Envisat is a dead 8,100 pound satellite that scientists now say is at high risk of triggering a catastrophic cloud of cascading space junk similar to the one portrayed in Gravity.
At 30 feet (9 meters) long, Envisat is the largest civilian observation satellite currently in space. Unfortunately, it died on April 8, 2012 — so it's just spinning aimlessly around the Earth at a height of 490 miles (790 km). It's not expected to re-enter Earth's atmosphere for another 150 years.
Because of its large size and the altitude at which it orbits, fourth-year students at the University of Leicester's Department of Physics and Astronomy fear that it's at high risk of colliding with other satellites and debris. This would unleash the dreaded Kessler Syndrome — an avalanche effect instigated by cascading bits of debris.
It would be like the one portrayed in Gravity. In that case, a Russian rocket started the whole thing by knocking out one of its own satellites. But in this proposed instance, the Leicester students worry that Envisat could smash into another satellite or other bits of space junk. And as we all know from Gravity, the outcome would be awful. In fact, failure to prevent such a thing could result in our having to "reboot" low Earth orbit by clearing it of all satellites and debris — and then starting from scratch.
To date, Envisat has had two objects pass within 200 meters of it, while one spacecraft has already been forced to move out of its path.
To deal with it, the Leicester physicists have proposed a de-orbiting plan: "If Envisat could be slowed down, it would be possible for it to enter an orbit with a lower altitude and natural forces, such as drag, would bring it back into Earth's atmosphere,"
The scientists calculate that the satellite would need to be moved to an altitude of 435 miles (700km) from its current position in order to return to the planet in 25 years. They say it may be possible to use NASA's Robotic Refueling Mission (RRM), which was specifically designed to refuel and repair non-operational satellites. However, it is still in its earliest phases of testing.
You can read the entire paper at the Journal of Physics Special Topics, a special journal where students "are encouraged to be imaginative with their topics, and find ways to apply basic physics to the weird, the wonderful and the everyday." Previous entries to this journal include a visualization of hyperspeed and the impracticality of human teleportation.