Space Debris Delays U.S. Spacewalk

Two NASA astronauts were suited up and getting ready to begin a 7 hour spacewalk this morning when it was suddenly cancelled because a piece of space debris was closing in on the International Space Station. The spacewalk has been rescheduled for tomorrow, but the incident is another illustration of the growing problem of debris in low Earth orbit.

Josh Cassada and Frank Rubio were supposed to exit the ISS at 7:45 am ET and install a new ISS Roll Out Solar Array (iROSA). They installed one already on December 3, part of an effort to increase electricity production on the ISS.

But Mission Control called it off when they became aware that a piece of debris from a Russian rocket upper stage would come within a quarter of a mile of the ISS and they needed to move the ISS away to avoid a potential collision.

Engines on Russia’s Service Module (also called Zvezda) and Russian Progress cargo ships are used both to periodically reboost the ISS orbit to compensate for atmospheric drag and to make Pre-Determined Debris Avoidance Maneuvers or PDAMs like this.

Two Progress spacecraft are docked to ISS right now. In this case, thrusters on Progress MS-20 were fired at 8:42 am ET for 10 minutes 21 seconds.

Astrophysicst Jonathan McDowell of Jonathan’s Space Report identifed the debris as coming from a July 18, 2011 launch of a Zenit rocket with the Fregat upper stage, which placed Russia’s Spektr-R space telescope into orbit. McDowell emphasized that the debris is not from the Fregat upper stage itself, but a propellant tank that was jettisoned at the time and disintegrated on May 8, 2020.

The breakup in question was not of the Fregat stage itself but of the Fregat SBB (Sbrasivaemiye baki banov) separable toroidal propellant tank which was jettisoned in an intermediate orbit.

— Jonathan McDowell (@planet4589) December 21, 2022

On 2011 Jul 18, a Zenit-3F/Fregat was launched from Baykonur with the Spektr-R (Radioastron) space observatory. The Zenit stage 2 went to a 177 x 447 km orbit and reentered a few weeks later. The Fregat made a burn to 429 x 3703 km x 51.5 deg, jettisoned the SBB, and (cont)

— Jonathan McDowell (@planet4589) December 21, 2022

then Fregat made a second burn to a deep 2936 x 335094 km x 51.6 deg orbit and released Spektr-R.
The SBB tank disintegrated on 2020 May 8 after 9 years in orbit.

— Jonathan McDowell (@planet4589) December 21, 2022

NASA tweeted this is the third collision avoidance maneuver the ISS has had to make this year.

There have been three Debris Avoidance Maneuvers by the station this year: June 16, Oct. 24, and today. Looking at data from the past couple of years, there were two maneuvers in 2021, and three in 2020.

— International Space Station (@Space_Station) December 21, 2022

NASA rescheduled the spacewalk for tomorrow at 8:30 am ET. NASA TV coverage begins at 7:00 am ET.

Just last week, a planned Russian spacewalk was abruptly terminated when Russia’s Soyuz MS-22 spacecraft dramatically began to leak coolant just outside the airlock two cosmonauts were about to open. They remained safely inside. Roscosmos is still trying to definitively determine what happened, but among the top theories is that the coolant line was ruptured by a piece of debris or a micrometeorite.

NASA ISS Program Manager Joel Montalbano and Roscosmos’s head of human spaceflight Sergei Krikalev, one of Russia’s most experienced cosmonauts, will hold a media briefing tomorrow to discuss the Soyuz MS-22 situation. As it turns out, that briefing will take place while Cassada and Rubio are on their spacewalk.