Progress M-05M replenishes ISS – NTA back to full working order

Following its launch on a Russian Soyuz-U launch vehicle from the Baikonur Cosmodrome in Kazakhstan on Thursday, the resupply ship Progress M-05M has docked with the International Space Station (ISS) on Saturday. The orbital outpost also received a boost on Friday, when a valve on a Nitrogen Tank Assembly (NTA) – associated with the recently delivered Ammonia Tank Assembly (ATA) – finally opened.

Progress M-05M:

Launching with supplies of propellant, food, water and consumables, as well as hardware for the Russian and the US segments of the ISS, Progress M-05M was the 37th Russian logistics spacecraft launched to ISS, and the fifth spacecraft in the new series which sports improved performance.

The unmanned vehicle is designed to automatically dock with the Station. However, due to a problem with the vehicle’s KURS autopilot, Expedition 23 commander Oleg Kotov took control via the TORU system and manually docked the Progress with Pirs docking compartment.

The Progress was manifested with 2395 kg (5280 lbs) of cargo, specifically: 870 kg (1,918 lbs) propellants, 50 kg (110 lbs) oxygen & air, 100 kg (220 lbs) water and 1375 kg (3,031 lbs) spare parts & experiment hardware.

“Prop in the propulsion system tanks 870kg. Gas in the oxygen supply system containers  – oxygen 50kg. Water in the Rodnik system tanks 100kg,” listed Roscosmos. “The items in the cargo compartment 1318kg Equipment for the systems: gas supply system 33kg, water supply system 73kg, on-board hardware control system 5kg.

“Telemetry data system (BITS2-12) 2kg. Thermal control system 6kg. Telephone and telegraph system 2kg. Onboard computer system 3kg. Maintenance and repair equipment 5kg. Sanitary and hygienic items 71kg. Food containers, fresh products 325kg. Medical equipment, linen, personal hygienic and prophylactics items 155kg.

“On-board documentation files, crew provisions, video- and photo-equipment 35kg. Equipment for Russian crew members 42kg. Stored items (kit 9) 5kg. FGB-hardware 64kg. MRM2-hardware 53kg. USOS hardware 420kg. Total mass of the cargo delivered 2588kg.”

NTA Solution:

Thanks to patient troubleshooting by ISS controllers, a stuck NTA valve was finally opened on Friday, allowing for the re-pressurization of an ammonia coolant loop that was central to the recent STS-131 mission.

STS-131 Specific Articles:

During Discovery’s mission – which successfully installed a new ATA on Station -  ground teams were unable to open the NTA’s GPRV (Gas Pressure Regulating Valve), which has been integrated with the new ATA.

The NTA supplies pressure to the ATA, which in turn feeds the ETCS (External Thermal Control System) Loop A. NH3 (Ammonia) is supplied to the ETCS via the ATA when there are volume changes in the system due to varying thermal conditions.

With spare NTAs on the ISS, managers considered, and then rejected, the idea of utilizing a fourth EVA to changeout the system. That proved to be the correct decision.

“THOR conducted part 6 of the Loop A NTA GPRV Troubleshooting Friday morning. This part was to turn on the GPRV and then Open NTA Isolation Valve 1 to allow the launch pad of N2 to flow back to the GPRV to try to ‘shock it’,” noted memos acquired by L2.

“This was a repeat of what was already tried using the launch N2 pad from Tank 2. So no one really expected the troubleshooting to work. However, it did. When the valve was opened the pressure at the GPRV went up, then started to go down (which was expected with a GPRV stuck in vent), but then after about 40 seconds, the pressure started increasing towards the setpoint!

“The on-console team has pressurized (just enough to unseat it and force all of the NH3 to liquid) and isolated ATA Tank 2 (per the pre-19A plan). They are currently in the process of fully pressurizing Tank 1 and integrating it into the main Loop A system. At the end of those operations the GPRV will be powered off to protect against the GPRV getting stuck at an end of travel position (one of the legs on the fault tree).”

A managerial overview memo also outlined that a confirmed root cause is still outstanding on why the valve was initially problematic, whilst congratulating the team for their efforts.

“Big Picture: The EATCS Loop A NTA GPRV has been recovered and Loop A has been pressurized, continuing to run nominally.

“THOR performed additional troubleshooting on the Loop A GPRV. This troubleshooting cold soaked the GPRV for ~24hrs and ‘shocked’ the valve with ~130kPa of N2 that was residual in some of the plumbing, left over from before the R&R. This recovered the GPRV function.

“They then pressurized ATA Tank 2 and isolated the tank (nominal config). Next they pressurized ATA tank 1 and integrated into the loop. Finally the pressurized Loop A and isolated the NTA (nominal config). This troubleshooting may not point exactly to a smoking gun, but it is believed that thermal issues and the planned venting before the ATA R&R may have driven the valve to the full open position where it got stuck.”

Some additional work is required – such as re-balancing the heat loads between Loops A and B – although the success means STS-133 is freed from what was already pre-emptive work associated with an NTA task, despite being a packed mission already, along with no further work toward a Stage EVA with Expedition 23 flight engineers Timothy Creamer and Tracy Caldwell Dyson.

“THOR and their engineering counterparts have worked long and hard to get to this point,” added the memo. “Also, many other disciplines have assessed other options if the GPRV could not have been recovered. Congrats to the team on a job well done!”

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