NASA's final plans for when the International Space Station is retired at the end of this decade have been revealed, with the agency asking for proposals for new spacecraft to guide the ISS as it burns through Earth's atmosphere. Under current policy, NASA and most of its international partners intend to operate the International Space Station until 2030, when its basic structure will become too fatigued to continue to safely host astronauts.
The question is, how to safely handle this 100-ton structure?
Pushing it into a higher orbit is not feasible because doing so would require enormous amounts of energy and would stress the spacecraft, causing it to break apart. Another option would be a controlled descent into the atmosphere, where it would burn up and any surviving debris would fall into uninhabited areas of the ocean.
The original idea was to use a series of Russian Progress robotic cargo ships to push the International Space Station into a desired orbit, but a year-long study by NASA and ISS partners showed that the Progress plan was not going to work. Another fact that NASA has not disclosed is that Russia plans to leave the International Space Station in 2028, and deteriorating relations between Russia and other partners have made previous plans less reliable.
As an alternative, NASA has proposed to American companies the development of the United States Deorbit Vehicle (USDV), which would be used in the final deorbiting phase of the space station's natural descent after the orbit decays. New aircraft are either modifications of existing aircraft or entirely new designs. The competitor's offer was a fixed cost plus initiative agreement that included design, development, testing and evaluation, followed by actual construction and deployment. Since the spacecraft only has one chance to complete its mission, NASA wants to include a lot of redundancy in its systems.
Since 1998, five space agencies (Canadian Space Agency, European Space Agency, Japan Aerospace Exploration Agency, NASA and national space company "Roscosmos") have operated the International Space Station, with each agency responsible for the management and control of the hardware it provides. The space station is designed to be interdependent, operating on contributions from the entire partnership. Participating countries including the United States, Japan, Canada and the European Space Agency (ESA) have pledged to operate the space station until 2030, and Russia has pledged to operate it until at least 2028.
At the end of the International Space Station program, the space station will be deorbited in a controlled manner to avoid densely populated areas. The safe deorbiting of the International Space Station is a shared responsibility among all five space agencies and is funded by partners based on the percentage of mass owned by each agency. Going forward, the United States plans to transition its operations in low Earth orbit to commercially owned and operated platforms to ensure continued access to and presence in space for research, technology development, and international cooperation.
In a years-long effort, NASA and its partners studied deorbiting requirements and previously developed an initial strategy and action plan that evaluated the use of multiple Roscosmos Progress spacecraft to support deorbiting operations. These efforts now demonstrate that new spacecraft solutions will provide greater capabilities for responsible deorbiting. To kick off the development of this new spacecraft, NASA issued a request for proposals.
USDV focuses on the last derailment activity. It will be a new spacecraft design or modification of an existing spacecraft that must function on its first flight and have sufficient redundancy and exception resilience to continue the critical deorbit burn. As with any development effort of this scale, the development, testing and certification of USDV will take several years.