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Previous chapter: Spiral development history
The 115-ton Spiral system was conceived as a two-stage aerospace system, where a large booster aircraft would launch the orbiter, equipped with its own two-stage rocket booster. (317)
The entire system could deliver a 10.3-ton payload into a 130-150-kilometers orbit.
The Spiral project promised an orbital delivery system where payloads would reach as much as nine percent of the total launch mass of the vehicle -- an unprecedented feat for a traditional space rocket. Thus it would cut the cost of delivering one kilogram of payload into orbit by as much as 3-3.5 times comparing to existing launch vehicles.
Hypersonic Carrier Aircraft, GSR
The 52-ton hypersonic carrier aircraft, known by Russian abbreviation as GSR, would be equipped with four hydrogen-burning, air-breathing jet engines. (Although early versions of the GSR plane were to be powered by traditional kerosene-burning engines.)
After a horizontal takeoff from a runway, the GSR could accelerate up to 1.8 kilometers per second, or Mach 6 (six time the speed of sound). It would then release the orbital stage with its own two-stage rocket booster at an altitude of 28-30 kilometers.
The first stage of the Spiral would accelerate the orbital plane up to 4.5 kilometers per second before dropping away, while the second stage would then complete the orbital insertion at an altitude of around 130 kilometers.
The orbital stage
The 8-10-ton orbiter would then fire its attached rocket stage to reach a 130-150-kilometer orbit. The takeoff from the Soviet territory would restrict the inclination of achievable orbits from 45 to 135 degrees from the Equator. However the orbital stage would be capable of achieving an additional 17-degree change in the inclination of its orbit.
During reentry into the Earth's atmosphere, the orbiter could vary its landing trajectory from 4,000 to 6,000 kilometers and maneuver from side to side up to 1,500 kilometers. This capability would enable the vehicle to land on pre-determined airfields in the USSR from each of every three orbits passing over the Soviet Union. Using its own "built-in" jet engine, the orbiter could land on any Class II runway. (317)
The most unusual feature of the Spiral space plane was its wings, which could rotate around an axis running along the side of the fuselage, not unlike planes use to on aircraft carriers. When in a vertical position, the wings would be shielded from exposure to the most severe heat loads during reentry, leaving only the belly of the orbiter to be protected with a heavy duty heat shield. The hollow nose cap and wings were also designed to serve as radiators to facilitate thermal conditioning of the vehicle during the return home.
Once the most heat-intensive phase of the reentry was over, the Spiral would unfold its wings into an almost horizontal position, acquiring good gliding abilities for its approach to a runway.
The heatshield on the underside of the orbiter was connected to the rest of the body on special hinges, which allowed it to shift relative to the rest of the fuselage and isolate the heat generated during reentry from reaching the main body of the orbiter. The heat shield was made of ultra-thin silicon-based fiber and amorphous refined quartz reinforced with a silver layer.
The landing gear was designed in such a way that when in folded position it was located inside a heat-protected area of the ship and it could be lowered without any doors or openings in the bottom heat shield.
The orbiter was to be equipped with its own liquid propellant engine with a thrust of 1.5 tons. It would be used for orbital correction and braking maneuvers to return to Earth. Two backup braking engines with a thrust of 16 kilograms each would be available.
An additional six small engines with a thrust of 16 kilograms and 10 engines with a thrust of one kilogram would be used for attitude control.
Spiral technical characteristics:
Writing, photography and illustrations: Anatoly Zak; Last update: October 11, 2012
Last edit: November 20, 2008
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Scale model of the Spiral system in the takeoff configuration. Click to enlarge. Copyright © 2001 Anatoly Zak