The Armstrong Siddeley, later Bristol Siddeley Gamma was a family of rocket engines used in British rocketry, including the

Black Knight The black knight is a literary stock character who masks his identity and that of his liege by not displaying heraldry. Black knights are usually portrayed as villainous figures who use this anonymity for misdeeds. They are often contrasted with t ...

and

Black Arrow Black Arrow, officially capitalised BLACK ARROW, was a British satellite carrier rocket. Developed during the 1960s, it was used for four launches between 1969 and 1971, all launched from the Woomera Prohibited Area in Australia. Its final flig ...

launch vehicles. They burned kerosene fuel and

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%� ...

. Their construction was based on a common combustion chamber design, used either singly or in clusters of up to eight. They were developed by

Armstrong Siddeley Armstrong Siddeley was a British engineering group that operated during the first half of the 20th century. It was formed in 1919 and is best known for the production of luxury vehicles and aircraft engines. The company was created following ...

Coventry Coventry ( or ) is a City status in the United Kingdom, city in the West Midlands (county), West Midlands, England. It is on the River Sherbourne. Coventry has been a large settlement for centuries, although it was not founded and given its ...

, which later became

Bristol Siddeley Bristol Siddeley Engines Ltd (BSEL) was a British aero engine manufacturer. The company was formed in 1959 by a merger of Bristol Aero-Engines Limited and Armstrong Siddeley Motors Limited. In 1961 the company was expanded by the purchase of t ...

in 1959, and finally

Rolls-Royce Rolls-Royce (always hyphenated) may refer to: * Rolls-Royce Limited, a British manufacturer of cars and later aero engines, founded in 1906, now defunct Automobiles * Rolls-Royce Motor Cars, the current car manufacturing company incorporated in ...

in 1966. Engine static testing was carried out at

High Down Rocket Test Site The High Down Rocket Test Site is a former Rocket Testing facility on High Down near The Needles. The site was built and operated in secret, from the 1950s. The Black Arrow rocket, used to launch the Prospero satellite (a wholly British proje ...

, near

The Needles The Needles is a row of three stacks of chalk that rise about out of the sea off the western extremity of the Isle of Wight in the English Channel, United Kingdom, close to Alum Bay and Scratchell's Bay, and part of Totland, the westernmo ...

on the

Isle of Wight The Isle of Wight ( ) is a county in the English Channel, off the coast of Hampshire, from which it is separated by the Solent. It is the largest and second-most populous island of England. Referred to as 'The Island' by residents, the Isle of ...

(). ( Spadeadam in Cumbria wasn't used for testing until

Blue Streak Blue Streak or Bluestreak may refer to: Entertainment * ''Blue Streak'' (album), a 1995 album by American blues guitarist Luther Allison * Blue Streak (comics), a secret identity used by three separate Marvel Comics supervillains * Bluestreak (c ...

, after Gamma).

Advantages of kerosene / peroxide engines

Use of kerosene / hydrogen peroxide engines has been a particularly British trait in rocket development, there being few comparable engines (such as the LR-40) from the USA. The combustion of kerosene with hydrogen peroxide is given by the formula : CH₂ + 3H₂O₂ → CO₂ + 4H₂O where CH₂ is the approximate formula of kerosene (see

RP-1 RP-1 (alternatively, Rocket Propellant-1 or Refined Petroleum-1) is a highly refined form of kerosene outwardly similar to jet fuel, used as rocket fuel. RP-1 provides a lower specific impulse than liquid hydrogen (LH2), but is cheaper, is st ...

for a discussion of kerosene rocket fuels). This compares with the combustion of kerosene and liquid oxygen (LOX) : CH₂ + 1.5O₂ → CO₂ + H₂O showing that the exhaust from kerosene / peroxide is predominantly water. This results in a very clean exhaust (second only to cryogenic LO₂/LH₂) and a distinctive clear flame. The low molecular mass of water also helps to increase rocket thrust performance. The oxidiser used with Gamma was 85%

high-test peroxide High-test peroxide (HTP) is a highly concentrated (85 to 98%) solution of hydrogen peroxide, with the remainder consisting predominantly of water. In contact with a catalyst, it decomposes into a high-temperature mixture of steam and oxygen, with n ...

(HTP), H₂O₂. Gamma used a silver-plated on nickel-gauze catalyst to first decompose the peroxide. For higher concentrations of H₂O₂ another catalyst would have been required, such as platinum. No ignition source was required since the very hot decomposed H₂O₂ is

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 ...

(will spontaneously combust) with kerosene. Due to the high ratio (8:1) of the mass of H₂O₂ used compared to the kerosene, and also its superior heat characteristics, the H₂O₂ may also be used to regeneratively cool the engine nozzle before combustion. Any pre-combustion chamber used to power the pump turbines needs only to decompose H₂O₂ to provide the energy. This gives the efficiency advantages of closed cycle operation, without its usual major engineering problems. All of these characteristics lead to kerosene / hydrogen peroxide engines being simpler and more reliable to construct than other liquid propellant chemistries. Gamma had a remarkably reliable service record for a rocket engine. Of the 22 Black Knight and 4 Black Arrow launchers, involving 128 Gamma engines, there were no engine failures.

Stentor

The Gamma began as the smaller cruise chamber of the two-chamber

Stentor In Greek mythology, Stentor (Ancient Greek: Στέντωρ; ''gen''.: Στέντορος) was a herald of the Greek forces during the Trojan War. Mythology Stentor is mentioned briefly in Homer's ''Iliad'' in which Hera in the guise of Stent ...

rocket engine produced by

for the Blue Steel stand-off missile.

Gamma 201

Bristol-Siddeley Bristol Siddeley Engines Ltd (BSEL) was a British aero engine manufacturer. The company was formed in 1959 by a merger of Bristol Aero-Engines Limited and Armstrong Siddeley Motors Limited. In 1961 the company was expanded by the purchase of th ...

developed this stand-alone four-chamber engine from 1955 to 1957 for the

test vehicles. Gamma 201 was used for the first twelve Black Knight launches (14 in total), Gamma 301 for most of the later flights. The initial Black Knight vehicles were single-stage rockets designed to test prototype re-entry heads for the proposed

strategic

ballistic missile A ballistic missile is a type of missile that uses projectile motion to deliver warheads on a target. These weapons are guided only during relatively brief periods—most of the flight is unpowered. Short-range ballistic missiles stay within the ...

. Testing of the Black Knight began at Woomera, Australia in 1958, but the Blue Streak project was cancelled in 1960. The rockets continued to be tested until 1965, as part of a planned two-stage space launcher, using the Gamma 201 for the first stage until August 1962, when it was replaced by the more powerful Gamma 301.

Gamma 301

This was basically the same as the Gamma 201, but had automatic mixture-ratio control for improved thrust. There were nine initial test firings of the Gamma 301 engine at High Down from 16 April to 31 May 1957, all of which were largely successful.

launches BK16 and BK18 used the Gamma 301. These two were the beginning of the Project Dazzle high-speed re-entry vehicle trials, where a solid fuel

Cuckoo Cuckoos are birds in the Cuculidae family, the sole taxon in the order Cuculiformes . The cuckoo family includes the common or European cuckoo, roadrunners, koels, malkohas, couas, coucals and anis. The coucals and anis are sometimes separ ...

was mounted pointing ''downwards'' in the second stage, so as to increase re-entry speeds. Eight Gamma 301 launches were made in total.

Gamma 2 / Double Gamma

A two chamber version of Gamma, used for the second stage of the

satellite launch vehicle. As the only Gamma not required to operate at sea level, the nozzles were extended to allow better expansion.

Gamma 8

This was an 8 chamber development of Gamma, used for the first stage of the

satellite launch vehicle. Gamma thrust chambers were mounted in pairs radially, each pair on a one-axis tangential gimbal. Collective movement gave roll control, differential movement pitch.

Gallery

File:Black Knight Gamma 201 engine and re-entry head.jpg , alt=A rocket engine section with a re-entry vehicle beside it., Gamma 201 engine behind a Black Knight re-entry vehicle File:Gamma 2 engine.jpg, alt=A rocket engine on display, Gamma 2 rocket engine, used on the Black Arrow 2nd stage File:Black Arrow R3 Stage 1.JPG, alt=Battered remains of a rocket, The recovered remains of Stage 1 of the Black Arrow R3 rocket, successfully launched from the Woomera Rocket Range in October 1971.

References

{{EngvarB, date=April 2014 Rocket engines using hot cycle hydrogen peroxide propellant

Gamma Gamma (uppercase , lowercase ; ''gámma'') is the third letter of the Greek alphabet. In the system of Greek numerals it has a value of 3. In Ancient Greek, the letter gamma represented a voiced velar stop . In Modern Greek, this letter re ...

Rocket engines using the staged combustion cycle gl:Gamma 8