MTKVA - original concept (top) and refined design (bottom)
Credit: © Mark Wade. 15,704 bytes. 625 x 180 pixels.
In 1974 the N1 heavy launch vehicle project was cancelled and Glushko was appointed chief designer of the new NPO Energia enterprise, replacing Mishin as the head of the former OKB-1. At the same time in the United States development work was underway on the space shuttle. The US Defence Department planned to use the shuttle for a range of military missions. The Soviet military, seeking strategic parity, wished development in the Soviet Union of a reusable manned spacecraft with analogous tactical-technical characteristics.
As far as the manned orbital vehicle itself, the OKB-1 specialists who had developed the Soyuz capsule disapproved of the winged US shuttle design. They knew from the extensive aerodynamic studies undertaken to develop Soyuz that there were large weight penalties and thermal control problems in any winged design. Their studies indicated that a lifting body shape capable of high angles of bank at hypersonic speed could nearly match winged designs in cross range. They felt that the parachute and retrorocket soft vertical landing methods developed for Soyuz could be applied to a larger spacecraft as well.
Therefore the preferred 1974 design was an unwinged spacecraft, consisting of a crew cabin the forward conical section, a cylindrical payload section, and a final cylindrical section with the engines for manoeuvring in orbit. The MTKVA would be launched by the Vulkan launch vehicle into orbit, and after completing its mission undertake a controlled re-entry, using a hypersonic lift-to-drag ratio of 1.0 to make wide cross-range manoeuvres for recovery on Soviet territory from almost any orbit. The MTKVA would glide to the landing zone at low subsonic speed. The final landing manoeuvre would use parachutes for initial braking, followed by a soft vertical landing on skid gear using retrorockets.
To reduce development costs, NASA and USAF trade studies settled on a partially reusable design. While the solid propellant booster rockets were recovered, the cryogenic main propellant tank of the shuttle core was expendable. The main engines and guidance system were recovered with the orbiter.
|Buran configurations - Aerodynamic configurations of Buran tested during development.|
Credit: © Mark Wade. 10,148 bytes. 283 x 183 pixels.
The Soviet Union at this point had no experience in production of solid rocket motors, especially segmented solid rocket motors of the type used on the shuttle. Glushko favoured a launch vehicle with parallel liquid propellant boosters. These would use a 700 tonne thrust four-chamber Lox/Kerosene engine already under development.
The high chamber pressure, closed-cycle, reusable 230 tonne thrust Lox/LH2 main engine being developed for the shuttle was well outside engineering experience in the Soviet Union. No production engine using these cryogenic propellant had ever been used in Russian rockets, and the largest such engine under development was the 40 tonne thrust 11D57. Glushko believed that while a Soviet cryogenic engine of 200 tonnes thrust could be developed in the required time, to develop a reusable engine would be impossible due to limited experience with the propellants.
This conclusion led to other important design decisions. If only expendable engines were to be used, there was no need to house them in the re-entry vehicle for recovery. This meant that the orbiter itself could be moved from the lateral mounting of the space shuttle to an on-axis vertical loading position. The result was the Vulkan launch vehicle - a classic Soviet launch vehicle design: booster stages arranged around a core vehicle, with the payload mounted on top. The elimination of the lateral loads resulted in a lighter booster, and one that was much more flexible. The vehicle could be customised for a wide range of payloads by the use of from two to eight booster stages around a core equipped with from one to four modular main engines. Either a payload container for heavy unmanned payloads (mainly the elements of Glushko's LEK lunar base) or the military's required spaceplane could be placed on the nose as the payload.
After a great deal of detailed analysis the definitive MTKVA design proposed in May 1976 had a refined aerodynamic shape with a rounded triangular cross section. This gave it the ability for high bank angles at hypersonic speeds and increased cross-range manoeuvrability. Small vertical stabilisers and a body flap at the base of the vehicle were sufficient for manoeuvring the vehicle in the atmosphere. Numerous small soft landing rockets were exposed when the landing gear deployed. The 200 tonne vehicle had over twice the shuttle's mass and nearly three times the shuttle's payload.
After two years of preliminary work on the Vulkan and MTKVA, the Soviet military and political leadership declared a national requirement for a spacecraft of the same class as the US space shuttle. Comparison with the competing concepts indicated that despite the evident advantages of the MTKVA approach, there were serious technical and operational problems with that design. There was considerable technical risk in realizing the vertical landing itself - and considerable operational risk in completing the fast and complex series of operations necessary to achieve the landing. There were also problems in ground handling - how to move the vehicle after it had landed, especially if this occurrred outside of the normal landing zone. The final analysis of the problems indicated that the rational solution was an orbiter of the aircraft type. The MTKVA and Vulkan designs were modified to meet this order. The Buran orbiter, a straight aerodynamic copy of the US space shuttle, replacing the MTKVA and was moved to the lateral position. But the engines, for the reasons given earlier, remained in the core vehicle. The liquid boosters were retained, but reduced to four in number. After being restressed for the lateral launch loads, the resulting Energia launch vehicle and Buran space plane had only half the payload capability of the original design. Only in considering this evolutionary history can the design of the Energia/Buran be understood.
Total Length: 25.0 m. Maximum Diameter: 8.0 m. Total Mass: 200,000 kg. Total Payload: 80,000 kg. Main Engine Propellants: N2O4/UDMH.