DARPA Proposes Ripping Up Dead Satellites To Make New Ones

Hugh Pickens writes "DARPA reports that more than $300 billion worth of satellites are in the geosynchronous orbit, many retired due to failure of one component even if 90% of the satellite works just as well as the day it was launched. DARPA's Phoenix program seeks to develop technologies to cooperatively harvest and re-use valuable components such as antennas or solar arrays from retired, nonworking satellites in GEO and demonstrate the ability to create new space systems at greatly reduced cost. However, satellites in GEO are not designed to be disassembled or repaired, so it's not a matter of simply removing some nuts and bolts, says David Barnhart. 'This requires new remote imaging and robotics technology and special tools to grip, cut, and modify complex systems.' For a person operating such robotics, the complexity is similar to trying to assemble via remote control multiple Legos at the same time while looking through a telescope."

Comments

Makes sense

[Fluffeh]

This sounds like one of those brilliant ideas on paper, but one that will prove infinitely harder in reality. Re-use satelites, great idea, good luck doing it though.

Re:Makes sense

[Ihmhi]

I think it would come down to a cost-benefit sort of thing.

I'm just working my way through my coffee and I haven't had my breakfast yet, so excuse any insanity in the following.

The best way I could figure one could do this would be to have a robotic "scrap yard" in space - a space station of sorts with storage bays and robotic arms and/or drones that would pull in satellites and have them be disassembled through fly-by-wire. The parts would then be stored in bays and re-assembled.

I can see a few problems with this, of course. One way or another you're going to have to get the drones/station to the satellites. You're going to have to have *something* pull up next to the satellite and either drag it into a reclamation bay or have the whole reprocessing unit go up right next to it. Moreover you'd have to fuel the reclamation station somehow, meaning the satellite that scraps other satellites would eventually need to be scrapped or refueled itself.

It might be pretty difficult to actually re-build the stuff in space, too... so another option would be to just collect the junk and return it to earth. But I'd say it takes way more effort to get something back down from orbit than it does to get it back up there. You don't need to give satellites heat shielding because they're not really supposed to return. So if you were to go the "collect parts and bring them back down" route, you'd have to heat-shield everything, not to mention things like parachutes or retro-rockets that would permit to land without smashing into the ground at terminal velocity.

So... I don't know, this idea seems pretty nuts. I don't think we could do it until we have electrically-powered engines that can be recharged with solar power and a rather large, permanently-manned space station.

Re:Makes sense

[maeka]

One way or another you're going to have to get the drones/station to the satellites. You're going to have to have *something* pull up next to the satellite and either drag it into a reclamation bay or have the whole reprocessing unit go up right next to it

Except that moving the birds from their widely differing orbits is a major expense.

I don't think we could do it until we have electrically-powered engines that can be recharged with solar power and a rather large, permanently-manned space station.

Ion drives exist. But like all things in life there is a tradeoff. Engines which don't hurl much mass don't produce much thrust. Engines which hurl lots of mass require lots of propellent, be it electrically accelerated propellant or chemically accelerated propellant.

Re:Makes sense

[SimonTheSoundMan]

For a person operating such robotics, the complexity is similar to trying to assemble via remote control multiple Lego at the same time while looking through a telescope

Sounds like brain surgery to me, not quite rocket science then. Shouldn't be too hard.

Re:Makes sense

[maxwell demon]

The ideal position for such a station would IMHO be an orbit a bit above or below the geostationary one. Such a station would be a bit faster (or a bit slower) than the geostationary ones, and thus would regularly come relatively close to each one. It would also save fuel for the "harvesting module": Only a relatively minor orbit change would be needed; basically a short thrust for getting from the circular orbit into an elliptical one whose apogee (or perigee for the outer "service orbit") is in the geostationary orbit and is reached exactly at the position of the satellite. There it grabs the satellite, does another short thrust to correct the orbit (which is changed by the addition of the satellite; also you want to get back to the station, not just to the same orbit), and thus returns to the station where the satellite is recycled.

The refueling is indeed a big problem. Thrusting always involves emitting matter, and therefore even if your energy if 100% solar electric, you still will eventually have to refuel (unless you manage to build an ultra-powerful laser of ultra-low mass -- and don't fear the risk of accidentally directing it to earth or to another satellite :-))

Re:Makes sense

[maxwell demon]

Well, If I had to decide between flying with a rocket built by a self-taught rocket scientist and having my brain operated on by a self-taught brain surgeon, I think I'd take the rocket flight.

Re:Makes sense

[drinkypoo]

I was just thinking it sounds like a really great game. It would make a dandy mod for some FPS engine that can handle rotating the player.

Re:Makes sense

[Runaway1956]

I think the lego analogy is oversimplified. They should have said it would be like building your own telvision via remote control while looking through a telescope. Legos "just fit". Diodes, resistors, etc, don't just snap together - and neither will all those parts form satellites launched by different companies, for different purposes, over the span of a few decades. Almost nothing is going to "just fit".

Re:Makes sense

[hedwards]

That was in line with my thoughts. If the devices were designed to snap out the fuel cells and reprogram the onboard logic, it could probably be made to work, at least for satellites of a similar type, but going much further than that would require technology which we don't yet have.

There's also the issue of these satellites being owned by somebody, even though they are still in orbit and unusable at the moment.

Re:Makes sense

[tibit]

Presumably a lot of military hardware uses a couple common satellite buses, so the parts could perhaps be interchangeable. I think that reusing across dissimilar craft is a pipe dream for now.

Re:Makes sense

[EdZ]

Except that moving the birds from their widely differing orbits is a major expense.

Not really. A lot of the valuable satellites will be in GEO or the geostationary graveyard orbits. Moving them around takes very little energy.

Re:Makes sense

[frank_adrian314159]

This sounds like one of those brilliant ideas on paper, but one that will prove infinitely harder in reality.

Remember that "R" in DARPA's name? It doesn't have to work. It just has to be something interesting from which one could learn something new. And I could see a whole lot of useful/interesting stuff coming out of even trying to do something like this.

Re:Makes sense

[zippthorne]

Thrust is only critical when you're trying to get off a planet. If you're already in orbit, you don't care about thrust as much as Isp, which translates to your delta-v budget...

That said, this sounds like a pretty stupid idea. The expense of getting the robot miner/factory to the retired satellite is as much as putting a whole new satellite in place, one produced using the full resources of planet-bound manufacturing, not some ad-hock remote-controlled business, and I strongly suspect that each robot would have to be specifically tailored to modify each existing satellite...

The most valuable resource a retired GEO satellite has is not the stuff in the satellite, but the position it occupies. The best solution is to build an attachable thruster as a secondary payload, and use it to nudge the satellite into interplanetary orbit so the new satellite can take it's place....

Re:Makes sense

[Anonymous Coward]

But at least now we have an idea of what they may plan on using the X-37 for.

With a few mods to this idea, it also wouldn't be too hard to use this process to tap into and record other countries satellite data. Think of the intel aspect. Completely hijacking satellites is another possibility.

Re:Makes sense

[Rakishi]

You are describing having two satellites traveling at different velocity impact each other without utterly destroying either fragile device. Just because two satellites are in the same location at the same time does not mean one can realistically "grab" the other.

Re:Makes sense

[Smallpond]

This sounds like one of those brilliant ideas on paper, but one that will prove infinitely harder in reality. Re-use satelites, great idea, good luck doing it though.

I have a closet full of old PC components and will never use most of them -- and those were designed to be interchangeable commodity parts. What are the chances that you can take a solar panel off an old satellite and use it for something? Did they standardize on micro-USB connectors? nope. Common voltage? nope. Standard mounting bracket? nope.

What other heavy items might be useful? batteries, telescopes, radios. Still less likely than my old PC parts.

The only chance this has is taking new parts up and repairing existing satellites using remote controlled or autonomous robots. Humans don't have a vehicle capable of getting to GEO. That might save a little of the cost of building and launching a whole new satellite if the robot can be reused for many missions.

The only precedent I can think of is the Hubble repair mission. On that one they found the bolts required much higher torque than they expected. I remember one of the astronauts called the Car Talk guys to ask about it. I don't think a robot would be able to pull out a cell phone.

Re:Makes sense

[TFAFalcon]

Ownership can be easily resolved.

Start charging 'rent' for satellite positions in orbit. You can bet companies will start begging people to take their broken hardware.

Re:Makes sense

[ScrewMaster]

For a person operating such robotics, the complexity is similar to trying to assemble via remote control multiple Lego at the same time while looking through a telescope

Sounds like brain surgery to me, not quite rocket science then. Shouldn't be too hard.

The round-trip signal delay might also prove a problem for someone operating a remote gripper or performing some delicate real-time operation. You're going to need some serious AI on-board to handle most things, I think: the human operator would just issue directives and the local intelligence would get the job done. Eventually, as the software develops, you won't need the human.

This isn't exactly a trivial proposition: they'd probably have to spend a good chunk of that $300 billion getting this to work. Of course, having that kind of near-space technology would be absolutely invaluable. The idea of having satellites whose only job is to zip around repairing and/or salvaging other satellites is very appealing, and would make satellite designers begin to think about standardization, or at least make sure that their platforms are built to standards that the robots can handle.

One problem I can foresee is getting enough radiation-hardened processor power in orbit. The top-of-the-line spacegoing CPUs aren't very impressive compared to a desktop machine of ten years ago. The greater your component packing density the greater the odds that a subatomic particle is going to knock a bit loose somewhere. We'll probably just have to accept that the error/failure rate of such equipment is just going to be substantially higher, and build in enough redundancy and error-detection and correction capability to make it workable. Space is not a great environment for microprocessors.

Still, once you have robots that can perform at that level, just ship components up there and have them assemble even larger facilities in orbit. Immensity can be bought very cheaply in space: getting the raw materials up there is the problem. Next step would be to set up robotic mining colonies on the moon, and use a solar-powered mass-driver to ship refined products to Earth orbit. We could have an entire space infrastructure up and running before a human being ever sets foot in it. I remember reading James P. Hogan's "Two Faces of Tomorrow": he offered a remarkable vision of such technology at work. We couldn't do it today (that's why it was science-fiction) but it would certainly be doable.

That is, if we have the vision ... personally, I doubt it. We're far too concerned with building another failed welfare state (or another failed fascist state, or both) to be bothered about such things. And that's too bad: maybe if we'd taken a trillion or so of that bailout money and put it into this kind of research we'd have something really worthwhile in a few years.

Sophisticated orbital robotics could kick off a near-space revolution as world-changing as the original Space Race, and with even greater economic return. Try convincing the President of that (or anyone on NASA's appropriations committee for that matter.) It truly boggles my mind (and depresses me, when I think about it) how many people in this country have been thoroughly brainwashed into believing that our space efforts should be shut down because they're a waste of money. Hell, if you just take economic effect of space-based weather prediction alone, our efforts in space have been well-rewarded. Now add in military tech, communications, scientific research ... the whole tapestry of sciences and technologies that have been advanced because we took some captured German V2 rockets and started experimenting with them.

Re:Makes sense

[ScrewMaster]

I don't think a robot would be able to pull out a cell phone.

True, but what would happen is that the human operator would receive a message on his screen saying, "operation halted, programmed torque limit exceeded." The operator could then decided to override the limit and see if he can't work it loose. If that doesn't work, then he or she can call up the Car Talk guys.

Re:Makes sense

[HiThere]

Why would they be in a hurry?

If it goes a little faster, it will move to a slightly higher orbit, and rotate more slowly. Wait for the place you're aiming for to catch up. Slow down, to move as fast as it does. You'll probably need tethers to do the final orbital adjustment, but by then your speed difference should be in the inches/minute range. (The tether is because it's quite difficult to exactly align in position and velocity in all three dimensions. But you want to get really close before you touch. Think of it as a flexible docking collar, without the air seal.)

This seems like a perfect job for an ion rocket. It's close enough to the sun to use solar power. There's no rush. And things are not only in a stable position already, they'll stay in stable positions along the entire trajectory. You would, however, want to use an advanced model that can operate without special fuels. (Use a laser to evaporate some of the metal from the thing you're moving, and accelerate that as your exhaust. Probably hasn't been built yet, because this is a new situation, but it's a pretty straight-forward adaptation of the current models. Think of it as a nano-scale mass-driver.)

Re:Makes sense

[icebike]

The most valuable resource a retired GEO satellite has is not the stuff in the satellite, but the position it occupies. The best solution is to build an attachable thruster as a secondary payload, and use it to nudge the satellite into interplanetary orbit so the new satellite can take it's place....

Exactly. Where are my mod points when I need them!!

The physical material in the satellite costs a few dollars. The rest of the cost is the cost of employment of large numbers of highly paid technicians on earth. As such any savings in trying to repair these things is elusive at best, and, given the nature of government programs probably impossible.

Better DARPA should invent cheap technology packages that can be launched by the hundreds latch onto or snag these dead birds and de-orbit them freeing their slot in GEO, and preventing them from joining the the ever growing space junk yard. Just a small tug that would set them on a slow path toward re-entry and burn up.

Re:Makes sense

[Lifix]

Huh... rent? So the US should charge the rest of the world 'rent' to use 'space?' please explain what you mean.

Re:Makes sense

[Intropy]

The physical materials are cheap, but the fuel required to orbit them is not. There is some value in the "real estate" as you say, but if you just move the existing satellites out of the way to make room for new ones launched from Earth, you still have to pay to get all that mass into orbit. If you can reuse some of that mass, then you can save a lot of fuel.

Re:Makes sense

[hairyfeet]

I don't think so, after all nobody is saying "you gotta get that part TODAY Johnson!" are they? you could use one of those Russian Hall Effect thruster which IIRC are pretty power efficient for their size, then as the other poster said have a 'scrap yard" where drones take them apart.

But IMHO if they are gonna do that then we are gonna need to get together with the other sat producing countries and work on a modular design for future birds. that would make this MUCH easier to do and while i'm sure that with the right design even the dead birds already up there could be stripped with modular designs it could be a hell of a lot easier.

Personally i'm all for it. anything that will cut down on the clutter up there while getting real use out of what was once junk is a great idea in my book. if this works we then need to focus on "clearing the neighborhood" of all the bits and pieces that have been piling up since the 1950s. Has anybody seen the picture of just the crap we're tracking? its towards the bottom half of the page. I didn't know until i landed on this we have 13 reactor cores and 32 nuclear generators in orbits below 1700km. we REALLY need to be cleaning this mess up!

Re:Makes sense

[dbIII]

Getting from one end of geostationary orbit to the other end and then slowing down to match geostationary orbit again is not trivial in terms of fuel costs. If the stuff is close together (unpowered things in that orbit tend to accumulate over Indonesia apparently due to differences in gravity+shape of the earth) then that is a different story. There's a lot of other stuff in other orbits you'd just have to ignore - eg. the ISS was deliberately proposed to be put in such an orbit so that it would cost less in fuel to bring new modules up from the earth than moving MIR and bolting that to it.
I get the idea that this is taking a long term view and may be about ensuring that future satellites have parts that can be removed and interchanged. It's possible we may be part way there if everyone is using brand X antennas, panels or whatever.

Re:Makes sense

[dbIII]

13 reactor cores and 32 nuclear generators

The Readers Digest of all things told me about that as a kid.
I wouldn't be too worried, the sheer kinetic energy of those things falling out of the sky is more dangerous than their radioactive properties. Once they've crashed the radioactive materials are so active that they are trivial to find (eg. fragments from a Kosmos impact in Canada were found from the air) but small enough that accidental exposure is likely to be minor. Those reactors are not the big steam generating kind we see used on earth and are only used because in space nobody can change your batteries.
Dozens of SF movies have warned me about what can happen to people that touch smoking bits of equipment that fall from the sky :)

Re:Makes sense

[Rei]

I don't know... as soon as I heard about this, my immediate thoughts jumped to, "WE COME IN PEACE... PRIORITY OVERRIDE. NEW BEHAVIOR DICTATED. MUST BREAK TARGET INTO COMPONENT MATERIALS." ;)

annoying... "filter error: Don't use so many caps. It's like yelling".

Re:Makes sense

[EdZ]

Getting from one end of geostationary orbit to the other end and then slowing down to match geostationary orbit again is not trivial in terms of fuel costs.

Orbits have ends now?
Seriously though, the energy costs are trivial, and pretty much proportional to how fast you want to move around. Move into a slightly lower orbit (maybe a few m/sec delta-v for a Hohmann transfer), then wait for a while, then move back out. The shift around the orbit is dependant on how long you wait, not on how much fuel you expend. Drop down to an orbit around 1000km lower, and you can move around the whole of the GEO track in less than a month.

Re:Makes sense

[slick7]

This sounds like one of those brilliant ideas on paper, but one that will prove infinitely harder in reality. Re-use satelites, great idea, good luck doing it though.

Odd thing is, my decades long study of the debris in orbit focuses one aspect on this very issue. Am I an engineer? No. Have I published any papers on this subject? No. Are my ideas valid? As valid as anybody elses.

Re:Makes sense

[slick7]

Except that moving the birds from their widely differing orbits is a major expense.

Not really. A lot of the valuable satellites will be in GEO or the geostationary graveyard orbits. Moving them around takes very little energy.

Don't forget the insurance recovery fees, 10%, I believe.

Re:Makes sense

[slick7]

The cost of translations are less than those of launches and the subsequent failures.

Re:Makes sense

[slick7]

The greatest cost is the installation of facilities. Once in orbit, costs drop when insurance recovery fees are factored in, as well as salvage rights.

Re:Makes sense

[slick7]

The physical materials are cheap, but the fuel required to orbit them is not. There is some value in the "real estate" as you say, but if you just move the existing satellites out of the way to make room for new ones launched from Earth, you still have to pay to get all that mass into orbit. If you can reuse some of that mass, then you can save a lot of fuel.

The whole satellite is greater than the sum of its parts. Yet, when a $150 circuit board screws up a 200 million dollar satellite network the cost of recovery and repair is less expensive due to re-usability factors.

Re:Makes sense

[hairyfeet]

But the big IF there is IF they can control re-entry which is not always the case. what if it goes down in Miami? New York? if any of these comes down in a major city the impact with the buildings will spread the shit far and wide, it would be a mess. And that of course isn't counting the loss of life from the pure panic that happens when you say the word radiation around the public. sure the device itself in a worst case would give less than a hundred people cancer, but how many will literally stomp their fellow man to death trying to get away from the ZOMG radiation?

While i agree there is a reason for having them frankly our past history with cleaning up after ourselves doesn't give me much confidence friend. Did you see that pic of just the known debris? You are basically driving a ball of radiation through a minefield and hoping like hell you don't hit something that causes you to lose control. hell look at the spectacular wipeout of that Iridium sat, with the price of those things if they couldn't prevent that, what is to keep one of these reactors from hitting Denver?

Re:Makes sense

[jimmyswimmy]

Parent is exactly right. In the defense-sciencey world, there is a whole class of problems often called DARPA-hard. I think the term is one DARPA itself uses. My company recently missed out on an opportunity to bid a project for DARPA because we had an approach based on current technology which could be fielded very quickly. DARPA doesn't do that. DARPA does crazy, hard projects with the goal of advancing technology. This is definitely an area ripe for DARPA - it is a high risk, high payoff application.

Suppose this works - the cost of putting a new bird in orbit drops significantly. Rather than destroying a satellite that isn't working quite right, you could salvage it for parts the way we do a car. So first, you haven't wasted these space-qualified and tested components, but even better, you don't have to fly new ones up there. That's not just money, it's also time. You might be able to extend the effective lifetimes of various satellite constellations, such as GPS, Iridium and GLONASS, and thus improve reliability of such systems.

There's a fairly obvious flipside, as well - I don't know if there is international law on satellite ownership, but the law of salvaging seagoing vessels is quite clear - finders keepers. You sink a boat and I find it first, it's mine to sell - including its cargo. I don't know how this applies to space, but there is a pretty obvious (to me) parallel between a sunk boat and a grossly nonfunctional satellite. To clearly state my point: suppose a Russian spy satellite breaks, and we have this capability - we could take it and break it apart and do as we like to it. Of course if not done covertly the Russians would simply destroy one of ours, but it is interesting to consider the possibilities.

Re:Makes sense

[Pence128]

This. You need another burn to get into GEO, and a again to get back out. Since the station would probably be much more massive than a satellite, it would probably be better for the satellite to match the station's orbit. If the satellite is dead, a drone could go fetch it.

Re:Makes sense

[Pence128]

Under the Outer Space Treaty, any object in space remains under the control and jurisdiction of the state which launched it. It doesn't matter if it does anything or not.

Re:Makes sense

[Pence128]

It wouldn't be too hard, but it would be impossible without everyone noticing.

Re:Makes sense

[TFAFalcon]

The rent should be paid to the country that registered the orbital position. So for example company X wants to launch a geostationary satellite. They have to go to their government, and apply for an orbital slot. The government then registers that slot with the United Nations, and begins charging the company rent.
The rent could then either stay with the government, or go to the United nations.

Re:Makes sense

[Anonymous Coward]

And who decides who gets which allocations. Not necessarily a bad idea, but I don't think it is politically workable until we have a world government, which I don't see happening anytime this century.

One question

[lennier1]

Would the whole process and those dated components even warrant all those expenses?

Re:One question

[Anonymous Coward]

Well, let's see. On the one side, we have DARPA's well-funded program, presumably chock full of experts in the field, who seem to think it is.

But then a guy on Slashdot isn't sure.

What to think, what to think...

Re:One question

[msobkow]

I agree we need to collect the space junk we've scattered in orbit. It's a hazard to future flights.

But I can't imagine that the hardware left up there is worth the expense of salvage. Most of the expense of a satellite is not the hardware itself, but the R&D that goes into them, the testing, the prototypes, the huge staff involved in the overall process of design and construction. The hardware itself is as disposable and unimportant as your PC.

Re:One question

[Anonymous Coward]

Well, let's see. On the one side, we have DARPA's well-funded program, presumably chock full of experts in the field, who seem to think it is.

But then a guy on Slashdot isn't sure.

What to think, what to think...

Experts take a backseat to politicians. And politicians fuck every engineering project they put their grubby hands on.
Witness the ISS and the SHUTTLE.
Going in geosynchronous orbit to recover useful material from satellites ? Yeah not going to happen. Not now, not in 10 years, not in 50 years. We'll have greater probability of going to Mars or the Moon before even having some kind of orbital recycling facility (not for low earth orbit).
Just look at what happens for leo satellites, instead of recycling certain components we burn them up in the atmosphere.

Re:One question

[Anonymous Coward]

$300 billion of equipment sounds like a large recoverable expense. Also, that large dollar sum has to correlate to physical stuff. That is, there is $300 billion in equipment floating around the earth that future satellites and manned ships will have to navigate around. Right now the number is increasing every year (minus the US satellite that re-entered this year and the German satellite that is about to). The value will be most realized in cleaning up the debris rather than in making satellites operational.

Re:One question

[maxwell demon]

Just look at what happens for leo satellites, instead of recycling certain components we burn them up in the atmosphere.

This story is about geosynchronous satellites. Those are not burnt in the atmosphere. Doing so would be quite expensive, indeed.

Re:One question

[Anonymous Coward]

The hardware maybe disposable here on earth but once put into orbit it gains a whole new value of at least $14,000 per pound. I believe DARPA wants to send say five robots into space to build like 40 new satellites. Also I don't think many advances worth the cost of sending a new bird have been made on most of the heavy parts of satellites since say 1975. I am talking thrusters, Antennas, Outer shells, etc. I think that it is a lot harder then it looks, and unlikely to happen without real advances in robots here on earth. It could work for say GPS birds and other birds with several carcases to harness good spares from. But only if the robots have human level skill sets.

Re:One question

[hedwards]

Or make the Chinese do it seeing as that stunt they pulled with that anti-satellite weapon contributed so substantially to the problem in the first place.The only other cases where the US in 1985 and again in 2008. Neither event contributed significantly to the problem and the latter debris is almost certainly already out of orbit.

Re:One question

[jamesh]

If nothing else, all the crap up there could be useful as reaction mass :)

Re:One question

[Intropy]

Even is the components are completely obsolete and not reusable, the components of the components could still be reusable. How far down do you want to strip it? If it came down to it, you could melt parts of the satellite down, separate out the materials, and start from scratch. The main thing you're saving is the gigantic cost of getting mass from the Earth into orbit.

Recovery of satellitesd

[Anonymous Coward]

Man, if only someone could design a launch vehicle which could also be used to capture and return old satellites to Earth for disassembly. Although knowing how these things work I suspect such a vehicle would never really be used to it's full potential and become retired shortly before someone else noticed it might be a good idea.

Re:Recovery of satellitesd

[maxwell demon]

Man, if only someone could design a launch vehicle which could also be used to capture and return old satellites to Earth for disassembly.

That would not save you the cost of transporting them (back) into space. It would only add the cost of getting them down to earth (which for GEO satellites would be quite expensive as well).

Re:Recovery of satellitesd

[Anonymous Coward]

We're talking about geosynchronous orbit here asshole. Do some research before exposing yourself as an utterly ignorant naive retard who learned eveything about space from his Star Trek box set. And it's means IT IS, moron.

Space junk

[Anonymous Coward]

I thought non-functioning satellites were kicked into a higher orbit so their slot could be reused.

As far as the idea of reusing component, I just have the thought of instead of one big piece of junk in a stable orbit turning into lots of components in unstable orbits.

Orbital Junkyards

[PolygamousRanchKid]

Earthbound junkyards work, because there's lots of interchangeable parts that can be harvested from old cars. Can the same be said of satellites, or are they made of one-time built to order parts? Also, it's one thing for a junkyard part in your car to crap out on the road. Do you want to trust satellites in orbit with used parts? Oh, just stop by the orbital junkyard, for a new used part . . .

Re:Orbital Junkyards

[robot256]

Some satellites are one-offs, but things like the GPS and NOAA constellations have dozens of virtually identical models. And speaking from experience, the space industry is moving (although ever so slowly) toward interchangeable parts to reduce costs. If they knew there were five or ten usable solar arrays for the taking, they could design the interface to accept them as well as a new parts.

The other interesting thing is that being able to salvage satellite parts would mean they would be less of a sunk cost and more of an investment. If they have a resale value after they are retired, that adds profit motive to the launching company.

Re:Orbital Junkyards

[GPSguy]

Beat me to it...

There's a tendency now to try to use more common components in new satellites, especially for meteorology birds, while there's always new science, adapting existing hardware to do the work means you might get a couple of instruments on different spaceframes, and not cost as much as the gee-whiz one-offs. Someone already mentioned that R&D, testing, SRM&QA and launch services cost a bunch. If we COULD accomplish this, then restoring capabilities on-orbit would be great.

NASA had a "Flight Telerobotic Servicer" project in the early 90's. Don't know where it went but it did get a fair bit of support and a lot of good engineering talent was pointed at it. From my interactions with DARPA projects in the past, there's a fair chance that something useful will come out of this, even if the whole program is over-ambitious.

Re:Orbital Junkyards

[Animats]

NASA had a "Flight Telerobotic Servicer" project in the early 90's. Don't know where it went...

Not very far. After some study contracts, a $233 million dollar contract was awarded, but not much resulted. A prototype arm was built and is for sale for $42,000. Early planning proposed a test flight in 1991, with a rather easy set of tests. ("Peg in hole". With a human remote operator. Really. )

Orbital Chop Shop

[Anonymous Coward]

The Pentagon is making it and they are not known for being green. So the actual purpose could be as a weapon against other satellites.

Re:Orbital Chop Shop

[benjamindees]

It's entirely possible that the "weapon" satellites are already up there and the purpose of this is to tidy up the broken ones before someone else does.

If only we had a space craft to go fetch 'em

[Dupple]

We could just bring them back to earth and relaunch them later. Now all we need is a space craft that can land on earth after a trip into near orbit...

Re:If only we had a space craft to go fetch 'em

[lennier1]

Good thing the Chinese are currently developing something based on that novel idea.

Re:If only we had a space craft to go fetch 'em

[spirito]

The shuttle is not even close to the capability to go into geosynchronous orbit!

Re:If only we had a space craft to go fetch 'em

[jopsen]

Why? the whole point is to avoid launching heavy parts like antennas and solar panels... Because they are heavy, not because they're expensive to buy...

Re:If only we had a space craft to go fetch 'em

[thrich81]

In addition to spirito's earlier comment that the Shuttle couldn't get near to geosynchronous orbit (the max the Shuttle ever got to was just under 400 miles, geosynch is about 25,000), as the article states "one of the primary drivers of the high cost is the launch costs". Thus bringing any components back defeats the purpose of the cost savings of harvesting in the first place -- one more task the Shuttle never did nor could do economically as promised.

Re:If only we had a space craft to go fetch 'em

[Anonymous Coward]

Just another nail in the coffin of Space Nuttery.

Re:If only we had a space craft to go fetch 'em

[benjamindees]

Of course it is. Capt. Willis once piloted a shuttle beyond the moon on a mission to destroy a comet headed for the Earth. I saw a documentary about it.

Ownership

[Gonoff]

Who does an old defunct satellite belong to? I suspect that it still belongs to whoever put it up there, or their executors, whoever bought the company etc.

And who is authorised to say that something is defunct anyway? Imagine such phrases as "We left it dormant for future needs." and "We were keeping it until we could go up ourselves, collect it, bring it back and repair it."

Scientists and engineers may have worked out the economics of doing this, but have they included that nasty concept of Corporate Lawyers?

Re:Ownership

[maxwell demon]

Who does an old defunct satellite belong to? I suspect that it still belongs to whoever put it up there, or their executors, whoever bought the company etc.

I'd think so, too.

And who is authorised to say that something is defunct anyway?

The owner, of course. You would probably have to pay him something for the right to reuse parts of his satellite, but as long as it's cheaper than sending up a new one, it would still be a net advantage. And for the owner it's deciding between having useless junk in space he won't ever be able to use again, or getting money for someone reusing it. It's a no-brainer.

Re:Ownership

[Anonymous Coward]

Scientists and engineers may have worked out the economics of doing this, but have they included that nasty concept of Corporate Lawyers?

Oh man if the project were viable I would just send a bunch of corporate layers up in orbit in deep freeze.
And awaken them only when needed which would be never.

Re:Ownership

[russotto]

Scientists and engineers may have worked out the economics of doing this, but have they included that nasty concept of Corporate Lawyers?

I'd expect that a satellite in a retirement orbit would still belong to the original owner, but the Corporate Lawyers aren't necessarily a large bar. If it's the original owner doing or benefiting from the salvaging, or if they get a sufficient cut of the savings, the lawyers can stick to writing contracts rather than getting in the way.

A larger problem seems to be that for this to work, it has to be cheaper to maintain a repair capability in GEO than to launch new satellites. Launching satellites is expensive, but developing and maintaining a repair capability is basically a complete unknown.

Re:Ownership

[arthurpaliden]

Salvage use law of the sea as a basis.

Re:Ownership

[Anonymous Coward]

Ha!

Try to enforce law *in loco* :D

Re:Ownership

[Anonymous Coward]

There's of course a conflict of interest if the same company building the satellites also provides the launch services (e.g. boeing (who make e.g. the GPS satellites) and ULA (apparently the DOD's favorite builder of rockets, lockheed martin and boeing).

Re:Ownership

[Edgester]

If the original owners own the satellite, then would they be liable for the space junk they leave behind? Company A's space junk takes out Company B's working satellite. Let the corporate lawyer death-match commence! If there was real punching, then I would buy a ticket.

Re:Ownership

[Pence128]

Frankensat goes to the highest bidder.

Lego, Lego Lego !!!

[Going_Digital]

Arrgh, what is it with slashdot posters, there is no such thing as Logo's, just like you don't say multiple USB's, you say multiple USB Ports. Lego is the brand name for the construction system and the components are called bricks or components, so the correct way to say this would be 'multiple Lego bricks' or 'multiple Lego components'.

Re:Lego, Lego Lego !!!

[Anonymous Coward]

Look, I know trademark law is shitty like that, but I'm going to keep calling them Legos instead of "Lego(TM)-brand plastic molded building component bricks" or whatever the official name of it is.

If you don't like it, fix the trademark law so that the common people can call things whatever they feel like, as long as nobody but Lego sells Legos.

Re:Lego, Lego Lego !!!

[Dunbal]

there is no such thing as Logo's

Oh yes there is.

Re:Lego, Lego Lego !!!

[EETech1]

I remember reading this on the back of every Lego instruction booklet when I was a kid. These are Lego bricks, or Lego blocks, please do not call them Legos as this is not the trademarked name. Funny what sticks in your mind after 30+ years! I remember reading that over and over and pondering the difference, and why on earth it would matter!

Cheers

Re:Lego, Lego Lego !!!

[shoehornjob]

Duck... here come the grammer nazi's.

Re:Lego, Lego Lego !!!

[Anonymous Coward]

That's a rule invented by trademark lawyers trying to protect the Lego trademark. Normal people don't have to follow their dictates and it is in no way illegal for anyone to talk about their legos. The idea that the Lego company is going to lose their trademark if people keep talking about their bricks as legos is rather far-fetched and overprotective to begin with. Other companies employ trademark lawyers with more common sense: for example, no one at Google complains about people "googling" for something or other, and even Hormel stopped complaining about calling unwanted e-mail "spam".

Why no Republican backlash?

[Anonymous Coward]

Why hasn't there been a Republican backlash over this? This is clearly a case of "reuse", which is one of the 3 Communist Rs (the others are "reduce" and "recycle").

Ownership

[Anonymous Coward]

It seems to me that ownership issues would be a major concern. Say corporation A and corporation B send up satellites at the same time. Both have components break in the same year, rendering both satellites useless. However, since 90% of each satellite is still usable and since the components are on the other satellite, it makes sense to cannibalize one for the other. Which one gets cannibalized? Who owns the final frankenstein?

Any VC's out there want to start a business with me? Buy up dead satellites for pennies and sell them to DARPA or become the space scrap yard. PM me if interested!

Not components, but the travel...

[jopsen]

From the article:

one of the primary drivers of the high cost is the launch costs,

It's interesting todo because the antennas and solar panels makes up quite a lot of the launch costs... they're not talking about reusing everything, just the heavy parts :)

Re:Not components, but the travel...

[gatkinso]

Heavy parts being optics, benches, batteries, flywheels, gyroscopes.... basically everything that is not reusable.

Re:Not components, but the travel...

[mspohr]

The heavy parts mentioned in the article are the antennas (large parabolic dishes) . These don't wear out and could be reused. I imagine solar panels could also be reused.

Re:Not components, but the travel...

[Anonymous Coward]

Antennae are nearly infinitely reusable, hell dishes even work with holes in em. Yes, optics are too specialised and the rest wear out. I can see value in the chassis too if you have a good enough assembly plant up there. Let's say 1/3 of the mass is reusable, the rest is junk, that's worth investigating reuse.

Makes no sense

[frovingslosh]

As the article says, the current birds are not made for this, and that is one orbit that you really don't want to play Angry Birds in. It would make much more sense to mandate that if you want GEO orbital space any new satellite would have to be highly modular and repairable, and maybe even plan for refiling (although if you think fuel is expensive here just wait to see the cost there). With an insane amount of money you might kluge together something with the current scrap, but I doubt it could offset the cost of getting the robots to do it there in the first place. Far better and safer to cut losses on the old junk and stop sending up unfix-able designs.

Re:Makes no sense

[jfengel]

It's a good idea to make mandates for the GEO orbit, but it's going to add weight and cost to the next round of birds. That makes them even more expensive, and you'd better be able to demonstrate that you will in fact be able to take advantage of it, or that will be added cost to no benefit.

It sounds like they're faced with the same situation software developers often are: reuse would be great, but much of the time it really is cheaper just to re-build another custom solution. And even if we do explicitly design for re-use, we'll probably guess wrong about what the possible re-uses should have been.

It's _never_ as simple as snapping legos together. It's always the dream, but at best you get dozens of iterations before a standard arises. I bet its the same for satellites as for software.

" are not designed to be disassembled or repaired"

[HellYeahAutomaton]

It sounds suspiciously like these satellites are products made by Apple.

Motive?

[mepperpint]

Is this DARPA's real motive or do they want the ability to cannibalize enemy satellites?

Re:Motive?

[Pence128]

Under the Outer Space Treaty, the state that launches an object into space retains jurisdiction and control over it, and is responsible for any and all damage it causes. Intentional damage would probably be interpreted as an act of war.

Huge Orbiting Junkyard.

[bejiitas_wrath]

A huge orbiting junk yard could lead to a space-station, the Chinese could build this and make a permanent step into space and help clean up all of the orbiting space junk, of which their must be millions of pieces by now. That would make future trips into space much safer.

We can only hope.

X-37

[__aazsst3756]

We sorta have one in the X-37. No idea if it is big enough to haul a satellite, or if it even has a robotic arm capable of catching one.

I believe they are looking for new missions for this spacecraft to justify continue development. Perhaps the reason for the suggestion? They are currently proposing a "C" model that is 20% larger to provide the capability to haul astronauts in the cargo bay.

http://en.wikipedia.org/wiki/Boeing_X-37

And doesn't cost $1.5bn per flight

[tp1024]

You forgot that part.

V'Ger

[Latent Heat]

Um, maybe the reconstructed satellite will want to mind meld with a bald Asian sex goddess?

Cost of bringing it into space?

[pinkeen]

I thought that the cost of bringing the satellite into space exceeds the cost of the actual hardware a lot. Does it really make sense to harvest the parts? I'd like to see numbers.

Re:Cost of bringing it into space?

[Pence128]

I don't understand the question. The whole point is to reduce launch mass.

Why not

[Anonymous Coward]

rip up the government and make a new one instead

Union Labor

[Anonymous Coward]

Screw developing more robots, although robots are cool, but this is THE REASON to send real-live Union Labor to do the job.

Darpa.

[Anonymous Coward]

DISCLAIMERS:
- Though not hostile to the US, I'm a foreigner, so don't expect me to hold your hands, too.
- Overall, I tend to consider everyone first as Earthlings, then humans and finally as citizens of a country.
- Defense usually means reacting. It seems to mean "attacking" in English (IMHO "wake up first and kill him before he kills you" is apelike, not human).

We need some kind of agreement for space like the one we have about Antarctica.

That before you recycle another country's satellite and this makes them angry; part of the Defense goals is to avoid stepping on the toes of others. Avoid creating enemies: it's way cheaper than fighting them.

Having power is great, but it's worthless without control.

We were made to have limited powers and so, until now, the world has not been destroyed. Limit yourselves before you regret having too much power.

Re:Darpa.

[Pence128]

We need some kind of agreement for space like the one we have about Antarctica.

The Outer Space Treaty is almost exactly that.

Not a new idea.

[Anonymous Coward]

http://www.imdb.com/title/tt0064691/

Actually, a reusable space plane would be real handy for this kind of job.... oh, wait.

Re:Not a new idea.

[Pence128]

Actually, a reusable space plane would be...

considerably more expensive than simply launching a new satellite, completely defeating the purpose.

It depends

[SmallFurryCreature]

A lot of reactions talk about the cost of fuel... seemingly these people forget that the satellite in question might still have fuel available that is going unused. What if out of this research it becomes clear that any new satellite needs the requirement to have enough fuel left for one last journey to the collector satellite orbit where it will be dismantled.

I wonder how a slashdot story about Darpa seeking input on a research project for some kind of network that can route around damage would be received. Seems like Slashdot is getting more and more users that immediately go negative rather then exploring the possibilities.

Re:It depends

[Dunbal]

that the satellite in question might still have fuel available that is going unused.

Considering the trivial amount of delta-v required to keep a satellite in GEO, that amount of fuel is likely to be tiny per satellite - ie not worth the fuel cost of boosting specialized fuel extraction/recycling equipment up to GEO and into specific orbits. Add this to the fact that fuel is usually pressurized, and that different satellites are probably using different fuel types - it's not the easiest component to deal with.

Re:It depends

[Anonymous Coward]

"Seems like Slashdot is getting more and more users that immediately go negative rather then exploring the possibilities."

it's just that the crowd is getting older.

and well, uh, fixing up old satellites has been done in the past. hubble is the main example of "reusing" parts instead of sending everything up again.

Re:It depends

[Pence128]

Geostationary satellites today have enough fuel left over to get into the "graveyard orbit", a few hundred km above GEO. I don't think scavenging fuel would be practical, but future satellites could use a modular system where the whole tank/pump/engine assembly is removed, refilled and bolted to a new satellite.

Junkyards in Space

[32771]

This sort of thing could really put a space station and its inhabitants to easy to understand use, fix and repair stuff in orbit. Keep most of the kinetic energy, get unobstructed sunshine, and catch some space junk - campy. Running a solar sailing race on the side as a hobby could be entertaining.

I remember that there existed a TV show about junkyard people in the past. Maybe one could come up with a space comedy around it. Some cross between Alien and Space Cowboys maybe.

Re:Junkyards in Space

[ColdWetDog]

What we really need are some Jawas.

I remember!

[32771]

I made some comment about the topic in the past. Nice, DARPA listened, or to be more modest, had a similar idea.

Darn sad I can't find it now. Thinking about it, it really isn't that hard to come up with the idea, somebody like Oberth or Ziolkovsky probably already thought about it.

Guess it is time to standaradize

[Shivetya]

if they can prove reassembly in orbit is viable then it suggests that the space industry needs to standardize to facilitate this.

How about something that shuttles satellites back?

[Anonymous Coward]

I have this perfect idea. We build a re-usable re-entry vehicle that allows us to launch new satellites, and while in orbit we could retrieve the defunct older satellite and simply bring the whole thing back to Earth. Then when the satellite's on Earth we can scrap the heck out of it, re-using nearly everything that's in it in the first place. Maybe even just replace that one pesky component that failed, re-test everything and send it back up on another mission.

I envision this space vehicle to have a huge cargo bay capable of taking heavy loads into orbit, maybe we could even use it to build and re-supply the space station. It would would re-enter the Earth's atmosphere and then act like a glider of sorts to land on a conventional runway. The payload would be removed and the orbiter prepared for another mission in less than a few weeks.

This could be the best solution out there as it gets the old piece out of orbit thereby nullifying it's danger to other orbiting objects; allows us to recycle the valuable components and progresses human exploration of space.

In fact, I know where there are about four of these very spaceships just waiting to be used. ... all sarcasm aside, the Air Force B-52 was developed in the 40's and is STILL flying today, even after follow-on fighter/bombers were developed, deployed and are now retired. There may have been a lot of things wrong with the Space Shuttle, but there were far more things -right- about it that it should have been brought into the 21st century and continued service. No, I don't work for NASA, but I've been a fan of the space program since I was a little boy.

How without the Shuttle

[Anonymous Coward]

And it's beautiful Canada Arm.

Why not a Service Station

[arthurpaliden]

Use some of those inflatable habitats and build a dry dock / junk yard in orbit. Use a tug to take stuff back and forth to and from LEO and GSO.

Re:Why not a Service Station

[Anonymous Coward]

This is a great idea!

Better yet add a "utility bay" module to the international space station and have engineers fix/repair/rebuild the satellites, for a price of course.

Use the proceeds to keep the space station funded and operational.

Re:Why not a Service Station

[izomiac]

Actually, that's not a bad idea, although I'd propose adding a small shuttle to the ISS so you don't have to reorbit the satellite. Humans are far better than robots at this sort of work, remotely operated ones especially. Given launch costs and the typical single part failure, having astronauts fix satellites is an excellent (and likely economic) reason to keep humans in space. I'm sure the military would love to be able to upgrade its spy satellites periodically, and just recall all the work that was done on the Hubble.

Re:Why not a Service Station

[Anonymous Coward]

Sounds good in theory, as it gets the smart meat up there to do the work in a shirtsleeves environment, but in practice you'd probably find it being done in a separate nitrogen-pressurised bay for fire suppression and isolation of nasties like leftover hydrazine propellant and leaking batteries. Those systems were designed for longevity in vacuum, and may not really stand up to cycling between vacuum and 0.5-1 bar.

Re:Why not a Service Station

[Pence128]

In terms of cost, LEO is the halfway point to GEO. Getting from GEO to LEO and back would cost the same as launching a brand new satellite.

And then there's the ISS...

[trenobus]

The ISS is expensive to keep in operation with a crew, so there has been discussion of taking it out of service in a few years, and de-orbiting it. My suggestion is to salvage it using robotic technology, and use the material to build new satellites in space.

The original space program had enormous technological benefits for society that would have been valuable even if we had failed to land on the moon. I believe a program to develop robots to disassemble the ISS and build satellites would also pay dividends in terms of advancing robotic technology for manufacturing and recycling, whether the goal is achieved or not.

Re:And then there's the ISS...

[symbolset]

This is interesting. Or turn it into a LEO gas station.

Re:And then there's the ISS...

[dbIII]

ISS is expensive to keep in operation with a crew, so there has been discussion of taking it out of service in a few years, and de-orbiting it

I'd say only by the people that thought the entire idea of having an orbiting research platform was a bad idea in the first place. The thing's barely been built and people want to get rid of it before it's had a chance to be used for more than a handful of projects.

Remember when you were a kid...

[ibsteve2u]

...and you didn't want to wear your older brother's patched jeans to school?

Now - under the expert leadership that contaminating politics with money yields - the space program of the United States of America is going to wear patched satellites in outer space...that's progress.

Re:Remember when you were a kid...

[Pence128]

the space program of the United States of America is going to manufacture satellites in outer space

Now that's progress.

Re:Remember when you were a kid...

[ibsteve2u]

lolll..yeah, I remember when I was a kid the little town I was from suffered pretty seriously from the 1969-1970 recession. Money was scarce - and suddenly instead of new bikes, there was a wave of "custom" bikes being made by extending the forks of an existing bike with the forks of another and so on and so forth.

But the bottom line was still the same: Because of an inability to afford the purchase of something designed specifically for the job at hand, people "made do" by slapping together parts from old systems.

Both performance and, more importantly, reliability were issues with those bikes.

Re:Remember when you were a kid...

[Pence128]

In the beginning it will be like that, but I think this is the first step to bona fide space factories: melting down old bikes and making new ones.

Orbiting

[arisvega]

".. the complexity is similar to trying to assemble via remote control multiple orbiting Legos at the same time while looking through a telescope."

Fixed that for you.

Shadow Moses

[Anonymous Coward]

So where does Solid Snake fit into all of this?

Maybe it's not about OUR satellites...

[time961]

It seems possible that the Defense Department is researching this technology not just for economic savings. If technology like this existed, it could be used, for example, to remove a nifty new imaging sensor or radar component from someone else's satellite, or maybe to add a device that connects to that satellite's internal data bus (operation Ivy Bells, anyone?) and taps or modifies the data.

Most satellites have essentially no situational awareness, because being taken apart by little aliens in shiny green spacesuits (or by advanced remanufacturing robots) is just not part of the threat model. So it tends to be very hard for ground control to distinguish between a random equipment failure and a failure caused by deliberate modification of the spacecraft.

This mission probably isn't what the X-37 is for, since it's a low earth orbit vehicle, not geosynchronous.

Re:How about something that shuttles satellites ba

[Anonymous Coward]

Do you realize how fucking stupid and clueless you sound? Oh go shed a tear over the delusions of the Space Age already. It's OVER. FINISHED.

MOVE THE FUCK ON ALREADY

Return to Earth ?

[Latinhypercube]

Return to Earth ? Are you a fucking retard ? Did you miss the whole fucking point ?

What I would like to see

[symbolset]

A sort of suicidal hunter-killer micro bot bird flock. Launched with scores of these bots in each rocket, on attaining orbit they spread out, attach to dead junk and deorbit it. Or aggregate it all in one spot for this proposed mechbot to service.

Why not fix the existing ones?

[subreality]

If one component is failed, why not replace it? The reason we don't do that now is that it's a complicated operation to do in space but if the point is to develop the technologies to make this kind of salvage possible, wouldn't it be just as easy to replace the broken part in some cases?

Re:How about something that shuttles satellites ba

[aix tom]

Of course the ONLY value these parts have up there is that they are already up there. Bringing them back would make absolutely no sense at all, since that would destroy the only value they have.

And if we start "harvesting" working satellites?

[doobydoobydoo]

Wouldn't this technology also allow working satellites belonging to others to be "harvested"?

Most Spy Sats Arent High-Flying

[koestrizer]

..either. Retry your argument.

Been saying this for years...

[Anonymous Coward]

There are definitely issues to work out, but the costs involved with getting one pound of anything into space is incredible. Once you get it there, if you can figure out how to recycle it and keep it there, there are definitely savings to be had (and therefore... money to be made). A current 3D printers would require some gravity, but get past that and just about anything plastic can be recycled. How about some kind of solar furnace and aluminum? I'm in. Let's do it. :-)

Reducing fuel needs

[ChrisMaple]

There's no need to rush. Solar sails can move Mr. Fixit from one spot to another. Or Mr. Fixit can attach a sail to junk, and program the sail controls to take the junk to a junkyard (a.k.a. the moon).

Would people really panic so much anyway?

[dbIII]

Although those bits are fast they are not large. If it comes down in a major city it's not going to do as much damage as a light plane coming down at speed and it's going to be easier to find the radioactive bits than in a remote area. Remember that even fairly weak sources of gamma rays are very easy to detect. Would it even give one person cancer before they get away from it? They'd have to be pretty unlucky or ignore the likely evacuation order.
Take a look at wikipedia or elsewhere for these devices. They are not large. A lot of them are just a small photon source and a photovoltaic.
Also people tend to panic a lot less in real disasters than in disaster movies. Two towers down and fear of more terrorist attacks did not result in a lot of people stomping their fellow man to death to get out of New York.

Re:Would people really panic so much anyway?

[hairyfeet]

But that was a plane not ZOMG radiation. When you are dealing with NBC threats you are dealing with the "invisible death" problem as i call it. With a plane, gun, bomb, etc you have something that is easy for folks to visualize which gives them the false illusion of control and that helps to calm them. they think "I can run, I can dodge, i can duck under that awning" and this gives them comfort.

With NBC you have invisible death, where until you start puking blood you wouldn't know if you were surrounded by it which scares the fuck out of the human animal. Look at outbreaks of disease in Africa where they tried to quarantine. Even though they were risking the lives of possibly millions by spreading the disease many would try to run the blockades, why? because as long as THEY feel healthy right that second they think "if i don't get away from this it'll get me too!" and because they can't see the threat they felt out of control and that again scares the shit out of folks and a scared cornered animal is the most dangerous.

So while I agree the actual risk would be small this is one area where if it came down in a major city I'd want the gov to lie their asses off. Say its the busted ass end of some commercial bird and just not let the people know shit. because folks react a hell of a lot differently when it comes to threats they can see and those they can't.

Not a one dimensional problem

[dbIII]

Orbits have ends now?

I'll try to put things more clearly. If you are going to change your path of movement to that of another object you not only have to get there but also match speed and direction with the other object. That means at least two changes.
Your "just drop down to a lower orbit" means a change in speed so an expenditure of fuel. Once you have the right position "below" as you suggest (which it won't be because it's not a stable orbit, in fact the altitude would still be around geostationary) it's then another burn to get to the object you want to match orbits with and then another to slow down and match the orbit. That's not going to be a trivial expenditure of fuel unless the distances are trivial. If it's 180 degrees away waiting a long time isn't going to solve the problem because gravity is making it harder to get back into geostationary orbit with every passing second.
You have think about it in two dimensions of polar co-ordinates instead of just one :) Maybe think of it in terms of gliders flying parallel to the ground and you need to get from the one in front to the one behind. If gravity could be ignored they wouldn't stay in orbit anyway.

Re:Not a one dimensional problem

[dbIII]

Once you have the right position "below" as you suggest (which it won't be because it's not a stable orbit, in fact the altitude would still be around geostationary)

You'd probably be going up at a reduced forward speed to act against gravity bringing you down over time.

Re:Not a one dimensional problem

[Pence128]

Stop it before you give someone an brain aneurism.

(which it won't be because it's not a stable orbit, in fact the altitude would still be around geostationary)

What are you smoking? Here, read this.

it's then another burn to get to the object you want to match orbits with

Do you honestly think it takes the same amount of time to make an orbit regardless of altitude? I'll give you a hint: the ISS orbits the earth in 91 minutes.

That's not going to be a trivial expenditure of fuel unless the distances are trivial.

Distance? Who carers about distance? If you're moving, you'll get there.

gravity is making it harder to get back into geostationary orbit with every passing second.

What is this I don't even.

Re:Not a one dimensional problem

[dbIII]

Stop it before you give someone an brain aneurism

You mean start thinking :)
That link is about something completely and utterly different because it's about shifting into different orbits and not another location in the same orbit - and it's a bit much that you both misunderstood that and implied that I'm on drugs because I didn't misunderstand that. Look at my other post for an idea of what velocity (both speed and direction) to start with.

Do you honestly think it takes the same amount of time to make an orbit regardless of altitude

Where the hell did you get that idea from? I didn't imply that in any way at all - plus it should be obvious that once you start moving from a stable orbit you are not in a stable orbit anymore. The time taken for one revolution isn't going to constant for a revolution because your angular velocity isn't going to be constant - the time to go around is the time to go around, nothing more, nothing less. Forget about times for orbits. All of that changes when you speed up or slow down. Orbital velocities are for a stable state and when things are changing they are not stable are they?

It looks like the bit about having to climb back up if you let gravity drop you down was not obvious so I'll try again. The angular velocity (http://en.wikipedia.org/wiki/Velocity) of moving in geostationary orbit is keeping you up, and if you cut that velocity gravity is going to accelerate you towards the ground and you'll have to expend some energy to get back up to the right altitude again. The fuel costs are not going to be trivial unless you are advancing or receding a trivial number of degrees around the orbit since the more time spent dropping the more energy is going to be required climbing.

Distance? Who carers about distance? If you're moving, you'll get there.

No. It's all about matching velocity as well as matching location. That requires more fuel than just getting to the location (and the location is moving anyway).

Re:Not a one dimensional problem

[Pence128]

shifting into different orbits and not another location in the same orbit

That's how it's done. You move to a different orbit, wait a while and then move back. I thought you were on drugs because you keep talking about unstable orbits. The only way an orbit is unstable is if you intercept the body you're orbiting, reach escape velocity or a third body causes you to eventually do one of those things.

Here's how it works: you decelerate from GEO into an elliptical orbit with a perigee about 100km less than GEO. when you reach perigee, you decelerate again to reach a circular orbit. You are now in a circular orbit 100km lower than GEO, orbiting slightly faster than GEO. You wait until you've moved forward the required amount and reverse the process to get back into GEO. Get it?

Re:Not a one dimensional problem

[dbIII]

Forget about orbits and assuming they are some sort of fixed quantum state instead of just the balance of forces. It's all going to change the moment you apply another force. Think in two dimensions and think in polar co-ordinates. Take a look at my other post with a very rough diagram. You can't just "wait" because gravity is not waiting for you, so the longer you "wait" the more fuel has to be expended to get to where you want to go.
The irony is your suggestion that is supposed to save fuel would cost a lot of fuel because of all the changes. Take a look at my post labelled "Maybe this will help" and if it doesn't you might need to find a high school physics textbook. That's not being deliberately cruel like your misplaced "Get it", that's a serious suggestion because this is all very interesting stuff and with understanding will come enjoyment.

Re:Not a one dimensional problem

[Pence128]

Sorry, clicked the link in an email and didn't see your other post.

Yes! I like the wheel analogy. OK: you don't get off the wheel, you move to a different wheel which is slightly smaller and slightly faster. Understand that?

Re:Not a one dimensional problem

[dbIII]

It's not like that, it's not a single dimension that is just a list of orbits. Please take a look at my post labelled "Maybe this will help".
Note that the change in that example is not really an orbit because if you go all the way around you won't quite make it back to the high point on the next time around. Going lower costs because gravity increases the lower you go.

Re:Not a one dimensional problem

[Pence128]

Hm.... Do what NASA would do if they were in GEO and wanted to be in a circular orbit with an altitude of 35,686km, 100km less than GEO. Since you are in a lower orbit, your angular velocity is higher right?

Re:Not a one dimensional problem

[dbIII]

Just look at that post "Maybe this will help" and get back to me. The X axis is angle, Y axis is altitude and the reference frame is fixed on the two satellites in geostationary orbit as if they are two fixed points. Then you might get some idea of what NASA would do.

Re:Not a one dimensional problem

[Pence128]

I know what NASA does and that's not it. From the top: I'm in orbit 100km lower than GEO. My angular velocity is higher than objects in GEO and on the earth's surface. If I look down, I see that I'm moving eastward relative to the surface of the earth. When I'm over the point I want to be, I move back into GEO. The delta V required is about 10m/s.

Re:And if we start "harvesting" working satellites

[Pence128]

Yeah, but the law doesn't.

Maybe this will help

[dbIII]

To get from one point on an orbit to another point on the orbit you can both slow down and oppose the acceleration due to gravity by going "up" and getting pulled "down" over time after the burn. So flattened out with the orbital direction from left to right you would have an arc something like this to get from S1 to S2:

_____path
__path___path
S2___________S1
________________burn direction

(Ignore the underscores, spaces get formatted out and the junk filter hated my version with dots showing the arc.)
Once you get there you need another burn to speed up and have the right heading.
All this of course takes fuel. For major changes in angle it takes more fuel than minor changes. You can't just "get off the wheel", wait, and then climb on again. There's nowhere else to stand.

Re:Maybe this will help

[EdZ]

To get from one point in an orbit to another, you make two transfers. One to a lower faster orbit, then one back to the higher slower (original) orbit. As the lower orbit is faster, you track forwards relative to the original orbital position. The transfers are Hohmann transfers, which are pretty much the most efficient way of getting around when gravity slingshots or low-thrust-high-ISP sustained burn motors are unavailable.

What you appear to be describing is to thrust semiballaistically 'above' the orbit, which is a really odd thing to do (you're not on a surface, you're in microgravity!), and a massive waste of fuel.

Re:And if we start "harvesting" working satellites

[doobydoobydoo]

There are lots of things the law doesn't allow that governments and the military get away with.

Re:And if we start "harvesting" working satellites

[Pence128]

Ok, what if you say, rendezvous with the satellite harvester, except you overshoot by a few km/s

No! Rotational speed is not the whole thing - 2D!

[dbIII]

I know what NASA does and that's not it

No you don't - with respect you are not even grasping the concept of rotation and are only thinking of fixed circles which is why I'm trying to describe it to you in a more familiar set of 2D co-ordinates. It's not a silly single dimension idea of concentric rings of wheels, there is a second dimension. You don't just step from one orbit to another without passing through intervening space and in fact you would never want to if you just want to shift to a different angle at the same altitude. Instead you completely leave the circle and go for an arc that would be slightly elliptical if it was to be a complete orbit - there is no need to waste fuel moving into a different circular orbit and getting out of it again (4 burns with your idea if you think about it - you can't get the change in velocity for free).
Even with just two burns with that arc that would become an ellipse it's not going to be trivial amounts of fuel for large changes in angle. The greater the divergence the greater amount of fuel you've got to burn at the start and finish. Even if you don't care if it takes 100 intersections of the two paths to get to the end point you still lose something - gravity is making the angle between the two diverge a bit with every orbit and in the end you've got to burn fuel to get back on that circular track. The longer you "wait" the more fuel you need to burn to correct it at the end. There is nowhere to step off and no free ride anywhere apart from down.

That is a very different thing - it's GEO: 1 orbit

[dbIII]

No no no - the situation here is moving around in the same orbit to do things with satellites in geostationary orbits. What you are describing is to move from one orbit to another - read the web page.
You could move to another circular orbit, stabilise in and then move back up again - which seems to be what you are suggesting - but that would take four burns and you don't need to do it, space has more than one dimension guys! It doesn't just have be a ring of circles numbered one to whatever. Things can move at angles as well and there are elliptical orbits.
As for microgravity that's all relative within objects in space but the orbiter is going to be influenced by a really big mass that is relatively close - take a look at Newtons law of gravitation that you seem to have temporarily forgotten :)

Pirates

[hoboroadie]

The first thing I thought of was the Military chopping bits off other country's satellites, and then a maybe Star Trek episode with a rogue robot wandering the galaxy cannibalizing stray hardware, slow-moving starships, &c.

Re:Pirates

[drinkypoo]

Sorry if I'm fixated on games, but it's where these ideas can be realized most cheaply. Some space sim games actually have meaningful damage locations, if you improved that such that the geometry was meaningful in other ways (with mass, thrust, weapons with energy output of specified kinds and so on) then in theory you could implement this. I think the side-scroller that resembles it is called tumiki fighters but maybe not.

Re:That is a very different thing - it's GEO: 1 or

[EdZ]

It doesn't matter how many dimensions space has, transferring to a lower orbit and waiting will be the most energy efficient approach to move around. If you want to move around in the same orbit, you'd need to thrust continuously, and use up large amounts of propellant for no good reason.

Things can move at angles as well and there are elliptical orbits.

What else do you think a Hohmann transfer is?! An elliptic orbit that lets you move from one circular to another.
If you're suggesting altering the plane of the orbit though, that'd take a massive amount of propellant and completely pointless.

Re:No! Rotational speed is not the whole thing - 2

[Pence128]

you are not even grasping the concept of rotation and are only thinking of fixed circles

What, you're reading my mind now? Fixed circles? what gave you that idea?

You don't just step from one orbit to another without passing through intervening space

If you're in a circular orbit, simply increasing or decreasing your velocity will put you in an elliptical orbit with perigee or apogee at your current position. If you're in an elliptical orbit, increasing your velocity at apogee or decreasing your velocity at perigee can put you in a circular orbit.

there is no need to waste fuel moving into a different circular orbit and getting out of it again

It's not wasting fuel. Fighting gravity is wasting fuel.

(4 burns with your idea if you think about it - you can't get the change in velocity for free)

The amount of propellant expended has nothing to do with the number of burns. It has everything to do with the total change in velocity, which is about 10m/s for a 100km difference. In reality, you can get away with a lot less than that.

it's not going to be trivial amounts of fuel for large changes in angle.

That's why no one does that. Satellites don't even have enough thrust to do that.

...no free ride anywhere apart from down.

Ok, I think I've got it. This is wrong, There's no free ride anywhere, not even down. If you're not going fast enough for a circular orbit at your altitude, you are pulled toward the earth by gravity. Your altitude is falling, but your velocity is increasing. Eventually you reach a point where your velocity is too high for a circular orbit at your altitude, and you go flying out into space again. This is an elliptical orbit. The ellipse isn't centred on the earth, the earth is at one of the foci.

Re:No! Rotational speed is not the whole thing - 2

[dbIII]

What, you're reading my mind now?

No, reading your posts where you have made that extremely obvious. If you can't understand what I have below go find a first year engineering or physics student or a bright high schooler to sketch you up some diagrams because it's hard to get you from nowhere to somewhere without diagrams.

It has everything to do with the total change in velocity, which is about 10m/s for a 100km difference

It's more than that because it is happening in two dimensions.
Angular velocity and radial velocity and you don't get from A to B by magic - you get there by motion. That requires expending extra energy.

Re:That is a very different thing - it's GEO: 1 or

[dbIII]

Look - the question was about getting to a different angle in the same orbit - it's NOT about getting into a different orbit. There no point just going to wikipedia and finding the first entry with orbit in the title because that is answering a totally different question. Think about RADIAL velocity instead of just forgetting that it exists.

If you want to move around in the same orbit, you'd need to thrust continuously

No you don't because you don't have to stick to a circle - there are other arcs that can intersect that circle and there is more than one dimension. I'm sure you know this but I'm writing it just in case you don't so please don't get offended, and I should have really written this in the reply to the other guy that is a bit furthur behind. A one dimensional description has position only in terms of altitude and only angular velocity, and some people leave school thinking that's enough and satellites hop from one circular orbit to the next. That's not enough to describe moving around an orbit. You need to be able to consider radial velocity in addition to angular velocity. That is what I meant when I tried so many times to point out the mistake by writing that it's not a 1D problem.

that'd take a massive amount of propellant

You've got that right and so will staying on the same plane and changing the angle around the orbit. You don't get that for free no matter how long you wait or what course you are on.

I get the impression you've forgotten about what the article summary was about since you keep going on about transfers to a different orbit:) It is about moving around getting bits off geostationary satellites to do repairs or build new ones.

What else do you think a Hohmann transfer is

But this is NOT about doing that and is about a different change in location.

Just as well the article wasn't about a skip trajectory. I'm amazed how long this thread has got with something this simple.

Re:That is a very different thing - it's GEO: 1 or

[dbIII]

Sorry to reply again, but you'll probably see what I mean best if you draw some circles and ellipses on a sheet of paper. Each change in direction costs fuel so you'll see what I mean about two changes instead of the four you'd need to do two Hohmann transfers with everything else equal (same burn angle and time).
What I'm trying to get across is that it isn't easy to move around an orbit and the method you've suggested makes it twice as hard as it could be.

My idea...

[hesaigo999ca]

I had a similar idea way back when they announced they were retiring the shuttle....so I mentioned maybe letting it do one last up, but not a down, and leave it in space for parts that could be used for future projects needing materials etc.... but was found by most to be idiotic with this type of thinking, yet here we are many years later with a similar idea about satellites...which to me makes perfect sense....however I will say what someone else told me....

The satellites are old technology and probably do not contain anything worth salvaging, ....but my true feelings are that any type of material can be useful for fixing stuff, not just creating stuff....so why not???

Re:That is a very different thing - it's GEO: 1 or

[EdZ]

Radial and Angular velocity are two ways of writing THE SAME THING, just in two different coordinate systems (polar and Cartesian respectively).
You seem to think that four small burns will take up more fuel than two large burns (to move in and out of the ellipsoid you're proposing would take LARGE burns). The reason I keep going on about 'transitions to a different orbit' is because every time you thrust, you're transitioning to a different orbit. The orbit may or may not be circular or stable, but it is an orbit. There is no 'just changing locations in an orbit', orbital motion does not work like that. Moving about efficiently is all about picking the orbits with the lest amount of energy needed to move between them. It takes LESS energy to move from GEO, via a Hohmann orbit, to a sub-GEO orbit, via a Hohmann orbit, and back to GEO, than it does to thrust into an elliptical and than back to GEO in one go. The reason is simple: the elliptical will have a large difference in eccentricity, so circularising would take a lot of propellant. Hohmann transfers are, by definition, the orbit with the smallest difference in eccentricity between two orbits.

But you don't need to take my word for it: look up every satellite launch ever performed within Earth orbit: all move around via Hohmann transfers. NASA, JAXA, the ESA, Roscosmos, and everyone else, don't do that for shits and giggles; they do it because it's the most efficient way of moving about using chemical propellants.

Re:That is a very different thing - it's GEO: 1 or

[dbIII]

Radial and Angular velocity are two ways of writing THE SAME THING

Sorry that was a typo - I meant the radial and perpendicular components of the angular velocity. In this thread there seems to be a lot of ignorance that there is anything other than the perpendicular component. (Also they are not the "same thing" unless there is no perpendicular component). Anyway, without considering both there's no way to actually understand the situation, only pretending to understand by mentioning terms that sound sortof as if they might fit if you repeat them enough.

all move around via Hohmann transfers

As I said above they are moving to a different place to what we are discussing. It looks like you've just found the first thing that mentions orbits and assumed it fits in all cases.
I also suggest you get that pencil and paper and look at that Hohmann transfer again, plus I sould have put with everything else equal (same burn angle and time) in bold so you would have noticed it last time. Your "the elliptical will have a large difference in eccentricity" is not necessarily correct - it's just hard to draw it with ASCII art otherwise and still be readable :) The radial component would be just enough to counteract gravity for the time needed to get to the right angle - slower so you drop faster and have to climb at some point if you want to get back to the same orbit.
You are almost there - you wrote "circularising would take a lot of propellant" but for some reason have yet failed to understand that you do that TWICE with your suggestion which is why it is a bad idea.

Re:That is a very different thing - it's GEO: 1 or

[Pence128]

From the post with your diagram:

To get from one point on an orbit to another point on the orbit you can both slow down and oppose the acceleration due to gravity by going "up" and getting pulled "down" over time after the burn.

I didn't want to do the math, but I suppose it's the easiest way. Ok, you thrust to reduce velocity and thrust upwards to compensate for gravity pulling you down. The length of GEO is about 265,000km. If you slowed yourself by 5m/s (half of my rather extravagant budget) it would take 307 days to go 180 degrees. That's 307 days you have to accelerate an average of 1.456 x 10^-3 m/s^2 away from the earth for a total of 38.62km/s. This is enough for a mars landing and back. Add another 5m/s to get back up to speed. If you don't thrust away from the earth, gravity pulls you down. This isn't a problem, because when you thrust to speed up again, you'll come right back up. Again: -2.5m/s to go into an elliptical orbit, -2.5m/s again at perigee to go into a circular orbit at GEO - 100km, wait until you're 1/2 orbit from where you want to be, +2.5m/s to go into an elliptical orbit and at apogee you will be exactly were you want to be, going in the direction you want to be going, and 2.5m/s too slow. +2.5m/s. So your choice: 38,630m/s or 10m/s?

Re:That is a very different thing - it's GEO: 1 or

[dbIII]

Wow. You really need to sketch it out on a sheet of scrap paper to visualise what is going on if you are getting that sort of result :) Accelerating all the way back? WTF? You can go up and down instead of staying on the one dimensional circular track which is what I've trying to point out all of this time. WTF do you think you do to start a Holman transfer? It's not a magic trick to jump from one location in one dimensional space to the next - it's a movement in two dimensions and there can be other movements in two dimensions and other things you can do with non-circular paths.

I'll see if I can explain things a bit more clearly. For 180 degrees you don't have to hit it on the first pass. No Holman transfer needed - that first little kick DOES put you into an elliptical orbit it was just that I was showing the first part of the arc that makes up an ellipse if it does a full orbit. If the first intersection doesn't get you there one later on will, but of course as time progresses gravity is pulling you down a little bit with every orbit that you are doing less than the stable speed at GEO. When you get to the right angle you then accelerate in the transverse direction and cancel your radial velocity to properly get back into GEO. Say if you start with a 2 degree "hop", that's 90 orbits (or maybe less since the incident angle between the ellipse and circle will change as gravity just keeps on accelerating you towards the ground) to get to 180 degrees and probably not a huge amount of time so probably not a huge increase amount of radial velocity change from gravity. It's hard to describe, but if you sketch it you'll probably grasp it almost instantly.
As for the choice - obviously neither and sadly your 10m/s is wrong as well because you are ignoring the radial compenent of getting in and out of the elliptical orbits to move!!! 2D problem! Why are you guys not listening when I keep repeating that over and over and also convinced that you are correct without going anywhere near the mathematics?
Anything with rotational motion or conic sections really seems to confuse people without any background in engineering or physics :( It appears you only get simplistic bullshit about a mass on a string and teen arrogance taught instead of anthing useful.

Ah, heck...I won't be able to laugh...

[ibsteve2u]

...when somebody mangles "It's not heart surgery." and "It's not rocket science." into "It's not rocket surgery." anymore.

Re:That is a very different thing - it's GEO: 1 or

[Pence128]

Ok, I think I know what you're trying to do. You want to enter an elliptical orbit with perigee inside GEO and apogee outside GEO so that it intersects GEO at two points. Confirm/Deny?

You can go up and down... ...WTF do you think you do to start a Holman transfer?

You accelerate perpendicular to gravity. Here, read This. Look at the diagram.

I should have done the math properly: To move from GEO to GEO - 100km, you need:
sqrt(earth geopotential/42164km)*(sqrt(2*42064km/(42164km+42064km))-1) = -1.8257 m/s and
sqrt(earth geopotential/42064km)*(1-sqrt(2*42164km/(42164km+42064km))) = -1.8268 m/s
To get back to GEO you need
sqrt(earth geopotential/42064km)*(sqrt(2*42164km/(42164km+42064km))-1) = +1.8268 m/s and
sqrt(earth geopotential/42164km)*(1-sqrt(2*42064km/(42164km+42064km))) = +1.8257 m/s for a total delta-v of 7.305 m/s.

Re:That is a very different thing - it's GEO: 1 or

[dbIII]

You are still only doing it as 1D - that's like trying to find the area of a circle using a single triangle and is never going to work. Read the bit under "explantion" and then consider that time while moving and in the lower orbit matters because gravity hasn't gone away.
This may at least make you think you understand: imagine a Holman transfer, now imagine putting it on a slight angle to go up a bit and instead of going to a lower orbit ending up on the same one. For large changes you might go around a few times just like the shuttle did getting to orbits at different heights doing an actual Holman transfer (ever notice they sometimes took a day or so to get there instead of minutes - they went around a few times to save fuel). So like a Holman transfer only different (or in other terms, an ellipse). It's just swapping the simplist case which does not fit for a slightly different variant. Happy now?
Anyway, maybe from your 1D attempt at considering a 180 change by decellerating back to zero velocity (which by your 1D model would then put the object in the centre of the earth) you might have got a bit of a rough idea that moving around in the same orbit is not so trivial as a poster suggested a long way above. All we need now is an online physics textbook that can take you through step by step until you can actually understand what a Holman transfer is instead of just bringing it up as if it's a magical incantation. There's no point linking it like above and pretending it's the answer to anything until you've read through it and understand it.

Re:That is a very different thing - it's GEO: 1 or

[Pence128]

You are still only doing it as 1D

I'm ignoring you when you say this because otherwise I'm forced to think you are crazy.

that's like trying to find the area of a circle using a single triangle and is never going to work.

I have no idea what this is supposed to mean.

Read the bit under "explantion" and then consider that time while moving and in the lower orbit matters because gravity hasn't gone away.

Still don't know what you are saying here. There are only two thrusts in a Hohmann (note spelling) transfer and in the ideal case they are assumed to be instantaneous.

... and instead of going to a lower orbit ending up on the same one.

You're going to do better than this. If you accelerate in any direction you are in a different orbit.

Anyway, maybe from your 1D attempt at considering a 180 change by decellerating back to zero velocity (which by your 1D model would then put the object in the centre of the earth)...

Where did you get this? The relevant line is "If you slowed yourself by 5m/s..."

...you might have got a bit of a rough idea that moving around in the same orbit is not so trivial as a poster suggested a long way above.

That's why it's stupid and no one does it. You transfer to a different orbit and wait for the right phase.

...actually understand what a Holman transfer is instead of just bringing it up as if it's a magical incantation.

I know what a Hohmann transfer is. You can't even spell it. Go read it again. Come back when you get it.

Re:That is a very different thing - it's GEO: 1 or

[dbIII]

May I draw your attention the the first line of the wikipedia page you keep pretending is the answer:

In orbital mechanics, the Hohmann transfer orbit is an elliptical orbit used to transfer between two (typically coplanar) circular orbits.

May I also point out that the article is about getting to satellites located at different points in a single orbit.
That really puts your "Come back when you get it" in a different perspective doesn't it?

Now I suggest actually reading some of things I've written above and other things on the subject and you may get a glimmer of a clue why I wrote that it's not trivial in terms of fuel to move to another location in the same orbit. Don't ignore the 1D comment and get insulting about it because it tells you where your mistake is which is why I've kept repeating it in the hope it will sink in.
We are not talking about a weight on a string going around in a circle but instead about orbital transfers. The simplist case you could find does not fit because it doesn't address anywhere near the actual problem - for instance it ignores time and the suggestion that you just "wait" in a lower orbit depends upon time for it to work! Of course if you ignore time any extra fuel costs due to gravity working on the object over time also get ignored which makes it a useless model that will give very unrealistic results and make the model look very attractive to those that do not understand what the model is supposed to represent.

Re:That is a very different thing - it's GEO: 1 or

[Pence128]

I've explained multiple times how the Hohmann transfer is relevant, but we'll get back to that.

I can't be thinking in one dimension. Circles and ellipses don't exist in one dimension.

Of course if you ignore time any extra fuel costs due to gravity working on the object over time also get ignored...

There are no "extra fuel costs." Where did you get that idea? Better question: what do you think would happen if I waited forever?

Re:That is a very different thing - it's GEO: 1 or

[dbIII]

I can't be thinking in one dimension. Circles and ellipses don't exist in one dimension.

In polar co-ordinates a circle is defined by only it's radius (1D) while a point is defined by radius and angle (2D). Now do you get it? The problem is changing angle and thus not solvable in 1D, and is also dependant upon time.
Your unjustified arrogance is getting more depressing with each indication that your ignorance is deeper than expected :(

Better question: what do you think would happen if I waited forever?

Unless energy is expended to maintain the forward velocity the orbit will decay into an elliptical orbit and the satellite will eventually fall to earth. The higher it is the less acceleration towards the ground there is due to gravity and the longer it will take for the orbit to decay to a given point. Now do you see why time matters and why altitude (radius) matters?

Re:That is a very different thing - it's GEO: 1 or

[Pence128]

In polar co-ordinates a circle is defined by only it's radius (1D)

Define an ellipse using only one number.

Your unjustified arrogance is getting more depressing with each indication that your ignorance is deeper than expected :(

I was thinking this about you, but I wasn't going to say it.

Unless energy is expended to maintain the forward velocity...

There's drag in space now? News to me.

Gravity!

[dbIII]

Define an ellipse using only one number.

Think about what you've written there calmly and you'll see I'm talking about an elliptical transfer alone instead of requiring an expensive drop down to a circular orbit which is not required and you only think is required if you are only thinking about circles.
The transfer you are talking about is just the WRONG TOOL. It is for changing radius when the problem is changing angle. To use an analogy you are taking a knife to a gunfight and holding it by the wrong end because you are using it the wrong way :)

drag in space now? News to me.

GRAVITY EXISTS!
Why do you think satellites eventually fall to earth? I suppose if you have ignore that it explains why you think things an overly simplistic approach is justified.

Re:Gravity!

[Pence128]

GRAVITY EXISTS!

Gravity =/= drag.

Why do you think satellites eventually fall to earth?

They don't. This reveals the true magnitude of your ignorance.

Didn't you notice the last two in the news?

[dbIII]

And you are the one calling me ignorant?
FFS - learn something about what you are writing about before pretending you know as much as you should have learnt at high school it you'd taken physics or any decent mathematics subjects.

Re:Didn't you notice the last two in the news?

[Pence128]

You mean this one?

Since that time, due to atmospheric drag, the satellite slowly lost height...