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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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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 ...
G11's user avatar
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4 votes
2 answers
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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 ...
Tom's user avatar
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3 votes
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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 ...
Tyreeze's user avatar
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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 ...
Anish Kommireddy's user avatar
3 votes
3 answers
158 views

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 ...
Andy Woolford's user avatar
3 votes
1 answer
153 views

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 ...
confused_aspirant's user avatar
2 votes
1 answer
205 views

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 ...
Kevin's user avatar
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2 answers
184 views

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.
Bob Bobb's user avatar
0 votes
1 answer
667 views

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?
FalconHeavy321's user avatar
0 votes
1 answer
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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?
FalconHeavy321's user avatar
3 votes
2 answers
345 views

Something doesn't add up when calculating thrust for Starlink satellites

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 ...
Playstation_waifu's user avatar
0 votes
1 answer
106 views

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?
Niranjan's user avatar
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15 votes
2 answers
3k views

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?
The Rocket fan's user avatar
1 vote
1 answer
148 views

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?
FalconHeavy321's user avatar
17 votes
1 answer
2k views

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” ...
Woody's user avatar
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735 views

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 ...
The Rocket fan's user avatar
-3 votes
1 answer
174 views

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?
Peanut 's user avatar
6 votes
2 answers
411 views

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 ...
Ögmundur Eiriksson's user avatar
2 votes
1 answer
258 views

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. ...
Woody's user avatar
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3 votes
1 answer
229 views

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 ...
geoffc's user avatar
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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 ...
suitsme's user avatar
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3 votes
1 answer
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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 ...
boarbytes's user avatar
3 votes
3 answers
531 views

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?
Ashvin's user avatar
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2 votes
1 answer
93 views

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 ...
Artem Shamsutdinov's user avatar
0 votes
2 answers
417 views

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 ...
Alice Miller's user avatar
1 vote
0 answers
46 views

Matching reference thrust to engine given certain parameters

I am running a simulation where a reference thrust value is meant to be matched by a liquid engine which I know the following information about: $"F_{vac}=100000"$ N, $I_{sp}=364$ sec, $D_e=1.01$ m, $...
alexmesa's user avatar
0 votes
0 answers
53 views

Analytical representations for thrust in underexpanded flow (P_e>P_a) [duplicate]

I am familiar with the ideal thrust equation: $F=\dot{m}U_e +(P_e-P_a)A_e$ When $P_a$ is greater than $P_e$, you have thrust losses, and the equation accounts for that. When $P_a=P_e$, you achieve ...
alexmesa's user avatar
2 votes
2 answers
189 views

How and who calculated the thrust required from first stage of launch vehicle Saturn V for moon landing?

Given the lack of clarity about weight of CM, SM and LEM while designing Saturn V, how and who calculated the thrust required from first stage of launch vehicle (Saturn V), for moon landing? were the ...
Niranjan's user avatar
  • 3,796
0 votes
1 answer
81 views

Is the momentum thrust of a liquid rocket engine in a static test fire the same as in flight?

Assuming vacuum exit conditions are matched by means of a suitable ejector mechanism, is the exhaust velocity of combustion products relative to static engine the same as that of a flying rocket ...
Jithin's user avatar
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1 vote
1 answer
302 views

Cold Gas Thruster to space engineering challenges

I have seen this question. The natural extension of this question would be - could you lift a human or an equivalent payload to LEO with cold gas thruster only? For numbers, take 100 kg mass for the ...
Sean's user avatar
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21 votes
3 answers
3k views

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,...
Woody's user avatar
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3 votes
1 answer
290 views

Where do the numbers 101,972 and 3,600 come from in terms of Thrust-Specific Fuel Consumption (TSFC or SFC)?

Online, on sites such as Wikipedia's for Specific Impulse and Thrust-specific fuel consumption, there are these units: 101,972/x g/(kN·s) and 3,600/x lb/(lbf·hr) Perhaps 3600 comes from the number of ...
Kurt Hikes's user avatar
2 votes
1 answer
284 views

Thrust needed for Ion Thruster Lift off from Earth surface

I've been calculating the needed mass flow rate for a hypothetical ion rocket, lifting off from Earth's surface and propelled with a Dual-Stage 4-Grid ion thruster. Data given: mass of the spaceship /...
sea_for's user avatar
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0 votes
1 answer
81 views

Study of selection higher stages for a multistage rocket

Will it be correct to say that the thrust produced by the first stage is the ultimate limiting factor for a rocket's ability? The logic behind this thought is like this: Higher quantity of its ...
Niranjan's user avatar
  • 3,796
3 votes
0 answers
996 views

What is the maximum thrust of the Starlink satellites?

As in the title, what is the maximum thrust (in N) that the satellites of the Starlink constellation can achieve? I read that they use Hall-effect thrusters, but I couldn't find a specification of the ...
cholo14's user avatar
  • 273
0 votes
1 answer
231 views

How do you calculate thrust produced by a rocket engine?

I was planning on building a water-powered rocket. I also wanted to know how high my rocket might go. Could someone help me figure out, how to calculate thrust produced by a rocket engine?
Ishaan Manish's user avatar
1 vote
0 answers
412 views

How to propagate the trajectory in GMAT with a custom thrust profile

So basically I was trying to design a low thrust maneuver to increase the apogee of the spacecraft. I solved it separately and got some thrust profile (thrust and it's direction as a function of time)....
Aryan's user avatar
  • 11
5 votes
3 answers
1k views

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 ...
mylifeforaiur's user avatar
3 votes
0 answers
121 views

Making sense of rocket engine thrust calculation [closed]

Recently I've been trying to design a hypothetical rocket engine using the mass flow rate, exit mach, temperature, and pressure calculations provided by NASA's own website. I've come to know quite ...
R. Hall's user avatar
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6 votes
0 answers
230 views

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 ...
uhoh's user avatar
  • 149k
3 votes
1 answer
188 views

Thrust requirements from Saturn 1 rocket's first stage

What was the need / trigger to develop Saturn I rocket, and who defined / what dictated the thrust requirements from Saturn I, so that eight number of H1 engines had to be clustered to achieve that ...
Niranjan's user avatar
  • 3,796
7 votes
2 answers
1k views

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 ...
Niranjan's user avatar
  • 3,796
3 votes
2 answers
257 views

Can pyroxene and other silicon compounds be used as a theoretical spacecraft fuel?

I have been reading this patent, which led me to this paper. The first uses polysilane, which basically replaces the $\text{C}$ in a $\text{-R-C-R-}$ group, making an $\text{-R-Si-R-}$ group. I also ...
Sean's user avatar
  • 213
1 vote
1 answer
543 views

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 ...
user avatar
10 votes
1 answer
1k views

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 ...
Niranjan's user avatar
  • 3,796
4 votes
2 answers
1k views

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 ...
user avatar
7 votes
5 answers
1k views

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 ...
Chris Collett's user avatar
1 vote
0 answers
73 views

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 ...
Luke's user avatar
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1 vote
0 answers
69 views

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....
JKamue's user avatar
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2 votes
1 answer
213 views

Could New Horizons' thrusters' ISP be as low as 157 sec?

A discussion below How much of a deep space spacecraft's structural mass is useless dead weight after launch? Any plans to shed it in the future? has lead to https://nssdc.gsfc.nasa.gov/nmc/...
uhoh's user avatar
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