Software glitch caused thrusters to trigger by Nauka module after docking with ISS, according to Russia

Russian cosmonauts aboard the International Space Station continue to fix a problem that has caused the Newly arrived Nauka module to inadvertently fire its thrusters after docking at the orbital outpost.

The situation now seems under control, but, for 47 minutes yesterday, things have weird and even a little scary.

At around 12:34 a.m. EDT, about three hours after docking with the ISS, the New Multipurpose Laboratory Module (MLM), or Nauka, began firing its thrusters. As a result of this unexpected propulsion, the station lost its attitude control, causing it to drift at a speed of about half a degree per second, as ISS program director Joel Montalbano explained during a NASA press briefing held yesterday. In total, the surprise boost caused the space station to shift by about 45 degrees, mostly in pitch.

Russian flight controllers responded by turning off Nauka’s thrusters. Thrusters on the Zvezda module and a docked Progress freighter then returned the space station to its normal position. Attitude control was resumed at 1:29 p.m. EDT, according to NASA.

“At the moment, the station is in its normal orientation, the entire ISS and the mmultipurpose laboratory module systems are functioning normally, ”explained Vladimir Soloviev, flight director of the Russian segment of the ISS, in a Roscosmos declaration. “A reliable internal power and control interface was created, as well as a power interface that connected the module to the station. “

NASA said the crew of the ISS Expedition 65 had never been in danger and no damage was reported. Montalbano said he was “not too worried” about the incident, saying mission controllers were fine. trained for situations like this. A recurrence is no longer possible, he added, claiming that Nauka’s thrusters were “inhibited” by Russian controllers.

“This is one of the most serious incidents in the 24-year history of the ISS,” wrote Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics. to me in an email. “The loss of attitude control risks a priori shattering the complex.

McDowell highlighted a 2016 incident in which the Japanese Hitomi satellite, after encountering problems with its attitude control system, entered an uncontrollable spin, causing it to rupture. The situation on the ISS was “not that extreme,” he said, and the ISS “probably” did not experience structural failure, McDowell wrote, “but you don’t want to a 400 ton station with large flexible parts like solar panels that fall end to end.

McDowell said he was concerned about the condition of some outdoor experiments attached only by metal ties. The “fight” between Nauka and the other control modules – in which several sets of thrusters were engaged – could have created “oscillations in the flexible parts of the structure, in particular” the radiators and solar panels “, in which the Design tolerances may have exceeded, he writes.

Soloviev said a “short-term software failure” was at the root of the incident, in which a “direct command was mistakenly implemented to turn on the module’s motors for removal, resulting in some modification of the orientation of the complex as a whole. “

As a result of this inadvertent thruster firing, NASA postponed today’s session planned launch of unmanned Boeing CST-100 Starliner commercial crew vehicle. The second test drive of this vehicle is now program for August 3 at 1:20 p.m. EDT. The postponement “gives the International Space Station team time to continue working on the checks of the newly arrived Nauka module from Roscosmos and to ensure that the station will be ready for the arrival of Starliner”, according to a statement from NASA. declaration. Of course, sending a test spacecraft to the ISS while the crew continued to resolve a serious situation wouldn’t have made much sense.

Mission specialists are now trying to determine how much propellant was lost by the ISS because the crew had to regain attitude control. Montalbano said the procedure had not depleted the station’s fuel reserves, but that it was “obviously more propellant than we wanted but nothing to worry about.”

Russian cosmonauts are now performing a set of procedures to ensure the “unconditional safety” of the ISS and its crew, especially tasks related to the Nauka module’s propulsion system, according to a Roscosmos. declaration. After that, the crew will open the hatches, first the Zvezda service module, then the new Russian module. Cosmonauts “will open the hatches, enter the module, turn on the means necessary to purify the atmosphere and begin normal regular work,” said Soloviev. They will also need to balance the pressure in the Nauka module, which will take time, because the total volume of the module encompasses 2,472 cubic feet (70 cubic meters).

The Nauka module spear from the Baikonur Cosmodrome on July 21, but its initial propellant burned failed, forcing flight controllers to use back-up engines. Concerns about a wobbly antenna and docking port complicated matters even more, but the docked module “nominallyWith the ISS on July 29 at 9:29 a.m. EDT.

The new module will provide additional space to perform experiments, store cargo and accommodate new water and oxygen regeneration equipment. Nauka has a second toilet for the Russian crew and an additional room for a third Russian crew member. The module also delivered a new airlock and the new European Robotic Arm (ERA), which will be the first robotic arm to serve the Russian segment.

Following: Inspector Gadget robotic arm heads for the International Space Station.