Questions tagged [engine-design]

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

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2
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1answer
84 views

Rocket engine power vs. Sound

Is there any relationship between the sound emitted from a rocket engine and the amount of thrust it gets at surface temperature and pressure?
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0answers
141 views

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 ...
7
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1answer
263 views

How similar are nuclear ramjets to nuclear thermal rockets?

Russia is currently developing nuclear powered cruise missiles. These presumably use nuclear ramjet propulsion in the same way that the US's Project Pluto would have. Is there enough similarity ...
5
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1answer
516 views

What would be the performance of a nuclear lightbulb engine with graphene instead of quartz?

The nuclear lightbulb is a closed-cycle gas-core nuclear propulsion system. It uses quartz to separate the nuclear fuel from the propellent, thus eliminating the radiation problems with open-core ...
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1answer
285 views

InSight Launch - Centaur Fuel Rich

During the launch of InSight today one thing sprung out to me: at T+408s the voiceover announces: Centaur slightly fuel rich. And again at ...
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1answer
394 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 ...
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2answers
357 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 ...
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1answer
108 views

If anything, what can cause a rocket engine to flame out prematurely?

I would assume that dropping flow rates or a drop in chamber pressure would cause the engine to stop thrusting, but I am unaware as to what specifically these conditions might be.
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181 views

Trade-offs in developing larger engines vs using more smaller engines

Looking to explore the inverse point of this question: What challenges are there for more, smaller liquid fuel engines instead of one large? As stated in the answer to the above question, fewer, ...
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1answer
995 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/...
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2answers
330 views

What are the choice of materials for LOx pumps casing and impellers?

Given the highly corrosive nature of LOx and the extremely low temperature, what materials are usually used for the LOx pumps? Steel, Copper, and many alloy tend to be flammable in liquid Oxygen ...
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0answers
132 views

Does LOx stay as liquid when entering combustion chamber?

Given the heat from combustion and increased temperature, would the LOx still be in liquid form after emanating from the injector? Or will it instantly transform into gas? Are injectors cooled using ...
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1answer
652 views

Why spray LOx into combustion chamber, if GOx is more effective?

Are there any issues in transforming the liquid oxygen into gaseous oxygen before injecting into the combustion chamber? Gaseous Oxygen will be readily available for combustion and will mix well with ...
8
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1answer
2k views

What is the current status of EmDrive engine?

This engine was making news few years ago, but I have not heard much about it lately. Were there any updates regarding its tests, further development or anything?
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1answer
253 views

Don't Preburner exhaust fumes disturb the combustion in a Full-flow Staged Engine?

Since Full-Flow Staged Engine uses preburned fuel/OX-rich gases in combustion chamber, don't those exhaust fumes produced by the preburner somehow unbalance or 'pollute' the pure combustion of fuel ...
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1answer
159 views

Does regenerative cooling reduce specific impulse?

Specific impulse of exhaust velocity depends on the temperature in the combustion chamber. Won't regenerative cooling lower the chamber temperature, causing the exhaust velocity to decrease?
8
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1answer
585 views

How does turbine power output of a full-flow staged combustion engine compare to Oxygen-rich staged combustion?

One of the benefits of the SpaceX Raptor full-flow staged combustion engine is the extra power generated by having all of the fuel and all of the oxidizer flow through the turbines to produce power to ...
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96 views

What is the largest number of engines ever used on an orbital class rocket? [duplicate]

Specifically the number of engines simultaneously ignited. So not summing up over different stages. I am interested in the max for both number of engines and number of combustion chambers. What I ...
2
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1answer
532 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 Vac in the second stage but i can't find any information as to why the nozzle has to be bigger in vaccuum. I guess that a ...
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0answers
152 views

Could a high specific impulse chemical rocket be built by using some of the fuel in a closed cycle to heat the exhaust?

There is a fundamental limit to the specific impulse of a chemical rocket because the propellant is also the fuel so you are limited by the fuels energy density. What if you burnt some fuel in a ...
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91 views

Are fission thermal engines more expensive to develop than chemical engines?

Is there something inherent in the technology of a fission thermal rocket engine that makes it a more expensive endeavour than developing yet another chemical engine? For example because of the ...
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556 views

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 ...
3
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1answer
635 views

Cooling a hydrolox rocket with Water

Would it be efficient to use water as a coolant in a hydrolox rocket, then feed the steam after the water has boiled (due to heat transfer from the engine nozzle) into the combustion chamber, so as to ...
8
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1answer
2k 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 ...
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3answers
3k 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 ...
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67 views

What is the mechanism principle of the grid fins in F9? [duplicate]

What is the mechanism principle of the grid fins in F9? or how to design the mechanism for the electricity grid fins? or how to design a electricity folding wing like the grid fins in F9?
6
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1answer
277 views

Understanding Von Braun's Math: Theoretical Isp

I've just read Wernher Von Braun's Project Mars: A Technical Tale, and I'm trying to understand the math in the back. I can follow some of what he's doing, but other parts I just can't tell where his ...
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1answer
740 views

At what pressure ratio did the fuel turbopumps of the F1 and J2 operate?

I would like to know the operating points of the fuel-turbo-pumps used in the Saturn rocket engine. (From what I could learn via google, the turbo pump went under the name Mark III) Is there any ...
8
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1answer
233 views

TR-106 under-expansion in sea-level test?

I was looking at pictures of a test fire of a TR-106 engine, and it appears to be fairly under-expanded. What's the reason for this? Does this somehow increase efficiency with this specific engine?
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96 views

Simulation of Rocket chambers like in Hall Effect Thrusters

I started learning Solidworks in hopes of being able to run simulation to study rocket chambers. Currently, I am studying the flow of plasma and its interaction with the magnetic field, but ...
12
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1answer
2k views

Merlin 1D Engine Throttling

How does the SpaceX Merlin engine control the mass flow rate to throttle its thrust? Do the pintle injectors move? Does the mass flow rate to the gas generator change?
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1answer
2k 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 ...
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1answer
3k 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??
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1answer
2k 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 ...
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3answers
2k views

Is ISP all there is to engine efficiency?

Most rocket engines have their efficiency measured by the specific impulse of the engine, which is just how fast the exhaust of the engine is going. Is there another measure of efficiency that's ...
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1answer
334 views

Do gimbaled engines have to be carefully test-fired to ensure the thrust axis intercepts center of rotation?

A smoothly running rocket engine will have a center of thrust axis. If the engine is gimbaled, that axis should pass through each of the gimbal axes (if it's a classical gimbal), or if it is a ball ...
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0answers
1k views

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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1answer
1k 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 ...
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1answer
130 views

What organizations correspond to the logos on this ORBITEC Vortex engine rocket?

Images are from the 2012 New Atlas article ORBITEC flight tests new vortex liquid fuel rocket engine. One looks a bit like a US military or DoD logo, one perhaps is ATK, but I'm not sure. Is this ...
5
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1answer
955 views

How is chamber pressure and temperature determined for cold gas thrusters?

I'm trying to get some theoretical performance numbers for a cold gas thruster using quasi-one-dimensional flow, and I don't know where to start. For combustion engines you would just take a given ...
29
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2answers
5k views

Why cool engines with fuel as opposed to oxidizer?

As I was watching Tom Mueller describe the Merlin engine, he said that the RP-1 propellant is pumped through ribs in the nozzle to regeneratively cool the engine. Also, a video about Copenhagen ...
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0answers
104 views

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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1answer
321 views

Does all of the fuel in a Staged Combustion Cycle go to the preburner? [duplicate]

Can anyone tell me the difference between staged combustion and full flow staged combustion? Does full flow mean there are 2 preburners (fuel- and oxidiser-rich respectively) or does it mean that ...
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0answers
283 views

How was the Stabilo crewed re-entry vehicle supposed to work? A tractor engine with four nozzles?

ARCA Space's webpage for the Stabilo program has a description and an image. Hydrogen peroxide monopropellant? Reaction closer to the crew than the nozzle? With thrust at the top, it seems that ...
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1answer
2k views

The principle behind regenerative cooling?

In regenerative cooling the fuel is passed around the nozzle before being pumped into the combustion chamber right? I don't really see how this affects cooling itself, since the heat captured around ...
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3answers
423 views

Rocket Engine demonstrator fuel choice

As rocket Science and Space Exploration is becoming more and more popular, I'm currently running some numbers, whether it would be possible to build a rocket engine for showing at schools or ...
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0answers
111 views

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 ...
2
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1answer
438 views

Could super-cold LOX be used in every rocket engine?

Super-cold LOX gives advantages in performance for a rocket. But it isn't used in all rockets. SpaceX's Merlin 1D rocket engine uses super-cold LOX. Also NK-33 use sub-cooled LOX. Could super-cold LOX ...
4
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1answer
350 views

Ribbed rocket nozzles

A short while ago I visited a real life dissected rocket and it came to my attention that its nozzle is ribbed across its surface. Why would engineers build it this way and what are the advantages ...
6
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1answer
481 views

What are the issues and concerns related to turbopump blade cracks and manned spaceflight?

While the WSJ headline sounds ominous: Congressional Investigators Warn of SpaceX Rocket Defects, Quartz's SpaceX needs to redesign its engine to ensure it is safe for human spaceflight seems to be a ...