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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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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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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Why are unused launch abort rockets jettisoned rather than used to augment thrust?
Launch abort rockets use powerful rockets. For a pad abort, they must have enough thrust to lift the capsule to an altitude where parachutes can function.
The Apollo launch escape rocket had a 155,...
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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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How is thrust transmitted from strap on boosters to the central core?
Strap on boosters of a lot of heavy launch vehicles seems to be attached with just a few "flimsy" struts.
Here are few images for reference :
Some of the possibilities:
These support structures ...
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Where does the thrust act in a rocket engine and how is it transferred to rocket structure?
A rocket engine is basically a device that generates a high pressure inside the chamber and the pressure difference creates a force.
A nozzle helps in effectively accelerating the flow and increases ...
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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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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 there any rule for rocket engine nozzle proximity from each other?
I wonder if there is any rule for how closely you can put engine nozzles to each other. Are there any vibration, heat, etc. constraints when you are assembling two or more engine bells together?
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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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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. ...
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Do the propellants ionize in chemical rockets?
When combustion takes place in a chemical rocket (LOX/LH2), do the gases ionize due to high temperatures? If they do, how do they get around the problem?
Ionization is a waste of energy I believe, ...
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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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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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Why do chemical rockets encompass a weird shape on this thrust vs. Isp graph?
Consider this graph of engine thrust versus specific impulse (from https://dawn.jpl.nasa.gov/mission/ion_prop.html):
Most propulsion technologies encompass roughly rectangular regions on the graph. ...
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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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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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What was the first rocket to use gimbaled thrust?
A gimbaled thrust system was used on the Space Shuttle, which is easily recognized in the beginning of this launch video. Was this technology first used by jet fighters, or was it first invented for ...
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What is the correct thrust curve for a solid rocket with a simple circular hole, and why?
Going to wikipedia's article on solid-fuel rockets, I come across some graphs of thrust curves for certain bore-hole geometry. Right now I'm interested in the simplest bore-hole: a circular hole right ...
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What was Sutton talking about? How to "obtain small accelerations by taking advantage of difference in gravity as a function of altitude"?
Sutton and Biblarz's Rocket Propulsion elements says in Chapter 1, section 1.2 (editions 7, 8, 9, possibly earlier as well) that:
Totally different methods of producing thrust are used in ...
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Why will SLS Block I bring less mass to LEO than the STS shuttle system did?
The Space Transportation System (STS) could bring a fully loaded shuttle orbiter of 109 tons to orbit (or maybe empty+payload 68+25=93 tons). The Space Launch System (SLS) Block I is based on STS, but ...
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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 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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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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Can we thrust a rocket from earth using electric power?
I wanted to know if we can thrust a rocket from earth using electric power? If yes, how and has anyone tried to do 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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Can you reach the Sun by only thrusting horizontally?
Suppose you have a hypothetical spacecraft launched from Earth.
When it escapes from Earth's gravity it will still be orbiting the sun at roughly the same velocity as the earth, approximately 30km/...
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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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How did SpaceX achieve such a high Thrust to Weight ratio with the Merlin engine?
Were there specific breakthroughs which allowed SpaceX to get such an incredible thrust to weight ratio? The next closest American engine was almost twice as heavy (199 vs 82), and the next closest ...
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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 well can hybrid motors be throttled?
Pretty self explanatory: down to what percentage can hybrid rocket engines be throttled to? And what fuel / oxidiser combinations allow for the greatest throttling?
I'm planning on using hybrids for ...
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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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Why are optimal launch TWRs so different in KSP than on earth?
In Kerbal Space Program (KSP), optimum thrust-to-weight ratio (TWR) is around 1.5-3. When looking at NASA, SpaceX, Blue Origin spacecraft, the launch TWR is around 1.25-1.3.
Is it because the ...
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How much G force is applied when correcting an orbit around Earth?
How much g force is applied to a satellite to correct a decaying orbit if done each orbit? How long does it take to correct an orbit on the average?
I understand there are variables as in which orbit ...
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Optimal thrust vs isp for variable isp rockets (VASIMR) when taking off/orbiting
This question was initially inspired through playing Kerbal Space Program, however I am seeking a more general answer.
I've been playing the excellent Near Future Propulsion mod for KSP, using ...
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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 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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Relationship between part dimensions and performance of ion electrospray thruster
I got the relationship between power, thrust and specific impulse for an ion electrospray thruster as follows:
$$P/T= 1/2 \times g_o \times I_{\mathrm{sp}}$$
Where: $P$ = power required (in Watts), $...
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Could the Bloodhound Rocket Car be launched into orbit?
The Bloodhound SSC (Supersonic Car) currently being constructed to break the 1000 mph barrier is powered by a Hybrid Rocket (Solid fuel + HTP) and a Rolls-Royce EJ2000 Jet Engine:
Considering the ...
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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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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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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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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 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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With pressure-fed engines, is any measurable thrust generated by venting the pressurant out the engine bell after flameout?
A pressure-fed rocket engine supplies fuel and oxidiser to the combustion chamber by pressurising the fuel and oxidiser tanks with an inert gas (typically helium or nitrogen). Presumably, when a ...
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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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How to calculate rocket acceleration?
What are the equations used to calculate rocket thrust, acceleration, and weight? Obviously this depends on the type of fuel and engine and a lot of other factors, but I'm interested in a simplified ...
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Sea Launch, and other ocean-based launch pads: Stability?
A rocket launch generates a huge volume of gas which are then deflected in different directions.
(source: Space News)
Ejected gas have the potential to move the deflecting panels, so the platform ...
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Second stage thrust used to slow first stage
Is it possible to use a large lightweight sail deployed on the first stage shortly after separation from the second stage to receive exhaust thrust from the second stage engine, so as to slow the ...
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Deriving the thrust of a rocket
I understand the the thrust of a rocket is given by
$$F_x = M_e V_e - M_i V_i + (P_e - P_i) A_e$$
However when I try to derive it myself using Reynold's transport theorem I get the following:
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