A major setback occurred on October 24, when a rocket explosion killed over 100 people, including Chief Marshal of Artillery Mitrofan Nedelin, in what is now called the Nedelin catastrophe. This was one of the worst disasters in the history of spaceflight. It involved a rocket that was not designed by Korolev, and was not necessary for the Vostok programme; the rocket was by rival designer Mikhail Yangel, intended to be a new generation of intercontinental ballistic missiles. It would be two weeks before work on the Vostok programme continued, and it was realised that the original target of a December crewed launch was unrealistic.