S-IV

S-IV
	Schematics of the S-IV
Manufacturer	Douglas Aircraft Company
Country of origin	United States
Used on	Saturn I (stage 2)
General characteristics
Height	12.19 m (40.0 ft)
Diameter	5.49 m (18.0 ft)
Gross mass	50,576 kg (111,501 lb)
Propellant mass	45,359 kg (100,000 lb)
Empty mass	5,217 kg (11,500 lb)
Launch history
Status	Retired
Total launches	6
Successes; (stage only)	6
Failed	0
First flight	January 29, 1964
Last flight	July 30, 1965
S-IV 100 series
Powered by	6 RL-10 engines
Maximum thrust	400 kN (90,000 lbf)
Specific impulse	410 s (4.0 km/s)
Burn time	482 s
Propellant	LH2 / LOX

The S-IV was the second stage of the Saturn I rocket used by NASA for early flights in the Apollo program.

The S-IV was manufactured by the Douglas Aircraft Company and later modified by them to the S-IVB, a similar but distinct stage used on the Saturn IB and Saturn V rockets.^[1]

The S-IV stage was a large LOX/LH₂-fueled rocket stage used for the early test flights of the Saturn I rocket. It formed the second stage of the Saturn I and was powered by a cluster of six RL-10A-3 engines. Each one of the engines supplied 66.7 kilonewtons (15,000 lb_f) of thrust for a total of about 400 kilonewtons (90,000 lb_f). The cryogenic LH₂ (liquid hydrogen) and LOX (liquid oxygen) tanks were separated by a common bulkhead. The forward bulkhead of the LOX tank formed the aft bulkhead of the LH₂ tank. This saved up to 20% of structural weight.^[2]^[3]

Flight history


Mission serial number	Launch date (UTC)	Launch notes
SA-1	October 27, 1961 15:06:04	First test flight. Block I. Suborbital. Range: 398 km. Apogee: 136.5 km. Apogee Mass: 115,700 lb (52,500 kg). Dummy S-IV and S-V stages.
SA-2	April 25, 1962 14:00:34	Second test flight. Block I. Suborbital. 86,000 kg water released at apogee of 145 km as part of Project Highwater. Dummy S-IV and S-V stages.
SA-3	November 16, 1962 17:45:02	Third test flight. Block I. Suborbital. 86,000 kg water released at apogee of 167 km. Dummy S-IV and S-V stages. Second and last Project Highwater flight.
SA-4	March 28, 1963 20:11:55	Fourth test flight. Block I. Suborbital. Dummy S-IV second stage and S-V third stage. Apogee: 129 km. Range: 400 km.
SA-5	January 29, 1964 16:25:01	First live S-IV second stage. First Block II. First to orbit: 760 x 264 km. Mass: 38,700 lb (17,550 kg). Decayed 30 April 1966.
SA-6	May 28, 1964 17:07:00	First Apollo boilerplate CSM launch. Block II. Orbit: 204 x 179 km. Mass: 38,900 lb (17,650 kg). Apollo BP-13 decayed 1 June 1964.
SA-7	September 18, 1964 16:22:43	Second Apollo boilerplate CSM launch. Block II. Orbit: 203 x 178 km. Mass: 36,800 lb (16,700 kg). Apollo BP-15 decayed 22 September 1964.
SA-9	February 16, 1965 14:37:03	Third Apollo boilerplate CSM. First Pegasus micrometeoroid satellite. Orbit: 523 x 430 km. Mass: 3,200 lb (1,450 kg). Pegasus 1 decayed 17 September 1978. Apollo BP-26 decayed 10 July 1985.
SA-8	May 25, 1965 07:35:01	Fourth Apollo boilerplate CSM. Only night launch. Second Pegasus micrometeoroid satellite. Orbit: 594 x 467 km. Mass: 3,200 lb (1,450 kg). Pegasus 2 decayed 3 November 1979. Apollo BP-16 decayed 8 July 1989.
SA-10	July 30, 1965 13:00:00	Third Pegasus micrometeoroid satellite. Orbit: 567 x 535 km. Mass: 3,200 lb (1,450 kg). Pegasus 3 decayed 4 August 1969. Apollo BP-9A decayed 22 November 1975.