[HN Gopher] Air-breathing electric propulsion for long-term orbi...
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Air-breathing electric propulsion for long-term orbital stability
(2021)
Author : rbanffy
Score : 85 points
Date : 2022-05-10 12:51 UTC (10 hours ago)
(HTM) web link (www.sciencedirect.com)
(TXT) w3m dump (www.sciencedirect.com)
| perihelions wrote:
| How much damage would air do to satellites at that altitude? The
| 2nd largest component is atomic oxygen, which doesn't sound
| friendly.
|
| edit: From fig. 3, compared against [0], the atomic oxygen
| density for this concept is 102-103 greater than at ISS' altitude
| (which considers it a hazard [1]). /edit: [2] has photos of ISS O
| damage
|
| [0]
| http://esmat.esa.int/publications/published_papers/corrosion... (
| _"...oxygen atoms have a density of 107 to 108 atoms /cm3 at
| International Space Station (ISS) altitude (around 400 km) with a
| thermal energy of approx. 0.1 eV"_)
|
| [1]
| https://ntrs.nasa.gov/api/citations/20010038448/downloads/20...
|
| [2]
| https://ntrs.nasa.gov/api/citations/20190025445/downloads/20... (
| _" Figure 3.--Atomic oxygen undercutting degradation of the P6
| Truss solar array wing blanket box cover on the ISS after only 1
| year of space exposure."_)
| tomrod wrote:
| I wonder if plastic components work for that use case?
| wongarsu wrote:
| With that low an orbit you need hundreds of satellites to get
| decent line-of-sight coverage of the earth. I'd expect most
| satellites that go there are "mass produced" for that reason
| alone and are happy with a lifetime that's about 10 times less
| than that of the ISS, and a safety factor that's much lower.
| ncmncm wrote:
| We might imagine ceramic passivation coatings to protect
| surfaces of extra-low-orbiting birds.
|
| The ability to collect enough energy to drive thrust from
| large, draggy solar panels seems like a limiting factor.
| Maybe they could double as wings? Keeping them oriented to
| minimize drag would interfere with their ability to collect
| energy. It might be the optimal geometry for such a bird
| would be a hollow cylinder with panels ranged all the way
| around the outer surface.
| sitkack wrote:
| Beam energy from a higher orbit, microwave or optical.
|
| They could also have highly eccentric orbits so that they
| are only low over the coverage area.
| mLuby wrote:
| I hope air-breathing ionic propulsion _takes off_ because even if
| it turns out to not be great for satellites it 'd be wonderful
| for (small) aircraft. Aircraft are very loud thanks to their
| engine and propellers/jets. Recent experiments showed its
| possible to fly with _no moving parts_ using ionic flow:
| https://www.youtube.com/watch?v=IorDYGI1uqc (9min) I for one
| would love to fly (on) such a quiet plane, like a glider. Compare
| muscle car rev to electric car silence.
|
| It also reminds me of the Bussard ramjet, which I thought is
| considered ineffective due to creating more drag than thrust.
| Maybe the environment makes a difference?
|
| I wonder if it'd be more effective to use antipodal ground
| transmitters to beam power up to the satellite, rather than the
| satellite using solar panels? Less concern about sCaRy high-power
| microwaves when aiming them from rather than at Earth, though it
| could still interfere with aircraft and unintended satellites in
| the cone of effect.
| mlindner wrote:
| The noise from engines isn't from their combustion or their
| moving parts. It's from the massive air flow they cause. Ionic
| engines aren't going to be much quieter for aircraft, assuming
| they're even possible to move that much air.
|
| Also air breathing ionic propulsion kind of depends on the
| external presence of ions, which requires space conditions, not
| normal atmospheric conditions.
| lazide wrote:
| Eh, _kinda_. While most noise from a jet engine at the ground
| comes from the shear forces from the fast moving compressed
| exhaust stream interacting with slow moving surrounding air,
| the engine itself isn't quiet.
|
| Even in situations where you don't get that exhaust stream,
| (such as helicopter turbines spinning up with the clutch
| out), they're _very loud_. Hearing protection required loud.
|
| And very little of a rotary planes noise is coming from
| airflow or from the prop directly, most of it is coming from
| the engine itself. At best at least half.
|
| Presumably an ionic drive couldn't create the pressure
| differential levels of a jet engine, or probably even a prop,
| so they'd have relative large, relatively slow moving masses
| of air to work. So noise should be a lot lower from that, and
| also from lack of a internal combustion or turbine engine
| screaming it's hardest.
| [deleted]
| RobertoG wrote:
| This company is trying to do that:
|
| https://www.kreiosspace.com/
| [deleted]
| rossjudson wrote:
| A lot of movie scripts will need rewrites.
|
| OMG our orbit is decaying and we're running out of fuel. We're
| gonna hit the atmosphere and....
|
| get more fuel. Yay!
| biomcgary wrote:
| This concept was already used in The Expanse. I forget which
| episode.
| spacemark wrote:
| Very interesting. I work in the industry and have not heard about
| this concept. It appears quite a bit of low-TRL work has been
| done by our friends in Europe and Japan. Appears possible in the
| near future, especially with market pressures due to the
| popularity and anticipated congestion of LEO.
|
| But holy cow, the thruster in their diagram appears to be 80% of
| the spacecraft volume. These aren't going to be small birds,
| requiring likely multiple kW to stay in orbit.
|
| Thanks for sharing.
| _Microft wrote:
| Here is another article that I remember having submitted once:
|
| https://www.esa.int/Enabling_Support/Space_Engineering_Techn...
|
| Edit: since this article mentions "SITAEL" and some authors of
| the paper submitted here seem to work for "SITAEL" as well, it
| might be talking about the same thing. I'll keep the comment
| here anyways.
| dr_orpheus wrote:
| Super cool, but yeah it does seem to require a lot of power,
| more so than some of the existing electric propulsion systems.
| The T/P of 23 mN/kW is worse than a lot of existing Hall Effect
| thrusters that get thrust in the range of 50-70 mN/kW. It would
| be significantly more efficient with an ISP of the air-
| breathing EP in the ~5000 s range. But with the huge volume
| (and I assume more mass than existing EP thrusters) its hard to
| see how overall this would end up being a more efficient system
| than other electric propulsion systems.
| bell-cot wrote:
| _Interesting_. Sounds like a satellite with such a propulsion
| system could orbit with a perigee down where it had "infinite
| delta-v on tap", but an apogee up where space debris was a real
| problem. Given such a platform capability, all sorts of ways to
| intercept & de-orbit space junk start looking viable - because
| the "shift orbit to intercept the next one" moves are more-or-
| less free.
| UncleSlacky wrote:
| I've thought for a long time that the so-called "Biefeld-Brown
| Effect" (aka corona wind, electrohydrodynamic propulsion, ion
| propulsion, plasma actuator etc.) could be used to keep
| satellites in orbit indefinitely and cheaply using the atmosphere
| as propellant. It also has the advantage that the lower you go,
| the denser the atmosphere and the better the thrust.
|
| https://en.wikipedia.org/wiki/Biefeld%E2%80%93Brown_effect
| https://en.wikipedia.org/wiki/Plasma_actuator
| marcosdumay wrote:
| > No matter how much funding has been invested and the number
| of various private claims of a high induced speed, the maximum,
| average speed induced by plasma actuators on an atmospheric
| pressure conviction, without any assistant of mechanical
| amplifier (chamber, cavity etc.), is still less than 10 m/s.
|
| From your wikipedia link. That's a large problem for a rocket.
| mrfusion wrote:
| Can anyone eli5?
| NortySpock wrote:
| There is a small amount of air drag in low earth orbit, caused
| by the very thin gas atmosphere. The solar wind from the sun
| strips off and ionizes some of this gas. Ions are atoms or
| molecules with an unbalanced positive or negative charge -
| contrast that with neutral atoms or molecules without an
| electric charge.
|
| Ions can be accelerated via an electromagnetic field. You can
| use this as thrust for your spaceship. The faster the exit
| velocity of the gas, the more efficient your acceleration. (the
| technical term is Isp or impulse-seconds or something).
| Normally spacecraft carry their own neutral fuel, ionize it,
| and then spit it out the back end. This requires a lot of
| electrical energy but if you get that from big solar panels
| this tends to be more efficient than chemical energy rockets.
| More efficient => less mass=> smaller, cheaper spacecraft and
| rockets.
|
| The paper estimates that in very low earth orbit (190km
| altitude -- for reference the International Space Station is at
| 400km altitude), there is enough density of ionized gas, that
| you could suck in ionized gas, accelerate it out the back with
| ion thrusters, and basically break even or better. This means,
| at that altitude, with a very specific design, you could use
| the atmosphere as propellant rather than bringing your own in a
| bottle. In theory, not needing a fuel supply means you're not
| fuel limited on satellite lifetime, and fuel supply is normally
| the big constraint that ends a satellite mission.("We're out of
| gas for pointing and moving the spacecraft")
|
| Takeaway: might be useful for Starlink / Project Kuiper /
| imaging systems in 5-10 years... Might be useful around other
| planets with plentiful solar power but it's a very niche
| solution only usable at this one altitude band currently.
|
| See also: Hall Effect Thruster, Electrostatic Grid Thruster.
|
| Contrast with: fusion powered Bussard Ramjet.
| Anunayj wrote:
| Satellites in low earth orbit (think Starklink, ISS) orbit
| around like 300-600 km height. At this height the the
| atmosphere is pretty thin but not negligible and these
| satellites slow down over time due to drag. For this reason
| they often have to have a method of propulsion for "station
| keeping" [1].
|
| Now propulsion in space is somewhat different to how we do on
| Earth (in airplanes). To propel yourself forward, since
| momentum is always conserved, you need to have something (with
| momentum) and throw it backward (which requires energy), so you
| are propelled forward. On Earth Jet engines suck air in,
| combine it with fuel and throw it all backward to propel
| themselves forward. A propeller just throws the air backward to
| boost itself forward, however in space you can't do that, cause
| there is nothing to suck in. Which means you need to carry that
| mass with you.
|
| There are some very efficient designs (like Ion thrusters [2])
| that propel ions of gases to very high speeds (using electric
| energy obtained from solar panels) to achieve very efficient
| propulsion.
|
| This LEO satellites are not exactly in a perfect vaccuum, what
| this paper suggests is the viability of a method where a engine
| sucks air in the thin atmosphere, and uses a (very efficient)
| engine to propel it backward that it is able to compensate for
| the drag forces the satellite would endure.
|
| 1. https://en.wikipedia.org/wiki/Orbital_station-keeping 2.
| https://en.wikipedia.org/wiki/Ion_thruster
| Anunayj wrote:
| Oh and I forgot to mention, notice how I say we need to throw
| something with "momentum" and not "mass", this is because
| think of photons, they don't have a rest mass, but they have
| momentum! and all you need to makes photons is energy
| (Afterall LEDs do it with efficiently). Infact light sails
| [1] use this momentum to propel themselves forward! Afterall
| the solar system is full of photons thanks to the sun. The
| downside is... they are very very slow.
|
| There are also concepts of making a "Photon Rocket" [2] as a
| viable means of interstellar travel.
|
| [1]. https://en.wikipedia.org/wiki/Solar_sail [2].
| https://en.wikipedia.org/wiki/Photon_rocket [2].
| EthanHeilman wrote:
| The thing that makes it hard to go fast is not the energy
| needed but the mass you need to toss out the back. This is
| because you need to carry the mass you throw out the back. It
| adds to your total mass and slows you down. In space generally
| you carry all that toss out the back mass and once you use it,
| you can't get more. You can get more energy by using solar
| panels. Going the speed of light would require very little
| energy if you could just convert that energy directly into
| forward direction.
|
| Solution: If you are close enough to Earth that you experience
| drag from the atmosphere, use the atmosphere as the mass you
| toss. Now you have a really efficient long term way of going
| fast because you can always get more mass to toss from the
| atmosphere and you can always get more energy from solar
| panels. You no longer need to bring mass to toss to orbit and
| you never run out of mass to toss.
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(page generated 2022-05-10 23:01 UTC)