Category A VERTICAL EMPIRE

Liquid fuel rockets need a fuel and an oxidant. The UK used kerosene as a fuel almost exclusively, although a lot of work was done on liquid hydrogen, but sadly no use was made of this work. HTP (High Test Peroxide) was the most common oxidant: this was an 85% solution of hydrogen peroxide (H2O2) in water. The hydrogen peroxide decomposes to steam and oxygen on a catalyst (silver mesh gauze) and kerosene injected into the resultant hot gases ignited spontaneously. However, Blue Streak used engines (see Figure 1 below) licensed from the US and re-engineered, which burned oxygen and kerosene. The measure of the effectiveness of a rocket motor or fuel combination is called Specific Impulse. This was always written in documents of the period as S. I., but nowadays is usually written as Isp. This can be defined in many different ways: one is thrust times burn time divided by mass of fuel burnt. Another way of looking at it is the thrust obtained from each pound of fuel burned per second. The HTP/kerosene combination had a relatively low S. I., around 210-220 at sea level. Oxygen/kerosene gives an S. I. of around 245 at sea level. The effectiveness of a rocket motor is increased at high altitude or in vacuum. This is because 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. Thus S. I. is sometimes quoted at sea level and sometimes in vacuum. Vacuum S. I. is typically 10-15% higher than sea level. Hydrogen/oxygen is the most effective combination of all, reaching S. I.s of at least 400. This means double the thrust for the same weight of fuel (and burn time). Against that, there are weight penalties in the use of liquid hydrogen, since it has a very low density and needs large tanks. It is also very cold, boiling at -253 °C or 20 K, so the tanks usually need extra insulation, which in turn implies a further weight penalty.

Rocket chambers will, not surprisingly, get very hot, and ways have to be found to stop them getting too hot. One method is to use film cooling. At the top of the chamber is an injector, where the fuel and oxidant enter the chamber, and it usually resembles a shower head. It is designed so that the fuel and oxidant can mix and burn as quickly as possible. In film cooling, the injector feeds in only fuel at the very edge of the chamber, so that the sides of the chamber wall will be in contact with relatively cool unburnt gas. This usually means a slightly reduced efficiency, as the motor is running fuel rich. The next and most obvious method is to use the incoming fuel to cool the chamber walls before being injected into the chamber. This is called regenerative cooling. One way to do this is to have a double walled chamber, with the fuel flowing between the two walls. This tends to be rather heavy – the pressure in the chamber is obviously quite high, and so the walls need to be robust. This is illustrated in the de Havilland Spectre motor shown in Figure 6.

A refinement on this method was to make a chamber of thin nickel tubes brazed together. Reinforcing bands were usually attached around the tubes, but overall, the construction was much lighter. This technique was first used in the RZ 2 motor for Blue Streak and the chambers of the Stentor motor for the Blue Steel missile. Fuel or oxidant then flows through the tubes to cool the chamber.

Sometimes the expansion cone for upper stages is left as plain metal, and this is sometimes referred to as ‘radiation cooling’ – in other words, the metal is left to glow red hot and literally radiates its heat away into the vacuum of space.

Lubbock and his co-workers at the Fuel Oil Technical Laboratory in Fulham, London, were the first in the UK to work on liquid fuelled rocket motors. Their first design, called Lizzie, was fuelled by LOX (liquid oxygen) and petrol. It was a very simple device: the propellants were forced into the combustion chamber using high pressure nitrogen, so no pumps and other ancillary equipment were needed. It was intended for rocket assisted take-off in aircraft such as the Wellington. In 1946 it was the first liquid fuelled rocket motor to be test fired at the RPD Westcott, and was eventually developed to give thrusts of up to 2000 lb.

Lizzie was used to power the Liquid Oxygen Petrol/

Guided Aerial Projectile, or LOP/GAP, which was an

early test vehicle, fired from

Aberporth in Wales, and later, the Rocket Test Vehicle 1 or RTV-1. Problems cooling the engine led to a change of fuel to a methanol/water mixture. As a consequence of work with Lizzie, it was realised that hydrocarbons did not act as good coolants for rocket engines, and that their flame temperatures are also relatively high, exacerbating the cooling problem. Kerosene was not considered again for rocket motors in Britain for some years.

To provide for the large consumption of liquid oxygen, a manufacturing plant has been constructed at Spadeadam. The plant is capable of producing a total of approx. 100-tons of liquid oxygen per 24-day in addition to liquid and gaseous nitrogen. The liquid oxygen is transported by road tankers from the plant to the storage tanks in the test areas, the nitrogen gas is pumped by pipeline to high pressure reservoirs in each of the areas.21

Spadeadam was built by the Ministry of Works under the supervision of the Ministry of Supply. It was one of the few areas of the whole MRBM programme over which the Treasury had direct control. (It was probably also the most expensive – the estimate of the cost at the time of cancellation was around £24 million). They kept spending under a tight rein, an example of this being when PFG Twinn of the Ministry of Supply wrote to the Treasury asking to be able to spend up to £10,000 on particular items without seeking direct Treasury authorisation. Reluctantly, the Treasury agreed.

Spadeadam was obviously extremely remote, which is why it was chosen in the first place. This did lead to transport difficulties, particularly when showing visitors round. Twinn requested authorisation for some transport in the form of:

1 Ford Consul Black with Heater Saloon 4-6 seats £556

1 Ford Prefect ditto ditto 4 seats £42422

To which the Treasury replied:

We approve the purchase of the Ford Consul, but would be grateful if you would substitute a Ford Popular for the proposed Ford Prefect. Hundreds of Populars are in use in Government service, and we would rather keep to this cheaper 4-seater model.

It really is quite extraordinary that the ministries should be debating the relative merits of a Ford Prefect or a Ford Popular. One cannot quite see the same problem arising at Cape Canaveral.

In July 1959, an official from the Treasury, Mr JA Marshall, set off to inspect Spadeadam in the company of Mr William Downey from the Ministry of Supply. ‘The visit was enjoyable (in spite of almost continual rain) and instructive,’23 he remarked.

In general, he approved: ‘The administrative block is a modest and simple construction as far as I saw it, and there certainly appears to be nothing lavish here.’

But later he was to observe one example of:

… what I would regard as some extravagance.

This is in the housing of the lines which run from the control and recording centre to each of the four stands. It has been put wholly underground. in a tunnel some 400 yards along.

Other cables had been put in an over ground duct. Mr Marshall enquired why this had not been done here. He was told: ‘. had it not been so placed, it would have obscured the view of those in the control centre’.

It also had to be carried under a road, but Mr Armstrong was not entirely convinced it had been necessary to put the entire length of cable underground.

Despite this particular example of ‘extravagance’, Mr Marshall seemed satisfied with his visit. He was ‘well impressed by all I saw’, which included the control rooms, full of:

electronic instrumentation provided to record every possible facet of the test for subsequent analysis. To the layman this produces a hopelessly bewildering mass of knobs, buttons, recording graphs, lights etc’

He goes on:

Mr. Downey had the courage to ask the schoolboy question: “Which is the button which actually sets it going?”. The scientist who was showing us round was utterly at a loss for about a quarter of a minute!

There were other problems. ‘Commander Williams, the senior Rolls Royce representative, who is the general manager of the place, had a go at me on two minor things’.

This related to the housing which had been built for those working at Spadeadam.

He said he thought the Treasury were unduly mean in not allowing them to build a higher proportion of garages… a number of people who have no garages… do have cars and keep them standing in the street… Since the streets are fairly narrow – the whole estate is on very modest lines – this could be a serious nuisance…

And also:

He also thought we underestimated the difficulties they faced when we insisted on a certain proportion of the houses having two bedrooms instead of allowing them to be all three, or in a small number of cases, four-bedroomed.

How much was the Treasury saving? Mr Marshall noted that ‘… the additional capital cost of the three bedroomed house is only £70 …’, but on the other hand, ‘we get an extra 5s. a week rent back from it’.

5s. means 5 shillings, or 25p in decimal money. The extra room would have paid for itself in just over five years.

If Blue Streak had gone ahead in its military guise, then a considerable number (no figure has been found, but a reasonable estimate might be between 10 and 20) of experimental and proving vehicles would be needed, as well as the 60 or so production missiles, starting in 1960 and ending by about 1966. Somewhat optimistically, the development schedule had called for the first missile to be fired from Woomera around mid-1960. As it was, the first vehicle was not fired until 1964, and there were a total of 11 firings by 1971 (in practice, more were built and tested, as there were some basic, non-flight, development vehicles, and also some which were used to check at the sites at Woomera and Kourou).

Thus after the cancellation, the tempo of work slowed considerably, and only one of the missile test stands, C3, was completed. There were also inevitable redundancies and a considerable drop in morale. In May 1967, Val Cleaver, Chief Engineer of the Rocket Department at Rolls Royce, wrote of the need ‘to raise morale and inspire some confidence in the future of the establishment’24, but apart from the test site for the liquid hydrogen RZ 20 motor, no further development work was carried out at Spadeadam.

Spadeadam would take time to build, so whilst it was being constructed, Rolls Royce used the P stand at Westcott for preliminary testing of the Rocketdyne derived RZ 1. Most of the runs were of very short duration – usually just a few seconds. Progress was delayed by a spillage of liquid oxygen onto the steel girders, which caused them to crack. One of the longest test runs was also the last, on an open day at which the Press was present. A motor was fired for 20 seconds, and on being checked after the firing, it was found that the gear box between the turbines and the pumps had disintegrated. A fraction of a second more, and the firing might have become very spectacular.

So from mid-1957, testing and development proceeded apace. At Hatfield in

Hertfordshire, large structures were built to house the testing of early, non-flight vehicles. These were for checking the strength of the vehicle structure and for such tasks as determining whether half a ton of fuel could be pumped from the tanks each second. Engine testing was carried out separately by Rolls Royce, first at a test site at Westcott and then at the purpose-built facility at Spadeadam in Cumbria. Here, in addition to engine development, assembled vehicles could be static fired. Once tested, they would then be taken apart for transport to Woomera.

Transport proved to be a difficulty. The large size of the tanks meant that very few aircraft would be suitable, and those which were, such as the Bristol Freighter, had limited range. This meant a great many countries would be overflown on the route from the UK to the Antipodes, and, given the nature of the cargo, political difficulties were foreseen. The problem was solved when the RAAF bought Fockheed Hercules aircraft: one of these could be leased from Australia for the purpose. And given the extra range of the Hercules, the overflying problem could be reduced by going westward round the world, over Canada and the US. As it would turn out, the tank of the first missile was at Fos Angeles when the cancellation was announced, and it was returned to the UK. All subsequent civil vehicles were transported by road and sea.

Another of the major problems in the early development was that of guidance. The contract had been given to Sperry, but they were struggling: ‘… accuracies being demanded from the inertial equipment for this project are extremely high and very marginal. It does seem that these accuracies are just

Figure 43. Cutaway view about obtainable,..’25 in January 1956. There is a of Blue Streak. despairing cry from the Director of Air Navigation in

October 1956: ‘There does not yet exist, I believe, anywhere in the world a gyroscope suitable for Blue Streak.’26 This was not quite true: American gyroscopes were very much more advanced, and Ferranti was eventually given the job of adapting Kearfott gyroscopes for the guidance system. Although these were probably not the best the Americans had under development, they were perhaps the best they were prepared to make available to the UK. And in November 1956: ‘It will thus be seen that, though the Blue Steel situation is parlous, the Blue Streak position is even more desperate’. A working design was finally produced, although in the end it was never used: the guidance system was cancelled at the same time as the missile. A satellite launcher needed a much less complicated system, and scrapping the Blue Streak inertial guidance could save money.

As the 1960s progressed, inertial navigation was to become much improved: a system designed for the TSR 2 aircraft was adapted for Black Arrow. Blue Steel was left to soldier on with a much earlier design, which, with its valves, was very power hungry. Again, the penalty was being paid for being early in the field.

But the next, and most controversial, point about Blue Streak was to be its proposed means of deployment. To have the missile sited on the ground in the open, as the Thor missiles were, was pointless. A pre­emptive strike by relatively few Russian missiles would have destroyed every site before a missile could be fired in retaliation. As all sides in the Cold War realised, land-based missiles would have to be sited in ‘invulnerable’ silos, although the word ‘silo’ was not in usage in the UK at that time. Indeed, the two phrases used became code phrases, showing which side of the controversy you were on. ‘Underground launcher’ was the phrase used by those in

favour of the project, ‘fixed sites’ if you were against. ‘Fixed sites’ were perceived as being vulnerable. Airfields, somehow, were not perceived as being vulnerable – although they were as ‘fixed’ as any missile launcher. [4]

23 TNA: PRO T 225/1424. ‘Blue Streak’ medium range ballistic missile: test site, Spadeadam. JA Marshall 10 July 1959.

24 TNA: PRO AVIA 92/232. Spadeadam: liquid hydrogen-liquid oxygen thrust chamber test facility. Cleaver to CGWL.

25 TNA: PRO AVIA 54/2135. Blue Streak development: inertia guidance.

26 Ibid.

What was Black Knight, and why was it necessary?

One of the many unknowns when work began on Blue Streak was what would happen when the vehicle carrying the warhead re-entered the atmosphere. To cover a range of 2,000 miles or more, the vehicle would have to be travelling at very high speed – around four kilometres a second. The time of flight would be of the order of 20 minutes, most of it spent in the vacuum of space. Various problems arise when the vehicle re-enters the atmosphere. Firstly, will it be aerodynamically stable? Secondly, will it be able to withstand the forces imposed by the deceleration? Thirdly, will it simply burn up, as a meteorite does?

The point at which all the aerodynamic forces of the vehicle act is called the ‘centre of pressure’. It is important that the centre of pressure is well behind the centre of gravity, otherwise the vehicle might ‘flip over’. Whichever shape is chosen, it must be stable, else its flight path cannot be predicted with any accuracy.

A sphere can be ruled out immediately: it is aerodynamically unstable and will tumble as it falls (Eiffel demonstrated this by dropping cannonballs off his tower). An alternative shape is a cone with a rounded base, and this can be oriented so it enters the atmosphere ‘blunt end first’ or ‘sharp end first’. The ‘blunt end first’ configuration is familiar from the Mercury, Gemini and Apollo capsules. The ‘blunt end first’ also has a much higher drag, or air resistance.

The ‘sharp end first’, having a lower drag, is not slowed down so much in the thinner upper layers of the atmosphere. Instead, it is still moving fast when it meets the denser air lower down. The result is that the deceleration is then more abrupt, the forces greater and the peak heating greater. The advantage from a military point of view is that it would be much more difficult to stop, and it would also be rather more accurate.

The heating effect was another unknown. Effectively, the kinetic energy of the vehicle is almost all converted to heat in a very short period of time. This does not happen by ‘friction’, as is commonly stated, but by a different mechanism. The air in front of the vehicle is being compressed, and when gases are compressed they heat up. To compress them, work has to be done; this work appears as heat. If the heat is given no chance to escape, then the heating is described as ‘adiabatic’. Heat is then transferred from the hot gases to the vehicle.

RAE decided to go for the ‘sharp end first’ design, and carried out calculations on the effects of re-entry.1 Calculations are one thing; what happens in reality is another. There was only one way to find out: fire a model re-entry head vertically upwards, and see what happens when it comes back down again. To achieve a speed of 4 km/s on re-entry meant sending the body 800 km high. In addition, RAE wanted to carry instruments in the head to measure temperatures and accelerations, so it had to be a reasonable size. A re-entry head weight of 200 lb was chosen.

An example of the shape chosen is shown above – this is a drawing of the re­entry head flown on BK09.2

The next question was what sort of vehicle could launch the model re-entry vehicle? Could a solid fuelled vehicle do the job? The advantage of using solid fuel motors is that they can be clustered together ‘off the shelf’. A further advantage is that of staging: it is quite easy to arrange a stack of solid fuel motors into a three or four stage vehicle.

One crude method of estimating the effectiveness of a rocket motor is to estimate its total impulse – that is, thrust x burn time. Black Knight as originally designed gave a total impulse of around 2,300,000 lbf. seconds, whereas one of the larger solid fuel motors of the time, the Raven VI, gave a total impulse of
around 450,000 lbf. seconds. Hence five Ravens would give the same impulse. Using solid fuel motors also made staging easier, producing a more efficient vehicle. The sketches on the left show some possible two stage vehicles.3

On the other hand, another way of estimating the performance of rocket vehicles, as mentioned earlier, is the mass fraction or mass ratio, which is defined as (initial mass)/(final mass). Here Black Knight would have won hands down: any British solid fuelled vehicle of the time would have had a very poor mass ratio, whereas that of Black Knight was extremely good.

The RAE estimated that the mass ratio for a solid fuel motor of around one million lbf. seconds impulse would be in the region of five. For Black Knight, the ratio turns out to be 18. In performance terms, this means that, all other factors being equal, Black Knight would have a final velocity nearly double that of a solid fuel motor design (to be precise, 1.8 times greater). In addition, a large solid fuel vehicle would not have been so easy to steer, whereas Black Knight was steered by swivelling the liquid fuel chambers.

But there was also another reason, never quite spelled out, which was that Britain had never built a ballistic rocket before, let alone one on the scale of Blue Streak. Black Knight would be a chance to gain experience not only in the building of such rockets, but also other matters such as launch technique, and so on. Indeed, de Havilland was given the responsibility for the launches at Woomera, in anticipation of Blue Streak, and somewhat to the chagrin of Saunders Roe.

Since the specification4 was for a quick and inexpensive solution, then it was obvious HTP motors would be chosen, and since RAE was running the programme, then it was also fairly obvious that RPE’s motor, the Gamma, would be chosen. The Gamma had a thrust of around 4,100 lb; four of them clustered together gave a thrust of 16,400 lb. This set the weight of the vehicle: a lift off

acceleration of 0.3 g meant an all-up weight of (16,400/1.3) lb or around 12,600 lb.

Armstrong Siddeley (as they then were) at Anstey were given the contract to build and test the new motor, which would be called the Gamma 201. When the motor for a particular vehicle was completed, it would be taken down from Anstey to Cowes, to be mated to the tank section. Saunders Roe then needed a site to carry out static testing – where the vehicle is filled with fuel and the motors fired, but without releasing it. The Needles battery at the end of the Isle of Wight was War Office property, but was now surplus to requirements. Saunders Roe proposed building the site close to the battery, just round to the south, in a natural amphitheatre formed in the chalk.5 The area was known as High Down, and Figure 81 below shows the site soon after completion. The two gantries were where the vehicles were held down for static testing. The site has not yet been landscaped, as can be seen from the areas of raw chalk.

Some of the site is still in existence, principally the curving concrete walkway in the amphitheatre. Figure 81 (bottom) shows the site as it was in 2010, more than 50 years after it was constructed.

In the centre was the control room: test firings were carried out from here and the various instrumentation read outs were recorded. In the 1950s, the main method of recording data was by using a pen recorder with a long strip of paper. All the instrumentation would have been analogue. At each end of the walkway
was a gantry, the bases of which remain today. The vehicle would have been mounted inside the gantry, and below was a large iron blast deflector, which could be water-cooled during engine tests. The gantries and control rooms were designed to be as identical to their Australian counterparts as possible so as to reduce the chance of problems on countdown or launch. There would also have been tanks behind the main site for the kerosene and HTP, as well as workshops and other facilities. According to the architect, the part of the site that gave him greatest difficulty was the water reservoir for cooling the blast deflectors: the water had to be pumped up from nearby Yarmouth through a very inadequate water main.6

In these days of Green Belt, planning permission, NIMBYism, and so on, it seems incredible that a rocket test site could be built on one of the most scenic sites in Britain without objection, but it was also obvious from the files that the idea of anyone objecting did not occur to the official mind. The site belonged to the War Office, was now surplus to requirements, and a test site was needed. Planning permission as we now know it was not necessary in those days.

It is indeed a scenic spot, now owned by the National Trust. Cars are not allowed along the cliff road up from Yarmouth, but there is a bus which runs up to the Needles Battery for those who do not care for the walk. The site overlooks the Needles rocks and lighthouse. Beyond the lighthouse is the Shingle Bank, and even on the calmest days, broken water can be seen here. In the far distance are the chalk cliffs of Studland Bay and Swanage, with the Purbeck Hills in the background. Equally, it must have been a bleak place in a southwesterly gale in winter.

The Saunders Roe brochure for the proposed test site stated: ‘The cost of renovating existing buildings, cutting the road and installing the complete test facility is estimated to be no more than £45,000.’7 This turned out to be somewhat optimistic, but to build a static test stand for that figure is good value for money.

Black Knight was a slim cylinder, 3 ft in diameter. Its exact height would vary depending on the payload, but it was 32 ft 3 inches to the top of the separation bay. Initially it was a single stage vehicle; later versions used a solid fuel Cuckoo motor as a second stage. Some also used some small Imp motors to push the re-entry head away from the main body, but to describe this as a three stage version, as some RAE reports did, is being a little optimistic.

Starting at the bottom, there was the propulsion bay, 36 inches diameter and 56 inches high, which held the four

Figure 82. An early Black Knight at rocket chambers, the turbine to drive the Woomera. This is an early ‘proving pumps, hydraulics and other equipment, round’, whh a non-separating head and was built by Armstrong Siddeley at

Anstey, before being taken down to Cowes to be attached to the tank section. It was easy to dismount for transport, and could be tested and calibrated before being assembled into the vehicle.

The thrust chambers were ‘toed in’ slightly so that the thrust line passed through the centre of gravity. Four fins were fastened to the engine bay; these were for aerodynamic stability during flight. Attached to two of the fins were pods. One held a radar transponder (a transponder receives the radar signals and rebroadcasts them to give a stronger signal), the other a telemetry transmitter to return data, and an electronic flashgun. This was set to flash every four seconds, and since the launch was at night, the vehicle’s progress could be followed

о

optically.

Above the engine bay was the HTP tank, 208 inches long along the cylindrical section. Two tubes of manganese dioxide were attached to the tank, and if the destruct signal was sent, explosive would drive the black powder into the tank. Manganese dioxide is a catalyst for the decomposition of hydrogen peroxide, and the resultant steam and oxygen gas would blow the tank apart.

The bay between the HTP and kerosene tanks contained air bottles which were used to pressurise the HTP tank. The kerosene tank was not directly pressurised, as the hydrostatic head was sufficient to prime the pumps. One striking feature is the size of the HTP tank compared with the kerosene tank: 208 inches compared with 48 inches. The mass of HTP was over eight times that of kerosene, although the greater density meant the volume ratio was smaller.

Above the kerosene tank was the pressurised electronics bay. This housed instrumentation, telemetry, control system electrics, autopilot gyroscopes, a command receiver and electrical power supplies well Figure 83. Etectronic fbsh gun away from the worst effects of engine induced installed in one of the pods attached vibration and heating. Above this would be

to the fins. the payload, which would differ from flight to

flight. The tubes running down the side of the vehicle were fibreglass fairings covering the kerosene feed pipe and the various electrical cables.

Initial ideas for the tank structure was to make it from very thin aluminium (26 Standard Wire Gauge (SWG), which is 0.018 inches or 0.46 mm) supported by 16 stringers.9 This may well have been by analogy with Blue Streak, although the stringers in the case for Blue Streak were there for a different reason. The RAE was uneasy about the structure, mainly because the stringers would experience aerodynamic heating on ascent, which would lead to a variety of problems with them, the main being expansion. If the stringers expanded and the tank did not, then unpredictable stresses would be set up. At least one such tank was constructed; photographs of the setting up of the gantries at High Down and
at Woomera show a white painted stringered missile body being used to check the facilities.

The change to 20 SWG (0.036 inches or 0.914 mm) tank thickness did incur a slight weight penalty, which was estimated at 50 lb. The initial weight breakdown for the vehicle was given as 1,100 lb vehicle weight plus 200 lb for the head, or 1,300 lb. 11,250 lb fuel gave a total weight of 12,550 lb. As is always the case, weights crept up during the detailed design process; the first vehicle, BK01, came in at 1,480 lb.10

Close inspection shows a series of holes cut in the side of the motor bay. These were designed to reduce what is called ‘base drag’. When the vehicle is climbing up through the atmosphere, it encounters air resistance. If the rocket has a blunt end, the air will swirl around behind it, producing extra drag. The purpose of these ‘bleed holes’ was to let air flow in, reducing this base drag.

To test the idea, a small solid fuelled vehicle was prepared, which had four small rocket motors and a take-off weight of 140 lb, the rear section being a scaled version of the Black Knight propulsion bay. Several of these were test fired in Wales, with the conclusion that the bleed holes gave an estimated improvement in the final velocity of up to 200 ft per second. Further tests were needed to check on what is called ‘recirculation’ where hot exhaust gases get swept back into the engine bay.11

One effect which was not appreciated at the time was the expansion of the exhaust plumes in the near vacuum of high altitude. This did cause problems in some of the early launches, when the kerosene supply to the motors was cut, leading to a period of what was called ‘cold thrusting’ – that is, the motors were running on HTP only. This works, but is much less effective. The problem was investigated by firing a Gamma motor in a vacuum chamber at Westcott. The solution was to fit spring loaded flaps over the holes, so that they would open in the atmosphere, but as the air got thinner, the springs would force the flaps shut.

To improve performance further, a small solid fuel motor was added as a second stage. This was the Cuckoo – originally intended as a launch boost for the Skylark (the name apparently derived from the idea that the Cuckoo kicked the Skylark from out of its nest!). The original version was the Cuckoo IA, first flown in April 1960; the Cuckoo IB was identical apart from a changed interface from Skylark to Black Knight. It was replaced by the Cuckoo II, which had an improved performance. The Cuckoo would later go on to be developed further in extended versions of Skylark. The oddest feature is that the second stage is mounted pointing downwards. At the very top, under the jettisonable fairing, is a gas bottle with jets. This was used to spin up the Cuckoo motor after separation
from the main stage, which then coasted up to apogee then fell back to earth. An ionisation gauge was used to detect the start of the atmosphere, at which point the motor was fired. After motor cut off, the head was pushed away from the empty casing so that they would re­enter separately.

An even more elaborate system was used in later flights.

This involved a cradle which was referred to as a ‘sabot’

(French for ‘clog’, but in this context it has the artillery meaning of a device used in a firearm or cannon to fire a projectile which must be held in a precise position). The re-entry head was held in the sabot, which was attached to the Cuckoo motor by a long nylon rope. The aim was to propel the head well clear of the spent motor case.

The sabot system was necessary to keep the second stage re-entry out of the field of view of the instruments tracking the re-entry head. Separation took place at high altitude so as to give the head sufficient time to be at least 20,000 ft ahead of the second stage at 300,000 ft altitude. It was built on a magnesium alloy plate, on which there was an aluminium seat shaped to the re-entry head. It gave the head a velocity increment of the order of 400 ft/second using four Imp X motors. The thrust of the Imps blew off four panels on the separation bay, and in the case of BK20 it is possible that there was some interference at separation. Despite exhaustive ground testing on the range at Larkhill (Salisbury Plain) it was not possible to simulate the effects of vacuum and low temperature on the nylon.12

The lanyard as originally conceived consisted of 8 ft of steel wire followed by 120 ft of undrawn nylon. It was changed to 310 ft of slightly thinner nylon. The steel wire and first 20 ft of the nylon were covered with a woven asbestos sheath to protect it against the flame of the Imp motors, which had a burn time of a third of a second.

The final arrangement was sometimes and somewhat optimistically referred to as a three stage version: the Black Knight first stage, the Cuckoo second stage, and the Imp motors making the third stage. Starting at the top, below the nose cap is a gas bottle, which with attached jets, was used to spin the stage up. Below that is the Cuckoo motor, pointing Figure 87. The lanyard and sabot arrangement. downwards, then the sabot and lanyard arrangement, with the re-entry head itself at the very bottom.13

As we shall see in the next chapter, the lanyard system was not always a success for a variety of reasons.

Changes to Black Knight were made incrementally throughout its life. The other major improvement was to replace the original rocket chambers with ones derived from the Stentor motor – the Stentor being developed by Armstrong Siddeley for the Blue Steel missile. The new chamber was lighter, but equally importantly, it was much easier to control the mixture ratio of HTP to kerosene in the new motor, making it more efficient. The maximum thrust was also greater – potentially 25,000 lb, but in practice an intermediate thrust level of 21,600 lb was used. The new motor was named the Gamma 301. A further refinement was proposed for the 54-inch Black Knight, the Gamma 304, which would have had only one turbine and pump feeding each chamber, rather than the four separate ones in the Gamma 301.

5 TNA: PRO AVIA 48/57. Black Knight: re-entry test vehicle. Saunders Roe Technical Publication 144.

6 Personal communication.

7 TNA: PRO AVIA 48/57. Black Knight: re-entry test vehicle.

8 TNA: PRO AVIA 6/21517. Black Knight electronic flash installation for optical tracking.

9 TNA: PRO AVIA 13/1269. ‘Black Knight’: body tests.

10 Ibid.

11 TNA: PRO AVIA 6/19890. Ballistic test vehicle Black Knight. (Technical Note Number G. W. 503, HGR Robinson.)

12 TNA: PRO AVIA 6/21754. Black Knight vehicles of project DAZZLE and their flight behaviour. RAE Technical Report 68076.

13 TNA: PRO DSIR 23/36396. The Black Knight vehicles of project DAZZLE and their flight behaviour.

Two stage. Launched 6 August 1964 at 02:45. Apogee 374 miles.

This was the first launch with the Gamma 301 motor rated at the full thrust of 21,600 lb, and all vehicle systems were successful. The re-entry head for this flight was a copper sphere, which was recovered the next morning. Although it had split into two and had been scored and dented by the impact with the ground, it was in surprisingly good condition.

The science fiction author Stephen Baxter has written a short story, ‘Prospero One’, about the first and last launch of two British astronauts from Woomera. His ‘Black Prince III’ launch vehicle uses five Blue Streak boosters strapped together (this does seem a little over the top). But what would be needed for a manned capsule? Could it be done with British technology as of, for example, 1964 (and without five Blue Streaks)? The answer is yes – but only just.

America’s first manned spacecraft was the Mercury capsule, which weighed 4,300 lb at launch and 3,000 lb once in orbit (the escape tower was jettisoned during ascent). Mercury was the smallest capsule into which a man could be squeezed; there was no room or weight spare for anything else, and it had very limited endurance. The more capable two man capsule, Gemini, weighed in at 8,500 lb in orbit. Gemini could stay in orbit for several days, and carry a reasonable amount of equipment.

Given the original Black Prince design had a payload of around 2,200 lb into low earth orbit, it would have to be uprated very considerably, but by this time RPE had developed liquid hydrogen motors of around 4,000 lb thrust, so making a motor of 8,000 lb thrust would not be that difficult. The American Centaur stage had a thrust of 30,000 lb; four of the RPE motors gives a thrust of 32,000 lb. Centaur was even built in stainless steel using the same balloon technique as Atlas and Blue Streak; de Havilland could no doubt have built a similar stage without much difficulty. Such a vehicle might be able to put a payload in the region of 4,000 lb into orbit, which is close, but not really good enough.

There is the possibility of strap-on boosters: four Black Knight boosters, stripped of all other equipment, might well serve here. They could be uprated to

25,0 lb thrust, giving an extra 100,000 lb thrust at lift-off. This would mean that there would be weight to spare, so that the liquid hydrogen stage could be considerably stretched. Now we might have a vehicle capable of putting 6,000lb or more into orbit – perhaps sufficient, but only just, and by stretching the design as far as it can go.

All this is achievable with the technology of 1964, although developing the liquid hydrogen stage would involve some years work. As to cost: Gemini cost around $1.25 billion, or roughly £500 million at the contemporary exchange rate. The question arises as to whether it would have been worthwhile putting a British astronaut into orbit… and, regrettably, the answer is no. Gemini was merely a stepping stone to Apollo. Now we have an International Space Station but the financial or scientific return from the ISS is negligible, whereas its costs are horrendous.

The past being another country, they did things differently. I have kept almost entirely to the units of the day. Thus feet and inches. 1 metre is 39 inches. Weight was used where today we would (I hope) use mass. Mass is difficult to define, but can be thought of as the inertia of a body. Weight is the force of gravity on that mass. 1 pound, abbreviated lb (derived from Latin libra), is 0.45 kg.

More annoyingly, force was also expressed in lb, meaning in this context the weight of an object with a mass of 1 lb. Modern usage takes the unit of mass as 1 kg and of force as 1 N. The force of gravity on 1 kg is 9.8 N on Earth at sea level. Thus rocket thrust was defined in pound force, sometimes abbreviated to lbf, or plain lb, which would now be written as 0.45 kg x 9.8 N = 4.4 N. A metric tonne is 1000 kg, an imperial ton is 2,240 lb. By a lucky coincidence they are almost identical.

Pressure was usually given in pounds per square inch, psi, or atmospheres. ‘Atmosphere’ is still sometimes used today under the name ‘bar’ (and by extension, the millibar or mb found on weather charts). The modern SI unit of pressure is the newton per square metre (N/m2) or pascal (Pa). 1 atmosphere or 1 bar is approximately 15 psi or 100,000 Pa (100 kPa).

Orbit heights are usually given in nautical miles above the Earth’s surface. A nautical mile is, strictly speaking, one second of arc of a Great Circle on the Earth, or around 2000 yards. A statute mile is 1,760 yards. Thus a nautical mile is a little less than 2 kilometres.

After all this, the merits of the metric system appear obvious!

Acronyms and Abbreviations

AWE – Atomic Weapons Establishment, situated in Aldermaston, Berkshire, and responsible for the development of British nuclear weapons. Now the AWRE or Atomic Weapons Research Establishment.

BND(SG) – British Nuclear Deterrent (Study Group). An ad hoc group set up to report on the deterrent, and which recommended the cancellation of Blue Streak as a military weapon.

BSE – Bristol Siddeley Engines. Armstrong Siddeley merged with Bristol to form Bristol Siddeley Engines, which was later taken over by Rolls Royce.

CGWL – Controller of Guided Weapons and Electronics. A senior post within the Ministry of Supply. The Controller was responsible for overseeing guided weapons projects.

DRPC – Defence Research and Policy Committee. A high level committee which recommended particular lines of research and development.

ELDO – European Launcher and Development Organisation.

GW Department – Guided Weapons Department at the Royal Aircraft Establishment (RAE). Responsible for missile development.

HTP – High Test Peroxide, a mixture of 85% hydrogen peroxide and 15% water.

JIC – Joint Intelligence Committee. Provides advice to the Cabinet related to security, defence and foreign affairs

OR – Operational Requirement. This was the specification for a new weapon. The requirement would be issued by the Air Staff, and the Ministry of Supply was responsible for circulating the requirement to the various aircraft manufacturers, choosing the winning design and overseeing the development of the project.

RAE – Royal Aircraft Establishment, situated in Farnborough, Hampshire, and responsible for Government-directed research into aeronautics.

RPE – Rocket Propulsion Establishment, situated in Westcott, Buckinghamshire, and responsible for research into rocket motors.

S. I. – Specific Impulse. One of the measures of rocket motor performance. The higher the S. I., the better the performance.

Places

In 1946 the Ministry of Supply asked Armstrong Siddeley Motors to develop a liquid fuel rocket motor with a thrust of 2,000 lb for use as a booster unit for fighters. Initial ideas were for a hydrocarbon/liquid oxygen motor, but after talks with the RAE, the fuel was changed to a mixture of 65% methanol and 35% water. At the time, it was thought that hydrocarbon fuels were not well suited for cooling the chamber. The first test run of the motor, now named Snarler, together with a fuel pump was achieved in February 1949.

Motors designed to be installed in manned aircraft need to be safe and reliable: by May 1950, the motor had achieved 71 minutes of full thrust in testing. A Snarler motor was then installed in the tail of the Hawker P.1040
prototype (forerunner of the Sea Hawk), the new aircraft now being designated the P.1072. Flight trials began in November 1950.

Snarler was capable of being throttled – not always easy to achieve with rocket motors – and had a maximum sea level thrust of 2200 lb. The S. I. of the motor was 195, with a combustion chamber pressure of 300 lb/sq in (2 0bar).

Work on Snarler’s successor, Screamer, began in 1950. Initially intended to give 4,000 lb thrust, the specification given by the Ministry of Supply was changed to a more powerful motor of higher thrust. One of the main differences between Screamer and Snarler is that the Snarler pump was driven externally; Screamer would have its own gas generator to drive the turbines which would power the pumps.

In these early days there was very little design knowledge of gas generators, and it was decided to add water to the combustion mixture to reduce its temperature. Because water was being carried for the gas generator, it was decided to use its excellent cooling properties for the combustion chamber jacket, the heated water then being injected into the combustion chamber itself. Unusually, the combustion chamber had no throat, being a simple cylinder followed by the usual expansion cone.

By 1954, the complete motor was ready for testing, and by September, thrust ratings of 8,000 lb had been achieved. The motor was later installed in the underside of a Meteor for flight testing, but with the cancellation of the Avro 720 rocket interceptor in favour of the Saunders Roe SR53, and the decision to use only HTP in manned vehicles, Screamer was not developed further.

There was one feature in which Blue Streak was ahead of its time, and this feature, by a process of tortuous logic, was to provide the means by which its cancellation was achieved.

One of the defining images of the Cold War was that of the missile silo: the sight of a missile erupting from a hole in the ground conjured up images of mushroom clouds, radioactive fall-out, megadeaths. One of the less known facts about missile silos is that much of the initial research on launching missiles from underground was carried out near a small village in Buckinghamshire – Westcott.

The first American missiles to be deployed – Thor, Atlas, Jupiter – were all deployed on surface sites, with the only protection for the missile being protection from the elements – wind and rain. These missiles were also very large and very fragile. A sniper a mile away could put a bullet through the tanks and disable the missile permanently. They would be damaged beyond use by the blast from an atomic explosive even though it might have been miles away. In the jargon of the day, they were hopelessly vulnerable to a pre-emptive strike. Later versions of the Atlas missiles were kept in hardened shelters – hardened in this context meaning strengthened against attack – although they still had to be removed from the shelters to be erected, fuelled and fired.

The slightly later Titan I missile was housed in a ‘lift and fire’ silo: the missile was prepared for firing in an underground tube, then lifted to the surface for the moment of firing. This reduced the window of vulnerability to a few minutes, but the vulnerability still existed. The only way to make sure the missile could not be destroyed before launching would be the ‘fire in the hole’ method.

The Minuteman solid fuel missiles that America was in the process of deploying were far more robust than the relatively fragile liquid fuelled rockets. They also had a much greater initial acceleration, meaning they would clear the silo quicker, and so providing a hole in the ground for them was relatively straightforward. Blue Streak, on the other hand, would take several seconds to clear the silo, and there were two major problems to be investigated. The first
was whether the acoustic energy produced from the rocket motors would be sufficient to damage the thin tank walls, the second was the problem of gas flow. How could the exhaust gases (and Blue Streak burned nearly half a ton of fuel a second) be deflected away from the rocket? And what of the gas flow within the tube? Would the missile be pulled towards the wall of the tube?

The problem of vulnerability to pre­emptive attack had been recognised from the outset, and reference was made in the original requirement to ‘underground launch sites’ without being specific about detail. Initial ideas were very vague, until a proper research programme was started at RPE Westcott. Initial ideas centred around some sort of ‘U’ tube arrangement, with the missile in one arm of the U. To study the dynamics of the gas flow, a 1/60th scale model of the rocket was used, together with jets of high pressure nitrogen gas to represent the rocket exhaust (it is not surprising that the men who worked on this part of the project lost most of their hearing). Perspex models of various configurations were made, with small woollen tufts to show the air flow.1

The next step was considerably more expensive. A 1/6th scale model U tube was to be built, complete with an acoustic lining, real rocket motors placed inside, and fired. Microphones would measure sound levels. Rather than excavate

DEFLECTOR BOX

EXHAUST DUCT

SR1CK WALL

SIMULATING

GROUND PLANE.

INSTRUMENTATION CABLES

PROPELLANT SUPPLY PIPES

Figure 46. 1/6th scale model of the proposed underground launcher.

a deep hole, the U tube was built horizontally, on the ground, with a brick wall to simulate the ground plane, as shown in the drawing above. Octagonal concrete sections were built and fitted together, some of which can be seen at Westcott today, although, slightly surprisingly, there is no trace of the model silo itself.

The 1/6th scale missile could then be moved up and down and its Gamma motors fired. Various other effects could be investigated at the same time – for example, the effect of the rocket efflux on the concrete at the bend of the U tube. Low temperature concrete was preferred since it merely tended to melt; high temperature concrete fragmented, and the fragments were swept along the tube, gathering more as they moved along. Reading between the lines, some of the test runs could be somewhat alarming, as this excerpt from a report shows:

As was expected, the erosion caused directly by the impingement of the jets was small, but small particles removed from the surface were accelerated by the gas stream, and scoured the curved deflector plate downstream of the point of impingement. The effect was cumulative and persisted in the region of high gas speeds and where the deflector was concave towards the jets… Pieces weighing two ounces or more were picked up about 50 yards from the launcher exit.2

But these were not the only problems. What was the effect of a one megaton explosion half a mile away? What effect would the shock wave have on the launcher and the missile, not to mention the personnel inside? The effect of ‘radio flash’ (now known as ElectroMagnetic Pulse or EMP) was unknown, as were the effects of neutron irradiation. Furthermore, the launcher had to accommodate the launch crew for a period of up to 24 hours after hostilities began. They would need living quarters inside the launcher itself.

There were turf wars from the outset. The Ministry of Works, part of the Ministry of Supply, would normally deal with constructional matters such as these, but the Air Staff wanted to handle it themselves. Aggrieved, the Permanent Secretary at the Ministry of Works appealed to the Treasury to adjudicate. Emolliently, the Treasury wrote back to say that yes, the Ministry of Works had a very good case, but they had decided to leave it to the Air Ministry since it was they who would have to use the end product. So who would the Air Staff appoint to build the launchers? De Havilland were not popular with the Ministry of

Supply, who found them difficult to deal with. In addition, de Havilland was in bad odour as a consequence of their over-spending (the Treasury at one time was considering sending in the accountants Cooper Brothers, predecessors to today’s management consultants).

A minute in October 1957 said of de Havilland: ‘It should be clear that design of underground sites is in no way the responsibility of this firm, which is already showing itself incapable of carrying the load that has been put on it.’3 On the other hand, there were not many alternatives, and, in the end, the firm was given the job in lieu of anyone else. The evolution of the design can be seen in the various documents still in the National Archives, but the final version was given an airing in a presentation at de Havilland’s offices in Charterhouse Square, London4.

The full specification can be seen in Appendix A, but Figure 50 makes the layout fairly clear. The final design is indeed impressive, as the architect’s drawing shows (Figure 51). The figures of the men inside the launcher give some feeling for the scale of the launcher.

Starting at ground level, the emplacement is surrounded by a built-up bank, and the access road can be seen top right. The missile would have been brought on a transporter, then lowered into the missile shaft. The silo is drawn with the lid open, and the launch and efflux ducts can be seen. On the left is the entrance, with its airtight and blast proof doors.

The cylinder is divided into two: one half houses the missile and the shafts, the other houses equipment and the living quarters.

The missile itself is held on a platform attached to the walls by springs or hydraulic cylinders, so that the relatively fragile missile would be insulated from the shock of nearby explosions. There are access platforms around the missile; the warhead would almost certainly be stored separately and would have to be fitted before launch. Around the walls of the shaft is an acoustic lining, product of the research at Westcott.

At the bottom of the launcher is the liquid oxygen tank and the kerosene tanks. Fuelling the missile in the confines of the launcher might well have been a rather hazardous procedure! This was one of the advantages of storable propellants.

Note that the whole launcher is surrounded with a % inch mild steel liner – this, in conjunction with the lid, should act as a gigantic Faraday cage. This was to protect the launcher from EMP which might otherwise destroy all the electrical and electronic equipment inside. Looking at the thickness of the walls, building these launchers would have had a considerable impact on Britain’s production of concrete!

A description of the prototype launcher, code named K11, says:

Basically, the emplacement consists of a hollow re-inforced concrete cylinder, 66 feet internal diameter, extending downwards from ground level to a depth of 134 feet and divided internally into two main sections by a vertical concrete wall. One section houses a U-shaped tube, whose arms are separated by a concrete wall and are, respectively, the missile shaft and its efflux duct. The surface apertures of this U-tube are covered by a lid that can move horizontally on guide tracks. The other main section within the cylinder is divided into seven compartments, each with concrete floor and ceiling, for the various storage, operating, technical and domestic functions.

The internal diameter (66 feet) of the concrete cylinder is determined solely by what is to be accommodated. Protection against [a 1 megaton explosion at Vi mile distance] is given by the lid and by the re-inforced concrete roof walls and foundations. The wall thickness will depend on the geological characteristics of the surrounding rock and may well be of the order of 6 feet. The depth of 134 feet is arrived at primarily to give sufficient clearance below the missile (itself 79 feet long) to allow for de-fuelling and re-fuelling the missile into and from the liquid oxygen and kerosene storage tanks located on the 7th floor.

The 400 ton steel lid could be opened in 17 seconds, and high pressure hoses would sweep it clear of debris first. Two firms, John Brown (SEND) [Special Engineering & Nuclear Developments], and Whessoe Ltd of Darlington, were commissioned to produce designs. Whessoe’s report is dated March 1960, so that it is obvious that the design of the lid had not been finalised by the time of the cancellation. This, combined with the problems of finding a site for K11, meant that the schedule must have been slipping seriously. To have produced a fully working prototype by 1963 or 1964 on this basis looks difficult to achieve.

Brown’s lid was 56 ft by 36 ft, weighing 600 tons. Both were hollow, although with strong internal bracing, and in Brown’s case, 5 ft thick. The Whessoe lid used 3 inch thick steel plate top and bottom. The lids were to be capped with 6 inches of concrete. The rails on which the lid was to run were also of steel, in Brown’s case 7 inches square in cross section, and for Whessoe, ‘12 inch overall width by 5% inch rail width’.

John Brown’s submission noted that

the front edge will have an angled profile to act as a plough in the event of it being necessary to clear any rubble which may accumulate on the track. The two 36’ sides will house pairs of four-wheeled bogies, and a continuous rack will run down the outside of these faces, engaging on a pair of pinions.. .5

When considering the electrical drive mechanism, it was noted that the requirement stated:

A cover weighing 600 tons has to be moved from the open to the closed position in 17 seconds and fine positioned to within half an inch within a few seconds of the end of this period. Alternatively, it has to be opened without fine positioning in 17 seconds. The time allowed for lifting the jacks is 5 seconds so that 12 seconds remain for the operation.6

Provision was also made for keeping the lid free from debris, although the ground shock the silo was predicted to receive would be considerable. There are references in a de Havilland paper to ‘Ground shock… in a vertical direction, an instantaneous step velocity of 2*4 ft/sec is induced, which decays at a uniform rate to zero in one second… in a horizontal direction, an instantaneous velocity of % ft/sec is induced which decays at a uniform rate to zero in one second’, whereas Whessoe notes that there are ‘Acceleration forces on Ancillary Equipment equivalent to accelerations of 2g’7. In addition, the rails would be exposed to heat from the fireball. The question this raises is whether the rails buckle under these loads and hence jam the wheels. A silo whose lid cannot be opened would not have been much use!

Other aspects of the design were to cause concern: the various effects created by a nuclear explosion nearby. Whilst the silo might survive the blast, there were concerns as to the effects of EMP and of high energy neutrons. The RAE Lethality Committee set to work to investigate these effects.

One effect, of course, is the thermal radiation or heating. Being underground, the launcher was relatively immune from this, although the lid and the rails would be exposed. This was not thought to be a significant problem. The high temperatures and energetic radiation produced by nuclear explosions also produce large amounts of ionised matter that is present immediately after the explosion. Under the right conditions, intense currents and electromagnetic fields can be produced, generically called EMP (Electromagnetic Pulse), that are felt at long distances. Living organisms are impervious to these effects, but they can temporarily or permanently disable electrical and electronic equipment. Ionised gases can also block short wavelength radio and radar signals (fireball blackout) for extended periods.

The occurrence of EMP is strongly dependent on the altitude of burst. It can be significant for surface or low altitude bursts (below 4,000 m); it is very significant for high altitude bursts (above 30,000 m); but it is not significant for altitudes between these extremes.

This was the reason for the steel liner to the silo: it would act as a Faraday cage, whereby the strong magnetic and electrical fields pass through the liner without affecting anything inside. For this to be effective, the cage must have no openings through which energy could leak. Studies were carried out on the consequences of such details as pipework into and out of the silo, and what effect they might have.

The main radiation hazard came from high energy neutrons, which would not only affect the warhead but also the crew inside the silo. One of the purposes of the lid was to act as a neutron absorber (the water within the concrete would help).

In addition, the equipment in the silo might be protected against ground shock, but the crew themselves could be seriously injured. There was even a proposal to keep a spare crew suspended in hammocks ready to take over. The missile itself would be suspended on hydraulic cylinders to act as dampers against the ground shock.

The work done at Westcott can be said to have validated the concept of the launcher (it was estimated at the time of cancellation that the Westcott work had cost £1.8 million). It is also of interest that the British design studies preceded any undertaken in the US, and Colonel Leonhardt, deputy commander for Installations, Ballistic Missile Installations, visited the UK to evaluate the design for the underground launcher. Dr Barry Ricketson of RPE travelled to America in 1959, as the minutes of a meeting noted: ‘… Dr Ricketson was at present in the United States giving the Americans the knowledge he had acquired in his studies of the problems of launching ballistic missiles from underground.’8

A similar research programme, which seems closely based on Westcott’s work, was carried out in the US, where again a 1/6th scale model was tested. The Titan II silo design that resulted can be seen to have a family resemblance to the Blue Streak launcher (although similar problems lead to similar solutions). The last Titan silo was not taken out of commission until 1987, which tends to argue against any obsolescence of the UK design.

Within the silo, there would be a crew of three officers and five men per shift, and the crucial point of the OR for the launcher was that:

… the emplacement must be self-contained for an emergency period of four days (covering three days before an attack is expected and one day afterwards).

This is the pivotal issue for the silo concept: early warnings, launch times and the rest were irrelevant. Indeed, although much had been made of the fact it would have been impossible to launch Blue Streak between the time that an incoming attack was detected and the time when it arrived, this misses the point entirely. The UK would never have launched ‘on warning’. There were no facilities for doing so. A man carrying the codes for a nuclear attack follows around the US President throughout his time in office, but in the UK there has never been such provision. There would have been very many times when the Prime Minister would have been inaccessible, such as when he was in his car on the way to Chequers, for example, and authority to launch would not have been delegated to the military.

The point of Blue Streak was to act as a deterrent, so that if the UK were attacked with atomic weapons, it would have the ability to retaliate for a period of up to at least 24 hours after the initial attack, although there is no reason why this period could not be longer. The UK might not then be a functioning society any more apart from this one vital aspect – its ability to strike back at its attacker. That was the point of deterrence. But would the launchers in fact be capable of this? Some thought so, when the effect and accuracy of Russian missiles was being discussed. Thus, in a Ministry of Defence memo in June 1958:

This does not mean that a potential enemy attack with weapons achieving a c. e.p. of Vi mile would invalidate Blue Streak as a weapon. With a c. e.p. of Vi mile, one MT weapon delivered at each site would have a 50% probability of neutralizing a site. [This was an estimate based on the silo design and the known effects of nuclear explosions.] Thus to achieve an acceptable probability of destroying our retaliatory capability, a much higher ratio than one attack per site would be required; for example, more than 3 attacks per site would be required for a 90% probability and, if the reliability of the attacking weapons system is, say, 70% then more than 4 launchings against each target would be required. Alternatively, to give a 90% probability of putting a Blue Streak site out of action with 1MT delivered, a c. e.p. of

V mile would be required and again additional launches would be needed to offset the inevitable less-than-100% reliability. [c. e.p. is circular error probability; the chance of 50% of missiles arriving within this radius.]

A paper prepared in 1959 gives some idea of the projected costs:

The Ministry of Supply estimate that the total R&D cost of a below-ground Blue Streak would be £160-£200M, broken down as follows:

Underground Deployment

100 sites at £2M per site £200M

100 missiles at £0.5M per missile £ 50M

10 years operating costs at £0.125M per missile per year £125M

R&D £160-£200M

Warheads £100M

Total £635-675M

Even with only 60 missiles deployed, which would have been the probable final total, these are impressive sums for 1959. But they were only estimates, based on no hard data, and the history of such projects made it very clear to everyone except the Ministry of Supply that all such estimates were usually wild underestimates. The Treasury, of course, was more cautious: in January 1958 it gave authority to start work on Australian facilities. However, it went on ominously, ‘commitments on the part of the launchers related to “below ground” aspect are to be kept to a bare minimum and no work should begin on the “below ground” part of the launchers themselves.’9

Air Vice Marshall Kyle, Assistant Chief of Air Staff (OR), had to write to the Treasury:

At our meeting on Monday, 21st April [1958], in the Ministry of Defence, the requirement for underground launching for Blue Streak was queried and I confirmed then that this was the firm intention of the Air Council. From the attached note you will see that this has been made plain for well over a year and that the need for underground siting was envisaged in the original O. R. for the missile.10

Similarly, the Ministry of Supply argued that the idea of underground siting had been outlined in the 1958 Defence White Paper. The Treasury dismissed this by saying: ‘… the Treasury would never accept that a unilateral statement in a Defence White Paper committed the Government to any particular policy.’ One does wonder then what the point of a Defence White Paper was. The idea that a Defence White Paper would be published without having been cleared by the Prime Minister is more than a little absurd.

In Australia, a U tube launcher was to be built in the side of a ravine to avoid unnecessary excavations. A similar idea was pursued at Spadeadam, where English Heritage has recently investigated the site:

A letter from the Ministry of Supply to the Treasury shows that plans were well- advanced for the construction of an underground ground launcher at Spadeadam by September 1958. Trial bore holes had been drilled during the summer and permission was sought to begin the construction of a full size silo at a cost of £690,000, plus a 15 per cent agency fee. Owing to the proximity of the bedrock to the surface and the great expense (and time) that would be incurred excavating a hole 150 feet deep, it was planned to dig a 30 feet hole through the overburden down to the bedrock. The base of the silo would be placed in the hole while the remainder of the structure would be above ground. It was also proposed to place the missile silo hole close to the Greymare Hill Missile Test Area so that advantage could be taken of its technical infrastructure.

A contemporary air photograph taken in August 1961 confirms that work had begun on the silo. It shows an excavation with disturbed ground to its north and traces of heavy vehicle tracks leading westwards back towards the southern end of the Greymare Hill complex. Following the cancellation in April 1960, all major civil engineering work was halted, proving that this work had taken place prior to that date. Subsequent to the abandonment of the project, the silo trials area was covered by a dense coniferous plantation, effectively hiding the site from view for over forty years.11

In the UK, a full engineering prototype launcher was to be built, but finding a site for K11 and indeed for the rest of the silos was not easy. In June 1957 a list of 92 possible sites had been prepared, but only by looking at a map for disused Ministry of Defence properties. In a stroke of lateral thinking, more than 40 roadstone quarries were looked at for suitability: after all, there was already a hole there, and roadstone was good and hard. Geologically, the silos had to be sited in hard rock or other fairly rigid material such as chalk. By October 1958, there was talk of Duxford for the site of K11, with alternatives at Odiham, Waterbeach and Stradishall. By January 1959, Castle Camp, Ridgewell, Sudbury, Raydon and Lasham had made their way onto the list12.

Although there was talk of building clusters of six silos at a time, the sites had to be well separated by distance of several miles, so that one site would not be affected by attacks on other sites. But in February 1959, there was a change in policy: ‘the first sites should be in the South of England, North of the Thames’, and twelve disused airfields had been surveyed by March. These were Castle Camps in Cambridgeshire, Ridgewell in Essex, Tibenham and Hardwick in Norfolk, and Eye, Beccles, Sudbury, Metfield, Raydon, Bungay, Halesworth, and Horeham, all in Suffolk.

A problem emerged at Duxford, however: discovery of the water table 40 ft down and the resultant flow of water rendered it unsuitable13. Another site had to be chosen, and Upavon and Netheravon in Wiltshire were then earmarked for the job.

But now the Home Office intervened: they wanted the sites well away from any evacuation areas, and on the East Coast, so that fallout would be carried away by the prevailing winds. Upavon was dropped from the list of sites as a result. The 1959 election then intervened, holding up the progress, and after the election the emphasis changed: now the RAE was sent up to Yorkshire and Durham to look at the likes of Acklington and Eshott as locations for the K11 site. Similarly, the VCAS favoured Ouston or Morpeth.

Bircham Newton in Norfolk was also a strong contender, and the RAF went to investigate its geological suitability, as this memo from Wing Commander Wood indicates:

I had a long talk with the Station Commander Bircham Newton (Group Captain Walford) during my visit yesterday. He was rather upset about some of the unavoidable mess (mostly vehicle tracks) which the Soil Survey Team have made on the airfield as he is trying to have the whole place look spotless for a visit by C. A.S. [Chief of the Air Staff] on 16th October [1959] – I undertook to see that everything was tidied up. The Group Captain also asked for guidance should he be asked about the holes on the airfield which will still be evident.. .14

Once the deliberations of the BND(SG) began to leak out, progress became even slower. A memo from the Ministry of Aviation to the Ministry of Works in January 1960 contains the paragraph:

We are still not in a position to give you instructions to proceed on procurement for K.11 pending the completion of the current Defence review. There has been considerable correspondence at Ministerial level and it has been agreed that until the Defence review has been completed no new major commitments can be entered into on the Blue Streak project. Certainly K.11 is a ‘major new commitment’.

One thing was certain: by the time of cancellation no site had been fixed upon, no excavation had been started, the design was not complete and the chances of K11 being operational by 1964 were looking increasingly remote. [5]

3 TNA: PRO AVIA 92/18. Design of firing sites for ballistic missiles : policy.

4 TNA: PRO DEFE 7/2247. Development of Blue Streak.

5 TNA: PRO AIR 2/11115. Underground launcher: protective cover; design study.

6 Ibid.

7 TNA: PRO AIR 2/11131. Underground launcher: protective cover; design study.

8 TNA: PRO AVIA 92/19. Design of firing sites for ballistic missiles: policy.

9 TNA: PRO AVIA 92/18. Design of firing sites for ballistic missiles: policy.

DEFE 7/2245. Development of Blue Streak.

1 Cockcroft, W. (2006). ‘The Spadeadam Blue Streak Underground Launcher Facility U1’ Prospero 3 pp. 7-14.

12 TNA: PRO AIR 2 14701. Blue Streak: selection of sites.

13 Ibid.

14 Ibid.

Of the 22 Black Knight launches, two were proving flights and one was for ELDO, testing the range instrumentation. The remaining 19 were all for re-entry experiments. Initially, these were to test out the design of the re-entry, but soon they broadened out into a more general study of re-entry phenomena.

The first two flights were the proving flights; it was the third launch, BK04, which was the first to carry a separating re-entry head. This had thermocouples on the head to measure the temperatures at re-entry, the data being radioed back to the ground. Later re-entry vehicles would have a tape recorder to store the data – which was another good reason to ensure that the re-entry head was found after the flight. The data showed that the peak heating was similar to that predicted, and thus the design was now proved experimentally. There were other issues which could be explored in later flights.

After the early flights had verified the re-entry body design, the direction of the programme began to shift. Defence against ballistic missile attack seemed almost impossible, but there was now an opportunity to investigate whether such a defence might be possible. There was also another objective – to discover how best to make Britain’s missiles safe from an anti-ballistic missile defence.

The first few flights had shown some interesting phenomena. Firstly, that the exhaust plume from an ascending rocket gave a very strong radar response.1 There was the possibility of using this to detect enemy launches, although this would mean some form of over-the-horizon radar. Secondly, that the re-entry vehicle gave a very weak radar response – what today would be called ‘stealthy’. This tied in with work being done at RAE by the mathematician Grant Dawson, who was studying the radar response of the V bombers.

Ballistic missile defences have been divided into exo-atmospheric and endo – atmospheric – or, to put it more simply, intercepting the re-entry vehicle outside the atmosphere or once it had re-entered. In order to intercept the vehicle, it first had to be tracked. Radar was the only way of tracking the vehicle outside the atmosphere – and, as mentioned, the re-entry vehicle shape had a low radar cross section – particularly viewed from head on. It was also relatively easy to hide the re-entry vehicle within a host of decoys which gave similar radar responses.

Interception within the atmosphere has to be done within a very short space of time – certainly less than a minute. Again, one problem is how to discriminate between the re-entry vehicle and decoys. Thus further flights were planned, using optical instruments to observe the re-entry. These were the ‘Gaslight’ series of experiments. The results were sufficiently promising to lead on to a further set of experiments, Dazzle, with American participation. For these flights, the range at Woomera would be much more heavily instrumented.

Roy Dommett, who was involved in the Dazzle experiments, describes them thus:

The DAZZLE programme was sold to the Governments on the basis of exploiting the Blue Streak technology of a low radar observable profile, which was then an advanced concept for the west.

Chosen was the simple conical GW20 shape for which the UK already had derived an extensive experimental aerodynamic data base. The intention was to observe the re-entries of bodies with heat shields made in simple, reasonably well understood materials. Our agreed choices were fused silica, copper, PTFE (Teflon) and loaded durestos (an asbestos-phenolic composite).

For comparison there were to be two reference copper spheres flown. Their manufacture proved surprisingly difficult. The copper shapes were turned to shape by hand held tools in a workshop behind a garage in North London by men wearing armoured vests, and then had to be kept spotlessly clean to avoid sodium contamination. The PTFE was moulded from powder in large sections under pressure, which bulked down about 30% more than expected. ICI, the supplier, was very helpful as no one had ever made such big pieces before, and its final profile varied noticeably with the room temperature. Being PTFE, it was very difficult to machine. The silica glass sections were made in rough by a glass blowing firm in the north near Newcastle using sand moulds, and we had change from £100. The crud had to be machined off with diamond tools in F1E workshop at RAE where we discovered that glass stress relieved itself hours after it was touched. It could only be assembled by having layers of asbestos felt mat between every glass-glass and glass – metal interface.

The conical copper bodies were expected to fail at some point during re-entry by softening and distortion of the nose, but up to that time they would be clean and the observables would be entirely due to the interactions with the atmosphere unaffected by contamination from ablation products. It was thought that the PTFE would massively sublime at a much lower surface temperature than the silica and the products probably suppressing the flow observables, and that the durestos would ablate messily, enhancing them.

He also has this to say about the sabot system described in the previous chapter:

To be absolutely sure of the quality of the data, it was decided that the re-entry experiments should be pushed into the atmosphere ahead of the upper boost stage using a sabot that was firmly restrained by a lanyard to the upper boost stage, so that the experiment should have been several thousands of feet ahead of it during re­entry. The sabot was driven by four Imp solid propellent motors. In vacuum the plumes spread enormously, and the section of the tether near the sabot had to be in steel. Playing out the tether could exceed the critical speed for the undrawn nylon rope, chosen to avoid elastic bouncing around, and a very careful packing technique had to be found. Finally the rope still broke in flight quite early, despite extensive ground based testing, then it was eventually realised that nylon type plastics have “attached water molecules” which boil off in vacuum, cooling the rope and making it brittle. We also found it near impossible to get the re-entry vehicles to come in without a coning motion of the order of 20 degrees generated by the separation disturbances.