This seems like a big deal. Assuming it could collect more than it needs to keep itself in orbit, it could refuel a tank and skip from atmospheric body to atmospheric body. Something like this could make it to Neptune and back, though it might take an incredible amount of time.
Still, atmospheric fuel scoops were still sci-fi until now, as far as I’m aware.
This is still very much sci-fi at the moment for anything flying above a 250 km earth orbit because atmospheric density decreases dramatically fast with altitude.
The missions targeted by this technology are GOCE-like spacecrafts which by design must fly low and need an insane amount of propellant to compensate for the high atmospheric drag at such altitude.
> This is still very much sci-fi at the moment for anything flying above a 250 km earth orbit because atmospheric density decreases dramatically fast with altitude.
One of my favorite takes on this concept was Poul Anderson's Tau Zero [1], which used a Bussard ramjet [2]. Apparently, in the 70s, in was thought that there was enough hydrogen surrounding our solar system to support interstellar travel.
> The missions targeted by this technology are GOCE-like spacecrafts which by design must fly low
Once the technology matures, it could be used by more missions. Flying low has its benefits:
* Lower latency for communication satellites,
* Better resolution for Earth imaging / spy satellites,
* When the satellite fails, it quickly deorbits by itself.
Until now, flying low has just not been economical, but if this thruster has similar lifetime to medium and high orbit satellites, then many more missions could choose lower orbits.
> Assuming it could collect more than it needs to keep itself in orbit, it could refuel a tank
That's not this device though, it looks like the "collected" air runs straight into the thruster, like the flow through a jet engine. No tank involved.
That's a cool thought. You could perhaps use the atmosphere of planets to accelerate at very high velocities with the energy stored between each body (which would be a lot .. ie 60 days of 24/7 solar harvesting).
The question is whether the thrust you produce is roughly linear with the energy you expel? Or does it taper asymptotic? What if the power system on the craft is titanium batteries that are designed to deliver 1 MW for say 2 minutes? Will that give you the needed acceleration in a given planets atmosphere? What if you use planetary lasers and don't need batteries at all?
Solar light isn't that strong once you go beyond mars.
Earth gets 1400 W/m^2, at Saturn only 16 W/m^2 and on Neptune maybe 1.5 W if you get lucky.
60 days of continous harvesting, assuming the spacecraft doesn't use any power (which is not true in reality), is about 2 kWh at Neptune. Not that much. Saturn would be 23 kWh.
It may not work on any planet. A fundamental design challenge is that increased size of solar panels create more drag, and increasing the height to reduce drag means it must go faster which further increases drag. While the Solar Impulse has demonstrated an equilibrium of speed-to-size can be maintained at normal altitude and low speed, we'll have to wait to see if something can be built to sustain equilibrium at these heights.
A lot; also keep in mind that air is not a finite resource, it's continually generated from e.g. electrolysis (h2o -> o) and other processes (carbon + oxide = c02, plenty of carbon on earth, plenty of oxygen). Plus as another commenter mentioned, we're already losing some air all the time anyway.
Tangentially related question - what happens to the gas used as a reaction mass in thrusters in orbit - when it's used to speed up I guess it falls down cause velocities mostly cancel out, but when it's used to slow down the ship, and engines are fired retrograde - the reaction mass has orbital velocity, right?
Does it stay in some orbit forever, like a solid object would? Can it cause gas "Kessler syndrome", with gas rings around Earth's most common reaction mass orbits?
If we choose our orbits and burn times so that this gas piles up in particular place on particular orbit, can we then reuse that as "air" for these engines from the article?
Xenon's very heavy, most of it would eventually come back down to Earth - probably sooner rather than later. Most of what we lose to deep space is hydrogen and helium. And almost none of that is from space missions, anyway, it's just Brownian motion.
It is not mentioned in detail in the article, but it's worth looking up what the GOCE satellite was. Unlike 99.9% of satellites ever built, it was designed to be shaped sort of like a rectangular missile with solar panel wings. The idea was to make it slightly more aerodynamic and thus prolong its lifespan at very low orbit altitude, with ion thruster and tank of propellant.
So, possibly dumb question: is this basically a fan without moving parts?
This is a prototype so I'm guessing the size/cost can be reduced in the future, and if it becomes small/cheap, I could see a fan without moving parts having a lot of applications.
It kind of works like an aerodynamic diode: it is much easier for the incoming particles to go through the intake tubes (because they are oriented along the spacecraft velocity vector) than to exit the collector. This is because after a they collide with surfaces inside the collector, their velocity vector is randomized and no longer aligned with the tubes.
[Edit] Mass is not such an issue when you contrast it with the mass of propellant that you save...
[Edit2] I forgot to precise that my description only pertained to the intake part: there is of course a plasma thruster at the back (no moving part either)
Definitely. Ozone is a significant irritant (although it also has an "air freshening effect", see air ionizers), to produce significant airflow I believe you'd need very large electrodes, which would produce lots of ozone. The electrodes need to be large because the voltage is limited by air's breakdown voltage, so you can't just pump up the voltage like you can (for the most part) just increase a fan's velocity.
For lack of friction/bearings a magnetic bearing fan seems like a much better option. The strength of this technology is the great exhaust velocity, which is great for space applications.
I'd be more worried about random Nitrogen Oxides (NOx) emissions, but again, too small of a volume to actually matter in any significant way. A couple of VWs are probably worse.
it ionizes the incoming gas and then accelerates it to very high speed with an electric field. My guess is that wouldn’t work well in normal atmospheric conditions but no idea really.
The main challenge is whether the ionization creates enough thrust to overcome drag; this seems to be true in the upper atmosphere, but not sure if that works in the lower. Then again, you could probably do it, but it'd require more energy.
If you're not limited by propellant, it seems like this would be really useful for satellites that need to change orbit frequently. Performing a plane change, for example, normally requires a prohibitive amount of propellant, but if that is essentially free, you can change orbit at will, albeit somewhat slowly.
Wonder if this would work nicely with a highly elliptical orbit like Molniya. When it gets closer to the atmosphere it scoops up some more gas, then when it is further away it provides nice wide coverage.
At first I thought that this was a type of magnetohydrodynamic drive[1]. I've have watched a video of one of the french scientists who has been studying electric propulsion systems. Sadly the video quickly went downhill into pure conspiracy theory realm.
Ringworld posited interstellar Bussard ramjets [1]. Since they were proposed (and Ringworld written) we have discovered there isn’t enough hydrogen in interstellar space to make such vehicles feasible.
This might be needed if we succumb to the Kessler Syndrome. By operating in the upper atmosphere, we could continue to have satellites while there's a maelstrom of high-hypersonic bullets overhead.
Yes, operating a Hall or ion thruster on O2 and/or N2 is not new (and Busek was not the only one that did it either).
And it is definitely hard, but this is just part of the problem.
The really tricky thing is to get the whole system working. For instance it is not longer possible to use a "high pressure" (relatively speaking of course) propellant feed. Even with the passive compression stage discussed in the article, an off-the-shelf thruster wouldn't be able to operate due to the low inlet pressure.
Also, the intake/collector design is a problem of its own. AFAIK this was the first real-life test for the passive intake concept (the theory of operation and trade-off to be considered are discussed here [1]).
That being said there is still a long way to go before this can work in space...
The page doesn't go into any detail, but it looks like this would require the air to come from a tank? Otherwise surely they would have mentioned it, not requiring on-board propellant is the feature of this thruster.
The air this thruster gathers isn't used as fuel, only as propellant. The energy needed to accelerate the propellant and generate thrust still has to come from somewhere.
Aircraft don't need propellant; they can simply "push off" of the air (via propellers, turbofan engines, etc); so this mechanism is useless for them. They still need fuel to run their engines, which this device doesn't provide.
Ion engines have very low thrust, so they're not suitable for in-atmosphere work. In space they can apply a gentle thrust for a long time, which is useful.
Ion engines also only typically ignite in a near vacuum as well. You would need HUGE voltages to do the same thing in the (main part of the) atmosphere.
No. This is a ion thruster, a class of thrusters which already exist and are used in various satellites. They carry a propellant (xenon), then use electricity to accelerate and shoot the propellant out the back. This provides extremely efficient, but low amount of thrust (like a nudge).
This development gets rid of the need to carry propellant. They satellite will scoop it up from the atmosphere, saving weight and prolonging life.
They just throw stuff out the back of the rocket really fast to move forward, like any other sort of rocket. The nice thing about electrical rockets is that they decouple the energy used to throw the propellant from the chemical energy generated from burning the fuel, so you can end up throwing it out fast for very efficient rockets if you have enough electricity.
No, this is actual Newtonian physics. Rockets function based on Newton's third law: every reaction creates an equal and opposite reaction. We sit on wheeled office chairs, I push you- we both move, to opposite directions.
Rockets aren't fueled by office chairs, though, but by gases. They push the gas molecules into a particular direction and themselves are pushed into another.
So, to move in space by pushing stuff, you need two things:
a) mass to push away
b) some power to do the pushing
(This ignores several categories of other forms of force generation on space craft like solar sails).
Chemical fuel rockets happen to strike two flys on one go - the mass they carry also generate the energy for the push, so that's only a matter of plumbing and hydrodynamics to get them going.
The problem with this approach, though, is that once you run out of fuel, you run out of fuel. No more chairs, no more acceleration. Refueling in space is really expensive, if you need to bring up the propellant from a deep gravity well like earths surface to the orbit (https://xkcd.com/681/).
There is no necessity the propellant (i.e the 'chairs') needs to generate the energy for pushing itself away. You can you Some Other Physics to push the propellant away from the vehicle. It works just as fine.
This system collects the fuel from sparse gas surrounding it, and expels it using an electric thruster, which probably get's it's energy from solar panels.
Potentially, like some other poster noted, you could design a spacecraft with this that once it reaches planetary orbit, it can hop from planet to planet and refuel itself indefinetly (just as long as the planets have an atmosphere).
So it's Way Cool, and this has been hypothesized in science fiction for decades, so it's also Genuine Scifi Space Tech :)
Doesn't look like it. This type of drive has been around, but the issue had been that it would run out of propellant that powered it to keep the satellite in low earth orbit. This is the successful testing of a drive of the same type, but it collects that material from the atmosphere so it hopefully it won't run out for a long time and keep missions running longer.
This seems like a big deal. Assuming it could collect more than it needs to keep itself in orbit, it could refuel a tank and skip from atmospheric body to atmospheric body. Something like this could make it to Neptune and back, though it might take an incredible amount of time.
Still, atmospheric fuel scoops were still sci-fi until now, as far as I’m aware.
This is still very much sci-fi at the moment for anything flying above a 250 km earth orbit because atmospheric density decreases dramatically fast with altitude.
The missions targeted by this technology are GOCE-like spacecrafts which by design must fly low and need an insane amount of propellant to compensate for the high atmospheric drag at such altitude.
> This is still very much sci-fi at the moment for anything flying above a 250 km earth orbit because atmospheric density decreases dramatically fast with altitude.
One of my favorite takes on this concept was Poul Anderson's Tau Zero [1], which used a Bussard ramjet [2]. Apparently, in the 70s, in was thought that there was enough hydrogen surrounding our solar system to support interstellar travel.
[1] https://en.wikipedia.org/wiki/Tau_Zero
[2] https://en.wikipedia.org/wiki/Bussard_ramjet
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> The missions targeted by this technology are GOCE-like spacecrafts which by design must fly low
Once the technology matures, it could be used by more missions. Flying low has its benefits:
* Lower latency for communication satellites,
* Better resolution for Earth imaging / spy satellites,
* When the satellite fails, it quickly deorbits by itself.
Until now, flying low has just not been economical, but if this thruster has similar lifetime to medium and high orbit satellites, then many more missions could choose lower orbits.
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This does not preclude the possibility of spacecraft doing repeated dips only on the perigee
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ISS is at 150km and needs costly refueling, right? Wouldn’t that be the most interesting applicaton in terms of cost savings?
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> Assuming it could collect more than it needs to keep itself in orbit, it could refuel a tank
That's not this device though, it looks like the "collected" air runs straight into the thruster, like the flow through a jet engine. No tank involved.
That's a cool thought. You could perhaps use the atmosphere of planets to accelerate at very high velocities with the energy stored between each body (which would be a lot .. ie 60 days of 24/7 solar harvesting).
The question is whether the thrust you produce is roughly linear with the energy you expel? Or does it taper asymptotic? What if the power system on the craft is titanium batteries that are designed to deliver 1 MW for say 2 minutes? Will that give you the needed acceleration in a given planets atmosphere? What if you use planetary lasers and don't need batteries at all?
Solar light isn't that strong once you go beyond mars.
Earth gets 1400 W/m^2, at Saturn only 16 W/m^2 and on Neptune maybe 1.5 W if you get lucky.
60 days of continous harvesting, assuming the spacecraft doesn't use any power (which is not true in reality), is about 2 kWh at Neptune. Not that much. Saturn would be 23 kWh.
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It may not work on any planet. A fundamental design challenge is that increased size of solar panels create more drag, and increasing the height to reduce drag means it must go faster which further increases drag. While the Solar Impulse has demonstrated an equilibrium of speed-to-size can be maintained at normal altitude and low speed, we'll have to wait to see if something can be built to sustain equilibrium at these heights.
"Sorry data, air may be the eventual oil."
Trivia question: How many round-trips from Neptune would it take to cause a 1% dip in Earth's air content?
Bonus question: Since the Earth is not making any more Xenon, are we losing some of this resource to the deep space every time we nudge a satellite?
A lot; also keep in mind that air is not a finite resource, it's continually generated from e.g. electrolysis (h2o -> o) and other processes (carbon + oxide = c02, plenty of carbon on earth, plenty of oxygen). Plus as another commenter mentioned, we're already losing some air all the time anyway.
Tangentially related question - what happens to the gas used as a reaction mass in thrusters in orbit - when it's used to speed up I guess it falls down cause velocities mostly cancel out, but when it's used to slow down the ship, and engines are fired retrograde - the reaction mass has orbital velocity, right?
Does it stay in some orbit forever, like a solid object would? Can it cause gas "Kessler syndrome", with gas rings around Earth's most common reaction mass orbits?
If we choose our orbits and burn times so that this gas piles up in particular place on particular orbit, can we then reuse that as "air" for these engines from the article?
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Xenon's very heavy, most of it would eventually come back down to Earth - probably sooner rather than later. Most of what we lose to deep space is hydrogen and helium. And almost none of that is from space missions, anyway, it's just Brownian motion.
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It's not Xenon you have to worry about, it's Helium. Once we run out we'll be too heavy and fall into the sun.
It is not mentioned in detail in the article, but it's worth looking up what the GOCE satellite was. Unlike 99.9% of satellites ever built, it was designed to be shaped sort of like a rectangular missile with solar panel wings. The idea was to make it slightly more aerodynamic and thus prolong its lifespan at very low orbit altitude, with ion thruster and tank of propellant.
https://en.wikipedia.org/wiki/Gravity_Field_and_Steady-State...
So, possibly dumb question: is this basically a fan without moving parts?
This is a prototype so I'm guessing the size/cost can be reduced in the future, and if it becomes small/cheap, I could see a fan without moving parts having a lot of applications.
Absolutely, this is a passive compressor.
It kind of works like an aerodynamic diode: it is much easier for the incoming particles to go through the intake tubes (because they are oriented along the spacecraft velocity vector) than to exit the collector. This is because after a they collide with surfaces inside the collector, their velocity vector is randomized and no longer aligned with the tubes.
[Edit] Mass is not such an issue when you contrast it with the mass of propellant that you save...
[Edit2] I forgot to precise that my description only pertained to the intake part: there is of course a plasma thruster at the back (no moving part either)
Is the principle behind the Feynman sprinkler involved in any way?
[0] https://en.wikipedia.org/wiki/Feynman_sprinkler
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It works by ionizing the air, so that might lead to issues with producing ozone.
Ozone in the high atmosphere is a good thing though - the ozone layer. It's only at ground level that it can act as a health hazard.
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Definitely. Ozone is a significant irritant (although it also has an "air freshening effect", see air ionizers), to produce significant airflow I believe you'd need very large electrodes, which would produce lots of ozone. The electrodes need to be large because the voltage is limited by air's breakdown voltage, so you can't just pump up the voltage like you can (for the most part) just increase a fan's velocity.
For lack of friction/bearings a magnetic bearing fan seems like a much better option. The strength of this technology is the great exhaust velocity, which is great for space applications.
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...not at the quantities this thing would make.
I'd be more worried about random Nitrogen Oxides (NOx) emissions, but again, too small of a volume to actually matter in any significant way. A couple of VWs are probably worse.
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it ionizes the incoming gas and then accelerates it to very high speed with an electric field. My guess is that wouldn’t work well in normal atmospheric conditions but no idea really.
The gas collecting portion of this design wouldn't work well, but it's certainly possible to generate thrust by ionizing air at atmospheric pressure and zero relative velocity. See https://en.wikipedia.org/wiki/Ionocraft#Mechanism and https://www.youtube.com/watch?v=vzZy1Aqleno
The main challenge is whether the ionization creates enough thrust to overcome drag; this seems to be true in the upper atmosphere, but not sure if that works in the lower. Then again, you could probably do it, but it'd require more energy.
there already are fans without moving parts, manufactured by Dyson.
Edit: wrong... see below. Thx, walrus!
They have moving parts. There's a normal fan at the bottom. See here:
https://en.wikipedia.org/wiki/Bladeless_fan
There is an ordinary fan in the base and the ring is hollow with slots in it.
If you're not limited by propellant, it seems like this would be really useful for satellites that need to change orbit frequently. Performing a plane change, for example, normally requires a prohibitive amount of propellant, but if that is essentially free, you can change orbit at will, albeit somewhat slowly.
Is no-one going to comment on how beautifully sci-fi that engine looks when running?
Wonder if this would work nicely with a highly elliptical orbit like Molniya. When it gets closer to the atmosphere it scoops up some more gas, then when it is further away it provides nice wide coverage.
At first I thought that this was a type of magnetohydrodynamic drive[1]. I've have watched a video of one of the french scientists who has been studying electric propulsion systems. Sadly the video quickly went downhill into pure conspiracy theory realm.
[1]: https://en.wikipedia.org/wiki/Magnetohydrodynamic_drive
It's a giant ionic breeze!
There are less accurate ways to explain it.
It’s an elephant!
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I just finished reading the second of the Ringworld books, and this seems very much like a first step towards the ramjets the book is all about.
so, to-do:
* find way to scoop up more incoming material
* replace electric propulsion with sth more powerful
* write smug think piece about how sci-fi guides engineering
Ringworld posited interstellar Bussard ramjets [1]. Since they were proposed (and Ringworld written) we have discovered there isn’t enough hydrogen in interstellar space to make such vehicles feasible.
[1] https://en.m.wikipedia.org/wiki/Bussard_ramjet
I haven't read Ringworld, but are you sure that it is not describing this already existing technology?
https://en.wikipedia.org/wiki/Ramjet
This might be needed if we succumb to the Kessler Syndrome. By operating in the upper atmosphere, we could continue to have satellites while there's a maelstrom of high-hypersonic bullets overhead.
Interesting - was just reading this morning about Astranis & their low-orbit satellites to supply more of the world with broadband
Seems like a tie-in, although Electric Thrusters themselves look bigger than the satellites right now.
That's everything I know about both subjects, so no idea if this is a useful comment or not :-)
Astranis is launching satellites to GEO [1], i.e., not low.
[1] https://techcrunch.com/2018/03/01/astranis-emerges-from-stea...
You're right. The article I read was more business oriented and used both terms, and I didn't notice.
kind of offtopic, I was reading yesterday about this new Hall thruster from NASA [0]. Amazing achievment!
[0] https://news.engin.umich.edu/2017/10/thruster-for-mars-missi...
This is just an application of the Biefeld-Brown effect (also seen in ionocraft and "lifters"). Nice to finally see it in use in satellites, though. https://en.wikipedia.org/wiki/Biefeld%E2%80%93Brown_effect
First thought was, what other industries and applications could this potentially serve?
Except it's not the first: http://www.busek.com/technologies__hall.htm
Yes, operating a Hall or ion thruster on O2 and/or N2 is not new (and Busek was not the only one that did it either).
And it is definitely hard, but this is just part of the problem.
The really tricky thing is to get the whole system working. For instance it is not longer possible to use a "high pressure" (relatively speaking of course) propellant feed. Even with the passive compression stage discussed in the article, an off-the-shelf thruster wouldn't be able to operate due to the low inlet pressure.
Also, the intake/collector design is a problem of its own. AFAIK this was the first real-life test for the passive intake concept (the theory of operation and trade-off to be considered are discussed here [1]).
That being said there is still a long way to go before this can work in space...
[1] http://erps.spacegrant.org/uploads/images/2015Presentations/...
The page doesn't go into any detail, but it looks like this would require the air to come from a tank? Otherwise surely they would have mentioned it, not requiring on-board propellant is the feature of this thruster.
How much thrust does this produce?
forgive my ignorance, but....could this be applied to aircraft? Make a near fuel-less jet?
The air this thruster gathers isn't used as fuel, only as propellant. The energy needed to accelerate the propellant and generate thrust still has to come from somewhere.
Aircraft don't need propellant; they can simply "push off" of the air (via propellers, turbofan engines, etc); so this mechanism is useless for them. They still need fuel to run their engines, which this device doesn't provide.
Ion engines have very low thrust, so they're not suitable for in-atmosphere work. In space they can apply a gentle thrust for a long time, which is useful.
Ion engines also only typically ignite in a near vacuum as well. You would need HUGE voltages to do the same thing in the (main part of the) atmosphere.
Spelling error in title. Should be ... Electric Thruster
I thrust it will be fixed.
Whoops! Yes, I fixed it. Thanks for noticing. :-)
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reddit is leaking
I had to reread this headline a few times, believing "Electric Truster" to be the esoteric job title of someone recently fired.
Can this be used in a sort of merry go round sling-by-scramjet to propell something at high speed near a gasgiant?
So, just to be clear (because I don't see it mentioned anywhere). Are we taking about the EMDrive here?
No. This is a ion thruster, a class of thrusters which already exist and are used in various satellites. They carry a propellant (xenon), then use electricity to accelerate and shoot the propellant out the back. This provides extremely efficient, but low amount of thrust (like a nudge).
This development gets rid of the need to carry propellant. They satellite will scoop it up from the atmosphere, saving weight and prolonging life.
So "air collecting" or "mass collecting" would be more accurate since it doesn't really breath like a typical air breathing engine?
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This is a customized Hall thruster.
Disclosure: I was involved in that project.
Do you know, is related to this study? [0]
[0] http://erps.spacegrant.org/uploads/images/images/iepc_articl...
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They just throw stuff out the back of the rocket really fast to move forward, like any other sort of rocket. The nice thing about electrical rockets is that they decouple the energy used to throw the propellant from the chemical energy generated from burning the fuel, so you can end up throwing it out fast for very efficient rockets if you have enough electricity.
http://hopefullyintersting.blogspot.com/2015/03/rockets-elec...
ELY 5:
No, this is actual Newtonian physics. Rockets function based on Newton's third law: every reaction creates an equal and opposite reaction. We sit on wheeled office chairs, I push you- we both move, to opposite directions.
Rockets aren't fueled by office chairs, though, but by gases. They push the gas molecules into a particular direction and themselves are pushed into another.
So, to move in space by pushing stuff, you need two things: a) mass to push away b) some power to do the pushing
(This ignores several categories of other forms of force generation on space craft like solar sails).
Chemical fuel rockets happen to strike two flys on one go - the mass they carry also generate the energy for the push, so that's only a matter of plumbing and hydrodynamics to get them going.
The problem with this approach, though, is that once you run out of fuel, you run out of fuel. No more chairs, no more acceleration. Refueling in space is really expensive, if you need to bring up the propellant from a deep gravity well like earths surface to the orbit (https://xkcd.com/681/).
There is no necessity the propellant (i.e the 'chairs') needs to generate the energy for pushing itself away. You can you Some Other Physics to push the propellant away from the vehicle. It works just as fine.
This system collects the fuel from sparse gas surrounding it, and expels it using an electric thruster, which probably get's it's energy from solar panels.
Potentially, like some other poster noted, you could design a spacecraft with this that once it reaches planetary orbit, it can hop from planet to planet and refuel itself indefinetly (just as long as the planets have an atmosphere).
So it's Way Cool, and this has been hypothesized in science fiction for decades, so it's also Genuine Scifi Space Tech :)
Doesn't look like it. This type of drive has been around, but the issue had been that it would run out of propellant that powered it to keep the satellite in low earth orbit. This is the successful testing of a drive of the same type, but it collects that material from the atmosphere so it hopefully it won't run out for a long time and keep missions running longer.
From a cursory reading, it doesn't sound anything like that at all.
https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster
Don't think so. Sounds like it accelerates air particles using electricity.