Editing GAM-87 Skybolt (section)

===Development and testing===
[[File:Avro Vulcan and B-52 over Edwards Air Force Base.jpg|thumb|right|Avro Vulcan and B-52 over Edwards Air Force Base]]
During development, it was decided that the system could not reach the required accuracy at the desired range without improvements to the guidance system. This led to the introduction of a [[star tracker]] platform that would enhance the existing [[inertial navigation system]]. For this role, the system had to be capable of tracking bright stars in direct sunlight, a challenging requirement. Star trackers have to be provided with a relatively accurate location in order to point their trackers at selected stars. Over a long flight, the INS would drift too much to provide the needed accuracy. Instead, the tracker has to be able to track the stars during flight, continually updating the INS.

This change meant that the missile could only be carried in locations where the front of the missile could continually observe the sky. This had always been the case on the USAF's [[Boeing B-52 Stratofortress|B-52]] bombers, where they were carried under the narrow-chord wings and the nose projected out in front. But this presented a problem for some of the UK designs, especially the [[Handley Page Victor|Victor]], where the layout of the wing, engines and landing gear left the mounting point behind the massive wing's leading edge. As [[Vickers Valiant|Valiant]] had limited range, the decision was made to move forward only with [[Avro Vulcan|Vulcan]], where its mounting points allowed the nose of the missile to project in front of this aircraft's [[delta wing]].

By 1961, several test articles were ready for testing from B-52s, with drop tests starting in January. In January 1961 a Vulcan visited the Douglas plant at Santa Monica, California, to ensure the modifications to the aircraft were electrically compatible with the missile. In Britain, compatibility trials with mockups started on the Vulcan.<ref name="Brooks114" />

Testing started with unpowered drop tests to ensure safe separating from the launch aircraft. Powered tests started in April 1962, but the test series went badly, with the first five trials ending in failure. The first fully successful flight occurred on 19 December 1962.<ref>{{cite web |url=http://www.astronautix.com/s/skyboltalbm.html |title=Skybolt ALBM |website=astronautix.com |access-date=11 July 2017 |archive-date=11 June 2017 |archive-url=https://web.archive.org/web/20170611062005/http://www.astronautix.com/s/skyboltalbm.html |url-status=dead }}</ref>