NASA and Roscosmos trying to avoid an empty Space Station

by Thomas Burghardt

Following the failure of the Soyuz MS-10 spacecraft to deliver Aleksey Nikolayevich Ovchinin and Nick Hague to the International Space Station last week, the orbital outpost is now left with two fewer crew members than planned. NASA now must assess their options for keeping the station occupied, pending Roscosmos’ updated launch schedule once the investigation into the Soyuz-FG failure has been completed.

Roscosmos immediately created a State Commission to determine the cause of the MS-10 abort and their investigation is already progressing.

Initial reports claim one of the four strap-on boosters is suspected to have incompletely separated from the center core booster, then impacted the core causing the main engine to shut down and the spacecraft to automatically abort.

According to L2, the spacecraft reached an apogee of 93 kilometers and landed 32 kilometers southeast of Dzhezkazgan, 19 minutes and 41 seconds after launch. These findings are only preliminary, as the first official report from the commission is yet to be published.

How quickly the commission can conclusively determine the cause of the failure and the corrective action needed to return the Soyuz-FG rocket to flight will be the driving factor in determining the space station’s fate. In an ISS status briefing the day of MS-10’s launch, ISS manager Kenny Todd stated that NASA hopes to avoid de-crewing the station.

Whether this can be accomplished relies not only on how quickly Soyuz-FG can return to flight, but how long the MS-09 spacecraft currently docked to the station can stay there. Soyuz spacecraft have an on-orbit lifetime of approximately 200 days.

This lifespan is limited by the Hydrogen Peroxide used by the Descent Module’s RCS thrusters. Extended time on orbit means the Hydrogen Peroxide becomes decomposed into gaseous Oxygen and Hydrogen, which create bubbles within the liquid-fueled thrusters.

These thrusters are used to orient the spacecraft from module separation through reentry. If bubbles form in the liquid fuel, the thrusters can become unreliable, forcing the crew to re-enter on a risky ballistic trajectory instead of a controlled descent.

The MS-09 spacecraft, launched in early June, will reach the end of its lifespan in late December. Prior to the MS-10 launch, MS-09 was scheduled to depart the station with the crew of Expedition 57 on December 13, a week ahead of the MS-11 launch on December 20. This would have left Hague and Ovchinin the sole occupants of the station for one week. Now, with Hague and Ovchinin still on the ground, there are a limited number of scenarios which avoid an empty space station.

Soyuz MS-09 arriving at the ISS – via Roscosmos

The prime scenario to keep the station occupied and the MS-09 spacecraft within its lifetime is for Soyuz-FG to return to flight prior to December. According to unconfirmed reports, a Soyuz-2 rocket carrying a Lotus-S electronic intelligence satellite for the Russian military is scheduled for October 25. Additional launches of the Soyuz-2 variant carrying a GLONASS navigation satellite and the ESA’s MetOp-C mission (to be launched by Arianespace) are also tentatively planned in the coming weeks. These uncrewed missions could serve to re-certify the Soyuz booster.

The Progress MS-10 cargo mission is also scheduled to launch on a Soyuz-FG rocket before the Soyuz MS-11 crew mission (on a Soyuz-FG) would then launch in early December with the crew of Expedition 58, ahead of the return of Expedition 57 aboard Soyuz MS-09. Unconfirmed reports suggest MS-11 has indeed moved forward, suggesting that the investigation is nearing a conclusion and that this prime scenario is the current plan.

MS-09 is the same Soyuz spacecraft that developed a pressure leak while docked to the station in August. The source of the leak was a breach in the spacecraft’s orbital module, which was repaired the same day to stabilize the station’s pressure. The cause of the breach is still under investigation but does not pose a threat to the spacecraft’s ability to return the current station’s crew back to Earth.

The hole – since sealed – in the docked Soyuz MS-09 – via NASA.

A second, unlikely scenario is that Roscosmos clears the Soyuz booster to fly only without a crew aboard. An empty Soyuz MS-11 spacecraft could launch to the station and dock autonomously, prior to the end of MS-09’s lifespan.

A successful launch would allow the MS-09 spacecraft to deorbit, empty, leaving MS-11 as the return spacecraft for the current station crew. The crew would extend their time on orbit until MS-12 can bring the next crew. Any problems during launch that prevent MS-11 from reaching the station would mean MS-09 bringing the station’s crew home, leaving the station unoccupied.

Mr. Todd in the ISS status briefing expressed confidence that ground controllers could fly the station remotely for a significant amount of time. While an empty station wouldn’t present significant technical challenges, it would be a symbolic loss for the ISS program, as the station has been constantly occupied since Expedition 1 arrived in 2000.

If the Soyuz booster is not cleared for flight prior to December, engineers on the ground could extend the time MS-09 spends on orbit. However, the nature of the Peroxide decomposition issue which limits the Soyuz lifetime does not produce any effects that are measurable by the spacecraft’s instruments, meaning engineers would have little data to justify exceeding engineering limits. This makes an extension of MS-09’s mission unlikely.

Since keeping a crew aboard the station requires an operational return vehicle in case of an emergency, a late return to flight for the Soyuz booster and no extension of MS-09’s mission would mean the return of Expedition 57 and an empty space station.

As of now, the only spacecraft capable of transporting humans to and from the station is Soyuz. However, two American Commercial Crew vehicles are nearing their first test flights and present additional options for keeping the station crewed. One important criterion for the initial, uncrewed test flights of both SpaceX’s Crew Dragon and Boeing’s Starliner is that crew is aboard the station to monitor systems during docking.

Current schedules place Crew Dragon months ahead of Starliner, in part due to an anomaly that occurred during abort motor testing earlier this year. This makes Dragon the prime candidate for a potential mission to the station. But even with Dragon’s head start, this scenario would require significant acceleration of the SpaceX DM-1 and DM-2 missions, and either an extension of MS-09’s lifetime or the launch of an empty MS-11 spacecraft.

The scenario would play out as follows. NASA would expedite SpaceX’s uncrewed DM-1 flight to launch prior to December. The flight is currently scheduled for no earlier than January 2019, but would be accelerated either due to a modified visiting vehicle schedule or expediting the remaining testing and inspections prior to launch.

DM-1 launches the first Dragon 2 on the uncrewed DM-1 mission to the ISS – via Nathan Koga for NSF/L2

It is understood that the flight hardware, both the Crew Dragon spacecraft and its Falcon 9 launcher, are on track to be ready for launch by December.

The reason for the January launch target is not hardware readiness, but remaining safety checks and inspections paperwork. While these safety procedures, of course, cannot be skipped, they could potentially be accelerated if NASA were to allocate appropriate resources.

DM-1 would then launch in December, uncrewed, and dock to the station. The current station crew would monitor Dragon’s systems, first as it docked, then as it undocked to return to Earth. A successful demo flight would certify Crew Dragon to carry crew aboard the DM-2 mission.

NASA has already considered changing the crewed test flights to operational crew rotation missions: first with Boeing, then, following the Starliner abort motor mishap which delayed Boeing’s flight tests, with SpaceX Crew Dragon.

In order to launch DM-2 to the station prior to Soyuz returning to flight, the current station crew would have to extend their stay in orbit, either by extending MS-09’s lifetime or launching an empty MS-11. Also, the timeline for both DM-1 and DM-2 would have to be significantly accelerated, making this scenario extremely unlikely.

Starliner and Dragon 2 will take over US crew rotations on the ISS – via Nathan Koga for NSF/L2

Another obstacle to Crew Dragon potentially assisting with ISS crew rotations is human rating her launcher: Falcon 9. NASA requires seven flights of Falcon 9 in the configuration that will carry crew before flying any astronauts.

While the Block 5 iteration of Falcon 9 has flown six missions so far and has more missions scheduled to launch prior to December, none of them have had the upgraded Composite Overwrapped Pressure Vessels (COPVs) that are included in the Commercial Crew configuration.

The COPVs were upgraded to enable an accelerated fueling timeline after the Amos-6 anomaly in 2016, when an uncrewed Falcon 9 exploded on the pad due to COPV failure. Seven flights of Falcon 9s which include the upgraded COPVs would certify the launcher for crewed launches.

In addition to a successful DM-1 mission and seven flights of the upgraded COPVs, SpaceX would also have to complete the Dragon in-flight abort test prior to putting crew aboard. There will be a significant time gap between DM-1 returning to Earth and the in-flight abort test, since SpaceX plans to use the same Dragon spacecraft on both missions.

It is estimated that refurbishment of the spacecraft would take a few months. Only once DM-1 and the in-flight abort are successful, Falcon 9 has flown seven times with the upgraded COPVs, and all of the inspections are completed on the ground will SpaceX be ready to launch a crew to that station. It is not likely this could all occur in the next two months.While odds are SpaceX will not be able to help keep crew aboard the station, they could be affected by an uncrewed station. The uncrewed demo flights for both SpaceX and Boeing require crew to monitor systems during docking. If DM-1 cannot be accelerated to fly while the current crew is in orbit, and Soyuz does not return to flight by December, the Commercial Crew test flights would have to wait until the station is reoccupied.

This could also have implications for the “capture the flag” race between SpaceX and Boeing. The last crew to launch from American soil, aboard Space Shuttle Atlantis on STS-135, brought an American flag to be brought home by the next American-launched crew. A delay to SpaceX DM-1 could mean time for Boeing and Starliner to solve the abort motor issue and progress towards readiness for their own demo flights.

As NASA evaluates its options to keep the ISS crewed, they will also likely adjust schedules for uncrewed cargo missions. Progress 71, which will require a re-certified Soyuz booster to launch, was originally scheduled to launch on October 30.

A Northrop Grumman Cygnus spacecraft, designated NG-10 and launching aboard an Antares rocket from Wallops Island, Virginia, is scheduled to launch to the station on November 15.

Cygnus arriving at the ISS – via Nathan Koga for NSF/L2

A SpaceX Cargo Dragon spacecraft designated SpX-16, launching aboard Falcon 9 from Cape Canaveral, Florida, is scheduled for November 27.

With less crew aboard the station needing consumables, in addition to the normal redundant amounts of supplies sent, these missions will likely not need to launch earlier than currently planned, even if the Progress supply mission is significantly delayed.

The primary focus for NASA in the coming weeks will be the safety of all crew members, whether they are currently in orbit or waiting to launch from the ground. Meanwhile, ground controllers and engineers will take on the difficult and important task of keeping the space station occupied so that the research conducted on the orbital laboratory can continue uninterrupted.

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