back to article Budget satellite drag sail shows space junk how to gracefully exit orbit

A prototype satellite built to test a deployable drag sail to de-orbit satellites appears to have fulfilled its purpose, burning up on re-entry earlier this month after spending just 445 days in orbit. SBUDNIC, an acronym chosen to be a play on "Sputnik," was put together by students at Brown University, Rhode Island, using …

  1. Kurgan Silver badge

    It works only if the satellite electronics still work at the end of its mission time.

    I mean, the issue is that it's a somehow active system. The sat has to be able to deploy it actively after its mission has come to an end. A malfunction that kills the whole control system on the sat will leave it in orbit and unable to deploy the self-killing device. Still it's better than not having it at all.

    1. terry 1

      Re: It works only if the satellite electronics still work at the end of its mission time.

      Maybe a spring loaded deploy system held closed with power. No power, then it pops open?

      1. Prst. V.Jeltz Silver badge

        Re: It works only if the satellite electronics still work at the end of its mission time.

        doesent sound like the ideal way to use what i'd imagine is a pretty short supply of power .

        or is it ? lotta solar up there . But in that case , even when system dead solar might hold the deploy switch closed

        1. Version 1.0 Silver badge
          Joke

          Re: It works only if the satellite electronics still work at the end of its mission time.

          OK, I'll install this on my Pixel phone to watch it "work" ...

        2. DJO Silver badge

          Re: It works only if the satellite electronics still work at the end of its mission time.

          Then a self powered system that deploys the sail if it does not get a signal from the satellite control system over a set period, say 28 days.

          Minimal drain on the satellite systems, just an "I'm still alive" signal every 20 days or so.

        3. ChrisC Silver badge

          Re: It works only if the satellite electronics still work at the end of its mission time.

          "even when system dead solar might hold the deploy switch closed"

          You use a switch which defaults to the normally-open position in the absence of any power, and you design the switch control circuitry so that it needs to see a varying sequence from the host system to keep the switch held closed. Anything which prevents the host from continuing to generate that sequence, or which causes a loss of power to the control circuitry, and the switch opens...

      2. Paul Crawford Silver badge

        Re: It works only if the satellite electronics still work at the end of its mission time.

        Maybe some chemical "glue" that has a sticky life of a couple of years in-orbit?

      3. spuck

        Re: It works only if the satellite electronics still work at the end of its mission time.

        So a mechanical watchdog or deadman switch?

        Maybe a clockwork mechanism that counts down to releasing the sail in 60 days, that can be "bumped" or reset by energizing a solenoid or motor. The software could actively look for times to perform the reset when the solar panels are in full sun and there is an energy surplus.

    2. Anonymous Coward
      Anonymous Coward

      Re: Retrofit?

      I don't see why you couldn't come up with a sort of magnet, or grappling hook, or bolas sort of thing to attach this to non-equipped satellites. Combine it with a "hunter-launcher" (isn't there such a device in development?) and you've got the whole system.

      1. werdsmith Silver badge

        Re: Retrofit?

        Many a dissertation has been written on such systems as a spacecraft that could change orbits to rendezvous with defunct objects and give them a tug to expedite their descent. It usually comes out quite costly, but a decent academic exercise nonetheless.

      2. sebacoustic

        Re: Retrofit?

        Thing is, it's quite hard to find and get to those defunct satellites in orbit.

        May I quote the venerable D Adams:

        “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.”

      3. Fruit and Nutcase Silver badge

        Re: Retrofit?

        A (laser guided) basking space shark

    3. Anonymous Coward
      Anonymous Coward

      Re: It works only if the satellite electronics still work at the end of its mission time.

      No. As a matter of fact, this sail can even be weaponized. You just create a maneuverable satellite that has a bunch of sails that saddle up to "target satellites" and attaches a sail to the target. (in Space, even epoxies work quite well.) In the case of some satellites, like Starlinks, you could probably use the sale to block the ion thrusters and let the starlink's own (larger) solar sails deorbit it.

    4. John Brown (no body) Silver badge

      Re: It works only if the satellite electronics still work at the end of its mission time.

      I wonder how the economics work out? How big a sail is required and how much additional weight will that be compared to small extra amount of fuel reserved for a de-orbit burn? It may only cost $30 for the test articles but it adds to the launch cost too, but there seems to be other options available for new sats to be de-orbited. The builders/designers/operators will go for whatever is cheapest overall, ie launch cost and reliability. But the article only seems to compare this sail with the costs of separately launched de-orbiting bots. Those latter ought to only be needed for older kit. Newer kit generally already has a de-orbit mechanism. Or is this device intended to attach to existing sats to de-orbit them?

      1. Marty McFly Silver badge
        Holmes

        Re: It works only if the satellite electronics still work at the end of its mission time.

        Yeah, cost-to-orbit per pound is the real money.

        This would need to be mission hardened and fail-safe to prevent an un-commanded deployment. No one is going to trust a multi-million dollar satellite to $30 worth of consumer kit and hope it doesn't activate early.

        1. M.V. Lipvig Silver badge

          Re: It works only if the satellite electronics still work at the end of its mission time.

          They don't actually have to buy this. This proved the concept works, so satty builders can build their own parachute system.

      2. werdsmith Silver badge

        Re: It works only if the satellite electronics still work at the end of its mission time.

        "compared to small extra amount of fuel reserved for a de-orbit burn?"

        Assumes that the spacecraft has any powered impulsion engine. They don't all use thrusters/boosters - especially cubesats. Their deorbit process is to put them at an altitude where the orbit decays over a roughly predicable time. By increasing drag profile you can use higher orbits where otherwise the things would keep on flying for the foreseaable. Like ProsperoX3.

  2. Anonymous Coward
    Anonymous Coward

    Some issues remain...

    Using a drag device might remove said dead satellite from orbit...BUT surely this can only be used on satellites that will 100% burn up during re-entry.

    Also: if the drag system takes some time to actually de-orbit a bird, then there's the risk on an uncontrolled re-entry taking place that could result in pieces of space junk landing on/near to buildings which can cause a problem not only in terms of causing damage/injury/death to whatever/whoever is hit by it, but also the issue of how "irradiated" any solid pieces will be, which could cause a health issue.

    1. Excused Boots Bronze badge

      Re: Some issues remain...

      True; but assume that this system would only be used on new or potentially defunct satellites which are known to be small enough to assume that they will completely burn up on re-entry. And imagine a similar system which has a propulsion mechanism in reserve. The sail decelerates the object so that it starts re-entry, if it looks like there is a possiblity of impacting a landmass then the rockets fire to adjust the profile to bring it down over an ocean.

      Yes, I know, it won't be perfect and eventually incidents will happen, but probably better than doing nothing!

    2. that one in the corner Silver badge

      Re: Some issues remain...

      > surely this can only be used on satellites that will 100% burn up during re-entry.

      In which case, even a de-orbit burn won't be much use, will it? And as they were looking for an alternative to a burn that specific objection is hardly a failure of this design.

      But most of what is up there will burn very nicely (if you are thinking of the recent "unidentified lump from the heavens" your average satellite does not have large tanks).

      > the risk on an uncontrolled re-entry taking place

      Most of the satellite re-entries, afaik[1], are "uncontrolled", as the de-orbit burn may be just enough to drop them into atmosphere only as deep as required for them to experience drag to finish the job. It is only the big beasties, or the manned missions, where they worry about a burn large enough to get them down right away and in a planned location.

      > but also the issue of how "irradiated" any solid pieces will be, which could cause a health issue.

      Stuff in space certainly gets irradiated more than stuff down here[2], that mostly means that the space blobs are killed, which is a plus, healthwise (so only the really strong ones survive to get down here - look out, Steve!). It doesn't mean the bits of debris are themselves radioactive. My wife irradiated people for her work: they were okay to be around afterwards. Unlike the ones stuffed full of tracers, which weren't there to irradiate the patients as much as causing the imaging equipment to react: it was preferred that they hung around until they had, how to put it, safely expelled most of the materials.

      [1] as always, links to material that corrects me happily accepted.

      [2] but stay away from, say, active volcano plumes or spending too much time down deep holes in granite, or ...

  3. Winkypop Silver badge
    Flame

    Life’s a drag

    And then you de-orbit!

  4. Neil Barnes Silver badge
    Coat

    orders of magnitude less costly than rival ideas

    But not half as much fun! Pass me my stetson and lasso!

  5. Kevin McMurtrie Silver badge

    Who's doing the evil research?

    I bet there's de-orbiting research going on in secret too. Imagine a satellite that's nothing but spools of fine polyimide threads. Give the command and it shoots threads at high speed in every direction. They'd drift around in the solar winds and soon make a mess everywhere.

    1. that one in the corner Silver badge

      Re: Who's doing the evil research?

      Those threads could mess some stuff up but unlikely enough to cause other satellites to de-orbit (there isn't anything special about polyimide that makes it de-orbit stuff, it just allows you to make light-weight sheets suitable for cheap launches).

      Unless there was some strange weaver of space cloth (Norns in Spaaaace) you'd mostly get some threads spreading out away from Earth, to the delight of any spiders that managed to hitch a ride, whilst the rest drifted down and out of orbit, at which point we would have to alert the dragon riders.

      1. Neil Barnes Silver badge

        Re: Who's doing the evil research?

        Beware of the bison!

        https://www.pinterest.at/pin/629448485410642769/

      2. Kevin McMurtrie Silver badge

        Re: Who's doing the evil research?

        Spiders do an amazing job flying on threads. Volume is relative to diameter squared while area is linear. This means that fine threads have an extremely high surface area relative to their mass. On top of that, threads create powerful electrostatic charges and move to optimally gather force from them.

    2. Dr Dan Holdsworth
      Boffin

      Re: Who's doing the evil research?

      The point of the exercise is to create surface area which interacts with the extremely tenuous atmosphere still present at those heights. So, why not use a large amount of fine, metal-coated filament which will become statically charged as it deploys, together with small leaf-like bits of membrane which similarly become statically charged and end up sticking out in all directions. What you end up with is a huge, leafy cloud of fluff, which whilst it hasn't got the elegance and surface area of a sail is still a huge increase in surface area.

      Attached to any satellite this will (at least at orbital heights) increase drag and help de-orbit the satellite; it should also be light enough that the thing breaking up should be a problem.

      1. M.V. Lipvig Silver badge

        Re: Who's doing the evil research?

        I forsee using a cubesat that splits into 4 cubesats with a filament web between them. The cubesat splits out making a net that grabs more and more satellites. Eventually, enough are roped together that the orbital speed can no longer keep the combined mass in orbit, and down they come. The cubesat pieces could even have motors on board that could slow the mass down. Even if the net didn't hold, the effect on orbital speed would still be enough to force a deorbit.

  6. bertkaye

    makes the medicine go down

    My name is Mary Poppins, and I gracefully exit orbit all the time with a simple umbrella. You may license my technology inexpensively in exchange for a mere spoonful of sugar.

    1. Alan Brown Silver badge

      Re: makes the medicine go down

      Golden Brown sugar? It explains the flying...

  7. ChrisC Silver badge

    What's not clear from the writeup...

    ...either here or on the Brown website itself, is whether they left SBUDNIC with the sail stowed for long enough to establish a baseline against which the effectiveness of the sail could be compared once deployed, or if they were just presuming that their orbit would have been comparable to those of the other sats released at the same time, and were therefore relying on their orbits to provide the baseline to compare against an immediate deployment.

    Given the rather significant difference between the estimated and actual time to de-orbit, it either suggests this experiment was a roaring success in showing that the efficacy of a de-orbit sail is even higher than anyone could have predicted, OR that some other factor was at play which meant this particular sat was always going to de-orbit faster than the others, sail or no sail.

  8. Grinning Bandicoot

    Waste Not

    To date the big cost is in getting the device into orbit. After all the yammering about a nuclear plant's diluted waste water discharge where, O where, is all the outrage and oratory about heavy metal vapors and forever elements (!) being dumped into the atmosphere for the children to breath. Just compare the ratio of stupid to ignorant since the start of "The Satellite Age'.

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