Société D'Etudes Pour La Propulsion Par Réaction
   HOME

TheInfoList



OR:

The (SEPR) (in ) was a French research and manufacturing company founded in 1944 which specialised in the development of liquid-fuelled rocket engines during the 1950s, 60s, 70s and 80s. The SEPR 841 is a liquid-fuelled
rocket engine A rocket engine is a reaction engine, producing thrust in accordance with Newton's third law by ejecting reaction mass rearward, usually a high-speed Jet (fluid), jet of high-temperature gas produced by the combustion of rocket propellants stor ...
used as an auxiliary power unit for the
Dassault Mirage III The Dassault Mirage III () is a family of single/dual-seat, single-engine, fighter aircraft developed and manufactured by French aircraft company Dassault Aviation. It was the first Western European combat aircraft to exceed Mach 2 in horizont ...
mixed-power high-altitude interceptor aircraft of the 1960s. The engine was one of several similar engines developed by SEPR.


Mixed-power

In the 1950s, Western Europe was much concerned about attacks by fleets of high-flying bombers, such as the Tu-95 ''Bear''. These pre-dated the development of either practical
afterburner An afterburner (or reheat in British English) is an additional combustion component used on some jet engines, mostly those on military supersonic aircraft. Its purpose is to increase thrust, usually for supersonic flight, takeoff, and combat ...
s or surface-to-air missiles, and so means to improve the performance of conventional aircraft were sought. Particularly in France, and to some extent in the UK, mixed-power interceptor aircraft were studied, with a combination of jet and rocket power. The rocket would be used for high-altitude performance, increasing either speed or ceiling. French studies for mixed-power interceptors began in 1948. By 1953, the SNCASO Trident aircraft was in flight. This was an unusual design, with a single three-chambered SEPR rocket engine as the main engine, assisted for take-off and low altitude flight by two
Turbomeca Marboré The Turbomeca Marboré is a small turbojet engine that was produced by Turbomeca from the 1950s into the 1970s. The most popular uses of this engine were in the Fouga CM.170 Magister and the Morane-Saulnier MS.760 Paris. It was also licensed f ...
turbojets. The Trident was difficult to handle on the low-powered turbojets alone and was thirsty for fuel on rocket power. This primary use of the rocket was not repeated in the future: later aircraft would be jet-powered, with the rocket reserved for high-speed dashes. Later rockets would also be considerably less powerful than the Trident's SEPR 48–1. A development for the Trident II aircraft was the two chamber SEPR 631 engine. The two chambers could be fired separately. Although not throttleable, this did give a half-thrust setting.


Mirage

The
Mirage A mirage is a naturally-occurring optical phenomenon in which light rays bend via refraction to produce a displaced image of distant objects or the sky. The word comes to English via the French ''(se) mirer'', from the Latin ''mirari'', mean ...
and its distinctive
delta wing A delta wing is a wing shaped in the form of a triangle. It is named for its similarity in shape to the Greek uppercase letter delta (letter), delta (Δ). Although long studied, the delta wing did not find significant practical applications unti ...
planform In technical drawing and computer graphics, a multiview projection is a technique of illustration by which a standardized series of orthographic projection, orthographic two-dimensional pictures are constructed to represent the form of a three-d ...
began with the prototype MD.550 Mystère-Delta. This bore little relation, other than its name, to the
Dassault Mystère The Dassault MD.452 Mystère is a 1950s French fighter-bomber. It was a straightforward development of the successful Dassault Ouragan Development After the success of the Ouragan, Dassault was working on a more advanced machine which woul ...
; France's swept-wing fighter of the period. The delta aircraft was smaller, around two thirds of the Mystère's weight and was powered by two small
Viper Vipers are snakes in the family Viperidae, found in most parts of the world, except for Antarctica, Australia, Hawaii, Madagascar, New Zealand, Ireland, and various other isolated islands. They are venomous and have long (relative to non-vipe ...
turbojets and the SEPR 66 rocket. All three of these engines barely exceeded the thrust of the Mystère's ATAR 101D, although they also only weighed about half of the ATAR.


Mirage IIIC

The Mirage III adopted the more developed and afterburning ATAR 9. As the delta wing considerably increased the supersonic capacity of the aircraft, rocket power was retained. This was the first European aircraft to exceed Mach 2 in level flight. It was recognised that most mission profiles did not require the rocket and could not afford its fuel consumption. The original goal of intercepting high-flying bombers also seemed to be receding in favour of missiles, for both offence and defence. The Mirage's rocket was thus mounted as a removable pod which could be replaced with a jet fuel tank for additional range. Only the high altitude interception would still use it. To retain balance as rocket fuel was consumed, the rocket pack was in two parts. The
nitric acid Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...
oxidiser tank was mounted directly ahead of the rocket engine. A smaller TX2 Furaline fuel tank was mounted in the front bay just behind the cockpit, replacing the cannon pack. When in the rocket-powered interceptor role, the aircraft would only be armed with missiles. The rocket pack could be swapped in around 20 minutes by removing six bolts. Fuelling the rocket oxidiser was potentially somewhat hazardous and so it was carried out away from other aircraft, by groundcrew in protective clothing and with a fire crew standing by in order to flush away any spillage. Acid refuelling was carried out above a steel drip tray, with the acid flow and tank vent return through closed pipework with a sightglass to observe full tanks. Performance in training sorties achieved Mach 1.4 without the rocket and 1.8 with. Altitudes of could be reached in a zoom climb, or on rocket thrust. A typical training sortie duration of 45 minutes would be reduced to under 30, with high Mach and rocket use.


Auxiliary rocket engines

SEPR's auxiliary rocket engines were based on
hypergolic A hypergolic propellant is a rocket propellant combination used in a rocket engine, whose components spontaneously ignite when they come into contact with each other. The two propellant components usually consist of a fuel and an oxidizer. The ...
fuel chemistry of 98.5%
nitric acid Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...
(HNO3) oxidiser with
furfuryl alcohol Furfuryl alcohol is an organic compound containing a furan substituted with a hydroxymethyl group. It is a colorless liquid, but aged samples appear amber. It possesses a faint odor of burning and a bitter taste. It is miscible with but unstabl ...
as a fuel, in the ratio of 2.4:1. Later fuels were a mixture of 41% furfuryl alcohol, 41%
xylidine Xylidine can refer to any of the six isomers of xylene amine, or any mixture of them. The chemical formula of xylidines is C8H11N or, more descriptively, (CH3)2C6H3NH2. The CAS number for the isomer mixture is 1300-73-8. They are colorless solids ...
and 18% methyl alcohol, called furaline. Unusually, the
turbopump A turbopump is a fluid pump with two main components: a rotodynamic pump and a driving gas turbine, usually both mounted on the same shaft, or sometimes geared together. They were initially developed in Germany in the early 1940s. The most co ...
s for some of SEPR's engine were mechanically driven from outside. A mechanical drive shaft from the
accessory drive The accessory drive is a gearbox that forms part of a gas turbine engine. Although not part of the engine's core, it drives the accessories – such as generators, pumps for fuel and lubrication oil, air compressors, hydraulic pumps and engine st ...
of the main turbojet provided the needed at 5,070 rpm, provided that the engine was running at full speed. As the propellants are hypergolic, the engine can be ignited repeatedly simply by engaging the clutch drive to the pump. The engine's single combustion chamber was regeneratively cooled by the acid oxidiser.


SEPR 841

The 841 used TX2 ( triethylamine xylidine) as a fuel. The engine was designed for simplicity and reliability, rather than sophisticated control. The pilot's only control was a simple on/off switch, with the valves and pump then controlled by an electromechanical timer. Power for actuating the main valves was then obtained by a compressed air bottle or fuel pressure. The tanks were air pressurised, the fuel tank by engine compressor
bleed air Bleed air in aerospace engineering is compressed air taken from the compressor stage of a gas turbine, upstream of its fuel-burning sections. Automatic air supply and cabin pressure controller (ASCPC) valves bleed air from low or high stage engine ...
and the oxidiser tank by ram air and additionally by the stored air bottle. Ram air was taken from the supersonic inlet boundary layer bleeds. A single timer-controlled valve opened the stored air supply which then opened the pneumatic LP cocks. A second valve, after a delay, engaged the turbopump clutch. HP cocks were opened by a single hydraulic piston, driven by fuel pressure controlled through a third timed valve. Both fuel and oxidiser first flowed through a small pilot valve for ignition, before their main valves opened. Correct opening of all four valves was monitored by the timer control, to ensure a safe mixture. A dump valve system was provided for any residual acid. Oxidiser loaded was burned in flight before landing, or dumped. Bulk production of the engines was carried out by
Hispano-Suiza Hispano-Suiza () is a Spanish automotive company. It was founded in 1904 by Marc Birkigt and as an automobile manufacturer and eventually had several factories in Spain and France that produced luxury cars, aircraft engines, trucks and weapons. ...
.


SEPR 844

For simplicity of fuel supply, the TX2 fuel of the SEPR 84-1 was replaced with standard jet TR-0
kerosene Kerosene, or paraffin, is a combustibility, combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in Aviation fuel, aviation as well as households. Its name derives from the Greek (''kērós'') meaning " ...
as the SEPR 84–4. This required a few changes to the engine. For reliable hypergolic ignition, a small TX tank was retained to supply the engine's pilot ignition valve. This fuel supply was controlled very simply, by displacement under fuel pressure acting on a piston in the tank. TX capacity limited the engine to just two or three starts per flight. The forward bay tank could also be used as an additional fuel tank for the main jet engine. The main tankage could not, however, supply the rocket. Replacing both rocket and cannon with the fuel tanks gave additional
ferry A ferry is a boat or ship that transports passengers, and occasionally vehicles and cargo, across a body of water. A small passenger ferry with multiple stops, like those in Venice, Italy, is sometimes referred to as a water taxi or water bus ...
range.


See also

; Aircraft *
Saunders-Roe SR.53 The Saunders-Roe SR.53 was a British prototype interceptor aircraft of mixed jet and rocket propulsion developed for the Royal Air Force (RAF) by Saunders-Roe in the early 1950s. As envisaged, the SR.53 would have been used as an interceptor ...
; Engines * Napier Scorpion


References

{{DEFAULTSORT:Societe d'Etudes pour la Propulsion par Reaction Aircraft rocket engines Rocket engines using hypergolic propellant Research institutes in France