Atlas (familia) version
Atlas (familia) Atlas-Centaur
The Atlas topped by Centaur, the first rocket stage in the world to burn liquid hydrogen. Its development was painful and was nearly cancelled twice, yet it went on to launch the Surveyor landers, the Pioneer probes and most of the Mariner programme. The line that starts here runs unbroken to the Atlas V.
- May 8, 1962
- First launch
- No
- Reusable
History
Liquid hydrogen
Centaur was the first rocket stage to burn liquid hydrogen and liquid oxygen. The performance was outstanding, but hydrogen has to be kept colder than liquid oxygen and gives little mass for a great deal of volume, so the stage needed very large tanks. Convair designed it around the same pressure-stabilised tank construction as the Atlas, partly out of engineering conviction and partly because that allowed it to be built on the existing production line.
The booster had to be adapted in turn: an uprated booster section with twin turbopumps on each engine, a structure strengthened for such a heavy upper stage, and lengthened propellant tanks.
A programme that almost died
The first vehicle reached the Cape in October 1961 and sat on the pad for seven months while hydrogen leaked through the intermediate bulkhead and guidance and propulsion faults were chased down. When it finally flew, in May 1962, an insulation panel tore away during ascent, hydrogen tank pressure ran away and the vehicle broke up less than a minute after lift-off.
A congressional inquiry called the management of the programme weak, and there were proposals to abandon Centaur in favour of another launcher. President Kennedy suggested cancelling it outright and was talked out of it by the argument that settled the matter: experience with liquid hydrogen engines was essential to Apollo. Technical direction moved to NASA's research centre in Ohio, where the insulation panels and several other design flaws were put right.
The second flight, more than a year later, worked. The fifth ended in the largest pad explosion Cape Canaveral had seen, traced to booster fuel prevalves that opened only partway and starved the engines of kerosene.
From Surveyor to Atlas II
Once past that crisis, Atlas-Centaur became the workhorse of American scientific launches. All seven Surveyor spacecraft that set instruments on the Moon flew on it, as did the Pioneers bound for Jupiter and Saturn and most of the Mariner probes.
The vehicle kept growing in blocks: the original LV-3C, the SLV-3C with a stretched Atlas, and the SLV-3D with an uprated Centaur whose avionics absorbed those of the booster. That continuous evolution led to the Atlas I and Atlas II, and through them to the whole modern family.