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 (...
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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 ...
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  • 119k
28 votes
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Why do ion thrusters frequently use xenon as the reaction mass?

Xenon is the heaviest non-radioactive elemental inert gas. The added mass allows for denser packing at less pressure. The mass is one of the limiting factors, so having a more dense gas helps ...
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  • 119k
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 ...
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  • 8,401
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 ...
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  • 65.5k
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 ...
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  • 148k
22 votes
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Why aren't there any space tugs in use?

While the ISP on Ion thrusters is awesome, the overall thrust is pretty low. Thus the transit time from LEO to GEO would be quite long and slow. In some cases this matters. If it takes an extra year ...
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22 votes
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How will the ion thruster powered Dawn spacecraft enter orbit around Ceres?

Does it have any additional thrusters? Not to thrust towards its targets. For that, it's 100% ion thruster propelled. It does also have a set of 12 MR-103G variable thrust (0.9 N maximum) RCS (...
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  • 75.6k
22 votes
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Can ion thrusters be scaled up?

Assuming you mean "quite small" in terms of mass as well as thrust output. Fundamentally, current ion drives are limited by the amount of power available to them - it takes many, many ...
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  • 8,715
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 ...
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  • 13.3k
19 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 ...
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  • 12.3k
18 votes

How large a body could a probe with ion engines land on and launch from?

Here's how you can work it out. First, thrust in kilo-Newtons (kN) divided by mass in metric tons yields acceleration in meters-per-second-per-second. Divide by 10 to get acceleration in approximate ...
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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 ...
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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 ...
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14 votes
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General guidelines for modeling a low thrust ion spiral?

The rule you have for the total $\Delta V$ of a low-thrust spiral is an upper limit arrived at as you let the thrust go to zero. However that takes an infinite amount of time. The total $\Delta V$ ...
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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 ...
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  • 148k
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 ...
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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 ...
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  • 13.3k
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 ...
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12 votes

Can ion thrusters be scaled up?

Leaving aside the power consumption problems (which have been well discussed in other answers) and returning to the part of the question where you asked: Are they [Ion Thrusters] fundamentally ...
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  • 7,089
12 votes
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What is the performance of ion thrusters in actual deployed spacecraft?

Dawn and Deep Space 1 both use the NSTAR ion engine - I got my stats from a mix of sources so there may be small differences between the engines used on the two spacecraft, but they seem to be pretty ...
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12 votes

Can ion thrusters be scaled up?

While their ISP is insanely good, ion thrusters have miserable T/W ratio, less than 1/1000th of unity; you simply cannot take off from any large body with them, no matter how many of them you use. ...
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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, ...
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  • 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 ...
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  • 119k
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 ...
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  • 12.3k
11 votes

Why aren't there any space tugs in use?

A single-use, disposable ion drive can be made no larger than it needs to be, thus uses no more fuel than it needs to. A reusable ion drive tug, first of all, has to take its payload to destination, ...
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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 ...
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  • 5,795
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 ...
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  • 122k
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 ...
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