Bristol Siddeley Gamma

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.)
Configuration
Chamber	4, gimballed in opposed pairs
Performance
Thrust (SL)	16,860 lbf (75.0 kN)-21,000 lbf (93 kN)
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
Configuration
Chamber	2, extended
Performance
Thrust (SL)	14,523 lbf (64.60 kN)
Burn time	110–120 seconds

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
Configuration
Chamber	8, gimballed in pairs
Performance
Thrust (SL)	52,785 lbf (234.80 kN)
Burn time	125 seconds

The Armstrong Siddeley, later Bristol Siddeley Gamma was a family of rocket engines used in British rocketry, including the Black Knight and Black Arrow launch vehicles. They burned kerosene fuel and hydrogen peroxide. 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 in Coventry, which later became Bristol Siddeley in 1959, and finally Rolls-Royce in 1966.

Engine static testing was carried out at High Down Rocket Test Site, near The Needles on the Isle of Wight (50°39′38.90″N 1°34′38.25″W / 50.6608056°N 1.5772917°W / 50.6608056; -1.5772917). (Spadeadam in Cumbria wasn't used for testing until Blue 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 the LR-40) from the USA.

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

where CH₂ is the approximate formula of kerosene (see RP-1 for a discussion of kerosene rocket fuels). This compares with the combustion of kerosene and liquid oxygen (LOX)

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.