Bristol Jupiter


The Bristol Jupiter was a British nine-cylinder single-row piston radial engine built by the Bristol Aeroplane Company. Originally designed late in World War I and known as the Cosmos Jupiter, a lengthy series of upgrades and developments turned it into one of the finest engines of its era.
The Jupiter was widely used on many aircraft designs during the 1920s and 1930s. Thousands of Jupiters of all versions were produced, both by Bristol and abroad under licence.
A turbo-supercharged version of the Jupiter known as the Orion suffered development problems and only a small number were produced. The "Orion" name was later re-used by Bristol for an unrelated turboprop engine.

Design and development

The Jupiter was designed during World War I by Roy Fedden of Brazil Straker and later Cosmos Engineering. The first Jupiter was completed by Brazil Straker in 1918 and featured three carburettors, each one feeding three of the engine's nine cylinders via a spiral deflector housed inside the induction chamber. During the rapid downscaling of military spending after the war, Cosmos Engineering became bankrupt in 1920, and was eventually purchased by the Bristol Aeroplane Company on the strengths of the Jupiter design and the encouragement of the Air Ministry. The engine matured into one of the most reliable on the market. It was the first air-cooled engine to pass the Air Ministry full-throttle test, the first to be equipped with automatic boost control, and the first to be fitted to airliners.
The Jupiter was fairly standard in design, but featured four valves per cylinder, which was uncommon at the time. The cylinders were machined from steel forgings, and the cast cylinder heads were later replaced with aluminium alloy following studies by the Royal Aircraft Establishment. In 1927, a change was made to move to a forged head design due to the rejection rate of the castings. The Jupiter VII introduced a mechanically-driven supercharger to the design, and the Jupiter VIII was the first to be fitted with reduction gears.
In 1925, Fedden started designing a replacement for the Jupiter. Using a shorter stroke to increase the revolutions per minute, and including a supercharger for added power, resulted in the Bristol Mercury of 1927. Applying the same techniques to the original Jupiter-sized engine in 1927 resulted in the Bristol Pegasus. Neither engine would fully replace the Jupiter for a few years.
In 1926 a Jupiter-engined Bristol Bloodhound with the registration G-EBGG completed an endurance flight of, during which the Jupiter ran for a total of 225 hours and 54 minutes without part failure or replacement.

Licensed production

The Jupiter saw widespread use in licensed versions, with fourteen countries eventually producing the engine. In France, Gnome-Rhone produced a version known as the Gnome-Rhône 9 Jupiter that was used in several local civilian designs, as well as achieving some export success. Siemens-Halske took out a licence in Germany and produced several versions of increasing power, eventually resulting in the Bramo 323 Fafnir, which saw use in German wartime aircraft.
In Japan, the Jupiter was license-built from 1924 by Nakajima, forming the basis of its own subsequent radial aero-engine design, the Nakajima Ha-1 Kotobuki. It was produced in Poland as the PZL Bristol Jupiter, in Italy as the Alfa Romeo 126-RC35, and in Czechoslovakia by Walter Engines. The most produced version was in the Soviet Union, where its Shvetsov M-22 version powered the initial Type 4 version of the Polikarpov I-16. Type 4 Polikarpovs can be identified by their lack of exhaust stubs, rounded NACA cowling and lack of cowling shutters, features which were introduced on the Shvetsov M-25 powered Type 5 and later variants. Production started in 1918 and ceased in 1930.

Variants

The Jupiter was produced in many variants, one of which was the Bristol Orion of 1926. Metallurgy problems with this turbo-supercharged engine caused the project to be abandoned after only nine engines had been built.
;Brazil Straker Jupiter I
;Cosmos Jupiter II
;Bristol Jupiter II
;Bristol Jupiter III
.
;Bristol Jupiter IV
;Bristol Jupiter V
;Bristol Jupiter VI
;Bristol Jupiter VIA
;Bristol Jupiter VIFH
;Bristol Jupiter VIFL
;Bristol Jupiter VIFM
;Bristol Jupiter VIFS
;Bristol Jupiter VII
;Bristol Jupiter VIIF
;Bristol Jupiter VIIFP
;Bristol Jupiter VIII
;Bristol Jupiter VIIIF
;Bristol Jupiter VIIIFP
;Bristol Jupiter IX
;Bristol Jupiter IXF
;Bristol Jupiter X
;Bristol Jupiter XF
;Bristol Jupiter XFA
;Bristol Jupiter XFAM
;Bristol Jupiter XFBM
;Bristol Jupiter XFS
;Bristol Jupiter XI
;Bristol Jupiter XIF
;Bristol Jupiter XIFA
;Bristol Jupiter XIFP
;Bristol Orion I
;Gnome-Rhône 9A Jupiter:French licence production primarily of 9A, 9Aa, 9Ab, 9Ac, 9Akx and 9Ad variants.
;Siemens-Halske Sh20, Sh21 and Sh22: Siemens-Halske took out a licence in Germany and produced several versions of increasing power, eventually resulting in the Bramo 323 Fafnir, which saw use in wartime models.
;Nakajima Ha-1 Kotobuki: In Japan, the Jupiter was licence-built from 1924 by Nakajima.
;PZL Bristol Jupiter: Polish production.
;Alfa Romeo Jupiter: Italian licence production,.
;Alfa 126 R.C.35: Alfa Romeo developed variant
;Walter Jupiter: Licence production in Czechoslovakia by Walter Engines
;Shvetsov M-22: The most produced version; manufactured in the Soviet Union.
;IAM 9AD: Licence production of the Gnome-Rhône 9A in Yugoslavia
;SABCA Jupiter: license production in Belgium by SABCA
;Piaggio-Jupiter: License production by Piaggio

Applications

The Jupiter is probably best known for powering the Handley Page H.P.42 airliners, which flew the London-Paris route in the 1930s. Other civilian uses included the de Havilland Giant Moth and de Havilland Hercules, the Junkers G 31 and the huge Dornier Do X flying boat, which used no less than twelve engines.
Military uses were less common, but included the parent company's Bristol Bulldog, as well as the Gloster Gamecock and Boulton Paul Sidestrand. It was also found in prototypes around the world, from Japan to Sweden.
By 1929 the Bristol Jupiter had flown in 262 different aircraft types,
Note:

Cosmos Jupiter