Angara with Block DM: Mixing the unmixable
In a strange historical irony, a space tug inherited from the Soviet lunar program found its way right to the top of Russia's 21st century rocket. It also made two old rivals in the Russian space industry cooperate again.
An interpretive drawing of the Angara-5 rocket with the Block DM-03 upper stage. The developer had never released an official depiction of the architecture, even though this configuration was considered for the rocket's second test mission.
The idea to put the veteran Block DM stage on top of Angara rockets was obviously on a collision course with the Angara's primary developer's own designs to employ the Briz-M space tug on the new-generation launch vehicle. Suffice to say that during two decades of painful development of the Angara rocket, GKNPTs Khrunichev did not release a single depiction of the Angara equipped with the Block DM stage or its variants. Nor did the company include Block DM in the commercial user's guide for the Angara.
However by the end of 2000s, environmental concerns over the use of toxic propellants, which have marred Proton operations in Kazakhstan for years, reached Russia as well. The environmental issues also coincided with the realization that the geographical position of the launch facility for the Angara-5 rocket at the northern launch site in Plesetsk would seriously cripple the rocket's ability to compete on the international market. To access the equatorial orbit required for commercial communications satellites, the Russian government would have to replicate again the infrastructure in Plesetsk, whose development had originally been insisted upon by the Ministry of Defense. After the Kremlin had also squandered an opportunity to build a commercial launch pad for the Angara in Baikonur as a joint venture with Kazakhstan, Russian taxpayers had to foot the bill for another launch pad for Angara in Vostochny. From the outset of that project, the local population, from activists to the regional governments, showed great concern for the environmental impact of the new center on the surrounding area and on the drop zones downrange from the site.
By adding the kerosene-burning Block DM to Angara-5 and to Angara-3, Roskosmos could avoid the use of toxic propellants employed in Briz-M, even though this replacement could do little to improve the rocket's payload capabilities. With that swap, the entire Angara rocket would be fueled by a single and relatively safe propellant combination -- liquid oxygen and kerosene. (Small amounts of toxic hydrazine would still be needed in Vostochny to fuel satellites). RKK Energia also long advertised other advantages of Block DM over Briz-M, such as its better maneuvering capabilities, which result in more accurate delivery of satellites into their orbits.
Ironically, the nearly half a century-old Block D would outlive its grandson -- Briz-M! Moreover, the latest incarnation of the Moon-Race Era space tug can now migrate to the more powerful Angara-5V variant, where it has a chance to play a role in the human exploration of the Moon in the new century.
To the chagrin of GKNPTs Khrunichev, on Sept. 8, 2009, the head of RKK Energia issued Order No. 326 beginning an effort to adapt the DM-03 stage for the Angara rocket. On December 22 of the same year, the Russian government issued Special Decree No. 1055-30, which formally endorsed the program. The preliminary design of the stage, designated 11S861-03, was ready by the middle of 2010. (566) The project apparently remained on ice for the next four years, as GKNPTs Khrunichev struggled to get the Angara family ready for launch, while the Ministry of Defense worked to complete its launch pad in Plesetsk. In December 2014, Angara-5 finally made its inaugural mission with the Briz-M stage as its space tug, however the rocket's second mission was apparently considered to fly with Block DM-03 to deliver a payload from an initial parking orbit to its final destination.
In 2014, RKK Energia issued a technical project for the 14S48 Persei (Perseus) and 14S49 upper stages, which incorporated most features proposed for the Phase II upgrade in the DM-03 project. The 14S48 variant was equipped with an older 11D58M engine, while the 14S49 would sport the new-generation 11D58MF engine. Both variants will apparently do away with the use of toxic propellants in auxiliary propulsion systems and will feature new compact flight control system. Both stages would also have a new removable adapter, which could serve as an interface for the largest payload fairing available for the Angara-5 rocket.On Dec. 27, 2021, Russian military personnel at the Plesetsk range, north of Moscow, performed the third test launch of the next-generation Angara-A5 rocket. During the mission, the newly configured vehicle carried the first Persei space tug which failed to insert a simulated cargo into a target orbit.
Payload capabilities of the Angara-5 rocket with various upper stages (as of August 2015):
General layout of the 14S48 and 14S49 upper stages as of 2014. Notable is an absence of the separate ullage motors used to initiate main engine firing. An add-on collar adapter matches the width of the Angara's payload fairings. Credit: RKK Energia
Booster stages for the third Angara-5 rocket during processing in Plesetsk circa October 2021. Click to enlarge. Credit: Russian Ministry of Defense