Russia’s Soyuz TMA-21/26S spacecraft departed the International Space Station (ISS) today (Friday 16th September) prior to landing in Kazakhstan a few hours later. Soyuz TMA-21, carrying American astronaut Ron Garan and Russian cosmonauts Alexander Samokutyaev & Andrey Borisenko, undocked from the Mini Research Module-2 (MRM-2) Zenith docking port at 12:38 AM GMT, before landing at 4:00am GMT.
Soyuz TMA-21 background:
Launched to the ISS on 4th April with a crew of two rookie cosmonauts and a veteran Space Shuttle astronaut, Soyuz TMA-21 docked to the ISS on 6th April. Soyuz TMA-21 carries a special commemorative “Yuri Gagarin” designation, since the Soyuz TMA-21 mission coincided with the 50th anniversary of Yuri Gagarin’s first foray into space. Soyuz TMA-21 carries special commemorative decals in recognition of Yuri Gagarin.
Upon landing, Soyuz TMA-21 will have completed 162 days on-orbit – 38 days shy of its 200 day orbital lifetime limit.
Originally scheduled to return to Earth on 8th September, Soyuz TMA-21 gained an extra week on-orbit due to the desire to keep the ISS crewed at six people for as long as possible, in light of the suspension of Soyuz flights due to the Progress M-12M/44P launch failure.
It was not possible to keep Soyuz TMA-21 on-orbit for an additional 38 days, so as to use all of its orbital lifetime, since the Soyuz landing site in Kazakhstan becomes too dark to support a landing after 18th September. Adequate lighting will return 40 days later on the 26th October, but Soyuz TMA-21 cannot remain on-orbit until then, since by this time it would have been in space past the preferred 200 day limit.
Undocking and landing procedures:
In the hours prior to undocking on Thursday (15th September) night, the Soyuz TMA-21 spacecraft was powered up and checked out, and Quick Disconnect (QD) clamps that help hold the Soyuz to the ISS were removed. The farewell ceremony and hatch closure between the ISS and MRM-2 then occurred between 9:20 and 9:40 PM GMT.
Leak checks then occurred between the Soyuz and the ISS, and then between the Soyuz Descent Module (SA) and Orbital Module (BO) once hatches were closed between the two modules. Leak checks of the crew’s Sokol launch & entry suits also occurred.
Prior to undocking, the ISS moved to the undocking attitude under the control of Russian thrusters, and free drift was initiated just prior to undocking at 12:38 AM GMT on Friday.
Undocking provided Soyuz TMA-21 with a Delta-V (change in velocity) of 0.12 m/s, a 15 second separation burn with a Delta-V 0.55 m/s was then conducted by the Russian vehicle.
The ISS then returned to its standard Local Vertical/Local Horizontal (LVLH) attitude under the control of Russian thrusters at 12:46 AM GMT.
Roughly 2.5 hours later, Soyuz TMA-21 conducted its de-orbit burn between 3:05:27 AM and 3:09:47 AM GMT. Tri-module separation took place at 3:33:24 AM GMT, following which atmospheric entry commenced at 3:36:43 AM GMT. Following parachute deploy at 3:45:20 AM GMT, the Soyuz TMA-21 SA hit the deck in Kazakhstan at 4:00:22 AM GMT, or 10:00:22 AM Kazakhstan local time.
Notably, after module separation, mission control in Moscow did lose all communication with the crew, prior to one of the recovery planes managing to make contact to confirm the crew were in good shape.
Expedition 29:
Following the undocking of Soyuz TMA-21, the ISS is now in a rare configuration since only two Russian vehicles will be docked to the station – Soyuz TMA-02M/27S at MRM-1 Nadir, and Progress M-10M/42P at Docking Compartment-1 (DC-1) Nadir. The Service Module (SM) Aft port is currently unoccupied due to the failure of Progress M-12M, and the MRM-2 Zenith port will be vacated by Soyuz TMA-21 upon undocking.
The MRM-2 Zenith port will remain vacant for around two months, until the arrival of the delayed Soyuz TMA-22/28S, and the SM Aft port will remain vacant until the arrival of Europe’s Automated Transfer Vehicle-3 (ATV-3) on 19th March 2012.
With Expedition 28 Commander Andrey Borisenko having handed over command of the ISS to US astronaut Mike Fossum yesterday, the undocking of Soyuz TMA-21 will mark the official end of Expedition 28 and the beginning of Expedition 29.
However, instead of the usual two week period of three crewmember operations that usually occurs during crew rotations, Expedition 29 will be at three crewmembers for around eight weeks until the arrival of Soyuz TMA-22 with an additional three crewmembers. However, the resulting six crew period will be short lived, since Soyuz TMA-02M, carrying three crewmembers, will have to depart the ISS less than one week after Soyuz TMA-22 arrives.
Expedition 29 will then remain at three crewmembers until the arrival of Soyuz TMA-03M/29S around one month later.
Progress M-12M failure investigation status and recovery plan:
Last week, the Russian space agency, Roscosmos, announced that the cause of the Progress M-12M launch failure had been identified. Investigators found that a blocked fuel line leading to the gas generator of the Soyuz-U booster’s third stage RD-0110 engine caused the gas generator, which drives the engine’s turbopump, to lose pressure, and in response the engine automatically shut down as designed.
Although defined as a “random” failure, the blocked fuel line has led to Roscosmos taking the decision to ship all Soyuz booster third stages back to their manufacturing plant for a thorough check-up, to verify that the issue was indeed a one off. This decision has impacts for the future schedule of ISS resupply and crew rotation flights.
A “tentative” schedule of future Soyuz spacecraft launchings and landings and Progress resupply craft launchings was agreed today by the Space Station Control Board, which represents all the International Partners of the ISS. After hearing Roscosmos’ findings from the Progress M-12M failure, the following was agreed, with the caveat that changes may be made “to reflect minor changes in vehicle processing timelines”.
The first Soyuz booster launch will serve as an uncrewed test of the Soyuz booster, and as an ISS resupply flight. A Soyuz-U booster will loft the Progress M-13M/45P spacecraft on 30th October, for a docking to the ISS at the DC-1 Nadir port on 1st November.
Progress M-10M/42P, which is currently docked to DC-1, will undock on 29th October, one day prior to the Progress M-13M launch, resulting in a brief period of the ISS being placed in the very rare configuration of only one Russian vehicle docked at the outpost (Soyuz TMA-02M at MRM-1).
Providing the Progress M-13M launch is successful, the next launch will be a crewed Soyuz-FG booster with Soyuz TMA-22/28S on 14th November, for a docking to the ISS at the MRM-2 port, soon to be vacated by Soyuz TMA-21, on 16th November. This represents a nearly two month delay for Soyuz TMA-22, which was originally scheduled to launch on 22nd September.
Following the Soyuz TMA-22 docking, the Soyuz TMA-02M/27S undocking from MRM-1, originally scheduled for 16th November, will occur on 22nd November – leaving less than one week of handover time between the Soyuz TMA-22 and Soyuz TMA-02M crews.
It is understood that a 22nd November undocking of Soyuz TMA-02M would result in acceptable lighting conditions at the Kazakhstan landing site by way of a dawn landing.
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The next launch to the ISS will then occur around 26th December, when a Soyuz-FG booster will loft Soyuz TMA-03M/29S, for a docking to the ISS at the MRM-1 port on 28th December, putting the ISS back up to six crewmembers with the beginning of Expedition 30.
The delay of Expedition 30 is expected to result in SpaceX’s C2/C3 Dragon demo mission being delayed to January or February 2012, since the originally scheduled launch date of 30th November would result in a 9th December ISS arrival date for Dragon, a time when only one trained US crewmember would be available on the ISS, when free-flyer capture and berthing operations require two trained crewmembers.
Finally, a Soyuz-U booster would loft Progress M-14M/46P on 26th January, for a 28th January docking to DC-1, which will have been vacated by the undocking Progress M-13M on 25th January.
Resupply flights, however, are not the driving concern in the schedule, since enough supplies exist on the ISS for six crewmembers to reach summer 2012 without receiving any resupplies.
The driving issue is crew safety, with NASA ISS Program Manager Mike Suffredini noting “Our top priority is the safety of our crew members. The plan approved today, coupled with the conditions on orbit, allow the partnership to support this priority while ensuring astronauts will continue to live and work on the station uninterrupted.
“Our Russian colleagues have completed an amazing amount of work in a very short time to determine root cause and develop a recovery plan that allows for a safe return to flight. We’ll have a longer period of three-person operations and a shorter than usual handover between the next two crews, but we are confident that the crews will be able to continue valuable research and execute a smooth crew transition”.
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