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World-first firing of air-breathing electric thruster
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.
[...] 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.
"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.
(Score: 3, Interesting) by UncleSlacky on Wednesday March 07 2018, @11:11AM
Finally! About time the electrokinetic/ionocraft/lifter/"Biefeld-Brown" technology was adapted for use in space.
https://en.wikipedia.org/wiki/Biefeld-Brown_effect [wikipedia.org]
(Score: 0) by Anonymous Coward on Wednesday March 07 2018, @11:21AM (6 children)
Will this allow ISS to stay in orbit, without frequent fuel resupplies?
(Score: 2) by beckett on Wednesday March 07 2018, @12:05PM
the mean height of ISS is just above 400km [heavens-above.com]; the project only tested at height of 200km, which was about as high as Sputnik-1 got.
(Score: 3, Informative) by c0lo on Wednesday March 07 2018, @12:39PM (4 children)
No, the air acts as a propelant, the spent energy is electric. You'll need to supply the electricity somehow.
If you think PV panels, there's a trade-off: the panels will create drag.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by fyngyrz on Wednesday March 07 2018, @01:30PM (1 child)
Even scooping up gas molecules adds drag.
However, integrated conformal PV panels can be designed on such that they don't add drag.
All of this is a balancing act. If the sum total of the thrust generated by gas molecules + impetus added by the electrical system is greater than the drag, and can be directed where it needs to go, the system can work.
(Score: 2) by c0lo on Wednesday March 07 2018, @02:18PM
This is why I said 'trade off' rather than 'outright impossible'.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by JoeMerchant on Wednesday March 07 2018, @01:45PM (1 child)
I was thinking of a new generation of satellites with hypersonic aero-design like a Blackbird... lay the PV panels along the body, might not be enough to keep it up (7-8km/s aerodrag has got to be a bitch to overcome...) but maybe with a nice hot plutonium pile onboard...
🌻🌻 [google.com]
(Score: 3, Informative) by richtopia on Wednesday March 07 2018, @06:52PM
The image from the article is similar to what you describe:
http://www.esa.int/spaceinimages/Images/2018/03/Air-breathing_space_mission [esa.int]
(Score: 0) by Anonymous Coward on Wednesday March 07 2018, @12:07PM
No mention about the achieved thrust though. Anyone here who has more info?
(Score: 0) by Anonymous Coward on Wednesday March 07 2018, @12:14PM (1 child)
It looks more like a Hall thruster [wikimedia.org] than an ion thruster [wikimedia.org].
Note [esa.int] the annular channel and the cathode on the side.
(Score: 0) by Anonymous Coward on Saturday March 31 2018, @04:20PM
So it does. Good catch. That also greatly increases the viability, because Hall thrusters have a much longer operating life than other ion drive systems.
(Score: 2) by JoeMerchant on Wednesday March 07 2018, @01:27PM (10 children)
Will be impressive, indeed, if the thruster doesn't have to be as large as the spacecraft itself.
When you're "in atmosphere" that can be used for thrust, it's also going to be hypersonically dragging on the satellite body. I don't see any way this could work on the existing ISS - maybe something shaped like the SR-71...
🌻🌻 [google.com]
(Score: 2) by Rivenaleem on Wednesday March 07 2018, @02:46PM (9 children)
It's no different to propelling a boat through water. The satellite is 'buoyant' enough not to 'sink' so what it needs to do is propel itself through the medium it is floating on. Like a boat it will need to be shaped so that it doesn't have to work against itself, and isn't steered off course by a cross current.
(Score: 2) by JoeMerchant on Wednesday March 07 2018, @04:06PM (8 children)
You mean a U-boat? "Speedboats" get up on plane and propel themselves in the water while mostly passing the hull through air.
Satellites don't "float" on the atmosphere, it's a very diffuse boundary and in LEO they are inside it, although a very low density area.
This is a troll, right? The "cross current" in orbit is a 7+km/s headwind. A fast boat at 30 knots is doing 0.015km/s.
🌻🌻 [google.com]
(Score: 2) by Rivenaleem on Wednesday March 07 2018, @04:17PM (7 children)
It's almost as though it's hard to find a perfect analogy! If only there were cars that travelled under the road instead of on top of it.
(Score: 1) by DECbot on Wednesday March 07 2018, @04:41PM (5 children)
Imagine a car with a snorkel plowing through the bottom of a lake....
cats~$ sudo chown -R us /home/base
(Score: 2) by JoeMerchant on Wednesday March 07 2018, @05:01PM (4 children)
Well, air density at sea level is about 1225g/m3 while on-orbit around 200km up it's about 1/25 billionth as much at ~0.05ug/m3 [dtic.mil]. So, even though you are moving 500x as fast as the speedboat through air, and drag is a function of the square of velocity (does that hold in ultra-low densities?), that's still less than 1/100,000th the air-drag on a speedboat doing 30 knots.
🌻🌻 [google.com]
(Score: 2) by bob_super on Wednesday March 07 2018, @05:30PM (2 children)
The better analogy would be an air-breathing cannonball using a ramjet to expend reach, but without any control surfaces.
> drag is a function of the square of velocity (does that hold in ultra-low densities?)
That is a very good question, and I'm really curious what the answer could be. Obviously, moving the molecules out of the way is the same effect on the surface they bounce on, but the fact that they don't have neighbors preventing them from bouncing off has to account for some reduction. Does a spaceship traveling extremely fast in very-low density atmosphere create a spaceship-shaped tunnel that is temporarily a true void?
(Score: 2) by JoeMerchant on Wednesday March 07 2018, @06:09PM
If you're really curious, that paper I referenced above probably tell you in a roundabout fashion how they calculated drag... Seems like more attention span and time than I possess at the moment, especially compared to how curious I really am.
🌻🌻 [google.com]
(Score: 2) by JoeMerchant on Wednesday March 07 2018, @06:12PM
The thing that a spaceship has that your average pirate-era cannon ball doesn't is gyro control of orientation...
🌻🌻 [google.com]
(Score: 0) by Anonymous Coward on Wednesday March 07 2018, @05:38PM
At ultra-low densities, molecules don't interfere much with each other, so drag is simply determined by kinetic energy. It's that equation K=0.5mvv with vv being v squared.
At high densities, the fluid is viscous. Drag can be much higher.
(Score: 0) by Anonymous Coward on Wednesday March 07 2018, @07:01PM
Tremors 7!
(Yes, I checked, there's already a 6th in the works...)