Blok DM-03

The Blok DM-03 (Russian: Блок ДМ-03 meaning Block DM-03), GRAU index 11S861-03, is a Russian upper stage used as an optional fourth stage on the Proton-M carrier rocket. Two have been launched, the first in December 2010,^[1] however as of July 2013 the stage is yet to be demonstrated in flight as both launches failed before fourth stage ignition, the first as a result of a problem with the Blok DM's fuel load.^[2]

The Blok DM-03 is powered by a single RD-58MF engine, fuelled by RP-1 paraffin and oxidised by liquid oxygen. It can carry 25% more propellant than the Blok DM-2, which it replaced as a Proton upper stage;^[2] however most government launches and all commercial missions use the Briz-M instead. The payloads for the first two Blok DM-03 launches were groups of three Uragan-M satellites for the GLONASS programme, with further missions slated to carry three more Uragan-M satellites, and two Ekspress satellites on separate launches. The Blok DM can inject payloads into orbit more accurately than the Briz-M,^[3] making it better suited for launching satellites such as the Uragan-M which lack apogee motors.

When production ended in 2012, five Blok DM-03 stages had been produced by RKK Energia, for use on Proton and potentially Zenit rockets.^[2] A new version of the upper stage is expected to be introduced once the five launches are complete;^[4] all five DM-03s have been slated for Proton launches between 2010 and 2015.

Launches

Failures

The Blok DM-03 is yet to attempt or complete a burn as part of a launch, since both Proton launches to include the upper stage have failed before reaching the point of Blok DM ignition. In the 2010 failure, the rocket was too heavy to reach orbit and reentered the atmosphere during a coast phase between the end of third stage flight and the beginning of the Blok DM-03's first burn, whilst the 2013 flight failed after the rocket went out of control seconds after liftoff.^[7]

The first launch to use the Blok DM-03 was conducted on 5 December 2010, from Site 81/24 at the Baikonur Cosmodrome. The rocket was expected to deploy three Uragan-M satellites for the GLONASS constellation, with the first three stages of the Proton placing the Blok DM and payload into low Earth orbit, and the Blok DM then propelling the satellites into their operational medium Earth orbits. During preparations for launch, the Blok DM-03 was fuelled using instructions intended for the Blok DM-2, which included an instruction to fill the tanks to 90% capacity.^[2] Owing to the DM-03's larger tanks, this was more propellant than needed for the mission, and left the rocket too heavy to achieve orbit. The Blok DM, with payload still attached, reentered over the Pacific before the start of its scheduled first burn.^[2] Following the failure, the Blok DM-03 was grounded for further tests, with a Proton-M/Briz-M and several smaller Soyuz-2 rockets being used for GLONASS launches over the next 30 months.^[3]

The July 2013 flight, which marked the Blok DM-03's return to flight was another GLONASS launch, also conducted from Site 81/24, with liftoff occurring on time at 02:38:22 UTC. The rocket went off course almost immediately, before disintegrating. The payload fairing and upper stage were among the first parts of the rocket to detach. Debris fell around 1,000 metres (3,300 ft) from the launch pad, with the parts of the rocket still intact exploding upon impact. An investigation determined that three first stage yaw sensors had been installed backwards, resulting in the failure of the vehicle's guidance system.^[7]

Footnotes

1. ↑ 1.0 1.1 Although the December 2010 launch failed before the Blok DM-03 was scheduled to perform its part of the flight, the stage's incorrect fuel load was discovered to have caused the failure

References