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Questions tagged [propulsion]

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

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66 votes
3 answers
173k 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 ...
James Jenkins's user avatar
14 votes
9 answers
3k views

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 ...
uhoh's user avatar
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7 votes
4 answers
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 ...
uhoh's user avatar
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6 votes
2 answers
867 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 ...
Muze's user avatar
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12 votes
1 answer
11k 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 ...
uhoh's user avatar
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3 votes
2 answers
1k 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 ...
uhoh's user avatar
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51 votes
7 answers
9k views

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 (...
James Jenkins's user avatar
41 votes
4 answers
5k views

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 ...
matt's user avatar
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4 votes
2 answers
1k 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 ...
AndrewMaxwellRockets's user avatar
2 votes
1 answer
581 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 ...
uhoh's user avatar
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29 votes
3 answers
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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 ...
Hobbes's user avatar
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17 votes
3 answers
3k views

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 ...
Everyone's user avatar
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13 votes
3 answers
3k views

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 ...
uhoh's user avatar
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12 votes
3 answers
7k views

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\...
ChrisR's user avatar
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12 votes
3 answers
2k 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. ...
James Jenkins's user avatar
11 votes
3 answers
3k views

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 "...
SF.'s user avatar
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7 votes
1 answer
7k views

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 ...
user148532's user avatar
5 votes
1 answer
1k 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 ...
Jay Laughlin's user avatar
4 votes
1 answer
497 views

Why might krypton have a lower utilization fraction than xenon for ion propulsion, and what can be done to improve it?

A comment below Why will Starlink satellites use krypton instead of xenon for electric propulsion? links to the 2011 preprint A Performance Comparison of Xenon and KryptonPropellant on an SPT-100 Hall ...
uhoh's user avatar
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27 votes
8 answers
21k views

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.?
Travis Bear's user avatar
17 votes
3 answers
2k views

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 ...
David Fourman's user avatar
16 votes
4 answers
5k views

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?
Joe's user avatar
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12 votes
3 answers
1k 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 ...
AlanSE's user avatar
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9 votes
3 answers
10k views

Ion Thruster Thrust Calculation Problem

Trying to calculate the impulse of a little ion thruster I'm putting together. An old version of it can be found here, I'll be polarizing the AC current and putting in copper nails on the next ...
Colin Warn's user avatar
9 votes
4 answers
2k views

How are vacuum optimized engines tested without disintegrating them?

SpaceX recently test fired vacuum optimized raptor engines of starship. Doesn't vacuum optimized engines disintegrate when operated in atmosphere? If yes, what additional modifications are made to the ...
Ashvin's user avatar
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9 votes
2 answers
597 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 ...
Diomidis Spinellis's user avatar
8 votes
2 answers
342 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 ...
SF.'s user avatar
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7 votes
2 answers
2k 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_\...
uhoh's user avatar
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6 votes
1 answer
258 views

Hows does "Glenn Research Center's sapphire refractive secondary concentrator" work?

Clicking through NASA.spinoff.gov I came to the page for spinnoff 2001 Glenn Research Center and found this: Glenn Research Center's sapphire refractive secondary concentrator will be used with ...
uhoh's user avatar
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6 votes
1 answer
2k views

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 ...
Jake Blocker's user avatar
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5 votes
2 answers
804 views

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 ...
uhoh's user avatar
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4 votes
1 answer
2k 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?
Edward Jane's user avatar
59 votes
4 answers
8k views

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 ...
James Jenkins's user avatar
18 votes
1 answer
1k views

How important is plume impingement in rendezvous operations?

When performing space rendezvous operations close to the target vehicle (0-5 m relative distance), pursuer thruster escape nozzle gases can hit the target if firings are done in the direction of ...
Julio's user avatar
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18 votes
2 answers
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 ...
Ricky's user avatar
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18 votes
2 answers
1k views

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 ...
JKor's user avatar
  • 840
16 votes
3 answers
16k views

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 ...
Stu's user avatar
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10 votes
1 answer
3k views

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

Troubleshooting a DIY Ion Thruster

Been following a Make-Magazine article on how to make your own ion thruster: https://makezine.com/projects/ionic-thruster/ Went through the tutorial step by step, not seeming to get any thrust out of ...
Colin Warn's user avatar
10 votes
1 answer
533 views

STS: How much thrust did the nominal post-MECO LOX dump produce?

Following up to some questions asked in comments to the answer to this question: With pressure-fed engines, is any measurable thrust generated by venting the pressurant out the engine bell after ...
Organic Marble's user avatar
9 votes
3 answers
2k views

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 ...
reason1337's user avatar
8 votes
2 answers
2k views

"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 ...
uhoh's user avatar
  • 149k
8 votes
1 answer
829 views

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 ...
radex's user avatar
  • 1,652
7 votes
2 answers
952 views

Is this description of the "dipole drive" and how it would work physically correct?

Comments in chat have noted the recent post in the Centauri Dreams blog titled The Dipole Drive: A New Concept for Space Propulsion. In contrast to the single positively charged screen employed by ...
uhoh's user avatar
  • 149k
7 votes
2 answers
1k views

Is the propulsion for the Scorpion nuclear-thermal-electric ship concept viable and credible?

Recently I've come across the proposal for the "Scorpion" spacecraft -- I originally ran across it on Project Rho (ctrl-F for it) but it looks like the article was published in the journal ...
ikrase's user avatar
  • 8,873
7 votes
2 answers
3k views

How is it that "blow-down" propellant storage systems work in micro/ zero-gravity?

A "blowdown" pressure system is something that is extensively utilized on Earth -- with tons of applications ranging from kegs to high-tech hydraulics. This architecture focuses on adding a ...
Austin Prater's user avatar
7 votes
5 answers
16k views

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 ...
SpacePropulsion101's user avatar
5 votes
1 answer
310 views

Is there any possible reason to direct the electron gun specifically towards the ion trail behind an ion thruster?

This answer to Neutralization of ions in the ion thruster quotes the introduction to Wikipedia's Ion thruster: Temporarily stored electrons are finally reinjected by a neutralizer in the cloud of ...
uhoh's user avatar
  • 149k
4 votes
0 answers
212 views

Where can I read about Lucy's complete propulsion system?

Wikipedia's /Lucy (spacecraft) says nothing of propulsion, and it's SWRI home page for the spacecraft http://lucy.swri.edu/mission/Spacecraft.html gives specification and enumerates what's on Lucy’s ...
uhoh's user avatar
  • 149k
2 votes
1 answer
386 views

Could a CubeSat be propelled by this low-tech electromagnetic propulsion system?

I have come up with a conceptual idea for a low-tech electromagnetic propulsion system for a CubeSat, and I would like to know if it would create (on a theoretical basis) a net force strong enough to ...
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