Saturn IB

NASA’s Historical Data Book gives the Saturn IB a total height of 68.3 metres with spacecraft and escape tower, 6.6 metres in diameter, and first stage thrust of 7,116,800 newtons from eight Rocketdyne H-1 engines. The Apollo-Soyuz press kit rounds the same stack to 224 feet and the thrust to 7.3 million newtons, 1.64 million pounds. Strip the spacecraft off and the vehicle alone is about 43 metres, which is where the lower figures in circulation come from. Payload is about 40,000 pounds to low Earth orbit, 18,144 kilograms, per NASA’s Apollo 7 press kit.

The first stage geometry is an accident of poverty. Fabricating a single six metre tank meant new tooling and new welding techniques, and the Army Ballistic Missile Agency had already signed away half its available funds to Rocketdyne to get the H-1 engine. So they used what was lying around: partial rejects and incomplete 1.78 metre Redstone tanks and 2.67 metre Jupiter tanks, bundled eight around one. As Heinz Mrazek put it, the dire need made them more inventive. NASA’s own history calls the result a weird compromise and says it was never intended to look like a streamlined vehicle for the exploration of space.

Nobody believed the cluster would work. Von Braun recalled that people still had trouble persuading individual rocket motors to fire reliably, "and here we said we would fire up all eight simultaneously". There were jokes about Cluster’s Last Stand. Not until the third static run, on 29 April 1960, did they light all eight, and then only for eight seconds. The Pentagon was no more enthusiastic: the Secretary of Defense twice refused Saturn a priority rating, in December 1958 and again in May 1959, on the view that it was simply too big for any military mission.

Saturn IB is Saturn I with the S-IV second stage swapped for the hydrogen-burning S-IVB and the first stage uprated. It flew nine times and succeeded nine times: three uncrewed Apollo qualification flights in 1966, the first test of the lunar module in space, Apollo 7 with the first Apollo crew on 11 October 1968, all three Skylab crews in 1973, and Apollo-Soyuz on 15 July 1975. It never left low Earth orbit and never carried anyone to the Moon.

When it stopped, two complete flight vehicles were left over. SA-209 and SA-211 went into storage, the first stage at Michoud, the second stage at Kennedy, the instrument unit at Marshall. The Saturn family retired with what NASA counts as a 100 percent success rate across 32 launches, and with two working rockets that nobody ever launched.