UR-500 Polyblock Credit - © Mark Wade

UR-500 design studies considered two variants of the first stage: polyblock and monoblock. The polyblock variant consisted of a centre large diameter oxidizer tank surrounded by several smaller diameter fuel tanks. This version could be assembled in a special rig with the lateral blocks being sequentially mounted on the centre. In January 1962 this design was chosen as most advantageous, following studies that indicated improved wind loads and bending moment characteristics compared to the monoblock design. The developed version of the design would become known as the Proton.

This had the advantage of easier installation of the upper stages and payload due to the smaller length of the first stage. This variant was studied in Filial 1 under the lead engineer E. T. Radchenko. The polyblock design received patent number 36616 in 26 July 1966. Named on the patent were V N Chelomei, V N Bugayckiy, V A Birodov, G D Dermichev, N I Yegorov, V K Karrask, Yu P Kolesnikov, Ya B Nodelman, and E T Radchenko.

The design mass and engine performance figures for this version have been given; the calculated payload is 12,000 kg. This is coincidentally very close to the 12,200 kg payload mass given (incorrectly) at the time of the launch of the two-stage variant of the launch vehicle, Proton 1.

Manufacturer: Chelomei. LEO Payload: 12,000 kg (26,000 lb). to: 200 km Orbit. Liftoff Thrust: 8,119.800 kN (1,825,404 lbf). Total Mass: 554,940 kg (1,223,430 lb). Core Diameter: 4.10 m (13.40 ft). Total Length: 43.00 m (141.00 ft).

• Stage Number: 1. 1 x Stage: UR-500 Polyblock Stage 1P. Gross Mass: 378,900 kg (835,300 lb). Empty Mass: 26,900 kg (59,300 lb). Thrust (vac): 8,989.700 kN (2,020,965 lbf). Isp: 310 sec. Burn time: 119 sec. Isp(sl): 280 sec. Diameter: 4.10 m (13.40 ft). Span: 7.40 m (24.20 ft). Length: 21.20 m (69.50 ft). Propellants: N2O4/UDMH. No Engines: 4. Engine: 8D43 + 11D43. Status: Design 1962. Original 'Polyblock' design for Proton first stage. This was selected configuration; although somewhat greater in dry mass, it had the advantages of shorter length.

• Stage Number: 2. 1 x Stage: UR-500 Stage 2. Gross Mass: 137,700 kg (303,500 lb). Empty Mass: 16,000 kg (35,000 lb). Thrust (vac): 3,183.200 kN (715,612 lbf). Isp: 320 sec. Burn time: 119 sec. Diameter: 4.10 m (13.40 ft). Span: 4.10 m (13.40 ft). Length: 10.90 m (35.70 ft). Propellants: N2O4/UDMH. No Engines: 4. Engine: RD-0213. Status: Design 1962. Original Proton second stage design.

• Stage Number: 3. 1 x Stage: UR-500 Stage 3. Gross Mass: 23,940 kg (52,770 lb). Empty Mass: 2,180 kg (4,800 lb). Thrust (vac): 613.110 kN (137,833 lbf). Isp: 320 sec. Burn time: 110 sec. Diameter: 4.10 m (13.40 ft). Span: 4.10 m (13.40 ft). Length: 3.70 m (12.10 ft). Propellants: N2O4/UDMH. No Engines: 1. Engine: RD-0212. Status: Design 1962. Original Proton third stage design.

• Afanasyev, Igor, Novosti kosmonavtiki, "35 let RN Proton", 1998, Issue 5, page 40.