Bristol Siddeley Gamma


Gamma 201
Country of originBritain
ManufacturerBristol Siddeley
Application1st stage booster
PredecessorArmstrong Siddeley Stentor
SuccessorGamma 301
Liquid-fuel engine
PropellantHydrogen peroxide / kerosene
Mixture ratio8:1 (approx.)
Chamber4, gimballed in opposed pairs
Thrust (SL)16,400 lbf (73 kN)[1][2]
Gamma 301
Black Knight tail.jpg
Black Knight tail showing engines
Application1st stage booster
PredecessorGamma 201
SuccessorGamma 8
Liquid-fuel engine
PropellantHydrogen peroxide / kerosene
Mixture ratio8:1 (approx.)
Chamber4, gimballed in opposed pairs
Thrust (SL)17,000–21,600[3] lbf (76–96 kN)-21,000 lbf (93 kN)[4]
Specific impulse250 seconds (2.5 km/s)
Burn time120 seconds
Gamma 2
Gamma 2 rocket engine on Black Arrow 2nd stage.jpg
Gamma 2 rocket engine, used for the second stage
Application2nd stage
PredecessorGamma 301
SuccessorLarch (rocket engine)
Liquid-fuel engine
PropellantHydrogen peroxide / kerosene
Chamber2, extended
Thrust (SL)14,523 lbf (64.60 kN)[5]
Burn time110–120 seconds
Gamma 8
Gamma 8 rocket engine on Black Arrow 1st stage.jpg
Gamma 8 rocket engine on Black Arrow 1st stage
Application1st stage booster
PredecessorGamma 301
Liquid-fuel engine
PropellantHydrogen peroxide / kerosene
Chamber8, gimballed in pairs
Thrust (SL)52,785 lbf (234.80 kN)[6]
Burn time125 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.[7]

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).[8][9] (Spadeadam in Cumbria wasn't used for testing until Blue Streak, 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.[10]

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 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.[11] The low molecular mass of water also helps to increase rocket thrust performance.[12]

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.[13] 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 (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.[12]


The Gamma began as the smaller cruise chamber of the two-chamber Stentor rocket engine produced by Armstrong Siddeley for the Blue Steel stand-off missile.[14]

Gamma 201

Bristol-Siddeley developed this stand-alone four-chamber engine from 1955 to 1957 for the Black Knight test vehicles.[15] Gamma 201 was used for the first twelve Black Knight launches (14 in total), Gamma 301 for most of the later flights.[16]

The initial Black Knight vehicles were single-stage rockets designed to test prototype re-entry heads for the proposed Blue Streak strategic ballistic missile. 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.[17][18][19][20][21][22][23][24][25][26][27]

Gamma 301

This was basically the same as the Gamma 201, but had automatic mixture-ratio control for improved thrust.[28] 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. Black Knight 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 was mounted pointing downwards in the second stage, so as to increase re-entry speeds. Eight Gamma 301 launches were made in total.[16]

Gamma 2 / Double Gamma

A two chamber version of Gamma, used for the second stage of the Black Arrow satellite launch vehicle. As the only Gamma not required to operate at sea level, the nozzles were extended to allow better expansion.[18][29]

Gamma 8

This was an 8 chamber development of Gamma, used for the first stage of the Black 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.[29]



  1. ^ "Gamma 201". Retrieved 13 November 2016.
  2. ^ gamma engines rocket department dec 1964
  3. ^ Gamma engines Bristol siddeley rocket dep 1964
  4. ^ "Gamma 301". Retrieved 13 November 2016.
  5. ^ "Gamma 2". Retrieved 13 November 2016.
  6. ^ "Gamma 8". Retrieved 13 November 2016.
  7. ^ "Rolls-Royce Heritage: Coventry". Archived from the original on 18 May 2008.
  8. ^ "High Down".
  9. ^ "Black Knight Testing at The Needles". Archived from the original on 27 March 2008.
  10. ^ Hydrogen Peroxide – Optimal For Turbomachinery and Power Applications (PDF). 43rd IAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit. Cincinnati, OH: American Institute of Aeronautics and Astronautics, Inc. July 2007.[permanent dead link]
  11. ^ "Black Arrow". Nicholas Hill., The "levitation" picture, showing the R3 / Prospero launch lifting off on Gamma's invisibly transparent exhaust plume.
  12. ^ a b Pietrobon, Steven S. (May–June 1999). "High Density Liquid Rocket Boosters for the Space Shuttle" (PDF). Journal of the British Interplanetary Society. 52: 163–168. Bibcode:1999JBIS...52..163P.
  13. ^ D. Andrews & H. Sunley (July 1990). "The Gamma rocket engines for Black Knight". Journal of the British Interplanetary Society. 43: 301–310.
  14. ^ "Avro Blue Steel stand-off missile". Archived from the original on 8 February 2004.
  15. ^ C.N. Hill (2001). A Vertical Empire: The History of the UK Rocket and Space Programme, 1950–1971. Imperial College Press. ISBN 978-1-86094-268-6.
  16. ^ a b "UK Rocket History".
  17. ^ "Gamma 201 rocket engine, c. 1957". Science Museum. Archived from the original on 18 March 2010. Retrieved 9 April 2008.
  18. ^ a b "Gamma rocket motor". Archived from the original on 8 May 2008.
  19. ^ Harlow, John (1993). Alpha, Beta and RTV-1, The Development of Early British Liquid Propellant Rocket Engines. Congress of the International Astronautical Federation (IAA). Graz, Austria.
  20. ^ Harlow, John (November 1999). Hydrogen Peroxide Engines – Early Work on Thermal Ignition at Westcott. International Hydrogen Peroxide Propulsion Conference, Purdue University. pp. 211–219.
  21. ^ Andrews, D.; Sunley, H. (July 1990). "The Gamma Rocket Engines for Black Knight". Journal of the British Interplanetary Society. 43 (7): 301–310.
  22. ^ Andres & Sunley (1990), pp. 283–290.
  23. ^ Harlow, John (20–24 July 1998). Hydrogen Peroxide – A U.K. Perspective. University of Surrey Symposium on Hydrogen Peroxide.
  24. ^ Robinson, H. G. R. (July 1990). "Overview of the Black Knight Project: Black Knight, its Genesis". Journal of the British Interplanetary Society. 43 (7): 291–296.
  25. ^ Scragg, J. (July 1990). "A Contractor's View of the Black Knight Programme". Journal of the British Interplanetary Society. 43 (7): 297–300.
  26. ^ Harlow, J. (July 1990), "Black Knight Upper Stages", Journal of the British Interplanetary Society, 43 (7): 311–316
  27. ^ Robinson, H. G. R. (July 1990), "Suggested Developments of Black Knight", Journal of the British Interplanetary Society, 43 (7): 317–318
  28. ^ H.W.B. Gordon B.A. & L.W. Parkin MSc (February 1964). A Summary of "Black Knight" Flight Data from 1958 to 1962. UK gov. Original may be found in the Public Record Office, Kew (part of AVIA 6 17362), the on-web link is to a precis by Nicholas Hill. Archived from the original on 25 September 2005. Retrieved 10 April 2008.
  29. ^ a b Douglas Millard (2001). Black Arrow rocket: A History of a Satellite Launch Vehicle and its Engines. London: Science Museum. ISBN 978-1-900747-41-7.