View source for Red Snow

{{Short description|British nuclear weapon}}
{{about|the nuclear weapon Red Snow}}
{{Use British English|date=April 2012}}
{{Use dmy dates|date=June 2022}}

'''Red Snow''' was a British [[thermonuclear weapon]],<ref name=AWE-yellow-sun>{{cite web |url=http://www.awe.co.uk/main_site/about_awe/history/timeline/1961a/index.html |title=Yellow Sun MK.2 Enters Service |date=September 2007 |publisher=Atomic Weapons Establishment |archive-date=7 June 2007 |archive-url=https://web.archive.org/web/20070607113254/http://www.awe.co.uk/main_site/about_awe/history/timeline/1961a/index.html |url-status=dead }}</ref> based on the US [[B28 nuclear bomb|W28]] (then called Mark 28) design used in the B28 thermonuclear bomb and [[AGM-28 Hound Dog]] missile.<ref>{{cite web |url=http://nuclear-weapons.info/images/tna-avia65-1771e24_01.JPG |title=Defence Committee on Nuclear Requirements 1959–1963 |id=TNA AVIA 65/1771 E24 |date=17 July 1962 |work=Atomic Weapons Research Establishment |publisher=National Archive |page=1 |accessdate=2 January 2012 |quote=Red Snow is the British version of the U.S. Mk.28, which has been tested by the American Authorities. It follows that all current British nuclear weapons are based on tested designs. |archive-date=28 May 2012 |archive-url=https://web.archive.org/web/20120528213730/http://nuclear-weapons.info/images/tna-avia65-1771e24_01.JPG |url-status=live }}</ref> The US W28 had yields of {{convert|70|,|350|,|1100|and|1450|ktTNT|PJ|abbr=on}}<ref name=nukearc>{{cite web |first=Carey |last=Sublette |url=http://nuclearweaponarchive.org/Usa/Weapons/Allbombs.html |title=Complete List of All U.S. Nuclear Weapons |website=Nuclear weapon archive |date=12 June 2020 |access-date=2021-03-18 |archive-url=https://web.archive.org/web/20090227003412/http://nuclearweaponarchive.org/Usa/Weapons/allbombs.html |archive-date=2009-02-27}}</ref> and while Red Snow yields are still classified, declassified British documents indicate the existence of "kiloton Red Snow" and "megaton Red Snow" variants of the weapon, suggesting similar yield options, while other sources have suggested a yield of approximately {{convert|1|MtTNT}}.<ref name=UKAEA>{{cite report |publisher=UK Atomic Energy Authority |date=1964 |title=Weapons Department Atomic Warheads Production Committee, Papers & Minutes |url=http://nuclear-weapons.info/images/tna-ab16-4675p63.jpg |page=63 |docket=TNA AB 16/4675 |access-date=2022-04-27 |archive-date=2021-05-23 |archive-url=https://web.archive.org/web/20210523131337/http://nuclear-weapons.info/images/tna-ab16-4675p63.jpg |url-status=live }}</ref><ref name=NukeInfoWE177/>

==Development==
The Red Snow warhead was developed after a September 1958 decision to adopt the US warhead for British use, following the [[1958 US-UK Mutual Defence Agreement]]. It entered service in 1961, remaining in use until 1972, when it was replaced by the [[WE.177]] bomb.<ref name=AWE-yellow-sun/> Production numbers are classified, but it is believed that fewer than 150 weapons were produced.<ref>{{cite web |url=https://nuclearweaponarchive.org/Uk/UKArsenalDev.html |title=History of the British Nuclear Arsenal |last=Sublette |first=Carey |date=2002-04-30 |website=Nuclear Weapon Archive |access-date=2022-05-03 }}</ref>

Red Snow was used as both a free-fall bomb and as the warhead of the [[Blue Steel missile]].<ref name=AWE-yellow-sun /><ref name=AWE-blue-steel>[https://web.archive.org/web/20070922202648/http://www.awe.co.uk/main_site/about_awe/history/timeline/1961b/index.html Blue Steel Nuclear Missile Enters Service], Atomic Weapons Establishment timeline, September 2007</ref> In the gravity bomb role, it was fitted into the casing of the [[Yellow Sun (nuclear weapon)|Yellow Sun]] weapon, even though the Red Snow warhead was considerably smaller than that of the original Yellow Sun bomb.

The Red Snow physics package was later reduced in size, weight and yield, and fitted with a smaller more modern primary, intended as a [[Red Beard (nuclear weapon)|Red Beard]] replacement. Known as Una, this was later reduced in diameter and renamed Ulysses as the physics package intended for the UK warhead on the [[Skybolt]] project.<ref name=NukeArcUK>{{Cite web|url=http://www.nuclear-weapons.info/vw.htm#WE.177%20Temporary%20Footnotes|title=Nuclear-weapons.info|access-date=8 November 2009|archive-date=27 September 2018|archive-url=https://web.archive.org/web/20180927142646/http://www.nuclear-weapons.info/vw.htm#WE.177%20Temporary%20Footnotes|url-status=live}}</ref>

==Design==
Red Snow used the [[Thermonuclear weapon#Basic principle|primary stage]] Peter, an anglicised version of the US Python device used in the W28.<ref name=NukeInfoWE177>{{cite web |url=http://www.nuclear-weapons.info/vw.htm#WE.177 |title=WE.177 |last=Burnell |first=Brian |date=2018-04-15 |website=Nuclear Weapons: a Guide to British Nuclear Weapon Projects |access-date=2022-05-03 |quote="PETER – A boosted fission device, an anglicised copy of the W-34 Python primary used in the Red Snow strategic warhead and it was already in production in the UK, so could be available quickly. Yield of 11 kt was not capable of enlargement to the sizes specified by OR.1176 / 1177." |archive-date=27 September 2018 |archive-url=https://web.archive.org/web/20180927142646/http://www.nuclear-weapons.info/vw.htm#WE.177 |url-status=live }}</ref> The Peter device contained {{convert|2.25|kg|lb}} of plutonium and {{convert|1.4|kg|lb}} of uranium. The kiloton Red Snow contained {{convert|1.6|kg|lb}} of plutonium, {{convert|11|kg|lb}} of uranium, {{convert|0.6|kg|lb}} of lithium deuteride and {{convert|2.49|to|2.54|g}} of tritium, while in megaton Red Snow all the values stayed the same except the lithium deuteride amount which increased to {{convert|16|kg|lb}}.<ref name=UKAEA/>

The device was fitted inside weapon cases from the older Yellow Sun weapons. This may have been to simplify crew retraining, simplify integration of the new weapon to existing platforms, or to hide the radical reduction in weapon size.<ref name=NukeArcUK/>

==See also==
* [[Atomic Weapons Establishment]]
* [[Rainbow Codes]]

==References==
{{reflist}}

{{UKColdWarProjects}}
{{Strategic nuclear weapon systems of the United Kingdom}}

[[Category:Cold War weapons of the United Kingdom]]
[[Category:Nuclear bombs of the United Kingdom]]
[[Category:Military equipment introduced in the 1960s]]
[[Category:Rainbow code]]