A Black Knight IRBM

One rather unusual proposal surfaced at the time when Skybolt was cancelled. At the subsequent Nassau conference in December 1962, Macmillan was able to persuade President Kennedy to provide Polaris, effectively without strings. This seemed to be distinctly improbable at the outset, and there was obviously a short period of almost panic in the British delegation. Without Skybolt and without Polaris, Britain would have been thrown back entirely on its own resources, which were then very few. Sir James Lighthill, at that time Director of RAE, came up with a proposal for a missile based on Black Knight and wrote a note for Macmillan headed ‘A Possible British Deterrent’. It begins by saying:

Advances in technology make it possible, today, to do Blue Streak’s job with a rocket at one tenth of Blue Streak’s weight. The main advances have been in reduction of weight of warhead, and the perfection of the technique of the two-stage rocket, whose first stage is shed after it has burnt itself out.1

He then put forward the idea that:

… The very successful research vehicle BLACK KNIGHT (an entirely British development began in 1956 as a ‘lead into’ BLUE STREAK and first fired 2U years later) could now do the job with a small second stage. Several two stage rockets with BLACK KNIGHT as first stage have actually been fired. In the last three firings, all systems (including first and second stage separation, and complex data processing and transmission systems) worked as planned. In all fourteen firings of BLACK KNIGHT, the first stage flew successfully.

For delivery of nuclear warheads over 1500 nautical miles (the London Moscow distance), a suitable second stage would be one using the extremely well tried Gamma 201 engine (of 4000 pound thrust). Guidance would be based on the Ferranti miniature stable platform, of which the prototype has already been satisfactorily tested.

The fuels would be kerosene and hydrogen peroxide (which can be stored at room temperature for a whole month). The missiles can be fired from small hardened sites (a tenth of the size contemplated for BLUE STREAK), and would be vulnerable to a megaton explosion only if it took place less than half a mile away.

The system suggested would use proven components that started development in 1956. It would probably reach the first flight after two years of further development (at high priority), and begin to come into service after another two years (and some 30 test flights).

A tentative estimate of research and development cost includes £15m. spent on the missiles plus £20m. on the Woomera range, which I add together around up to £50m. The cost of operational missiles and launch sites is estimated at £200,000 and £500,000 respectively, which I add together around up to £1m. per missile. These figures suggest that for £100m. (essentially what remains to be spent by us on SKYBOLT) we could have 50 of these rockets. (They would be simpler and cheaper than the US rocket Minuteman because of the much shorter range required).2

In the end, Britain did acquire Polaris without strings, but Lighthill’s suggestion was probably the most viable if Britain wanted to retain its deterrent yet ‘go it alone’. Certainly some form of Black Knight would be the only ballistic missile which could have been developed in less than five or six years, and by far the cheapest.

Obviously RAE followed up this idea later, when the dust had settled:

An investigation was recently made into the possible use of Black Knight as an IRBM Two cases were considered, both based on the 54" Black Knight with a sea level thrust of 25,000 lb weight. The first assumes that HTP and kerosene were the propellants, with a vacuum specific impulse of 250 secs; the second that the specific impulse can be raised to 280 secs by using propellants such as NTO/UDMH. In both cases the second stage used the same propellants as the first stage. The maximum range of an 800 lb re-entry vehicle was found to be just over 1000 n. miles with the HTP/kerosene combination and 1500 n. miles with NTO/UDMH.3

And later in the report: ‘It was found that a second stage weight of 3500 lb at a thrust of 6000 lb was about the optimum.’

Changing fuels would have negated one of the major advantages of the proposal: it was simple, cheap and made use of existing and proven hardware.

It is curious that a much more useful proposal was not pressed into service at this point. The 1958 proposal for an IRBM from Armstrong Siddeley, resurrected in 1960 (described in the Black Arrow chapter), would have been eminently suitable. The design is basically a much enlarged Black Knight, but instead of the small Gamma engine (4,000 lb thrust), it uses the large Stentor chamber: 24,000 lb thrust. Thus the proposed vehicle is six times more massive. It would have been easy enough to put a small second stage on top, and it would certainly have had the range to reach Moscow.

As an alternative missile to Blue Streak, it had the advantage that the propellants are storable, or reasonably so. Certainly, HTP would be easier to handle than liquid oxygen within a silo, and could be stored in the missile for long periods – months rather than weeks.

Certainly, an alternative history or counter-factual for Nassau would be interesting: what would Macmillan have done if Polaris was not available, or at least hampered by a sufficient number of strings as to make it political unpalatable? The only possibilities were some sort of air-launched missile (a ramjet cruise missile, the X-12 or Pandora, was being suggested at the time), or (with a large number of people having to eat quite a few words) a land-based missile, and here a Black Knight derivative is an obvious choice. Like Titan II and unlike Blue Streak, the fuels were storable in the missile, making for a much more credible weapon.

It is interesting, although coincidental, that such a missile would have looked very much like Black Arrow, whose development costs were a mere £10 million. The first flight of Black Arrow was in June 1968, and, given proper funding, this could have been reduced by at least two years or more. Lighthill had noted that it was now possible ‘to do Blue Streak’s job with a rocket at one tenth of Blue Streak’s weight’. That was perhaps a touch optimistic, but Black Arrow at 40,000 lb was actually a fifth of the weight of Blue Streak’s 200,000 lb.