Payload capacity and accommodations
The Buran orbiter was conceived to match the capabilities of the Space Shuttle and its performance requirements were defined early on in the project based on available data on the American system. By 1972, under the influence of the U.S. Department of Defense, the payload requirements for the Shuttle started crystallizing at a payload bay 60 ft (~18.3 m) long and 15 ft (~4.6 m) in diameter, and a payload mass of up to 65,000 lbs (~29.5 tonnes). jenkins When the first set of technical proposals for the Reusable Space System was submitted by NPO Energia in October 1974, the payload requirement was 40 tonnes to a 200 km 51.6-degree reference orbit, with 20 tonnes return. The resulting RLA-135 vehicle was an oversized version of the Shuttle, with a 20 meter long payload bay 5 meters in diameter. By June 1975, the requirements were amended to 30 tonnes to orbit and 20 tonnes return, and a design “not inferior to the American [system]”. [^2] These values became official with the February 1976 Central Committee resolution that formally launched the Soviet shuttle effort and remained as the performance baseline for the remainder of the program, even as the Shuttle’s eventual lifting capability was somewhat lower. jenkins 55 tonnes
The production Buran orbiter featured a payload bay 18.50 m long with a 4.60 m diameter. Due to the required clearances, the maximum payload envelope was a cylinder 17 m long with a 4.50 m diameter. [^3] The “hypothetical payload” for the orbiter was a 4.15 meter diameter cylinder 15 meters in length. For low-inclination, low-altitude orbits, the maximum payload of 30 tonnes is dictated mainly by structural limits of the orbiter and the loads expected during nominal flight and abort scenarios as well as the required dV reserve of the orbiter. Return payload capacity is baselined at 15 tonnes for payloads captured from orbit and non-deployable payload bay hardware, with a maximum allowed return payload of 20 tonnes. Naturally, in case of a launch abort, the orbiter was able to land with the full 30 tonnes of payload.
With the maximum 30-tonne payload to be deployed at the 200 km, 50.7-degree circular reference orbit, the orbiter is configured to support a 7 day mission as standard. [p.46]
Payloads are installed in the orbiter through the Payload Attachment System (SKPG), a set of fixed and releasable payload trunnion fixtures. The releasable fixtures are electrically driven and can be used to both deploy and capture payloads through commands issued autonomously by the flight computer or by a crew member from the RM-5 workstation. The SKPG fixtures are attached to the orbiter through bridge fittings, which are supported by bridge attachment points machined into every other mid-fuselage frame. Twelve attachment points are located on each side of the payload bay; a bridge fitting can be installed between any two neighboring attachment points. The bridge fitting is secured to the sill longeron with four bolts below the cradle’s top edge. Along the top edge, a number of indexed positions are available for the fixtures. Each bridge fitting can hold one or multiple trunnion fixtures for both deployable payloads and fixed payloads like laboratory modules, extra propellant tanks or hardware pallets. Payloads are attached through trunnions to two fixtures at the forward end and any one or both fixtures at the aft end. The trunnions are held in the fixtures through ball bearings and carry only vertical and longitudinal loads, being isolated from all bending and torsional loads. Along the center of the payload bay, a beam is installed between two neighboring frames which braces the payload’s keel support against transverse loads. Shorter non-deployable payloads can also be attached through a system of three supports, with one trunnion fixture on each side of the payload bay and a lower support held by a ball socket. Smaller payloads and non-deployable hardware up to one tonne can be attached to one bridge fitting only, e.g. the SPK pallet. [A] 1.4.2
It is important to note that due to mass overruns on the orbiter and the Energia launcher, the actual payload capacity for fully outfitted first series orbiters launched using early production Energia core stages is lower than the design value. The Blok Ts core stage used for the November 1988 maiden flight of orbiter 1K was around 7.5 tonnes overweight, bringing the lifting capacity of the Energia down by about the same amount; from 105 to ~97.5 tonnes. Consequently, the orbiter payload was reduced to around
Buran reference orbit is 250 km at 50.7 deg inclination. This corresponds shuttle (1999, 104% throttle) 203km due east (28.5) is 55,250 lbs (25.1 t) 203km at 57 is 41,000 (18.6 t), at 50.7 (buran-like) is 44,150 lbs (20.0 t), or 37,600 (17.1 t) columbia. -1500 kg for altitude,
Bibliography
Semyonov, 1995, ch. 1.2 [A] [^2] Reusable Space System with Orbital Ship OK-92 - Technical Reference p. 3 [^3] AKS p.31