back to article New study demonstrates iodine as satellite propellant... in space

Scientists are trying to support the boom in miniaturised satellites with the development of a plasma engine using an iodine propellant — rather than the commonly used xenon — for the first time. Launched last November by Chinese space biz Spacety, the propulsion systems developed by French company ThrustMe are meant to offer …

  1. Pascal Monett Silver badge

    On the one hand : Science !

    On the other hand : another excuse to put thousands more satellites into an already crowded orbital junkyard.

    My heart is torn.

    1. MiguelC Silver badge
      Coat

      Re: On the one hand : Science !

      Fine science, it seems, but calling the company "TrustMe"? Really?

      1. Paul Crawford Silver badge

        Re: On the one hand : Science !

        Why not ThrustMe?

        Far more appropriate for an engine. Or doing the time-warp dance...

        1. Sleep deprived
          Happy

          Re: On the one hand : Science !

          Why not ThrustMe?

          Because the French have a problem with pronouncing the th, which comes out as z (ze satellite...)

          1. Anonymous Coward
            Anonymous Coward

            Re: On the one hand : Science !

            "Why not ThrustMe?

            "Because the French have a problem with pronouncing the th, which comes out as z (ze satellite...)"

            the 'th' sound in 'the' is different to that in 'thrust'. There are at least two different 'th' sounds in English and there's an example to illustrate the difference 'the theatre'. So the example isn't a good choice.

            See https://en.wikipedia.org/wiki/Pronunciation_of_English_%E2%9F%A8th%E2%9F%A9

            I have no idea of what problems the French have pronouncing any of them, although wikipedia does mention some.

            1. Anonymous Coward
              Boffin

              Re: On the one hand : Science !

              The two pronunciations of 'th' are the voiced ('than') and unvoiced ('thing') dental fricative. Both are quite rare in European languages and think in languages generally, this is why non-native English speakers often find them hard. Interesting is that they did not occur in ancient Greek, but they do in modern Greek. Both occur in Spanish. Neither occurs in my native language (in either of them in fact).

      2. DS999 Silver badge

        That got me too

        A company called "TrustMe" makes me start thinking of reasons why I shouldn't trust them. It is like if you see a listing of a house for sale and it says "not haunted" and you immediately wonder how haunted it is.

      3. Rustbucket

        Re: On the one hand : Science !

        The name of the company is actually Thrustme, although that makes me think more of a porn channel.

        https://www.thrustme.fr/

    2. Peter Gathercole Silver badge

      Re: On the one hand : Science !

      Maybe this technology can be used to provide the end-of-life de-orbit maneuver.

    3. The Axe

      Re: On the one hand : Science !

      Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.

      1. Brewster's Angle Grinder Silver badge

        Re: On the one hand : Science !

        Space might be big. But we're talking about a thin shell around the earth inhabited by rapidly orbiting objects intersecting long exposure windows.

      2. Snowy Silver badge
        Coat

        Re: On the one hand : Science !

        Space may be big but space in orbit vs the problems of a collision and suddenly that space starts to look uncomfortable small.

  2. Andy Non
    Coat

    Maybe mix the iodine

    with Ammonia first. That would give it a bit more "kick". ;-)

    I'll get my lab coat, mine's the one with hole blown in the pocket and label saying "mad scientist".

    1. Chris G Silver badge

      Re: Maybe mix the iodine

      The ammonia helps it to make pretty purple smoke but is that good as reaction mass?

      1. Andy Non

        Re: Maybe mix the iodine

        It made my chem lecturer "react" when he stepped on a bit and it exploded sending more fragments of it around the lab floor, followed by more cracks and bangs as others subsequently walked around.

    2. DoctorPaul

      Re: Maybe mix the iodine

      Oh that reminds me of some "unofficial" bits of chemistry at school back in the 60's :-)

      I seem to recall that potassium permanganate and conc sulphuric acid provided interesting results - covered the entire chemistry lab in a layer of fine black fluff some ten minutes before the class was due to start.

      Which in turn reminds me fondly of the grinding mill for gunpowder that my friend and I made out of Meccano, an Andrews tin and some marbles. Sealed (small) jar of the powder was ignited electronically using a model railway transformer, two wires and a sliver of tin foil - I sometimes wonder how I survived my childhood!

      1. Anonymous Coward
        Anonymous Coward

        Re: Maybe mix the iodine

        "I seem to recall that potassium permanganate and conc sulphuric acid provided interesting results - covered the entire chemistry lab in a layer of fine black fluff some ten minutes before the class was due to start."

        Our chemistry teacher was also the deputy head, so he used to think big. When he wanted to demonstrate the reaction of sugar and conc sulphuric, he took a bag of the stuff from the lab steward's tea-making kit and tipped a whole bottle of acid on it. Luckily? he did it in a large crystallising dish and there was a fume cupboard nearby to dump it into.

      2. John Brown (no body) Silver badge

        Re: Maybe mix the iodine

        "I sometimes wonder how I survived my childhood!"

        Do that today and you'd probably end up in jail as a terrorist!

  3. DarkwavePunk

    Uh

    Don't mess with halogens. Put some dioxygen difluoride into the mix to spice things up - that'll get you bang for your buck.

    1. O RLY

      Re: Uh

      For a fun read about FOOF, here's Derek Lowe, PhD, discussing why he will never work with it.

      https://www.science.org/content/blog-post/things-i-won-t-work-dioxygen-difluoride

      https://www.science.org/content/blog-post/things-i-won-t-work-dioxygen-difluoride

      1. Ribfeast

        Re: Uh

        This stuff is nasty too:

        https://en.wikipedia.org/wiki/Chlorine_trifluoride

    2. Swarthy Silver badge
      Boffin

      Re: Uh

      I have said before (and will probably say again - knowing this crowd) If FOOF is the answer, you are asking the wrong question.

  4. Spoobistle
    Joke

    little was known about its fundamental properties

    I do hope we're not going to discover that dusting iodine over the upper atmosphere might be a bad move. Still, it might help sterilize any "plagues from spaaace" a la Hoyle & Wickramasinghe!

    1. Mike 137 Silver badge

      Re: little was known about its fundamental properties

      "I do hope we're not going to discover that dusting iodine over the upper atmosphere might be a bad move"

      I suspect we will. Halogens are highly active chemically. However it may not become apparent for some time, making it harder to reverse.

    2. adam 40 Silver badge

      Re: little was known about its fundamental properties

      What about when it condenses onto other spacecraft (if used in orbit)?

      1. Yet Another Anonymous coward Silver badge

        Re: little was known about its fundamental properties

        Space is big. Really big. You just won't believe how vastly, hugely, mindbogglingly big it is.

        The number of Iodine atoms/m^3 this adds ......

    3. Chris G Silver badge

      Re: little was known about its fundamental properties

      Iodine is thought to be bad for the recovery of the ozone layer but considering it will be used in microscopic amounts in orbits somewhat higher than the ozone layer, it is unlikely to have any significant effect. hopefully.

      https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjSydT4taL0AhUi5uAKHYk3C8EQFnoECAcQAw&url=https%3A%2F%2Fwww.sciencedaily.com%2Freleases%2F2020%2F01%2F200113153310.htm&usg=AOvVaw2KcMF5uvbZk_MQxMG6EFED

  5. tony72

    Nice

    From a quick Google, it seems like iodine is about $80/kg, while Krypton is only $3 (and Xenon is $850). But I guess if the storage system is much simplified (i.e. lighter) with iodine, that's probably much more significant than the cost of the stuff itself. I guess we'll know soon enough; if there's a significant cost saving, certain companies putting thousands of satellites into orbit are surely going to take note.

    1. Gene Cash Silver badge

      Re: Nice

      Rockets are 100% engineering tradeoffs. For example, liquid hydrogen has more bang than RP-1 (a refined kerosene) but the tanks are huge and need cryo insulation... so first stages use RP-1 because the rocket overall ends up a lot lighter and smaller, and that's important in a first stage.

      It's not a cost saving. It's a space & weight saving. Cubesats have a hard size and mass budget. If you exceed it, you're not a cubesat any more, and you don't fit into the standard launcher or the ride-share.

      1. Yet Another Anonymous coward Silver badge

        Re: Nice

        Wouldn't you just pick the heaviest material that is a liquid at room temperature and easily vaporized?

        Something silvery and quick ?

        1. ClockworkOwl

          Re: Nice

          Not sure, but I bet it's latent heat.

          Mercury takes 5 times as much energy to vapourise as Xenon, and none of that will provide propulsion...

        2. Paul Crawford Silver badge

          Re: Nice

          That sort of thought has been considered before. I suggest a read of:

          https://library.sciencemadness.org/library/books/ignition.pdf

          He covers how at one point dimethyl mercury was considered, that is something you really don't want to deal with. Not ever. Really, not EVER. A world leading specialist in the toxic nature of heavy metals was killed by what seems like a trivial accident:

          https://en.wikipedia.org/wiki/Karen_Wetterhahn

          1. Jan 0

            Re: Nice - Karen Wetterhahn

            Yikes! It makes me wonder how I ever survived making and detonating substantial quantities of fulminate of mercury, many decades ago.

    2. Dante Alighieri Bronze badge
      Coat

      costings

      there is a Wikipedia page on this topic.

      Data is older but indicated Iodine ~$30-35 and borne out by current googling, and a cost for Krypton of ~$290/kg at the same time frame which looks more realistic to me. YMMV

      So cost saving on propellant and likely big reduction in thruster weight/volume. Win/Win

      All we need now is one with a charged field to ingest orbital debris and a scheme to atomise it for thrust; mk2 tracks down debris to ingest and declutters LEO

      Mines the one with the psychoactive substance -->

      1. Fruit and Nutcase Silver badge
        Alert

        Re: costings

        Mentos + Cola is cheaper. Come up with a way to modulate that...

      2. John Brown (no body) Silver badge

        Re: costings

        "All we need now is one with a charged field to ingest orbital debris and a scheme to atomise it for thrust; mk2 tracks down debris to ingest and declutters LEO"

        Just don't give it any current AI and leave it to it's own devices. It might start eating stuff it shouldn't.

    3. John Brown (no body) Silver badge

      Re: Nice

      I would imagine it's also the cost of containing the gases at very high pressure as opposed to the a solid, transporting it to the satellite and "fuelling" it on the launch site. The raw material cost is probably largely irrelevant. Likewise, they are targetting very small sats and the article says the current gas based ion engines don't scale down small enough.

    4. Bill Gray

      Consider 'total cost of ownership'

      These are low-thrust devices, only used once an object is in (at least) low-earth orbit. You have the cost of the propellant, _and_ its storage tank (significant for xenon), _and_ the cost to get it to LEO in the first place. See slide 9 of the link below; looks as if at best, it'll run you over $1000/kg for that bit.

      https://ntrs.nasa.gov/api/citations/20170012517/downloads/20170012517.pdf

      So ignoring the storage issues, but adding cost-to-LEO in, you're looking at $1080/kg for iodine; krypton, $1003/kg; xenon, $1850/kg. Also to be considered is exhaust velocity; if one propellant can be expelled at ten times the velocity of another, thereby generating ten times as much thrust per kilogram, that'll slant things in yet another direction.... I know xenon has an exhaust velocity of around 40 km/s; dunno about the others. If they're significantly slower, it'd go a long way to explain why xenon gets the use it does.

  6. lglethal Silver badge
    Trollface

    Supporting a boom in the small satellite market

    I'm not sure if the customers will be that happy if they're satellites go boom due to this thruster.

    Things going Boom on a satellite are generally considered very bad indeed. We're all looking at you Russia! *shakes head in disgust *

    1. Mark 85 Silver badge

      Re: Supporting a boom in the small satellite market

      We're all looking at you Russia! *shakes head in disgust *

      Better add the US and China to that disgust. They've blown satellites up intentionally also.

      1. The Axe

        Re: Supporting a boom in the small satellite market

        And India

      2. Bill Gray

        Re: Supporting a boom in the small satellite market

        Yes and no. The US test was on an object already at low altitude. As a result, most of the bits decayed rapidly, with the last bit coming down 20 months later.

        https://en.wikipedia.org/wiki/Operation_Burnt_Frost

        You can argue against ASAT tests on a variety of grounds. But if you're going to do them, for $(DEITY)'s sake, do it on an object at low altitude where it won't cause much trouble. Such objects are numerous. There is absolutely no good reason to blow up something at the altitudes of the Russian, Chinese, and Indian tests.

  7. adam 40 Silver badge

    Needs more thrust

    I'm surprised about the single voltage gradient in the thruster.

    Surely a more efficient method would be a linear accelerator, or even a cyclotron, so accelerate the ions to near light velocities?

    Then you can cut down on your propellant for a given impulse.

    1. Yet Another Anonymous coward Silver badge

      Re: Needs more thrust

      Easier to add extra propellant mass than engineering to increase the velocity - unless you have a very long voyage planned where the amount of the stuff you chuck overboard matters.

      Efficiency is just electrical power in vs kinetic energy out - more complex systems to create higher velocities would generally be less efficient.

  8. cray74

    Density!

    Iodine's not just space storable, but a room temperature solid that will vaporize easily (184C). Compared liquid and gas containers that have to deal with the stresses of pressurization, an iodine tank could be very light. Just boil a bit off at near-vacuum pressure for the low demand of an ion engine.

    And the density! 4.93g/cc is about four times denser than any common liquid or solid propellant, to say nothing of a gas like xenon. The propellant tank would be so light for the delta-V you could cram in it.

    Finally, iodine ionizes at a lower energy than xenon, so it's got that advantage.

    Cool stuff.

    1. Yet Another Anonymous coward Silver badge

      Re: Density!

      and if you graze your knee you can dab some on ....

  9. TheRealRoland
    Coat

    Tim nice-but-dim's comments:

    >Tech promises to support boom in small satellites

    "Sounded more like a thud to me"

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