THE BOR-5 TEST VEHICLE

The aerodynamic behavior of Buran was studied using 85 different scale models (ranging from 1: 3 to 1: 550) in 25 wind tunnels simulating Mach 0.1 to 2.0. These wind tunnels were situated at TsAGI in Zhukovskiy, and at SibNIA and the Institute of Theoretical and Applied Mechanics (ITPM), both in Novosibirsk. A total of 36,630 wind tunnel tests were conducted prior to the maiden flight of Buran.

The Russians also developed 1: 8 scale models of Buran called BOR-5 to study the vehicle’s behavior at re-entry speeds. Unlike BOR-4, they simulated the shape of Buran itself and were launched on suborbital trajectories. The purpose of these flights was:

– to determine major aerodynamic characteristics in real flight conditions at high velocities;

– to determine aerodynamic coefficients, the lift-to-drag ratio, balancing characteristics, roll and pitch stability and to compare them with calculated characteristics;

– to investigate pressure distribution along the vehicle’s surface;

– to determine heat and acoustic loads;

– to check the adequacy of the techniques used to calculate aerodynamic characteristics.

The BOR-5 models weighed 1,450 kg and were 3.856 m long. Because of their small size and the specifics of their trajectory, they were exposed to much higher tempera­tures than Buran and therefore were covered with an ablative heat shield rather than

tiles. The nosecap was made of a tungsten-molybdenum alloy. Just like the BOR-4 vehicles, they were equipped with a wide range of sensors to measure temperatures, aerodynamic characteristics, and orientation. The data obtained by these sensors were sent back in real time via telemetry.

The BOR-5 models were launched from Kapustin Yar by the Kosmos-3M-RB5 rocket and launched in the direction of Lake Balkhash, covering a distance of about 2,000 km. Having reached a maximum altitude of 210 km, the second stage of the Kosmos booster pitched down to accelerate the model to Mach 18.5 at 45 degrees before separation. After separation from the second stage, the model used small gas thrusters for orientation, switching to aerodynamic surfaces as it entered the denser layers of the atmosphere. Beginning at an altitude of 50 km, it followed the same changes in bank angle and angle of attack as Buran, albeit at much higher speeds than the full-scale orbiter. At an altitude of 7 km a parachute was deployed to reduce the vertical landing speed to 7-8 m/s.

The BOR-5 vehicles were built at NPO Molniya’s EMZ factory with the assis­tance of specialists from other divisions of NPO Molniya and also from the Flight Research Institute. Like the BOR-4 missions, the test flights were supervised by a State Commission headed by Gherman Titov.

The first BOR-5 (serial nr. 501) was launched on 6 July 1984, but was lost when it failed to separate from the second stage due to an electric fault. The first successful mission took place with vehicle nr. 502 on 17 April 1985. Post-flight analysis did

reveal significant damage to the nosecap and leading edges of the wings, which altered the vehicle’s aerodynamic characteristics. Therefore, on subsequent missions those areas were protected with a special molybdenum alloy and a special anti-oxidation coating. Three more successful missions (using models nr. 503, 504, 505) were con­ducted on 27 December 1986, 27 August 1987, and 22 June 1988. Models 501 to 504 were outfitted with small mock-up turbojet engines on either side of the vertical stabilizer, but these were no longer mounted on the final BOR-5 vehicle because by then it had been decided to fly Buran without turbojet engines.

Vehicle 505 was unsuccessfully put up for auction in the United States in 1991 and was stored in the Mojave Desert for about four years before being put on display at the Santa Barbara Museum of Flight. In 1997 it was purchased by a person in Merritt Island, Florida, who still owns the vehicle [19].