Bristol Siddeley Gamma

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.

Gamma 201

Country of origin	Britain
Manufacturer	Bristol Siddeley
Application	1st stage booster
Predecessor	Armstrong Siddeley Stentor
Successor	Gamma 301
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	16,400 lbf (73 kN)[1][2]

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

They were developed by Armstrong Siddeley in Coventry, which later became Bristol Siddeley in 1959, and finally Rolls-Royce in 1966.^[9]

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).^[10][11] (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 and AR2) 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 (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.^[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 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. In closed 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 a gas 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]

Stentor

The Gamma was adapted^[16] as the smaller cruise chamber of the two-chamber Stentor rocket engine produced by Armstrong Siddeley for the Blue Steel stand-off missile.^[17]

Gamma 201

Bristol-Siddeley developed this stand-alone four-chamber engine from 1955 to 1957 for the Black 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 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.^{[20][21][22][23][24][25][26][27][28][29][30]}

Gamma 301

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 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.^[19]

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.^[21][32]

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.^[32]

Gallery

• Bristol Siddeley Gamma rocket engines
• 
  Gamma 201 engine behind a Black Knight re-entry vehicle
• 
  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.

References

1. "Gamma 201". Astronautix.com. Archived from the original on 13 November 2016. Retrieved 13 November 2016.
2. gamma engines rocket department dec 1964
3. Gamma engines Bristol siddeley rocket dep 1964
4. "Gamma 301". Astronautix.com. Retrieved 13 November 2016.
5. "Gamma 2". Astronautix.com. Archived from the original on 13 November 2016. Retrieved 13 November 2016.
6. "Gamma 2". Astronautix.com. Archived from the original on 13 November 2016. Retrieved 13 November 2016.
7. Black Arrow: Black Arrow, accessdate: 22. Dezember 2023
8. "Gamma 8". Astronautix.com. Archived from the original on 13 November 2016. Retrieved 13 November 2016.
9. "Rolls-Royce Heritage: Coventry". Archived from the original on 18 May 2008.
10. "The High Down Testing Site". www.spaceuk.org. Archived from the original on 16 April 2004.
11. "Black Knight Testing at The Needles". Archived from the original on 27 March 2008.
12. 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. Retrieved 4 December 2022.
13. "Black Arrow". Nicholas Hill., The "levitation" picture, showing the R3 / Prospero launch lifting off on Gamma's invisibly transparent exhaust plume.
14. 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.
15. D. Andrews & H. Sunley (July 1990). "The Gamma rocket engines for Black Knight". Journal of the British Interplanetary Society. 43: 301–310.
16. Sutton, George Paul (2006). History of liquid propellant rocket engines. Reston, Va: American Institute of Aeronautics and Astronautics. ISBN 978-1-56347-649-5.
17. "Avro Blue Steel stand-off missile". Archived from the original on 8 February 2004.
18. 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.
19. "Black Knight Flight Data". www.spaceuk.org. Archived from the original on 16 April 2003.
20. "Gamma 201 rocket engine, c. 1957". Science Museum. Archived from the original on 18 March 2010. Retrieved 9 April 2008.
21. "Gamma rocket motor". Archived from the original on 8 May 2008.
22. 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.
23. Harlow, John (November 1999). Hydrogen Peroxide Engines – Early Work on Thermal Ignition at Westcott. International Hydrogen Peroxide Propulsion Conference, Purdue University. pp. 211–219.
24. Andrews, D.; Sunley, H. (July 1990). "The Gamma Rocket Engines for Black Knight". Journal of the British Interplanetary Society. 43 (7): 301–310.
25. Andres & Sunley (1990), pp. 283–290.
26. Harlow, John (20–24 July 1998). Hydrogen Peroxide – A U.K. Perspective. University of Surrey Symposium on Hydrogen Peroxide.
27. 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.
28. Scragg, J. (July 1990). "A Contractor's View of the Black Knight Programme". Journal of the British Interplanetary Society. 43 (7): 297–300.
29. Harlow, J. (July 1990), "Black Knight Upper Stages", Journal of the British Interplanetary Society, 43 (7): 311–316
30. Robinson, H. G. R. (July 1990), "Suggested Developments of Black Knight", Journal of the British Interplanetary Society, 43 (7): 317–318
31. 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.
32. 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.