This spacewalk could have a big payoff
By Cat Hofacker|August 20, 2019
The addition of a new docking port to the International Space Station could mean more business
Update: International Docking Adapter-3 was installed on the Harmony module, NASA said. The spacewalk ended about 3 p.m. EDT and lasted six hours and 32 minutes.
Astronauts are scheduled to conduct a 6½-hour spacewalk Wednesday to prepare the U.S. portion of the International Space Station for what could be a bustling future of multiple capsule dockings.
At the moment, the Harmony module, where cargo capsules dock, has just one port. That’s a problem because astronauts arriving or departing will need to pass through this module once Boeing and SpaceX begin their Commercial Crew flights.
Kirk Shireman, the ISS program manager, compares this to “living in a one-car garage.” No one can pull in until there’s room in the garage.
It’s a limitation that NASA wants to solve before the long-delayed Commercial Crew capsules start flying in a matter of weeks or months. Starliner is scheduled to make a first uncrewed flight in October or November, and Crew Dragon will make its first crewed flight “hopefully this year,” SpaceX’s Hans Koenigsmann, the company’s head of spaceflight, said Monday at the AIAA Propulsion and Energy Forum in Indianapolis.
So, on Wednesday NASA astronauts will install a second docking port onto Harmony.
The International Docking Adapter-3, IDA-3 for short, will be attached to the top of Harmony, whereas the existing dock is on the front, meaning the side facing Earth. With two ports, Harmony can accommodate any combination of two Commercial Crew or future vehicles that space entrepreneurs might construct, Shireman said during a Friday briefing at Johnson Space Center in Houston.
“We expect that other private vehicles will come up and bring visitors to ISS on that docking port,” he said, referring to IDA-3, “so we really need to have this capability.”
NASA will stream the spacewalk on its website. Coverage will begin at 6:30 a.m. EDT, and the IDA-3 install is scheduled to start at 8:20 a.m.
Boeing designed the new port to meet the International Docking Standard, a set of uniform measurements available online for governments and companies to reference when designing spacecraft to dock with the ISS. The two Commercial Crew spacecraft were built to this standard.
On Monday, ground controllers at Mission Control in Houston commanded Canadarm2 and the two-armed Dextre robot at its end to pull IDA-3 from the trunk of the Cargo Dragon that docked with the Harmony module in late July. Dextre continues to hold the new docking port, awaiting the start of the spacewalk.
Just before Wednesday’s spacewalk, Dextre will move IDA-3 into position against a pressurized mating adaptor at the top of Harmony. This adaptor will equalize the air pressure between the station and a docked capsule. Astronauts Nick Hague and Andrew Morgan will route color-coded cables along the outside of the ISS into the correct sockets on IDA-3. The ISS will transmit power and data to IDA-3 via these cables.
Connecting the cables, which were brought outside on a spacewalk about five years ago, will take several hours, said Alex Kanelakos of Johnson Space Center, the lead spacewalk officer for this extravehicular activity.
“They have baked in the sun and have UV and AO [atomic oxygen] exposure, so we expect them to be very difficult to manipulate and route,” he said. “They will be stiff and want to maintain the coiled shape” they were kept in.
Once all the cables are connected, NASA astronaut Christina Koch will finish the install from inside the ISS. She will push a button on a control panel in the Destiny Laboratory to close a set of hooks on IDA-3 to latch onto the pressurized mating adapter, sealing the two components together.
Still to be determined is which Commercial Crew capsule will be IDA-3’s first visitor.