
First firing of air-breathing electric thruster - sohkamyung
http://www.esa.int/Our_Activities/Space_Engineering_Technology/World-first_firing_of_air-breathing_electric_thruster
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karkisuni
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.

~~~
binarycoffee
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.

~~~
ckastner
> 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](https://en.wikipedia.org/wiki/Tau_Zero)

[2]
[https://en.wikipedia.org/wiki/Bussard_ramjet](https://en.wikipedia.org/wiki/Bussard_ramjet)

~~~
gaius
How can you decelerate with a ramjet? Wouldn't your own exhaust push the
matter you needed out of the way?

~~~
whatshisface
You could push the exhaust single-file in a highly focused beam, leaving most
of the solid angle around you unpushed.

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walrus01
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.

~~~
mrestko
[https://en.wikipedia.org/wiki/Gravity_Field_and_Steady-
State...](https://en.wikipedia.org/wiki/Gravity_Field_and_Steady-
State_Ocean_Circulation_Explorer)

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kerkeslager
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.

~~~
vanderZwan
It works by ionizing the air, so that might lead to issues with producing
ozone.

~~~
telchar
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.

~~~
vanderZwan
Yeah, I should have clarified: I was responding to the _" having a lot of
applications"_ remark, which to me implied other places than low earth orbit.

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mhandley
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.

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Davetron
Is no-one going to comment on how beautifully sci-fi that engine looks when
running?

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rdtsc
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.

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yoz-y
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](https://en.wikipedia.org/wiki/Magnetohydrodynamic_drive)

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gwbas1c
It's a giant ionic breeze!

~~~
cjsawyer
There are less accurate ways to explain it.

~~~
schwarrrtz
It’s an elephant!

~~~
IIAOPSW
There are more accurate ways to explain it.

~~~
lordelph
It's an elephant on a skateboard in the rain - the elephant sucks up some
falling water, and then shoots it horizontally from its trunk to scoot
gracefully across the savannah.

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black_puppydog
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

~~~
JumpCrisscross
_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](https://en.m.wikipedia.org/wiki/Bussard_ramjet)

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stcredzero
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.

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jmadsen
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 :-)

~~~
kartikkumar
Astranis is launching satellites to GEO [1], i.e., not low.

[1] [https://techcrunch.com/2018/03/01/astranis-emerges-from-
stea...](https://techcrunch.com/2018/03/01/astranis-emerges-from-stealth-with-
a-new-satellite-technology-for-connecting-the-world/)

~~~
jmadsen
You're right. The article I read was more business oriented and used both
terms, and I didn't notice.

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ccozan
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...](https://news.engin.umich.edu/2017/10/thruster-for-mars-mission-
breaks-records/)

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UncleSlacky
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](https://en.wikipedia.org/wiki/Biefeld%E2%80%93Brown_effect)

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dmurthy
First thought was, what other industries and applications could this
potentially serve?

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Robotbeat
Except it's not the first:
[http://www.busek.com/technologies__hall.htm](http://www.busek.com/technologies__hall.htm)

~~~
binarycoffee
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/...](http://erps.spacegrant.org/uploads/images/2015Presentations/IEPC-2015-271_ISTS-2015-b-271.pdf)

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mrfusion
How much thrust does this produce?

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holtalanm
forgive my ignorance, but....could this be applied to aircraft? Make a near
fuel-less jet?

~~~
andygates
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.

~~~
godelski
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.

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cletusw
Spelling error in title. Should be ... Electric Thruster

~~~
HankB99
I thrust it will be fixed.

~~~
sohkamyung
Whoops! Yes, I fixed it. Thanks for noticing. :-)

~~~
inamberclad
And here I spend a good minute staring at the title, looking for the (now
gone) spelling error.

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cduguet
So, just to be clear (because I don't see it mentioned anywhere). Are we
taking about the EMDrive here?

~~~
martythemaniak
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.

~~~
flukus
So "air collecting" or "mass collecting" would be more accurate since it
doesn't really breath like a typical air breathing engine?

~~~
andrewwharton
It doesn't accelerate the air like a typical air breathing engine, but it
certainly ingests the air like one. It's basically a ramjet but uses electric
charge to accelerate the exhaust gas rather than hydrocarbons.

