Well first of all, the Space Shuttle program ended a few years ago, and none have been launched since then.
The Shuttle never went to places that were properly referred to as "outer space". When they flew, the Space Shuttles went to low Earth orbit, where the acceleration of gravity is roughly 85% of its value on the Earth's surface.
So a Shuttle that weighed 20 million Newtons on the launch pad weighed roughly 17 million Newtons while in orbit.