Here is the text on the Orion

“The team at Somerdale was enlarged, and work began on what Fedden had finally concluded must be started at the earliest possible date: a new engine much more powerful than the Centaurus. Under the revived name Orion, a study was made for an 18-cylinder radial with a bore of 6’/a in and capacity of 4,140 cubic inches. It incorporated several features planned for future models of the Hercules and Centaurus. One was an exhaust system with the pipes discharging straight to the rear from aft*facing ports. Another was a new design of head consisting of a close-finned copper base, with nickel-plated flame face, shrunk into a steel body. The Orion was drawn in detail by Butler in early 1941, and promised to be a superb engine rated at an initial power of about 4,000 hp. Several airframe constructors welcomed it, and Arthur Gouge (Short Brothers) and Rex Pierson (Vickers) began projects for large bombers and flying boats using four or even six. Such very big machines appeared certain to be needed – in peace, if not during the War – and the one thing Fedden wanted to avoid was having to couple together groups of smaller engines.

“With the Centaurus he had what appeared to be the most powerful aero engine in the world. With the Orion added at the top end of his family he considered the Bristol company would be able to offer an unbeatable range of engines, not only to win the War – which he said in 1941 would probably last until 1946 – but also to win the fierce commercial battles of the ensuing peace.

“Fedden was frankly and totally committed to the sleeve-valve piston engine, which he was certain would be needed up to at least 1955 and probably later. He had no doubt his company could – if it had the strategic judgement and motivation – be the world leader in piston aero engines during the whole of this period, providing the foundation for a world-beating series of British aircraft. It is characteristic of Fedden that, in early 1941, in the grimmest period of the War and long before the formation of any Brabazon Committee to study the problem, he was deeply engaged in considering the design of the aircraft for the post-war period. It was partly because of this that he appreciated the importance of the Orion.”