Gamma 301

Black Knight tail showing engines
Application	1st stage booster
Predecessor	Gamma 201
Successor	Gamma 8
Liquid-fuel engine
Propellant	Hydrogen peroxide / kerosene
Mixture ratio	8:1 (approx.)
Cycle	Gas-generator
Configuration
Chamber	4, gimballed in opposed pairs
Performance
Thrust, sea-level	17,000–21,600[3] lbf (76–96 kN)-21,000 lbf (93 kN)[4]
Specific impulse	250 seconds (2.5 km/s)
Burn time	120 seconds

Gamma 2

Gamma 2 rocket engine, used for the second stage
Application	2nd stage
Predecessor	Gamma 301
Successor	Larch (rocket engine)
Liquid-fuel engine
Propellant	Hydrogen peroxide / kerosene
Cycle	Gas-generator
Configuration
Chamber	2, extended
Performance
Thrust, vacuum	68.2 kN (15,300 lbf)[5]
Thrust, sea-level	64.60 kN (14,520 lbf)[6]
Burn time	113 seconds[7]

Gamma 8

Gamma 8 rocket engine on Black Arrow 1st stage
Application	1st stage booster
Predecessor	Gamma 301
Liquid-fuel engine
Propellant	Hydrogen peroxide / kerosene
Cycle	Gas-generator
Configuration
Chamber	8, gimballed in pairs
Performance
Thrust, sea-level	52,785 lbf (234.80 kN)[8]
Burn time	125 seconds

TheArmstrong Siddeley, laterBristol SiddeleyGamma was a family of rocket engines used in British rocketry, including theBlack Knight andBlack Arrow launch vehicles. They burned kerosene fuel andhydrogen peroxide. Their construction was based on a common combustion chamber design, used either singly or in clusters of up to eight.

They were developed byArmstrong Siddeley inCoventry, which later becameBristol Siddeley in 1959, and finallyRolls-Royce in 1966.^[9]

Engine static testing was carried out atHigh Down Rocket Test Site, nearThe Needles on theIsle of Wight (50°39′38.90″N1°34′38.25″W / 50.6608056°N 1.5772917°W /50.6608056; -1.5772917).^[10][11] (Spadeadam in Cumbria wasn't used for testing untilBlue Streak, after Gamma).

Use of kerosene / hydrogen peroxide engines has been a particularly British trait in rocket development, there being few comparable engines (such as theLR-40 andAR2) from the US.^[12]

The combustion of kerosene with hydrogen peroxide is given by the formula

CH₂ + 3H₂O₂ → CO₂ +4H₂O

where CH₂ is the approximate formula of kerosene (seeRP-1 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.^[13] The low molecular mass of water also helps to increase rocket thrust performance.^[14]

The oxidiser used with Gamma was 85%high-test peroxide (HTP), H₂O₂. Gamma used a silver-plated on nickel-gauze catalyst to first decompose the peroxide.^[15] 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 ishypergolic (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 toregeneratively cool the engine nozzle before combustion. Inclosed cycle engines the pre-combustion chamber used to power any pump turbines needs only to decompose H₂O₂ to provide energy. This gives the efficiency advantages of closed cycle operation, without its usual major engineering problems. The Gamma, being agas generator cycle engine however did not take advantage of this.

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.^[14]

The Gamma was adapted^[16] as the smaller cruise chamber of the two-chamberStentor rocket engine produced byArmstrong Siddeley for theBlue Steel stand-off missile.^[17]

Bristol-Siddeley developed this stand-alone four-chamber engine from 1955 to 1957 for theBlack Knight test vehicles.^[18] Gamma 201 was used for the first twelve Black Knight launches (14 in total), Gamma 301 for most of the later flights.^[19]

The initial Black Knight vehicles were single-stage rockets designed to test prototype re-entry heads for the proposedBlue Streak strategicballistic missile. Testing of the Black Knight began atWoomera, 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 theGamma 201 for the first stage until August 1962, when it was replaced by the more powerfulGamma 301.^{[20][21][22][23][24][25][26][27][28][29][30]}

This was basically the same as the Gamma 201, but had automatic mixture-ratio control for improved thrust.^[31] There were nine initial test firings of the Gamma 301 engine atHigh Down from 16 April to 31 May 1957, all of which were largely successful.Black Knight launches BK16 and BK18 used the Gamma 301. These two were the beginning of theProject Dazzle high-speed re-entry vehicle trials, where a solid fuelCuckoo was mounted pointingdownwards in the second stage, so as to increase re-entry speeds. Eight Gamma 301 launches were made in total.^[19]

A two chamber version of Gamma, used for the second stage of theBlack Arrow satellite launch vehicle. As the only Gamma not required to operate at sea level, the nozzles were extended to allow better expansion.^[21][32]

This sectionneeds expansion. You can help byadding missing information.(June 2008)

This was an 8 chamber development of Gamma, used for the first stage of theBlack Arrow 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.^[32]

This sectionneeds expansion. You can help byadding missing information.(June 2008)

• Bristol Siddeley Gamma rocket engines
• 
  Gamma 201 engine
• 
  Gamma 2 rocket engine, used on the Black Arrow 2nd stage
• 
  The recovered remains of Stage 1 of the Black Arrow R3 rocket, successfully launched from the Woomera Rocket Range in October 1971.

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