Computer generated image of the current Earth orbit debris being tracked. It shows only 95% of oribiting garbage. (via NASA Orbital Debris Program Office)
More elaborate efforts are being made to clean up space in order to allow future space exploration and decrease the risk of catastrophic collisions. Most methods involve rockets to send up other devices with nets, harpoons and even lasers to undermine the orbits of space trash, but Boeing of Chicago is suggesting a relatively simpler approach involving a single rocket to make trips up and bring down obsolete space trash by spraying them with cold and heavy inert gases.
Boeing filled a US patent application in September that details plans for a rocket to make cleaning trips to space. The gas rockets method for cleaning space junk would start by positioning itself above the target(s) around 100 km from earth. Then it would spray up to 10 tonnes of cryogenic gases at a contrary trajectory to the orbiting junk. According to the patent author, Michael Dunn, the gas cloud would disperse in seconds but its initial density would be enough to slow down the debris enough for them to fall out of orbit and back to Earth.
The gas cloud itself would be composed of a cryogenic noble gas like krypton or xenon or a mix of high-atomic weight elements, such as titanium, zirconium or depleted uranium, and halogens. It is estimated that the clouds would be between 50 km to 500 km in size and have a mass of 1,000 kg to 10,000 kg. This cloud would be emitted from specialized nozzles, positioned 180 degrees apart on the rocket that perform Prandtl-Meyer expansion of the gas.
Boeing hypothesizes that collision between clouds of this cold heavy gas and obsolete equipment would slow down junk from the usual speed of 7.8 km/s to 7.6 km/s. A deceleration of 0.2km/s that is enough to decay its orbit and send it to its fiery death as it re-enters the atmosphere.
This type of “janitor” rocket would mean that no extra equipment is needed in transporting the machine into space and thus lessening the chance for leaving more debris in orbit. The rocket would be capable of positioning itself at 100 km up, spraying its contents and fulfill its duties before returning to Earth to reload. Whether multiple lift-offs is more environmentally beneficial versus just leaving the junk, is yet to be discussed. The idea still only lives in the papers of a patent, but soon enough these space cleaners will come to life.
Cabe