Mission 2K2: Burya-Mir, February 1994
Defining the mission
Following the success of mission 2K1 there had been calls within the Soviet government to skip the remaining unmanned test flights and to launch the next mission with cosmonauts on board. Although the engineers at the newly-established Soviet Space Agency (Vsesoyuznyy Kosmicheskoye Agentstvo, VKA - literally the “All-Union Space Agency” [1]) and RKK Energia were gaining confidence with their shuttle, there were practical considerations that argued against rushing ahead. Although spacecraft 2K (Burya) had been fitted with a partially functioning life support system for her maiden flight, she was still missing much of the equipment that would be needed for a manned launch. The most critical of these were the ejection seats and related emergency escape equipment, which the Soviets viewed as being absolutely essential for the first manned missions after witnessing the tragedy of Challenger. The pilot’s control console was also missing, and many of the other control stations were not fully connected to their systems. Less glamorous items such as a functioning galley and sanitation facilities would also have to be added.
Work had re-started on outfitting Buran (spacecraft 1K) to a full crewed capability in mid-1992, but the shuttle was still not expected to be ready until the end of 1994 at the earliest. Bringing Burya up to that standard would take a similar amount of time, meaning no manned launch was likely before the start of 1995. With the Supreme Soviet voting to cancel funding for unmanned Energia-T launches in October 1992, and with the cheaper Energia-M suffering more delays, this would mean a more than two-year gap in Energia launches, exacerbating problems in retaining qualified technical staff and keeping the facilities at Baikonur well maintained. These issues had already led to the decision to mothball Pad 37 and the UKSS test stand, leaving Pad 38 as the only complex from which Energia could be launched. Further cuts could result in the aging infrastructure being unable to support the giant rocket at all.
These realities led to the decision in February 1993 to continue the upgrade of Buran for a targeted first manned mission in early 1995, whilst Burya would undergo a minimal post-flight refurbishment for a second unmanned mission in late 1993. Mission 2K2 (Mission 2 of orbiter 2K) would perform the second part of the activities that had originally been intended as part of 2K1: an automated docking with the Mir space station.
Preparations for launch
Following her landing at Baikonur’s Yubileynyy runway on 30th November 1992, Burya first had her propulsion system drained of residual liquid oxygen, with both oxygen and hydrogen then removed from the fuel cells. The spaceplane was next transferred to the Assembly and Fueling Facility (MZK) for the removal of any remaining fuel and other hazardous liquids. The exhausted batteries were also removed, followed by the extraction of the 37KB and docking modules from the payload bay. On 10th December the shuttle was moved from the MZK to the Transfer Bay of the MIK OK Orbiter Assembly and Test Facility, where a crane lifted Burya and carried her to Bay 102 for inspection and renovation of the thermal protection system.
Inspections of Burya’s thermal protection system revealed five tiles missing (compared with seven on Buran’s initial flight), but many more damaged. Some of this appeared to be the result of ice impacts during launch, but most of the damage to tiles on the belly of the orbiter came from plasma jets generated during re-entry by the aerodynamic effects of gaps between the tiles. The US Space Shuttle avoided this problem by laying its belly tiles at an angle to the direction of flight and using a special ‘gap-filler’ material to make them tight, but the Soviet orbiters placed the rows of tiles perpendicular to the nose, relying on an organic felt filler material and precision placement to keep the gaps too small to generate plasma jets. On Buran this had proved mostly successful, but the cut-backs of the early 1990s had evidently led to a reduction in quality control, with Burya showing evidence of five times as many plasma jets compared with Buran.
The replacement of the damaged tiles and inspections of the rest of the thermal protection system were completed by the end of March 1993, but Burya was to remain in Bay 102 until May. This was due to the next area of the MIK OK, the Assembly Bay 103, being occupied by orbiter 1K Buran, which was undergoing installation of its life support system. The prototype orbiter was eventually moved to the MZK for further work, freeing up Bay 103 for Burya, which was then able to undergo systems checks and minor repair work from its flight six months previously. Burya was next moved to Bay 104 for electrical and control system checks in June before proceeding to the anechoic chamber in Bay 105 for radio systems checks. In August 1993 Burya finally left the MIK OK and moved to the MZK (Buran having relocated back to the MIK OK Bay 102 in July) for fueling in preparation for APU and propulsion system test firings at the Site 254 test stand (the stand’s own propellant fueling systems having been decommissioned the previous year as a money saving measure).
Burya was then forced to wait a further two months in the MIK OK as Energia vehicle 4L was put together in the MIK RN. Tensions between the Ukrainian SSR and the Soviet central government over control of the privatisation of state companies (and the money and powers of patronage resulting from their sale to political allies), including OKB Yuzhnoye, had delayed the delivery of the Blok-A booster rockets from their Dnipropetrovsk factory, and so the stacking of vehicle 4L did not start until October 1993. It was not until early December that Burya was finally moved to the MIK RN and joined to her carrier rocket. Once again, the venerable 37KB instrument module and SM docking module were installed in Burya’s payload bay, but this time they were joined by the 1 tonne Fosvich-2 X-ray telescope, which Burya would deliver to Mir and attach to the lateral docking port of the station’s Kristall module.
Other preparations were also underway for the mission. 6th December 1993 had seen the launch of Soyuz TM-18 to the Mir space station carrying cosmonauts Aleksandr Viktorenko, Yury Usachov and Valeri Polyakov. Polyakov was destined to remain aboard Mir for over a year before returning to Earth with Soyuz TM-20 in January 1995, setting a new record for long duration spaceflight. Conversely, Usachov and Viktorenko were part of a standard 6 month expedition (Mir EO-15), and would return home in Soyuz TM-18 in May 1994. Together, this team would be responsible for supporting Burya’s docking to the station and the subsequent test activities. [2] Viktorenko had been selected to command the station during the 2K1 mission specifically for his experience with the shuttle programme, as he had been selected in 1978 as one of the cohort of shuttle cosmonauts from the Cosmonaut Training Centre (TsPK) at Star City. This training, plus his later experience on the Soyuz TM-3 and TM-8 missions to Mir, made him the ideal candidate to assess the performance of the Burya orbiter.
2K2 Launches
The Burya/4L stack was finally towed to Raskat Pad 38 in late January 1994, almost 14 months after the shuttle’s last launch from the neighbouring Pad 37. Despite the increasingly tough budget cutbacks, the ground crews at Baikonur continued to work with dedication and pride, and with the experience of 2K1 under their belts were able to complete launch preparations even faster than in 1992. With no countdown holds, ignition of the Energia core engines came as planned at 08:57 local time (02:57 UTC) on 7th February, with the four Blok-A boosters following on schedule, lifting Energia 4L from the pad at precisely the time needed to intercept Mir’s orbital plane.
Booster separation came two and a half minutes later, but despite all four Blok-A rockets making successful soft-landings downrange, no immediate attempt was made to retrieve them. The necessary recovery forces were no longer available, and with the low launch rate of Energia coming to be accepted, re-use would simply not be economical. Vehicle 4L would be the last Energia to include recovery equipment in the Blok-As, with future launches using the simpler, stripped-down version of the boosters originally developed for Energia-M.
As on all three previous launches, the core stage RD-0120 engines performed flawlessly, delivering its shuttle cargo into a sub-orbital trajectory eight minutes after ignition. Separation of Burya from the booster and the firing of its DOM manoeuvring engines also occurred as planned, and thirty minutes later TsUP controllers were able to confirm Burya was in a stable parking orbit around the Earth.
With the launch and early orbit operations phase of the mission now completed, the Biser-4 computers comprising Burya’s Central Computing System were commanded to load their rendezvous and docking application software into their RAM from the magnetic tapes of the Mass Memory Unit. This was necessary because the limited memory of the Biser-4 units (equivalent to 524 kB of RAM each) meant that it was not possible to run software for all mission phases at once. The new application installation process had been extensively tested on the ground in the OK-KS electrical analogue and in both Burya and Buran in ground tests, and this testing paid off with all four Biser-4 units successfully transitioning to the new software. This done, the orbiter began its two-day chase of the Mir space station.
Rendezvous and Docking with Mir
The initial orbit adjustment to begin rendezvous with Mir was triggered on Burya’s third orbit on the afternoon of 7th February, involving a short, ten-second burn of the starboard DOM manoeuvring engine. Over the the next day several minor adjustments were made with both the DOM and the smaller RSU Reaction Control System engines to match Burya’s orbit with Mir’s. These manoeuvres were performed automatically without ground intervention, guided by the GSP with updated state vectors derived from the RVV Vertical Radio Altimeter and the PRZS Sunrise/Sunset Detection Instrument. Also during this period, the Docking Module was powered up and its docking tunnel, topped by the APAS-89 port, was extended to its full 5.7m height, ensuring the port interface was clear of the top of Burya’s crew cabin. Finally, APAS-89’s guide ring was extended, putting the docking port into its “active” configuration and its supporting Kurs docking antennas swung into their deployed position.
The shuttle’s Mutual Measurement System (SBI), a radar acquired the space station at a range of 40km, guiding Burya into its terminal approach phase at a distance of 15km on the morning of 9th February. Burya initially approached Mir from below, along the Mir-Earth axis, to take advantage of natural gravitational forces in braking the shuttle. As Burya closed to within 1km it repositioned itself ahead of Mir in its orbital track, aligned with the Kristall module’s own APAS-89 port, Kristall having been repositioned by its Lyappa robot arm to Mir’s forward axial X- port a week earlier to provide better clearance and structural strength for the docking attempt. As a safety measure, cosmonauts Viktorenko, Usachov and Polyakov boarded their Soyuz TM-18 spacecraft and undocked from the station. Burya massed as much as the entire Mir space station, meaning any impact could be catastrophic, and so no chances were to be taken on this initial docking attempt. As a final precaution, Kristall’s large solar arrays were stowed for the final approach to avoid damage from Burya’s RSU engine plumes.
As the three cosmonauts watched from a safe distance, with Burya coming to within 30m of the station, the SBI radar suddenly lost lock, and the shuttle automatically reversed its approach to keep clear of the station. The cosmonauts were ordered to return to Mir whilst TsUP controllers analysed the situation, and it was soon determined that the problem was caused by unexpected multipath interference as the radar reflected and re-reflected from the structure of Mir and the shuttle’s own bulky fuselage. This caused the received signal to degrade below the threshold set by mission rules, triggering an abort. Further investigations overnight showed that it should be possible dock safely using just the Kurs system, and preparations were made to repeat the attempt.
The next day, 10th February, with the station’s crew once again watching nervously from a distance in Soyuz TM-18, Burya began its second approach to the station. This time the shuttle continued past the 30m mark to continue closing on Kristall at a rate of 5cm/s. At 07:39 UTC / 10:39 Moscow Time, as the complex overflew the Soviet-Mongolian border, the latches on Burya’s APAS-89 capture ring engaged with their counterparts on Kristall’s docking port. The latches then closed and the capture ring retracted to enable a hard dock. The Burya-Mir complex was now the largest structure ever assembled in orbit.
Operations at Mir
In the hour following docking, Viktorenko and Usachov performed leak checks of the Kristall docking compartment before equalising the pressure between Kristall and Burya’s Docking Module (SM), after which Aleksandr Viktorenko opened the hatch and entered the SM. Whilst Polyakov remained aboard Mir, Viktorenko and Usachov proceeded onwards to Burya’s Habitation Compartment. As on its previous mission, the compartment was in a heavily stripped-down state, although additional life support equipment had been fitted in the lower deck beneath the BO. The flight deck was also largely identical to its 2K1 configuration, although a check of the RM-5 console at the back of the compartment confirmed what the crew had seen from outside, that Burya was now carrying two SBM robot arms instead of the single arm that had flown in 1992.
Viktorenko was quickly able to establish communications with his comrades on Mir and the controllers at TsUP via Burya’s VHF system, but the SHF ONA-I antenna had difficulty in locking onto the Cosmos 2054 relay satellite due to Mir’s bulk obstructing its field of view. Aboard Mir, Polyakov reported fewer problems with the station’s ONA antenna, placed as it was at the opposite end of the complex from Burya, but communications problems would continue to be a feature of shuttle-Mir missions into the future.
With basic communications established between station and shuttle, the two cosmonauts next ran checks on the 37KB test payload and the Fosvich-2 X-ray telescope via the RM-6 console at the rear of the KO, with Viktorenko confirming the readiness of the two On-Board Manipulator System (SBM) robot arms via the RM-5 console beneath the rear port window, looking out onto the payload bay. With all systems showing nominal performance, the two cosmonauts returned to Kristall having spent almost five hours aboard the shuttle orbiter.
The next day, 11th February, saw Burya deliver its payload to Mir. This time Viktorenko entered the shuttle alone whilst Usachov remained on Mir with Polyakov. Once in place at the RM-5 workstation, with good lighting conditions from both bright sunlight and the floods in Burya’s payload bay, Viktorenko powered up the portside SBM arm and initiated a pre-programmed sequence to position the arm’s end effector above the ‘grab point’ of the Fosvich-2 telescope. With Viktorenko monitoring the whole process through both the RM-5 CRT displays and the payload bay window, over the course of fifteen minutes the SBM correctly moved into position, with the cosmonaut guiding the final capture manually using the arm’s video camera. Following a pause as the station passed over the nightside of its orbit, the return of daylight saw Viktorenko command the release of the payload bay latches holding Fosvich-2 in place, then used the arm to swing the telescope up out of the bay and into position in front of Kristall’s second, lateral APAS-89 docking port.
The next phase of the manoeuvre was the most critical. Kristall’s lateral port was attached to the same docking compartment as the port to which Burya was connected, so any damage to the compartment could block Viktorenko’s route back to Mir. An Orlan-DMA spacesuit had been stowed in the Habitation Compartment in case it became necessary for Viktorenko to spacewalk back to the station, but if the shuttle’s SM Docking Module were also damaged it could be necessary to exit via the portside crew access hatch normally only used on the launch pad. With no convenient handrails to aid an EVA, the space suited Viktorenko would have to assemble a deployable pole in the BO and attach it to the interior of the hatch before extending the structure to form a bridge to the safetly of Kristall.
Fortunately, such extreme contingency measures proved unnecessary, as over the next two orbits Viktorenko successfully mated Fosvich-2’s APAS port with that of Kristall. Initial problems with achieving a hard dock were solved by cycling the power to the latches on the Kristall side (basically, switching it off and on again). At the end of the day, with Viktorenko back on board Mir, Usachov was able to open the hatch to Fosvich-2’s small control compartment and begin wiring up power and control connections. Activation of the X-ray telescope would have to await Burya’s departure and the extension once more of Kristall’s solar arrays, but the shuttle’s first operational payload had been safely delivered.
Undocking and landing
Burya was to remain docked at the station for just three days - a limit set due to the shuttle being configured for just eight-days total endurance, plus the need to keep some margin should there be problems with the de-orbit. The hatches between Kristall’s docking compartment and Burya’s SM were sealed late on 11th February, with depressurisation of the two compartments starting on the morning of the 12th. The latches on the station-side APAS-89 interface were retracted at 07:17 UTC on 12th February, as the complex passed over the Ukraine, and Burya fired its DO vernier engines under automatic control to slowly back away from the station. The cosmonauts aboard Mir reported minimal disruption as the massive shuttle departed, completing validation of Burya’s ability to perform all nominal station support operations. Re-entry and landing followed later the same day, with Burya coming to a halt on the Yubileynyy runway at 10:58 UTC, bringing an end to another successful mission. Although Burya’s stay at the station was brief, the data obtained would prove vital in preparing future shuttle docking missions with Mir, as well as feeding into plans for the station’s successor.
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[1] The VKA is TTL’s equivalent of the Russian Space Agency, created during the reforms of the early ‘90s to distance the technical side of the Soviet space programme from direct political supervision. It remains under the auspices of the Ministry of General Machine Building (MOM) and closely tied to the Defence Ministry.
[2] Various butterflies mean Soyuz TM-18 (and the other Soyuz missions since TM-16) are launched approximately 2 months ahead of their OTL schedule. Aleksandr Viktorenko takes the place of Viktor Afanasyev on Soyuz TM-18.
