A manned American spacecraft has not docked with the International Space Station (ISS) in over four years, but that is bound to change. Boeing’s CST-100 Starliner and SpaceX’s Crew Dragon are the future spacecraft that will transport NASA astronauts to and from low-Earth orbit (LEO). These private companies are busy developing their spacecraft for future manned missions to the International Space Station (ISS) under NASA’s Commercial Crew and Cargo Program; meanwhile, engineers are testing the unit responsible for connecting the next generation spacecraft to the orbiting laboratory. Once installed, the International Docking Adapter (IDA) will serve as an entryway to a new future in America’s space program aboard the ISS, and there will be two of these adapters on the ISS to dock visiting spacecraft.
Engineers recently tested the mechanisms that will connect the future Boeing Starliner and Crew Dragon spacecraft to IDA-2, the second IDA, at the Space Station Processing Facility at NASA’s Kennedy Space Center in Florida. The adapters are built to the International Docking System Standard (IDSS) that establishes “a standard docking interface to enable on-orbit crew rescue operations and joint collaborative endeavors utilizing different spacecraft.” The IDSS features systems that are built in for automated docking and uniform measurements. This allows a variety of spacecraft (commercial and international) to use the adapters in the future.
The first docking adapter, IDA-1, was lost with the SpaceX CRS-7 Dragon cargo ship failure in June 2015, when 44,000 pounds of cargo heading to the ISS was lost 139 seconds after launch. IDA-2 is expected to go up to the ISS on CRS-9, originally targeted for December 2015, with a present target date of no earlier than (NET) January 2016. Astronauts on the ISS have been preparing for the IDA’s since early 2015 when Barry “Butch” Wilmore and Terry Virts, part of the Expedition 42 crew, participated in a six hour and 41 minute Extravehicular Activity (EVA) to lay and configure cables for the future arrival of the IDA’s. Relocation of the Leonardo Permanent Multipurpose Module (PMM) on May 27 was one of the first steps taken to reconfigure the U.S. Orbital Segment (USOS) for Commercial Crew vehicles. The loss of IDA-1 impacted future operations to reconfigure the USOS for Commercial Crew.
According to a previous AmericaSpace article, “IDA-1 would have been robotically removed from Dragon’s truck and ‘temp-stowed’ on the Dextre Special Purpose Dextrous Manipulator (SPDM) of the 57.7-foot-long (17.6-meter) Canadarm2 robotic arm, before being installed onto the [PMA-2] at the forward end of the Harmony node during an EVA by Kelly (EV1) and Lindgren (EV2) on 17 August.” IDA-1 was the primary adapter SpaceX and Boeing would have used to dock to the ISS from mid-2017 and into the future. IDA-2 was to serve as a back-up docking interface mounted on PMA-3 at the Zenith port of the Harmony module.
Both of the IDA’s will be connected to the Harmony module and placed on each of the station’s two open Pressurized Mating Adapters (PMA). As each one arrives on a Dragon cargo vehicle, the robotic arm on the station will remove the IDA from Dragon’s trunk and move it about one foot (30 cm) from the front of the PMA for astronauts to manually connect using tethers during an EVA.
Both of the IDA’s are identical, so IDA-2 will now serve as the primary docking adapter instead of IDA-1. A replacement unit, IDA-3, will be completed and launched at a later date. In a previous AmericaSpace article, NASA’s Rob Navias told AmericaSpace that IDA-3 will be built from spare parts and there is no current timetable on when it might be ready.
Boeing served as the Lead Integration Contractor on the IDA’s with parts assembled from various companies across 25 states. Each of the IDAs measure 42-inches tall and 63-inches wide and constructed by national and international teams. RSC-Energia is the Russian company responsible for making the primary structures of the IDAs. Systems arranged around the outside of the IDA’s, such as docking targets and laser retro-reflectors, gives the IDA’s an outer diameter of approximately 94 inches. IDA-2 will go through in-depth testing with both the Boeing CST-100 Starliner and SpaceX’s Crew Dragon spacecraft before the adapter is readied for launch.
According to NASA, “the systems and targets for the IDA are much more sophisticated than previous docking systems and include lasers and sensors that allow the station and spacecraft to talk to each other digitally to share distance cues and enable automatic alignment and connection.”
The IDAs are not only a key element for Commercial Crew, but also a key element for future collaborative exploration aboard the ISS. The need for the International Docking System Standard was outlined by NASA in 2011. It was noted that the “expansion of spacefaring nations (and non-governmental entities) will compound this issue in the future. Exploration cooperation could be much easier with internationally accepted interface standards.” The IDSS also enables low impact technology to accommodate a wide range of vehicle contact and capture conditions.
NASA’s Senior Project Manager for Relocation & IDA, Sean Kelly, spoke out about the significance of the IDA in February 2015:
“The International Docking Adapter is actually the first implementation of our International Docking System Standard. We’ve developed that over the last few years with all of our International Partners, so it’s really the first standard that we have in the spaceflight business and, as such, we wanted to lead the way and NASA established an effort to develop the International Docking Adapter. We tried tot put the emphasis on ‘international’, because although it’s in the critical path for Commercial Crew, it’s also a key element for what we plan for other international partners to come visit Space Station and start utilizing it in the future.”
Since the retirement of the Space Shuttle, NASA shifted its focus from working and living in low-Earth orbit to the Journey to Mars. This change opened up a new realm of opportunities for the commercial space industry when NASA called to the private sector to provide transportation to the International Space Station (ISS). The Commercial Crew and Cargo Program allows NASA to keep astronauts working in LEO while the agency focuses on building the infrastructure to take humans to deep space.
The integration of the IDAs to the ISS will be a significant milestone as NASA transitions from Space Shuttle to Commercial Crew. Although the United States is not back to launching humans just yet, the necessary preparations to get them flying from American soil are taking place on Earth and above our heads.
.Missions » ISS » COTS » CRS-7 » Missions » ISS » COTS » CRS-8 »