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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3
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1answer
138 views

Why are Starship's tanks curved the way they are?

Since Starship has to feed its engines in two kind of situations : -during ascent, acceleration is colinear to Starship's longitudinal axis. -at the end of the belly dive, acceleration is normal to ...
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1answer
85 views

Relationship between thrust and torque

I am a newbie to Aerospace and also a sophomore. I will try to explain as much as I could. What I know so far: A launch vehicle has a maximum thrust of 10N , Assumed propellent weight, Assumed ISP ...
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1answer
100 views

Can Falcon 9's engines be ignited more than 4 times if there is enough TEA-TEB?

SpaceX's Falcon 9 uses TEA-TEB as a ignitor for its Merlin engines. My question is if the rocket has more TEA-TEB, can the engine be shut down and restarted more than 4 times?
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2answers
3k views

Can nuclear thermal engine designs be shutdown in such a way as to be restartable, in space?

Nuclear thermal rocket designs have a working temperature of 2000k or greater. Shutting such a reactor down won't stop that heat production instantly - it'll take quite some time to cool. Do current ...
5
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1answer
582 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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2answers
188 views

What happened to tripropellant rockets?

IIRC, tripropellant rockets can deliver superior performance compared to bipropellant rockets (at the cost of added complexity). Now, I know that there is the Li/H/F combo, but it isn't used because ...
6
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2answers
398 views

Solid state thrust vectoring

Usually thrust vectoring for the whole rocket is done by changing the orientation of individual engine(s) by hydraulic/electric actuators. So in this system the engine simply moves and with it the ...
3
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1answer
74 views

How do I calculate thermochemical properties of mixed gases?

I'm working on a rocket project, and my design of engines is stalled. I need to be able to calculate the Cp, Cv, and R for mixtures of O2/CH4 (stoichiometric or fuel-rich mix) and CO2/H2O (result of ...
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1answer
135 views

How much power do radiation-based engines produce

I heard that the Voyager satellites used a radioactive source to power the computer and sensor systems. How much power can this technique produce nowadays? Could it power, say, a fighting robot? ...
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0answers
16 views

What are the best books to learn about space exploration? [migrated]

I would like to learn more about space exploration; what technology we have, how specific satellite technologies work, rocket design etc. What books would you advise to read? Where would you advise to ...
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0answers
58 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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0answers
47 views

Sources for values for realistic thrust calculation exercise?

I want to use this simplified equation to calculate the thrust of multiple different real engines: $$F = \dot{m} V_e + (p_e - p_0) A_e$$ Source: https://www.grc.nasa.gov/www/k-12/airplane/rockth....
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0answers
166 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 ...
2
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1answer
114 views

Could New Horizons' thrusters' ISP be as low as 157 sec?

A discussion below How much of a deep space spacecraft's structural mass is useless dead weight after launch? Any plans to shed it in the future? has lead to https://nssdc.gsfc.nasa.gov/nmc/...
6
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1answer
3k views

How many ion thrusters would be needed to accelerate a 1000 tonne craft at 9.8m/s²?

If we assembled an array of today's best ion thrusters in orbit, (the x3?) how many would be needed to accelerate a 1000 tonne spacecraft at 1g? I'm thinking Space Tug, for repeated Mars missions. ...
3
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1answer
64 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 ...
8
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1answer
370 views

How can firing a Space Shuttle OMS engine below 21 km cause its nozzle to “collapse”?

This answer to Can the space shuttle use OMS engines during landing? says: No and quotes Section 3.7 of the Orbital Maneuvering System Workbook; OMS 21002 October 10, 2006, Final version, USA006500 ...
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4answers
114 views

How do pressure-fed engines stay cool?

Does anyone know how pressure-fed/hypergolic rocket engines cool themselves down? Do they regenerativly cool themselves? Thanks!
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7answers
3k views

Are there any hand-sized rocket engines?

Are there any rocket engines that are small and light enough to be held in one or both hands? Gas, liquid and hybrid designs are fine but solid motors are excluded (with the exception of solids that ...
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0answers
49 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. ...
3
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2answers
150 views

Longest static fire?

What is the longest duration for a static fire of a complete rocket stage? Initially I wanted to ask this for Falcon 9 and Falcon Heavy I found a 10 second static fire for Falcon Heavy - https://...
3
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1answer
87 views

How powerful do cold gas thrusters normally get?

Modern rockets like the Falcon 9 use cold gas thrusters for steering on landing approach when the engines are dead. Cold gas thrusters are common in smaller satellites and spacecraft, which way a ...
2
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1answer
99 views

How can you calculate a course based on constant acceleration burn and deceleration burn?

In the TV series The Expanse, a sci-fi space-engine called the "Epstein Fusion Drive" is a thruster capable of performing constant acceleration (up to and beyond "20g" (about $200 ...
6
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1answer
431 views

Is there an acronym for secondary engine startup? SESU?

We have acronyms for main engine cutoff (MECO) and secondary engine cutoff (SECO). Do we have an acronym for secondary engine startup---SESU maybe?
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3answers
189 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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1answer
73 views

Why isn't the engine's Case-Throat-Nozzle reusable in Virgin Galactic's SpaceShipTwo?

I raed on https://www.smithsonianmag.com/smithsonian-institution/engine-powering-future-civilian-spaceflight-enters-collections-180971493/ (mirror): RocketMotorTwo is a hybrid rocket motor that ...
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2answers
3k views

Was there an anomaly during SN8's ascent which later led to the crash?

In SpaceX'S video, there is a conflagration inside the engine enclosure which seems irregular at around 1:49:49. The engine far left of the engine camera stops working and a few seconds later some ...
2
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1answer
66 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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1answer
49 views

Small liquid rockets are hard/expensive to build, but what about to use them?

It's become a sad and oft-demoralizing truism that it's quite difficult and expensive to design or build even low-performance liquid-fueled rocket engines, and that amateurs -- even those with skills ...
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2answers
141 views

What is the thrust of Momentus' thrusters?

I understand that they have an interesting method of using microwaves to produce plasma from water. They claim to have a "high" thrust and "high" specific impulse. Their Isp ...
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0answers
54 views

What is the mass of the Electron rocket's battery pack?

I am trying to estimate battery weights for electric pump fed rockets of various sizes and wanted to use the electron rocket as data to validate my calculations. However I was unable to find the mass ...
2
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1answer
144 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 ...
6
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1answer
119 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?
2
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1answer
70 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 ...
4
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0answers
66 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 ...
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0answers
85 views

Which engine has the highest nozzle wall temperature? [closed]

From all the rocket engines that were used in flight, which one has the highest nozzle wall temperature? The nozzle wall is not heated uniformly. But there are regions where they reach max temperature....
6
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3answers
2k views

What is the lowest first stage thrust for a launch reaching orbit?

What is the lowest thrust for a first stage rocket for a rocket that reached Earth orbit?
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0answers
56 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? ...
2
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2answers
117 views

Outsourced rocket engines for medium and small launchers

Is there any company selling rocket engines that work for small and medium orbital launchers other than Ursa Major Technologies? Looks like a good model: the company developing a rocket can save a lot ...
2
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1answer
75 views

Why maintain nominal engine inlet mixture ratio for a gas generator engine?

I was reading up on gas generator cycles and came across the following paragraph talking about fuel or oxidizer rich gas generators and the different mixture ratios for the main combustion chamber ...
3
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0answers
128 views

What are these white garbage-like things on Falcon 9 vacuum engine?

On recent launch I noticed, that some white things jumping on vacuum engine in space. Something like garbage or condensate. See video at right at times when Earth is at left: ...
3
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1answer
74 views

How throttle changes affect calculations of thrust?

So, for constant throttle setting equation to calculate thrust looks like $ \ F = \dot{m}_\mathrm e V_\mathrm e + (p_\mathrm e - p_0) A_\mathrm e$ But if we are looking at flightclub.io simulation, ...
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1answer
97 views

Concerns/challenges with LOX as a regenerative coolant

What are the fundamental issues that make LOX as a regenerative coolant difficult to work with or less ideal than using fuels as a coolant instead in small scale engines (<7000lbs of thrust/ ...
4
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0answers
67 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 ...
5
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1answer
349 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 ...
5
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0answers
83 views

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 ...
2
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2answers
136 views

Trying to make a program to calculate (liquid) engine size. Can you please help me check for any problems?

So as the title says I am trying to write code to calculate engine size and some other parameters. For the equations, I used mostly : Sutton's Rocket Propulsion Elements 8th Edition, and for the ...
8
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1answer
1k views

Have there been rocket engines designed for diesel? What ISP theoretically possible?

Have there been rocket engines or even test engines that have used diesel as a fuel? If so, what oxidizer had they used and what ISP did they achieve? If not, is it possible to say what ISP is at ...
4
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1answer
289 views

Why do RS-68s suffer ignition failures?

NROL-44 failed to be in space for yet one more night last night, this time because of an automated hotfire abort triggered when one of the outboard (iirc) engines on the Delta IV Heavy failed to ...
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0answers
81 views

Need help finding a clean expression for exit velocity [duplicate]

I'm trying to calculate a engine burning LOX and ethanol (96%) and for that I am using both CEAgui, a GUI for NASA's CEA (Chemical Equilibrium with Applications) code Sutton's Rocket Propulsion ...

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