Challenger

 was an American space shuttle that blew up 73 seconds after take-off on 28th January 1986. The eighth Doctor once said that its explosion affected the odds NASA gave for the there being a "major problem" with the space shuttles. Before the explosion, NASA said there was a one-in-a-hundred-thousand chance of there being a malfunction; afterwards, those odds went up to one-in-a-hundred. (EDA: Father Time)

When Isaac Summerfield first met Joel Mintz in 1983, he asked him where he was when Challenger blew up. (NA: Return of the Living Dad)