7 ideas to solve the space junk problem
— By Tyler Falk on January 14, 2014, 3:43 PM PST
1. Lasers don't slow junk down. They might melt it, evaporate (this would be good) it, or more likely break the object into more pieces, complicating the problem.
2. Large area nets are not so much impossible, as they are impractical. Large spinning (centrifugal force is used for deployment, like a fisherman casting a net) is a terrific anti-missile weapon (in theory anyway). You can cover a large area with nets, simply by using multiple nets, as large as technically possible, simply by overlapping their areas, with some separation between the nets, so they don't bang into each other. The problem with nets for debris capture is even if you can get the orbital plane correct and the speed of the net, close to that of the objects you wish to capture, when the object finally hits the net, it will distort/pucker at the point of impact. With each successive collision, the area and thus the efficiency of the net decreases.
3. The answer for large objects such as satellites and rocket boosters is another vehicle (manned or unmanned) to merge with the object and attach something, which will either take it away (solar sails), or slow it down (parachute if it's low enough or retro-rockets) so it will fall back to earth.
4. As for capturing small objects moving at tremendous speed, the answer is FOAM. It's not foam until after or as part of deployment. My best guess would be Kevlar. Kevlar foam is part of the design of space craft proposed for missions to Mars to protect the space craft and inhabitants against high velocity impacts. The beauty of a foam target, regardless of size and/or shape is that you don't have to accelerate it to the speed of the objects you wish to capture. You need only have the ability to place the target in harms way in the correct orbital plane. The debris' velocity and mass will do the rest. As the mass of the foam increases with collisions, it may reach a level where it's gravity is sufficient to attract and capture nearby pieces of debris.
If the foam target becomes a nuisance, the rocket motors used to move it into the path of debris can be used to slow its orbit sufficiently for it to return to earth, burning up in the atmosphere.
For the near Earth space debris, launch rockets that release clouds of ionized particles in the paths of the offending items. We don't have to capture the junk, we just need to slow it down so that it falls back into the atmosphere. We could put linear engines on new satellites themselves, so they can accelerate or decelerate as they pass thru the ion clouds. Old junk would just decelerate from the friction and from the accretion of mass that is not actually in orbit.
To make this (and other space launches) less expensive, we need cheap hydrogen balloons to take the rockets to 60,000+ feet before they ignite. This would make a rocket launch much much less expensive. Hydrogen balloons are much cheaper and more efficient than helium balloons, and could be made safe enough for temporary use.
Today's rockets use most of their energy and mass to get out of the thick lower atmosphere. We had to design them that way in the 1950s and 60s because we did not have the computing power to compute the orbits on the rocket itself. Now that's trivial, especially with GPS available.
I agree that lasers are an ideal solution for garbage collection, but the aiming problem will be difficult if the "garbage collection" spacecraft is moving at high velocity relative to the offending debris. Not as difficult as using a net, but still hard.
Most of the proposed technology addresses whole appliances. As stated above, at least one third of the debris is in very small pieces - too small for retrieval by anything other than something like a net.
Unfortunately, to be effective for anything other than a whole satellite, the net would have to be enormous - beyond current technology, on account of how far apart the debris pieces are now.
These tiny pieces are also the hardest to track, but they are none too small to cause catastrophic damage to an operating craft.
It's not a good thing, and there should have been more international outrage than there was when the Chinese intentionally added thousands of pieces of debris to the cloud.
What the Chinese did was unforgivable. A virtual act of "space war". The first of its kind.
I don't think launching more hardware is the solution. As has already been mentioned here, deploying nets or similar solutions is questionable simply because most objects in orbit are not all in the same orbit, meaning that they differ in speeds by as much as tens-of-thousands of miles per hour. There are no space-worthy light-weight (meaning launchable) materials available that can survive those kinds of impacts intact without just creating even more debris, and contributing to the "cascade" problem.
I personally favor the laser approach, either ground, air or space-based. It's relatively low cost. Targetable objects can be nudged into orbits that would more rapidly decay, resulting in the disintegration in the atmosphere.
One of the problems with the junk is that it is in orbit, along with good satellites. So "sweeping" an area with nets is unlikely to be effective, since the net and the junk are traveling at the same speed. Putting the net into a retrograde orbit means the speed differential becomes so huge that the junk will break the net. Better would be to use a laser or something else to slow the junk down, so it falls back into the atmosphere.
Paint, Copper, Aluminum, Titanium, Plastic, etc. are not magnetic. Thus, this attribute of the giant flying magnet and or space net, won't work.
In addition, any object used to sweep near space clean of debris, will have to attain speeds and plane of orbit matching and/or overtaking the objects you wish to catch in order to avoid a catastrophic collision, which will simply add more space junk to the inventory.
By the way, you can't land on the sun.
@theotherwill The problem here can be reduced to one term: "Delta-V," which is the amount of energy required (and accumulated) to put a satellite into orbit. In order to retrieve a satellite (or anything else in orbit), a means to subtract that energy is necessary. In short, it takes as much energy and launch resources, to de-orbit as it takes to put it into orbit.
All the nets, etc. that we wish to put there to sweep the junk require a lot of rocket power, which is expensive.
@omb00900 That's hyperbole. "Space war" would be appropriate if the Chinese weapons damaged a foreign satellite or rendered unusable an orbital path that another country wanted to use. "Criminal vandalism" with financial & diplomatic punishments would be more appropriate.
@Starman35 In order for this to work, the laser would need the following in order to slow something down enough to let gravity do the rest.
1. Line of sight access, outside earth's atmosphere, above or in front of the target in order to vaporize the target's material in such a way as to have the vapor propel the object earthward or simply slow it's orbit.
2. A suitable target. It won't work for thread (fiber glass, etc.) or paint chips unless you can completely vaporize the objects.
3. Some means (absent earth's atmosphere) of dispersing the target's vapor so that it does not interfere with the laser light's ability to continue hitting the target. A steady laser beam won't work. This deficiency in laser anti-missile technology was discovered years ago during tests in earth's atmosphere. It was discovered that the vapor given off by burning targets created a shadow (smoke cloud), which the laser could not penetrate, so they had to pulse the laser, giving the target's movement through earth's atmosphere a chance to fly clear of the smoke screen and be hit by the next pulse. If you could do this enough times, the surface of the target became sufficiently compromised that it caused air turbulence, sufficient for the target to disintegrate. No such luck in space. The technology is so inefficient that you might as well launch a million old fashioned street sweepers, a la Rocky and Bullwinkle into space and have them sweep up all the crap.
@theotherwill@omb00900OK, I'll go with "criminal vandalism", but you might be splitting hairs. I wonder how many wars have been started over an act of criminal vandalism?
It was purely a political act, and there were no repercussions, which was my real point.