# Saturn C-2

The Saturn C-2 was the second rocket in the Saturn C series studied from 1959 to 1962. The design was for a four-stage launch vehicle that could launch 21,500 kg (47,300 lb) to low Earth orbit and send 6,800 kg (14,900 lb) to the Moon via Trans-Lunar Injection. The C-2 design concept was for a proposed crewed circumlunar flight and the Earth orbit rendezvous (EOR) missions. It was initially considered for the Apollo lunar landing at the earliest possible date (1967).

## Launch vehicle requirements

On 30 September 1960, the fourth meeting of the Space Exploration Program Council was held at NASA Headquarters. The results of a study on Saturn development and utilization were presented by the Ad Hoc Saturn Study Committee. Objectives of the study were to determine:
* If and when the Saturn C-2 launch vehicle should be developed.
* If mission and spacecraft planning was consistent with the Saturn vehicle development schedule.
Since no change in the NASA FY1962 budget was contemplated, the Committee recommended that the Saturn C-2 development should proceed on schedule (S-II stage contract in FY 1962, with first flight in 1965).
The C-2 would be essential for Apollo crewed circumlunar missions, lunar uncrewed exploration, Mars and Venus orbiters and capsule landers, probes to other planets and out-of-ecliptic, and for orbital starting of nuclear upper stages. During a discussion on the Saturn program, several major problems were brought up:
* The adequacy of the Saturn C-1 launch vehicle for the orbital qualification of the complete Apollo spacecraft was in question. Although the C-1 could be used to launch a command module of 5,100 pounds, it was probable that the command module weight would increase to as much as 8,000 pounds, George M. Low of NASA Headquarters, in a critical review of the Apollo program, pointed out that a spacecraft for a circumlunar mission could be constructed within the payload limit of the C-2 launch vehicle. Both the developmental and production spacecraft could be available to meet the Saturn schedules.
* Much basic research would be needed before the first Apollo flight, In particular, the problem of reentry heating was of great concern. Low noted that a prediction criterion for proton beam events had been developed, making possible safe crewed circumlunar flights insofar as the radiation exposure problem was concerned.
* Concern was also expressed as to the possible need and availability of additional personnel to support the Apollo program.

## Changing configurations

During 1961 Saturn C-x configurations seemed to change month by month. In February 1961, the C-2 design finalized as a three-stage vehicle for Earth-escape missions, using an S-II second stage. It was calculated that 15 launches and rendezvous of the C-2 would have been required to assemble a lunar spacecraft in Low Earth orbit. By May 1961, a more powerful vehicle was desired for circumlunar missions, hence the C-2 was dropped in favor of the Saturn C-3. Further development of the C-2 vehicle was cancelled on 23 June 1961.

## Launch vehicle design

The original Saturn C-2 design (1959-1960) was a four-stage launch vehicle, using an S-I first stage with eight Rocketdyne H-1 engines, later flown on the Saturn I. The Army's original design used the S-III stage with two J-2 engines as the second stage; after the Saturn program was transferred to NASA, the second stage was replaced with an S-II second stage using four J-2 engines. The S-III stage would have been added atop the S-II, to convert the C-2 into the five-stage Saturn C-3. Later, a fifth J-2 engine was added to the S-II stage to be used on the Saturn C-5, which eventually was developed as the Saturn V launch vehicle.
The S-IV, later flown on the Saturn I, was to serve as the third C-2 stage and fourth C-3 stage; and an S-V Centaur would be the fourth C-2 stage. While this S-V/Centaur stage would never fly on any Saturn rockets, it would be used on Atlas and Titan launch vehicles. Modern versions of the Centaur are still in use on Atlas V and Vulcan.