December 26, 2012
Credit: Credit: Boeing
After a 2012 course correction, efforts by NASA’s International Space Station program to develop a new universal docking system standard for use aboard the 15-nation orbital science lab and future deep-space exploration vessels is on track for an operational debut by 2017.
Rivals in NASA’s efforts to develop a U.S. commercial crew transportation capability — Boeing’s CST-100, Sierra Nevada’s Dream Chaser and the SpaceX Dragon — are in line to initiate and wring out the new universal NASA Docking System (NDS). NASA is targeting 2017 for the first ISS commercial crew missions and planning two U.S. segment docking ports equipped to accept the new, non-proprietary system.
Several years of station operations with the Boeing-inspired Soft Impact Mating Attenuation Concept (Simac), which has replaced NASA’s in-house International Low Impact Docking System (Ilids) design, are envisioned to help qualify the NDS international standard for the rigors of deep space.
“That is the driving force, a more simplified design that is lighter overall, less costly,” says Mike Suffredini, NASA’s ISS program manager. “We want to fly beyond low earth orbit one day, and one of the tenants of the space station is to wring out critical systems at station before we use them for deep space.”
The NDS goal is to accommodate dockings between spacecraft with masses ranging from 5 to 350 metric tons.
The project began with an international docking system standards discussion by ISS Multilateral Control Board representatives in 2009 to encourage greater global cooperation in space, while establishing a more robust rescue capability.
In taking the project lead, NASA’s Johnson Space Center turned to Ilids prototyping underway within the center’s engineering directorate since the mid-1980s. Ilids, intended to eliminate the need for the jarring post-contact thrusting that accompanied shuttle dockings, was adopted in the mid-1990s as part of NASA’s ultimately cancelled X-38 ISS crew rescue vehicle, then NASA’s Orion capsule under the also cancelled Constellation program. One Ilids unit was installed at the base of the Hubble Space Telescope by astronauts in 2009 during a final shuttle servicing mission to the observatory.
However, Ilids was dropped in favor of Simac as the new international standard for the ISS and the post-Constellation Orion Multipurpose Crew Vehicle in 2012 to address several concerns.
Those included the width of the outer soft contact ring in the Ilids system that constricted the post docking passageway, or tunnel connecting the two joined spacecraft and through which astronauts and cargo pass; as well as weight and cost considerations, Suffredini says.