junk in orbit around the Earth is becoming a bigger problem every year. Space agencies are tracking some 7,000 tons of debris, adding up to more than 20,000 pieces larger than 10 centimeters. European space agencies and private companies, in a joint effort called RemoveDebris, plan to test a variety of different possible solutions next month with a satellite launched aboard a SpaceX rocket to the International Space Station.
“The problem with so much junk up there now is it is actually starting to prove a real issue, and the chance of collisions is increasing all the time,” Jason Forshaw of RemoveDebris told The Guardian.
One of the most intriguing efforts is spearheaded by Airbus, and its target is the biggest hunk of junk in orbit — Envisat, the largest Earth observation satellite ever launched, weighing more than eight tons. The company wants to corral the floating behemoth with a giant space harpoon, and then drag it down into the atmosphere, where it will burn up on reentry.
According to the BBC, the harpoon is currently being developed in England, and a small prototype will be tested during next month’s RemoveDebris mission. “If we can design a harpoon that can cope with Envisat, then it should be able to cope with all other types of spacecraft including the many rocket upper-stages that remain in orbit,” said project engineer Alastair Wayman.
Envisat, launched in 2002, was a state-of-the-art observation platform bristling with instrumentation including imaging radar, spectrometers, and atmospheric sensors. The European Space Agency (ESA) unexpectedly lost contact with the satellite in 2012. Despite numerous attempts to resurrect it, the mission was declared officially dead shortly thereafter.
The relative simplicity of the harpoon is what appeals to engineers. “Many of these targets will be tumbling and if you were to use a robotic arm, say, that involves a lot of quite complex motions to follow your target,” Wayman explained. “Whereas, with the harpoon, all you have to do is sit a distance away, wait for the target to rotate underneath you, and at the right moment fire your harpoon.”
Envisat is the long-term goal of the space harpoon project — its great white whale, as it were — but test missions in the next few years will focus on smaller targets. April’s RemoveDebris demo mission will release a small target from the satellite and then attempt to retrieve it using the harpoon.
The harpoon that Airbus plans to use for Envisat is about three feet long, and it’s fired with a burst of compressed air. Barbs will pop out and lock it into place after penetrating the skin of the rogue spacecraft, which is a little more than an inch thick.
“The harpoon goes through these panels like a hot knife through butter,” said Wayman.