The SNOT Approach To Clearing Space Debris

On February 10, 2009, Russia’s spent Cosmos 2251 satellite collided with a smaller, but still sizable, Iridium 33 communications satellite (story). As could be expected from a high-speed impact between two large but relatively fragile devices, smithereens ensued. While the large pieces are annoying, they can be tracked fairly easily and so anything in their way can be moved for safety when necessary. It’s the small stuff, and especially the very small stuff, that is the most worrisome. With the total number of objects both large and small in Earth orbit increasing by the year, the chances of more collisions is constantly on the rise. It is long past the time that we need to deal with the problem.

Many of the ideas that get tossed around just aren’t practical. For instance, magnets are all but useless since very little iron is actually to be found in spacecraft. Nets don’t take into account the amount of inertia that such a device will encounter whenever it actually catches something—nevermind the varying orbital velocity of the net from top to bottom that will tend to make it rotate. Lasers aren’t a bad idea, pulses of light being used not to vaporize junk in a science fiction sort of way, but simply slow them down so that they enter a lower (more fiery) orbit. The trouble with lasers is expense, power, and target acquisition and lock.

I think the best plan is to start with something low-tech: snot. Yes, that incredibly sticky nasal substance that is seemingly impossible to remove without finding something expendable to make it stick to so that it can be removed. Of course we’d have need of a high-tech version of this substance which would get some cute acronym like Surface-based Neutralizer of Orbital Trash (SNOT).

This substance would need to exhibit strong adhesive qualities in the extreme temperatures, microgravity, and near-vacuum found in the range of useful Earth orbits. If it also had a self-healing toughness to allow it to capture reasonably small particles traveling at high speed, so much the better.

I envision SNOT to be deployed on a micro-satellite basis piggy-backed on other launches, or it can be scatter-shot en masse with dedicated rockets. The typical SNOT will be very basic: a blob of the adhesive (expanded like a blown piece of bubble-gum would be a great option, but not required) attached to a de-orbiting tether. The tether provides a passive way for the SNOT to deorbit with whatever got stuck to it. Obviously, more debris can be cleared with larger surface areas of SNOT, but launch mass and the physical properties of SNOT clearly must be taken into account.

Using this purely passive method, SNOT should be able to clear debris in a decreasingly logarithmic fashion. With large debris fields, swaths can be de-orbited in short order, but as this occurs the field will become increasingly diffuse, the result being that incidental impacts with SNOT become less frequent. Again, this can be compensated for by increasing surface area, but only to a point. Still, the micro-satellite approach allows for the low-cost SNOT to be deployed continuously with the result that the orbital debris field can kept to a tolerable density.

For larger pieces of debris, SNOT alone might be enough to force quicker de-orbits simply by virtue of the tether. Still, in some cases that might not be sufficient. Remotely guidable de-orbiting rockets might have to be sent to take care of large orbiting carcasses. A problem in the past has been how to dock or otherwise interface with these derelicts. My suggestion: SNOT. Use it’s properties to maximum advantage. Combined with the remote rockets and a judicious amount of debris-mitigating thin-film SNOT around the debris to protect for unexpected fragility, there isn’t a huge technological hurdle that needs to be overcome so that dead satellites and boosters can be safely removed from long-lived nuisance orbits.

Much of the “trash” that is in orbit is relatively low mass (<50g) and of small size (<50mm). These include paint chips, nuts, bolts, glass and metal shards, mylar, and a host of other inevitable flotsam that would fill the sky even if every launch was uneventful and every spacecraft remained intact. Unfortunately, with catastrophic explosions, collisions, military tests, and possibly orbit-mining during times of war, the need to clear space of the small stuff is not only a constant need, but a growing one.

While it would be really cool to develop technology that could deploy nano-satellites to seek out and grab every piece of junk and return with it to a mothership, that’s not too practical or terribly efficient. For our current needs, using a lot of SNOT as a sort of cosmic pet-hair brush could provide the most effective solution. Plus, if you really want a cool factor, imagine some news anchor having to tell eir[[daggerto]] audience that, “NASA deployed their newest multi-billion-dollar satellite, and along with it, sixty pieces of SNOT.” OK, so not gee-whiz cool, but it’s made-you-say-it cool.