Backup Soyuz can't get to ISS before the end of February

Enlarge / A Soyuz spacecraft docked to the ISS. Nasa

Today, NASA held a press briefing to outline the situation on the International Space Station (ISS) following a major coolant leak from a docked Soyuz spacecraft at the station. At this time, neither NASA nor Roscosmos has a clear idea of ​​its options for using the damaged spacecraft. If it is unusable in its current state, it will have to wait until February to replace it with the ISS.

Soyuz spacecraft are one of two vehicles used to transport humans to and from the ISS, and serve as a “lifeboat” in case personnel need to quickly evacuate the station. So even if the leak does not endanger the ISS or its crew, it reduces the margin of error and can potentially interfere with future crew rotations.

As Roscosmos reported earlier this week, the impressive plume of material comes from a millimeter-sized hole in a coolant radiator. Although the cooling system has redundant pumps that could handle failures, the leak caused all the coolant to be lost, so there is nothing to pump at this point.

Sergei Krikalev, executive director of human spaceflight programs at Roscosmos, said ISS partners had already performed an analysis comparing the orientation of the hole to the likely direction from which any micrometeorites would have come. The two don't match, so there's no indication of how the damage occurred. The coolant does not present any danger to the exterior of the ISS.

At the time of the damage, the next Soyuz launch to the ISS was scheduled for a crew rotation in mid-March. Krikalev said that could be brought forward a few weeks to the end of February, which would bring a serviceable lifeboat to the station. Whether or not this carries a replacement crew will depend on whether the damaged capsule is considered safe enough to bring the current crew back to Earth. (Soyuz can perform automated station docking, so it can be sent to the ISS unmanned.)

At the moment, however, we still don't know if the damaged Soyuz can safely return the crew to Earth in the absence of a cooling system for its internal compartment. “As soon as we start powering up the equipment and as soon as the crew goes inside the crew compartment, the temperatures start to rise,” Krikalev said. "We don't know exactly how high it will rise, and our specialists in Russia, together with specialists in Houston, will estimate the rate of temperature increase and what maximum temperature can be reached during different modes of re-entry. "

These different modes include an option that minimizes the time Soyuz stays in space before re-entering. There's also the option of what Krikalev called "analogue re-entry", which is essentially manual control of the process, allowing some of the internal electronics to be shut down. If any of these re-entry options prove viable, the ISS's Soyuz could fulfill its role as a lifeboat despite the damage. Whether "viable in an emergency" is desirable for a crew rotation is a separate question.

“If the nominal entry is dangerous – or not safe enough, I would say,” Krikalev said, “then we will send a vehicle to have a good spacecraft for the crew.” This vehicle would be empty, which would mean an extended stay on station for the existing crew, and the ISS would be without a lifeboat until its arrival. NASA's Joel Montalbano indicated that in this case the damaged Soyuz would be returned empty to allow Roscosmos to obtain data on its behavior.

In the meantime, Montalbano said, things are getting back to normal on the ISS, with a spacewalk underway for the installation of solar panel upgrades. He said the next rotation of US personnel is still scheduled for a Jan. 9 departure on a Dragon spacecraft.