European approach to Space Debris

[flynn]

<i>From ESA Portal</i><br /><font size="5">Space debris mitigation: the case for a code of conduct</font><br /><br />15 April 2005<br />There is a lot of junk orbiting the Earth and the problem will worsen unless there are changes in how spacecraft operators operate. But it is not all doom and gloom. The first steps toward a comprehensive solution are already well underway including a European code of conduct for space debris mitigation.<br /> <br />According to Dr Ruediger Jehn, a space debris specialist working at ESA's Space Operations Centre (ESOC) in Darmstadt, there are several relatively simple measures that will help reduce the amount of debris in space. Some are already being implemented by spacecraft operators at little or no cost. <br /> <br />"These steps," he explains, "are based on common sense and include measures that should be acceptable to any spacecraft operator." <br />The basic concept is simple: do not make the existing problem worse; reduce or prevent the creation of any new debris; and, in particular, strive to protect the commercially valuable low Earth and geostationary orbits. <br /><br />The amount of debris created during normal operations can be reduced by not discarding, ejecting or detaching anything that does not have to be discarded, ejected or detached. This includes payload covers, Yo-Yo despinners and instrument covers such as those used to protect the highly sensitive optical windows of sensors during launch. Lastly, minimise break-ups, a major source of small but deadly debris. <br /> <br /><b>Explosions in space</b><br /> <br />It may be surprising to anyone outside the space community to learn that spacecraft (occasionally) and launch vehicles (frequently) do in fact break up in orbit. <br /><br />Launch vehicle lower stages generally fall back into the atmosphere and completely burn up, providing a tidy, if fiery, solution but the typical fate of rocket upper stages, which are usually cast off after launch, is to blow up. <br /><br />Why does t <div class="Discussion_UserSignature"> <font color="#800080">"All God does is watch us and kill us when we get boring. We must never, ever be boring" - <strong>Chuck Palahniuk</strong>.</font> </div>

 

[bobw]

Thanks for the article, flynn. I thought it was going to be about the shielding on ESA's ATV. <div class="Discussion_UserSignature"> </div>

 

[shyningnight]

Funny...<br />A week or so ago after reading a thread about "what would we DO with an HLV?"... I was daydreaming an idea.. Probably hideously impractical;<br /><br />In one launch, launch maybe 200 simple, cheap, lightweight, "deorbit-bots".<br />Each one being as simple as possible.<br />Controlled mostly from the ground... solar powered.<br />Single electric (ion) engine.<br />Grapling "arm".<br />Minimum brains.<br />Minimum cost.<br /><br />It's duty?<br />Using the ion engine, over the course of several years, match orbits with a piece of "junk". Grapple with it. Turn engine "up". Slowly, over the course of a few more years, de-orbit the "junk".<br /><br />Now, I know there are a dozen or more hurdles...<br />Nothing that's going to last for "years" in LEO is going to be all that cheap and simple...<br />"Just grapple with the satellite" is probably worth a laugh or two from the knowledgeable.<br />So is "just match oribits with the junk"...<br /><br />The only way it would be at ALL practical is to be able to launch HUNDREDS of them, and an HLV would provide that in one expensive lauch, rather than 200 separate launches of a moderately expensive laucher.<br /><br />Can they be made light enough, and still robust enough to last for their mission life without becomeing "junk" themselves?<br />Can an ion engine (of a cheap and robust design) even have enough "oomph" over time to deorbit satellites that are big enough to be worth tasking a "bot" to in the first place?<br /><br /><br />Don't know.. but it was an interesting daydream!<br />Paul F.

 

[mrmorris]

<font color="yellow">"In one launch, launch maybe 200 simple, cheap, lightweight, "deorbit-bots". "</font><br /><br />You'd be much better off with 1 robust, highly-capable de-orbit-bot that had an ion engine, *lots* of maneruvering propellant, and a cargo bay full of EDTs (electrodynamic tethers). <br /><br />- Maneuver to debris<br />- Slap on EDT to junk.<br />- EDT engages and provides orbital 'drag' to bring debris to terminal orbit.<br /><br />The system would allow for a much smarter 'bot', and a much larger capability to bring down junk. However light you make your 'bitty-bots' -- they'll be heavier and larger than what is essentially a spool of wire. Keep in mind that ion drives need a *lot* of power, so your bitty bots need big solar panels.

 

[shyningnight]

All true, I'm sure...<br /><br />My thinking about "many vs one" is mainly one of failure tolerance...<br />If one, or ten, or twenty, die... the other 180 of them go on. With one BIG tug, you have to build in enough redundancy that you don't lose the whole "mission" with one $10 part failing. <br /><br />"Dropping" a tether is probably far easier than using an ion engine...<br /><br />Power wise, again, you're probably right that a "cheap little bot" can't get enough power from a practical size solar array to effectively run an ion engine... but then again, IF it can be made small and light enough, Maybe?<br /><br />Mostly just daydream fodder... <img src="/images/icons/smile.gif" /><br /><br />Paul F.<br /><br />

 

[mrmorris]

<font color="yellow">"...get enough power from a practical size solar array to effectively run an ion engine... but then again, IF it can be made small and light enough, Maybe? "</font><br /><br />OK -- so we make the bot a 6" cube and the solary array is a marvel of engineering that folds into a 6" cube on top of it, then unfolds out to a 2 sq M array that's enough to shift the bitty-bot. Now that bitty bot grapples with an expended Delta IV upper stage that masses 50 times what bitty bot does. The array and ion engine is no longer sufficient to shift the mass.<br /><br />Ion engines get maximum efficiency (i.e. the most bang for the buck) as the power scales up. Every time you decrease the size of the solar array, the mass fraction required for your propellant increases. Your bitty-bots will be very inefficient. Papa-bot with huge solar arrays will get much better efficiency out of the propellant mass sent to orbit. In addition -- It doesn't have to shift the mass of all of these pieces of debris -- only the mass of the individual tethers.

 

[najab]

><i>The array and ion engine is no longer sufficient to shift the mass.</i><p>Maybe not all at once, but over time....<p>Anyway, since he was using my HLLV to launch the 200 de-orbit sats, they could each mass nearly a ton!</p></p>

 

[shyningnight]

<Anyway, since he was using my HLLV to launch the 200 de-orbit sats, they could each mass nearly a ton!<br /><br />Yup.. pretty much what I was thinking...<br />"bitty bot" is not QUITE what I was thinking... more like a "1000 pound bot" as opposed to a "Battlestar Galactica Sized Artificial Intelligence Tug costing 2.3 Billion". And yes, I know i'm drastically exxaggerating YOUR point (mostly for comedic effect...).<br /><br />najaB is right... <br />The deorbit "burn" could be YEARS long... <br />There are THOUSANDS of pieces of junk... ONE "Mega-Tug" would take 200 years to do it all... whereas 200 "thousand pound" 'bots can do 200 pieces of junk in 10 years.<br /><br />MAYBE there really just couldn't be enough power to do it.. granted...<br />But in my opinion, the ONLY way deorbiting "junk" would be cost effective is with many smaller, cheaper, 'bots rather than fewer more expensive ones.<br />If your "one big bot" had one "oops" with a satellite.. it's probably toast. Whole program canned until you build another one, IF you can get the money.<br /><br />Paul F.

 

[summoner]

Remember the old show with Andy Griffith? Salvage1 or something like that. I wonder if there is enough valuable material up there to make something similar work? I imagine that it'd be prohibitavely expensive, but alot of thos old sats were made with gold components. <div class="Discussion_UserSignature"> <p> </p><p> </p><p> </p><p> <br /><table cellpadding="0" cellspacing="0" style="width:271px;background-color:#FFF;border:1pxsolid#999"><tr><td colspan="2"><div style="height:35px"><img src="http://banners.wunderground.com/weathersticker/htmlSticker1/language/www/US/MT/Three_Forks.gif" alt="" height="35" width="271" style="border:0px" /></div>

 

[JonClarke]

Thwe problem is that the most problematic space debris is too small to make rendezvous practical. We are not talking about old satellites or spent stages, or even large parts. We are talking about tiny fragments, 1 - 10 mm across. You are notgong to to rendezvous with these. You can't even track them. But it these small fragments which are are the monst common and therefore the most lethal.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[najab]

><i>I wonder if there is enough valuable material up there to make something similar work?</i><p>It costs approximately $10,000/lb to get stuff into orbit. Gold currently costs about $7,500/lb. If you took water into orbit and turned it into gold you would make a loss of about $2,500/lb.</p>

 

[flynn]

One of the few space success stories in this country is Surrey satelite technology Ltd who make microsatelites.<br /><br />Follow link, http://zenit.sstl.co.uk/index.php?loc=116<br /><br />I can't see anything on there at the minute but I'm sure I read somewhere about them working on an Ion engine for a microsatelite. <div class="Discussion_UserSignature"> <font color="#800080">"All God does is watch us and kill us when we get boring. We must never, ever be boring" - <strong>Chuck Palahniuk</strong>.</font> </div>

 

[nacnud]

I don't think that SSTL has a working ion engine yet, but they have looked at thermal electric engines. There is more on their propulsion website here.

 

[mrmorris]

<font color="yellow">"Maybe not all at once, but over time...."</font><br /><br />Ion engines *always* impart acceleration 'over time'. However, I know (or at least firmly believe) that <b>you're</b> aware of just how much ion engine efficiency depends on power. The reason ion engines work so well is because instead of using chemical reactions to convert potential energy into kinetic energy, they use electrical power to do so. The more power available on the vehicle -- the more kinetic energy can be imparted to the noble gas ions -- the more efficiently the propellant is used. The greater velocity of the ions due to a power increase translates into a capability to move larger masses more rapidly.<br /><br />Also -- using the Ion-Engine-Deorbit craft (IEDs) in the fashion described means that either:<br /><br />1. Every time the craft de-orbits a piece of debris, the IED burns up as well.<br />or<br />2. The IEDs must contain enough propellant to match orbits with a piece of debris, lower its orbit to a point that it will re-enter itself in a reasonable timeframe, and then lift itself *back* up to an orbit where it can grab some more debris (repeat). This means the IED needs a *lot* of propellant.<br /><br />By contrast, if EDTs were used for the de-orbit stage, the IEDs need only match orbits with multiple objects.<br /><br />How about a hybrid of the concepts -- launch 100 IEDs with a cargo hold of EDTs. Upon separation from the booster, the IEDs maneuver to various orbital altitudes/inclinations where multiple pieces of debris are located and then start pinballing from one to the next attaching EDTs.

 

[nacnud]

I like the last option, ConeXpress and a bunch of rats tails <img src="/images/icons/smile.gif" />