# 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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### Pressure Term in Rocket Thrust Equation

In the rocket thrust equation, as well as the thrust due to the mass flow rate of the exiting propellant, there is also an additional pressure term included. However I have noticed that this term is ...
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### Engine most likely to be available in the next 80 years to accelerate a craft at 1G for 4 weeks [closed]

I am wondering what type of engine would most likely be available in the next 80 that can constantly accelerate a spacecraft at 1G. Preferably, it could accelerate it for 4 weeks. The engine could be ...
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### Computing Flight Characteristics for Different Propellant Grain Geometries?

Consider the following image: I am interested in mathematically accounting for some of these different geometries but have had little success so far in finding how this can be done. The first thought ...
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### How can I find the predicted approximate altitude of a rocket based on simply the propellant, specific impulse, and propellant mass?(solid propellant) [duplicate]

I am getting all the inputs I outlined above, including burn-time which I could not mention above(character limit), from a small scale motor test. I know there are specific specific impulses for each ...
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### Commercial Sources of variable thrust Rocket Engines [closed]

The project is to build a model rocket to take off and land vertically. Max height perhaps 100 feet. Looking for a suitable engine which can provide variable thrust control and thrust vectoring which ...
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### What is missing in the conversion of specific impulse from units of seconds to thrust/mass flow rate? [duplicate]

I was trying to get the Specific Impulse of the Saturn V engines, hoping for a value in N/kg/s, as I need to know the mass consumption rate per thrust value. Any and all sources give me the value in ...
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### Is specific impulse and thrust maximum in vacuum or for exit pressure equals atmospheric pressure?

According to the thrust formulation of a rocket one can show, that maximum thrust is not delivered for pambient= 0 but for pambient=pnozzle_exit since then the momentum term is maximized. But then I ...
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### Wasn't it 1 engine out at liftoff, then another 5 were lost my the end of max-Q? [closed]

Here's a picture. 27 engines running out of 33. Probably not as bad as you'd think. Yes there's less thrust, but the other engines will be able to run longer.
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### Is it wrong to say that the thrust increases with time?

Is it wrong to state that the thrust increases with time? Because it implies that it actually increases over increasing altitude, with time?
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### Higher nozzle exit velocity generally means higher thrust right?

Higher nozzle exit velocity generally means higher thrust right? If that is the case, then a higher heat capacity could potentially lead to a higher exit velocity, thus higher thrust?
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Considering the answer of user Mark Adler here, to calculate how much ΔV is needed to raise orbit we can simply approximate it as the change in orbital velocity. Starlink satellites seem to be ...
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### Thrust & acceleration produced by a rocket engine

For given propellants, with their mass flow decided by the rpm of the turbo pump, what decides the thrust and acceleration produced by a rocket engine? Can we control them independently?
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### How high is the ISP of a fire extinguisher

After seeing this question Flying around on a fire extinguisher I wondered how high the ISP of a fire extinguisher is. What is the ISP of a fire extinguisher?
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### Is the critical inclination the same on every planet in the solar system?

I am learning about Space exploration. Is the critical inclination the same on every planet (in the solar system) or does it depend on the planet?
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### Does "% Throttle" refer to fuel flow or thrust?

the question Is it possible to throttle down the thrust in a rocket engine to 1% just like in KSP? discusses the ability of liquid fuel rockets to throttle. By convention, does the “% throttle level” ...
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### Is it possible to throttle down the thrust in a rocket engine to 1% just like in KSP?

With any normal liquid fuelled rocket engine it is possible to throttle the thrust up and down, but in Kerbal space program it is possible to bring it all the way down to around a percent thrust. Is ...
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### Rocket maximum distance [closed]

let's say I have a liquid rocket what would maximize the distance traveled by the rocket thus consume less fuel constant velocity or acceleration or why?
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### Thrust to weight of large solid fuel boosters

I have been looking at examples of large solid fuel rocket boosters or first stages used for space launch, such as P80, the Space Shuttle SRB, the various versions of Graphite-Epoxy-Motor, the solid ...
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### What is the fuel cost of deorbiting a kilo of space junk?

Removing debris from LEO requires a significant delta-V which most schemes propose to accomplish via rocket propulsion. Source The ratio of launch fuel to payload mass is often given as 9:1 for LOE. ...
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### HIghest thrust vehicles

Eric Ralph in an article about Falcon Heavy static fire test, wrote this: the most capable rocket currently operational – appeared to ignite all 27 of its first stage’s Merlin 1D engines, likely ...
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### How fast can a rocket with constant thrust but changing mass travel a linear distance with limited delta V?

Background I am developing a game / simulation that has spacecraft with advanced albeit at least not physically impossible drives travelling in the solar system. As operation time should be far more ...
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### Equations evaluating engine performance

What kind of equation would best evaluate a rocket engine's performance in foreign atmospheres such as Mars? Does it matter that specific impulse does not consider air resistance? Should I focus on ...
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### Which orbital class rocket has highest TWR at liftoff?

Which orbital class rocket (active or retired) has the highest thrust to weight ratio at liftoff?
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### Using a reverse sling + compression sock to give an asteroid an initial boost - possible?

building my a related question, I have a hypothesis in question: Assuming that we can get a tug spacecraft near an asteroid worth mining, at appropriate but faster speeds can we use a slingshot with a ...
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### What is the maximum weight a raptor 2 engine can lift up at sea level on earth?

Regardless of target orbit, how can I calculate the maximum weight one engine can lift? If the raptor's TWR is 140 and its Thrust is 1.81 MN then: W = F / TWR = 12,900 N ==> m = W / g = 1.3 tons ...
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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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