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I have been thinking on controlled de-orbiting of Satellites.

You can carry a supply of conventional chemical fuel, and use it to apply a delta-V that would de-orbit them. There are also methods of using drag, solar wind pressure etc.

I however am interested in knowing whether there's enough material in LEO / MEO that we can use as a fuel to do this, so what we don't have to carry fuel with us.

Let us ignore the commercial viability for a start.

Option 1 : Hydrogen from Solar wind

This is unlikely, as the earth's magnetic field blocks the Alpha particles (H⁺) ions.

Option 2 : Meteors

Ignoring the complexity of capturing them, they are sporadic.

With that in mind, my specific question is :

Is / are there any material available at the LEO/MEO region that a satellite can capture and use as it's fuel to create a thrust?

That is, is/ are there possibilities of creating fuel in-situ in LEO / MEO ?

EDIT I am open to learning about fuel ( that burns with oxidizer also collected / synthesized insitu) , propellant (like a ion engine propellant) and reaction mass.

Thank you

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  • $\begingroup$ Do you mean to ask about "fuel" or just "propellant" or "reaction mass"? To burn hydrogen as fuel, you need an oxidizer (like oxygen for example) otherwise it doesn't do anything for you as fuel. However, you could put a gas in an ion engine and ionize it and accelerate it, and that would be both a propellant and a reaction mass. You could also collect meteorites, then shoot them out the back, and that would be a reaction mass, but not a fuel. The hardest part about a fuel is finding an oxidizer to burn it with. $\endgroup$
    – uhoh
    Commented May 24, 2021 at 23:22
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    $\begingroup$ Either. I am adding the edits $\endgroup$
    – Sean
    Commented May 25, 2021 at 0:53

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You can always increase existing dV from drag by not only passively "ploughing" through thermosphere/exosphere molecules around, but actively accelerating them in the opposite direction. Because relative velocity against upper atmosphere will be approximately orbital (~7 km/s) and ion thrusters are able to accelerate propellant to a few 10s km/s, you have some factor to gain here.

There is actually an ESA project targeting exactly this -- air breathing ion engine for operation in extremely low orbit, though the intended purpose is opposite, that is to fight the drag, it shows clearly that with an ion thruster, there is realistic possibility to gain more delta-V than what will be generated by drag. Directing the thrust against orbital motion could be some (minor?) technical issue, but likely no principal obstacle.

Because upper atmosphere molecules are the most abundant mass around in LEO and MEO (and readily available anywhere along orbit), I do believe it is the most realistic option in the spirit of your question. (If other means of deorbiting without reaction mass -- tethers and magnetic field, solar sails, etc. whatever would be more practical is a different issue.)

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Short answer: no.

When you are talking about going to asteroids or other planets to produce fuel (and then transport it back to LEO), well, sure, that's possible, and we already do this. We "travel" to the third planet from the sun, produce "in-situ" propellant, and then lift it to LEO.

Propellant from an asteroid would cost exponentially more to produce, and would likely be further away from a delta-V perspective. Which is worse on just about every front.

The only way in-situ production makes sense is if it's actually in-situ, near the location where you're going to need it.

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