36 votes

Why doesn't JWST use ion thrusters?

Since the L2 point is unstable, JWST needs engines to maintain it's orbit. It uses mono-propellant engines which have given it a 10 year (maximum) lifespan. The JWST uses bi-propellant engines (...
David Hammen's user avatar
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32 votes
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Going from LEO to lunar using only low-thrust ion propulsion - can it be done?

The piece that you are asking about not only can be done, but it has been done. SMART-1 was launched in to GTO in 2003 and entered orbit around the Moon in 2004, using only an Ion engine to do so. It ...
PearsonArtPhoto's user avatar
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27 votes
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How many ion thrusters would be needed to accelerate a 1000 tonne craft at 9.8m/s²?

You can't do it. It's impossible. Each thruster provides thrust, but each thruster has mass, as do the power sources needed to power them and the tanks to store their fuel. No currently existing ion ...
ikrase's user avatar
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23 votes
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Overcoming the speed of light thanks to ion thrusters

The expression $v_e = \sqrt{\frac{2Vq}{m}}$ is a non-relativistic approximation. This is quite valid when the exhaust velocity is small compared to the speed of light, which is the case for ion ...
David Hammen's user avatar
  • 73.8k
23 votes

Why doesn't JWST use ion thrusters?

@DavidHammen's answer goes a long way towards answering, especially in that the space telescope's bus was finalized quite a long time ago when ion propulsion was much less a proven long-term reliable ...
uhoh's user avatar
  • 149k
20 votes
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Why can't we use charged fine metal dust instead of plasma for ion thruster?

In an ion thruster, particles are accelerated because of their electrical charge. The force acting on them is proportional to the charge (and the external field applied, which we can treat as fixed ...
asdfex's user avatar
  • 15k
20 votes

Have light gases like hydrogen or helium been explored for ion propulsion?

(Top edit: The Question asserts "Xenon and krypton are popular despite their heavy mass" and asks about exploring H or He ion propellants for improved Isp. This answer shows that lighter is not ...
Bob Jacobsen's user avatar
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16 votes
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Maximum grid voltage of ion thruster

Ion engines balance two different kinds of efficiency: $I_{sp}$ which is basically "reaction mass efficiency". For that you want the highest possible exhaust velocity, which will be helped ...
Steve Linton's user avatar
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16 votes

Does Krypton or Xenon produce more thrust in a Hall-effect thruster?

All your analysis is fully correct. At the same voltage and mass flow rate, Krypton produces more thrust. But you're missing one very important point: None of the existing applications is limited by ...
asdfex's user avatar
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16 votes
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Moon landing with ion thrusters

This is one of the cases where Kerbal Space Program differs significantly from real world rocketry. The stock ion engine in KSP has a thrust of 2000 N at 250kg, a thrust-to-weight ratio of 4.9 on the ...
SE - stop firing the good guys's user avatar
15 votes

Why are Ion Thrusters so energy hungry?

A conventional thruster with two liquid propellants requires energy too. But it is chemical energy stored in the propellants. Ion thrusters use no chemical energy at all, all the energy of the ion ...
Uwe's user avatar
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14 votes
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Ion Thruster Thrust Calculation Problem

I'll first try to independently reproduce your calculation: The thrust force is the transfer of momentum per unit time: $$F = \frac{dp}{dt}.$$ Assuming ions accelerate by mutual Coulomb repulsion with ...
uhoh's user avatar
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14 votes
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Will an array of multiple ion engines still be more efficient than a single chemical engine?

While this seems like a good idea at first, you very quickly run into the main problem with ion engines: their tiny thrust. Let's compare a typical ion engine from the Dawn mission and an upper stage ...
Jack's user avatar
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13 votes
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Could cosmic rays be produced by alien propulsion systems?

I can't give a precise answer to your primary question besides "Extremely unlikely", but here are some facts on cosmic rays that might help coming to a conclusive answer: Current models are able to ...
asdfex's user avatar
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13 votes
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Could a cubesat propel itself to Mars?

I am assuming you mean by propulsion by the CubeSat itself. Not at the moment! Mostly because of the throughput (thruster lifetime) constraint on small Electric Propulsion (EP) thrusters designed for ...
Knudsen Number's user avatar
12 votes
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Why are Ion Thrusters so energy hungry?

The thing to notice about this type of drive is that the ions encounter the positively charged accelerating grid first. The ions that provide the thrust to the rocket are positively charged as well, ...
Mark H's user avatar
  • 286
12 votes

Are any electrically propelled missions to the outer solar system being planned? If not why not?

No, there are no planned missions using an Ion drive to the outer solar system. The reason is something that you haven't taken in to account. Sunlight drops significantly as one goes further from the ...
PearsonArtPhoto's user avatar
  • 121k
12 votes

If LOX/LH2 were used in a fuel cell powering an ion engine could it provide a greater delta-v than with a conventional engine?

TLDR: Yes, but probably no, well maybe. Fundamentally, the second law of thermodynamics is about entropy: If you create it, part of the energy budget of a running engine has to be spent on getting ...
Bob Jacobsen's user avatar
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11 votes
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Thrust vectoring for ion propulsion - any plans or current research?

The ion engines on Deep Space 1 and Dawn were gimbaled. If you are going to operate one engine, it pretty much has to be gimbaled or vectored to direct the thrust, on average, through the CG (center ...
Mark Adler's user avatar
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11 votes

Thrust and rotation strategy to circularize a standard GTO orbit using ion propulsion?

TL; DR: Trajectory optimization for continuous thrust is difficult and this field is very active in research. 2021 clarifications: Methodology For the least amount of fuel, the best is the thrust the ...
ChrisR's user avatar
  • 6,220
11 votes
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VLEO - ion thrust using atmospheric molecules?

ESA is working on such an engine. an ESA-led team has built and fired an electric thruster to ingest scarce air molecules from the top of the atmosphere for propellant, opening the way to ...
Hobbes's user avatar
  • 127k
11 votes

Maximum grid voltage of ion thruster

Knowing that the thrust is proportional to the grid voltage Almost correct! All else equal, the thrust will be proportional to the ion velocity, which will vary as the square root of their kinetic ...
uhoh's user avatar
  • 149k
10 votes
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What would the rocket equation look like for 4 ion thrusters?

The number of thrusters doesn't matter (that will change how quickly you can execute your $\Delta v$, not the ultimate amount of change you can perform). Just take the efficiency figure from the ...
BowlOfRed's user avatar
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10 votes

Thrust of ion thruster when spacecraft is charged

This is a great question! To first order charging doesn't matter. What matters is the exit velocity of the ions, determined by the acceleration potential difference $V_b$. In a simple situation the ...
uhoh's user avatar
  • 149k
10 votes
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How much of the world's xenon has been used in spaceflight altogether? Is it a lot? Did it cost a lot?

According to Wikipedia's article about xenon, the gas occurs at 87 ppb (parts per billion) by volume in Earth's atmosphere. Earth's atmosphere weighs 5.15×1018 kg. Dividing this by the density of air (...
flhl1010's user avatar
  • 116
9 votes

Why can't we use charged fine metal dust instead of plasma for ion thruster?

Ion thrusters work so well because they have a very high exhaust velocity. This is made possible by the fact you're using individual atoms as the propellant. Metal powder consists of much larger, ...
Hobbes's user avatar
  • 127k
9 votes

Why are Ion Thrusters so energy hungry?

There is a sense in which the wonderfully high ISP of ion thrusters is the cause of their energy hunger, independently of the detail of their operation. It works like this: we need a certain amount ...
dmckee --- ex-moderator kitten's user avatar
9 votes
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Can a solar sail be added to an ion engine and work better?

Intro This is a tricky question, primarily because solar sails benefit from a low mass spacecraft and with the addition of an electric propulsion system, you are increasing the mass decreasing the ...
SoRobby's user avatar
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