Saturn INT-21

American orbital launch vehicle. Saturn variant consisting of S-IC first stage and S-II second stage. This essentially flew once to launch Skylab in 1972, although the IU was located atop the Skylab space station (converted S-IVB stage) rather than atop the S-II as in the INT-21 design.

Liftoff Mass - kg	S-IC - No. F-1 Motors	S-II - No. J-2 Motors	Payload - kg - 4.68 G limit
2,209,000	4	3	76,000
2,209,000	4	4	84,000
2,209,000	4	5	89,000
2,762,000	5	3	101,000
2,762,000	5	4	112,000
2,762,000	5	5	116,000

LEO Payload: 115,900 kg (255,500 lb) to a 185 km orbit at 28.00 degrees. Flyaway Unit Cost 1985$: 681.500 million.

Stage Data - Saturn INT-21

• Stage 1. 1 x Saturn IC. Gross Mass: 2,286,217 kg (5,040,245 lb). Empty Mass: 135,218 kg (298,104 lb). Thrust (vac): 38,703.160 kN (8,700,816 lbf). Isp: 304 sec. Burn time: 161 sec. Isp(sl): 265 sec. Diameter: 10.06 m (33.00 ft). Span: 19.00 m (62.00 ft). Length: 42.06 m (137.99 ft). Propellants: Lox/Kerosene. No Engines: 5. Engine: F-1. Status: Out of Production.

• Stage 2. 1 x Saturn II. Gross Mass: 490,778 kg (1,081,980 lb). Empty Mass: 39,048 kg (86,086 lb). Thrust (vac): 5,165.790 kN (1,161,316 lbf). Isp: 421 sec. Burn time: 390 sec. Isp(sl): 200 sec. Diameter: 10.06 m (33.00 ft). Span: 10.06 m (33.00 ft). Length: 24.84 m (81.49 ft). Propellants: Lox/LH2. No Engines: 5. Engine: J-2. Status: Out of Production.