Maiden Flight of the Saunders-Roe S-R.53 Mixed-Power-Plant Interceptor
de Havilland Spectre powers Britain's first manned aircraft with primary rocket propulsion

THE association between the parent companies of the Saunders-Roe and the de Havilland groups of companies was announced in November. 1956. Now, in the S-R.53 mixed-power-plant interceptor, which made its maiden flight on May 16, J957, we see the fruits of a long technical. co-operation between Saunders-Roe Limited of Cowes, Isle of Wight, and The de Havilland Engine Company Limited of
Leavesden, Hertfordshire.

This photograph shows the Sounders-Roe S-R.53 to be an extremely sleek and good-looking aircraft, even with wheels down.

The S-R.53 is the first British manned aircraft to employ the mixed-power formula rocket engine and jet-turbine - which has been originated by Saunders-Roe to meet the problem of high-altitude interception and has been one of the de Havilland Engine Company's
major developments since the war. In the S-R.53 aircraft it is the rocket engine which is the primary source of power.

The new formula undoubtedly has a vital place in Western defence plans as now evolving. Until such time as the ground-to-air missile
can effectively undertake all aspects of air defence. the mixed-power interceptor, manned in the first stage of its development, affords a
practical means - perhaps the only means of defending vital targets against the transonic or supersonic high-altitude manned bomber.
Mixed power ensures the extremely rapid climb to stratospheric heights and the swift acceleration to high supersonic speeds at
altitude, combined with the endurance necessary for a practical operation. It has other remarkable advantages as well.

An aircraft such as the S-R.53 provides great operational flexibility. A very high power-to-weight ratio - more favourable than can be achieved by the addition of more or larger jet engines - ensures a shorter-than normal take-off A low landing weight, the result of rocket fuel consumption, ensures unusually favourable short-landing characteristics. This means smaller airfields and it is once again possible to use metal mesh laid on grass, as in former years.

Tactical flexibility is paramount. The jet-fuel/rocket fuel ratio can be varied to suit the early warning available. For short warning,
rocket and jet combine to give the fastest time to operational height. When longer warning is available. the accent is on range or
endurance at altitude. In these circumstances the rocket is brought in for final climb and acceleration.

The main power-plant of the Saunders-Roe S-R.53 is -the de Havilland Spectre liquid propellent rocket engine. This employs the principle
of variable thrust control and is the first British rocket engine of this type to have flown. The- rocket engine, unlike air-breathing
piston and gas turbine engines, is entirely independent of the atmosphere for oxygen to support the combustion of a hydro-carbon
fuel. The rocket carries with it its own oxidant - highly concentrated hydrogen peroxide (H.T.P.) in the case of the Spectre-which. by a simple catalytic process, is changed into heavily oxygenated. superheated steam; it is in this gaseous mixture that finely atomised kerosene or gasolene fuel spontaneously ignites to produce additional thrust. A rocket-engined aircraft thus avoids the inevitable loss of power which during ascent and at great height s handicaps the performance of aircraft fitted with more conventional means of propulsion. Indeed an engine such as the Spectre enjoys enhanced performance under these conditions as diminishing outside pressure permits more efficient functioning.

S-R. 53. The first manned British aircraft to have a rocket engine as its main power plant flew from the Ministry of Supply establishment at Boscombe Down on May 16 this year. The de Havilland Engine Company Limited, in addition to building the Spectre rocket engine. is
developing the Gyron series to operate in conjunction with rocket power. The prototype S-R.53. however. is fitted with the Armstrong
Siddeley Viper jet engine.

The Spectre is the result of many years of research and development by the de Havilland Engine Company; during this time the relative
merits of various types of oxidants were carefully studied and the final choice of hydrogen peroxide indicates a decision based not only
upon operating efficiency but upon considerations of storage problems, chemical stability, availability and - of outstanding importance safety.

The de Havilland Spectre. which was developed under a Ministry of Supply contract, first ran in July, 1953. and had been engaged on an extensive programme of test-bed running when in December. 1956, these ground-running trials supplemented by flight-testing in a Canberra aircraft. Air experience soon established its excellent handling qualities over a wide range of operating conditions and official approval was obtained in March, 1957. for the engine to be flown in aircraft other than the Canberra. During the flight-testing period the advantages of precise thrust control have been proved and it has been shown that this feature affords exceptional operational flexibility.

Rocket-powered aircraft are able to climb to operational levels, now in the stratosphere. in a shorter time than has ever before been
possible. At such heights they are capable of very rapid acceleration to high-supersonic combat speeds and they possess the reserve of
power which is essential for manoeuvring in rarefied air at great altitudes. Carrying their own supply of oxygen in addition to fuel.
aircraft powered solely by rocket engines are, however. capable of only relatively short endurance. and it is for this reason that the
de Havilland Engine Company have evolved in the Gyron family a special type of gas turbine engine which has been designed to
operate at high efficiency in conjunction with rocket power.

The S-R.53 design team was led by Mr. M.J. Brennan, BSc, Mi Mech E., F.R.Ae.S., chief designer of Saunders Roe.
Squadron Leader J. S. Booth, D.F.C., Saunders-Roe's chief test pilot flew the S-R.53 on its maiden flight

These engines a re capable of maintaining very high speeds at great altitude after the rocket engine, having provided the initial
acceleration, is shut down. Further, their fuel economy under these conditions and during a turbine-powered cruise return to base makes
possible an operational sortie of useful duration. The use of these two types of power unit in logical partnership forms the basis of
the de Havilland mixed-power-plant formula for high-performance military aircraft.

D.H Spectre Magazine Advertisement From 1958