Category A VERTICAL EMPIRE

Two stage. Launched 7 June 1961 20:50. Apogee 362 miles.

BK17 was another two-stage vehicle but with a lighter low-drag eroding head to give higher re-entry speed. The first stage performance was very good. The kerosene level sensor and HTP probes worked well and propellant usage in flight was determined. Visual observation and camera records of re-entry were confusing, but it soon became clear that the second stage had not functioned correctly. The head and tape recorder were recovered, and subsequent analysis of head tape record and body telemetry indicated that second stage separation occurred at re-entry and not at the end of first stage burning. It was possible to deduce from the records that the failure of second stage separation at first stage burn-out was due to failure of one of the two explosive bolts. In later vehicles explosive bolts and associated circuits were duplicated. At re-entry the second stage was torn off, followed by second stage burning.

The tape of the recorder in the head ran out before re-entry. In subsequent heads, the speed of the tape in the tape recorder was reduced so as to run for a longer period and ensure recording re-entry.

R3 was dispatched to Australia early in 1971, and the second stage arrived at Woomera on 26 July, followed by the first stage on 17 August. Static firing of the second stage occurred on 1 September, and the two stages and the back-up satellite had been assembled by 1 October. The complete vehicle was given a static firing test on 8 October, and the flight model satellite was fitted by 22 October. A decision was made to delay the launch until 26 October, but systems checking delayed the launch further.

Derek Mack, one of the Saunders Roe launch team (Saunders Roe had by then become the British Hovercraft Corporation), remembers the morning of 28 October as a cool, fresh Australian spring day, with clear skies. The overnight crew had filled the HTP tanks and adjusted the kerosene levels, as well as arming the many pyrotechnic systems on the vehicle. The gantry was wheeled back at 11:00, but there was some alarm when the Attitude Reference Unit, which steers the vehicle, began to give erratic signals. There was relief when it was realised that this was due to the vehicle swaying gently in the light breeze. The vehicle lifted off smoothly, and the various telemetry stations north of Woomera reported that all events had been successful. However, this did not yet mean that the launch had been successful: it was only when the global satellite station at Fairbanks reported an operational signal from a satellite on a frequency of 137 MHz that the team knew that they had an orbiting satellite. The party could begin, but there was a sour taste to it.

R3 launched the Prospero satellite (X3) into orbit on 28 October 1971, in a text book launch.19 The programme had meanwhile been cancelled by an announcement in Parliament by the new Minister at the Department of Trade and Industry, Frederick Corfield, on 29 July 1971. The teams that had built Black Arrow and launched it were out of a job.

Prospero had a mass of 66 kg, and was launched into an orbit of perigee 557 km, apogee 1,598 km, and an inclination to the equator of 82°. It is still in orbit. It carried four experiments:

(a) To determine the thermal stability of a number of new surface finishes.

(b) To determine the behaviour of new silicon solar cells.

(c) An experiment in hybrid electronic assemblies.

(d) An experiment by Birmingham University to determine the flux of micro meteorites.

The satellite was formed from eight faces covered with 3,000 solar cells. Since the spacecraft would be in the earth’s shadow for part of its orbit, rechargeable batteries were also carried.

The flight sequence for the Prospero satellite launch was:

Event Time (seconds)

Lift-off 0

First stage engine shut down (HTP depleted) 126.9 Stage separation/second stage ignition 133.5

Inter stage bay separation 139.1

Payload fairing separation 180.0

Second stage shut down (HTP depleted) 256.9

Pressurise attitude control system 262.5

Spin-up rockets 575.0

Stage separation 577.0

Third stage ignition 590.0

Payload separation 710.1

The fifth vehicle, R4, was never fired, and is now on display in the Science Museum, London.

Rocket motors work by ejecting gases at high speed. From the physics point of view, the momentum given to the gases will be counteracted by an equal and opposite momentum given to the rocket. Rocket motors are designed to make this momentum change as large as possible.

A change in momentum implies a force, since force x time = change in momentum. The force is given by change in momentum per second (strictly speaking, rate of change of momentum). This is usually referred to as the rocket thrust, measured in newtons, or, in Britain in the 1950s and 1960s, in lb – a shorthand for pounds force.

Gases moving at high speed have kinetic energy, and in almost all rocket motors this kinetic energy comes from chemical energy. With solid fuel motors, the fuel and the oxidant are melted together and poured into a casing to cool and solidify. Almost all liquid fuel rockets need both a fuel and an oxidant. There are a few chemicals which can be used by themselves (referred to as monopropellants) – hydrazine (N2H4) and hydrogen peroxide (H202) are examples. They can be decomposed directly to gases (usually by means of a catalyst). The drawback is that they are not very energetic and tend to be used only for small control jets.

The most common rocket fuels are:

• hydrocarbons, referred to generically as ‘kerosene’ (some early British documents refer to ‘kerosine’), usually as some form of jet fuel.

• hydrazine or some related compound (usually UDMH – Unsymmetrical DiMethyl Hydrazine or (CH3)2N. NH2).

• liquid hydrogen.

Kerosene is cheap, easy to handle, not volatile and not poisonous. Hydrazine is easily storable, and it is mostly used in combination with dinitrogen tetroxide, N204. Both produce highly poisonous fumes, and dinitrogen tetroxide is also very corrosive. They ignite spontaneously on contact (i. e. they are hypergolic). The combination is often used in missiles which are left fuelled up on a long-term basis, or in upper stages of satellite launchers, particularly when a restart capability is needed.

Liquid hydrogen is the most energetic and effective fuel, although it suffers from two major drawbacks: it boils at -253 °C or 20 K, and has an extremely low density of 71 kg/m3 compared with 1,000 kg/m3 for water. Low density implies large tank volume and, as a consequence, extra weight.

Kerosene was the usual fuel of choice in the UK, with either liquid oxygen or HTP as the oxidants. Although a good deal of research and development was done on liquid hydrogen, including test firing of liquid hydrogen chambers, sadly no rocket stages were built using liquid hydrogen.

Common oxidants are liquid oxygen, and as mentioned, dinitrogen tetroxide in combination with hydrazine. However, Britain was to make extensive use of another oxidant, hydrogen peroxide (H2O2), and the way it was used was and still is unique. Hydrogen peroxide was used in the form of High Test Peroxide or HTP, a solution with 85% of hydrogen peroxide and 15% water. Hydrogen peroxide can be decomposed to steam and oxygen at a high temperature using a catalyst – nickel gauze plated with silver, the silver being the catalyst. In this way, the HTP could be used as a monopropellant, but it was much more efficient to inject a fuel such as kerosene into the hot gases to be burnt in the oxygen produced in the decomposition. HTP was also thought to be safer and easier to handle than liquid oxygen. In 1952, the decision was taken to use only HTP motors for all liquid propellant rockets used on, or in, aircraft1.

The story of Blue Streak divides into two phases, phases which are very sharply divided from each other: the military and the civil. The civil phase was an afterthought, a by-product from the military. Blue Streak was cancelled as a military weapon in 1960, and its life as a civil project began with the intention of creating a satellite launcher from what had been intended as a Medium Range Ballistic Missile (MRBM). But after 14 years and hundreds of millions of pounds of expenditure (much to the despair of the Treasury) neither programme yielded useful results – but that was not the rocket’s fault. Technically, the design was excellent. Almost every launch was flawless. But it spent most of its life in search of a role.

The original intent behind Blue Streak was to produce a guided weapon capable of carrying a megaton range warhead to the strategically important parts of the USSR. Design work began in 1955 and the final result was a technological snapshot of rocketry progress circa 1957. In principle and design it was very close to its American and Russian counterparts, and very much their equivalent. But to realise this, we have to look briefly at the history of guided weapons.

The V2 was notoriously inaccurate, and given in addition its limited payload (1 tonne of high explosive), it was not an effective military weapon. Following the war, both the Americans and the Russians pressed on with improved designs, based around the V2 concept. The British devoted relatively little effort to large rockets at this stage, and such work was, in the main, theoretical, although three captured V2s were fired off in Cuxhaven, Germany (Operation Backfire) in what was effectively a familiarisation exercise. However, the post-war rocketry effort in the three countries began to solve some of the three major problems of guidance, accuracy and range.

Most of the work done in the UK in the early 1950s simply consisted of studies of possibilities. The technologies of the time were changing fast, and the problems were firstly to choose which would be the most fruitful, and secondly, to try and estimate how far the technologies could be usefully developed. One of the first significant British developments in this field of long-range delivery
systems was a report commissioned from the English Electric Company Ltd.1 Work on the report, entitled ‘Long Range Project’, by LH Bedford, started in March 1952, and the completed report was delivered in July 1953. The first consideration was that of range and accuracy. The report took a range for the weapon of 2,000 nautical miles with circular error probability (c. e.p.) of the order of 1,500 ft as the target to be aimed for (c. e.p. refers to the probability of 50% of the missiles landing that distance from the aiming point). Three types of missiles were considered: the ramjet, the glide rocket and the ballistic rocket. The guidance system for all of these was taken to be integrating accelerometers using gyroscopes. The times of flight were calculated as 16 minutes for the ballistic rocket, 25 minutes for the glide rocket and 50 minutes for the ramjet. The significance of this was that the accuracy of the system decreased as time of flight increased. Thus the ballistic rocket was to be preferred on two counts: that of accuracy and that of invulnerability. Intercepting a warhead from a ballistic missile is a task that even today is extremely difficult. Indeed, if attempted operationally on a system with even rudimentary decoys, it is well-nigh impossible.

The two major problems of the ballistic rocket were identified firstly as obtaining a sufficiently high S. I. from the rocket motors, and secondly the problems of re-entry into the atmosphere. In neither case were practical solutions offered, nor was there any attempt to suggest design features such as the fuel to be used. The report was still theoretical and speculative.

The RAE was conducting its own studies into the same areas as the English Electric Report, and it is interesting to note the estimated all-up weights of the three options2:

(Range is given in nautical miles; weights in thousands of pounds)

This has important implications for the design of any ballistic missile: a mass of 210,000 lb implies a lift-off thrust of at least 250,000 lb. It was noted that the ballistic missile would be much heavier than the others, and that if it were to be chosen it would be because of its much greater chance of survival against enemy defences. The calculations were done assuming liquid oxygen and kerosene as propellants, and give a remarkably accurate prediction for the weight of what would become Blue Streak.

As a consequence of these deliberations, the RPD at Westcott pressed ahead with design studies on larger motors. But even at the end of 1954 no formal summary had been made of the RPD’s overall policy on the ballistic missile, as it was felt the position was constantly changing. At the same time, research was continued on a series of rocket engines that went under the generic name of Delta. Despite RPD’s earlier dislike of kerosene as a rocket fuel, these were lox/kerosene fuelled, and mainly for research purposes. There was no firm design for a missile at this stage, although speculative drawings of how to fit several motors together for such a missile were made.

Commercial firms were also interested in the concept: during a meeting between the RAE, RPD and Rolls Royce, the company stated that:

In their own studies they had assumed a warhead of 10,000 lb and minimum range of 2,500 miles and had produced a preliminary design. This design was a single stage missile with an all-up weight of 250,000 lb and empty weight 18,000 lb giving a mass ratio (empty/all up) of 0.072. Thirty-three chambers of 10,000 lb thrust each were used.

Apart from the number of chambers, again this sounds very much like Blue Streak.

At around this time the ramjet and the glide rocket drop out of consideration. The glide rocket was never a very serious candidate. The ballistic missile with separating warhead and self-contained guidance system has the great advantage that it was, and still is, almost invulnerable to defensive counter measures. A missile is also much better equipped to carry decoys; in other words, dummy re­entry vehicles or devices that would look the same as a re-entry vehicle to enemy radar. Decoys have been an on-going area of research up to the present day.

The ramjet is not as vulnerable to guided missiles as the manned aircraft, but does not begin to compare with a free falling re-entry vehicle at velocities of several thousand ft per second. Height is also a factor here: today’s turbofan subsonic cruise missile is designed to fly as low as possible since terrain following radar and accurate guidance have subsequently been developed to make this possible. Supersonic ramjets would be high flying and more vulnerable to defensive missiles.

In 1954 the Sandys/Wilson agreement was signed between the UK and the US, whereby the two countries agreed to collaborate on long range missiles; the British concentrating on medium range weapons whilst the Americans would aim for intercontinental ranges. However, to produce an effective military weapon, there were several important problems to be solved other than simply building a big enough rocket. For the missile to fulfil its function, all the systems had to work together. Loss of just one would render the weapon impotent.

The first of these problems was that of guidance. Radio/radar guidance during the launch phase was possible. However, such external guidance could easily be jammed or destroyed, particularly during a nuclear attack. The answer lay in internal inertial guidance, using gyroscopes and accelerometers to determine the vehicle’s heading and speed accurately. The American Atlas missile used a form of radio guidance, but all other missiles carried inertial guidance. A form of radio guidance for Blue Streak was also developed for a time before being abandoned as too easy to jam and too easy to destroy, and also because there was an economy drive on! There were many obstacles to an accurate inertial guidance system in the 1950s, before the advent of transistors and when electronics depended on power-hungry thermionic valves for amplifiers. Suitable gyroscopes were difficult to manufacture, and eventually, partway through the project, gyros had to be bought from the American firm Kearfott. To give some idea of the accuracy which was needed over a range of 2,500 nautical miles, it was stated early in the programme that there was

a requirement for a 50% circular error no greater than 8,000 feet at all ranges. If this requirement should result in undue delay in the introduction of the missile into service the Air Ministry will be prepared to accept a 50% circular error of no greater than 3 miles at all ranges in the first instance.3 [8,000 ft is around one and a half miles.]

A novel feature of these designs for ballistic missiles was that at the moment the engines cut, some two to three minutes after launch, the warhead and its re­entry vehicle would separate from the empty rocket shell and travel along a ballistic path outside the atmosphere towards its target. After a flight time of some tens of minutes, the re-entry vehicle would descend on its target at very high speed – perhaps as much as 15,000 miles per hour. It had to re-enter the atmosphere at this speed, which led to the other unknown of the time: what would happen to such a vehicle? Would it survive re-entry or would it burn up like a meteor? In parallel with Blue Streak, the Black Knight programme was set up to investigate the problem. Guidance and re-entry were the two major imponderables, for which a good deal of work had to be done in parallel to the main project. But what of the rocket itself?

After the Sandys/Wilson agreement had been signed, the US and the UK set out to design missiles which were complementary to each other. Initially, the Americans were to produce the long-range Atlas missile, the British the medium- range Blue Streak. A team of Americans visited the UK in April 1955 to discuss progress. Sir Steuart Mitchell (CGWL) described the British plans, which involved the RAE as the principal designer for the first two years, control being passed to the firms in the second year. The American team was not impressed by this idea. The VCAS (Vice Chief of Air Staff) noted that he had been told in private that

They felt themselves that unless we give it to industry with a free hand it might delay the project greatly. They voiced the opinion at the meeting that the British Technical Civil Service was of a much higher calibre than the American, but that a scheme such as that proposed by Mitchell would just never work in the US.

Whether this was the case is difficult to judge, but certainly, progress in 1956 seems to have been slow. On the other hand, uncertainties as to the warhead, as we shall see, contributed to the delays.

It is also noticeable that the many technical reports that came out of the RAE at this time were also speculative and academic. Typically, a half dozen different design solutions would be carefully evaluated in these reports, but they did not lead to a direct practical design in the way that an aircraft design team might work. British aircraft designers of the time would start with quite detailed sketches, which would be refined up to the final solution. A commercial firm was also under pressure to produce a prototype as soon as possible in a way that the RAE was not.

At the same time, a British team from RAE had visited America, and produced a report defining the problems more clearly. As a result of this, the Air Staff felt sufficiently confident as to issue an Operational Requirement (OR 1139) for the missile in 1955, which stated a requirement to deliver a megaton range warhead over a distance of up to 2,500 miles. An OR is one thing, a design is another. Throughout 1955 and 1956, whilst work started on Black Knight and on other aspects of the programme, arguments went back and forward as to the details of the design. The crucial point, from which all else flowed, was: should it have one motor or two? The motor under consideration, an American design, had a thrust of 135,000 lb. This implied a missile weight of no more than 100,000 lb with only one motor. A two motor design could be double that mass. The critical factor, and an unknown factor, was the payload, and the payload was, of course, a megaton warhead and its re-entry vehicle.

With only one motor and a warhead weight of 2,000 lb, the maximum range that could be expected was only 1,900 miles – not enough. There was a further snag: Britain did not have a thermonuclear warhead weighing only 2,000 lb. Indeed, Britain did not have a thermonuclear warhead at all – in 1955, the design of such a warhead was only just beginning. It would not be until late in 1957 that such a device would be tested successfully. The only warhead that might have done the job weighed 4,500 lb – far too much. Some lateral thinking would be needed.

But in parallel with this crisis, another was developing; this time within the British Government. ELDO had been set up by the Conservative Government under Macmillan, and Douglas Home, Macmillan’s successor, was not in office long enough to bring about any major policy changes. The new Labour Government under Harold Wilson took a very different view of the organisation, aided by the Civil Service, who had always been opposed to ELDO, and saw their chance to cancel it. The Treasury memo on space to the new Chancellor, Jim Callaghan, in 1964 is an interesting read (it is reproduced in its entirety in Appendix A)16.

Part of Wilson’s rhetoric at the 1964 General Election had revolved around the idea that the Conservative Government had been out of date and out of touch, as opposed to a more dynamic Labour Party. The phrase ‘the white heat of the technological revolution’ is attributed to him after his speech at the Labour Party Conference at Scarborough in October 1963. Like many such catch phrases, he did not say it quite in this form; it has been slightly paraphrased. (His actual words were ‘In all our plans for the future, we are re-defining and we are re­stating our Socialism in terms of the scientific revolution. But that revolution cannot become a reality unless we are prepared to make far-reaching changes in economic and social attitudes which permeate our whole system of society. The Britain that is going to be forged in the white heat of this revolution will be no place for restrictive practices or for outdated methods on either side of industry.’)

Wilson felt that the Conservatives had committed themselves to some extremely expensive technological programmes such as Concorde, TSR 2, ELDO, and so on, and that the scientists, engineers and technicians involved should instead be working in private industry, helping to produce up-to-date goods for both the domestic and export markets. A number of aviation projects were cancelled in 1965, but Concorde and ELDO proved to be more difficult – they were international projects, and the Government had signed treaties which were hard to break. If the British Government were to cancel the projects, then they would be repudiating the treaties and be liable for damages – and the cost of the damages might well soak up any saving (although it is probable that the Government ended up spending far more on both Concorde and ELDO than it would have paid in damages as a result of cancellation in 1964).

Having discovered that pulling out of ELDO might be more trouble than it was worth, the British began employing other tactics. One was a demand for a reduction in its share of the budget. The argument being used here was that other countries were benefiting from developing new technologies, whereas developing Blue Streak was fairly routine work and nothing new was being learned.

Another tactic was to become excessively legalistic as to the nature of the work being carried out – whether it was part of the ‘original programme’ or not. The British Government had signed up to the programme as agreed in the original convention, and nothing else. Any change to the programme – for example, the perigee/apogee system – could then be opposed on the basis that it was not in the original agreement. These problems became more acute as costs rose, and new budgets had to be negotiated. Finally, the British Government effectively withdrew on the basis that it was interested in developing the technology that went into the satellites rather than the launchers. This withdrawal was de facto rather than de jure, as we shall see.

An example of the British attitude can be seen in a memo concerning the French and ELDO B:

If ministers accept the Chief Secretary’s view that the UK should not participate in the ELDO programme as proposed by the Minister of Aviation, it will be important to handle this in such a way as to minimise political repercussions. I do not doubt that if the UK delegate were to stand up at the beginning of the conference and announce crudely that the UK is to withdraw from the organisation, there would be an unfortunate reaction among other members. But as stated earlier, the French have themselves called the whole future of the Organisation into question by insisting that its programme should be radically recast and that until this is done the French financial contribution will be restricted. It ought to be possible to take advantage of this to throw most of the onus for the collapse of the organisation on to the French. One need not say in terms that the UK regards ELDO as undesirable. All that would be necessary to say, as I see it would be that the UK are not prepared to depart from the concept of ELDO A as originally conceived and that they are not even willing to proceed to completion of this programme until it has been more adequately costed. As for ELDO B they could not begin to consider a commitment in principle on the basis of the inadequate information about the cost, technical validity and economic prospects of the project so far available. This, one hopes, should suffice to bring about the demise of ELDO.17

Such behaviour was also guaranteed to irritate Britain’s partners. It was Britain, after all, that had worked so hard persuading these countries to join ELDO, and now, halfway through the programme, it was Britain that was working to destroy the organisation. There is an interesting letter on the subject in the ELDO archives:

It is unrealistic and wasteful to attack either the British decision of April 1968 not to contribute to the ELDO overrun and not to participate in post 1971 rocket development, and the decision of the Four [that is, the four nations remaining in ELDO: France, Germany, the Netherlands and Belgium] to make sure that Europe possesses rockets for putting into orbit both near and geostationary satellites. What is at issue is purely the British contributions for 1969, 1970 and 1971 of a total value of about £M17.

In April, Mr. Wedgwood Benn announced the decision mentioned above, but stated that of course the UK would carry out its commitments as agreed in 1966 and earlier, evidently referring to these £M17. It seems, however, that the UK expected the immediate collapse of ELDO following the British announcement with dissolution liabilities, the British share of which could at most come to £M10 after 1968. This expectation may also have been partly responsible for the hesitations expressed about the supply of Blue Streak.

By the time of the Bonn Conference it had become clear that the Four wished ELDO to continue. This led on the one hand to British assurances on the supply of Blue Streak which were accepted by the others, and to the proposal made by Wedgwood Benn at Bonn that if the British liability to ELDO was reduced (the figure of £M17 was not mentioned then, but subsequently, especially at the ELDO Council on 29 November) the UK would put that much and more into application satellites, reversing the UK decision of April on this issue. Although the UK was helpful at Bonn on several issues (use of launchers, unifications), acceptance of this protocol was made a necessary condition for lifting the reservation the UK had put on this and several other points.

In fact the British proposal was never seriously considered because the others

(i) saw no sense in an applications programme without a launcher;

(ii) if the UK switched resources from the technically uninteresting production of

Blue Streak to application satellites, it would benefit her and no-one else;

(iii) the others were not in a hurry on applications;

(iv) they thought the UK was keen on applications anyway.

In these circumstances, the UK, on December 18, 1968, in a letter to the Ministers, released herself unilaterally from the commitment by regarding ELDO’s austerity plan T9 as different from what agreed in 1966. This pretext, although possibly justified on the narrowest legal basis, shocked the others by its patent conflict with earlier British statements. They fear the effect of this unilateralism as a precedent and certainly are asking whether such legal devices could be used equally in any other technologically risky long-term programme. The very basis of European technological co-operation has been undermined by this step through its fundamental shaking of confidence. The UK’s fitness as partner for any future enterprise is now being questioned even by her closest friends. Note that in this painful development there has never been any advice on the £M10 first presumably evaluated in April and now offered as a present, as no commitment is now said to exist.

All European technological co-operation in space, and possibly elsewhere, will be ruined by this destruction of trust. The severity of the step does not seen to have been understood in the UK, and is of course totally divorced from the merits or otherwise of ELDO.18

And even as ELDO was falling apart, the French Government was still pressing Britain on its participation, to which a memo from within the Department of Trade and Industry commented that:

The fact remains that there is little to be gained by the ELDO Secretariat or by the other ELDO members from making a fuss to keep us in the organisation. Legally we can argue the toss. Politically we can point up the logic of our position. And financially the organisation will be no worse off by our departure.19

In other words, the Government had washed its hands of the organisation, and there was very little in practical terms that the other countries could do. ELDO was finally wound up in 1972, and the British Government has never participated in any part of the Ariane project that followed.

Those in the ELDO Secretariat were well aware of its weaknesses, but had their hands tied. An exposition of the situation was given to the Royal Aeronautical Society in February 1968 by Dr Iserland of ELDO:

The difference between the technological task of ELDO and a political, economic or scientific task of other organisations, showed up from the start: time is a prime factor in technological achievements and, in particular, in space missiles.

When the Convention was signed in 1962, it was decided, therefore, not to wait until its ratification by the Governments, which took place only in 1964. To enable work to be started immediately, a Preparatory group was instituted as a part-time body with the responsibility of specifying and co-ordinating the work and preparing for the functioning of the Organisation on entry into force of the Convention. During this period, each member country started the work under its own authority and at its own financial risk by placing the contracts. To avoid discontinuity, the Convention also stipulated that after ratification, the authority for the contracts would remain with the Governments for the Initial Programme and that direct contracts between ELDO and the firms would necessitate the consent of the member state.

Paradoxically, this laudable desire for speed to start the work, characteristic of the technical nature of the enterprise, resulted, after 1964, in a factor slowing down unnecessarily the speed of progress. Since ELDO did not place the contracts itself, it was not vested in the authority of the ‘overlord’ which is essential in carrying out efficiently an industrial programme.

Strictly speaking, with the kind of organisation imposed for the Initial Programme, the executive lines for co-ordination and management of any part of the development programme of the Europa I launcher were as follows: if the central technical group in the Paris headquarters, known as the Secretariat, found it necessary to define or to specify some technical requirement, it would have to approach the appropriate ministry of the country in which the equipment was built: if this ministry accepted the need for it, it would pass the recommendation to the establishment which was entrusted with the supervision of the national work on behalf of the Government – in the UK this would have been Farnborough. This establishment would then specify the technical requirements to one or two different firms.

This already long process of imposing in ‘open-loop’ an already chosen solution is still relatively straightforward, compared with the process of agreeing on a technical solution where information had to go up and down this long ladder several times simultaneously in one or two different countries, first to find a technical solution and then to implement it. Needless to say, this strict formal line could not always be followed and technical features often had to be by ELDO representatives with some representatives from specialised establishments or industrial firms. However, a pragmatic practice which does not follow the agreed formal lines of control and financial authority can obviously lead to confusion at the risk of offsetting thereby, the advantage of the direct approach. The alternative, to avoid too long information lines, was to agree on a solution in meetings or Working Groups. Since ELDO had no authority to arbitrate a solution (not being the ‘overlord’), a kind of unanimity rule had to be followed, which consisted of convincing the representatives of each country and firm of the correctness of the suggested decision or to find a compromise, which was not necessarily technically optimum. There then still remained the long channel for implementation through the various steps mentioned before.

It will easily be imagined what difficulties are encountered in co-ordinating by such means, for example, the definition of a common electrical circuitry throughout the three-stage launcher.

In some instances, the frightening complexity of this type of co-ordination had a direct influence on the choice of some technical solutions. Here is one example: When it had to be decided whether a central sequencer for all flight events should be adopted for the complete vehicle or else individual sequencers for each stage, relaying each other after exchange of signals at the cut-off of one stage to initiate the start of the next one, it was judged that only the solution with individual stage sequencers had any chance of practical achievement, the central sequencer being outside the possibilities of such a remote co-ordination set-up in view of the numerous events, intimately related to details of each stage, which it would have to control. Without judging which solution is superior on strictly technical grounds, it can certainly be stated that the partial failures in our last two launches have some relation to that choice insofar as the light-up of the second stage did not occur in both cases because of incorrect functioning of the second stage sequencer, while the first stage operated with its own sequencer. Perhaps with a central system, we might either not have launched at all or else had correct sequences throughout the two-stage flight…

The first critical period developed when ELDO presented the budget for 1965. The new estimate of cost to completion of the Initial Programme was for approximately 400 million MU [MU = Monetary Unit, effectively equivalent to 1 US dollar] i. e., twice the original amount estimated in 1961 before the creation of ELDO. Consultations between the member countries became necessary according to the Convention. They took place early in 1965. France suggested to stop the development of the Europa I launcher and to proceed directly to the development of a more advanced and more powerful launcher with upper stages based on liquid hydrogen/oxygen.

The critical period lasted for about three months, during which an extensive study of the French proposal was made, before it was decided to continue the development of Europa I. The effect of this period can still be felt, as it slowed down the work and resulted in delays; delays which amounted to considerably more than the period of uncertainty itself. For the consultations of 1965, ELDO had prepared proposals for follow-up programmes after the Initial Programme. Decisions on these later programmes were, however, postponed by the member countries until 1966. This fact did not help to speed up the work on the Initial Programme after the crisis had been resolved.

Consultations between member countries resumed in 1966, but this time at ministerial level. It was now the turn of British Government to express doubts about the technical and economic validity of the Europa I launcher and to be concerned about the increasing costs. A second critical period began, and it took three sessions of the Ministerial Conference from April to July 1966 to resolve the crisis.

The comments about the flight sequencers (electronic systems that produce the signals to initiate events during flight) are interesting: ‘only the solution with individual stage sequencers had any chance of practical achievement’. Certainly the failures of F5 through to F8 can be put down to exactly that cause: the flight sequencers sending the wrong command at the wrong time, which might not have happened had there been one sequencer for the complete vehicle. It is a considerable indictment of the organisation that it was forced to adopt an engineering compromise which could well have led to the loss of five consecutive launches.

The attitude persisted as far down as the individual launch teams. Alan Bond (later to be designer of the UK spaceplane HOTOL) was the Rolls Royce performance engineer sent from England to monitor the engine performance on the F8 round, and has this to say about his experiences:

The Rolls Royce team at Woomera was under the very capable management of John Bowles. The insular nature of the various teams was striking from the start, not only internationally but also between the vehicle and propulsion teams from the UK.

I am not implying any animosity, there certainly was not any. In fact there was a palpable sense of doing something very important which everyone was very proud of. But there were cultural barriers to communication, except through the regular management channels. In the whole four months of the campaign, the conversations I had with members from the French, German and Italian teams could be counted on the fingers of one hand.

This was in complete contrast to the experience I had seven years later as part of the JET fusion research project where the integration of the international teams was very close. JET went on to be a world beating success and a demonstration of what collaboration can achieve.20

But there were other failures in ELDO, within the organisation itself. ELDO was very much a political construct, designed to cope with all the wheeling and dealing that went on in a multinational organisation such as this. The failure lay on the technical side.

Each country provided its own part of the vehicle, and acted independently. Thus the British set up Blue Streak as the first stage, and then the French would come along and add their stage on top, then the Germans would come with their stage, and finally the Italians would fit the payload and payload shrouds. There was no one in overall technical command. The Secretariat could only make recommendations to member states, with exhortations such as these:

Following the F7 trial [F7 being the seventh flight], the Secretariat tried to inculcate a greater awareness of the need for better technical discipline and control of operations during a trial. Meetings and discussions took place with Member States on the subject of inspection and defect reporting in particular. During the F8 trial, some improvement was obvious, but it is still apparent that these disciplines are not accepted as having the importance attached to them which the Secretariat would

wish. The supply and control of spares was also still far from satisfactory in the

21

upper stage areas.

Despite the exhortations, matters did not improve, as the report on the failure of the eleventh launch, F11, shows:

Two main points provide the basis for the failure of the project.

– the poor organisation of the management system as a whole;

– the technical difficulties of the third stage and its equipment.

The management system established since the beginnings of the Organisation has proved its ineffectiveness.

There exists a certain confusion about the respective roles of the national agencies, the Secretariat, and industry. With regard to the internal structure of the Secretariat, levels of authority are not sufficiently clear. Some firms are badly organised and have not shown a sense of responsibility. Finally, political problems have too often taken precedence over the technical problems and cost-effectiveness of the project.

In these conditions, the Secretariat was unable to play its proper piloting role, which resulted in an unflightworthy launcher and the abnormally high cost of the programme.

Without going into detail, the main technical problems lie in the third stage. Its design is complicated and its wiring needs to be thoroughly revised. Its integration has been particularly deficient. Three major systems in this stage have net been qualified: the sequencer, the middle skirt separation system, and the guidance computer. The latter, moreover, which is a prototype product, is not flightworthy.

To guarantee an adequate level of reliability, it is necessary:

– to achieve by appropriate tests the integration of all the on-board electrical systems of the third stage and to demonstrate their electromagnetic compatibility;

– to reorganise the Secretariat in order to transform it into an efficient management tool and provide it with unquestionable technical competence, so that it may play its proper role in discussions with industry.

– to rationalise the Secretariat industrial arrangements to enable a satisfactory solution of the interface and integration problems.22

F11 had been launched in November 1971. Ten years after the initial Anglo – French proposals, after eleven launches and literally hundreds of millions of pounds, the vehicle was still not, in the words of the report, flightworthy. Even so, ELDO still hoped to continue with Europa:

Following the failure of F11, the ELDO Council set up a EUROPA II Project Review Commission on 18th November 1971.

This Commission’s terms of reference were to propose corrections to the programme from both the technical and organisational points of view and to indicate the consequences of these corrections for future launchings.

The aims that the Commission sought to achieve were the following:

– to determine the technical, administrative and financial conditions for ensuring a substantial probability of success for the next EUROPA II launch within reasonable time limits, or to conclude that this is not possible;

– to propose a fresh target plan for launchers, launches and payloads from F12 to F16 inclusive.23

But the Germans failed to make much progress on the redesign of the third stage. The launch of F12 was put back until October 1973 (the F12 Blue Streak
arrived at Kourou in April), but it soon became apparent that ELDO was going nowhere, and in May 1972, the F12 launch was cancelled, Europa II abandoned, and ELDO was wound up at the end of the month. [9] [10]

Single stage. Launched 1 May 1962 at 22:43. Apogee 494 miles.

BK15 was a re-entry physics experiment but limited by the availability of ground instrumentation on the range at the time, i. e. the ‘Gaslight’ project equipment and not the more sophisticated ‘Dazzle’ project equipment.

A single-stage vehicle was fitted with a separating uninstrumented 36-inch diameter copper sphere (the first pure metal head used). The object was to achieve re-entry of the sphere in advance of and well separated from the main body, to provide spatial resolution for ground instruments. This was to be done by turning the vehicle over in the yaw plane after engine burn-out, then separating and pushing the head vertically downwards away from the body when it had turned through 180o.

A sabot containing thrust units was used to push the head away; the sabot itself was to have remained attached to the body by a lanyard. Subsidiary upper atmosphere experiments were also carried out and further data obtained on Gamma 201 engine performance and propellant usage. It was also intended to test for the first time an ‘automatic pilot’ in the ground guidance system. A head re-entry velocity of 11,600 ft/second was achieved at 200,000 ft.

The vehicle turnover and head separation devices worked, but the timing of the latter was incorrect; the head was separated before the vehicle had turned through 180o. The lanyard failed to hold the sabot to the body and the sabot therefore accompanied the head. The re-entry of the head was not recorded by any ground instrument nor was it seen by any observer.

This in itself is a significant result since it confirms the prediction that, because of the absence of ablation products and other contaminants in its wake, the re-entry into the atmosphere of a pure copper head should be a target difficult to detect by optical means. The sphere was recovered and, as expected, there was no heat discolouration of the surface; the maximum surface temperature did not exceed 350 °C during re-entry.

Governments tend to make the announcements of the cancellation of a project as brief as possible. The Opposition and the Press will not follow up the cancellation of a project such as Black Arrow unless there is the whiff of a scandal. The Press was not interested; and in this case there was very little that the Opposition could use to attack the Government.

EXPERIMENTAL SURFACE FINISHES

EXPERIMENTAL SOLAR CELLS

POWER SYSTEM ELECTRONICS

ASPECT SENSORS

BATTERY

One group of people that is rarely informed of the true reasons for the cancellation are those who work on the projects, and whose livelihood depends on them. Not surprisingly, urban legends or conspiracy theories begin to emerge. The cancellation of Black Arrow was no exception.

Engineers are usually conservative by nature, and often Conservative by political inclination. One of the ‘bogey men’ of the time was Tony Benn (known earlier in his career as Anthony Wedgwood Benn, but who had now adopted a more demotic name), and to those who worked on the project, part of the mythology was that it was cancelled by Benn and the socialists, when it was actually cancelled by a Tory Government!

In reality, virtually all the opposition came from the Treasury, as the following memo from February 1969 illustrates:

I have no doubt that the Cabinet will give overwhelming approval to the Ministry of Technology’s [Tony Benn] proposals for Black Arrow. At the S. T. meeting on Friday, 21st February, all Ministers from all Departments except the Treasury were not only in favour of the proposals, but emphatically so. The reservations of D. E.A. officials [Department of Economic Affairs] are not apparently shared by D. E.A. Ministers, including Peter Shore. The least enthusiasm was shown by Sir Solly [Zuckerman, Chief Scientific Adviser to the Government], but he gave qualified support and clearly did not brief the Lord President to oppose.

2. I should in fairness add that Tony Benn put his case very attractively. It clearly has some merit and while I suspect there may be a considerable degree of optimism influencing the supporters of Black Arrow, I doubt if the Treasury arguments however skilfully deployed, will sway other Cabinet members.

3. In the circumstances I would suggest that a last ditch fight by the Treasury against Black Arrow in Cabinet could be mistaken. It might undermine the Treasury’s general position on more hopeful causes. I feel a tactically more rewarding line would be for you and the Chief Secretary to say that having looked at the proposals you feel that there is merit in them (including the proposal for a British launcher) and that you do not propose to object.20

The Ministry of Aviation had been subsumed into the Ministry of Technology in February 1967. It was further reorganised with the advent of the Conservative Government lead by Edward Heath in 1970, becoming part of the new Department of Trade and Industry (DTI). But after all the attacks on Black Arrow by the Treasury, it was actually the Aviation department of the Ministry of Technology which began the process by which Black Arrow would be cancelled. The memo in question is undated, but seems to have been written around October 1970:

As I mentioned the other day, I feel there might be considerable advantage in arranging an impartial examination of the National Space Technology Programme in the light of the recent Black Arrow launch failure [the R2 launch].

It is of the utmost importance that the next firing of Black Arrow, currently scheduled for May 1971, should be successful. We, RAE and Industry are already engaged in analysing the technical causes of the failure, but we have to recognise that there are also wider implications. Another failure, and our national technological competence as well as the future of the National Space Technology Programme would be in question. Examination of the programme as a whole by an outsider of suitable qualifications could be useful in ensuring that it develops from this point on in the best possible way.

The examination would have to take as a starting point an acceptance of our primary objective in space, which is to attain the capability in satellite technology enabling us to offer space hardware, internationally and on an industrial scale. The investigation should in addition not question the broad institutional framework of the Programme-in other words it would be accepted that the effort was a joint Government and Industry one. Within these constraints, however, the investigation should be given the widest possible remit to examine the means we have employed to reach our objective.

The formal terms of reference might be on the following lines:-

To assess the relevance and appropriateness of the Programme, in its present form, to the goal of establishing a significant national competence in satellite technology.

To study in particular the role of the national launcher (Black Arrow) in the programme; the level of effort needed to develop it into a dependable vehicle; and the cost of alternatives to it.

To report on the management of the Programme, with special reference to the launcher element.

And to make recommendations.

I believe that an examination along these lines could be of a very real help to us, especially in providing the answer to two questions — is the level of spend on the Black Arrow launcher programme a sensible one, or ought it to be increased very substantially in order to achieve real gains; and, whatever the level of sensible expenditure on a national launcher programme might be, would it be preferable and more economic to use an American launcher?

The difficulty, of course, is to find a man of sufficient managerial and technical qualification within the UK who was not already involved in the space programme. We are already separately engaged in the discussion of suitable names. My present purpose is therefore to seek your approval of the terms of reference set out above, on the basis of which we might approach a suitable candidate.21

The question was who among what have been termed as ‘the great and the good’ would be willing and available, although one stumbling block was the requirement for some technical knowledge. In the event, an impeccably qualified candidate was identified and, on 1 October 1970, accepted the invitation to undertake the inquiry: William Penney.

William Penney is best known for his work on Britain’s atomic weapons, although he had many other scientific accomplishments to his name. He won a scholarship to study at the University of London, winning the Governor’s Prize for Mathematics and graduating with First Class Honours in 1929. In 1944 he joined the British mission to Los Alamos, working on the use of the atomic bomb and its effects. On his return to England, he was put in charge of the British atomic bomb project, and saw the project through to the test of the first bomb in 1952. At this point Penney was offered a Chair at the University of Oxford. Always more inclined toward the academic life, he was keen to accept this post, but he was persuaded that the ‘national interest’ required him to continue as director of the AWRE at Aldermaston until 1959. From 1954 Penney served on the Board of the Atomic Energy Authority, becoming Chairman in 1964. He retired as Chairman in 1967, and then became Rector of Imperial College.

Given these achievements, it was unlikely that his findings would be disputed, and given his expertise in running demanding experimental programmes, he would have seemed to be the ideal man for the job. Being retired from any form of Government research meant he had no axe to grind, and would be widely seen as an impartial observer.

A briefing note for the Minister after Penney had submitted his report noted that:

Lord Penney’s approach to his inquiry was informal. By meeting the people in industry and government concerned with Black Arrow, and discussing the project with them, he aimed to make personal assessment of the management of the programme at the same time as briefing himself on the details of the project. He made two visits to industry, to see the major Black Arrow contractors – British Hovercraft Corporation on the Isle of Wight, and Rolls-Royce at Ansty, Coventry. He visited RAE Farnborough on two occasions, and had a number of discussions with the staff of space division and other headquarters divisions with an interest in Black Arrow. For details of the alternative launchers to Black Arrow he relied on information supplied by the department: he made no visits abroad in the course of the inquiry.

As might be expected, the report was thorough and comprehensive, stretching to 24 pages and 68 sections. He fulfilled his brief admirably, looking at Black Arrow and its alternatives, then considering the viability of Black Arrow within the larger framework of British space policy. His conclusions and recommendations are worth quoting:

My conclusions are as follows:

The disappointing performance of Black Arrow launcher R2 in September 1970 was not due to poor project management, bad fundamental design, or low grade effort. We know we were taking a gamble in trying to make do with so few test launches, and the gamble went against us.

The cost of launching of the X3 satellite on the R3 vehicle is almost fully incurred, and the best policy would therefore be to launch X3 in July 1971 as planned. But in spite of all the work being done to follow up the R2 failure, we cannot be sure that the gamble will not go against us again on R3. The Ministry has neither the time nor the resources to build up greater confidence in Black Arrow before X3 is ready for launch.

It is probable that with the present launch rate of one Black Arrow a year, we will still not be fully confident of its reliability by 1974 when we are planning to launch X4, the second major technological satellite. Even if the Ministry agreed to fund an increase in the launch rate, only one or two extra Black Arrows could be built and launched by 1974.

There is a three-year gap between X3 and X4, but Black Arrows are being built at the rate of one a year. This mismatch between the production rates of launchers and worthwhile satellites may well continue beyond X4, and cannot easily be remedied by adjustments to the launcher programme which is already running at about the minimum level for efficiency…

The current programme gives us too few Black Arrows to establish the vehicle as a proven launcher in a reasonable timescale, and too many to meet our requirements for satellite launches. It is therefore not a viable programme at present, and there is no easy way out of the dilemma.

And on the subject of alternative launchers, he notes:

Black Arrow has no alternative use, and the nation would have much to gain and little to lose if it were cancelled in favour of American launchers. We would be abandoning a certain political independence and a guarantee of commercial security payments, but on these two points satisfactory safeguards should be available from the US authorities.

Unless a formal approach is made quickly to the inhabitants on the availability of Scouts and other launchers for our technological satellite programme, further commitments will have to be made on Black Arrow vehicles as an insurance move.

As soon as we are satisfied that we can get the launchers we need from the Americans on acceptable terms, the Black Arrow programme be brought to a close as soon as possible. However, the launching of X3 on the R3 vehicle should proceed, and there may be a need for a further launch if problems arise with X3/R3.

I therefore recommend that:

The Ministry should make a formal approach to the US authorities as soon as possible about the availability of launchers for X4 and subsequent satellites in the National Space Technology Programme, and terms on which they can be provided.

Commitments on R5 and subsequent Black Arrow vehicles should be kept the minimum possible level while the Americans are being approached, and all work on them should be stopped as soon as satisfactory arrangements have been made for the supply of US launchers.

The X3 satellite should be launched as planned on the R3 Black Arrow vehicle in July 1971; the R4 vehicle should be completed in all major respects and used as a reserve for R3 up to the launch.

If X3 goes into orbit successfully and functions as planned, the Black Arrow launcher programme should be brought to a close without further launches.

If X3 fails to go into orbit successfully or fails to work in orbit, the Ministry will have to decide whether to bring the launcher programme to a close at that point or repeat the X3 experiments by launching the X3R on the R4 vehicle. Unless they are sure that the R4 vehicle has a better chance of success than the R3, and it is worth spending кШ million to repeat the satellite experiment, a further launch should not be sanctioned.

The X4 satellite should be launched on Scout; and Scout or Thor Deltas should be bought as necessary for later satellites in the series.

The Ministry should determine at a high level the views of British industry on the value of a technological satellite programme. If no such value can be identified the programme should be brought to a stop. If it is established that the programme is worthwhile, a plan should be drawn up for a series of future satellites so organised as to give the maximum benefit to British firms in their attempts to win contracts in the international market.22

It is difficult to argue with his conclusions, or, indeed, with his recommendations. As he correctly points out, there was a ‘mismatch between the

production rates of launchers and worthwhile satellites’. Making fewer launchers was not economic; there were not the resources to make more satellites.

The report was submitted to the Minister in January 1971, and made its way up the government hierarchy, culminating in a meeting held in the Prime Minister’s room at the House of Commons at 5:15 pm on Monday 6th July, 1971.

Those present were the Prime Minister (Edward Heath), the Chancellor of the Duchy of Lancaster (Geoffrey Rippon), the Lord Privy Seal (Earl Jellicoe), the Secretary of State for Trade and Industry (John Davies), the Minister for Aerospace (Frederick Corfield), the Chief Secretary to the Treasury (Maurice Macmillan), and Sir Alan Cottrell, Chief Scientific Adviser. An excerpt from the minutes of the meeting reads:

The Lord Privy Seal recalled that on 24 May the Ministerial Committee on Science and Technology had approved the proposals by the Minister of Aerospace that the Black Arrow programme should be stopped, that we should support the full development of the X4 satellite and that for the launching of small satellites we should in the future rely on the American Scout launcher. The Prime Minister had been doubtful about the impact of this decision on future European collaboration in science and technology, particularly as the French were developing their own launcher the Diamant. Since then however the political difficulties have largely dissolved. The Diamant programme had now been deferred and the French were themselves using the Scout launcher this year.

The Prime Minister and the other Ministers present agreed that the proposals originally approved by the Science and Technology Committee in May should now be implemented. The Chancellor of the Duchy of Lancaster said he did not think that the cancellation of Black Arrow would be deemed inconsistent with anything the government had said when in opposition; there had been no commitment to back any project which was not successful.

The Minister for Aerospace said he thought that the announcement of the decision would not cause great surprise and could be done by an Answer to an arranged Written Question.

The Prime Minister agreed to this and suggested that the announcement should be as late as possible.23

Three weeks later, the following exchange appears in Hansard for 29 July 1970:

National Space Technology Programme

Mr. Onslow asked the Secretary of State for Trade and Industry what progress has been made with the review of the National Space Technology Programme; and if he will make a statement about the future of the Black Arrow Launcher.

Mr. Corfield: The first phase in the review of the National Space Technology Programme has now been completed. Plans to launch the X3 satellite on a Black Arrow vehicle later this year have been confirmed, but it has been decided that the

Black Arrow launcher programme will be terminated once that launch has taken place.

We have come to this decision on Black Arrow mainly because the maintenance of a national programme for launchers of a comparatively limited capability both unduly limits the scope of the National Space Technology Programme and absorbs a disproportionate share of the resources available for that programme.

We hope to complete our review in the early months of 1972. Meanwhile work is continuing in industry on research into basic satellite technology and on the development of the X4 satellite. X4 is planned to be launched in 1974 on a Scout vehicle to be purchased from N. A.S. A.

The curious (or perhaps not so curious) feature of the announcement is how little attention it received. True, Black Arrow always had had a low profile, but neither in Parliament nor in the press was there any great comment. Perhaps the last word should be given to the New Scientist magazine, which had this to say in August 1971:

Despite considerable success with small launchers – notably Skylark – the modern sport of rocketry evidently rouses little excitement in British hearts. The now- promised demise of the Black Arrow programme, the erstwhile Black Knight venture, is unfortunate only because its death throes have been so prolonged. Announcing last week that, after a final launching later this year when it hopefully will put the X 3 satellite into orbit, Mr Frederick Corfield, Minister for Aerospace, said that henceforth Britain’s need to pursue experiments in space technology would be met with US launch vehicles. The reason essentially is that nearly all foreseeable space applications are going to require satellites in high geostationary orbits; Black Arrow falls far short of this requirement, being able to lift some 260 lb only into a near-Earth orbit.

One measure of the effectiveness of a rocket motor or fuel combination is Specific Impulse or S. I. One way to define it is (thrust x burn time)/(total mass of fuel burnt). Another way is the thrust obtained from each lb (or kg) of fuel burned each second.

In modern units, S. I. would be quoted in Ns/kg – which turns out to be dimensionally equivalent to m/s. This is because S. I. can also shown to be the same as the exhaust velocity of the gases from the combustion chamber. Furthermore, the final velocity of a rocket (in the absence of gravity, air resistance and so on) can be shown to be:

vfinai = vexhaust x ln(mass at start/mass at end)

Hence the greater the exhaust velocity, the greater the final velocity of the rocket (ignoring all the complications such as gravity, air resistance and so on).

The difference between the mass at the start and the mass at the end is effectively the mass of fuel (unless anything is jettisoned along the way!). The skill of the designer is to build a vehicle as structurally efficient as possible – all fuel and no structure is not possible, but the structural mass must be as small as possible. Blue Streak had an unusual tank structure, being a lightweight stainless steel ‘balloon’, which needed to be constantly pressurised to keep its structural integrity. Black Knight and Black Arrow were also structurally very efficient.

The equation above only applies in ideal circumstances. The effectiveness of a rocket motor is decreased in the atmosphere, since the thrust from a rocket engine derives from the pressure difference between the pressure inside the combustion chamber and the pressure outside. In a vacuum there is no outside pressure. Another way of looking at this is to say that the exhaust velocity is reduced by the air outside. Thus S. I. is sometimes quoted at sea level and sometimes in vacuum. Vacuum S. I. is typically 10-15% higher than sea level.

The HTP/kerosene combination has a relatively low S. I., around 210-220 at sea level. Oxygen/kerosene gives an S. I. of around 245 at sea level. Hydrogen/oxygen is the most effective combination of all, some motors reaching S. I.s of at least 400. One way of looking at this is to say that there is double the thrust for the same weight of fuel.

The saga of the warhead is a story in itself. The urgency with which it was pursued is slightly puzzling in hindsight since it was not intended to deploy Blue Streak until the mid-1960s. The UK had taken the decision to develop thermonuclear devices (also known as fusion weapons or more popularly, the H bomb) in 1954, and the Atomic Weapons and Research Establishment (AWRE) at Aldermaston did not as yet have a working design. Given all the other development work that needed to be done, a decision on a warhead could have been deferred until a fusion weapon had been developed. There was a degree of risk in this: there was the possibility that no warhead could have been developed within the weight limit of one ton. On the other hand, the Blue Streak design was the largest possible for a single stage vehicle with only two motors. Designing anything larger would have led to a very unwieldy weapon.

What Britain did have was a relatively low yield lightweight fission device – Red Beard – and a design for a much more powerful warhead which incorporated fusion principles, but was not what would now be called a thermonuclear device. This was Green Bamboo – never tested, since it soon became obsolete. The snag was that this device had a weight in the region of 4,500 lb, but in the absence of anything else, it was Green Bamboo which was specified in OR 1142, entitled ‘Warhead for a Medium Range Ballistic Missile’.

Red Beard, the lightweight fission weapon, had been ruled out since its yield was only 10-20 kilotons (kT), and given the predicted accuracy of Blue Streak, this was thought to be inadequate. Green Bamboo was too heavy. Thus William Penney, then Director of Aldermaston, was asked if a lighter warhead of similar yield could be built. He replied to say this might be possible, but that ‘the figures of 1,800 lb weight and 30” diameter quoted for an unboosted fission bomb with a yield of about 1 megaton were purely estimates at this stage and could not be guaranteed.’4 After further study, he decided that ‘on current knowledge I could not guarantee to make a satisfactory warhead within the weight specified’. A weight of around 2,200 lb was more probable, and it would use around twice as much fissile material as Green Bamboo. It would be a pure fission device, but in the absence of any alternative, this warhead, now codenamed Orange Herald, was chosen, and, punctiliously, the wording of the OR was changed from ‘thermonuclear’ to ‘megaton’. (Note: there is some ambiguity here. ‘Megaton range’ meant around a megaton yield, and 600 kT would qualify since 600 kT = 0.6 MT, which can be rounded up to 1 MT.)

Given that the lightest warhead that AWRE could guarantee would weigh 2,200 lb, this decided the issue of one motor or two for Blue Streak: if it was to reach the range required it would need two motors.

A memo concerning Orange Herald sums up the position with some rather interesting comments along the way:

Orange Herald – OR1142

Your loose minute of 31 October asks what is the present status of the official requirement for Orange Herald, and whether the Minister knows of the project. I propose to answer in some detail for I think that it will be useful to record the history of the project.

2. A Draft Operational Requirement No. OR1139 (May 1955) for the Ballistic Missile was discussed at an Air Ministry Operational Requirements Committee meeting on 9th June, 1955. … In discussion of the range of the missile a warhead weight corresponding to Green Bamboo was assumed, and it seemed unlikely that the range which Air Staff desired could be met by a single-motor missile…

4. In the meantime, however, CGWL had been discussing with AWRE the penalties implicated on the missile design by the weight of Green Bamboo, and DAWRE [Director AWRE, William Penney] had said that he could develop a megaton warhead of about half the weight, although requiring more fissile material.

5. This smaller megaton warhead was considered by AWRE to be an important project, and in mid August I was asked by AWRE to arrange for an MOS [Ministry of Supply] code word to be registered for it, for AWRE use and to facilitate inter­departmental discussion. One copy of my minute notifying the choice of a code word for “A megaton warhead for the Medium Range Ballistic Missile” went to PS/Minister [the Minister’s Private Secretary] but, of course, without any description of the warhead

7. In discussion on 14th October, DDAWRE [Deputy Director AWRE] made it clear that AWRE consider it important to go ahead with the lighter warhead, that they are in fact doing so (for the present on their own initiative) and that they are considering the possibility of a trial in 1957. AWRE’s line is thus quite clear …

9. I have also consulted the CGWL side, in the person of DGGW [Director General Guided Weapons]. He tells me that they are not yet in a position to put up the missile requirement OR1139 for the Minister’s approval prior to acceptance: they still consider the project to be in the design study stage, and a meeting will probably be held in December (1955) to make a final assessment. It seems almost certain that a twin-motor design will be agreed, but whether the missile has one or two motors, they will still want the lighter warhead. I pointed out that Orange Herald has at the moment the status of a private venture on the part of AWRE, and that it seemed to me desirable that an OR should be issued to cover it. So far as DGGW is aware, the Minister has not been given any data from the CGWL side on the characteristics of

Orange Herald.

10. Thus the answers to your questions are:

(a) The present status of Orange Herald is that of a private venture by AWRE, for the present Air Staff Requirement for a warhead for the OR1139 missile refers specifically to Green Bamboo. DGGW will inform Air Staff that the missile needs a lighter warhead; this should result in a revised OR calling in effect for Orange Herald, and we can then clear with AWRE the warhead parts of this OR in readiness for the eventual submission of 0R1139/1142 to the Minister by CGWL and CAW [Controller Atomic Warfare].

(b) There is no evidence that the Minister knows anything of the project beyond the code word and its definition.

[Sgd] D. CAMERON DAW Plans. (10th November 1955)

That last line is worth repeating: ‘there is no evidence that the Minister knows anything of the project beyond the code word and its definition’. Decisions involving the expenditure of millions of pounds were authorised not by the politician in charge of the ministry, but by the senior officials running the projects – and Orange Herald probably cost close on ten million pounds (as much as Black Knight or Black Arrow) to design, build and test. Indeed, it is rare that ministers were involved in anything other than the basic decisions. Mention is made of the OR being subject to final ministerial approval. It would be unfair to say that this comprised a ‘rubber stamp’, but on the other hand, how was a professional politician able to judge whether the OR made sense or not? Ministers would take decisions on matters such as whether a ballistic missile was needed, and the rest was up to the permanent officials. Ministers do take the final responsibility – thus when Blue Streak was ultimately cancelled as a weapon, ministerial reputations were at stake. Indeed, it might be said that Duncan Sandys’ defence of Blue Streak while Minister of Defence and Minister of Aviation, even though it was his job to do so, probably hindered his future career. This memo does throw some light on the degree to which decisions involving very large sums of money are taken quite independently of the minister who is nominally in charge – and yet, in almost any system of government, this is the case.

Orange Herald was, in many ways, an extremely unsatisfactory device. It required a very great deal of weapons grade U235 – one Air Ministry paper gives a figure of 120 kilograms, although other figures have been quoted. Whether the UK had the facility to produce 60 such warheads is a very interesting question. Another memo noted that ‘Orange Herald is one of the rounds to be tested at Grapple next year. The cost of the material may be £2% million.’ If those costs were carried through to the final deployment, then the warhead cost would be 60 x 2% = £150 million!

Operation Grapple was a series of tests of atomic devices based at Christmas Island in the Pacific. Three devices were scheduled for the first series, held in mid-1957, and Orange Herald was the second. The first and third were attempts at fusion devices, which were not wholly successful, but showed ‘proof of principle’. Grapple had been described by the British Government as ‘H bomb’ tests, and the press reported the Orange Herald test as an ‘H bomb success’. Orange Herald was not an ‘H bomb’, but rather a large fission device, although one can understand why the Government did not draw attention to this. This has led some later commentators to suggest the deception was deliberate – that if the fusion tests had not worked then the Government could always claim success via the Orange Herald test, whose yield was around 720 kT.

Although as we will see, Orange Herald was never deployed in its original function as Blue Streak warhead, it did come into service in a rather indirect way. The fusion tests later in 1957 were successful, but there was still a long way to go between the testing of the ‘physics package’, as the part that goes bang is sometimes called, and deployment of a fully serviceable weapon with all its handling and safety devices. Mainly for political reasons, a high yield warhead was required for the V bombers so that the Government could say the RAF had a ‘megaton capability’. The answer was a reduced yield (400 kT) version of Orange Herald, codenamed Green Grass.

Initially, the warhead was mounted in the casing of the original British atom bomb, Blue Danube, and the resultant weapon named Violet Club. Owing to the large amount of fissile material (U235) in the warhead, there were some very considerable operational limitations. Any mishandling of the device which caused it to become damaged might result in sufficient fissile material coming into contact so as to cause a low level explosion. One safety device used to prevent this happening was several hundred ball bearings, which filled a void inside the warhead and physically kept the fissile material apart. If Violet Club had ever been flown operationally (which is unlikely), the ball bearings would have had to be removed before take-off. A later version was produced in a different casing (Yellow Sun Mk 1) which allowed the ball bearing to be jettisoned in flight! The number of Green Grass warheads produced was quite limited, partly due to the amount of fissile material needed, and, given the constraints with which the weapon had to be handled, the RAF was quite glad when it was replaced by a fusion warhead.

The testing of Orange Herald meant that RAE could now move on with the design of a re-entry vehicle for Blue Streak, but to do so meant that AWRE had to supply details of the warhead in terms of masses and dimensions. Little was forthcoming, until a slightly indignant memo in May 1958 from the Deputy Director at RAE noted that

… it was learned that no work was in progress on Orange Herald at AWRE, nor was there any intention of doing any. Newley suggested that our work, based on Orange Herald, should be stopped, and that AWRE would offer instead a two-stage warhead of similar weight… Orange Herald had very doubtful in-flight safety, and is highly vulnerable to R effects, and the new proposal is welcome in that it would be greatly superior in both these respects. Nevertheless, it seems to have emerged in a most casual fashion.5

The ‘R effects’ mentioned refer to a perceived vulnerability of warheads to neutron irradiation. Orange Herald, with its large amount of U235, would have been very vulnerable to such effects.

The two-stage device referred to would be some variation on the fusion weapons that had been tested at Grapple. These went under the generic code name of ‘Granite’ devices (e. g. Green Granite, Purple Granite etc.). Hence the RAE, who was responsible for the re-entry vehicle, dropped their work on Orange Herald, and waited in anticipation for details of the size, shape and weight of the new Granite devices.

There then followed one of the greater ironies of the British nuclear weapons programme. Nuclear co-operation with the United States had ceased soon after the end of the war, and Britain had gone it alone in the development of firstly a fission device and now a fusion device. In many ways, the achievement was quite remarkable, as Aldermaston, with its relatively small budget and limited resources, produced a working fusion design less than three years after work had begun. As a result of Aldermaston’s success, the Americans agreed to resume nuclear co-operation. The UK was given the designs for two nuclear warheads, one of them being the Mark 28, approximate yield 1.1 MT. The advantage to the UK was that the design had been fully engineered as a weapon rather than just as an experimental device, and so the Granite designs, painstakingly developed by Aldermaston, were dropped in favour of the Mark 28. The anglicised version of the Mark 28 would go into service as Red Snow.

The major problem to continuing with ‘weaponising’ a Granite design was that further nuclear testing would have been required, and public and world opinion was turning very much against atmospheric nuclear tests. Britain did not have an underground testing facility, and so the advantages of adopting the American design were that much greater. Hence if Blue Streak had been deployed operationally, then the warhead would have been the 1.1 MT Red Snow.

Whatever the warhead, it seemed that its weight would not come under a ton, which imposed its own restraints on the design. Thus Air Vice Marshall Satterly wrote in July 1955:

My views are that if we go for the single motor missile we shall always be in trouble over weight and range, and will find ourselves in the early 60’s [sic] still striving to catch up. Let us be bold and go for the twin motor and exploit any future saving in weight in the warhead, or anywhere else, by increasing the range. Let us then review the position in a years [sic] time, when we can put much more reliance on the small warhead and when we are due to consider parallel development of a second missile.6

Sir Steuart Mitchell, CGWL, ‘reluctantly agreed that two motors would probably be necessary to guarantee a range of 1500 nautical miles’. Dr William Cook, Deputy Director at Aldermaston, said that AWRE ‘had not realised how significant was the weight of the small warhead in reaching this decision.’ Reluctantly, given the uncertainties in the payload, it was realised that two motors would be needed to achieve the necessary range. A single motor missile would have been almost identical to the American Thor missile, but the heavier UK warhead coupled with the already limited range of Thor (1,500 miles with the US warhead) ruled out the use of Thor by the UK. This was summarised in a paper by Sir Frederick Brundrett, Chief Scientist at the Ministry of Defence, in June 1956:

The co-operation between the Americans and ourselves on this missile development is extremely good except that which is limited by United States laws governing the passage of information on atomic weapons. We have, in fact, considerably more knowledge on this subject than we are supposed to have and it is vitally important that the Americans are not made aware that we have the information that follows.

The warhead for Thor is being designed to a weight of atomic core of 1,500lb, but the weight of the warhead itself must include the metal sheathing designed to act as a heat sink. The total weight including this sheathing will be 2,600lb if the sheathing is of steel and 3,100lb if the sheathing is of copper. The comparable figures for our own design are 2,250lb, 3,600lb and 4,500lb…

What this means, however, is that if an arrangement could be made for the Americans to provide vehicles to which we could fit our heads, which is a technical possibility, the range of the American vehicle with our head would be reduced to something of the order of 1,100 miles…1

There is no doubt that the single motor design would have been simpler, cheaper, and would have taken less time to develop, but, in a sense, the Air Ministry had painted themselves into a corner. The missile had to be as big as it was to achieve a range of 2,000 miles with a megaton warhead. But no one appears either to have queried this requirement or even decided what the missile was for. Was it a deterrent? Was it actually intended as a weapon that could be used to win a war? Did it need a range of 2,000 miles? The Strath Report, also concluded in 1955, looked at the effect on the UK of just five megaton warheads, and was deeply pessimistic about the result. And if the intention was to ‘win’ a nuclear war with the USSR, how much destruction would have been necessary to annihilate it or, at least, force it to surrender?

The requirement could have been relaxed either in terms of range or warhead – and it does seem odd that no one ever contemplated the possibility of warheads becoming lighter. And given the range as 2,000 miles, why did it have to be a megaton warhead? Would 200 or 400 kT have been sufficient? And could Aldermaston have designed such a warhead within the new weight constraints? Further, the payload weight was pushed up by inadequate knowledge of the re­entry head. It might have been worth putting more research into re-entry before finalising the design. It is possible that a single motor design might have had a better chance of ultimate deployment, being smaller, cheaper and quicker into service. But the assumptions on which the criteria were based never seem to have been questioned in depth.

Europa was a three-stage vehicle (the Perigee Apogee System of Europa II was sometimes claimed as a fourth stage), the first stage being a modified Blue Streak, which had an overall length of 60 ft 4 inches (18.4 m) and a diameter of 10 ft (3.05 m). The take-off mass was 197,500 lb (89.4 tonnes), which included

126,0 lb (57 tonnes) of liquid oxygen and 56,300 lb (25.5 tonnes) of kerosene fuel. At the first stage engine cut-off, the mass remaining, including residual propellants and tank pressurisation gas, was 15,200 lb (6.8 tonnes).

The liquid oxygen was held in the upper tank, which was a pressurised shell without stringers or frames, constructed of welded stainless steel sections with a minimum thickness of 0.019 inch (0.48 mm). The kerosene tank was also of stainless steel but strengthened with internal frames and stiffeners and external longitudinal stringers. The two tanks were separated by a deep domed diaphragm built up of welded segments, and similar domes closed off the top and bottom ends of the tank assembly. The liquid oxygen tank was fitted with anti-slosh baffles.

The propulsion bay was attached to the tanks by a short cylindrical skirt structure which was designed to transfer the thrust loads to the tanks above. In the propulsion bay were two thrust beams from which the rocket engines were gimballed, and the ends of these beams, as well as transmitting the thrust loads, acted as support points for the vehicle in the launcher stand. The bay was of light alloy construction, and housed the combustion chambers, the propellant pump assemblies, the engine control systems, as well as the hydraulic pumps and servo – jacks for swivelling the combustion chambers. The bay was closed at the rear end by a heat shield to keep out exhaust gases and radiant heat from the rocket exhausts. Two panniers were placed on either side of the propulsion bay to house more equipment and instrumentation.

There was initially considerable technical discussion – and controversy – as to the best way to design the tanks, which were the major structural element, and the one where most weight could be saved. It was realised that the high internal pressure – about two atmospheres – required to avoid cavitation at the propellant turbopump inlets could be used to stiffen up a very light structure so that it could take heavy longitudinal and bending loads. A pressure of 30 psi over a 10 ft diameter circle represents a total force of 340,000 lb, which was quite adequate to accelerate upper stages of around 35,000 lb to an acceleration of some 7-8 g.

The liquid oxygen tank was put forward of the kerosene tank in order to bring the centre of gravity as far forward as possible with respect to the centre of pressure, so as to ease the task of the control system. A lighter kerosene tank structure could be obtained if some of the end loading were taken by stringers and frames, since the mass of the liquid oxygen tank under acceleration would need excessively high pressures in the tank.

The choice of tank material, too, was the subject of considerable study, both light alloy and stainless steel being close contenders. It was essential for the tank material to have good strength at liquid oxygen temperature (-183 °C), to be able to withstand kinetic heating, to be readily and efficiently weldable, and be available in uniform sheets of closely controlled thickness. Stainless steel was eventually chosen, made by Firth

Vickers for railway coaches, and with very good physical properties over the range of temperatures required. Individual cylindrical sections were prefabricated from 36 inch wide strips of material.

The two Rolls Royce RZ 2 rocket engines each had a rated thrust at launch of

150,0 lb, giving a take-off acceleration of 1.3 g. The original thrust rating of the RZ 2 engine was 137,000 lb, and this was used for the single stage flights. The higher rating, obtained by an increase in combustion chamber pressure, was used in the later flights.

The turbines were driven by hot gases produced by fuel rich combustion of a small proportion of the main propellants in separate gas generators, and two turbopump units supplied the propellants to the regeneratively cooled thrust chambers. The bright yellow plumes produced from the gas generators can be seen very clearly as the vehicle lifts off. The total propellant flow rate was 1,210 lb/s for the two motors. At high altitudes, the thrust of an engine increases, due both to an improvement in specific impulse brought about by a more efficient expansion of the exhaust gases, and to increases in propellant flow rates as the hydrostatic heads at the propellant pumps rise with vehicle acceleration. Sea level S. I. was around 248, vacuum S. I. was around 285.

The main function of the pressurisation system was to provide pressure in the liquid oxygen tank to preserve its structural integrity, to provide sufficient pressure at the pump inlets to suppress cavitation, and to control boiling of the liquid oxygen. The pressurisation system operated in two principal modes: ‘standby’, with the tanks full of propellants, the pressure in the liquid oxygen tank was maintained at about 9 lb/in2 and about 5 lb/in2 in the kerosene tank; and ‘flight’, when the pressures were raised to 30 and 15 lb/in2 respectively, starting about one minute before lift-off. The ‘standby’ pressures were chosen to provide adequate stability of the vehicle under conditions of ground loading, winds, etc., and the liquid oxygen in its tank would be in a state of equilibrium boiling. For ‘flight’, a low-pressure vent valve on the liquid oxygen tank was closed, and the combined effects of atmospheric heat input and of nitrogen supply from the pneumatic control unit raised the pressure to flight level in about 30 seconds. During the raising of pressure in the liquid oxygen tank, the pressure in the kerosene tank was raised so that the differential pressure across the intertank diaphragm was maintained at a safe value. The engines were then started. During flight, internal supplies of gas were needed so that the pumps did not cavitate or the tanks collapse. This was done with two heat exchangers or evaporators, one of which used the waste heat in the exhaust gases from one turbine to provide gaseous oxygen for pressurising the liquid oxygen tank, using a feed from the liquid oxygen pump discharge. The other, associated with the other engine,
evaporated liquid nitrogen supplied from a storage bottle on the vehicle to pressurise the kerosene tank.

One distinguishing feature of the flight models of Blue Streak (and, later, Black Arrow) was the spiral painted around the vehicle, which can be seen in the photograph on the right. This was for the benefit of the cameras filming the launch, and was the brainchild of an Australian mathematician, Mary Whitehead. In an interview some years later, she had this to say of the pattern:

The zig-zag pattern on the Blue Streak – that was at my request, because we were required to know whether the missile rolled as it went off [the launcher]. There were, I think, three or four cameras – they were called launcher high speed cameras – around [the launch site], so with that pattern, if the rocket rolled you could measure it really easily, depending on where that diagonal was relevant to the top and bottom stripes.

I had seen the black and white checks that were used on other missiles. I think that might have been in America, and this was the same sort of thing. But making a continuous line like that, you could measure to a degree whether or not it had rolled: as far as I know, I don’t think they did.

The interstage skirt was a stainless steel corrugated truncated cone, 1.23 m high, tapering from 2.8 m to

2.0 m, which weighed 137 kg. A small solid fuel motor was used to separate the two stages: it provided a thrust of 40 kN for 2 seconds.

The design of the second stage, also called Coralie, was constrained by several factors. Its size was set by the weight that Blue Streak could carry, and Blue Streak had been designed as a ballistic missile, not as the first stage of a satellite launcher. The 2 m (approximately 78 inches) diameter was certainly wider than the planned 54-inch Black Knight stage, which had the advantage that the vehicle was less flexible. The original brochure design had only one motor: the four motor design made control easier, particularly in the roll mode, and also meant that the interstage structure could be shorter and thus lighter.

The stage had a mass of 1,850 kg, of which 9,850 kg were fuel (100 kg of this was left at burn out) – 6,440 kg of dinitrogen tetroxide and 3,410 kg of UDMH. The chambers were pressure-fed from a gas generator, which used 41 kg of dinitrogen tetroxide together with 18.5 kg of UDMH and 98 kg of water, the water being used to lower the temperature of the gases to 350 °C. The pressure in the tanks was maintained at 18.6 bar (the combustion chamber pressure was 13.7 bar). Each chamber had a thrust of 68.1 kN (15,300lb) and a burn time of 75 seconds.

There is no doubt that choice of pressurised tanks did make the stage structurally rather inefficient. The choice was made in part to save time – the French had had little experience with turbopumps. A gas generator was lighter than simply using compressed helium gas, and a similar system had been in use on the Veronique sounding rocket. In addition, the same gases were used to drive the steering mechanism for the chambers and to generate the on-board electrical power supply.

Attempts were made to test the stage separately, with a vehicle called Cora1. The Cora 1 version used only the French Coralie stage, while the Cora 2 version added the German Astris stage. The Italian Europa nose fairing was also tested. For these tests the rocket nozzles were shortened to allow sea-level operation and four fins were added for stability. In the event, only the Cora 1 version was tested, and this failed on two out of three attempts.

The interstage structure was a cylinder 1.23 m long with a mass of 137 kg. Separation of the third stage was by explosive bolts, which caused problems in some of the early flights.

The German third stage, also known as Astris, was powered by dinitrogen tetroxide and Aerozine 50, an equal mixture of hydrazine and UDMH. This was stored in a spherical titanium tank 1.2 mm thick. The helium gas was stored in two bottles made of glass re-inforced plastic pressurised to 300 bar. The main motor had a thrust of 22.5 kN and two small control chambers of 500 N thrust (in vacuum). Since the chambers were to run in vacuum, the pressure in the chambers was a relatively low 11 bar. For a small vacuum stage where a restart capability could be useful, a pressure feed had advantages over turbopumps. The all-up mass was 3,370 kg (7,420 lb) and the empty mass was 610 kg (1,340 lb).

Germany had, of course, been the world leader in rocketry up to 1945, but the diaspora of rocket scientists and technicians, coupled with the perceived militaristic nature of rocketry development, meant that no significant work had been done since. On the other hand, there are advantages in starting again from scratch. Some of the initial German ideas for the third stage were very ambitious, and design studies for a high energy stage were outlined by Dietrich Koelle of Bolkow at a European Spaceflight Symposium in May 1963 . The paper mentioned that ‘Since 1961 intensive studies have been carried out at Bolkow Entwicklungen concerning an optimised high energy stage OPMOS’.

The three designs were ‘based on the propellant combinations H2/O2 and H2/F2 pressure-fed, and H2/O2 pump-fed. The results of the studies indicate that the payload capacity of the ELDO launch vehicle can be increased by the

introduction of a high energy upper stage from the present 220 lb to some 1,550 lb for escape missions.’ The studies were not merely theoretical: ‘Small hydrogen cooled engines have been on test for some time at the firm of Bolkow’.

The motor chamber was also distinctly unusual. It would provide 8,650 lb thrust, and used an Expansion – Deflection nozzle, where the flow is expanded radially and then turned axially. It has the advantages that it is a good deal shorter than the conventional rocket chamber, as seen in the artist’s representation above, and also allows for a greater expansion of the exhaust gases.

Calling the PAS a fourth stage was perhaps overdoing things slightly, but it was designed to enable Europa to put a satellite into geostationary orbit. It was described thus by J. Nouaille, who was the Project Management Director, in 1968:

… A lower metallic skirt attaches the stage to the top of the Europa I third stage. At the upper part of this skirt a separation mechanism releases the PAS system from the third stage when appropriate.

Four small rockets fixed on top of the perigee motor, approximately in the plane of the centre of gravity of the PAS system, spin up the vehicle, as soon as separated from the third stage, to a velocity of 120 rpm.

The perigee motor is then ignited, giving the vehicle an increment in velocity of approximately 2,450 m/s.

The main characteristics of this motor are:

empty mass 70 kg mass of propellant 685 kg

specific impulse 278 s maximum pressure 61 bar

maximum acceleration 10.3g

After burnout of the motor, a second separation occurs between the empty spinning perigee stage and the spinning satellite.

During the whole of its operation, the perigee stage is controlled and monitored by electronic equipments attached inside the upper skirt of the stage (equipment bay).

Apogee Motor.

The apogee motor is part of the satellite. It is ignited by a telecommand order at the most appropriate moment, taking into account the actual orbit and attitude data of the satellite.

Its main characteristics are:

empty mass 36 kg propellant mass 156 kg

specific impulse 270 s maximum pressure 42 bars

velocity increment 1470 m/s approximately.

The launching procedure of the ELDO-PAS satellite… includes

(a) an injection from Guiana into a parking orbit by the three lower stages of the launcher: after burn-out of the third stage, the attitude of the vehicle remains controlled by a cold gas jet system installed on the third stage. The platform of the Inertial Guidance system is used as a reference during this phase. Ground stations in Kourou (Guiana), Fortalezza (Brazil) and Brazzaville (Congo) are used to monitor the vehicle.

(b) When crossing the Equator, approximately at the longitude of Brazzaville, an accurate orientation of the PAS system is achieved, the PAS assembly is separated from the third stage, and then, immediately, the perigee motor is ignited, burnt out and separated.

(c) The satellite is spinning on a transfer orbit about 300 km perigee and 35,000 km apogee. An accurate tracking is obtained from the Gove station (Australia) and the main data on this orbit and on the attitude of the satellite are collected.

These data are transmitted to the main Control Centre in Darmstadt. The optimum time of ignition of the apogee motor is then calculated. Ignition will take place somewhere over the Atlantic, either at the second apogee of the transfer orbit or more probably at the fourth apogee.