More Years Eyed For ISS, To Increase Utilization

By Frank Morring, Jr.
Source: Aviation Week & Space Technology

“ISS extension will extend the broader flow of societal benefits from research on the Station,” Administrator Charles Bolden and John Holdren, Obama's science adviser, wrote in a joint blog.

It also will allow more time for improvements in the station itself. John Shannon, the former NASA space shuttle program manager who is now ISS program manager for station prime contractor Boeing, says the recent repair of a cooling system malfunction demonstrates the station is “robust” and ready to accommodate more users.

The company conducted engineering and logistics analyses that supported the decision to extend ISS service life, he says. The structure, instrumented with wireless accelerometers that measure how it reacts to arriving vehicles, thruster firings and solar-array motion, is fit to operate until at least 2028. The twin 10-ft.-dia. solar alpha rotary joints—too large to replace now that the space shuttle fleet is retired—have been working well since a lubrication problem was resolved in 2008, he says. The joints move the station's huge solar-array wings to track the Sun.

Launch and orbital vehicles available or expected to deliver cargo and crew to the station can support extended operations, Shannon says. However, bandwidth for research data already is in short supply, despite a doubling since assembly was completed, and is one potential shortfall as station utilization increases. Power is another.

Managers are considering an upgrade to Ka-band links to increase data throughput, Shannon says, and are studying ways to take advantage of improvements in solar-cell efficiency. One possibility may be to fold more efficient solar cell blankets to fit in the unpressurized “trunk” on the SpaceX Dragon cargo vehicle, and send station crewmembers on spacewalks to mount them over the existing arrays.

The Dragon and Orbital Sciences Corp.'s Cygnus are easing into regular commercial cargo deliveries to the ISS (see sidebar), and NASA's international partners continue to provide logistics support as well. The European Space Agency (ESA) will launch one more Automated Transfer Vehicle with a load of supplies, and early talks are underway with Japan to arrange three more H-II Transfer Vehicle cargo missions after 2015. Russian Progress cargo-carriers also will remain in the logistics mix.

Final proposals for U.S. commercial crew vehicles are due this week, with the first flight of at least one targeted for 2017. However, that may slip, so NASA and Russia are gearing up for another buy of Soyuz-capsule seats to stay within the three-year lead-time window for the Russian spacecraft. Overall, Gerstenmaier says, “knowing now that we're going beyond 2020” puts NASA planners in a better posture to get better prices for crew and cargo services.

The White House announcement came as the heads of more than 30 international space agencies gathered in Washington for a private summit organized by the U.S. State Dept., in parallel with an International Academy of Astronautics symposium on space exploration. The ISS extension was expected to be a key topic of discussion.

Jan Woerner, who heads the German space agency DLR, lists himself as a long-time supporter of extending ISS operations beyond 2020, and Germany is the largest supporter of station funding within ESA. Although ESA's future course in station funding will not be set until a ministerial meeting early in December, both agencies have entered a preliminary agreement with one of the private U.S. companies developing a commercial crew vehicle for NASA.

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