Progress MS-06 docks; mission to remove Pirs module delayed

by Chris Gebhardt

Roscosmos has launched – and docked – the Progress MS-06 resupply mission to the International Space Station.  Liftoff occurred at 15:20:13 local time (05:20:13 EDT) from the Baikonur Cosmodrome in Kazakhstan on Wednesday, 14 June 2017 with docking following on Friday.  This mission was to mark the first time a major element of the ISS will be deorbited. However, the Pirs docking compartment removal has been delayed to next year.

Progress MS-06 – launch preparations:

Given the launch campaigns of late for Roscosmos to the International Space Station, processing of the MS-06 Progress mission has been relatively uneventful and quite smooth.

In all, Progress MS-06 is the 158th Progress mission since the program began in 1978 for resupply efforts of the Salyut 6 space station and the 69th Progress mission to the ISS, counting the two Progress flights that were not designated as resupply missions because they delivered module elements to the Station.

One of those two Progress non-resupply flights occurred in 2001, when a modified Progress delivered the Pirs docking compartment to ISS.

Including this launch, 69 Progress missions have launched to ISS to date, with Progress MS-06 (or Progress 67 as it is known to NASA) the 66th attempt of a Progress family vehicle to successfully reach the Station, following the Progress 44 launch failure in August 2011, the Progress 59 launch mishap in April 2015, and the Progress 65 launch failure in December 2016.

Following retirement of the Soyuz-U carry a rocket in February, Progress MS-06 – as a few previous Progress missions have – utilized the Soyuz-2.1a rocket for lift off.

Following various construction milestones, system checkouts, and cargo loading, the Progress MS-06 vehicle was fueled with its propellants and compressed gases at the filling station at Baikonur on 31 May 2017.

After fueling operations were complete, technicians transferred the vehicle to the Spacecraft Assembly and Testing Facility (SC ATF), where was installed onto the assembly jig for final pre-launch processing.

In the SC ATF, engineers successfully mated Progress MS-06 to its support structure mount that will allow it to ride safely atop the third stage of the Soyuz 2.1a rocket.

Following the Designers Inspection, which clears the way for final launch processing, Progress was encapsulated into its payload fairing on 7 June.

On 9 June, engineers transported the encapsulated Progress to the Launch Vehicle Integration and Test Facility (LV ITF), where Progress was mated atop its Soyuz rocket.

The entire vehicle rolled out to launch pad 31/6 at the Baikonur Cosmodrome in Kazakhstan via rail transport on 11 June.

Progress MS-06 launched at 09:20:13 GMT (05:20:13 EDT – 15:20:13 local time at Baikonur) on Wednesday, 14 June 2017.

After an 8 minute 45 second ascent, the Soyuz-2.1a rocket delivered Progress MS-06 into its initial orbit to begin a two-day, 34 orbit rendezvous with the ISS.

At the time of writing, has not been able to confirm why Progress MS-06 is conducting a two-day rendezvous instead of the fast track, four orbit docking profile used again since earlier this year after confirmation that the new ground communications tracking center at the Vostochny Cosmodrome was completed.

Most likely, however, the two-day rendezvous is part of an overall effect of crew compliment reduction on the ISS now that the number of people onboard Station has been reduced to three for the next two months.

MS-06 and the two-day ISS rendezvous:

Once Progress MS-06 was deposited into its initial orbit, the vehicle performed primary health checks with the Vostochny Cosmodrome in eastern Russia before passing out over the Pacific.

The vehicle performed its first orbit raising maneuver, the DV1 burn, at 08:53:03 EDT (12:53:03 GMT) on 14 June.

The DV2 burn was followed shortly thereafter at 09:31:30 EDT (13:31:30 GMT).

The two burns cumulatively changed Progress MS-06’s velocity by 62.03 m/s and raised and circularized Progress’ orbit to better match that of the International Space Station’s.

A third burn, DV3, followed on Thursday morning at 06:55:09 EDT (10:55:09 GMT) and finalized Progress’ orbit via a delta-V shift of 4.00 m/s.

On Friday morning, docking operations commenced when the SCAN S-bd / C2V2 / HTV PROX / Cygnus PROX / Cygnus S-bd GS / Dragon S-bd GS rendezvous systems of the USOS (United States Operating Segment) are taken to “inhibit” to prevent any interference with Progress’ automated docking system and its communication with the RS (Russian Segment) of the ISS.

Inhibiting those systems occurred at 01:20 EDT (05:20 GMT) on 16 June while Progress MS-06 was 2,700 km from Station.

Progress then initiated its automated docking sequence three hours later at 05:19:06 EDT (09:19:06 GMT), with the Impulse 1 burn of 15.147 m/s at 05:42:44 EDT.

Impulse 1 changed Progress’ trajectory to prepare the craft for proximity ops with ISS and to begin aligning it properly for the flyaround maneuver late in the approach timeline.

Further preparations on Station continued with the handoff from the USOS Motion Control System (MCS) to the RS MCS at 05:54 EDT.

Impulse 2, delta-V: 1.575 m/s, from Progress followed at 06:04:13 EDT (10:04:13 GMT).

The ISS’s three person crew will then activated the Zvezda Service Module’s (SM’s) Kurs-P communication system at 06:07 EDT, followed by the activation of the Kurs-NA system on Progress at 06:08 EDT.

Progress performed the Impulse 3 burn (delta-V: 25.01 m/s) at 06:27:11 EDT (10:27:11 GMT).

The SM’s Kurs-P system began tracking Progress’ range from the ISS when the two craft are separated by 45 kms at around 06:37 EDT.

A final Kurs system communications check between the ISS and Progress MS-06 followed at 06:50 EDT once Progress had closed to 15 km.

The SM’s VHF-2 transmitter was activated at 06:55:46 EDT for TORU (Teleoperated Mode of Control) command link when Progress was 9 km from ISS, with Progress’ VHF receiver turned on at 07:05:56 EDT for TORU command link at a range of 3 km from Station.

TORU is the backup, manual docking system that Fyodor Yurchikhin, Expedition 51 Commander, could use to dock Progress MS-06 to the Station should the craft’s or Station’s automated Kurs docking system fail.

Progress then performed the Impulse 4 maneuver, imparting a delta-V shift of 5.396 m/s at 07:07:37 EDT (11:07:37 GMT).

TORU command link test between ISS and Progress followed seconds later at 07:07:56 EDT.

The ballistic targeting point was established at 07:09 EDT.

Impulse 5 came around 07:11:59 EDT, altering Progress’ speed by 5.633 m/s, followed by Impulse 6 (delta-V: 1.564 m/s) at 07:14:58 EDT.

Progress then began its flyaround maneuver of the ISS to align itself with the aft docking port of the Zvezda SM at 07:17:43 EDT (11:17:43 GMT).

The flyaround ended at 07:26:44 EDT, at which point Progress MS-06 performed stationkeeping (maintaining relative position with Station) as the crew and Mission Control Moscow review all data points from MS-06 and verify its alignment with SM’s aft docking port.

Under the pre-established timeline, Progress MS-06 pulsed its thrusters at 07:32:21 EDT (11:32:21 GMT) to begin the final 10 minute 9 second approach sequence.

Using its onboard computers, automated docking systems, and navigational aides, Progress MS-06 guided itself to a planned docking at 07:42:30 EDT (11:42:30 GMT). The timing of the actual docking was slightly earlier, marked at 07:37 EDT.

At the moment of docking, the RS of the Station inhibited ISS’s attitude control, placing the Station in free drift to help equalize dispersions between Progress and the ISS created by the energy of Progress’ “contact” with the docking mechanism.

Those dispersions dissipated in time for all the hooks on Progress to drive into the ISS at around 07:50 EDT – creating a hard dock between the two craft.

The ISS was then be taken out of free drift and reoriented to its nominal attitude before the RS hands back motion control to the USOS at around 08:35 EDT.

Eventual farewell to Pirs, preparing for the MLM Nauka lab:

While Progress MS-06 docked to the International Space Station on the aft end of the Zvezda Service Module, the original plan was for the vehicle not spend all of its time at the ISS at that port.

Once Progress’ 2,398 kg (5,286 lb) of payload – which consists of crew supplies, equipment and several satellites, two of which were built by schoolchildren – had been removed and the Station’s disposal equipment packed inside, the ISS crew was to close and seal the hatches between Progress MS-06 and the Station and prepare it for undocking.

The original plan called for the vehicle to be undocked from the aft portion of this Zvezda Service Module and re-dock over the course of a couple of hours to the Progress docking port on the Pirs docking compartment.

However, this redock plan has been moved to a later flight, namely Progress MS-09 at the end of 2018.

The maneuver relates to the plan to remove the Pirs module from ISS in order to make room for the MLM (Multipurpose Laboratory Module) Nauka for Russia, which has been heavily delayed – the latest delay relating to a contamination concern.

Nauka – Russia’s primary research lab for the Station – requires the docking port Pirs is currently using.

Nauka is tentatively scheduled to launch in 2018 aboard a Proton-M rocket.

Pirs itself was delivered to ISS in 2001 via a modified Progress vehicle and is currently attached to the nadir port of Zvezda.

For its eventual removal, the now-future Progress will begin a process that no other spacecraft has yet performed – the removal for destructive deorbit of a permanent module of the International Space Station.

At the end of its mission, the future Progress mission will pulse its thrusters, while keeping its docking clamps firmly latched onto Pirs, and will pull the docking compartment away from the International Space Station.

In this manner, Pirs itself will undock from the Station, with Progress acting more like a tugboat to safely maneuver the module away from the vicinity of the ISS.

Progress will then maneuver, with Pirs still attached, toward a destructive reentry into Earth’s atmosphere that will see the first major element of the International Space Station deorbited.

The reason Roscosmos has chosen to remove Pirs from the Station has nothing to do with the compartment’s overall life expectancy, usefulness, or performance.

It was entirely related to making room for the much-delayed MLM.

(Images: Roscosmos, NASA)

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