The Russian Soyuz TMA-20M spacecraft has returned Expedition 48 Commander Jeff Williams, along with Soyuz Commander Alexey Ovchinin and Flight Engineer Oleg Skripochka of Roscosmos, to Earth on Tuesday. The spacecraft successfully undocked from the International Space Station at 21:51 UTC, before successfully landing on the steppes of Kazakhstan at 01:13 UTC.
Launched by a Soyuz-FG rocket from pad No. 1 at Baikonur in March, Soyuz TMA-20M was the 129th flight of a Soyuz vehicle, the first of four crew transportation missions to the Space Station in 2016.
The spacecraft completed its fast-track journey to the orbital outpost via an automated docking with the zenith port of the Poisk docking module.
During their six-month mission, Williams served as Commander of Expedition 48, with Ovchinin and Skripochka serving as Flight Engineers.
The Expedition 48 crew members contributed to hundreds of experiments in biology, biotechnology, physical science and Earth science during 172 days in space for the crew.
Highlights of Williams mission included the installation, inflation and ingress into the Bigelow Expandable Activity Module (BEAM).
BEAM – launched in the trunk of the CRS-8 SpaceX Dragon – is a technology demonstrator, with the challenges providing engineers with lessons learned ahead of moving on to larger expandable modules.
The larger modules are likely to play a huge role in the exploration of deep space.
The BEAM module is hoped to be a stepping stone designed to gain useful in-flight experience of how expendable technology works with human spaceflight activities before the notional launch of the two B330 modules at the beginning of the next decade.
The first of two IDAs, this piece of hardware is designed to convert the US Segment’s old Shuttle-era docking ports to a new docking system, thus allowing them to accept the upcoming commercial crew vehicles which will all use the updated docking system design.
Williams only recently completed a second spacewalk, joining forces once again with Kate Rubins, as the duo completed EVA-37.
The spacewalkers successfully stowed a now unused spare radiator and also installed the first two hardware elements of a new system of external HD television camera.
Williams’ conclusion to his mission also saw him eclipse the record set by Scott Kelly for the most cumulative time spent by a NASA astronaut in space.
Williams returned to Earth having accrued 534 days in space on his four missions dating back to 2000, the most days by any US astronaut in history.
Preparations for departure began several days ago. This included a checkout on the crew’s ride home.
“In preparation for departure, the Crew successfully completed a thruster test on the vehicle. This was the first Soyuz thruster test conducted in Control Moment Gyroscope (CMG) Momentum Management (MM) control,” noted L2 ISS Status.
“By utilizing CMG MM for the thruster test, there is a potential to save approximately 5-20kg of propulsion during each thruster test.”
The crew then parted ways with their colleagues during Tuesday, with farewell speeches and hatch closures between the Station and the Soyuz.
With the crew completing the translation from the Orbital Module (BO) and Descent Module (SA) to strap themselves into their Kazbek couches inside the SA, Soyuz TMA-20M undocked from the ISS at 21:51 UTC.
Expedition 49 began aboard the station under the command of Anatoly Ivanishin of Roscosmos as the Soyuz departed.
Along with his crewmates Kate Rubins of NASA and Takuya Onishi of the Japan Aerospace Exploration Agency, the three-person crew will operate the station for more than two weeks until the arrival of three new crew members.
Shane Kimbrough of NASA and cosmonauts Sergey Ryzhikov and Andrey Borisenko of Roscosmos are scheduled to launch on September 24.
Following undocking, Soyuz enjoyed a few hours of free flight as it departed from the Station’s neighborhood via two separation burns while the onboard crew prepared for the final aspect of their mission.
The deorbit burn occurred at 00:21 UTC, reducing the Soyuz’s velocity just enough for it to begin the plunge back to Earth.
The Soyuz then entered a critical part of its mission as the spacecraft has no other option but to re-enter.
The first milestone was the module separation as the three major elements of the Soyuz spacecraft – the OM, DM and Instrumentation/Propulsion Module (IPM) – were pushed apart via the use of pyrotechnics.
All three modules nominally separate simultaneously – shortly after the deorbit burn is completed – at around 140 km altitude.
Two “off nominal” re-entries occurred in 2007 and 2008 and were the cause of separation failures on the modules, thus initiating a very stressful return for their three-person crews.
Known as “ballistic entry” – the crew have to endure much higher G-forces and land at an alternative site.
An investigation (L2 Russian Section) noted issues with the long-term exposure to electromagnetic emissions on-orbit, and the potential to cause issues with the pyro bolts, came after an extensive investigation that included the removal and return of one pyro bolt from Soyuz TMA-12.
Mitigation against this issue has resulted in no further issues with the module separation milestone in any of the following missions.
Once through the plasma of entry interface, the capsule was prepared for the deployment of its drogue chute. This prepared the spacecraft for the deployment of its main parachute.
This is one of the hardest parts of the return for the crew, which has been described as being inside a washing machine by some returning astronauts.
The Soyuz TMA-20M craft then completed the return to terra firma, landing on the steppes of Kazakhstan at around 01:13 UTC.
The exact timing of touchdown, under a “soft” thruster engine firing, is always dependent on a number of factors – such as the impact of winds on the Soyuz chutes – and can vary by several minutes.
With TMA-20M safely back on Earth, ground and air crews converged on the Soyuz to extract the crew from the SA.
The crew underwent immediate and preliminary health checks once outside their Soyuz spacecraft. All three were then transferred to a medical tent to prepare them for transit away from the landing site.
Eventually, they will part ways for their respective countries and space agencies.
(Images: NASA, Roscosmos, ESA and L2.
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