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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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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 ...
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299 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 ...
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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 (...
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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 ...
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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 ...
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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. ...
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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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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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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 ...
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59 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 ...
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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 this and this) thrust does not seem to need to be angled. ...
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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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217 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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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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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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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 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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197 views

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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163 views

Angled thrusters on the Soyuz 2.1a?

I saw a satellite launch recently (launch link) which used the Soyuz 2.1a rocket. Shortly after the launch I observed 4 symmetrical thrusters at an angle to the main thrust line. Is this for ...
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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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What single figure best compares the mass launch capacities of different rockets?

How much kinetic energy does a given launch give its payload? Could all launches be fairly lined up according to one single scalar representing how much kinetic energy they have actually delivered to ...
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323 views

How to convert from tons to kilonewtons?

How do a go from a thrust of 66.28 t to kilonewtons? thrust: 66.28 t isp: 237.2 s burn: 34 s These values are from ...
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Mathematical reasoning behind pe=pa leading to maximum thrust

I've been looking at both the thrust and thrust coefficient equations (below) and I understand that they will be optimum in a vacuum when $P_a=0$. But, I see in textbooks that $p_e=p_a$ corresponds to ...
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How do you calculate total Thrust and Specific Impulse for a rocket stage?

Given the stage has the following configuration: Thrust 741.4 kN (Main) 47.1 kN (Vernier) Specific impulse 297.999 s (Main) 288.999 s (Vernier) How ...
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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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How can I obtain the necessary thrusts / mass flow rates to achieve a given burnout velocity for an optimally staged rocket?

I understand how to use lagrange multipliers to obtain the optimal stage masses given the payload mass, the burnout velocity, the structural ratios of each stage and the specific impulses of each ...
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641 views

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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Is this equation for NEP thrust correct?

I have bolded the part that I am most interested in checking, because I am not sure if the formula is valid. I have been using Excel to find the thrust, power, etc for a NEP mission. I have been ...
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342 views

How do you calculate delta v and thrust for a given time? [closed]

Okay, so assume you have an electric propulsion (no Oberth effect) spacecraft leaving from Earth escape (for example) to Mars (for example). You want to get there much faster than a Hohmann transfer ...
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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 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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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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315 views

Orbit Maneuvering

I am working on a project of simulating orbit maneuvering. I have interfaced SGP4 with my current simulation code, however I realized that the orbit maneuvering cannot be done using SGP4. I am aware ...
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Linear Control Lock?

Assume a spacecraft with a less-than-perfect maneuvering thruster configuration such that in a particular attitude while attempting to dock, the thrusters will not allow translation along a particular ...
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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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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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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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Limiting factors of liquid rocket engine thrust

What are the limitations for the 1st stage liquid fueled rocket engines that are currently in widespread use, what are the factors that limit their total thrust? Why can't you just inject more and ...
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481 views

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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What does a high Hall Effect Parameter mean in MPD thrusters?

MagnetoPlasmaDynamic Thrusters are plasma thrusters in which the acceleration of the fluid (plasma) is carried in a electromagnetic way. The electric field and the lorentz force are the primary causes ...
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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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543 views

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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340 views

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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Does releasing a gas propellant in a vacuum produce thrust? [Martian Spoilers] [duplicate]

I recently watched, The Martian and was wondering about some of the manoeuvres and propulsion in space. My question is, how is this possible? How can escaping an escaping gas (from a pressurised ...
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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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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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How much thrust to launch a regulation size FIFA soccerball into orbit

How much thrust is necessary to launch a regulation size FIFA soccer ball into orbit around the Earth? Let us assume a size 5 which weighs between 420g and 450g. Remember, we will need thrust to ...
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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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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 ...