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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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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/...
J. Doe's user avatar
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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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28 votes
2 answers
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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 ...
KarlKastor's user avatar
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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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4 answers
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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? $$F = \dot{m} V_e + (p_e - p_0) A_e$$ ...
RR batman's user avatar
2 votes
1 answer
112 views

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 ...
Xi Liu's user avatar
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3 answers
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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?
Joe Jobs's user avatar
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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 ...
uhoh's user avatar
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3 votes
1 answer
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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 ...
Valentino Zaffrani's user avatar
3 votes
1 answer
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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, ...
mad.redhead's user avatar
5 votes
3 answers
3k views

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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5 votes
1 answer
638 views

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 ...
Human of Facts's user avatar
5 votes
2 answers
1k views

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 ...
mad.redhead's user avatar
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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 ...
Ricardo Casimiro's user avatar
1 vote
1 answer
115 views

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 ...
Ricardo Casimiro's user avatar
5 votes
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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?
Aarav Prasad's user avatar
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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 ...
Justin's user avatar
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10 votes
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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})...
Ben Woodman's user avatar
5 votes
2 answers
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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 ...
Erudite Philosopher's user avatar
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230 views

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 ...
PunchyRascal's user avatar
-4 votes
1 answer
286 views

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 ...
sahil saxena's user avatar
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1 answer
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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 ...
uhoh's user avatar
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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 ...
Valentino Zaffrani's user avatar
1 vote
1 answer
79 views

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 ...
Watch This's user avatar
21 votes
3 answers
6k views

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 ...
user34435's user avatar
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4 votes
0 answers
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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 ...
Russell Borogove's user avatar
1 vote
1 answer
269 views

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 ...
LEM's user avatar
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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 ...
uhoh's user avatar
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Can effective thrust in the more dense layers of the atmosphere be considered constant (as approximation)?

I am reading some course material about the 'Thrust load ratio'. It states the following: The thrust load ratio is: $Psi = {T \over Mg}$ $T$ being the effective thrust, equal to the actual (constant) ...
ThaNoob's user avatar
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-13 votes
4 answers
1k views

What pushes back on rockets? [closed]

Discussion: I have removed the parts of the question regarding landing and the conic nozzle. Adding in those issues makes the question too broad. No, it makes the question meaningful. It's an ...
curiousguy's user avatar
4 votes
1 answer
979 views

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 ...
uhoh's user avatar
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4 votes
2 answers
748 views

Compressed gas thruster for an orbital launch vehicle?

Is it possible for a compressed gas thruster to be used to launch a spacecraft into orbit? Let's say, it's already moving at 250MPH(111.7 meters/second) relative to the planets surface. Planets ...
mzs.112000's user avatar
1 vote
0 answers
200 views

What was the maximum thrust the RS-25 was capable of producing?

The Rocketdyne RS-25, a large hydrolox engine best-known in its role as the main engines (SSMEs) of the space shuttle orbiter, was originally certified to a thrust level of 1.67 meganewtons (mN) at ...
Vikki's user avatar
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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 ...
uhoh's user avatar
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2 votes
1 answer
914 views

Under-expanded nozzle at sea level - is it a problem?

I'm designing a solid rocket motor with a fixed pressure in the combustion chamber $p_{cc} = 70~bar$. When it comes to the choice of the right nozzle, I have to consider the proper expansion ratio, in ...
Nicola's user avatar
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4 votes
2 answers
1k views

Some exercise questions about Tsiolkovsky's Rocket Equation and Thrust Equation

I have found 6 of the question's answers, but I don't know they are correct. The last question about time of the burn I get negative result -0.42 seconds. Time could not be a negative value, so I ...
M. Çağlar TUFAN's user avatar
8 votes
1 answer
337 views

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 ...
cosmic_tintin's user avatar
4 votes
3 answers
448 views

How much of the exhaust speed is due to combustion and how much is due to the injection?

The thrust $F$ of a rocket engine is given by $$F=\dot{m}v$$ where $\dot{m}$ is the mass flow and $v$ is the exhaust speed. Now the first factor, $\dot{m}$, is almost entirely due to the turbo pumps (...
Everyday Astronaut's user avatar
3 votes
1 answer
447 views

What is the order of magnitude forces due to Earth's magnetic field, sunlight, drag, oblateness and tidal forces compare?

What in order of magnitude does pressures vary in LEO due to diamagnetic repulsion of Earth's magnetic field, sunlight, drag, oblateness and tidal forces compare on an ideal satellite? Is there any ...
Muze's user avatar
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1 vote
1 answer
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Is there enough energy in a rocket nozzle for fission?

How much more energy does the rocket exhaust atom have to have to be before fission can occur to create more thrust? Which exhaust byproduct atom would be the easiest to split? I understand in ...
Muze's user avatar
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4 votes
1 answer
3k views

How can a rocket approaching the Karman Line then return to earth faster than 53 m/s terminal velocity?

In the book, How to Make a Spaceship: A Band of Renegades, an Epic Race and the Birth of Private Spaceflight the opening chapter details the June 2004 attempt to take SpaceShipOne to the Karman Line. ...
Venture2099's user avatar
21 votes
2 answers
3k views

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 ...
karthikeyan's user avatar
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10 votes
3 answers
3k views

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. ...
DrSheldon's user avatar
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2 votes
1 answer
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SRB ejection methods [duplicate]

While an empty GEM-60 is just under 2 tons, it occurred to me that additional thrust could be generated by jettisoning the empty boosters (or a large portion of them) BEHIND the Delta IV rather than ...
Isaac Kotlicky's user avatar
2 votes
1 answer
164 views

What is intermediate thrust and brief pause for checkout on launching Soyuz spacecraft?

In a book I'm reading, the author mentioned the launch of Soyuz spacecraft as follows: What made it more spectacular was how close we were when it lifted off the launch pad. Yuri, Tim and I were ...
trequartista's user avatar
8 votes
1 answer
953 views

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 ...
uhoh's user avatar
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5 votes
2 answers
535 views

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 ...
Vikki's user avatar
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6 votes
1 answer
1k views

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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