Dragon spacecraft delivering a new door to improve docking at the ISS
Sometime in the next 12 hours or so, the CRS-9 SpaceX Dragon spacecraft should be berthing at the International Space Station (ISS), possibly for the last time. The ship that was launched just after midnight on the 18th has been syncing up its orbit with the ISS, so that it can gently be attached to the station itself. Once lined up with the station at a safe distance, the Dragon capsule will then basically surrender control of its own navigation so astronauts on the station use the robotic Canadarm to capture it and bring it gently to a hatch on the station. Once the spacecraft is berthed, astronauts will have access to equipment that will rewrite this entire process for future missions, enabling automated docking at the ISS for the first time.
Parking without pilots
Most of us don’t worry about the difference between docking and berthing, but in scenarios involving large ships, or even small craft moving at terrifying speeds, the are very important distinctions. Docking is when a vehicle can basically park itself without outside intervention. In 1967, two automated Soyuz spacecraft docked with each other for the first time. Once manned space-stations were in play, docking was done only in piloted spacecraft. To minimize the risk of dangerous collisions, unmanned craft have instead been berthed, or parked by outside intervention. In a port, this would be the job of a tugboat, but on the ISS that job usually falls on astronauts controlling the Canadarm robotic crane.
The concern with unmanned craft has mostly been over trusting that they’d be able to dock carefully enough on their own. To help with this, a key piece of cargo on this week’s CRS-9 mission is the International Docking Adapter (IDA). This new port attaches to the outside of the ISS’s existing ports, allowing 63 inches of clearance to the station from any docked spacecraft. It is equipped with a variety of sensors and connection points, which will allow the IDA and future spacecraft coordinate docking procedures, and then share data directly once connected. It will allow spacecraft to handle docking without any human intervention (aside from as a backup), which should help streamline future mission design.
New shared standards
It won’t just be the Dragon modules that will be making use of the new IDA port once it’s installed. In addition to the onboard sensors, the port is designed according to a new, international standard. This means that any future spacecraft that use this standard should be able to connect to the ISS, or even each other, as the IDA itself is agnostic in it’s connecting mechanisms. Basically, it’s the USB 3.0 plug for spacecraft, with no top or bottom to fumble around with. As a whole, the IDA system should make docking much easier than in the past, hopefully spurring more frequent rendezvouses between a variety of spacecraft.
This week’s delivery will be the first of two IDA components for the ISS, with the second being sent up in a later mission. It’s also the second time such a delivery has been attempted, as the first IDA was lost in June, 2015, after the Falcon 9 rocket launching the payload blew up 139 seconds after liftoff. Since this mission has been off to a much smoother start, complete with a successful first-stage landing, hopes are high for the successful installation of the ISS’s new front door.
Source: SpaceX CRS-9 Carrying Crucial Port to Station by Steven Siceloff, NASA News