and today we were taught about the car engines and we were told that in order to maintain proper lubrication in order to reduce the heating effect of friction in the pistons using ...
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6 votes
1 answer
275 views

Can gas bubbles form in the fuel and oxidizer rocket engine pumps due to insufficient flow from the tanks?

In a staged combustion cycle rocket engine, the fuel and oxidizer are fed into turbo pumps which are in turn powered by a pre-burner. My question is how do they ensure that the fuel and oxidizer are ...
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7 votes
2 answers
695 views

Are In-Flight Electrically Heated Steam Rockets Possible?

I wonder if a rocket that uses electricity from internal batteries to heat water in its tanks to high pressure would be able to use that pressure to take off. Is it possible? I've researched here and ...
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3 votes
1 answer
212 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 ...
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6 votes
1 answer
439 views

Can the higher oxides of nitrogen, like nitrogen pentoxide, be used as oxidisers in rocket engines?

Both nitrous oxide (N2O) and dinitrogen tetroxide (N2O4) are used in storable propellant combinations, so, simply as a continuation, can the higher oxides of nitrogen (N2O5, N2O6, etc.) still be used ...
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2 votes
2 answers
231 views

Why aren’t vacuum engines turned on after Mach 1?

In rockets, smaller nozzles are used at lower altitudes because atmospheric pressure would cause problems by pushing air into nozzles with higher expansion ratios. However, it seems to me that once ...
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0 votes
1 answer
132 views

How do you calculate thrust produced by a rocket engine?

I was planning on building a water-powered rocket. I also wanted to know how high my rocket might go. Could someone help me figure out, how to calculate thrust produced by a rocket engine?
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39 votes
6 answers
8k views

How much has fuel efficiency increased in rockets since the Apollo missions?

I have been talking with a friend of mine and the subject turned to modern rockets versus Apollo era rockets and fuel efficiency. My friend stated that today’s rockets use half the fuel of the rockets ...
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1 vote
0 answers
70 views

Calculating thrust using only weight

How do you calculate minimum thrust for a rocket ship using just the weight of the rocket? How do you chose what engine you need to use for your rocket?
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2 votes
1 answer
85 views

Solid metal fuel for nano satellite thrusters

A South African company is developing a solid metal fuel thruster that was initially researched by NASA but was not further developed, an electric reaction could be used to vaporise solid metal fuel, ...
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4 votes
3 answers
160 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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8 votes
1 answer
601 views

How do you test-fire vacuum engines in a vacuum chamber? Why doesn't it fill up almost instantly from the exhaust and spray (deluge) water?

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 ...
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2 votes
0 answers
76 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 ...
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2 votes
1 answer
52 views

Resources where one can find RD-171MV engine technical specifications? (e.g.TWR, Expansion Ratio, Isp, Thrust, Chamber pressure, O:F ratio)

I'm trying to get a hold of various technical specifications for the RD-171MV engine A modification of RD-171M being developed for the Irtysh rocket. Unlike RD-171M it's completely made from Russian ...
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2 votes
1 answer
275 views

Pressure inside Starship CH4 and LOX header tanks during entire Earth-Mars trip and landing on Mars?

What should be the pressure inside Starship CH4, LOx header tanks during the entire Earth-Mars trip and landing on Mars ? The main CH4, LOx tanks should be under 6 bar pressure, because that is the ...
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4 votes
0 answers
175 views

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 ...
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4 votes
0 answers
86 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 ...
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0 votes
1 answer
124 views

Difference between 2 pumps on same shaft run by a turbo pump and 2 pumps run on separate turbopumps

So i was trying to understand the working of the Full Flow Staged Combustion cycle(FFSC) and was comparing it to the Staged Combustion Cycle(SC) and Closed Combustion Cycle(CCC) a question came up in ...
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7 votes
1 answer
1k views

Using coolant as 3rd propellant

Rocket engines often have 2 propelants, one of which is used to cool the engine and after that the hot propellant is injected in the combustion chamber. Would make sense to have a third propellant ...
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4 votes
2 answers
631 views

What is the Isp of gunpowder likely to be? Could this table be right? Can it even be determined?

There are some unsourced refutations of the value for the Isp of gunpowder in the table shown below can be found under What kind of engine does this Isp = 1600 refer to? Is it cubesat-friendly? Alas ...
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  • 148k
11 votes
1 answer
276 views

Why is the flame color from the New Shepard engine orange?

New Shepard is described as using liquid oxygen and liquid hydrogen for its propellants. When hydrogen and oxygen burn, as in the Space Shuttle main engines, there is a short conical blue flame, ...
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3 votes
1 answer
196 views

Are the (relatively) new "all electric" satellite buses like the Boeing 702SP really all-electric? Are RCS and momentum unloading done with ions?

This answer to Can ion Thrusters be used for Reaction Control System? got me thinking about the new "all-electric" class of commercial satellite buses. Question: Are the (relatively) new &...
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  • 148k
2 votes
1 answer
290 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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4 votes
1 answer
729 views

Rocket propulsion question help

I've attempted this question but once again got this wrong. Here is what I did I knew that the thrust equation was mass flow * (Vj - V0). I also knew that the mass ...
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3 votes
1 answer
251 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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  • 148k
2 votes
1 answer
161 views

Has Demonstrator-1 2021-006BX demonstrated a hydrogen-oxygen combustion engine fueled by electrolysis yet?

NASA's NASA CubeSat to Demonstrate Water-Fueled Moves in Space says: A NASA CubeSat will launch into low-Earth orbit to demonstrate a new type of propulsion system. Carrying a pint of liquid water as ...
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  • 148k
2 votes
2 answers
820 views

Technical feasibility of using Raptor engines for Vulcan rocket

According to a recent GAO report (p. 116), ULA's Vulcan rocket's BE-4 engines are "experiencing technical challenges" and there is some concern whether they will be ready / certified in time ...
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1 vote
1 answer
144 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 ...
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19 votes
4 answers
3k views

Can "engine" and "motor" be used interchangeably in spaceflight? Are there any cases where they can't be?

Typing "rocket motor" into google returns a page full of links mostly about rocket engines. It seems that The Google has AI-synonymized them. Question: Can "engine" and "motor&...
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