Soyuz 7K-ST No.16L, sometimes known as Soyuz T-10a or Soyuz T-10-1, was an unsuccessful Soyuz mission intended to visit the Salyut 7 space station, which was occupied by the Soyuz T-9 crew. However, it never finished its launch countdown; the launch vehicle was destroyed on the launch pad by fire on 26 September 1983. The launch escape system of the Soyuz spacecraft fired six seconds before the launch vehicle exploded, saving the crew. This is the only time a launch escape system has been fired before launch with a crew aboard.
The Soyuz T-10-1 explosion would also remain the only instance of a Russian crewed booster accident in 35 years, until the Soyuz MS-10 flight aborted shortly after launch on 11 October 2018 due to a failure of the Soyuz-FG launch vehicle boosters.