Winds of Destruction

by Peter John Hornby Petter-Bowyer

  Being streamlined, bombs descend directly under the delivering aircraft until they have fallen some 2,000 feet clear. Thereafter drag and the progressive nose-down pitch cause bombs to slowly trail behind the bomber. But a safe separation height can never be less than 2,000 feet to avoid damage, and even destruction, from large weapons detonating directly below the delivering aircraft.

  This photograph shows a total of seventeen 500-pound bombs dropped by three Canberras. Note the huge gaps of ‘safe ground’ between the strikes.

  In our case this meant that, for accuracy to be assured, the Canberras would have to pass over target in perfect range of missiles and guns. The alternative was to bomb from great height and accept both loss of accuracy and the fact that cloud could limit windows of opportunity for strikes. Neither of these situations was acceptable. Another unacceptable issue, no matter the bombing height, was that large gaps in a string of bombs left too much ground uncovered.

  An inherent problem with conventional bomb design is the need for tail cones and stabiliser fins that are costly and occupy potentially useful space in a bomb bay. Spherical bombs are quite different. They do not poses wasteful appendages, nor do they suffer orientation problems. A spherical bomb bursting above ground will consistently deliver shrapnel through 360 degrees in all directions but always lose half into the air.

  Delivered in clusters, spherical bomblets moving through air at high speed create high-turbulence wakes that induces lateral movement to following bomblets. Moreover, high drag on every bomblet causes rapid deceleration from the moment of release. Another important advantage is the natural tendency of round bombs striking the ground at shallow angles to skip back into flight, making airburst possible. Admiral Nelson used this principle to good effect against enemy ships by skipping round cannon shell off water to improve the chance of gaining waterline damage.

  Having understood these explanations, Denzil and Bev were eager to assist us develop a spherical cluster-bomb system for Canberras because it was agreed that such a system was within the technical competence and capacity of the company. Denzil kindly undertook the initial research work at his company’s expense and I opened a project file marked ‘Project Alpha’. Projects that followed were Projects Bravo, Charlie, Delta, etc.

  Bev considered it necessary to use a central spherical bombcore fashioned from 8mm steel plate to house the explosive charge and a multi-directional delay-fuse. This fuse would initiate a pyrotechnic delaytrain and without regard to the orientation of a bomblet when it struck ground. The central core was to be encased within a larger 3mm steel sphere with many super-rubber balls tightly packed between the inner and outer casing.

  The purpose of super-rubber balls was to allow the inner core to compress them on impact with ground, thereby creating a latent energy source that would enhance a round bomblet’s natural tendency to bounce into flight. At the time we did not see that the rubber interface would be giving bomblets vitally important secondary characteristics. One was an inherent ability to absorb sharp shock loads on the fuse if a bomblet was inadvertently dropped onto concrete during handling and loading.

  A variety of tests were conducted to prove prototype bomblets’ ability to recover off ground even when dropped vertically from a helicopter at great height. When we were certain we had a worthwhile project on our hands, I went to the Air Force Commander’s office late one afternoon with an eight-inch bomblet in my hands.

  Having explained the design, I held the ball at waist height and asked Air Marshal McLaren to watch how the bomb recovered into the air after impacting the ground, whereupon I released the ball onto his office carpet. His reaction to the metallic clang was not what I expected and I do not think he even noticed the bounce. “Get that confounded object out of this office. You have six weeks in which to produce your system for full load strikes by four Canberras.” I was astounded by such a quick decision and said, “Sir, there is no money budgeted to meet your instruction!”

  Mick McLaren was known for his ability to come to quick decisions. His reply was typical. “You concern yourself with technical matters and I will take care of the money. I am counting on you for success. You have six weeks to do the job, so get cracking!”

  Schematic diagram of the Alpha bomb.

  Air Marshal McLaren was the first Air Force Commander not to have serviced in WWll, so he had a flexible attitude towards weapons in general. He had studied every ASR and had called for detailed post-operational studies of Canberra bombing effects following a number of strikes in a variety of bush conditions. I was not involved in any of these studies but had read every report. None that he received gave the Commander any reason to be satisfied with cylindrical bomb efficiency. Without him actually admitting it, he agreed with what I had been saying for many months and obviously liked the spherical bomblet concept as the means by which to make his Canberra fleet effective. I suspect that Group Captain Norman Walsh may have had a hand in influencing the Commander’s opinion on the need for a cluster-bomb system.

  I made a telephone call to Denzil and told him we had ‘green light’ on the Alpha Project and that Ron and I would be around to see him immediately. Denzil and Bev were waiting for us in the company boardroom together with the company’s accountant and a third engineer. Our excitement was somewhat tempered by the realisation that a project of this nature, if undertaken in the USA, would require many millions of dollars, involve many engineers and would take no less than five years to complete.

  With only six weeks to finalise research and development and produce four complete carriage and release systems along with hundreds of bomblets, it was obvious we had to make final but correct decisions right away. Denzil did some preliminary calculations that made it clear that cutting of metal had to start next day. In turn this meant we had to finalise the specific dimensions of both inner and outer casings at this very meeting so that preparation for half-sphere presses could be initiated that night.

  Canberra bomb-bay drawings were spread out on the boardroom table to confirm preliminary designs generated during our earlier work. I had to specify the number of bomblets in a single load so that Denzil and Bev could calculate final bomblet dimensions. For convenience we had already started referring to the bomblets as Alpha bombs (Project Alpha) and I gave the operational requirement as 400 Alpha bombs to be released from eight independent containers, which we named ‘hoppers’.

  The engineers quickly sketched profiles of four units comprising two hoppers each to establish the internal volume of each hopper. Having done this, they established that the external diameter of each Alpha bomb would be 155mm. From this the size of the rubber balls and inner bomb core were also determined.

  The very next day preparations were in hand to press the metal blanks into half spheres. By Day Three the welding of half-spheres for inner cores and outer casings was already under way. The first hundred outer casings were taken off-line and filled with concrete for initial proving trials.

  At New Sarum Warrant Officer John Cubbitt had his Drawing Office staff busy finalising the hoppers design and within two days Station Workshops were fabricating prototypes for preliminary drop trials of the concrete-flled Alpha bomblets. The concrete units approximated very closely to the calculated final weight of explosive ones.

  At my insistence flight trials commenced with the fitment of a camera into a Canberra bomb bay to record the release characteristics of the old 28-pound bombs from the ‘bomb box’ unit. The bombs we used were practice units that had the same shape and ballistic characteristics as live ones. Two full-load tests of ninety-six bombs each were made. In addition to the bomb-bay camera, each drop trial was filmed from a formating Vampire.

  What we saw was very disturbing. Bombs exiting the bomb box into the very high turbulent airflow, particularly at the rear of the bomb bay, gyrated, tumbled and jostled with each other. Some bombs were even blown back into their compartments before emerging again to join other wildly twirling and twisting bombs. Why film recordings
such as these had not been made and studied previously, I cannot say; but it made us realise that the Board of inquiry into the Canberra disaster had not come up with the correct reason for the premature detonation that destroyed the Canberra.

  First drop tests of the Alpha bombs were recorded in the same way and we were delighted to see how cleanly they dropped away and how rapidly they spread out and trailed back from the aircraft. Because the concrete Alphas suffered little damage on impact, we were able to gather them up for repeat drop trials, including releases at low level. All low-level runs were filmed from the bomb bay, by a chase Vampire and from the ground. The results were very encouraging. Impact with the ground was occurring well behind the aircraft, lateral spread was better than expected and every unit skipped back into flight.

  Bev had designed and produced a small number of multidirectional fuses for first non-explosive trials. Our first live trial only involved five Alphas fitted with delay fuses amongst concrete units. No explosive was included to allow post-strike inspection of each fuse. Two of these fired instantly on impact with the ground, two functioned correctly and one failed to fire. Inspection of the latter showed that the initiating cap had fired but the delay link failed to transfer to the detonator cap. In the case of the two instantaneous bursts, initiating caps’ flame had flashed past the delay links directly to the detonator caps.

  Modifications and rectification followed rapidly and we were soon testing whole clusters of Alphas charged with explosive. During this time we established that the Alpha bomblets exhibited two unexpected but highly desirable characteristics due to the rubber balls interface. The first was discovered when one bomblet had been deliberately detonated in the midst of a pyramid of unexploded bomblets (UXBs). It failed to cause a sympathetic detonation of any of the other bomblets as occurs with other explosive units—our problem was to find the widely scattered survivors for independent destruction. The second peculiarity was that we were finding hundreds of thin 20mmround shrapnel pieces that propelled like spinning saws and sliced their way into the hardest of trees. Formed by the 147 rubber balls that pressed out discs from the outer casing they spun like crazy saws aligned with their direction of flight.

  By the seventh week, one week behind schedule, the engineers were totally exhausted from their intense work schedule and many sleepless nights. However, we were ready to demonstrate to the Air Staff a full-scale Alpha strike on a 1,200 x 200-metre target that had been prepared by the Range Warden, ‘Kutanga Mac’. Hundreds of cardboard and steel targets were set above ground and in trenches throughout the length and breadth of the target.

  OC 5 Squadron, Randy du Rand, had not been too interested in our work at the start of Project Alpha, probably the consequence of my early tests with lead balls. However, once the project started to show positive results, nobody could have given greater support and assistance to the project team than Randy.

  The Commander and his senior staff officers flew to Kutanga Range to witness the demonstration and see for themselves if the Alpha system was ready for ‘the real thing’. The project team had witnessed many trials but this was to be the first full-scale drop. We had reduced the original 400 Alphas per Canberra load down to 300 to facilitate easy loading and because we had come to realise that the reduced load covered a greater strike length than the original 800 metres we had set for ourselves. The 25% cost savings was not the reason for the reduction, but it was a huge bonus.

  There was great anticipation and mounting excitement as Squadron Leader Randy du Rand opened his bomb doors late on his run-in at 400 feet at a speed of 300 knots. None of the Air Staff expected such a spectacle of dust and multiple airburst flashes as 300 bomblets did their thing. That the Alphas were bursting at perfect height well behind the Canberra was obvious to all before the sound of the explosions reached the observation point. This came as a thrilling continuous thundering of overlapping explosions.

  The Commander was quite overcome by what he witnessed and showed it by shouting, “Bloody marvellous. Absolutely bloody marvellous!” Everyone present congratulated everyone else before we all set off to walk the full length of the prepared target area.

  First inspection made it clear that the Alpha bomb system was just what we needed. When the visitors left, the project team commenced the detailed study that showed that the effective coverage of 300 Alphas was 1,100 metres in length by 120 metres in width. We had achieved more than we planned for! Fourteen unexploded bombs (UXBs) were defused for inspection in our ongoing attempts to reach 100% efficiency but, with 5% bomblet failures, the system already rated slightly better than the USA and UK guidelines for acceptable UXB rates in any cluster-bomb system.

  The important thing was that the Alpha system was cleared for operations and the Canberra had been given the antipersonnel punch it deserved. Training of crews had been done but it was considered necessary to prepare for formation attacks, initially by three Canberras. This involved flying a very flat echelon with the aircraft spaced 100 metres apart. In this way a strike length of better than 1,000 metres and a width exceeding 300 metres could be assured. The reason for the very shallow echelon was to make certain that formating aircraft did not fall back into the curtain of shrapnel rising from the exploding bombs dropped by adjacent aircraft.

  This photo shows the first half of 300 Alpha bombs dropped at a demonstration in South Africa. Note the distance of explosions behind the Canberra. The second aircraft is a long way off on photochase.

  Pyrotechnics and boosted rockets

  TARGET MARKING BY FIXED-WING aircraft using phosphorus rockets had been on going and all Army units carried smoke grenades and flares to mark FLOT and enemy positions. However, helicopters lacked the ability to put down markers from which to give other aircraft and ground troops direction. Rocket launchers were considered but discounted on the basis of weight and the fact that they would hinder rapid emplaning and deplaning of troops. Normal smoke grenades were unsuitable because they disintegrated when dropped from height.

  I read all ASRs and, having noted pilot requests for a longduration, pyrotechnic marker device, I took this on as a project to run concurrently with the Alpha Project. Besides, there was another pyrotechnic project already in hand for a RAMS requirement.

  Air Force technicians at New Sarum had recently developed a ground marker system for night bombing by Canberras. The system, known as RAMS (Radio Activated Marker Service), involved two ground flares, one of which was ignited by a radio receiver in response to a coded signal from an attacking aircraft. The other flare was manually ignited by troops on the ground. The purpose of RAMS was to give ground troops the ability to call for precision bombing of CT targets at night. This involved placing one flare as an inner marker within 300-500 metres of a live target. Having placed the inner (radio activated) marker, a bearing was taken from it to the centre of the target. The second (manually activated) flare was then sited as an outer marker on a reciprocal bearing that might be as much as 1,000 metres from the target.

  To prepare for a RAMS attack, a Canberra crew needed a fairly accurate grid reference of the target itself, the magnetic bearing from outer flare to inner flare and the distance from inner flare to target. For this type of attack, bomb-aimers (Canberra navigators) used a method known as ‘off-set aiming’. It involved calculating the difference between the normal direct aiming angle at the planned bombing height and the steeper angle given by the inner flare position. The bombsight was then depressed to the calculated ‘off-set’ angle. There was nothing to prevent a reciprocal attack-line being used, in which case the sighting angle would be shallow, but it was more comfortable to over-fly the outer marker before bomb release.

  When approaching target on the assigned attack heading, the pilot instructed the Army callsign to activate the outer flare for initial line-up. Thereafter the coded radio signal from the aircraft ignited the inner flare on the ground. Final adjustment to flight path was made to ensure correct alignment of the aircraft with the flares and bombs w
hich were released the moment the bombsight crossbar reached the inner marker. 5 Squadron had practised and perfected the offset bombing system, all of which had been done at fairly high level.

  Randy du Rand was happy enough with the existing RAMS system but felt it necessary to improve on the intensity of the flares for low-level night attacks. He was looking ahead, having visualised the need to use the proven offset bombing method for low-level delivery of Alpha bombs. Randy’s initiative was surprising on two counts. Firstly, the Alpha system had not yet been proven when he asked for brighter flares and, secondly, the new flares only became available in the nick of time for Randy’s first night attack with Alphas.

  Bev introduced me to an eccentric American pyromaniac who revelled in flames, smoke and big bangs. He was an extremely difficult man to give direction to because he kept going off at a tangent to any subject being discussed. Nevertheless, he was a real boffin when it came to producing prototype smoke generators and immensely bright flares.

  Bev made the steel containers into which the American loaded his concoctions. When we were satisfied with results we asked for repeat samples, but none gave identical results because the crazy fool kept changing ingredients without ever recording them. To pin him down was impossible and he refused point-blank to allow Bev to assist him so that Bev could establish precisely what chemicals were being used, and in what quantities. Much messing around occurred before it was realised that the man, already receiving good money for his work, sought to make a fortune from his secrets; so he was dropped, but not before Bev had established the primary chemical ingredients he had used.