# 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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### How are rockets gimballed to produce a gravity turn for the space shuttle?

I'm trying to simulate a gravity turn using a gimbaled thruster. I'm using the dynamical system described in a previous post of mine to execute a gravity turn by changing the angle $\phi_T$ between ...
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### What does it mean when the Voyagers "switch thrusters"?

The Gizmodo article NASA fights to keep the Voyager probes running after four decades says: As another example of the probes' need to adapt to circumstances to keep going, Voyager 2 has fired up ...
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### Why is there a hole in solid rocket engines?

I would like to find out why there is a straight hole down the middle in all solid rocket engine motors. I thought it only makes sense in hybrid engines where pure oxygen needs to be blown down the ...
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### Are side boosters sometimes angled even if they are symmetrically arranged?

When more than one side booster is added to a first stage to increase thrust and they are distributed uniformly around the core (as opposed to those shown in links below) thrust does not seem to need ...
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### What is a non-propulsive vent?

I just hear the term "non-propulsive vent". Is it a thing, a vent that does not cause propulsion? Or is it an event, where a vent of some unwanted gas has occurred which did not result in a ...
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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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### Shear forces between Shuttle, tank, and boosters - what pushes what?

This is the question that I should have asked here. The space shuttle and the two solid rocket boosters (SRBs) are mechanically attached to the giant tank. SRB's, shuttle, and tank all experience ...
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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 ...
265 views

### Has an object ever been put in orbit where the first stage was always at maximum thrust?

Variable thrust through changing the number of engines burning, or through propellant throttling, or other means is often/usually done to reduce maximum aerodynamic stresses on the rocket as well as ...
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### Why do pressure-fed systems have to be pressurized with helium or nitrogen?

This is something I just don't understand. The way I see it, propellant can be pressurized all on its own in the tank. Just pump a lot of the stuff in there and make sure the tank is strong enough. ...
498 views

### Upper stage structural loads on ascent?

In another question, this came up: For example, if a Falcon 9 launches 20 tons of fuel to dock in LEO, how can the same upper stage be used to launch 40 tons of fuel to the same orbit? Doesn't it ...
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### How did the Space Shuttle maintain thrust/weight balance

As a seasoned KSP player, I am aware of how important it is during ascent to have center of thrust and center of mass perfectly aligned. If you don't, your rocket will deviate from its course and ...
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### How far would the STS get without the SRBs

This is a very stupid hypothetical - sorry! Would the Space Shuttle Orbiter plus external tank have been able to leave the pad just using the SSMEs (i.e. without the solid rocket boosters ~80% of its ...
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### 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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### Ways to obtain thrust curves of different grain geometries

Different grain geometries in solid-fuel rockets produce various thrust curves: I can imagine it's not too difficult to obtain a thrust curve of a specific grain geometry with a measurement while ...
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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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### Was the Titan SRM thrust vs time curve engineered to allow for acceleration switches to initiate staging sequence events?

This answer describes the timing between the Titan III Stage 0 (SRM's) and Stage 1 events. The Titan first stage ignited just prior to SRM separation: Titan Stage I ignition occurs at approximately ...