Explanation was given as to why cylindrical bombs suffered too many weaknesses in bush warfare situations. The primary weakness of cylindrical bombs and warheads is that, when they burst, shrapnel is driven out at ninety degrees to their longitudinal axis. To be wholly efficient against enemy personnel, a cylindrical bomb needs to be about six feet above ground and vertically oriented at the moment of detonation, but even when dropping bombs from very high levels the vertical attitude cannot be achieved and accuracy is poor.
If the same detonation occurs when the bomb is horizontal, it is at its least efficient angle because only a narrow band of shrapnel strikes ground at ninety degrees to the bomb’s longitudinal axis. The remaining 95% of the ground around the bomb is unaffected; yet paradoxically this is the situation that occurs when bombs are dropped at low level to ensure high accuracy.
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.
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!”
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’.