NASA's final plans for the International Space Station when it is decommissioned at the end of the decade have been revealed as it asks for proposals for a new spacecraft that will be used to guide the station to burn up in the Earth's atmosphere.
According to current policy, NASA and most of its international partners intend to operate the ISS until 2030, by which time its basic structure will become too fatigued to continue to host astronauts safely. The problem is, how to dispose of the 100-tonne structure safely?
Pushing it into a higher orbit isn't feasible because of the enormous amounts of energy required to do so and the stresses that would be placed on the spacecraft that could cause it to break apart. The alternative is to carry out a controlled descent into the atmosphere where it will burn up and any surviving debris will fall into an uninhabited ocean region.
The original idea was to use a series of Russian robotic Progress cargo ships to push the ISS into the desired orbit, but a year-long study by NASA and the ISS partners showed that the Progress option wouldn't work as desired. Unspoken by NASA is also the fact that Russia is scheduled to leave the station in 2028 and deteriorating relations between Russia and the other partners make the previous plan less than reliable.
As an alternative, NASA has put out a proposal to American companies to develop a United States Deorbit Vehicle (USDV) that will be used for the final deorbit phase after the station naturally descends in altitude as its orbit decays. The new craft will be either a modification of an existing one or a completely new design. Competitors are being offered a firm fixed price of cost plus initiative agreement to cover design, development, testing, and evaluation, followed by actual construction and deployment. Because the spacecraft has only one chance to complete its mission, NASA expects it to include a heavy dose of redundancy in its systems.
Source: NASA
