page_title: Roy Fedden
section_title: Cosmos Engineering and the Jupiter
hierarchical_section_title: Roy Fedden / Cosmos Engineering and the Jupiter
context_page_description: Sir Alfred Hubert Roy Fedden MBE, FRAeS was an engineer who designed most of Bristol Engine Company's successful piston aircraft engine designs.
context_section_description: During this period, the aviation portions of Brazil Straker were purchased by Cosmos Engineering, where work on the designs continued. Both were ready for testing in 1918, but there seemed to be little interest at first. In September, however, a Mercury was experimentally fitted to a Bristol Scout and it dramatically improved performance, easily beating the competing Sunbeam Arab. Bristol then decided to try the Jupiter in their new Badger design, finding that it, too, completely outperformed the competing ABC Dragonfly. Production of both designs for Bristol was to start immediately but the war ended only days later and the contract was cancelled.
  With the ending of the war, Cosmos had no production designs and their repair work was quickly dwindling. The company was soon insolvent. Convinced of the quality of the Cosmos designs, the Air Ministry "made it be known" that they would be rather happy if the company were purchased by Bristol, which eventually took place in 1920. Sir George White later noted that they acquired the Mercury design and seven engines, all the assets of Cosmos, along with Fedden and his design team, for just £15,000. Even then most sources suggest they only did so after being persuaded to do so by the Air Ministry, which is perhaps not surprising given the fragile economy of the era.
  Bristol soon found a role for the larger design, which entered production at Bristol's new engine plant in Filton as the Bristol Jupiter. The Jupiter became a commercial success and was widely used around the world, resulting in Fedden becoming one of the most highly paid engineers in Europe. After Jimmy Ellor's pioneering work at the RAE on turbosuperchargers, the Jupiter was experimentally adapted with a turbo to become the first "Orion" design, although this saw little use.
  By the late 1920s, the Jupiter design was no longer competitive and Fedden and Butler started work on a pair of new designs. Both would use a supercharger, at that time a new-fangled idea, to provide boost even at ground level and thereby deliver similar power as the Jupiter's from a much smaller engine. Re-using their earlier name, this design emerged as the Bristol Mercury, while a more powerful design at the same size as the original Jupiter became the Bristol Pegasus.
caption: The Bristol Jupiter, designed by Roy Fedden
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