A Liquid Hydrogen Stage

One way round this limitation was to use a high energy upper stage, and so at the same meeting in December 1960 Saunders Roe were asked to consider a liquid hydrogen third stage with 4,500 lb of propellants. The brochure they produced was up to their usual high standard, laying down the problems clearly, and describing the solutions equally clearly. This design and that of RPE has been described in the chapter on rocket motors, so no more about the designs themselves need be said here. The cost of developing a liquid hydrogen stage for the BSSLV was put at between £5.5 million and £7 million.

Saunders Roe did hedge their bets somewhat at the instigation of RAE: the design might have been tailored to the BSSLV, but it was also drawn up with the possibility of mounting it on the French second stage which was now being negotiated. The prolonged European negotiations were slowly getting somewhere, although it would take many more months before any clear shape would emerge. At a meeting in March 1961 at Cowes, the RAE had to tell Saunders Roe that it had now been definitely decided that the second stage would be of French design. Saunders Roe and Bristol Siddeley were to continue with the design for the third stage, with particular emphasis on liquid hydrogen. At the same meeting, Saunders Roe reported that manufacture of the second stage tank structural test specimen was about 25% complete. Although it might seem that the work on the HTP second stage had been wasted, it carried through first to the 54-inch Black Knight and then to the second stage of Black Arrow.

In a further Design Study Progress meeting in July, the chairman noted that the situation was very vague (which, given the ELDO negotiations, was probably an understatement). He hoped that Saunders Roe would play a part in any future design studies and that they would continue to maintain a design study team. At the same meeting, Saunders Roe presented a brochure for the HTP/kerosene third stage, which would involve both high thrust and low thrust stages; a 2V hour period of low thrust was mentioned, and in addition, there was a further report on their liquid hydrogen stage. But this is effectively where work on Black Prince, or BBSLV, comes to a halt. Instead, attention turned to ELDO and Europa.

It might be thought that the creation of ELDO would have finally put the lid on any further thoughts of a BSSLV, but RAE was still doing its best to resurrect the idea. Throughout 1963 and 1964, meetings were being held between RAE and Saunders Roe on ‘medium energy upper stages’. This is a euphemism for HTP stages. In a meeting in June 1963, the chairman of the Working Party, H. G.R. Robinson of RAE, stated that ‘a study of upper stages for Blue Streak were needed as a back-up of the system studies for the E. L.D. O. launching vehicle, in case the latter was not available, or unsuitable’10.

The RAE was considering designs for circular equatorial orbits of either 13,740 km or 36,060 km height – i. e. 12-hour or 24-hour orbits. This would need an apogee motor for a final stage. In a follow up meeting, Saunders Roe were told that they would be given design contracts for ‘An Investigation on British End Stages in combination with the Blue Streak Launcher Vehicle’, and ‘in view of possible ELDO
involvement, RAE recommended that the proposed body diameter be 2 metres (i. e. 6.5 ft.)’11. Although Saunders Roe duly undertook the design studies as requested, they never went past the paper stage. On the other hand, the link to what would become Black Arrow becomes more obvious.

During 1963 and 1964, the design for what would become Black Arrow was evolving. Amongst all the imperial measurements of feet, inches and pounds is a first stage diameter of 2.0 m! This mixing of units not only seems odd but also would seem to have no connection with Blue Streak. However, the ELDO vehicle was being designed with a French second stage, which was also to be of

2.0 m diameter. The idea was then that if the Blue Streak interstage were to be suitable for the French vehicle, it would also be suitable for Black Arrow. In the event, there was a problem, since the Blue Streak side of the interface was much wider; the French stage was to have a skirt that would mate with the lower stage. So this odd metric feature was included in case, as seemed possible in 1963, ELDO did not go ahead, or, for whatever reason, was not a success.

Figure 60 shows a comparison between Blue Streak with Black Arrow mounted on top and Europa. The 54-inch diameter of the payload shrouds may have been a problem for a conventional satellite, although not for a communications satellite, where the payload might be quite small. The other problem was that Blue Streak might have been struggling to lift the 40,000 lb weight of Black Arrow.

But the design for Europa did materialise, and it might then be thought that all further suggestions for a solely British launcher might have died forever. However, there was one enthusiast for space exploration in the House of Commons, the Conservative MP Neil Marten, who asked a Question in the House about the possibilities of the Blue Streak/Black Knight combination. This might well have been a put up job, but it gave RAE the excuse to work the figures for a Ministerial reply, a task they set to work on with eagerness.12

This was in March 1968, when Europa, despite problems with its second stage, still looked viable. Two versions were considered. The first employed the first stage only of Black Arrow, with four of the eight chambers and one of the turbopumps deleted. The payload estimate was for 1,800 lb in a 200 NM polar orbit (750 kg at 500 km); however, extended nozzles on the motors (as in the Black Arrow second stage) resulted in an improvement on this of ‘some 20% to 25% giving a performance appreciably greater than ELDO A’. Adding the third stage of Black Arrow – the Waxwing motor – would increase payloads ‘by about
200 kg’. This would put the maximum payload up to 1,100 kg. Development costs were put at £1 million, and the unit cost per vehicle at £1.5 million.

A follow-up note gives some interesting comparisons between ELDO A and the Blue Streak/Black Arrow combination.

	Black Arrow	ELDO A	ELDO A
	Stage	2nd Stage	3rd Stage
Vacuo S. I.	250.5	280.8	292
Burnable Props. (kg)	13256	9800	2498
Mass of stage (kg)	1134	2389	737
Structural efficiency	0.079	0.196	0.200
Ideal velocity*	6244	4489	4610
Ideal velocity**	4636	2366	2714

* from stage itself (m/s) ** from stage when used as part of multi-stage vehicle

This shows the potential of a Blue Streak/Black Arrow combination. It also shows up very clearly the structural efficiency of Black Arrow as opposed to the ELDO second stage.

Equally interesting are the costings, for what they are worth:

HSD for work on Blue Streak:

Rolls Royce for work on Black Arrow motor: Westland – Black Arrow modifications Motor bays

Ground equipment modifications:

Modifications at Woomera say Total

[sic – total is actually £860k!]

Cost of first flight vehicle: Blue Streak £1000k

Black Arrow £400k – say £1500k total.

To carry out the modifications and launch one test vehicle for £2Уг million seems a touch on the optimistic side.

There were, of course certain snags. To do this in parallel with Europa would have been politically unacceptable (but it would have been interesting to see the reactions if the Blue Streak/Black Arrow combination had reached orbit by 1970). There was also the question of payload – but the Perigee Apogee System (PAS) design could have been adapted from ELDO to give a geostationary capability.

At around the same time, Saunders Roe produced their own brochure for a Blue Streak/Black Arrow combination. The skirt to the engine bay was flared out to match the Europa interface, as originally intended. They went through all the permutations with their usual thoroughness, considering eight chamber and four chamber variants, two – and three-stage versions, and also reviving the liquid hydrogen third stage possibility. Their payload calculations were on the optimistic side, however, since they estimated that Blue Streak and Black Arrow together could put as much as 3,000 lb in low earth orbit, and even a few hundred pounds in a geosynchronous orbit.

It is interesting to note that Saunders Roe were obviously thinking of communications satellites as an application for the launcher. Under the payload shroud the satellite is sketched with two solid fuel motors: one which would convert a low Earth circular orbit into a highly elliptical geotransfer orbit, and the second of which would then act as an apogee motor to convert the elliptical orbit into a circular geosynchronous orbit. In this context, it should be noted also that although the US was prepared to sell launchers to other countries, this offer was subject to considerable restriction and would almost certainly not have included commercial communications satellites. Britain’s military communications satellites, Skynet, were launched by the US only as a result of the close military ties between the two countries. Thus Britain might have been able to produce a low cost launcher for communication satellites – but not a very powerful one.

However, there was a considerable divergence in views between the establishments and the Ministries. The RAE and its associated establishments were constantly producing ideas based on Blue Streak, yet it was obvious that the Ministry of Technology, as the Ministry of Aviation had then become, was firmly set against any idea of a British-based launcher, and certainly, as already mentioned, it would have been politically unacceptable whilst ELDO was still in existence. It would also have been financially unacceptable as far as the Treasury was concerned.