Space Logistics - Downmass

Downmass

While significant focus of space logistics is on upmass, or payload mass carried up to orbit from Earth, space station operations also have significant downmass requirements. returning cargo from low-Earth orbit to Earth, or transporting downmass, the total logistics payload mass that is returned from space to the surface of the Earth for subsequent use or analysis. Downmass logistics are important aspects of research experimental and manufacturing work that occurs in orbital space facilities.

For the International Space Station, there have been periods of time when downmass capability was severely restricted. For example, for approximately ten months from the time of the retirement of the Space Shuttle following the STS-135 mission in July 2011—and the resultant loss of the Space Shuttle's ability to return payload mass—an increasing concern became returning downmass cargo from low-Earth orbit to Earth for subsequent use or analysis. During this period of time, of the four space vehicles capable of reaching and delivering cargo to the International Space Station, only the Russian Soyuz vehicle could return even a very small cargo payload to Earth. The Soyuz cargo downmass capability was limited as the entire space capsule was filled to capacity with the three ISS crew members who return on each Soyuz return. None of the remaining cargo resupply vehicles — the Russian Space Agency Progress, the European Space Agency (ESA) ATV, the Japan Aerospace Exploration Agency (JAXA) HTV — can return any downmass cargo for terrestrial use or examination. With the successful berthing of the commercially-contracted SpaceX Dragon during the Dragon C2+ mission in May 2012, and the initiation of operational cargo flights in October 2012, downmass capability from the ISS is now 3,000 kilograms (6,600 lb) per Dragon flight, a service that is uniquely provided by the Dragon cargo capsule. Eleven additional Dragon cargo resupply flights are scheduled to depart the ISS with downmass each in the next several years.