Questions tagged [propulsion]

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

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50
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3answers
121k 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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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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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
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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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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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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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2answers
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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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1answer
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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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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.?
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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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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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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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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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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 ...
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855 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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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 chemical ...
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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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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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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 ...
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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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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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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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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 ...
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2answers
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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 ...
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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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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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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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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 ...
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1answer
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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 ...
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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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1answer
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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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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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1answer
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How much time does it take to circularize a GTO orbit using ion propulsion?

SpaceX launched two GEO comsats, and is about to launch two more, that use all-electric ion propulsion. Now, I'm wondering, how much time would it take to actually make a satellite like that ...
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3answers
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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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2answers
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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 ...
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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
728 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 ...
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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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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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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 ...
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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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Is warp drive a legitimate avenue of scientific investigation?

I've been reading a number of online "pop-sci" articles on the subject of "warp drive" - derived from work done initially by Alcubierre. Some of the most recent articles say that there are ...
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Why is using a space elevator cheaper than rocket power?

Why is rocket power so much less efficient? In both cases you want to lift a given weight a certain height. What does climbing a tether give you that you don't have when using rockets? Wouldn't a ...
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Why are Ion Thrusters so energy hungry?

Ion thrusters need a lot of energy. But I don't understand why. So, one thing I understand is that it takes a lot of energy to achieve a high exhaust velocity (since kinetic energy is proportional to ...
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Can ion thrusters be scaled up?

All ion thrusters are quite small. Having read through the more approachable information about them, as they use physics pretty beyond me, I don't understand what it is about them that makes it ...
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Methods for propulsion other than rockets for leaving Earth's atmosphere?

Due to the large amount of energy required, the standard method for leaving the Earth's atmosphere is rocket propulsion. Is there any other methods in development that don't involve rockets? E.g. ...
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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 ...
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1answer
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How much delta-v can be achieved by venting the ISS atmosphere?

A sort-of follow-up to What do the astronauts do whilst the air-lock cycles? The ISS fact-sheet writes to say Pressurized Volume: 32,333 cubic feet (916 cubic meters) Elsewhere on the stack are ...