UR-500 Monoblock Credit - © Mark Wade

During UR-500 design studies, two variants of the first stage were considered: polyblock and monoblock. The monoblock approach was that the first stage be assembled from two separate modules with the same diameter: an upper oxidiser module and a lower fuel and engine block. In assembly trials of this design it proved difficult, because of the height of the first stage, to obtain access to the upper stages and payload atop the rocket. Although there was a payload advantage compared to the more compact polyblock design, this was relatively small and outweighed by the operational difficulties. This variant was studied by Chelomei’s Filial Number 1, Chief Designer V N Bugayskiy, under the lead engineer M S Mishetyan.

The design mass and engine performance figures for this version have been given; the calculated payload is 12,000 kg.

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: 543,400 kg (1,197,900 lb). Core Diameter: 6.20 m (20.30 ft). Total Length: 54.00 m (177.00 ft).

• Stage Number: 1. 1 x Stage: UR-500 Monoblok Stage 1M. Gross Mass: 367,360 kg (809,890 lb). Empty Mass: 25,560 kg (56,350 lb). Thrust (vac): 8,989.700 kN (2,020,965 lbf). Isp: 310 sec. Burn time: 115 sec. Isp(sl): 280 sec. Diameter: 6.20 m (20.30 ft). Span: 6.20 m (20.30 ft). Length: 30.00 m (98.00 ft). Propellants: N2O4/UDMH. No Engines: 4. Engine: 8D43 + 11D43. Status: Design 1962. Original conventional 'Monoblock' design for Proton first stage.

• 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.