Up there with invisibility, teleportation, and being able to cancel mid-season TV breaks, x-ray vision is one of the most sought after superpowers. In the mind’s eye, the ability to see through clothes has a veritable smorgasbord of litigious applications — but in the real world, especially in a military context, being able to see through walls would give soldiers an immense advantage… And that’s exactly what the MIT Lincoln Laboratory has managed to do.

It isn’t quite x-ray vision — it uses microwaves instead — but MIT’s radar array, made by Gregory Charvat and John Peabody, can see through 8-inch concrete walls (video demo below). Basically, it works just like a normal radar system: 44 antennae send out S-band microwaves (2-4GHz, about 10cm peak to peak). Most of these microwaves — 99.4% — bounce off the solid concrete wall. The 0.6% that make it through bounce off any objects on the other side, and then come back through the wall, losing another 99.4% of the waves. By the time the microwaves return to the array, the signal is just 0.0025% of its original strength.

So far so good — and now it’s time for the novel bit. The reflected waves are amplified and then passed through an analog crystal filter, which removes the waves that were reflected by the wall, leaving just the data left by whatever’s on the other side. This data is then analyzed by a “gaming computer” (bottom right in the image above) to create colored blobs on a screen; one red blob per moving target, and it can only track moving targets — but the researchers say this is OK because even the steadiest combatants can’t stay stiller than a concrete wall. All of this occurs in real-time, incidentally, and the blobs move around at 10 frames per second.

If you’re an armchair physicist, you’re probably wondering ‘why microwaves?’ Longer radio waves penetrate walls much better — that’s why television and radio signals can traverse hundreds of miles, while your WiFi router has all the power of a walnut — but they also require a much larger transmitter and receiver. Charvat and Peabody wanted something that could actually be used in warfare, and at 8 feet wide their creation could be mounted on the back of an army Hummer.

Anyway, with a working seeing-through-walls device, the researchers are now working on the output imagery: instead of blobs, they want each moving target to be represented by a cross. The MIT press release also points out that the same technology could be used by emergency response teams, to see through rubble and collapsed structures for survivors. For the most part, though, at least according to Charvat, the radar array is all about more efficient killing: “This is meant for the urban war fighter … those situations where it’s very stressful and it’d be great to know what’s behind that wall.”

Read more at MIT