Questions tagged [thrust]

Force produced by pushing against a reaction mass in space à la Newton's third law: "For every action there is an equal and opposite reaction." The thrust of a rocket engine is the forward force produced by expelling the exhaust mass (reaction mass) in the backwards direction.

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Is the momentum thrust of a liquid rocket engine in a static test fire the same as in flight?

Assuming vacuum exit conditions are matched by means of a suitable ejector mechanism, is the exhaust velocity of combustion products relative to static engine the same as that of a flying rocket ...
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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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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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Thrust needed for Ion Thruster Lift off from Earth surface

I've been calculating the needed mass flow rate for a hypothetical ion rocket, lifting off from Earth's surface and propelled with a Dual-Stage 4-Grid ion thruster. Data given: mass of the spaceship /...
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Study of selection higher stages for a multistage rocket

Will it be correct to say that the thrust produced by the first stage is the ultimate limiting factor for a rocket's ability? The logic behind this thought is like this: Higher quantity of its ...
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What is the maximum thrust of the Starlink satellites?

As in the title, what is the maximum thrust (in N) that the satellites of the Starlink constellation can achieve? I read that they use Hall-effect thrusters, but I couldn't find a specification of the ...
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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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How to propagate the trajectory in GMAT with a custom thrust profile

So basically I was trying to design a low thrust maneuver to increase the apogee of the spacecraft. I solved it separately and got some thrust profile (thrust and it's direction as a function of time)....
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Where to send invention ideas?

I invented a new type of thruster for satellites. I would like to know where can I send the report I made. The report was reviewed by several physicists and engineers in my environment, but I would ...
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Making sense of rocket engine thrust calculation [closed]

Recently I've been trying to design a hypothetical rocket engine using the mass flow rate, exit mach, temperature, and pressure calculations provided by NASA's own website. I've come to know quite ...
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What are the various ways that rockets measure the instantaneous thrust of each engine?

@DavidHammen's answer to Engine failure: how to detect? mentions thruster sensors. This intrigued me and so I thought I'd ask about how this is done. Thrust is a critical parameter to know in real ...
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Thrust requirements from Saturn 1 rocket's first stage

What was the need / trigger to develop Saturn I rocket, and who defined / what dictated the thrust requirements from Saturn I, so that eight number of H1 engines had to be clustered to achieve that ...
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How are thrust specifications for multi-nozzle engines given?

The Soviet R-7 ICBM used 5 RD-107/RD-108 engines in its first stage in a "Quincunx" formation. Each engine had four CD nozzles, and 1 propellant pump, common for all four nozzles. The thrust ...
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Engine thrust gain with altitude [duplicate]

As you climb at launch, atmospheric pressure falls, causing thrust to rise. The thrust gain I'm talking about here is due to the increased ratio of nozzle pressure to atmospheric pressure. I'm going ...
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Rocket engine test bed structure

Rocket engine thrust will eventually "lift" a certain amount of weight, to a certain height. For Saturn V, they used 5# F1 engines, each of which produced a thrust sufficient to lift ...
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Calculating mass expelled from cold gas thrusters

Consider a cold gas thruster rated at 1 lbf per firing. The thruster is on-off: there is no throttling, so when it fires it's at a constant full thrust. Assume the gas is nitrogen, and that it has a ...
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Earth Launch System with Water Propellant

Water based thrusters have been proposed (and possibly tested by now) for use in satellites and other in-space vehicles - see this NASA article. The idea is to perform electrolysis on the water to ...
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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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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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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/...
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Propulsion thrust vs high winds?

While I do understand that high wind speed is a risk for space launches (and all air flights), still, is it a physical constraint or a computational problem given we are not dealing with a hurricane/...
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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 ...
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Why does the Indian PSLV rocket have tiny boosters?

I have noticed that the Indian rocket PSLV has tiny strap-on boosters attached to it on the sides at the bottom. Why would these be used instead of just using a larger first stage? Why is there an ...
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Thrust value for space mission from Earth's orbit to Venus' orbit

If I had to take a spacecraft from Earth's orbit (400km above earth) to an orbit around Venus (6151km X 50,000km elliptical orbit), how much thrust will I need. Delta V is 5km/s using hohmann transfer?...
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Payload capacity of a rocket

Why does a rocket have far more payload capacity when placing an object in LEO compared to when it's placing the object in farther orbits, like on the Moon? If a rocket has sufficient thrust to take ...
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Spacecraft propulsion, Thrust, Delta V

For a spacecraft on an interplanetary mission (e.g. Mars), after deciding the propellant ISP value and Delta V required, how do you calculate the thrust required? $$F = \dot{m} V_e + (p_e - p_0) A_e$$ ...
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Is the thrust provided by electrostatic engines low because thrust depends on particle mass of the exhaust in the case of electrostatic engines?

Based on the equations of mass flow rate and exit velocity provided here (https://www.grc.nasa.gov/WWW/K-12/rocket/rktthsum.html), we can see that thrust in the case of chemical engines does not ...
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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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How should mass specific impulse calculated for relativistic exhaust?

This answer says: Optimising for Isp only is problematic, as it's simply: $$I_{sp} = \frac{v_e}{g}$$ Which is the same as optimising for exhaust velocity. With no constraints on thrust, particle ...
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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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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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Rocket specifications: specific impulse, thrust to weight ratio and burn time

In my somewhat unrealistic school project regarding space tourism to Mars we have to accelerate a 500 ton module (mass of propellant and engines not included) from LEO to an orbit around the sun at ...
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How efficient and fast would seven Caplan thrusters be at pushing the Sun and would it be worth building more than one?

I was thinking about stellar engines. One type of stellar engine is the Caplan thruster, which concentrates the star's light onto the star's surface to create beams of solar wind, which are collected ...
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5 votes
2 answers
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Falcon 9 Merlin 1d thrust calculated through every moment of flight

I am currently trying to recreate the launch of falcon 9 in unity. For the calculations I need the thrust of the first stage (only doing it for one stage for now). How to calculate it depending on the ...
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3 votes
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Thruster firing time for station keeping

I am simulating the example of LEO station keeping in GMAT with a delta-v thrusters of 2.5m / s, my question is how can I determine the time in which the thrusters act to raise the height of the orbit ...
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1 vote
1 answer
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Small thrust thrusters

If I have a propeller with a continuous thrust of $1 \times 10^{-9}$ Newtons, can I take the satellite from LEO to the moon? How can I calculate the time it would take for a satellite of a certain ...
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5 votes
1 answer
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Saturn 1 thrust mismatch

While reading about Saturn launch vehicle family, I read that Saturn 1 third stage used 2# RL 10 engines, producing a total thrust of 30K Pounds. But each RL 10, individually produced approx 25K ...
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Why there are small holes just at the ending of RS-25 rocket engine? [duplicate]

I have seen these holes in many pictures and I can't understand what are these and why are they used?
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Ion Lifter Thrust Calculation Problem

I've recently started building an ion lifter. I tried calculating the thrust the lifter produces but I came to a value that is way to high for such a small lifter. I'm using a 40kV at 1800mA AC ...
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why do under-expanded engines have less than ideal thrust?

I've been looking into rocket propulsion a bit and got stumped on something. I read that the thrust generated by an engine can be determined by the following: $$ F = \frac{w}{g}v_{e}+A_{e}(P_{e}-P_{a})...
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4 votes
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single thrust vs. multiple thrust

Does using one 5000 pound thrust engine give the same amount of thrust as five 1000 pound thrust engines? I am asking in terms of effectiveness not efficiency. Do the two different configurations ...
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How strong is the Starship bottom bulkhead?

I am wondering how much of a role does the pressurization of the propelant tanks play in making them withstand the engine thrust. What I am getting at is how much would the pressure offset or balance ...
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Using side thrusters on a missile to create an angular acceleration

Assume a rocket is standing on the ground with mass = 1000 kg, and near the top of rocket we apply a force of 100 N for say 1 sec, now assume that this is sufficient to tip the rocket over/start ...
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How did NASA calculate 22 million "rocket horsepower" for the SLS Booster?

This answer to Does NASA really report the power of rockets in horsepower? cites NASA news item Space Launch System Booster Aimed and Ready to Fire which says "What's impressive about this test is ...
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VASIMR thruster at scale

I am working on making one, the truth is that the principles are not so difficult, but does anyone have any plans? or reference "with numbers"? because the truth is that it is quite difficult to scale ...
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What is the precision attitude estimation strategy for satellites, under impulsive thrust manoeuvres?

Satellites mostly rely on star trackers and gyros for precision attitude knowledge. Under impulsive thrust manoeuvres, I expect the star trackers to blur and provide no attitude knowledge. What is the ...
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21 votes
3 answers
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Why do nuclear rockets (e.g. NERVA) have such poor Thrust-to-Weight ratios?

Nuclear fission releases far more energy per kilogram of fuel than conventional hydrocarbon sources. However, proposed nuclear rocket engines like NERVA (https://en.wikipedia.org/wiki/NERVA), while ...
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Why is a 1.5:1 TWR desirable for a reusable launcher?

According to a Teslerati article linked from another QA: The most critical component for the booster, according to Musk, is that there is “a lot of force pushing up.” He states that to launch ...
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Confusion about reactive force of a rocket

I am confused about the equation describing the reactive force of a rocket. I read from this source this equation: where M is mass of the rocket, u is the velocity of exhaust gas in an inertial frame ...
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Are there any other examples of right-angle exhaust diverters in spacecraft?

The Scott Manley video The Only Pilot to Shoot Down A Spacecraft - A Space Ace talks about the ASM-135 ASAT and its successful test launched from an F-15. He shows images from the page The F-15 ASAT ...
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