by Damien Burke
In November 1960 the Air Staff had drawn attention to an American RBW rocket then under development, and in October 1961, nothing further having been done in the interim, they asked the RAE to investigate this further. It was not until March 1962 that an RAE team visited the USA to assess the suitability of Revere Copper & Brass Inc’s RCU-2B Window-sowing rocket to contract QRC-142(T). This was designed to be fired at altitudes of around 50,000ft (15,000m) from Boeing B-52s travelling in a straight line, using twenty 2.5in folding-fin rockets carried in a pod under each wing. Each rocket would pull ahead of the launch vehicle and descend gently, exploding a sequence of Window units and thus laying a cloud that would begin ahead and below the launching vehicle and grow with further rockets, to try to seduce the enemy radar’s range gate into following the larger target of the Window cloud rather than the aircraft. Test carriage and rocket firing had also been trialled on Boeing B-47, North American F-100 and Lockheed F-104 aircraft, using an existing high-speed ALE9 pod, which alleviated most of the RAE’s worries of the susceptibility of the rocket to high-speed carriage and firing during manoeuvres, though some components would need to be replaced to cope with the sustained high temperatures of supersonic flight.
Meanwhile, BAC had continued working on the dorsal idea, and by November 1962 had come up with a dorsal ‘fin’, much smaller than the previously suggested installation, which would fire window cartridges sideways and upwards. The Air Staff were still not impressed, and in December, having looked at the RAE’s study on the American rocket, pushed once again for a complete design study into suitable RBW/ infrared decoy (IRD) dispensers, including carriage of a suitable rocket. Accordingly, a contract was awarded to Microcell to carry out a design study for a suitable countermeasures launcher to be pylon-mounted. Completed in June 1963, Microcell’s design study proposed an impressive variety of dispensers, with and without forward-firing Window rockets in addition to the launch of both RBW and IRD cartridges. Standardized RBW and IRD cartridges were already under development to RRE specifications, of 2.25in diameter and 5.3in long. The operational requirement for these dispensers was that they should be suitable for carriage on both port and starboard outer stores pylons over the aircraft’s full flight and temperature envelopes, capable of jettison, and carry as many cartridges as possible; a minimum of 100 for an RBW/IRDonly dispenser. Spent cartridge cases were to be retained within the dispenser after ejection of their payload. A variety of firing combinations was to be provided, and counters in the cockpits provided to show the remaining capacity of each type of cartridge. Window rockets, if chosen, would be fired singly at crew command, but RBW/IRD cartridges were to be capable of both manual and automatic firing in conjunction with the aircraft’s missile warning system.
The various RBW dispenser proposals made by Microcell in April 1962. Eventually the pylon-mounted pod became be the favoured solution. Damien Burke
By mid-1963 Microcell had completed a formal design study into a variety of pylon-mounted countermeasures pods. This illustration shows a TSR2 rolling into a nuclear dive attack, firing Window rockets on the way. BAE Systems via Warton Heritage Group
Microcell’s first proposal was for a slab-sided dispenser, pylon-mounted of course, firing RBW/IRD either to the side (and slightly downward to avoid the down-turned wingtips), or an alternative version that fired downwards. The latter would ease the positioning of different cartridge types within the dispenser, as side loads on the pylon were a limiting factor, and simultaneous ejection of the heavier IR decoys would require that IRD cartridges were concentrated near the pylon centre for a sideways-firing dispenser. The obvious problem with the downward-firing version was that at low level any cartridge contents would hit the ground in very short order, after less than half a second if the aircraft was flying at 50ft (15m). To avoid this, Microcell suggested an overwing fit, but this would need the addition of overwing hardpoints, and perhaps the addition of rear fins to the dispenser to aid clean separation if jettisoned.
Two of Microcell’s countermeasures pod designs. The upper one was a combination pod with forward-firing chaff rockets and sideways-firing chaff and flare cartridges; the lower design was a simpler one using only sideways-firing chaff and flare cartridges. BAE Systems via Warton Heritage Group
The final choice of countermeasures pod selected by BAC was this one, based on the simpler Microcell design. It was submitted to the MoA in late 1964. Damien Burke
The second proposal was for a dispenser that included forward-firing Window rockets. No suitable British rocket was then available, and one suggestion was to use the QRC-142 rocket that the RAE had been studying. The length of these rockets, and others suggested, would mean that the cartridge capacity of the dispenser would need to be reduced to a total of forty-two cartridges, and the low frontal area required for the dispenser would limit the number of forward-firing rockets, to just sixteen of the 2.75in-diameter QRC-142 rockets, or up to twenty-six if a suitable 2in-diameter rocket could be developed. With the rear of the dispenser taken up by the cartridges, rocket exhaust would be directed via a downward curving duct to a spring-loaded flap on the underside, or possibly through exhaust stacks directed to the sides, though this would require a longer dispenser.
While the American QRC-142 system went on to be developed successfully into the ADR-8 rocket fired from AN/ALE25 pods fitted to all B-52G/H models from 1964 onwards, interest in its use for the TSR2 evaporated, and BAC Warton went on to produce a design study of its own, based on the Microcell proposal for a side-wards-firing RBW/IRD dispenser. BAC’s pylon-mounted RBW/IRD dispensers were a minor variation on the Microcell design, similarly accepting existing 2.25in-diameter and 5.3in-long cartridges in an internal matrix. Each dispenser had room for 108 cartridges (72 RBW, 36 IRD, or all RBW if preferred), slightly more than the Microcell version. As the dispensers would be around 10ft (3m) off the ground when loaded on the pylon, the loading of cartridges would be carried out before hoisting the dispenser up to the pylon, and no special hoisting equipment would be required over and above the equipment already accepted as being required for TSR2 use. Existing pylon connections needed only a small modification to accept a seven-pin electrical connection rather than the existing three-pin connection, and the dispenser pod would be canted 7.5 degrees downwards to ensure that the fired cartridges cleared the wingtip.
A BAC advertisement of 1963. BAE Systems via Brooklands Museum
Control of dispenser firing would be the navigator’s job, and he would be able to fire cartridges in various permutations and intervals. Counters showing the remaining content of each dispenser would be present on the navigator’s panel, along with firing and sequencing controls. In terms of aircraft performance the RBW/IRD dispensers would have a slight negative effect on transonic longitudinal stability and introduce a fuel penalty of approximately 1,870lb (850kg) on the standard 1,000nm sortie. Trials using a Scimitar with a basic RBW dispenser in late summer 1964 were less than encouraging, and by January 1965 the requirement for such a dispenser had been suspended and work ceased ‘for the time being’. It was not restarted before the project was cancelled.
Active decoys and jammers
As well as RBW and IRD, OR.343 had required the carriage of an active decoy system. The idea here was that some kind of rocket would be fired with a radar reflection area similar to that of the aircraft, and perhaps carrying a noise jammer. Fairey Aviation had looked at using its Fireflash missile as the basis for such a decoy missile, to be used on the NA.39 on the final approach to a naval target. Such a decoy could conceivably have a large enough frontal radar cross-section (RCS) at least to cause confusion to the enemy radars tracking the incoming aircraft, but the TSR2’s overland role was entirely different. Radars could be anywhere alongside the aircraft’s path, not just at the end, so a decoy’s RCS needed to be large enough to duplicate the aircraft’s RCS from any aspect. Such a decoy would be so large as to introduce weight and carriage problems of its own, and in the end the NA.39 never use
d such a system either. One finding from the NA.39 studies was that Plessey had an experimental jammer that could run for about 10min on battery power, and this was felt to be more likely to be useful than a simple radar reflector decoy. Such jammers could be carried within the bomb bay, occupying space forward of the nuclear store, or in wingtip pods. Firing would be automatic during the loft manoeuvre, or when a radar acquisition turned into a radar lock. The biggest problem with this was that the aircraft presented its largest echoing area to any ground-based defence systems during the loft manoeuvre, so any decoy or jammer would have to be excessively large and powerful to be of any use. The problems mounted up rapidly, and as a result the requirement for the carriage of decoys and/or jammers was deleted from OR343 in August 1961.
Little information on other possible active ECM equipment for the TSR2 has come to light. Studies to Naval/Air Staff Targets 830 (jammer), 836 (towed decoy), 837 (combined pod to include jammer, towed decoy, chaff and flares) and 841 (draft for a passive-warning IR detector) were all under way at the time of cancellation, and these are mentioned in the context of TSR2 subsystems being still required after cancellation. However, these were all general requirements applicable to all tactical aircraft, very much theoretical studies rather than real projects, and no particular work appears to have taken place to link these to the TSR2 specifically, certainly not at the BAC end of things at least. Given that active ECM had been deleted from the requirement, this is unsurprising. None of the studies resulted in real hardware, and some years later the RAF would buy American ALQ-101 ECM pods instead.
Radar camouflage
The airframe had been designed to give minimum possible radar echoing area in the head-on aspect, particularly in the X-band, and as a result flat, forward-facing bulkheads were kept to a minimum and the engine compressor faces were partly hidden from direct forward view by long, twisted intake tunnels. The intake tunnels, while hiding the engines nicely, were a source of considerable reflection themselves, and the thermal and structural loads to which they were subject precluded the application of radar-absorbing material (RAM) to them. Thus the intakes provided approximately 60 per cent of the total frontal RCS of 20m2. In 1960 RAM was in its very early days, and the most crucial areas requiring camouflage were also those to which it would be most challenging to apply any such materials: the intake ducts and lips. The temperatures and structural distortions experienced in the intakes were sufficient to break off any currently available material, whether it was used as an additional application to the basic structure or formed the structure itself, and send it flying into the engines with possibly catastrophic results. No solution was found to this problem, and in March 1960 the Air Staff agreed that no radar absorbing material should be applied to the intakes. It was suggested that research should begin on the creation of a suitable high-temperature and high-strength RAM for future use on other aircraft, and for application to the TSR2 as an in-service upgrade.
The cockpit area’s radar reflectivity was one area that could be dealt with. Metallized glass in cockpit transparencies was a known method of reducing radar echoes from the cockpit area, and this dovetailed nicely with the gold film heating/ demisting system created by Triplex. No additional work was necessary. No figures have yet come to light on the resulting RCS reduction. By February 1963 RAM technology had moved on, and research had found that very thin metallic films, such as copper oxide paint mixed with resin, gave promising results in radar-absorbency trials. Vickers wrote to the Air Staff requesting views on this, and whether it could result in a reversal of the decision not to use radar camouflage on the intakes. If so, however, additional budgetary cover would be required. By late 1964 the subject was still coming up occasionally, but no firm decisions appear to have been made before the project was cancelled.
Gold film inlaid in the cockpit transparencies for heating and demisting purposes had the bonus of reducing the radar cross-section of the cockpit area. Damien Burke
CHAPTER NINE
Weapons
Weapons delivery and accuracy
The aircraft’s primary mission, that of delivering a tactical nuclear weapon, was, using existing tactics, also its most dangerous. The then-current means of attack, for which Red Beard’s fuzing system had been designed, was to use LABS, which described a selection of manoeuvres, all variations on a common theme known as ‘loft bombing’ or ‘toss bombing’. Rather than the classic bomb runs of the Second World War, in which the aircraft flew in a straight line over the target, releasing its bombs when the target was centred in the bombsight (level bombing), loft bombing entailed the aircraft effectively throwing a bomb in the manner of an underhand bowl. This was accomplished by pulling up into a hard climb (commonly 3 to 4g) and releasing the bomb at a preset angle (typically 45 degrees) that would give the best ‘throw’ distance). The aircraft would continue the pull-up, describing half a loop before rolling wings-level and escaping in the direction from which it came. The bomb would initially continue upwards too, but would describe a parabola back to earth, hopefully arriving on the target or at least very close by. The advantages of this delivery method were that the aircraft did not need to enter the immediate area of the target at any time, and thus kept considerable distance between itself and the atomic explosion. However, this manoeuvre also threw away the low-level interdictor’s primary means of protection, staying at low altitude. A typical loft-bombing attack could result in the aircraft gaining as much as 12,000ft (3,600m) in altitude during the manoeuvre, which left it extremely vulnerable to SAMs or fighter attack.
The Circular Error Probable (CEP) of a selection of nuclear delivery modes. Given a big enough bomb, of course, CEPs measured in hundreds of yards were effectively irrelevant. BAE Systems via Brooklands Museum
The RAE suggested a variation on this attack, in which the release angle was restricted to just 10 degrees and the aircraft terminated the climb immediately after release, rolling left or right to pull hard away from the target. The height gain would be much less, perhaps just 1,500ft (460m), and the aircraft would retain more speed and energy. However, the bomb would arrive on the target much quicker and would therefore need a delay mechanism to allow the aircraft to escape to a safe distance before the explosion. This also meant the bomb itself had to be tough enough to survive the initial impact without destroying the fusing system and disrupting the structure of the ‘physics package’ that made up the warhead.
An alternative means of attack was the dive toss, in which the aircraft approached the target at a higher altitude and then started a dive, releasing the weapon in the dive and then pulling out to escape. This, however, was even more dangerous than loft bombing, because the aircraft was exposed to detection for a much longer period. By late 1962 the requirement for a blind dive-toss attack was removed. However, a lay-down attack was now introduced, for both low-level and medium-level delivery.
Releasing bombs at low level also presented problems. The classic ‘lay-down’ attack, if performed at 200ft (60m), would result in the aircraft being damaged or destroyed by the explosion (certainly destroyed if the bomb was a nuclear one). Release would need to be from 400ft (120m) for conventional weapons, exposing the aircraft to defences, or a new type of bomb would have to be designed. Retarded bombs, using pop-out fins or parachutes to slow their descent, were being worked on elsewhere, but the Air Staff had already decided to save money on TSR2 by not requiring the design of any new conventional weapons, so their applicability was doubtful at the beginning of the project.
The answer to both sets of problems was the adoption of a stand-off weapon, a missile, that could be released some distance from the target and make its own way over the remaining distance. An Air Staff Target (AST.1168) was already in existence calling for an air-to-surface missile (ASM) that could be launched in blind conditions from low level, along with an Operational Requirement, OR.1173, for a nuclear-armed, visually aimed ASM, based on the characteristics of the American Bullpup missile. Although AST.1168 eve
ntually resulted in the Martel missile, OR.1173 ended up being cancelled.
Visual sighting was always going to be a problem for TSR2 crews. The thick windscreen and surrounding metalwork provided poor view quality in the most important directions, and trials with a Hawker P.1109 (Hunter variant) with a mocked-up TSR2 windscreen had found that vision angles were inadequate for visual identification of targets of opportunity. The use of visually guided missiles such as the Bullpup or AS.30 would have been severely limited by their minimum launch ranges being some distance away from the point at which the TSR2’s crew would actually be able to identify the targets.
Some of the attack methods originally envisaged for use by the TSR2. Computer capacity problems later resulted in the RAF having to make difficult decisions about which delivery methods it absolutely could not do without. Damien Burke