Saturn INT-21

The Saturn INT-21 was a study for an American orbital launch vehicle of the 1970s.^[1] It was derived from the Saturn V rocket used for the Apollo program, using its first and second stages and capable of placing 115,900 kg (255,500 lb) to LEO, but lacking the third stage.^[2] The guidance unit would be moved from the top of the third stage to the top of the second stage. The INT-21 was never flown.

Saturn INT-21

The Saturn INT-21 would have been similar to the Saturn V which launched the Skylab space station, on May 14, 1973
Function	Launch vehicle
Manufacturer	Boeing (S-IC) North American (S-II)
Country of origin	United States
Size
Height	98.5 m (323 ft) (without payload)
Diameter	10.06 m (33.0 ft)
Mass	2,916,080 kg (6,428,860 lb)
Stages	2
Capacity
Payload to LEO
Mass	115,900 kg (255,500 lb)
Launch history
Status	Study
Launch sites	LC-39A, Kennedy Space Center
Total launches	0
First stage - S-IC
Engines	5 Rocketdyne F-1
Thrust	34.02 MN (7,650,000 lbf)
Burn time	150 seconds
Propellant	RP-1 / LOX
Second stage S-II
Engines	5 Rocketdyne J-2
Thrust	5 MN (1,100,000 lbf)
Burn time	360 seconds
Propellant	LH2 / LOX

A related variant was launched once, from the Kennedy Space Center, Florida carrying the Skylab space station into orbit, at 17:30 UTC, on May 14, 1973.^[3][4][5] As Skylab was built from an S-IVB stage, there was no need to move the guidance unit. This version was intended to be used for other flights in the Apollo Applications Program, and would have also been used to launch other American space stations,^[5] including Skylab B.

See also

• Comparison of orbital launch systems
• Saturn I
• Saturn IB
• Saturn I SA-1