Crew-6 Docks After Another Hook Anomaly

NASA’s Crew-6 docked to the International Space Station on March 3 after solving another problem with a hook in the SpaceX Crew Dragon nose cone. SpaceX had to send a software update to override data that indicated Hook 5 was not properly positioned after verifying that it was, in fact, OK. An earlier issue with the same hook, one of 12, forced ground controllers to use a backup system to open the nose cone after the spacecraft reached orbit a day earlier. A faulty sensor was blamed in both cases.

The four members of Crew-6 on SpaceX’s Crew Dragon Endeavour successfully launched from Kennedy Space Center early Thursday morning, March 2, three days after an initial attempt was scrubbed due to a clogged filter in a piece of ground equipment.

Shortly after reaching orbit, Crew Dragon’s nose cone must open in order to expose 12 docking hooks used to attach it to the ISS. Opening the nose cone requires six of them to release. Each hook has sensors, or limit switches, that indicate the hook’s position.

One of the sensors on Hook 5 indicated a problem so Endeavour’s system automatically switched to a backup set of motors to successfully open the nose cone. SpaceX determined the problem was a faulty sensor.

As Endeavour approached the ISS 24 hours later, ground controllers got another indication that Hook 5 was not operating properly.

All Crew Dragon spacecraft operate autonomously while monitored by ground controllers, the crew aboard the spacecraft, and the crew on the ISS. For safety reasons, rendezvous and docking procedures call for the spacecraft to stop at waypoints at specific distances from the ISS when it’s within the “keep out sphere” to ensure everything is proceeding as planned.

When Endeavour reached Waypoint 2 just 20 meters (66 feet) from the ISS, it was supposed to pause for just a few seconds, but ground controllers radioed to the crew that “we see your docking hook not open.”

Endeavour remained in place while ground controllers determined what the problem was and found a solution.

Once again the fault was traced to a bad sensor on Hook 5.

NASA told SpacePolicyOnline.com via email that the “NASA and SpaceX teams verified that all of the docking hooks were in the proper configuration, and SpaceX developed a software override for the faulty sensor that allowed the docking process to successfully continue.” Only one of the hook’s sensors showed an “indeterminant” position while the others showed “the proper configuration for docking.” Ground controllers “were also able to confirm the hook was physically open by looking at the current trace and tachometer of the hook’s motor.”

The software override did the trick. Crew-6 docked at 3:45 am ET, about two-and-a-half hours later than planned (1:17 am ET).

The four members of Crew-6 — NASA astronauts Steve Bowen and Woody Hoburg, Roscosmos cosmonaut Andrey Fedyaev and UAE astronaut Sultan AlNeyadi — were greeted by the seven-person ISS crew — NASA astronauts Nicole Mann, Josh Cassada, and Frank Rubio, Roscosmos cosmonauts Sergey Prokopyev, Dmitri Petelin and Anna Kikina, and JAXA astronaut Koichi Wakata.

Bowen, Hoburg, Fedyaev and AlNeyadi are replacing Crew-5 (Mann, Cassada, Kikina and Wakata), who will return to Earth around March 9 on their Crew Dragon Endurance. The exact date has not been set and is weather dependent.

SpaceX Crew Dragon spacecraft are reusable. This is the fourth flight of Endeavour. It was the very first Crew Dragon to take people to space, test pilots Bob Behnken and Doug Hurley on Demo-2 in 2020. It then flew Crew-2 in 2021 and Axiom-1, the first all-private astronaut flight to dock at ISS, in 2022.  Axiom-1’s docking also was delayed by about 45 minutes at Waypoint 2.  ISS crew members were not able to receive views of the ISS docking port from Dragon’s center line camera. Space X was able route video to the ISS crew using a SpaceX ground station allowing the docking to proceed.