World-first Firing of Air-breathing Electric Thruster
Air-breathing ion thruster (Credit: ESA/Sitael)
PARIS (ESA PR) — 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.
Air-breathing space mission (Credit: ESA–A. Di Giacomo)
Replacing onboard propellant with atmospheric molecules 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.
Air-breathing electric propulsion (Credit: ESA–A. Di Giacomo)
“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, which was performed in a vacuum chamber by Sitael in Italy, 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.
Air-breathing ion thruster (Credit: ESA/Sitael)
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.
Thruster with xenon propellant (Credit: ESA/Sitael)
A two-step design ensures better charging of the incoming air, which is harder to achieve than in traditional electric propulsion designs.
“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 air molecules to a level where thruster ignition could take place, and measure the actual thrust.
Thruster with air (Credit: ESA)
“At first we checked our thruster 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.
“Finally, the system was 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.”
This project was supported through ESA’s Technology Research Programme for developing promising new ideas for space.
28 responses to “World-first Firing of Air-breathing Electric Thruster”
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I have not heard of this before and it sounds very interesting lots of potential, first thoughts of Musk’s satellites the lower they can fly the better the reception on earth and the faster the network speed. But there will be many possibilities for satellites that stay up at under 200 km. Any defining reason this would not work?
Oxidation of electrodes and other reactions may shorten it’s life but other than that no reason it shouldn’t work
Should work as long as the thrust generated is greater than air drag. This is something that would definitely need a test flight to prove the concept works “in the real world”.
There is also question of size and how that practical that may make it for vleo
I’d like to see more details on their collector design, as past US-based air-breathing electric propulsion studies had always run into really poor collection efficiencies when using passive collector designs (funnels, etc). The worse your collection efficiency, the higher the exhaust velocity has to be with the particles that do get captured in order to make up drag forces. Hopefully there will be a paper out on the concept explaining what they did differently.
~Jon
Does this system go back and forth between engine fuels? Xenon until there is a build up of enough O2 then it switches burns that and switches back to xenon?
That was my first thought – demonstrating an engine design in a vacuum chamber that can generate thrust from a low density atmosphere, is a long way from proving that an actual spacecraft can generate more thrust than drag. Presumably, even if the drag were greater than the thrust, such a spacecraft would still be able to utilise whatever thrust it produces to increase its time in low orbit, but would it be worth the cost?. There are many ideas floating about that seem to be principally motivated by finding innovative ways of compensating for expensive launch, e.g. reusing upper stages (such as ACES), lunar propellant mining, satellite servicing, etc.. Many or even all of these ideas could well be made redundant by the reduced launch costs of fully reusable launch. It will be interesting to look back in the years to come, to see how many of these survive BFR and its clones.
A fair number will survive reducing the bottom line is always a worthwhile goal
“…reducing the bottom line is always a worthwhile goal”
Well that’s my point. Spending millions or billions on strategies to mitigate high launch costs, may well no longer make sense when launch costs reduce dramatically. For example, multi-use of an ACES upper stage becomes a ridiculous suggestion alongside a fully reusable and far more capable BFS.
ACES as is sure, but if you see its architecture as the basis of a reusable tug, it can compliment bfs in making delivery of secondary payloads easier
Not a hope. BFS may lift tugs and propellant, but not a hope in hell will it be lifting an ACES upper stage or refuelling one. Tugs will either be purpose made permanent in space vehicles, most likely solar electric. Any chemical propellant tugs would either be BFS or single use.
Sep tugs are WAY too slow the whole point is to get to final orbit faster, so you need chemical, sep for return sure but chemical is needed to make it a worthwhile service
So you have a fully reusable launch system that can put 150 tonnes to LEO for $10 million and you have several LEO constellations that make GEO satcomms and large swathes of terrestrial based comms redundant. What exactly then is it that needs to get to a final orbit faster, or otherwise makes the low cost launch system not a worthwhile service. If you are desperate to use chemical prop rapid for orbital insertion, you could launch BFR 7 times in 7 days to 7 for the cost of a single Falcon 9 launch, or 21 times in 21 days for the price of a Vulcan launch with an ACES upper stage. You seem to be thinking of ways to use a low cost high capability fully reusable launch system as a better way to do yesterdays’ space operations. Cheap launch changes the game.
Anything that isn’t a primary payload that wants a specific orbit in less time
If bfr is booked out or you are a smaller company, a chem tug rideshare makes sense
About three years back someone was on The Space Show describing a concept where a satellite was in an elliptical orbit with a very low perigee and thrusting during the longer time it was out of the upper atmosphere in order to maintain its orbit. It strikes me that this would yield an even lower perigee than if it constantly remained in the upper atmosphere. The application would be for Earth imaging.
Boy, this is a huge deal and useful for planet exploration.
Hopefully, Europe and/or America will spend a lot more money on R&D ing this.
The gas collector efficiency is a major drag component, but there is another drag component as well. That is solar panels, which must also withstand the oxidation in upper atmosphere orbits. One way around that would be power beaming from earth-launched powersats in higher orbits to rectennas on these VLEO vehicles, with less drag from the rectennas and better oxidation characteristics than photovoltaics can exhibit.
It would also be a start on powering things by power beamed from one orbit to another.
That is certainly an idea worth considering, but isn’t (serious) power beaming still kind of in its infancy?
For science satellites in sun-synchronous orbits, the drag from solar panels can be eliminated by having body mounted panels (on the sun facing side) on an aerodynamic satellite body. See ESA’s GOCE mission:
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Of course that still leaves the oxidation problem to be addressed.
So there is a role to be played in space by pointy-nosed things with fins.
That thing reminds me of the opening credits of the 1980 Filmation FLASH GORDON. Not Zarkov’s rocket–tbut Mings high flying “drones” that shot it down.
Quite true, ‘Spike, but I was thinking about all the *other* orbits and uses for VLEO satellites. After all, power beaming is no more in its infancy than this propulsion technology, indeed, rather less so.
Expensive science spacecraft that need to be in VLEO for long duration missions might benefit from some sort of novel propulsion tech (though bigger xenon tanks seems the simplest solution). But when you say *other* orbits and VLEO sats, I assuming you are referring to constellations. I wonder if it wouldn’t be more cost effective to build sats for multi-thousand constellations as cheap as possible and to be replaced and improved upon at regular intervals, so that falling into the atmosphere after a few years is actually part of the design.
There are a couple answers to oxidation,
1 use rust resistant materials,
2 do nothing, instead treat it like a way to avoid the cost of acquiring xenon for your leo and vleo constellation.
Solar cells can be made from perovskite compounds. There may be one compound that resists oxidation.
Y’all realize this is how the Bussard collectors on the Star Trek USS Enterprise collect hydrogen and other matter for the IMPulse engines or matter antimatter reactions.
Not the first thruster which can breath upper atmosphere gases (or use a tanked reaction mass); MSNW in WA state has been developing their Electrodeless Lorentz Force (ELF) thruster for several years, first with the USAF (breather) then under the NASA NextSTEP-1 program.
Like a [very] low Earth orbit version of the Interstellar Ramjet!