Black Knight

The Black Knight programme was an importance milestone in evolving space launch vehicle technology for Britain.

 

A CONTRACTOR’S VIEW OF THE BLACK KNIGHT PROGRAMME

  1. SCRAGG Manager of Space Programmes, Westland Aerospace Ltd, East Cowes, Isle of Wight.

 The Black Knight programme was an importance milestone in evolving space launch vehicle technology for Britain. It demonstrated how members of different commercial concerns can work together as a team for the benefit of the project. The total cost of the project has not been declared but it is believed to be significantly lower than the equivalent costs being quoted currently for some launch vehicle developments.

  1. THE NATIONAL OUTLOOK IN THE MID 1950’S The Government of the day had published its considered decision to rely on short and long range missiles to provide the defence of Britain, thereby consigning its fighter and bomber squadrons to the scrapheap. There was little knowledge available on the dynamics of re-entering warheads launched by ICBM‘s and so the Government initiated the Black Knight programme to study these effects. Saunders Roe Ltd, as we were then known, were invited to contribute, to this programme, the knowledge gained on their mixed power plant interceptor fighter, SR53. This fighter used a conventional gas turbine engine for cruise and loiter, but was able to switch in a Hydrogen Peroxide/Kerosene rocket engine for high speed take-off and in-flight diversion. The knowledge on the design of tanks and handling of concentrated hydrogen peroxide, a very reactive liquid, was to become, for Westland, an important read-across from the fighter project. Aircraft manufacturing companies in the l950’s were predominantly working on military aircraft for UK defence. The Duncan Sandys pronouncement caused a major rethink on the direction that companies would hike and therefore a number of firms who already had been working on missiles could lend their expertise to the new defense requirements. This decision by the government would, in the future, be seen to have encouraged UK industry to be among the world’s leaders in space technology. It was against this background, then, that RAE Farnborough, the government programme managers, established a team of industrial contractors to define and run the Black Knight research programme.
  1. FORMULATION OF THE BK TEAM RPD Westcott had been developing the HTP/Kerosene Gamma motors and worked closely with Armstrong Siddeley to establish production and test facilities. The remainder of the launch vehicle was awarded to Saunders-Roe who, working closely with RAE Space Department assembled a team of suppliers for the vehicle systems. This team included

Reid and Siegrist – gyros  

Elliott tracking – transponders

EMI – telemetry transmitters

BAJ – air bottles

Hymatic – mechanical components                 

Laporte Chemicals – hydrogen peroxide

Hobson – servo actuators

 The vehicle structure, motor control system, electrical and mechanical systems were undertaken by Saunders-Roe. Saunders-Roe had designed and manufactured its own analogue computer. This computer was used throughout the Black Knight programme for theoretical trajectory prediction for each individual launch vehicle and, in the early design phase, for modelling the engine control system, to derive the gain changes required during flight to de-sensitise the system. A breadboard inner control loop was connected to the computer and measurements taken. This tool was to be invaluable during the early development phase, when computer models were refined to include vehicle measurements. This useful design tool was again used to explore any problems in the updated transistorised system. The vehicle was to be launched from the Woomera Test Site in South Australia as part of the UK/Australian Joint Project. Concurrent with the evolution of vehicle philosophy, it was necessary to address the ground infrastructure requirements. A broad strategy of development, testing and operation was evolving and this strategy would require an engine test bed at Ansty, the High Down static test site at the western end of the Isle of Wight and a full launch site at Woomera. The static test site would reproduce the launch site in all respects except actual release, while motor operation would be restricted to 35 sec instead of the full flight operation of 120 sec. In 1955, Saunders-Roe began to assemble its team under the then Chief Designer, Maurice Brennan. The choice of a site for the static tests on the Isle of Wight was undertaken and a number of such sites considered. The site offering most advantages because of its topography was the old military installation at the western end of the island, above The Needles. A firm of architects, John Strube was retained for overall design of the road system and conversion of existing but long unused military installations while the detailed design of the facilities was undertaken by the SR works engineer. The necessary control and monitoring equipment for the vehicle operation was to become a natural extension of the various vehicle systems design. This infrastructure concept was then applied to the Woomera launch site. Minor changes to the High Down concept were necessary, at Woomera, to only two main elements firstly the servicing tower had to be withdrawn for launch and secondly the hold-down fixture, the release jack, required an operating system. These were to be the only two features not checked during acceptance testing at High Down. At that time, some 3000 people were employed at Saunders Roe on various aircraft projects including the mixed power plant fighter. Over the next 3 years this level of employees had to be drastically reduced as aircraft programmes were cancelled for one reason or another. This was of benefit to the Black Knight programme as it released designers with the requisite knowledge. The Design Office team comprised a number of young and enthusiastic engineers, guided by mature engineers like Alec Prickett, Len Summers and Wally Peters. Bert Lloyd undertook the project manager’s job of co-ordinating the activities between RAE, contractors and the Design Office. As part of this design organisation, a development department was created, under the leadership of Paul Leyton, to staff and undertake the static testing at High Down and then to take the vehicle to Woomera and launch it. The Government, wishing to make maximum use of this research vehicle, ordained that the launch crew at Woomera would be provided by the de Havilland company, who were to be responsible for launching Blue Streak and would therefore get “hands-on” knowledge of launch disciplines. Many long and frank discussions took place between Saunders-Roe and the Government on what was seen by the company as a high risk, when de Havilland had not been involved in the design and Blue Streak was a totally different concept. The government, being the customer, won the day. With the benefit of hindsight, this teaming arrangement proved invaluable to Saunders-Roe, in later years, in learning and understanding how to co-operate with companies who could be considered competitors. There were to be numerous occasions in the programme when this frustration nearly surfaced but, in every instance, the need to complete the task became paramount and team harmony was continued. These small incidents reinforced the pride of those working in the programme, who felt they were pushing forward the technology and maintaining Britain’s place in the space field. The launch team consisted of members from the Australian Weapons Research Establishment who controlled the central range facilities and launcher safety, de Havilland, RAE, Saunders-Roe and Armstrong Siddeley.

  1. DESIGN AND MANUFACTURE CHALLENGES The vehicle structure had to be stable without internal pressurisation. (The Blue Streak oxidant tank, for instance, had to be pressurised at all times, to prevent collapse.) The challenge here for BK was to establish a manufacturing technique consistent with strength and liquid tightness. The initial tank concept was skin and welded stringer and the first two prototypes were so built. This proved to be an uneconomic and unreliable type structure. The final design used a thicker skin with internal support frames. In the mean time, development work, in partnership with Sciaky, was being carried out on a spot welder which was being modified to weld at spot radius pitch. In this way, a welded seam was produced which was strong and leak proof. In fact, for added assurance most seams had two lines of weld. Initial design of the motor control system used thermionic valves for the amplifiers and other “black boxes”. Transistor design was not sufficiently far advanced to have confidence in their reliability. This was to come later in the programme when transistorised control systems were introduced into the uprated vehicle configuration. The operating environment demanded ruggedised valves and at the outset, there were fears over whether the system would survive the harsh vehicle environment. In the event, the fears were groundless. It had been agreed that the final two minutes of the launch countdown would be fully automatic, the only manual intervention being an ability to stop the sequence. This decision demanded an interlock system which inhibited a subsequent command when the preceding event did not occur. The effect on the vehicle was minimised by introducing banks of interlocking relays on the ground, being fed from monitoring systems on the vehicle.

4. DEVELOPMENT CHALLENGES Civil contractors moved on to the static test site in April 1956 and the first challenge was to achieve the first vehicle motor firing one year later. This event was achieved, albeit by cutting a few corners. The vehicle oxidant tank of the first prototype was not leak proof and so alternative feed arrangements to the motors were made. An external tank was installed outside the servicing tower and a feed line direct to the engine installed. The first firing was not completely successful because only sufficient oxidant for a 35 sec firing was loaded and at the end of this period a vortex in the tank produced uneven combustion. For subsequent firings, the tank was filled, overcoming this problem. The second prototype was the first complete vehicle although the tank construction was not to the final standard. This vehicle was used extensively to develop the motor and guidance control systems. Day after day, the development work continued to search out all the “bugs” there might be in the system. In fact the days often stretched into nights over a period of some 15 months. During this period, the storeman gained a reputation for his alfresco meals (hot soup and bread, pies etc!!) It was not unusual to arrive home at 2 a.m. and be back at work at 7. In fact static firings were a blessing for all but the poor old mechanical engineer, because the tanks and motors required a 16 hour dry out period and the drying machine was a high speed, screaming compressor. It was impossible to work with this machine in operation! The stability of the control system was suspect in these early days. The original gyros suffered from excessive drift rates and continual exercising of the motors induced wear into the trunnions, which had to be changed. However, the control system was modified and improved during this development phase and the later success of all vehicles in the programme showed the value of this intensive work. Development work sometimes demands a return to basics. In the early days, there was often conflict between two or more sources of information on the performance of the motors during the static firings. One such example was the amount of HTP and A Contractor’: View of the Black Knight Programme Kerosene used to establish that the engine mixture ratio had been properly set. The quantity of kerosene used had to be known quite accurately. Various instrumentation systems were tried but we discovered there was no better substitute that weighing the quantity into the tank and weighing the residue! Eventually the on-board instrumentation was developed to give an acceptable accuracy. One problem which never went away was RF interference on to firing circuit lines. Two ostensibly identical vehicle modules would not show the same resistance to interference. Each flight vehicle was individually tested to prove that RF interference was at a low enough level not to initiate the firing circuits. The solutions to the problem areas in the ground system at High Down had been transmitted to the Australian site. Thus, when the first static firing was undertaken there was comparatively little modifications required. The early launches, similarly, did not require the large elements of development that had been undertaken at High Down. The early launches in the programme had proven that recent dynamics theory was correct and there was now a requirement to increase the re-entry velocity. This was to be achieved by fitting a solid motor on top of Black Knight with the head mounted inside the vehicle, pointing downwards. The top end of the solid motor (the exit nozzle) was modified to contain a pressurised gas bottle which separated and spun the motor and head. This modification increased the firing circuits and, incidentally, the RF interference checks. BK16 introduced the uprated and improved two stage launch vehicle. The Gamma 301 motor was introduced providing a 25% increase in thrust. The release jack was modified to retract after operating, the control system was transistorised and these changes led to a second development phase. The water cooling flow in the effeux ducts did not have to be increased and the Control System was found to be more efficient. The development period could be considered uneventful when compared to me prototype work.

  1. OPERATIONAL CHALLENGES Each flight vehicle was subjected to a final acceptance inspection in the workshops prior to sending it to the static test site. When it arrived, the Development Team checked the critical electric circuits and the control systems equipment to prove that no damage had been sustained in transit. As with any component, there were minor discrepancies and reference to the factory inspectors always produced the same reply “it was OK when it left here”. There were a few occasions when we felt that answer to be suspicious but could not be disproved, until the day arrived when the connector plug to the air system solenoid valve literally fell off when the access door was removed. The wires had not been soldered! The answer to the question was the same! In fact these little interchanges only served to cement the team spirit, as each side gained respect for the other and the quality of product was preserved. The testing routine of each flight vehicle at High Down was deliberately chosen to follow that which would be employed at Woomera but would, in certain tests, cover more parameters. It became clear at an early stage that the test procedures should be the same at both High Down and Woomera. Thus Contractors Standard Procedures (CSP’s) were born. As the research programme developed, so the information in the CSP’s was refined and even expanded. This produced the effect that the last vehicles in the programme were more comprehensively tested in the same timescale than the early vehicles. I am confident that this was one of the important factors which ensured the programme was successful. When the vehicle arrived at Woomera after 6 weeks at sea, it went through a similar reception routine to that at High Down. The Saunders-Roe team, by this time, had got to know the vehicle as you would know your car. This knowledge was shared with other team members during the reception inspection. It would be here in the reception area that the team would see the head for the first time. At this time in the launch sequence, work was fairly pedestrian and it was unusual to work extended hours. This then gave the “visitors” the opportunity to renew friendships with the “residents”, especially in the Mess in the evenings! It may seem paradoxical that these early evening were fairly sedentary affairs whereas the social evenings, later in trial, were as active as the days had been! The preparation of some of the early vehicles had to be extended when the systems, particularly the control system, did not seem to be working properly. In these early days, spare components were not plentiful and on one particular trial, we had to plead for permission to open up a gyro to correct an interlock. This operation would not normally be considered but when you have no serviceable spares, you are working toward a launch slot that cannot be missed; you take whatever action is best in the circumstances. In the event, the fault was corrected and the mission was totally successful. The first two surge vehicle that I referred to earlier, BK08, has impressed itself on our memory not only for that reason but also that it was the only vehicle to complete the launch Sequence, including opening the release jack, but not take off. The motor shutdown at the same instant the release jack opened and the vehicle remained balanced on the wind brace arms. However secure you believe your safety system to be, you can always find an exception! During the preparation of one of the later up-rated vehicles, the launch site and the Woomera village itself was attacked by a dust storm. All wind strength instruments went off-scale showing velocities in excess of 120 mph. Roofs in the village were ripped off but the only effect on this Black Knight was a thick layer of dust which took a day or so to remove. The filling of vehicle tanks with HTP, just a few hours before launch or static firing, had to be undertaken in protective suits. These suits had to be impervious and even on a cold UK day, the occupant could work up a reasonable sweat. Imagine then the conditions at Woomera with ambient temperatures up to 40°C. Much better than a sauna for trimming away excess fat!

6. CONCLUSION From a contractor’s point of view, the programme demanded fresh approaches to some of the technical challenges and eventually used the technology to develop an all British satellite launch vehicle. One spin-off, so far as Saunders-Roe was concerned, of quality assurance in our current products has been evolved from the Black Knight days. To end on a slight sad note, we regret the inability to capitalise on the advances made through the 50’s and 60’s more especially when you look at the world market for launch vehicles.