In designing a process or a system, it’s always wise to ensure your system is able to withstand multiple failures and keep on operating. If it can’t do that, it’s the victim of a single point of failure. When it comes to the International Space Station, that single point of failure has failed. For the past ten years, both the United States and Russia have had the capability to bring crew members to the station. This year, the Shuttle retired which left us with the Soyuz as the single method of transporting crew members to the station.
When the Progress 44 launch failed on August 24th, the single point of failure was activated. The Progress rocket used the same third stage as the manned Soyuz rockets and that was the stage that failed. So, mere weeks before one half of the crew of the ISS was to depart for earth and another three astronauts were to be launched on a Souyz to replace them, all manned space flights are on hold while the failure is investigated. This couldn’t have happened at a worse time. Soyuz spacecraft has an on-orbit lifespan of about 6 months. The crew of Soyuz TMA-21 launched in early April, 2011 and the crew of Soyuz TMA-02M launched in early June. The TMA-21 crew must get back to earth before October and the TMA-02M must return by November. This means that if the Russian investigation into the cause of the failure draws on, it is possible that the station will have to go unmanned for a while. There is not danger to the station if it goes unmanned for a while, as Slate explains. However, if it occurs, the de-crewing will break the 10 year streak of consistent manned spaceflight.
I hope that we will get beyond the point of having only a single point of failure and get back into the business of launching humans in to space. Whether it’s Russia or the United States, humans need to be in the business of getting off Earth.