typodupeerror

## Giant Balloons Could Solve Space Junk Problem210

Posted by samzenpus
from the giant-balloon-animals-soon-to-come dept.
An anonymous reader writes "More than 100,000 objects bigger than a centimeter wide hover around our planet, accounting for 4 million pounds of junk that befouls our atmosphere and threatens the expensive satellites we actually want in orbit. Dr. Kristen Gates, of Global Aerospace Corporation, proposes that we can clear the skies by attaching a football field-sized balloon to dead satellites, which would increase the orbital drag, eventually bringing a satellite down into the atmosphere where it would burn up. The GOLD — or Gossamer Orbit Lowering Device — unit is easily inflated in space, and best of all, if the deployed GOLD balloon collides with space junk, it won't deflate or break the junk into smaller, less manageable bits."
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## Giant Balloons Could Solve Space Junk Problem

• #### Collision course (Score:1, Informative)

on Wednesday August 04, 2010 @05:57PM (#33144880)
The question isn't just whether it can collide with and bring down space junk, but whether it can avoid legitimate satellites as well. I guess if anyone has any secret spy satellites floating around they better speak up or lose them to an uncoordinated balloon collision : ).
• #### Re:And all you need to do is catch up to the debri (Score:2, Informative)

by Anonymous Coward on Wednesday August 04, 2010 @06:03PM (#33144936)

Naturally the slashdot headline is wrong. They're talking about attaching it to entirely intact satellites to get them to de-orbit without hitting something and making more debris. (as seen from the URL of the story linked: "_Without_Making_The_Problem_Worse"

In other words, you just have to catch up to the satellites.

• #### Re:Collision course (Score:3, Informative)

on Wednesday August 04, 2010 @06:22PM (#33145134) Homepage
Actually most spacecraft (including "secret" government satellites) are tracked by both governments and private entities. Since the last collision the US Air Force has actually started expanding their capability for this even more. They are very open to working with other parties to solve space debris issues and avoid collisions with their satellites or between other satellites.
• #### Re:Collision course (Score:3, Informative)

on Wednesday August 04, 2010 @06:24PM (#33145150) Homepage

It doesn't sound like it's meant to bring down some random spacejunk with which it collides (which would mostly pass through it after all, at best / if impacts won't produce more debris), just to bring down a satellite to which it is attached. Not the only effort of such kind [surrey.ac.uk]

• #### Re:Weird.... (Score:2, Informative)

on Wednesday August 04, 2010 @06:37PM (#33145296) Homepage
That's all fine and good if you have great attitude (direction) control of your spacecraft. If you lose your gyros or something during the lifetime of the spacecraft, then you wouldn't be able to control an Ikaros like sail. Having a spherical balloon that doesn't care about direction and can inflate with minimal mechanical effort seems a lot more reliable.
• #### Got her name wrong (Score:3, Informative)

on Wednesday August 04, 2010 @06:41PM (#33145330)
It's Dr. Kristin Gates [gaerospace.com]. At least try to get the basic facts right.
• #### Re:Why not collect it in space? (Score:2, Informative)

on Wednesday August 04, 2010 @06:53PM (#33145406)

1. Launch costs will have to come down by a hefty factor before it becomes economic to launch entire factories and bring raw materials from far away. Once launch costs have come down that far (and I'm not holding my breath), the value of the raw materials that are in orbit today will seem slight. Meanwhile, even one more collision between derelict satellites will make the orbital environment more dangerous and harder to clean up.

2. The raw materials that are in orbit today are in a wide variety of orbits, by both altitude and inclination. If your factory is in equatorial orbit, the delta-V needed to collect a given mass from a polar or near-polar orbit (which spysats tend to use) is more than the delta-V needed to launch it from Earth, and far more than the delta-V needed to launch it from an asteroid etc.

• #### Re:Weird.... (Score:2, Informative)

on Wednesday August 04, 2010 @07:02PM (#33145468) Homepage Journal
If you've lost control of your spacecraft before it begins it's deorbit maneuver, chances are any system you put on there is going to have a hell of a hard time getting it to deorbit appropriately. Even if you start to inflate this giant spherical balloon after you've lost the ability to point your spacecraft, due to loss of reaction wheels or some other such thing, you are going to be trying to deploy a very large moment arm in an unpredictable/unknowable dynamic scenario (in other words, your rates and attitude will be completely unknown). This is going to inflict some pretty heavy structural loads on your spacecraft, primarily where the deployment system connects to the bus. As such, if you are trying to deploy this giant balloon in anything but the designed for performance envelope, you run the very real risk of tearing the deployment mechanism, and, hence, balloon from the bus, or failing catastrophically in some other manner, which would be completely counter-productive to your attempt to deorbit in the first place.

In short, deploying something this large is not something you just get to do no matter how your spacecraft is behaving. Like any other deorbit scenario, this balloon is going to have a performance criterion requirement that it must be designed for: "At end of mission you must be able to control your spacecraft within X, Y, and Z parameters in order to ensure successful deployment of giant balloon." You will have a similar mission requirement for any other deorbit profile, including a large sail. Now, I will give that those mission requirements might be a bit more lenient for the giant balloon (and I stress might), but I would much rather see a comprehensive trade study that sheds some light on whether or not this theoretical relaxation of mission requirements buys you any performance, fuel-margin, or mass throughout your mission. And I would want to see them compared against the increased complexity of using a balloon deployment as opposed to a tether or sail deployment.

Don't get me wrong, if the fella in the article has done such studies and shown that it will likely increase mission performance, then whether or not I think this is weird, we will see a giant balloon flying on a mission eventually. However, right now this seems like an interesting concept that doesn't seem like it would bring a whole lot to any given mission to me. This speculation is based off little more than my own personal knowledge of deorbiting spacecraft, which is part of the mission analysis that I do for a living.
• #### Re:Why not collect it in space? (Score:5, Informative)

on Wednesday August 04, 2010 @08:09PM (#33145946) Homepage

Ok, you've grappled the object. Where do you want to send it?

Sending it down requires a drag chute of some kind. Or it requires just enough delta-v to drop its perigee just a little lower into the atmosphere.

Suppose we had the mother of all factories sitting in equatorial orbit. Suppose your space junk is in a 35 degree orbit. Both objects are traveling at around 27Kkm/h if they're in a relatively low orbit. However, one object is moving 27Kkm/h due east, and one is moving 27Kkm/h 35 degrees north of east. Relative to each other they are moving at thousands of kilometers per hour when they pass each other. To collect the object you need to apply that much of a velocity change to it, which is a huge amount of energy (not quite what it took to launch, but we're getting into that kind of magnitude).

Think of it this way - you're on a racetrack going 200mph. Another car is going 200mph the other way. You want to collect it. How do you do this without massively changing its velocity?

One of the first rules of orbital mechanics is that plane changes are expensive. That's why the shuttle can't visit the ISS and the hubble on the same mission. They're both in similar altitude orbits, but in different planes. The shuttle doesn't have enough fuel to change planes (at least, not that far - and without looking up the numbers that is probably only 10 degrees or so).

• #### Re:How can it increase drag when there's no air? (Score:2, Informative)

on Wednesday August 04, 2010 @08:44PM (#33146164)
The equation for drag is force = 1/2 * speed^2 * density of atmosphere * area * drag coefficient. At orbital speeds, speed^2 is very large, so even a low density will produce significant drag. Also, the football-field-sized balloon has a very high cross-sectional area in relation to its mass, and even the mass of it plus the satellite, so the force produced will be still more capable of de-orbiting the satellite.
• #### Re:pop! (Score:4, Informative)

on Wednesday August 04, 2010 @10:03PM (#33146504)

There are no astronauts, there are no robots, there is nothing extra being launched into orbit to intercept existing satellites. This is a small, couple kilogram, briefcase sized package that will be attached to new satellites at launch, so at the end of their life, the balloon will be deployed, and the satellite will de-orbit in a matter of weeks.

They should have designed these satellites to be self-killing - i.e. Burn a rocket, deorbit, and burn rather than just throw stuff all over the place & forget about it.

Satellites generally are designed to be self killing. All satellites have some sort of moderate delta-v rocket meant for station keeping and orbital maintenance. A significant amount of the fuel for this rocket is held in reserve, in order to de-orbit the satellite at the end of its life. Geosynchronous and other high orbit satellites cannot afford to re-enter, so instead they rise up to a 'graveyard' orbit, in order to keep the useful orbits clean. The purpose of this balloon is to replace the reserve fuel for low earth satellites. It is significantly lighter than the required fuel, so it will allow a higher payload fraction for the satellite.

• #### Re:Does it mass more than the fuel to de-orbit? (Score:3, Informative)

on Wednesday August 04, 2010 @10:42PM (#33146704)

It's pretty pathetic that despite 50 years of space experience, we still have to worry about mere grams of fuel. I suspect humans will never develop the ability to travel further than our own solar system - it would be too expensive (in terms of fuel).

Travel in space is simple. Ion drives and other forms of electric propulsion have the potential for incredible velocities. Gravitation sling-shotting gives you plenty more velocity for free. The problem is that first 9km/s needed for low earth orbit. You have atmospheric drag to contend with, so you need to get out of the atmosphere as soon as possible.

Consider one of the space shuttle SRBs for example. At full throttle, each is pumping out some 5400kg/s at 2450m/s. That's roughly 16GW, or several times the power output of a large power plant. The only means we have of generating that kind of power is chemical or nuclear, and the general public doesn't much like nuclear powered rockets.

1000 years from now we'll be in pathetic shape, with all our oil, uranium, and other resources drained dry, and just barely surviving.

I'm not sure where you pulled that value from. We've got enough uranium to power us for a hundred thousand years, and enough thorium to run several times beyond that.

• #### Re:Solves the wrong problem (Score:3, Informative)

on Wednesday August 04, 2010 @11:42PM (#33146958) Homepage

If the big stuff stays up there, it has a tendency to get hit by the small stuff, which turns the big stuff into more clouds of little stuff. Above a certain density of stuff in orbit, this can lead to a rapid chain reaction that leaves LEO rather inhospitable. Better to de-orbit the big stuff as soon as it's no longer useful.

• #### Re:Solves the wrong problem (Score:3, Informative)

on Thursday August 05, 2010 @08:36AM (#33149218) Homepage
Also, the big stuff (many of which are rocket stages with some fuel left in them) sometimes explodes: http://www.newscientist.com/article/dn10979 [newscientist.com]

If we can deorbit even one *before* it explodes, we can cut the number of space debris by hundreds or thousands.

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