Credit: from Semenov, et. al., Buran, 1995.. 20,069 bytes. 353 x 238 pixels.
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| BOR-4 in the shop - BOR-4 in the shop prior to launch Credit: from Semenov, et. al., Buran, 1995.. 20,069 bytes. 353 x 238 pixels. |
To investigate the hypersonic aerodynamic characteristics and heat shield materials of the manned Spiral OS lifting body, 1:3 and 1:2 scale models of the OS were to be built. Unlike the full-scale model, these were had fixed wings and were designated BOR (unpiloted orbital rocketplane). BOR-1, -2, and -3 were increasingly sophisticated models of the configuration, flown on suborbital trajectories. After the cancellation of Spiral in favour of the Buran, BOR-4 subscale spaceplanes were used to test heat shield materials developed for Buran. Certain essential tests of these heat shield materials could not be done in the lab. These included interaction with the plasma sheath during re-entry, chemical disassociation effects, etc. The BOR-4 was clad in 118 tiles of the type developed for Buran as well as carbon-carbon nose cap and leading edge. These BOR-4 unmanned orbiters were equipped with braking engines. After a circuit of the earth, the spacecraft would deorbit, perform a gliding re-entry, followed by parachute deployment, splashdown in the ocean, and recovery by Soviet naval forces. BOR-4 flew four successful test flights at speeds of from Mach 3 to 25 and altitudes of 30 to 100 km. These test flights confirmed the physical, chemical, and catalytic processes that operated on the selected heat shield materials in the re-entry plasma. BOR-4 also provided important data on the acoustic environment during launch and re-entry. Compared to the Spiral MiG 105-11 EPOS configuration, the BOR-4 had a flattened, wider body with a much smaller vertical stabiliser. The cruise-back turbojet of the 105-11 seems to have been eliminated, and the canted stabiliser tips were cut off at the Mach angle, a MiG trademark.
 | BOR-4 at Berlin - BOR-4 as exhibited at Berlin side view Credit: Oliver Ha�a. 21,801 bytes. 353 x 226 pixels. |
Total Length: 2.8 m. Maximum Diameter: 2.2 m. Total Mass: 1,200 kg. Electrical System: Batteries.
 | BOR-4 at Berlin - BOR-4 as exhibited at Berlin side view Credit: Oliver Ha�a. 22,259 bytes. 317 x 211 pixels. |
The Vehicle Analysis Branch began investigation of the Soviet BOR-4. Small models were tested in NASA wind tunnels and demonstrated that the vehicle had good aerodynamic characteristics throughout the speed range from orbital entry interface to low supersonic speeds. The Soviet design had a 2,040 km cross-range capability and an outstandingly benign thermal profile at peak heating conditions. Therefore Langley adopted it as a baseline for a Crew Emergency Rescue Vehicle to back-up or replace the shuttle after the 1986 Challenger accident.
 | Uragan / BOR-4 Credit: © Mark Wade. 4,244 bytes. 456 x 353 pixels. |
Subscale Spiral spaceplane. After 1.25 revolutions of the earth, deorbited and recovered by Soviet naval forces in the Indian Ocean, 556 km south of the Cocos Islands .
 | BOR-4 Recovery - BOR-4 - Photo by Australian P-3 Naval Reconnaisance Aircraft Credit: NASA. 18,199 bytes. 332 x 246 pixels. |
Subscale Spiral spaceplane. In a new mission profile, braked out of orbit over the South Atlantic and was recovered in the Black Sea after one orbit of the Earth.
 | BOR-4 Recovery - BOR-4 - Photo by Australian P-3 Naval Reconnaisance Aircraft Credit: NASA. 37,580 bytes. 333 x 296 pixels. |
Last flight of the subscale Spiral spaceplane. Recovered December 19, 1984 5:26 GMT, in the Black Sea after one orbit of the Earth.
 | BOR-4 Model - BOR-4 wind tunnel model used by NASA to study configuration and refine it for use in HL-20/HL-42 vehicles. Credit: NASA. 11,973 bytes. 230 x 357 pixels. |