January 28, 2012, 7:15 AM — There's not a ton of oxygen in space. Because of this, we have to rethink how we go about doing the things that we take for granted here on Earth, like defense against an incoming missile. Back in 2007, China tested the first ASAT (Anti-Satellite missile) against one of it's own dead satellites; it was a resounding success.
Because of that, companies like the Raytheon Company has been working to give US space assets a figurative barrel roll defense.
One of the most common defenses against an incoming missile is a flare. Common aircraft use stuff like Magnesium-Viton-Teflon (MVT) flares to create a giant ball of light, heat and radiation that distracts incoming missiles and causes them to hit the flare and not the original target. The trick is to make the missile think it's hitting the target and not a decoy.
That's not so easy in space, where the raw material required to create an exothermic reaction are sparse. As is usually the case, science has the answer, and that answer is quantum dots.
What's a Quantum Dot, Anyway?
A quantum dot is a tiny little nanoparticle made of zinc, cadmium or some other semiconductor material. At such a small size, the quantum dots have some pretty unique electrical properties that you wouldn't see in a more sizable mass of their material; they give off light that the human eye can detect, for instance.
If that wasn't cool enough, the color of light they display depends on the size of the particle, making them tunable to whatever color the scientist wants. This is called the "size quantization effect". The dots can be tuned to give off infrared or ultraviolet light as well--light outside the visible spectrum.
Quantum Dots in Space
This brings us back to the defense aspect of this equation. Quantum dots can, based on this, be fine tuned to mimic the exact radiation signature of the space object they're trying to serve as a decoy for, making them incredibly effective as a flare.
The theory is to eject a cloud of quantum dots into space, via a spray from a storage tank or exploding a pack of dots suspended in inert gas. Those dots are fine-tuned to the spectral signature of the spacecraft they're protecting, and the missile hits the cloud instead of the craft.
That's the theory, anyway. You can see more at the Raytheon Company's patent application, which includes the full explanation including utilization of a ground-based tracking system to warn of a launched missile.