The F-l: a brutal machine

The F-l rocket engine is still one of the most powerful liquid-fuelled engines ever built and one with a distinguished service record. An uprated version of the engine, the F-1A, underwent trials and reached 17 per cent greater thrust but it was never brought into service. The Russian-designed RD-170. which saw service in the late 1980s, gave 12 per cent more thrust with greater efficiency.

The F-l began as an Air Force programme in 1955, which NASA then nurtured for its bigger missions. It was ideal as an engine for a first-stage cluster in a huge booster owing to its prodigious power, but its gestation was as difficult as any in the Apollo;Saturn story. In operation, a single engine consumed a total of nearly three tonnes of kerosene and liquid oxygen every second and produced a force that could balance 690 tonnes of mass. It became obvious in its development that simply scaling up the design of contemporary engines was not going to work. Injecting so much propellant into a huge 90-centimetre chamber often led to brutal combustion instability that destroyed engine after engine. It took nearly five years of trial and error for engineers at the Rockeidyne company to tame the F-l to the point where a

small bomb could be ignited within its combustion chamber and the resultant instability would dampen itself out within half a second.