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Progress M-27M mission
The Progress M-27M spacecraft (production No. 426) was the second Russian cargo vehicle to fly to the International Space Station, ISS, in 2015 to re-supply crew onboard the outpost. It was also the 150th Progress spacecraft and the 59th Russian cargo flight to the ISS, known as P59. The mission ran into severe problems immediately after reaching orbit.
Ground track and launch profile for Progress M-27M mission on April 28, 2015.
Launch and ride to orbit
The liftoff of a Soyuz-2-1a rocket took place as scheduled on April 28, 2015, at 10:09:50 Moscow Time (3:09 a.m. EDT, 07:09 GMT) from Pad No. 6 at Site 31 in Baikonur. The launch vehicle carried the 7,290-kilogram Progress M-27M spacecraft bound to the International Space Station, ISS. Following a standard ascent, the spacecraft separated from the third stage of the launch vehicle eight minutes 45 seconds after the liftoff.
According to NASA, following the separation from the launch vehicle, the Progress M-27M successfully deployed its power-generating solar arrays and a trio of communications antennas. However, the mission control in Korolev was not able to confirm a successful opening of a pair of the Kurs rendezvous antennas onboard the vehicle and the pressurization in one of two manifolds of the propulsion system. At the time, the telemetry from the spacecraft became sporadic. (The failure of the main computer onboard the spacecraft was also confirmed based on fragments of telemetry, a mission control source later said.) The radio system of orbital parameters also indicated that an apogee (highest point) of the Progress' orbit was 40 kilometers higher than normal. At the time, representatives of RKTs Progress, the Soyuz rocket manufacturer, told members of the State Commission overseeing the mission that the orbital insertion had gone as scheduled and the radio-control system had miscalculated orbital parameters.
As a result, the mission was immediately switched to a longer, 34-orbit rendezvous profile with the ISS, which would give ground controllers extra time to troubleshoot the issue. If they could resolve all the problems, the docking of the cargo ship at the station would take place around 5:03 EDT on April 30, NASA said.
After the second orbit, representatives of RKTs Progress admitted to the State Commission that they had not seen a signal confirming the separation between the third stage and the spacecraft due to loss of telemetry. The higher-than-normal orbital parameters, which were announced 1.5 hour earlier, turned out to be real.
Before the end of the day, engineers concluded that one propulsion system manifold onboard Progress responsible for the rendezvous maneuvers had lost pressure, making the trip to the station impossible. Ground control still hoped to activate the second manifold, normally used to deorbit the spacecraft, which appeared to be in order. Its thrusters could be used to stabilize the spacecraft and to perform a controlled deorbiting maneuver.
However, during four passes within range of Russian ground stations on April 28, mission control was not able to confirm the status of onboard systems. A video downlinked from the spacecraft around 16:00 Moscow Time, during a third pass over Russia (but the 4th revolution of the mission) showed a very fast rotation of the vehicle:
Russian ground controllers estimated the rotation rate at one full circle every three seconds, which would explain the sporadic telemetry.
According to NASA, at the very end of the communication window, Russian ground controllers sent commands to the Progress to stop its spin, but had no chance to see any effect from the action. The fourth and final communication session on April 28 also produced no visible results.
Next opportunity for Russian flight controllers to communicate with the spacecraft would come on April 29, 2015, at 03:50 Moscow Time during a 15- or 16-minute window, TASS reported.
Initial fragmentary data available about the accident quickly led to questions about the performance of the launch vehicle. The telemetry from the third stage of the Soyuz-2-1a rocket apparently stopped coming 1.5 seconds after the GK-3 command, which cuts off the RD-0110 engine onboard the rocket. The telemetry showed that the pressure in the combustion chamber of the engine started falling (as expected). However the spacecraft separation command, which was to come 3.3 seconds (plus/minus 0.3 seconds) after the GK-3 command, was never confirmed. The flow of data from a telemetry system located between oxidizer and fuel tanks on the third stage and transmitted via four antennas along two communications channels stopped within a fraction of a second from each other at T+526 seconds in flight.
The separation command was supposed to activate three dual pyrotechnic locks connecting the top edge of the third stage with the basis of the Progress. Three spring-loaded pushers would gently push the spacecraft away along 33 pins 0.13 seconds after the separation command. Four sensors would confirm the separation, which is known as separation contact or KO.
According to Russian mission control sources, who applied several different methods to measure the actual orbital parameters after the launch, the spacecraft entered a 193.85 by 279.15-kilometer orbit, which was higher than expected, but far from being fatal for the mission.
According to the mission control in Korolev, following the separation from the third stage at 10:18:38 Moscow Time, the Progress M-27M was expected to enter a 193 by 238-kilometer orbit, where it could remain for no less than 20 revolutions around the Earth or around 30 hours without any additional maneuvers, before naturally decaying into the Earth's atmosphere.
However, NORAD data indicated much more severe deviation (120.5 by 316.4 kilometers) or 70 kilometers up and down, which many Russian observers believed to be erroneous. By the time the flow of telemetry from the Progress was interrupted few seconds before the separation of the spacecraft from the rocket, its orbit was around 38 or 39 kilometers off the mark at its apogee, even though the rocket should've been capable of delivering its cargo within five kilometers from a prescribed altitude.
Despite some suspicions about the performance of the rocket, TV images downlinked from Progress at the time of the separation from the third stage appeared to show a stable flight. If correct, something else had to happen to send the spacecraft into a spin. It was also suggested that during the first TV transmission, the camera was actually off, delivering just a black square.
Still, at the end of the day, the Interfax news agency quoted an unnamed source as saying that a botched separation between the spacecraft and the third stage of the Soyuz-2-1a rocket had been a culprit.
According to one hypothesis, the separation between the spacecraft and the rocket was somehow delayed, causing it to coincide or take place after the opening of the depressurization valve on the oxidizer tank of the third stage, which is normally programmed to take place four seconds (plus/minus 0.3 seconds) after the GK-3 command.
The pressurized gas escaping from the rocket causes its body to spin and could take the spacecraft with it if it was still connected to the stage at the time. Still, the separation would have to take place somehow and some thrust would have to be applied to both vehicles taking them as far as 40 kilometers in separate directions. A possible collision resulting in an explosion could also explain a presence of at least 44 fragments detected by NORAD near the spacecraft.
Also, by the evening of April 28, NORAD updated orbital elements for the Progress M-27M mission, which finally came to a virtual agreement with the previously available parameters from Russian tracking means: a 188- by 260-kilometer orbit with an inclination 51.65 degrees toward the Equator.
Planned and actual orbital parameters for Progress M-27M mission:
First three revolutions of the ISS around the Earth on April 28, 2015.
An interpretation of info screens transmitted by cameras onboard Progress M-27M right after reaching orbit (top) and during its 3rd orbit (bottom) provides clues about possible failure of the attitude control system and massive consumption of onboard propellant.
Another attempt to communicate with Progress M-27M was apparently made during the mission's 13th orbit, in the early hours Moscow Time, however it was also fruitless. The spacecraft likely continued tumbling in space. The new communication window opened around 05:00 Moscow Time (10 p.m. EDT on April 28), however again produced no results. A total of six attempts were made during the day, all failed.
Specialists sent commands to the spacecraft to stop its rotation, but they failed even though the thrusters were activated, mission control sources said. The damage to propellant supply lines was suspected as a result and an attempt to switch to a backup propellant manifold did not work either. Plans to use manual remote-control system, TORU, to control the spacecraft were dropped as well. The Russian space officials then formally concluded that the controlling the spacecraft would not be possible, but monitoring of its orbit continued with the use of radio systems.
According to a press-release issued by the Join Functional Component Command for Joint Space Operations Center at Vandenberg Air Force Base in California, it made first observation of the Progress M-27M at 3:04 a.m. EDT and established that the spacecraft had been making one full rotation every five seconds.
According to NASA, during the day, the mission control in Korolev also asked the current ISS crew to try to photograph the stricken ship as it passes 170 kilometers below the station around 8:30 p.m. EDT. NASA also said that a previous night, Russian ground controllers had been able to establish communications with the vehicle and review telemetry. Russian controllers configured the refueling system to feed the thrusters (editor's note: in the remaining manifold) and made two unsuccessful attempts to command the thrusters to stabilize the vehicle’s angular rotation, NASA said.
During the night from April 29 to April 30, Gennady Padalka photographed the Progress M-27M and sent images to mission control, however their resolution was far from enabling to discern any external damage to the spacecraft, Interfax reported.
On April 29, various estimates put the reentry of Progress M-27M into the Earth's atmosphere between May 3 and May 11, 2015. The Russian mission control predicted the plunge between May 5 and May 8. A preliminary estimate issued by US military predicted the reentry on May 9. In the meantime, the third stage, which delivered the Progress M-27M into orbit, reentered the atmosphere on April 29 without an accident and so did most of the debris associated with the launch.
On May 4, US military predicted the reentry of Progress M-27M on May 8, 2015, at 13:13 GMT during the mission's 167th revolution around the Earth. If any debris of the spacecraft would survive the reentry, they would fall in the Pacific off the US West Coast.
On May 5, US military issued another prognosis advancing the reentry time to the 166th orbit of the Progress M-27M mission on May 8, 2015, at 12:17 GMT. In the meantime, specialists at the Mission Control in Korolev still maintained communications with the crippled spacecraft using its radio signals for orbit tracking and the reentry time predictions.
On May 6, Roskosmos issued a statement predicting the reentry of Progress M-27M on May 8, 2015, between 01:23 Moscow Time (6:23 p.m. EDT, 22:23 GMT on May 7) and 21:55 Moscow Time (2:55 p.m. EDT, 18:55 GMT). The agency promised a more accurate forecast 24 hours before the event and a possible impact area for its debris. Only small fragments of the structure can reach the Earth's surface, Roskosmos said. Around the same time, US military issued a prognosis for a decay on May 8 at 08:59 GMT (4:59 a.m. EDT) during the 164th orbit of the Progress M-27M mission. As of May 6, Progress M-27M was orbiting the Earth in a 166 by 193-kilometer orbit.
By May 7, US military moved forward the reentry prediction for the Progress M-27M mission by four revolutions, now forecasting the event on May 8, at 03:32 GMT, during mission's 160th orbit. A powerful magnetic storm on the Sun accelerated the decay of the stricken ship's orbit. In the afternoon, Roskosmos predicted reentry between 00:45 and 06:36 Moscow Time on the same day (5:45 p.m. - 11:36 p.m. EDT on May 7). The agency promised another forecast after 17:00 Moscow Time on May 7. However it was issued at the end of the business hours in Moscow and narrowed the reentry window from 01:13 to 04:51 Moscow Time on May 8 (6:13 p.m. to 9:51 p.m. EDT on May 7).
Another forecast from the US military came in the middle of the day, predicting the reentry on May 8, 2015, at 01:36 GMT (9:36 p.m. EDT on May 7). Around that time, the spacecraft descended to a 141 by 155-kilometer orbit. The forecast was updated one more time in the evening, this time pushing back the reentry by 11 minutes to 01:47 GMT (9:47 p.m. EDT). Another update came during the final two orbits of the spacecraft and put the decay at 01:52 GMT (9:51 p.m. EDT).
Ground track of the Progress M-27M mission on May 7, 2015.
On May 8, 2015, at 05:19 Moscow Time, Roskosmos issued a statement announcing the reentry of the Progress M-27M during its 160th orbit at 05:04 Moscow Time over the central part of the Pacific Ocean. However, it was unclear how the agency was able to confirm that fact given the lack of tracking capabilities over this region.
At 04:20, the US military issued a confirmation of the reentry, but placed it further down the orbital path of the spacecraft over the Pacific Ocean, west of the Southern tip of South America at the point -51 degrees latitude and 273 degrees longitude. According to that information, the reentry took place at 02:20 GMT. The US could actually detect the heat signature of the event with the help of infrared sensors onboard of its early warning satellites.
The final orbit and reentry locations for Progress M-27M on May 8, 2015, according to Roskosmos (left) and the US military (right).
Progress M-27M spacecraft under a payload fairing integrated with the third stage of the Soyuz-2-1a launch vehicle.
From the beginning, the investigation into the Progress M-27M failure focused solely on three final seconds in the operation of the Soyuz-2-1a launch vehicle and the separation of the spacecraft. It looked like a delayed command to cutoff the engine of the rocket's third stage held the key to the mystery. The following timeline of those critical moments had emerged by May 1:
Spacecraft data analysis
According to sources at RKTs Progress, the telemetry from the spacecraft stopped coming slightly earlier than the telemetry from the rocket. However the spacecraft retained some limited function, while multiple debris large enough to detect them from the ground were accompanying the mission and signs of problems were found in the telemetry from the rocket.
As a result, in the first weeks after the accident, publicly available sources tended to explain the accident by an explosion onboard the rocket stage, which damaged the spacecraft, while some considerable force still propelled both vehicles to different orbits. The spacecraft apparently never fired its engines and all its propellant had remained intact after the accident, according to available telemetry. In addition, it takes 30 seconds for the propulsion system onboard the Progress to be pressurized -- clearly not enough to make it operational at the time of the accident. Moreover, an apparent failure of the main computer onboard Progress M-27M probably blocked all its dynamic operations.
Investigators also concluded that following the pressurization sequence onboard Progress, the propellant under pressure of around 12 atmospheres was venting from lines punctured by a nearby explosion of the third stage, causing the tumbling of the spacecraft, a source at the mission control in Korolev said.
Rocket data analysis
Despite all the suspicions about the rocket, its engineers insisted that there was little evidence of the explosion in the available telemetry. For example, data showed normal shutdown of the RD-0110 engine, including the slowdown of the engine's turbopump, the fall of pressure in the combustion chamber and in the gas generator.
At the conclusion of the engine cutoff sequence, special sensors also signaled that the pressure in the engine's four combustion chambers fell to a level of full inactivity. The pyrotechnics then closed shut a pair of valves on a gas generator of the engine, four more valves were closed on oxidizer lines leading to each of four combustion chambers and one valve cut off the main fuel line.
However, from 0.2 to 0.4 seconds after the engine cutoff command, multiple sensors on the stage suddenly showed out-of-limit parameters, as if they were physically cut or thorn. For example, the turbopump rotation rate in the engine was going down smoothly as planned until it suddenly spiked to impossible 250 thousand rotations per minute and stayed there, according to the telemetry. The same way, the combustion chamber pressure sensors showed the fall to 3 kilograms per square centimeter, followed by a sudden surge to out-of-range parameters.
The flow of data from the RTSTs telemetry system located between oxidizer and fuel tanks on the third stage and transmitted via four antennas along two communications channels stopped within a fraction of a second from each other at T+526 seconds in flight. However some fragmentary data still continued coming from two out of three data sources.
Most importantly, the telemetry showed that temperature inside the oxidizer tank of the rocket remained constant at 80 degrees Celsius until T+550 seconds, indicating that its propellant drainage valve remained closed and the vessel was intact long after the separation of the Progress. No other indications of destructive events were available either, sources said.
Finally, the RTSTs radio-telemetry system onboard the third stage was switched off by the flight control system as scheduled at T+554 seconds into the mission, or 24 seconds after the separation between the spacecraft and the rocket.
On May 12, 2015, the State Commission led by Deputy Head of Roskosmos Aleksandr Ivanov presented its preliminary conclusions on the Progress M-27M accident. According to the agency press-release published on the same day, the launch of the Soyuz-2-1a rocket with Progress M-27M went as scheduled until the moment of separation between the spacecraft and the third stage of the rocket. The abnormal separation took place at T+526.716 seconds in flight, sending the spacecraft to an orbit with an apogee 40 kilometers higher than normal and the third stage entering orbit with an apogee 20 kilometers below normal, the agency said.
After reviewing all the materials, members of the State Commission came to a preliminary conclusion that a version of the abnormal separation had been objectively confirmed, which includes two subsequent events related to the depressurization (disintegration after the cutoff of the third-stage engine) first of the oxidizer tank and then of the fuel tank, Roskosmos said.
The agency said that the work of the Commission had been ongoing and that the final classification of the character of the cause leading to the launch failure would require in-depth calculations and theoretical studies, an additional simulation and a number of experimental works, which will be conducted.
Beginning on May 13, members of the Commission were to begin work at the sites of the companies-producers of rocket technology for determining and correcting possible causes of the accident, Roskosmos said. According to industry sources, in addition to visits to main contractors on the rocket and the spacecraft, TsNIIMash engineers went to Saratov in order to test nickel-cadmium batteries on the rocket. The team would try similate a situation with the shortsurcuit and the explosion of the battery.
The press-release also announced a new schedule of ISS missions, which was developed in cooperation with the project partners (in the wake of the accident):
The final conclusions of the State Commission are expected on May 22, 2015, Roskosmos said. However new developments suddenly intervened.
According to industry sources, on May 21, Aleksandr Danilyuk, Deputy Head of TsNIIMash research institute, which led the investigation, was preparing to sign off on a conclusion confirming the disintegration of the oxygen tank on the third stage of the Soyuz-2-1a rocket due to a manufacturing defect. At the time, the prevailing theory was that the welded seam connecting the upper bulkhead to the rest of the tank had given way, because it had to be welded twice during its production. The dual welding was the only one of 50 documented instances of deviations from the standard manufacturing process for the rocket and the spacecraft that the commission thought could have led to the accident.
A source familiar with the investigation reported on the online forum of the Novosti Kosmonavtiki magazine that the disintegration of the oxygen tank had been accepted as the primary cause of the failure primarily because the tank was deemed to be the only source of thrust, which could send the spacecraft 40 kilometers above its projected altitude according to TsNIIMash calculations, which were reportedly doubted by at least some engineers.
However at what was expected to be a final meeting of the investigative team, the head of TsSKB Progress, Aleksandr Kirilin and his deputy Ravil Akhmetov presented results of a detailed study dating back to the 1960s and proving that even after five welding cycles, the properties of the seam would not deteriorate.
At the same time, TsSKB Progress officials put forward a new theory how the Progress spacecraft could contribute to the failure, as a result of a separation from the rocket at a wrong time. According to TsSKB Progress, the spacecraft could initiate the separation process based on its own software algorithms and signals from four separation sensors, which apparently do not take into the account the status of the launch vehicle. (During a nominal flight, the separation is conducted jointly by the rocket's computers which command to cut the pyrotechnic bolts holding two vehicles together and by the spacecraft's computer, which commands to cut fasteners on its side of the interface.). At the same time, the TsSKB analysis of data from the rocket's flight control system also indicated that it had never issued a command for the separation of the spacecraft.
TsSKB conducted a ground separation test involving an experimental third stage and the transfer section from the Progress. First engineers exploded pyro-bolts on the rocket side and then blew up fasteners on the spacecraft side. The attitude control sensor, located in the intertank section of the rocket stage, reportedly showed equal loads from both events.
Based on all the data, TsSKB Progress apparently presented its own chronology of events based on the analysis of available telemetry, which claimed that the orbit confirmation command, PO, and the spacecraft separation command, KO, were issued within 0.12 seconds from each other at T+526 seconds in flight, while they had to have an interval from one to 15 seconds, according to the launch profile agreed between TsSKB Progress and RKK Energia. According to TsSKB Progress, events then developed according the following timeline:
Not surprisingly, RKK Energia staunchly opposed this version of events and insisted that nothing wrong could happen to the spacecraft, despite little data to prove it one way or another. Still, TsNIIMash put off making the conclusion in the investigation until at least May 26, while launching urgent re-evaluation of all available data.
On May 25, TsNIIMash conducted a failure test on the oxidizer tank, which underwent two rounds of welding. However it cracked along the line near the fueling valve only after the internal pressure had reached 10.2 atmospheres, which is far above the normal pressure of 4.5-4.6 atmospheres during the flight. The fuel tank has even lower pressure of 2.2 atmospheres.
On June 1, 2015, Roskosmos published a press-release entitled "Cause of the Failure Determined." It went as following:
...After a thorough analysis of the failed launch and the completion of full-scale experiments, members of the commission came to the following conclusion:
The damage to the ship during its abnormal separation from the third stage of the Soyuz-2-1a launch vehicle resulted from a particular property of the joint use of the cargo spacecraft and the launch vehicle. This design property was related to frequency and dynamic characteristics of joint vehicles.
This design property was not fully accounted for during the development of the rocket and spacecraft complex.
Limitations on further flights of the Soyuz-2-1a rocket with other spacecraft had not been found.
Currently, Roskosmos is developing an action plan for conducting further flight tests of this space complex.
On June 9, Roskosmos will finalize the new flight manifest for human missions in 2015, including launches of cargo ships.
Read much more about the history of the Russian space program in a richly illustrated, large-format glossy edition:
Original flight plan
According to the original plan, the docking of Progress M-27M at the outpost was scheduled on the day of the launch at 16:06:39 Moscow Time (9:06 a.m. EDT). According to the agency, the remote-control radio system, TORU, could be used to attempt to stop the rotation of the spacecraft, however chances of success were low due to unpredictable motion of the vehicle.
Progress M-27M was to follow a six-hour rendezvous profile with the outpost, aiming to achieve docking at 16:06:39 Moscow Time (9:06 a.m. EST) on the day of the launch at the Earth-facing docking port on the Docking Compartment-1, SO1, of the Russian segment. At the moment of the rendezvous with the cargo ship, the space station was expected to be in a 398.01 by 411.02-kilometer orbit.
To reach the outpost, Progress M-26M was scheduled to conduct four orbit-boosting engine firings, one during the mission's first revolution around the Earth and three more during the second orbit:
The autonomous rendezvous process was scheduled to start at 14:01:07 Moscow Time (7:01 a.m. EDT, 11:01 GMT). The final maneuvering, including a flyaround of the station, a short period of station-keeping and, finally, berthing would be initiated at 15:46:13 Moscow Time (11:36 EDT, 12:46 GMT).
Click to enlarge. Credit: RKK Energia
Click to enlarge. Credit: RKK Energia
Click to enlarge. Credit: RKK Energia
Click to enlarge. Credit: RKK Energia
Pre-launch processing of Progress M-27M spacecraft. Click to enlarge. Credit: RKK Energia
A Soyuz-2-1a rocket with Progress M-27M spacecraft rolls out to Pad 6 at Site 31 in Baikonur. Click to enlarge. Credit: RKK Energia
Click to enlarge. Credit: RKK Energia
A Soyuz-2-1a rocket with Progress M-27M spacecraft shortly after delivery to Pad 6 at Site 31 in Baikonur. Click to enlarge. Credit: RKK Energia
Progress M-27M lifts off on April 28, 2015. Click to enlarge. Credit: RKK Energia