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Spektr-RG to fly on a refurbished rocket stage

Russia's flagship space observatory, Spektr-RG, will be launched with a space tug which had passed its original operational warranty and had to be refurbished for the task. The Block DM-03 upper stage required new certification for flight before it could be authorized to carry the irreplaceable X-ray telescope which took nearly a decade to build. Following its launch on a Proton rocket, Block DM-03 will have the critical task of boosting the observatory from its initial parking orbit into deep space, toward a Lagrange L2 point behind the Earth relative to the Sun.

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Block DM-03 architecture with a generic payload.

After the 2016 decision to switch the planned Spektr-RG launch from the Zenit-Fregat rocket to the Proton-Block DM vehicle, Roskosmos State Corporation made plans to use a Block DM-03 No. 4L upper stage, which had been manufactured in 2011 on an order from the Russian Ministry of Defense. The stage was likely intended for a trio of the Uragan-M satellites for the GLONASS navigation network, but it had remained unused because of a reduced demand for replacements.

At the time, the Block DM-03 No. 4L, along with a similar vehicle -- No. 3L -- was in storage at the Experimental Production Plant, ZEM, in Korolev near Moscow. (The ZEM plant mass produces the hardware developed at RKK Energia, including Block DM series.)

The guaranteed life span for the storage and use of Block DM-03 No. 4L was to officially expire on Nov. 23, 2018, which meant that if the launch of the Spektr-RG mission would not take place as then scheduled in September 2018, the upper stage would have to be re-certified for flight after that date. As of the end of 2017, it was increasingly clear that Spektr-RG would not be ready for launch before 2019, thus requiring to re-certify Block DM-03 No. 4L for flight.

However, by 2017, the Soviet-era diagnostics equipment for the Block DM series at the ZEM plant reached such an old age that it had to be upgraded first, before conducting any further testing of vehicles No. 3L and 4L.

To make matters worse, as of September 2017, RKK Energia did not even have the formal permission from the Ministry of Defense to modify the Block DM No. 4L for the Spektr-RG spacecraft. There was also no funding at the time for extending the guaranteed life span of the stage beyond November 2018.

In September 2017, RKK Energia requested 73,785 million rubles (approximately $1.3 million) from Roskosmos to refurbish checkout and power supply components in the diagnostics facility for the Block DM series. This money would also pay for upgrading the diagnostics system for the Block DM series with new computers to check the flight control system aboard Block DM-03.

RKK Energia also requested Roskosmos an additional 35.2 million rubles (approximately $0.6 million) to cover already incurred expenses for the maintenance of Blocks DM-03 No. 3L and No. 4L from 2013 to 2016.

(To be continued)


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Article and illustration by Anatoly Zak; Last update: January 31, 2018

Page editor: Alan Chabot; Edits: January 30, 2018

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General architecture of the Spektr-RG spacecraft as of 2017. Credit: NPO Lavochkin


Block DM-03 during processing in Baikonur. Credit: RKK Energia

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