NASA has asked for companies to design a $1 billion space tug to crash the International Space Station back to Earth.
After initially considering using Russian spaceships for the task, the space agency has this month released a request for proposal from U.S. industry for the so-called U.S. Deorbit Vehicle (USDV), a spacecraft meant to safely deorbit the ISS as part of its planned retirement.
NASA explains: “The USDV is focused on the final deorbit activity. It will be a new spacecraft design or modification to an existing spacecraft that must function on its first flight and have sufficient redundancy and anomaly recovery capability to continue the critical deorbit burn.”
The call for designs was initiated on 20 September, with proposals due no later than 17 November.
In a March press conference, NASA Associate Administrator for Space Operations Kathy Lueders said the vehicle’s cost estimate “was a little short of about $1 billion”.
One initial plan had been to use multiple Russian Roscosmos Progress spacecraft to guide the space station home.
In 2001, Russia’s space station Mir was brought back to Earth using the thrusters of a small spacecraft, the Progress M1-5, to lower its orbit.
However, NASA now says: “These efforts now indicate a new spacecraft solution would provide more robust capabilities for responsible deorbit.
“To initiate development of this new spacecraft, NASA released the request for proposal.”
The Canadian Space Agency, the European Space Agency, the Japan Aerospace Exploration Agency, the National Aeronautics and Space Administration, and the State Space Corporation (“Roscosmos”) have operated the International Space Station since 1998.
Each is responsible for managing and controlling the hardware it provides.
The station was designed to be interdependent and relies on contributions from across the partnership to function.
The United States, Japan, Canada, and the participating countries of ESA (European Space Agency) have committed to operating the station through 2030, and Russia through at least 2028.
At the conclusion of the International Space Station program, the station will be deorbited in a controlled manner to avoid populated areas.
The safe deorbit of the International Space Station is a shared responsibility of all five space agencies through partner contributions based on mass percent ownership by the agency.
In the future, the United States plans to transition its operations in low Earth orbit to commercially owned and -operated platforms to ensure continued access and presence in space for research, technology development, and international collaboration.
“As with any development effort of this size, the USDV will take years to develop, test, and certify, ” NASA adds.
NASA explains how they will deorbit the International Space Station:
The primary objective during space station deorbit operations is the responsible re-entry of the space station’s structure into an unpopulated area in the ocean.
The chosen approach for safe decommissioning is a combination of natural orbital decay, intentionally lowering the altitude of the station likely using current propulsive elements, and then execution of a re-entry maneuver for final targeting and to control the debris footprint.
This final maneuver is expected to require a new or modified spacecraft using a large amount of propellant.
Due to the high propellant requirement of this final maneuver, the Earth’s natural atmospheric drag will be used as much as possible to lower the station’s altitude while setting up the deorbit.
Once all crew has safely returned to Earth, and after performing small maneuvers to line up the final target ground track and debris footprint over an uninhabited region of the ocean, space station operators will command a large re-entry burn, providing the final push to ensure safe atmospheric entry into the target footprint.
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