Saturday, August 20, 2016

New ‘Front Porch’ Added to International Space Station

Williams and Rubins work to attach adjustable tethers to IDA-2 in order to secure it to PMA-2 to allow for Dextre to release its grip. Photo Credit: NASA TV

Two members of the International Space Station’s Expedition 48 crew stepped outside the orbital complex to install a new “front porch”. The nearly six-hour long spacewalk started at 7:04 a.m. CDT (12:04 GMT) Aug. 19 with a goal to install International Docking Adapter-2 (IDA-2) to the forward end of the station.

NASA astronauts Jeff Williams and Kate Williams, commander and flight engineer, respectively, each tag-teamed to install IDA-2 as the primary task of the mission. The adapter was brought to the space station by way of SpaceX‘s CRS-9 Dragon. It has remained inside the trunk since arriving at the outpost one month ago.

The two spacewalkers left the Quest airlock and began moving toward the Pressurized Mating Adapter-2 (PMA-2), located on the forward port of the Harmony module. Williams was on his fourth spacewalk while Rubins was on her first.

Williams was the lead spacewalker, EV-1, with red stripes on his suit and Rubins was EV-2 with white strips.

Back on Wednesday, ground teams controlled the station’s robotic Canadarm2 with the Special Purpose Dexterous Manipulator (Dextre) robotic “hand” attached to the end of the arm. The arm used Dextre to grab the IDA-2, located inside Dragon’s trunk, and carefully pull it out.

IDA-2 was moved to within a few feet (about a meter) in front of PMA-2 where it stayed for more than a day. Then, a few hours before the spacewalk, it was moved to make contact with the docking ring.

When Williams and Rubins arrived at the work location, they began attaching power and data cables that were run across the station in the last year over four separate spacewalks spanning multiple expedition crews. Additionally, special adjustable tethers were attached to secure IDA-2 with PMA-2.

After confirming the adapter was firmly attached via the tethers, ground teams detached and slowly moved Dextre away.

Once that task was completed, inside ISS, Flight Engineer and Japan Aerospace Exploration Agency (JAXA) astronaut Takuya Onishi used a special IDA control panel to command the latches on IDA-2 to engage into PMA-2.

After a firm connection was established, the crew mated a few more cables and installed reflectors. Finally, the cover in front of IDA-2 was removed, revealing the docking petals to space – this officially made IDA-2 ready to receive commercial vehicles.

“It is amazing that now we’ve opened up a new chapter in the story of the International Space Station, putting the front door on this for future commercial vehicles,” Williams said not long after official confirmation of mating had occurred. “Congratulations to the entire team.”

The next task the spacewalkers completed included the running of even more cables to prepare for IDA-3 to be installed, currently expected sometime in 2018.

Additional tasks for EVA-36 included running power and data cables for a future Russian module addition to the ISS – Nauka – currently scheduled for sometime in late 2017.

After that had been completed, there was time for the duo to perform a couple of get-ahead tasks. First was to reconfigure a CETA cart brake handle and the second was to conduct a photo survey of a side of the Alpha Magnetic Spectrometer that the station’s external cameras cannot see.

However, sometime into the fifth hour of the spacewalk, Williams lost audio in his right ear. Fears that the water-in-the-helmet issue might crop up again, he was commanded to check his helmet absorption pad (HAP). It remained dry, so water buildup was not believed to causing the audio problem.

While everything was well within safety margins, Mission Control in Houston recommended ending the EVA early. As such, the two get-ahead tasks were not completed.

In total, between switching on to battery power (marking the official start of the spacewalk) to connecting their suits to power and cooling ports at 1:02 p.m. CDT (18:02 GMT) inside the airlock after returning (marking the end of the spacewalk), the duration of the EVA was five hours and 58 minutes.

After closing the airlock and pressurizing the crew compartment, the astronauts were helped out of their suits by their crewmates inside the space station.

Once back inside, the right earpiece on the Comm cap was found to be a bit wet when touched. It will be bagged for analysis at a later date in order to test its functionality. It will not be used for the next spacewalk, EVA-37, scheduled for Sept. 1.

Today’s walk was the 194th EVA in support of ISS assembly and maintenance – totaling 1,210 hours and 46 minutes. To put that into perspective, that is also 50 days, 10 hours and 46 minutes.

Preparation for this EVA spanned multiples years. Originally, the spacewalk was supposed to take place last summer. However, a launch mishap in June 2015 destroyed the CRS-7 Dragon capsule carrying IDA-1.

This current adapter, IDA-2, was the second to be built. A third is currently being manufactured by Boeing as a replacement for IDA-1 utilizing spare parts. Both will be used to support the Commercial Crew Program when SpaceX’s Crew Dragon and Boeing‘s CST-100 Starliner when they start flying.

The reason these adapters were manufactured was that a new International Docking System Standard (IDSS) was developed. The design utilizes low-impact technologies and allows for both docking and berthing. Additionally, it can support either autonomous or piloted dockings.

It adapts the current Russian-designed APAS-95-based system that was used during the Space Shuttle era. IDSS is not compatible with the old system, so the IDA converts the port to the new NASA docking standard, which is the agency’s implementation of the IDSS.

Boeing, SpaceX, and Sierra Nevada Corporation (with their Dream Chaser Cargo System) plan to utilize the IDSS for their crew and cargo vehicles.

Written by: Derek Richardson
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