Out-of-control giant satellite poses “Gravity”-style space debris threat

The students calculated that the energy required to move the satellite 90 km closer to the Earth was 2.7 billion joules — equivalent to an extra 143.1 kg of hydrazine fuel. This could be quite feasible, according to the students, if two of the craft’s 80 kg fuel tanks were replaced.

Actually, however, getting this fuel to the satellite in orbit would be a pretty tall order due to the costs involved of such a mission — which has never been attempted for a satellite which was not designed to be refueled.

An average satellite launch costs hundreds of millions of dollars — with each kilogram of the satellite’s costing tens of thousands of dollars.

“In the film, the cloud of space debris is caused by a missile which was supposed to destroy a non-operational satellite and sparks the chain reaction which eventually collides with Clooney and Bullock’s spacecraft. In real life this is very unlikely to happen,” said physics student Katie Raymer, 22, from Whitstable.

“It is even more unlikely that ESA’s Envisat could cause one of these chain reactions. However, each year two objects are expected to pass Envisat to within about 200 meters and other spacecraft have had to manoeuver themselves out of Envisat’s path. Also Envisat orbits at an altitude where the amount of debris is greatest. So although it is unlikely to happen, de-orbiting Envisat is certainly worth considering.

“Unfortunately, it would be very unlikely we could move Envisat to the right altitude due to how much it would cost. Envisat was not designed to be refueled, so another method of de-orbiting Envisat may be a better option.”

The students suggest it may be possible to use NASA’s Robotic Refueling Mission (RRM) which has been designed to refuel and repair non-operational satellites, but is still in its earliest stages of testing.

Professor George Fraser, director of the University’s Space Research Center, commented: “The Special Projects paper highlights the huge area and mass of Envisat as the major risk factors for space debris. The fact that Envisat is in a near-polar orbit doesn’t help either, since its path intersects most satellites’ orbits nearly at right angles. Imagine driving down the motorway and every so often a large truck cuts right across all four lanes right in front of you!”

The release notes that the team stressed that the calculations used in the paper should be taken as an estimate, as a full treatment would be very complicated and beyond the scope of a Journal of Physics Special Topics paper.

The Journal of Physics Special Topics is published every year, and features original short papers written by students in the final year of their four-year Master’s of Physics degree.

Course tutor Dr. Mervyn Roy, a lecturer in the University of Leicester’s Department of Physics and Astronomy, said: “The aim of the module is for the students to learn about peer review and scientific publishing. The students are encouraged to be imaginative with their topics, and find ways to apply basic physics to the weird, the wonderful and the everyday.”

— Read more in K. Raymer et al., “P2_1 Deorbiting Envisat,” Journal of Physics Special Topics (9 October 2013)