Questions tagged [engine-design]

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

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1answer
40 views

Need help on rocket nozzle equation

I saw this earlier post about a guy who needed help with his equation, but I was wondering about how they got one of his numbers. They said that their foot-pound/pound/degree Rankine (the gas constant ...
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40 views

Pressurant gas line design considerations

I am trying to understand the constraints on pressurant gas line sizes and lengths. For a static volume, the lines can be small in diameter because there is no significant flow velocity and therefore ...
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54 views

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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1answer
105 views

Open source liquid rocket engine

Is there an open source bi-propelant liquid rocket engine that would have all the documentation, computations, test results and 3D design files (CAD) freely accessible?
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1answer
68 views

Potential Fusion Drive system calculation issue

I will start off by saying that this is an entirely hypothetical drive system with plenty of handwaving and optimistic physics. My question I think is fairly simple and may just be something that ...
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1answer
99 views

How is the pressure within the gas generator determined?

The fact that pressure fed engines need their tanks to be at an even higher pressure has always confused me a little, but it's got me thinking; does the same logic apply to gas generator engines. If ...
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1answer
95 views

Is there a relation between combustion instabilities and chamber pressure?

Is there a relation between the combustion chamber pressure, and either an increase or decrease in both high and/or low frequency combustion instabilities. If so, how has this influenced engine design,...
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Injector design

I want to design a coaxial swirl injector for a bipropellant liquid rocket engine. I've tried to search a lot but can't find many references for the same. Has anyone worked on a coaxial swirl injector ...
3
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1answer
65 views

Cooling the nozzle extension of a nuclear salt water rocket (NSWR)

The nuclear salt water rocket(NSWR) uses a plutonium salt (at least to my understanding) dissolved in water as its fuel. The mixture is kept stable by filling the fuel tank with boron carbide, which ...
3
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1answer
516 views

ISP losses associated with exhaust vane TVC

What is the impact of exhaust vanes, such as those in the A4 and Redstone rockets, on exhaust velocity and overall ISP? As well as this, what is the relationship between ISP losses and the width of ...
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1answer
57 views

attitude thrusters sharing a common combustion chamber

Most smaller satellites and other larger but simpler space craft with a less demanding mass fraction tend to use cold gas thruster, importantly with a common or as few as possible pressure vessels, ...
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1answer
130 views

What were the stingiest and most generous vacuum nozzle? (records for the smallest and largest expansion ratios)

Vacuum nozzles are huge compared to their sea-level or atmospheric counterparts, as can be seen by comparing the first stage engines on an Electron or Falcon-9 to their second stages, where a big ...
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1answer
592 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 ...
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59 views

Why are rocket engines shaped like a bell rather than a gun barrel? [duplicate]

When blasting matter out of a spacecraft engine for thrust, it seems like you'd want as much velocity in one direction as possible. Why do spacecraft engines (e.g., Apollo CSM) have big bell-shaped ...
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1answer
71 views

Rocket engine with lowest Isp to reach orbit

Which engine with the lowest possible specific impulse has reached orbit propelling a given rocket? There is a page at Wikipedia that compares orbital engines but some engines are missing Isp value ...
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1answer
364 views

Ultra Safe Nuclear Technologies (USNC-Tech) has delivered a design concept to NASA, but what does NASA consider a “design concept” to be?

The 19-Oct-2020 Press Release Ultra Safe Nuclear Technologies Delivers Advanced Nuclear Thermal Propulsion Design To NASA begins: SEATTLE, Oct. 19, 2020 /PRNewswire/ -- Ultra Safe Nuclear ...
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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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76 views

Design impact on Chamber pressure

What is forming the amount of chamber pressure which is produced in a rocket engine and why would you like to have an higher chamber pressure? I was calculating the SpaceX Raptor engine for myself, ...
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3answers
1k views

Is it always one nozzle per combustion chamber and one combustion chamber per nozzle?

When I read about engines like the RD-170 they might have a single turbopump feeding multiple combustion chambers, and each combustion chamber has its own nozzle. Is there, or would it be reasonable ...
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112 views

What is the practicality of using sub-cooled propane in combination with HTP in an amateur engine design? [closed]

Using sub-cooled propane, at approximately -90°C (b.p. -42°C at STP) in combination with >80% hydrogen peroxide, can any meaningful gains be made, whilst considering that this fuel mixture would be ...
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1answer
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, ...
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1answer
77 views

Is there a distinct flame-front in a liquid-fuelled rocket combustion chamber?

Liquid fuel and liquid oxidizer are injected at high pressure through small orifices into the 'top' of a rocket's combustion chamber. The intention is that these mix quickly and then burn completely ...
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1answer
51 views

How important is the convergence angle of a liquid bipropellant rocket engine

So I can't exactly find out what angle should the converging part of the rocket chamber be or why different angles are chosen for engines (varies by about 15°). Are there any guidlines on the angle or ...
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1answer
83 views

How does one determine the optimal CH4:O2 ratio in a methane-LOX rocket engine?

The SpaceX Raptor uses a 78:22 O2:CH4 ratio. It also has combustion chamber pressures higher than any other rocket engine ever built. My questions are: What's the math / chemistry that determines ...
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1answer
117 views

Liquid Nitrogen Diluted Rocket

Imagine a rocket that uses a mixture of liquid nitrogen and oxygen as the oxidiser. It is designed like an oxidiser-rich staged-combustion engine, however there is so much nitrogen in the mixture that ...
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3answers
197 views

Can liquid rocket engines have the same thrust as solid rocket engines?

Take the Vega rocket launcher for example. Its first three stages are solid rocket engines and burn at a relatively short time. If I were to change its first stage into a liquid rocket engine, can ...
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31 views

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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1answer
67 views

What happened to continuously-applied heat barrier coatings in engines?

In Ignition, Clark describes an interesting approach to thermal control in rocket engines using oxygen as an oxidizer and hydrocarbon fuel: A small amount (few percent) of silicone oil or another ...
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3answers
2k views

Using nuclear detonations for propulsion

The proposed orion propulsion system used nuclear explosions to push against a giant shock absorber and propell it, but from my understanding, nuclear explosions only produce heat and rely on the ...
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65 views

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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1answer
83 views

Do pulse detonation rocket engines require any type of nozzle?

Rocket nozzles are used to convert slow moving gas under high pressure and temperature into hypersonic gas under approximately ambient pressure. From many videos of experimental Pulse Detonation ...
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5answers
2k views

Using of the rocket propellant for engine cooling

Why does liquid space propellant make a good engine coolant? I was researching the regeneratively cooled nozzle and combustion chamber on the Merlin 1D when I found this out. I do know that the pipes ...
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0answers
49 views

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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1answer
63 views

What is the relation between chamber pressure and expansion ratio?

I've always assumed that the expansion ratio of an engine equaled the pressure inside the engine over the atmospheric pressure, but I'm not sure this is right, could someone check me on this?
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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 ...
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1answer
158 views

How do we maintain the RPM of turbo pumps in liquid rocket engine?

How do we maintain the RPM of turbo pumps in liquid rocket engine? And how do we control it? And in the case of electric pump fed engine (like Rocket Labs's Rutherford engine) is easy but how we do it ...
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1answer
121 views

What is a throat plug used for?

This cutaway drawing of the F-1 injector plate has a "throat plug insert" annotated. What is a throat plug? What is it used for?
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1answer
163 views

using Tesla turbines to pump rocket fuel

From what I've read, tesla turbines are extremely lightweight and even more efficient (about 95% compared to 90% of turbopumps) when compared to turbopumps, and their bladeless design would also ...
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84 views

Preventing hard starts using varied propellant/ O/F ratio?

From what I've heard, hard-starts are a very common, particularly in less refined amateur rocket engines, and the only way to avoid them is to either start the engine on an extremely low flow rate or ...
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1answer
211 views

MT-135 Sounding Rocket info / design

I'm searching for any design file or deep-info on the MT-135 rocket, the fuel used, engines, engines info, any thing really. I have deep-searched on tons of sites but I just find few missions that ...
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1answer
72 views

Combination of fuel cells and electric motors - whether it has been used as part of an electric pump-fed engines?

In electric-pump-fed engines fuel pumps are electrically powered and batteries are used as source of electricity. Yet there is another source of electrical energy which could be used in theory - fuel ...
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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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1answer
56 views

What is the effect of poorly choosing L* in combustion chamber design?

I am a member of a university rocketry club and we are in the process of designing a liquid rocket engine. One of the previous propulsion leads did the primary conceptual design of this engine in RPA. ...
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1answer
359 views

Microwave drive for cubesats

Theory: how is this? I was doing a lot of research about the EmDrive thruster, i find 50% papers says that it work and other 50% saying that the "thrust" is a product of the interaction with ...
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72 views

what is the ISP loss associated with pressure fed engines

Numerically, what is the approximate loss of overall system specific impulse associated with pressure-fed rocket engines, not only as a result of the low chamber pressure but also of the additional ...
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80 views

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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1answer
367 views

Contracting rocket engine nozzles

The efficiency of rocket engine nozzles depends greatly on their expansion ratio an how well the ambient pressure matches the rocket nozzles exit pressure. An optimal expansion ratio means that there ...
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1answer
223 views

What is the feasibility of a graphite chamber, nozzle and bell walls

What is the feasibility of using graphite, particularly variants that are easy and affordable to acquire, in a combustion chamber, nozzle and bell as well as nozzle extension? Does it need ...
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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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1answer
193 views

Why don’t any engines use turboelectric oxidiser pumps?

Most larger liquid-fuelled rocket engines1 use fuel and oxidiser turbopumps driven by the hot, high-pressure gasses produced by burning said fuel and oxidiser: The gas-generator cycle burns some of ...

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