With the post-war rapid contraction of military orders, Cosmos Engineering went bankrupt and the Air Ministry let it be known that it would be a good idea if the Bristol Aeroplane Company purchased it. The Jupiter competed with the Armstrong Siddeley Jaguar through the 1920s but Bristol put more effort into their design and, by 1929, the Jupiter was clearly superior. In the 1930s, and led by Roy Fedden, the company developed the new Bristol Perseus line of radials based on the sleeve valve principle, which developed into some of the most powerful piston engines in the world and continued to be sold into the 1960s.
With the post-war rapid contraction of military orders, Cosmos Engineering went bankrupt and the Air Ministry let it be known that it would be a good idea if the Bristol Aeroplane Company purchased it. The Jupiter competed with the Armstrong Siddeley Jaguar through the 1920s but Bristol put more effort into their design and, by 1929, the Jupiter was clearly superior. In the 1930s, and led by Roy Fedden, the company developed the new Bristol Perseus line of radials based on the sleeve valve principle, which developed into some of the most powerful piston engines in the world and continued to be sold into the 1960s