Russia’s Multipurpose Laboratory Module (MLM) Nauka, meaning “science,” has defied the odds to successfully dock to the ISS after a long and arduous journey dating back over 20 years and a problematic propulsion system after launch which had threatened the success of the mission.
The docking was not without issue, with Russian cosmonauts noting that Nauka wasn’t on the correct course less than an hour before docking; however, a retro burn quickly corrected the issue. After also troubleshooting an issue with the TORU manual docking system, Nauka successfully docked in automated fashion to the Zvezda service module’s nadir port at 09:29 EDT / 13:29 UTC, marking the first major expansion to the Russian segment for over 20 years.
UPDATE — July 29, 5:34 EDT / 21:34 UTC
At 12:34 EDT / 16:34 UTC, the ISS’s systems registered a divergence from the nominal attitude orientation. The station’s gyros attempted to correct the attitude error but couldn’t.
At 12:42 EDT /16:42 UTC, the ISS’s attitude departure exceeded limits and a Loss of Attitude emergency was declared, giving NASA and the ISS top priority through the TDRS (Tracking and Data Relay Satellite) communications network in geostationary orbit.
At this time, the ISS was commanded to free-drift, the gyros were shutdown, and emergency control was handed to the Russian segment and the Zvezda service module. Zvezda likewise tried to correct the orientation of the Station, fighting against Nauka as the new module continued to fire its thrusters.
The ISS. (Credit: NASA)
Over the next 45 minutes, Russian controllers attempted to cease the thruster firings from Nauka, which were occurring without command. During this event, the ISS attitude movement never exceeded 0.5 degree per second and the crew did not feel the event.
according to Russian media reports, Nauka burned through its remaining fuel during this thruster event.
At 13:29 EDT / 17:29 UTC, with Nauka’s thrusters no longer operating, Russian controllers were able to use Progress MS-17’s thrusters to get the Station back in attitude control and returned to a stable orientation.
As a result of the need to evaluate the station, Starliner’s OFT-2 mission, which was scheduled to launch on 30 July, has been postponed to no earlier than Tuesday, 3 August 2021 at 13:20:10 EDT / 17:20:10 UTC.
UPDATE — July 29, 1:53 EDT / 17:53 UTC
After successfully docking to the station, roughly three hours later at 12:45 EDT / 16:45 UTC after cosmonauts had opened Zvezda’s hatch to Nauka, the new module suddenly began firing its thrusters without command.
This caused the ISS to leave its nominal orientation and end up 45 degrees out of alignment.
Immediately, Russian mission controllers detected the issue and Zvezda began firing its own thrusters to try and correct the issue. However, Nauka’s thrusters kept firing erroneously, and the two modules were essentially fighting each other, with Nauka pushing the ISS out of alignment and Zvezda trying to but not being able to fully correct.
At this same time, NASA ordered the Station into free-drift to alleviate stress on the modular attach points across the outpost.
NASA TV, Rob Navias, updating the situation now. Thread⬇️
– Zvezda's hatch was opened and crew was in process of getting things up and running when at 12:45pm EDT, Nauka began firing uncontrolled. ISS 45 degrees out of attitude. NO DANGER TO CREW! 1/x— Chris G – NSF (@ChrisG_NSF) July 29, 2021
MCC-Moscow then switched Zvezda’s thrusters off and used Progress MS-17’s thrusters instead to correct Station attitude.
Eventually, Russian controllers were able to get Nauka’s thrusters to stop firing; a more permanent disabling of the thrusters will be achieved when the ISS passes back over Russian ground stations.
At this time, there is no indication of damage to the International Space Station and all systems on the ISS are operating normally.
What effect this might have on Starliner’s planned launch on Friday, 30 July is not yet known.
Nauka docking
Immediately after a successful orbit insertion of 190 x 350.1 km, issues with the module’s communications and propulsion systems were noted. Initial troubleshooting was complicated by limited communications during brief periods when the module came within range of Russian ground stations.
The communications issues were resolved in initial orbits; however, the propulsion system issue was more troublesome and believed to be related to a part of the module’s fuel supply being rendered unusable due to gases becoming mixed with the fuel for the main engine.
Reports indicated that pressure in the main engine’s propulsion tanks had risen to unacceptable levels due to an earlier-than-planned equalization of pressure between the tanks. Thus, use of the smaller engines would be needed to relieve tank pressure to a point where the main engine could be used.
The EDL phase of a Mars mission is often referred to as "7 minutes of terror”. After #Nauka launch, the entire Russian space community experienced what I can call “8 days of terror”. But now it’s almost over! Let’s watch Nauka docking today at 13:26 UTC: https://t.co/LTfTe7XFch pic.twitter.com/eMufXKVsun
— Katya Pavlushchenko (@katlinegrey) July 29, 2021
That, coupled with continuous limited communications, resulted in several of the initially-planned orbit raising burns being cancelled and then later conducted using the module’s secondary engines.
These replanned first burns were enough to prevent Nauka from reentering the atmosphere within a few days, as was the fear given the low perigee insertion of 190 km. With those first burns, Russian controllers were able to stabilize Nauka, get the main engine working, and keep the module on track for a 29 July arrival at the Station as originally planned.
Approaching the ISS, Nauka used its KURS automated rendezvous system as intended; however, the module was also equipped with a TORU manual docking system, which would have enabled cosmonauts Novitsky and Dubrov aboard the ISS to take control of Nauka and fly it manually if needed.
For the docking, the ISS was placed in a special attitude – essentially pitched up 90 degrees – in order to place Nauka’s docking axis along the velocity vector. This was not the original plan, which would have seen Nauka approach up the R-bar, or Radial velocity vector, with the nadir Zvezda port facing straight down at Earth.
The ISS orientation plan for docking was changed to accommodate Nauka’s as-is condition after launch.
Docking was made to Zvezda’s nadir docking port, which was recently vacated by the Pirs module on 26 July. This port uses a docking system called the Hybrid Drogue Adapter (HDA).
Nauka, just before encapsulation for launch. (Credit: Roscosmos)
HDA is a Russian system which is essentially the combination of the traditional Probe & Drogue (SSVP) system and the Androgynous Peripheral Attachment System (APAS), on which the docking system of Dragon and Starliner is now based.
Specifically, HDA uses the docking collar from the APAS system, but rather than use a capture ring as is the case on the US segment, it instead uses a docking drogue as found on the SSVP system. This enables dockings to occur the same way as they do for Soyuz/Progress vehicles but gives a wider passageway through the hatch, which is useful for permanent modules.
Following docking and hard capture, the next immediate steps will be leak checks and vestibule pressurization followed by hatch opening, first ingress, and module activation.
Future plans:
A total of up to 11 spacewalks will be required in order to fully outfit and commission Nauka, with the first of these set to be performed in September.
Externally, after the module has been connected to the ISS via a series of cables, the first order of business will be to deploy the European Robotic Arm (ERA), which launched attached to the outside of Nauka.
This will involve removing external covers and launch restraints, following which the arm will be activated and fully checked out from the ground. ERA needs to be fully operational in order to proceed with the next phase of operations – which is transferring an airlock and radiator to Nauka.
This radiator and airlock were launched to the ISS attached to the outside of the Mini Research Module-1 (MRM-1) Rassvet on the STS-132 mission in May 2010 by Space Shuttle Atlantis. For the past 11 years, they have waited patiently for the arrival of Nauka.
The deployable radiator will be used to add additional cooling capability to Nauka, which will enable the module to host more scientific experiments. The airlock will be used only to pass experiments inside and outside the module, with the aid of ERA — very similar to the Japanese airlock on the US segment of the station.
The ERA will be used to remove the radiator and airlock from MRM-1 and transfer them over to MLM – with an extension boom being required to allow ERA to reach the airlock. This process is expected to take several months. A Portable Work Platform will also be transferred over, which can attach to the end of the ERA to allow cosmonauts to “ride” on the end of the arm during spacewalks.
Nauka also features a docking port on its nadir which other modules/vehicles can dock to. This port is also of the HDA type (passive side), however it features a special adaptor in order to convert it into a traditional Probe & Drogue port. This adapter converts the APAS docking collar into an SSVP docking collar, which will enable Soyuz and Progress vehicles to dock to MLM.
An internal cut-way showing the layout of Nauka. (Credit: Roscosmos)
In November, Russia will launch the Node Module (NM) Prichal to the ISS, which will dock to the nadir port of Nauka and will add a further four HDA-type ports to the Russian Segment for future expansion – although any expansion plans are now somewhat up-in-the-air following Russia’s decision to focus their future efforts on constructing their own station to succeed the ISS, possibly in cooperation with China.
Prichal will dock to Nauka using the HDA system, which will first require the removal of the HDA-to-SSVP adapter ring from the nadir port of Nauka.
This ring was therefore added as an “insurance policy” in case Prichal failed to make it to orbit, which would have rendered Nauka’s nadir HDA port useless as Soyuz and Progress vehicles would not have been able to dock to it which would have left the Russian Segment with only three usable docking ports.
The first docking to Nauka is planned for September 28, when Soyuz MS-18 will be relocated from Rassvet to Nauka’s nadir port in order to clear Rassvet for the arrival of Soyuz MS-19. MS-18 will then depart Nauka on October 17, whereupon Progress MS-17 will be undocked from MRM-2 Poisk and relocated to Nauka on October 27.
Assuming Prichal is successfully launched on November 24, Progress MS-17 will then undock from Nauka, taking with it the APAS-to-SSVP adapter ring, which will convert Nauka’s nadir port back to HDA configuration ready for the arrival of Prichal.
The planned configuration of ISS after Nauka and Prichal are attached. (Credit: Roscosmos)
In future, it will be standard practice to dock Soyuz vehicles to the nadir ports of Rassvet and Prichal and dock Progresses to the aft port of Zvezda and the zenith port of Poisk.
This is because the transfer chamber which connects to Zvezda’s aft port has a small leak which requires the hatches to remain closed as much as possible, which would block access to a Soyuz if it were docked to Zvezda’s aft port. In addition, Progress crafts are preferred for Zvezda’s aft port as this enables them to perform ISS reboosts using their main engines.
Progresses are also preferred for the Poisk zenith port as Poisk is now serving as the Russian Segment’s airlock following the departure of Pirs, and access to Soyuz craft docked to Poisk is blocked whilst Poisk is depressurized during spacewalks, which presents safety issues in an ISS evacuation scenario.
(Lead image: Nauka arriving at ISS. Credit: Mack Crawford for NSF/L2)