World-first firing of air-breathing electric thruster

March 6, 2018, European Space Agency
Air-breathing ion thruster. Credit: ESA/Sitael

In a world first, 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 satellites flying in very low orbits for years on end.

ESA's GOCE gravity-mapper flew as low as 250 km for more than five years thanks to an electric thruster that continuously compensated for air drag. However, its working life was limited by the 40 kg of xenon it carried as propellant – once that was exhausted, the mission was over.  

Replacing onboard propellant with atmospheric would create a new class of satellites able to operate in very low orbits for long periods.

Air-breathing electric thrusters could also be used at the outer fringes of atmospheres of other planets, drawing on the carbon dioxide of Mars, for instance.

"This project began with a novel design to scoop up air molecules as propellant from the top of Earth's atmosphere at around 200 km altitude with a typical speed of 7.8 km/s," explains ESA's Louis Walpot.

A complete thruster was developed for testing the concept by Sitael in Italy, which was performed in a vacuum chamber in their test facilities, simulating the environment at 200 km altitude.

A 'particle flow generator' provided the oncoming high-speed molecules for collection by the Ram-Electric Propulsion novel intake and thruster. 

A future air-breathing space mission in low orbit around Earth: propelled at around 7.8 km/s, the satellite would ingest air molecules from the top of the atmosphere (left) to fire its ion thruster (right), providing thrust to overcome atmospheric drag, allowing it to stay in low orbit indefinitely. Credit: ESA–A. Di Giacomo

There are no valves or complex parts – everything works on a simple, passive basis. All that is needed is power to the coils and electrodes, creating an extremely robust drag-compensation system.

The challenge was to design a new type of intake to collect the air molecules so that instead of simply bouncing away they are collected and compressed.  

The molecules collected by the intake designed by QuinteScience in Poland are given electric charges so that they can be accelerated and ejected to provide thrust.

Sitael designed a dual-stage thruster to ensure better charging and acceleration of the incoming air, which is harder to achieve than in traditional electric propulsion designs.   

Molecules of air at the top of the atmosphere are captured by a novel type of intake, then collected and compressed to the point of becoming thermalised ionised plasma, at which point they can be given an electric charge to accelerate them and eject them to provide thrust. Air-breathing electric propulsion could make a new class of long-lived, low-orbiting missions feasible. Credit: ESA–A. Di Giacomo
"The team ran computer simulations on particle behaviour to model all the different intake options," adds Louis, "but it all came down to this practical test to know if the combined intake and thruster would work together or not.

"Instead of simply measuring the resulting density at the collector to check the intake design, we decided to attach an electric thruster. In this way, we proved that we could indeed collect and compress the to a level where thruster ignition could take place, and measure the actual thrust.

"At first we checked our could be ignited repeatedly with xenon gathered from the particle beam generator."

As a next step, Louis explains, the xenon was partially replaced by a nitrogen–oxygen air mixture: "When the xenon-based blue colour of the engine plume changed to purple, we knew we'd succeeded.

The air-breathing thruster was initially run with standard xenon propellant, causing a bluish plume, which was then progressively replaced with a mixture of nitrogen and oxygen to represent Earth's atmosphere. Success was marked by the thruster plume changing to purple. Credit: ESA/Sitael
"The system was finally ignited repeatedly solely with atmospheric propellant to prove the concept's feasibility.

"This result means air-breathing electric propulsion is no longer simply a theory but a tangible, working concept, ready to be developed, to serve one day as the basis of a new class of missions."

Fired at first using standard xenon propellant, the test thruster was then shifted to atmospheric air, proving the principle of air-breathing electric propulsion. Credit: ESA

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33 comments

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skystare
5 / 5 (8) Mar 06, 2018
Like a non-nuclear version of a Bussard ramjet . . .
TheGhostofOtto1923
5 / 5 (1) Mar 06, 2018
Like a non-nuclear version of a Bussard ramjet . . .
Put an RTG on it and you will have something.
Thorium Boy
2.5 / 5 (2) Mar 07, 2018
There are two methods of propulsions worth a cent for space. RTG powered space probes and nuclear bomb powered manned spacecraft. The ridiculous chemical rockets are only fit for Earth orbit delivery of small items. If they ever want meaningful exploration of space, 1000 year old Chinese gunpowder won't do it.
Da Schneib
4.7 / 5 (3) Mar 07, 2018
OK, so how much power did it use? And how much thrust did it produce?
TheGhostofOtto1923
3 / 5 (2) Mar 07, 2018
TB thinks that there are only
two methods of propulsions worth a cent for space. RTG powered space probes and nuclear bomb powered manned spacecraft
- But he is apparently unaware of nuclear thermal propulsion...

"Part of NASA's Game Changing Development Program, the Nuclear Thermal Propulsion (NTP) project could indeed significantly change space travel, largely due to its ability to accelerate a large amount of propellant out of the back of a rocket at very high speeds, resulting in a highly efficient, high-thrust engine. In comparison, a nuclear thermal rocket has double the propulsion efficiency of the Space Shuttle main engine"

and

"Russia has announced that it will test a nuclear engine in 2018 that could help cosmonauts reach Mars in just six weeks..."

-meaning that he is seriously uninformed on the subject.
Gigel
5 / 5 (2) Mar 07, 2018
That engine may have the potential to accelerate a space probe to escape velocity or higher by flying it low for a long time. But it might require to fly much lower than this engine - say at 50-100 km altitude.
ScottyB
3 / 5 (1) Mar 07, 2018
Like a non-nuclear version of a Bussard ramjet . . .

Pretty much what i thought!
Now if they can get them to collect He3 and we fuel up at Sarurn!
Eikka
4 / 5 (3) Mar 07, 2018
But he is apparently unaware of nuclear thermal propulsion...


Nuclear thermal propulsion doesn't come close to the specific impulse of ion drives, though.

Direct propulsion by a NERVA type engine achieves impulses of about 900 seconds, while a VASIMR can get over 10,000 seconds. Specific impulse is impulse produced per unit of propellant expended, effectively thrust-seconds per mass flow.

The difference is that an NTP can produce a large kick and fast acceleration but uses proportionally more fuel, so it doesn't have as much delta-V. The ion engine has low thrust, but it uses proportionally less fuel, runs longer and thus in the end it gets there faster.

Eikka
4.3 / 5 (3) Mar 07, 2018
But high power ion engines can't run off of solar panels or RTGs because the power density is not high enough. You need a proper nuclear reactor to get the 200+ kW power output.
Da Schneib
3 / 5 (6) Mar 07, 2018
@Eikka, if the propellant is ambient and the power is ambient, then the thrust can be applied whenever it is useful, without consumables. We're not talking about interplanetary travel but about keeping satellites in orbit. Solar panels with accumulators on the satellite seem fine to me since it's all free. What's your problem? Rightwingnut philosophy again?
Eikka
2.3 / 5 (3) Mar 08, 2018
@Eikka, if the propellant is ambient and the power is ambient, then the thrust can be applied whenever it is useful, without consumables. We're not talking about interplanetary travel but about keeping satellites in orbit. Solar panels with accumulators on the satellite seem fine to me since it's all free.


There's probably a very delicate balance for how low it can go, because drag increases, and how high it can go, because the available air decreases.

Adding huge solar panels increases more drag than thrust. Adding more power to the thruster adds linearily to the area of solar panels needed, to the collector funnel area, and the larger size of the vehicle to support those panels increases its mass and drag coefficient more than linearily, so there's some optimum size and level of thrust.

In other words, the satellite is going to be rather small.

What's your problem? Rightwingnut philosophy again?


You're nuts.
Eikka
2.7 / 5 (3) Mar 08, 2018
There is no problem, just a comparison of different technologies and applications.

If you construe that as an attack, Da Schneib, the problem is between your ears. You block where there's no strike, and strike back with insults and accusations where there's no fight.

You always complain about me because you think telling the full story about something means a person is attacking it, or attacking you somehow.
KBK
not rated yet Mar 08, 2018
If they manage to get it to work and begin to orbit them, there is the small problem of not knowing what the change to the upper atmosphere will do to the whole atmospheric envelope.

Nice idea, but without knowing exactly any potential for atmospheric change dominoes are...it ends up being risky. Possibly even suicidal. We don't know. at all.

So don't fucking stick shit into the the upper atmosphere, that changes it, until you have even one tiny bit of a handle on what it will do.

We'v got exactly ONE atmosphere for 7 billion and this is at the minimum -a wild card. and no clue what it might do.

Thus, trashcan this thing, indefinitely.
Da Schneib
3.6 / 5 (7) Mar 08, 2018
If 40kg of xenon could keep a satellite in orbit at these levels for 5 years, according to the ESA using solar power to do it, then what? http://www.esa.in...tched_on

Maybe you should read the article more carefully instead of knee-jerking about how it won't work because there's not enough power in solar energy like you usually do.

So much for the "full story." You left a pretty important part out, again like you usually do.
BCL1
4 / 5 (4) Mar 08, 2018
That's nice show for masses - but air, or even propellant may not be actually necessary: http://astronomys...d.html..

Asimov: "Any sufficiently advanced technology is indistinguishable from magic."

-- It was Clarke, not Asimov.
Da Schneib
3.4 / 5 (7) Mar 08, 2018
And why is it that you always have an "It'll never work" excuse when solar power is mentioned, @Eikka?

Every

Single

Time.

Your agenda is to deny it continuously, even when the proof it works is right there in your face. That's what's nutty. And that's why I call you a rightwingnut. Because you are.
antialias_physorg
4.8 / 5 (5) Mar 08, 2018
If they manage to get it to work and begin to orbit them, there is the small problem of not knowing what the change to the upper atmosphere will do to the whole atmospheric envelope.

OK...seriousy...you need to get to grips with something called 'orders of magnitude'. Your 'argument' is like "we shouldn't swim in the ocean, because drops adhere to our skin when we leave - we might empty the ocean !!11!!1!1 Stop doing it!!1"
TheGhostofOtto1923
3 / 5 (1) Mar 08, 2018
There is a pulsed variant of the NTP, the pulsed nuclear thermal rocket, "a type of nuclear thermal rocket concept developed at the Polytechnic University of Catalonia, Spain and presented at the 2016 AIAA/SAE/ASEE Propulsion Conference for thrust and specific impulse (Isp) amplification in a conventional nuclear thermal rocket... The gained energy -by pulsing the nuclear core, can be used for thrust amplification by increasing the propellant mass flow, or using the intensive neutron flux to produce a very high specific impulse amplification"

"In summation, NASA's current reasoning is that a NPR can be developed that would be twice as efficient as its chemical counterpart, though it is likely such an engine would only be used beyond the Earth's atmosphere."

Then theres this
https://en.wikipe...c_rocket

-Many variables makes it hard to compare with ion engines.
TrollBane
5 / 5 (2) Mar 08, 2018
Otto's Ghost is right about the pulsed nuclear thermal rocket being a very interesting idea. It's not an ion engine, but the theoretical specific impulse is very high compared even to a solid core NTR.
TheGhostofOtto1923
not rated yet Mar 09, 2018
Otto's Ghost is right about the pulsed nuclear thermal rocket being a very interesting idea. It's not an ion engine, but the theoretical specific impulse is very high compared even to a solid core NTR.
But as eikka implies, how does it compare to a VASIMR-type engine? Is it more efficient in the end to convert reactor heat to electricity for accelerating ions, or to use it directly, all things considered?

I looked but couldn't find an answer.
carbon_unit
5 / 5 (3) Mar 09, 2018
ESA article:
https://www.esa.i...thruster

Neither really describes the collector. They just show the air particles looking like they are being drawn into the thruster somehow. Is there some sort of collector field, like a Bussard ramjet or just a physical intake? How big does the intake need to be? "Ignition" seems like a strange concept too.

If this works, it could be major. It would be possible to operate satellites in really LEO.
* Good place for communication satellite constellations - they are closer to their ground terminals; both could operate at lower power levels.
* Self cleaning orbits. If a satellite fails (enough), its thruster would die and the satellite would more rapidly deorbit. At end of life, just turn the engine off. Any debris from its orbital insertion would also happen lower and deorbit.
* higher LEOs safer for humans with more lower stuff lower.
TechnoCreed
5 / 5 (3) Mar 09, 2018
@carbon_unit
The third image from your link is teh intake. Here is a paper that give more information on the intake desigh. http://erps.space...-271.pdf
TrollBane
5 / 5 (2) Mar 09, 2018
Otto, have you looked at the Atomic Rockets site? http://www.projec...list.php
carbon_unit
5 / 5 (3) Mar 10, 2018
@carbon_unit The third image from your link is teh intake. Here is a paper that give more information on the intake desigh. http://erps.space...-271.pdf
@TechnoCreed, Ah, thanks, I did not click on the image and get that description. Those lines showing air molecules curving into the intake are rather bogus then. (Haven't read paper yet...)

Like a non-nuclear version of a Bussard ramjet . . .
Put an RTG on it and you will have something.
@otto We're talking about LEO air-breathing satellites here which will almost certainly de-orbit at end of life. Nuclear power sources are a Really Bad Idea.
TheGhostofOtto1923
2 / 5 (1) Mar 11, 2018
@otto We're talking about LEO air-breathing satellites here which will almost certainly de-orbit at end of life. Nuclear power sources are a Really Bad Idea
The topic shifted. Did you miss it?

What makes you think anyone would actually want fissiles in sats that would randomly fall to earth? Are you that stupid??
TheGhostofOtto1923
not rated yet Mar 11, 2018
Is it more efficient in the end to convert reactor heat to electricity for accelerating ions, or to use it directly, all things considered
The higher speed of ions, the better efficiency. The speed of ions from direct heating nuclear engines is limited by their temperature, which is limited by material used (graphite? tungsten?).
Yeah so? What other factors can you think of which would affect overall suitability for a given application?
carbon_unit
5 / 5 (1) Mar 11, 2018
The topic shifted. Did you miss it?
Oh well, shift happens... http://dilbert.co...97-03-22
carbon_unit
5 / 5 (3) Mar 11, 2018
If they manage to get it to work and begin to orbit them, there is the small problem of not knowing what the change to the upper atmosphere will do to the whole atmospheric envelope.

Nice idea, but without knowing exactly any potential for atmospheric change dominoes are...it ends up being risky. Possibly even suicidal. We don't know. at all.

So don't fucking stick shit into the the upper atmosphere, that changes it, until you have even one tiny bit of a handle on what it will do.

We'v got exactly ONE atmosphere for 7 billion and this is at the minimum -a wild card. and no clue what it might do.

Thus, trashcan this thing, indefinitely.

Except this engine uses the upper atmosphere without injecting anything into it. Also, it allows satellites to operate in lower orbit, reducing fuel needed. It prolongs the life of satellites in low orbit, avoiding the need for additional launches of replacements. Those launches do put stuff into all levels of the atmosphere.
TheGhostofOtto1923
not rated yet Mar 11, 2018
Oh well, shift happens... http://dilbert.co...97-03-22
What, this?
"Can Humans and Computers Mate and Have Babies?
by Scott Adams"

-I don't get it.
carbon_unit
not rated yet Mar 12, 2018
Hmm, the full link is http:!!dilbert.com!strip!1997-03-22 , replacing ! with / .
I don't know what you got... (Which reminds me of a Far Side involving Indians and egg beaters, but I'll not go there...) I wish they would not screw with links like that. You should see the correct link when you hover on my post and the click through works correctly.
TheGhostofOtto1923
not rated yet Mar 12, 2018
Yeah i was making a little 'joke' yes?
carbon_unit
not rated yet Mar 28, 2018
Another advantage of this is that it would allow LEO satellites to change their orbits as often as desired without fuel concerns. That would be a good bit of flexibility to have.
Bryan_Kelly
not rated yet Mar 29, 2018
This is a big step ahead on the way to a light-breathing hydrogen-light pump-jet thruster.

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