ESA successfully tests an air-breathing ion thruster


Please consider donating to Behind the Black, by giving either a one-time contribution or a regular subscription, as outlined in the tip jar to the right or below. Your support will allow me to continue covering science and culture as I have for the past twenty years, independent and free from any outside influence.

Engineers from the European Space Agency (ESA) and an Italian company have successfully tested a prototype of an ion engine that would obtain its fuel from the thin atmosphere available in low Earth orbit, thus allowing it to operate practically indefinitely.

From the press release:

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.

Think about it. You supply your planetary probe one or more of these engines, and once it reaches orbit around its target it has an unlimited fuel supply to do research just about forever. More important, such technology when further refined is going to enhance human exploration as well. For example, rather than use the atmosphere at it arrives, later designs could simply dive into the atmosphere to get the spaceship’s tank refilled. Such engines would make spacecraft free from the tether of Earth.

Share

14 comments

  • fred K

    Not sure there’s a net benefit of this, unless you really need to be at very low altitudes. Part of SpaceX’s starlink constellation plans to fly low enough to need ion thrusters … they may benefit from this.

    It’s a lot simpler to fly another 50 KM higher and do your mission from there.

    I’m fairly certain that it doesn’t make sense to drop into a gravity well, grab some atmosphere, and then accelerate out to a different gravity well.

  • fred K wrote, “I’m fairly certain that it doesn’t make sense to drop into a gravity well, grab some atmosphere, and then accelerate out to a different gravity well.”

    No offense intended, but your certainty here reminds me a lot of what managers and engineers would tell me for decades about how reusing rocket stages was impractical, no, impossible! Moreover, you could never land them vertically, and even if you could, it would use up so much fuel it would make it impossible to get any satellites into orbit.

    Anyway, I am thinking of a future where spacecraft are not designed for one-time use, but are vehicles like cars and trucks. They will have engines that their owners will need to get refueled. If we develop ion engines that can run on a wide range of gases and can be refueled simply by dipping into an atmosphere on one orbit, I see no reason why this won’t happen, especially because of the ability of ion engines to maneuver with greater flexibility.

  • Edward

    I’m fairly certain that it doesn’t make sense to drop into a gravity well, grab some atmosphere, and then accelerate out to a different gravity well.

    Think of all the propellant that would not have to be taken into orbit. Who needs to fuel up or refuel with lunar-water propellant when the Earth’s atmosphere can provide enough propellant to get to Mars, or wherever. At Mars, just dip into its atmosphere to get enough to come back to Earth. The same for all the other planets and moons that have atmospheres.

    The next Saturn probe may be able to collect enough propellant from Saturn in order to spend decades closely examining the various moons close up and to explore the rings’ particles close up, too. Just dip into Saturn’s atmosphere again, and you have enough for yet another moon’s exploration. This kind of mission is what someone commenting on this site, a few months ago, was hoping for on the next Saturn probe, and now it may become possible.

    A problem to overcome is the limited life on our current ion engines, and now there is even more incentive to extend that lifetime.

  • pzatchok

    How about with asteroid collection?

    Just land a few of these engines on the asteroid and then just harvest gasses from the asteroid.

    The hard part would keeing them powered.

  • BSJ

    Sounds kinda perpetual motion-ey to me.

    Can you really produce more thrust than you loose from drag?

  • J Fincannon

    This concept has been investigated for a while for use by satellites.

    What I really like is the great benefit for long duration aircraft at very high altitudes.
    https://patents.google.com/patent/US6834492

  • Localfluff

    I had no idea they made this advanced tests already, great news! This might be combined with aerobraking. The ExoMars Trace Gas orbiter has spent over a year aerobraking itself into science orbit. If it could’ve refueled an ion engine at each dip, that might’ve assisted.

  • Max

    The concept is sound, the question will be is the thrust greater than the drag? Can the craft store air? Will it be on a elliptical orbit to only scoop air when the craft has collected enough electrical energy (when batteries are full) and when it is not in the shadow of the earth where sunlight can provide heat and aid in the efficiency of the ion thrust?
    The picture shows the satellite has its Solar panels built into its body to reduce drag. The scoop that collects the air is larger than the body of the craft. The atmosphere shrinks when the sun goes down which reduces the drag in earths shadow, which is good because solar panels cannot produce power in earths shadow.
    The temperature of the craft drops to 300° below zero so it is unlikely to operate at that time due to inefficiencies. On the other hand, it could be put into a polar orbit that keeps it in the sunlight at all times. There is not much air over the poles, but the atmosphere bulges outward near the equator and is probably where the ion engine will be activated.

    The concept reminds me of sci-fi books I’ve read in the distant past. Like the concept of a colony ship (without FTL Technology) built into an astroid/ice covered comet where the mass drive engines would convert the mass of the astroid into thrust. It would take many generations, thousands of years, to arrive at their destination. The ship would be much smaller than when they started.
    Another concept involved a well established lunar colony and orbital space station that was cut off from earth due to nuclear war. Destroyed communication and support system as well as non-existent defense systems forced them to struggle for survival.(governments are gone, the colonist are completely forgotten)
    They created a fleet of scoop ships that would leave lunar orbit and dive through earths atmosphere at such speeds that’s the scoop would compress the air into their tanks with enough momentum left to reenter the moons gravity field.
    Moving too slow, the ships lunar orbit would be close to the surface allowing the lunar colony to shoot empty tanks with relief supplies and Crew by electrical railgun method. Once the tanks were full, they would be offloaded, to save fuel, into a magnetic net capture system.
    Then the scoop ship would use its ion engine in the slow process of climbing out of the lunar gravity well for another trip to earth.
    A larger craft with detachable living quarters, would be sent to Venus to scoop carbon dioxide because carbon became the most precious element. (Every human born act as a carbon sink that limited the carbon needed to grow food)
    On the return trip, they would refine/separate the carbon to store and use the oxygen, with hydrogen that was scooped from space, to make enough thrust and reduce their mass to return to the moon.
    I dig this stuff.

  • jburn

    I wonder how this type of fuel sourcing would impact prospects for giant airships.

    http://www.blimpinfo.com/airships/can-giant-airships-accelerate-to-orbit-jp-aerospaces-idea/

  • J Fincannon

    “I wonder how this type of fuel sourcing would impact prospects for giant airships.”

    I think it would definitely help that they did not have to carry their propellant to orbit with them. However, due to the large size of JP Aerospace airships to orbit and their drag profile (unless they invent some sort of drag elimination technology), even air breathing EP is not going to get them to orbit. But maybe if they changed to a thin wedge shaped airship….

  • J Fincannon

    “The concept is sound, the question will be is the thrust greater than the drag? ”

    With enough electricity and a high enough Isp, it should be, but we need more details.

    “Can the craft store air?”

    It does not look like it. It uses an inlet to compress the air and then ionize it and eject it.

    “Will it be on a elliptical orbit to only scoop air when the craft has collected enough electrical energy (when batteries are full) and when it is not in the shadow of the earth where sunlight can provide heat and aid in the efficiency of the ion thrust?”

    The GOCE satellite they mentioned is a polar, sun synchronous, 250 km orbit which looks similar to the one they propose. Even GOCE had eclipses though. EP does not practically work on batteries or in shadow. Only in Sun.

    “A review of research in low earth orbit propellant collection”, 2015 is a good report to examine.

    “The atmosphere shrinks when the sun goes down which reduces the drag in earths shadow, which is good because solar panels cannot produce power in earths shadow.”

    Not that much. Maybe you are thinking of the radiation belt. During a solar cycle, the atmosphere goes up and down over many months, but not in hours.

    “The temperature of the craft drops to 300° below zero so it is unlikely to operate at that time due to inefficiencies. ”

    Not sure what you mean. Satellites operate in eclipse. Even geosynchronous ones. It sure doesn’t help to not have sunlight though. EP likes operating in the Sun because of the power availability.

    “On the other hand, it could be put into a polar orbit that keeps it in the sunlight at all times. ”

    Precisely.

    “There is not much air over the poles, but the atmosphere bulges outward near the equator and is probably where the ion engine will be activated.”

    I don’t think so. Again, perhaps you are thinking the radiation belt. The atmosphere is held in place by gravity (pushed around by the Sun’s radiation, solar wind, etc) and the gravity at the poles are nearly the same as at the equator.

  • Edward

    BSJ asked: “Sounds kinda perpetual motion-ey to me. Can you really produce more thrust than you loose from drag?

    Yes. Solar arrays or nuclear power plant can be used to provide the energy that accelerates the molecules and atoms collected, providing more thrust than drag. During collection period, the thrust need only match the drag.

    Max asked: “Can the craft store air?

    This would have to be another invention. The ion engine tested here was only a conceptual test of the engine and the collection. The collected gasses were used immediately. Storage would be a different innovation, but a useful one.

    The temperature of the craft drops to 300° below zero so it is unlikely to operate at that time due to inefficiencies.

    Satellites tend to have “keep alive” heaters on board in order to ensure critical items remain warm enough, perhaps while in shadow; “warm enough” can be pretty cold, though. If the pass through the shadow is short enough, then the heat dissipation would not be so fast that the heaters have to turn on. Batteries would be needed for operation in shadow, and some spacecraft do not have much battery storage; the savings of this weight and reduction of this complication is one of the advantages of a sun-synchronous orbit.

  • Max

    I mentioned,
    “There is not much air over the poles, but the atmosphere bulges outward near the equator and is probably where the ion engine will be activated.”

    J Fincannon Said,
    “I don’t think so. Again, perhaps you are thinking the radiation belt. The atmosphere is held in place by gravity (pushed around by the Sun’s radiation, solar wind, etc) and the gravity at the poles are nearly the same as at the equator.”

    Thank you, I am impressed with the knowledge and information of the readers of this site.
    I looked up the atmosphere and this is what it says,

    Troposphere:
    “The troposphere can be found between the ground and an altitude of 7 to 20 kilometers (4 to 12 miles). The lesser thickness is found at the polar regions, since colder temperatures lead to a decrease in gas volume.”

    The poles only have 4 miles of atmosphere resulting in lower than normal air pressure.(which is why it’s so cold there even with 24 hour sunlight for nearly 3 months) Air pressure friction is what causes heat. (Which is also the causation of 90% of the global warming.)
    Equator has 14 miles of atmosphere, with the highest barometric pressure, the most friction, mildest weather on the planet, day or night.

    Stratosphere
    The stratosphere can be found between average altitudes of 20 and 50 kilometers (12 and 31 miles). The lower altitude of the stratosphere changes seasonally and varies between 8 and 16 kilometers (5 and 10 miles). The thickness of the stratosphere also varies with latitude. In both cases, colder regions and seasons lead to a thinner stratosphere, due to gas compression.

    I may be reading this incorrectly, but it appears the atmosphere over the poles are much thinner then at the equator. If I had to guess why, It could be that there is more gravity on the poles squeezing the atmosphere to the sides in combination with the centripetal force of the earth spinning.

    The ion engine cannot store air. Can it capture and reuse the air or Xeon? I’m thinking thrust would still work in a closed system. Magnetic field could reroute the protons back through the intake. I don’t know if it should go through a catalyst first.
    The idea came from trying to apply a different concept of recapturing the exhaust of hydrogen oxygen rockets in deep space. The exhaust is water which if is captured can be reprocessed back into fuel again. Can you just imagine a rubber or solar blanket balloon that must be miles in diameter filling with water vapor which forms ice crystals… It would be real difficult to collect those crystals in freefall. That is one advantage for an ion thruster on a planetoid. The exhaust gases would be captured by the gravity and refrozen on the surface to be gathered and recycled indefinitely.

    The hydrogen dirigible is a interesting idea. I’ve heard of similar concepts in popular mechanics using the skin of the craft like a particle Excelerator. I believe the dirigible was hollow like a donut, air forced through the middle would be ionized causing air to flow around the craft because of the magnetic field. So the air that would normally drag it slower, would be used to drive it faster.

  • J Fincannon

    Max said:

    “..but it appears the atmosphere over the poles are much thinner then at the equator. If I had to guess why, It could be that there is more gravity on the poles squeezing the atmosphere to the sides in combination with the centripetal force of the earth spinning.”

    You raise a good point about the centrifugal force and temperature. So, I ran a model to check the atmospheric density:
    https://ccmc.gsfc.nasa.gov/cgi-bin/modelweb/models/vitmo_model.cgi
    I ran it for 0 latitude and 90 deg latitude and compared the mass density of the atmosphere as a function of altitude from 0 to 150 km. When I plot the data they look pretty close even with the data plotted on a log scale. But if I do a percentage difference between the two, you see an interesting difference. Below 8 km and above 115 km, the atmospheric density for 90 degrees latitude is more than at 0 degrees latitude. But between 8 km and 115 km the polar atmospheric density is as much as 46% different. The greatest difference is at 62 km with a atmospheric density of 1.35e-7 gram/cm^3 for the 90 deg latitude value and 2.5e-7 gram/cm^3 for the 0 deg latitude case.

    So, your statement, “There is not much air over the poles,..” can be quantified by integrating the density over the altitude profile. Using this data source, there is 2.6% MORE atmosphere at the poles! It may seem odd, but since most of the atmosphere is at lower altitudes (it has higher pressure and is more dense), since the density is greater at 90 deg latitude than 0 deg latitude at The ion engine cannot store air. Can it capture and reuse the air or Xeon? I’m thinking thrust would still work in a closed system. Magnetic field could reroute the protons back through the intake. I don’t know if it should go through a catalyst first.

    This engine does not appear to store air, but it could if necessary. I think they seem to want to fly a circular orbit thus would get a constant feed of air molecules so no air needs to be stored.

    You can’t really get accelerated air or Xenon back. This is “reaction mass” and shoots out at high speeds to the great beyond. It would be a perpetual motion machine if you caught the ions and reused them.

    >The idea came from trying to apply a different concept of recapturing the exhaust of hydrogen oxygen rockets in deep space. The exhaust is water which if is captured can be reprocessed back into fuel again. Can you just imagine a rubber or solar blanket balloon that must be miles in diameter filling with water vapor which forms ice crystals… It would be real difficult to collect those crystals in freefall. That is one advantage for an ion thruster on a planetoid. The exhaust gases would be captured by the gravity and refrozen on the surface to be gathered and recycled indefinitely.

    Yeah, I don’t think you can capture reaction mass that is heading out at high velocity. It like putting an airplane inside a balloon. Its not going anywhere but it will blow alot of air around the balloon.

Leave a Reply

Your email address will not be published. Required fields are marked *