How Successful was Black Knight?

The rocket itself had a relatively simple task to perform, which was to boost its payload as high as possible, from where the re-entry vehicles would fall with as great a velocity as possible. Some launches were completely successful in that the rocket and the experiments yielded all the data required. Sometimes the launches were successful, but the experiments failed, yielding little data. However, even when the vehicle’s performance was below optimum, the experiments could still yield good results.

Failures that would have jeopardised orbital attempts had less impact on re­entry studies. The very first flight of all, BK01, ended prematurely when the destruct system operated inadvertently. There were also problems with engine overheating leading to kerosene starvation and resultant ‘cold thrusting’, particularly in the second (BK03) and fourth flights (BK05), but again, these were solved relatively early in the programme. ‘Cold thrusting’ occurs when the engine consumes HTP in the absence of kerosene: decomposition still takes place, but the thrust is very sharply reduced. In addition, on many flights the kerosene was exhausted before the HTP, resulting in a few seconds of cold thrust after ‘all burnt’. The discrepancy between the calibration during test firing and the actual launch was never pinned down.

The first stage of the vehicle performed exactly as intended on 15 of the 22 Black Knight flights. Other launches had problems in one way or another:

BK01: the self-destruct mechanism was accidentally triggered near the end of the flight.

BK03 and BK05: overheating in the engine bay lead to a fuel lock in the kerosene pipes, resulting in a long period of cold thrusting.

BK07: one chamber reverted to cold thrust after 100 seconds. Over 80% nominal velocity achieved.

BK14: pipe failure caused loss of kerosene: cold thrusting after 130 seconds. 85% nominal velocity achieved.

BK12: 6.8% difference in mixture ratio between flight and calibration.

BK23: premature shut down of engine due to gearbox failure 3 seconds before expected flame out.

Of the 22 flights listed, seven would not have made it into orbit if they had been satellite launch vehicles. Most of these problems could be considered as developmental difficulties that occur with any new technology. As a very first attempt at a modern liquid fuel ballistic vehicle, this is a fairly good record, with no major failures at all. It is also a tribute to the engineers at Saunders Roe and at Armstrong Siddeley Motors.

However, Black Knight was a success in a different direction. It gave RAE the confidence in the basic design, and as a consequence, many further projects were proposed using Black Knight as a basis. One, of course, was the Black Prince launcher and its various derivatives discussed in the BSSLV chapter. Another was Black Arrow – the subject of the next chapter.