The Saturn II Launch System
The Saturn II Launch System (SLS) is made up of the S-IF first stage, which boosts the stack to over 200,000 feet before returning to Kennedy Space Centre and a second stage; derived from the ever-useful and ageless S-IVB, which completes orbital insertion.
While the Nixon Administration decided against the development of a reusable launch system (to be known as the Space Shuttle) in 1972, NASA engineers and private industry independently pursued research into so-called ‘flyback’ boosters as an alternative to continuing use of disposable rocket stages. They would send a payload on their way to orbit before returning to land at Kennedy Space Centre. A short overhaul would follow before the booster would be ready for its next launch.
A reusable booster of this kind, it was surmised, would reduce costs and turnaround time between launches, with little more required than refuelling and restacking on the launch pad. History shows that to have been overly optimistic, but it is unlikely that the US space programme could have continued at the intensity it did in the 1990s had it continued to rely on disposable launch vehicles alone.
In 1981, planning and preparation for the Ares mission was continuing at pace, with flight tests of the Interplanetary Injection Booster (IIB) and the Mars Exploration Module (MEM). An influential report on the future of the manned space programme, written by former NASA Manager and systems engineer Joseph O’Shea, suggested that a reusable, fly back booster be developed to replace the Saturn I Evolved Launch Vehicle (ELV) that launched three missions a year to the latest Skylab workshop, by 1990.
McDonnell Douglas rose to the challenge, meeting the long-cherished ambition of NASA to retire the S-I stage, the oldest and most inflexible part of the Saturn launch family. Scampish journalists termed it ‘Mueller’s Revenge’, when George Mueller: a strong proponent of the Space Shuttle in the late 1960s, returned to NASA to manage Saturn II development and integration in 1983.
Construction of the first of four S-IF boosters began in 1985, and flight test articles took to the sky for the first time the week before the Ares mission touched down at Mangala Valles.
The payload for the Saturn II was initially the Apollo Command and Service Module (CSM), in its role as a crew transport and logistic vehicle. The first CSM launched by Saturn II docked with Skylab in 1991. The S-IF stage operated nominally, sending Apollo-Skylab 91B on its way before returning to land at KSC’s Booster Landing Facility – a 15,000-foot runway built specially for this purpose.
The maiden flight was followed by a series of interplanetary probes, earth observation satellites and, controversially, US military payloads, alongside the three flights a year to the orbital station.
Thirty years after its first launch, and after almost 130 flights, the CSM was replaced by the Hermes Crew Vehicle in 1997, which, launched by the Saturn II, continues to be the backbone of NASAs manned space programme today.