Editing Red Snow (section)

==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>