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...