Questions tagged [propulsion]

Systems for propelling a spacecraft from one place to another, such as rockets.

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51
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3answers
126k views

How fast will 1g get you there?

If you have the energy for a constant 1G thrust, how long would it take to get to the planets in our solar system? How long for the 5 nearest solar systems? Assuming turn over and decelerate at ...
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2answers
775 views

The Orbital Mass Accelerator Engine Theory

Can 2 satellites equal in weight traveling on the same orbital path in the opposite directions intersect and propel each other to gain altitude in orbit? Can orbital perturbation be negated during ...
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9answers
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Tiny emergency propulsive device if stuck floating in a large volume in microgravity

The questions here in SXSE Can you swim in space? and in Physics SE How to escape the center of a room without gravity? [closed] both address aspects of how to move if stuck floating in the center of ...
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1answer
8k views

Rocket Engine Plumbing: Still don't understand the Full Flow Staged Combustion Cycle

I just found this incredible video KSP Doesn't Teach: Rocket Engine Plumbing and ran through it a few times. It's very helpful in the way it outlines the various issues first, and then designs the ...
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6answers
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Can you tack against the sun using a solar sail?

Solar sails are a great, inexpensive way to move out from the sun, if you’re not in a hurry. Ocean going ships are able to tack against the wind, and to move up wind. Could a solar sail gain inbound (...
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3answers
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Could radiated heat propel space-craft in outer space?

The comment chain on What is the feasibility of launching a probe to Sedna? indicates RTG thermocouples decay. With the passage of time the thermocouple may even have the ability to transduce an ...
2
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1answer
366 views

MARS-CAT; What is a Cubesat Ambipolar Thruster and how does it work?

Trying to understand ion thrusters a little, I started looking at https://en.wikipedia.org/wiki/Ion_thruster#Propellants where I saw: The CubeSat Ambipolar Thruster (CAT) used on the Mars Array of ...
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2answers
445 views

What could go wrong if someone overpowered an ion engine?

The X-3 ion engine is the most powerful ion engine ever made, and puts out an astounding 5.4 N of force, using 103 kW. It's fuel is inert xenon gas, ionized and heated to a plasma. Now, what would ...
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3answers
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Starting a liquid fuel engine in zero gravity

In zero gravity, the liquid in a fuel tank tends to form a blob in a random location, so you'd have to take precautions to make sure the fuel pump can draw fuel. In a recent question about spinning ...
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3answers
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What are the phases of ignition (and flameout) of a liquid fuel engine?

As I observed ignition of several rocket engines (Shuttle, AMDE, Lynx Suborbital, Saturn V) they all come through a couple phases - emitting various vapors, unfocused flame, etc, before the proper "...
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3answers
1k views

Can you ride a bicycle on Deimos?

Deimos is the small moon of Mars. The surface gravity is 0.003m/s2 (compare to Earth @ 9.807 m/s2). In theory a person with a bicycle could launch from and land on Deimos with a bicycle and a ramp. ...
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1answer
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Liquid fuel / Oxygen proportions

A question ive been thinking about: If an engine works of a liquid propellant(Hydrogen in this case) and LOX, is there a specific proportion required for the two chemicals to burn completely? If so ...
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8answers
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Why aren't linear aerospike engines in common use?

Linear aerospike engines are an old idea that seem so full of promise. Why are they not widely used today by the likes of Boeing, SpaceX, etc.?
16
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4answers
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Could a ship take off from Earth using ion thrusters?

If you had enough ion thrusters, could you take off from Earth's surface into low Earth orbit? If not, why not?
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2answers
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Solar sail thrust calculation

In Space Mission Engineering: The new SMAD, page 555, section 18.7.2, the following thrust formula is given for a solar sail: $$F=\frac{2RSA}{c}\sin^2\theta=9.113\times10^{-6}\frac{RA}{D^2}\sin^2\...
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2answers
890 views

The “Em Drive” paper is out - need some help understanding it

Scott Manley tells us (see Engadget also) that the reaction-less drive peer reviewed paper is out, and nicely explains the basics. If it works, it would violate the long-held belief that linear ...
11
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2answers
861 views

Could Earth-lunar flybys be repeated consecutively without the use of propellant?

Ever since a recent orbital mechanics question, lunar flybys have been nagging me in the sense that there is obviously energy available in the system. I'm interested if you could get a repeatable ...
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4answers
2k views

What kind of engine does this Isp = 1600 refer to? Is it cubesat-friendly?

These two good answers (one and two) to the question "Is there a maximum Isp for 'exothermic chemical reaction rockets?'" put the limits around 500-550 seconds for the limits of practical ...
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1answer
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How does tank pressurization work?

I know the basic premise of tank pressurization. A inert gas (usually Helium) is kept in small tanks in or around the large propellant tanks, and when propellant is burned the helium fills the empty ...
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4answers
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Can gunpowder get you to the moon?

In 'From the Earth to the Moon' (1873) by Jules Verne, A huge cannon is used to send a spaceship to the moon. A lively discussion in chapter IX leads to using 400,000 pounds of fulminating cotton to ...
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4answers
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When the ISS accelerates, do the astronauts feel it?

The ISS has thrusters to avoid debris and to combat orbital decay. Do the astronauts feel the station accelerating? Do they have to hold onto something and is it the same when they rotate the station ...
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1answer
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What is the performance of ion thrusters in actual deployed spacecraft?

Which spacecraft / satellites currently deployed in space (2015) use ion thruster propulsion and how do they compare? The wikipedia article have some comparative numbers, but some of the engines on ...
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5answers
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What is total impulse?

I'm acquainting myself with space propulsion and I'd love a good definition of total impulse beyond just a derivation. Why is it important? How does it related to other key metrics for propulsion ...
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2answers
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Thrust vectoring for ion propulsion - any plans or current research?

While most applications of ion thrust involves long "burns" with either a tiny, slow rotation or none, in the case of this question: Thrust strategy to circularize a standard GTO orbit using ion ...
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Why do we use the gravitational acceleration at the Earth's surface when calculating the specific impulse of an engine?

So one of the ways of calculating Isp is: $$I_{sp} = V_e /g_0 $$ You divide the effective exhaust velocity by acceleration at earth's surface. This gives you a number in seconds, and is generally ...
7
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2answers
937 views

From the General Thrust Equation towards Tsiolkovsky, how to explain dropping these terms along the way?

The NASA Glen Research Center tutorial page Rocket Thrust Equation links to the General Thrust Equation page which starts with: Which transcribes into MathJax as: $ \ \ \ F = \dot{m}_\mathrm e V_\...
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Is it more efficient to assemble spacecraft in orbit, or assemble on the ground and launch?

My friends and I were trying to figure this out a while ago. I was thinking that by transporting smaller pieces into space via a lighter re-entry spacecraft, there would be overall less fuel used ...
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3answers
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What propulsion methods does the ISS use for station-keeping?

The International Space Station is constantly losing orbital energy due to atmospheric drag. How does station-keeping work for the ISS? What sort of propulsion system is used to keep it in the desired ...
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4answers
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Do rocket engines have shock absorbers?

With a million pounds of thrust and many g of acceleration and a significant fraction of a g of vibration, connecting the engine to the rocket can't be trivial. At launch the mass is very high and ...
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3answers
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Could a cubesat be self propelled to the moon from LEO?

Is it possible with current technologies to propel a cubesat, which is launched from Earth, to the moon? If current propulsion systems are able to do so, how do I continue the research in this topic ...
8
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2answers
372 views

How is charge dissipated in ion-propulsed spacecraft?

I understand that an ion-thruster will continuously charge its spacecraft with a charge opposite of the one of the ions it thrusts. Over a long journey this charge would be considerable. What would ...
5
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1answer
405 views

Could the helical engine work?

A helical engine is originally described in this NASA Paper; see also the youtube explanation by Anton Petrov The problem may be with powering the device. The original paper uses ions in a toroid to ...
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4answers
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Is this really Rosetta's orbit around 67P?

From this link I fount the following representation of Rosetta's orbit relative to 67P: A video from ESA depicts a similar orbit. My questions are: is that really the relative orbit? If yes: why ...
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3answers
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Has any CubeSat flown with an active propulsion system?

CubeSats are small, but so are some propulsion systems (cold gas thrusters, for instance, really aren't too complex and can be low volume/mass). Has any CubeSat actually flown with its own propulsion ...
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2answers
3k views

Space travel using constant acceleration drive: Earth to Europa

Long story short: I'm writing sci-fi and taking my protagonist to Europa. He's got 2 weeks to one month to get there from Earth, give or take a few days. That sounds, of course, preposterous in this ...
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2answers
12k views

What powers New Horizons?

What does New Horizons use to keep itself traveling (so far), while keeping all of its monitoring and communication systems active? I did read that it leveraged force from a gravity sling shot from ...
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4answers
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How big would a manned ascent stage for Mars need to be?

For a manned mission to Mars that isn't a one-way trip, we'll need an ascent stage that can reach orbit from Mars' surface. How big would this need to be to transport e.g. 3 astronauts to orbit? We've ...
7
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1answer
480 views

Non-vacuum ion propulsion

Are there any ion thrusters which could conceivably provide thrust inside the atmosphere? Not that they'd have enough thrust to take off under their own power, of course; I'm just wondering whether ...
14
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1answer
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Are MMH and UDMH interchangeable?

Can Monomethylhydrazine and Unsymmetrical dimethylhydrazine be used one in place of another for the class of the existing orbital maneuver engines (with reduced performance may be)? Such as Shuttle's ...
3
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1answer
751 views

How do you determine what the temperature will be in the combustion chamber of a rocket engine?

I am guessing it is dependent on the fuel and oxidiser and the chamber pressure but is there an equation that would calculate the chamber temperature?
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2answers
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Why Use Helium?

I apologize in advance if this question has already been asked and answered elsewhere, but why do RP-1/LOX rocket systems use helium for propellant tank pressurization? I understand the fact that O2 ...
6
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1answer
637 views

Density of propylene when used as rocket fuel, and advantages (if any) over RP-1?

Recently Vector space from USA has said that propylene is a better choice of fuel than RP-1. See Ars Technica's After a decade of testing, propylene rocket fuel may be ready for prime time Why is ...
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3answers
435 views

If specific impulse is directly related to exhaust velocity, would a ion post-accelerator improve the Isp of a propulsion system?

I understand that ion- and hall thrusters resemble a particle accelerator, and that led me to wonder if a post-accelerator (particle accelerator) used to boost the velocity of the ions would improve ...
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3answers
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What exactly causes stranded upper stages to explode?

Usually if an upper stage experiences a failure before it can "passivate" itself (empty tanks, drain batteries, etc.), it's only a matter of time before it explodes. For recent examples, see any of ...
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1answer
737 views

What contributes the majority of the mass in an ion drive?

In another question I've been corrected that batteries don't weigh that much in ion drive powered probes. Well, I thought a can of xenon would have a chance to be lighter than a solid block of ...
18
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1answer
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Why the non-symmetric design of rocket nozzles?

Although I have seen many perfectly symmetric nozzles, I have also seen designs such as this (Virgin Galactic) which is only symmetrical about one axis: Why is this?
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3answers
444 views

Harpoon propulsion - what would be the problems?

Let's imagine we have finally developed buckytube rope. A couple hundred kilometers of rope, able to tug a 100-ton craft at 6g acceleration, in a package packable on said craft. A near-earth asteroid ...
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2answers
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“Magic Space Unicorns” disproven? Any technical write-ups of the explanation of Em-Drive results presented at Space Propulsion 2018?

@Antzi's answer to EM drive requirements links to the recent Ars Technica article NASA’s EM-drive is a magnetic WTF-thruster; Test reveals that the magic space unicorns pushing the EM-drive are ...
6
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2answers
267 views

Using lower stage as reaction mass

As I was thinking about the process of stage separation, I realized the empty stage dropped, often many tons, is usually separated quite gently, moving at sluggish couple of m/s or less away from the ...
4
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1answer
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Pump requirements in rotating detonation engines

The recent Wired article After 60 Years, Explosion-Powered Rockets Are Nearly Here about progress on rotating detonation engines contains the following quote: A rotating detonation engine doesn’t ...