The International Space Station is getting an important piece of cargo next week: a new International Docking Adapter, or IDA, that will allow future crewed spacecraft to automatically dock with the station. The large metallic ring, which measures 63 inches in diameter, will eventually be installed on the Harmony module. This is the second IDA to be sent to space, though the first one never actually made it to orbit; it was destroyed when the SpaceX Falcon 9 rocket carrying it to the ISS disintegrated during launch in June 2015.
This is the second IDA to be sent to space, though the first one never actually made it
This new IDA is slated to launch early Monday morning from Cape Canaveral, Florida on a SpaceX Falcon 9 rocket. The vehicle will carry around 3,800 pounds of fresh cargo and science experiments, including a space-based DNA sequencer called minION that will be used by NASA astronaut Kate Rubins to sequence DNA in space for the first time. But the IDA is perhaps the key item onboard.
The ring is crucial for the future of NASA’s Commercial Crew Program — an initiative that tasks private companies with building and operating spacecraft that can transport astronauts to and from the ISS. Both SpaceX and Boeing, the companies contracted through the program, are currently developing these space taxis for NASA. SpaceX is updating its current Dragon cargo capsule into a crewed vehicle aptly named Crew Dragon, and Boeing is creating its own capsule, the CST-100 Starliner. Those are supposed to launch for the first time with people on board in late 2017 and early 2018, respectively.
An illustration of where the two IDAs will eventually be placed on the ISS. (NASA)
When the SpaceX and Boeing spacecraft reach the ISS, they’ll attach to the IDA. The IDA is outfitted with a host of sensors that spacecraft navigation systems can track and use to guide incoming vehicles through proper docking procedures. This means that astronauts on board the ISS won’t need to be involved with docking the spacecraft.
The adapter won’t be limited to just docking SpaceX and Boeing vehicles
But the adapter won’t be limited to just docking SpaceX and Boeing vehicles. The ring was built according to the International Docking System Standard, an international standard created in 2010 to guide the designs of space docking adapters. That means that future space vehicles, at least those with docking systems that adhere to standard, can also attach to the IDA.
The plan is to install the IDA to the station later this summer. The ISS robotic arm will remove the adapter from the trunk of SpaceX’s Dragon cargo capsule after it docks to the station later next week. The arm will put the IDA near its intended port on the Harmony node, where it will be connected. Then, the astronauts will eventually perform a spacewalk out to the IDA to finalize its installation.
This installation, however, was supposed to have happened already. The loss of the first IDA last year threw NASA’s Commercial Crew plans off balance. Next week’s launch was meant to bring the total number of adapters aboard the station to two. Now there will only be one until a replacement IDA is launched on a future SpaceX cargo mission, which may not happen until 2018.
An artistic rendering of how Boeing's Starliner will dock with the ISS. (Boeing)
And that could be a problem for Commercial Crew. A recent report from NASA’s Office of Inspector General speculated that because of the failure, only one IDA will be installed on the ISS by the time the first commercial vehicles launch in 2017. That means if there is a technical issue with the single IDA, there won’t be any other docking options and incoming vehicles will be unable to connect to the ISS.
NASA is trying to ensure that two adapters will be installed and ready before Commercial Crew flights begin
However, station managers are trying to ensure that two adapters will be installed and ready before Commercial Crew flights begin. Kirk Shireman, NASA’s ISS Program manager, said that the space agency plans to fly the replacement for the destroyed IDA on SpaceX CRS-16, or the company’s 16th ISS cargo mission, which doesn't have a tentative launch date yet. However, he noted that the IDA may launch sooner depending on when the first Commercial Crew launches are slated to occur, to make sure that two IDAs or on board prior to those flights.
"It’s not required to have both IDAs on orbit prior to the launch of the first Commercial Crew test flight," Shireman told The Verge during a press conference. "But we are actively monitoring the schedules of the Commercial Crew vehicles. We’re planning to launch on SpaceX 16, or a little earlier if we have to."