Talk:Bristol Siddeley Gamma

Molecular Mass and Thrust/ISP
The article states the relationship between molecular mass and thrust *completely* backwards. Low molecular mass exhaust gasses DECREASE thrust. What they INCREASE is specific impulse (ISP). This is as E = 1/2 m v^2 whereas thrust is based on change in momentum (which is proportional to mv rather than mv^2). The total energy levels are determined by temperature. At a given temperature, a gas with four times the molecular mass of a lighter gas will produce twice the thrust at half the specific impulse of the lighter gas, for instance. — Preceding unsigned comment added by 216.171.12.49 (talk) 18:36, 16 January 2015 (UTC)

Open cycle for Gamma 2
I don't have much information on the Gamma 2 (upper stage of Black Arrow). Was it open cycle, i.e. gas generator to exhaust? Also does anyone know what the nozzle differences were (redesigned as they didn't need to be used at sea level) Andy Dingley (talk) 15:19, 9 April 2008 (UTC)

Gamma was a closed-cycle engine, but didn't rely on conventional staged-combustion techniques - they just decomposed H2O2 to produce hot oxygen-rich steam whenever they needed power, then fed the resulting oxidizer into the combustion chamber once they were done powering the turbopump. - Chrontius (talk) 18:06, 5 August 2013 (UTC)

Adding onto this too many years later, many people are still confused about what engine cycle the Gamma engines used, some being misled by this very page due to the extensive mention of H2O2's benefits for staged combustion. No source i could find seems to state what engine cycle it used, but lots of things Strongly point to it being open cycle. I will further gather evidence here, but i doubt anything citable will show up.


 * Cutaways from the engine the Gamma was adopted from, the Stentor sustainer chamber, clearly show turbine exhaust dumps and no turbomachinery after the main catalyst bed, making the oxidizer rich staged combustion cycle described on this article impossible.
 * Piping visible on the Gamma 2 on this article is not consistent with staged combustion at all, in absence of properly sourced diagrams i cannot prove this, all i found so far were entirely unsourced diagrams being shared online.
 * Several sources and the wiki article mentioning the Soviet S1.5400 engine describe it as being the first closed cycle engine flown in 1960, while Gamma first flew '58.
 * Gamma 8 has a prominent large diameter pipe coming out of its thrust structure, a feature only seen on gas generator engines — Preceding unsigned comment added by 80.154.95.234 (talk) 07:47, 21 December 2023 (UTC)


 * For a more concrete source, one of the references from the article: "The Gamma Rocket Engines for Black Knight" from the July 1990 issue of the Journal of the British Interplanetary Society p. 301-310.
 * The turbopump section on p. 304 describes how H2O2 is decomposed to produce hot gas to power the turbine, then the gas is vented through the exhaust pipe. The paper refers to the turbine's power source as a "steam generator" rather than "gas generator", but it's definitely an open cycle. 206.127.187.1 (talk) 15:49, 17 March 2024 (UTC)

Naming and page moves
I really wish editors would think about using the Talk: pages before re-arranging pages.

What's a "Bristol Siddeley Gamma" when it's at home? Half of this town (and the half controlling the aero-engine collections) isn't talking to the other half over issues of whether a particular engine was a "Rolls" or a "Bristol" (let alone Armstrong Siddeley). The canonical name for this set of pages (and Stentor) wasn't random, it was an attempt to avoid miring the issue with politics over their names. Andy Dingley (talk) 09:54, 18 April 2008 (UTC)

Reference #6
The #6 reference goes to an AOL homepage, now defunct.

Most recent archived version is available here.

- Chrontius (talk) 18:08, 5 August 2013 (UTC)


 * Known problem, Link rot may help. Nimbus (Cumulus nimbus floats by)    00:10, 6 August 2013 (UTC)

Turbo
Should the use of turbo pumps rather than pressure feed be mentioned. --Kitchen Knife (talk) 23:11, 2 July 2015 (UTC)

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