Russia has announced  it will be investing $2 billion in a program to capture some of the thousands of pieces of dangerous debris that threaten the future of space technology. How might it work?
Energia, Russia's space corporation, has revealed plans  to build a special space "pod" which will grab around 600 defunct satellites and then safely deorbit them so that they either burn up in the atmosphere or splash down into the ocean. The pod will rely on a nuclear power core, and cost around $2 billion to develop and deploy. Energia plans to complete design and testing by 2020 and have it in service no later than 2023, with an operational lifespan of around 15 years. The company also said it has been working on a space interceptor capable of tackling any dangerous objects from the outer solar system that may be on a collision course with Earth.
If it seems odd to think of Russia as Earth's space junk and comet defender, it's also welcome news. Space debris in the form of defunct or malfunctioning satellites is an increasingly severe  problem. Numerous orbits are becoming inaccessible, or at least hopelessly dangerous, because of wandering hulls or showers of shredded metal debris--like the one caused by a collision between  a working U.S. Iridium satellite and a dead Russian Cosmos satellite in 2009.
How might the system operate? Energia hasn't offered much in the way of details, but its long mission life span and nuclear power source point to its drive tech. Radio thermal space waves can generate electricity over a long time, making it an ideal power source for ion drives (which use electric fields to accelerate ionized gas, rather than the typical chemical rockets). The pod's stated targets, dead satellites, also suggests it won't use an exotic  form  of debris capture, like a space net. Instead it's more likely to power its way up to a dead satellite in or near its main orbit, and then use the ion drive to gently push the spent vehicle into a decaying orbit that'll end with a burn-up.
Similar technology could be used in the "interceptor" spacecraft, only on a bigger scale. If you can identify and encounter an incoming threatening comet in time, you may only need to deviate its trajectory by a tiny amount so that it misses Earth rather than hits it.
Of course, the technology for both a debris pod and comet interceptor would also make those particular spacecraft very potent anti-satellite weapons in a hypothetical space war. But we're probably better off not thinking too much about that.
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