In the mid ‘70s I read a story, probably novella length as I remember it being in an anthology, about a stardrive with an unexpected side effect.
Plot details I remember:
During construction, the designer of the stardrive carried out frequent demonstrations of its primary effect, which was to reduce gravity.
Prior to the launch of the ship, there was an attempt to stop it. The man in charge of the project got the crew to board and be ready for launch, then remotely launched it destroying the launch complex and killing both himself and the group opposing the launch.
Despite being warned to stay strapped in, the stardrive designer got up for a drink of water and was killed when the ship launched.
On arriving at a suitable planet, they sent down a scout craft to look for a landing site. The pilot reported seeing something amazing at a particular location, but then contact was lost.
Shortly thereafter the ship’s drive kicked in automatically to avoid a collision with an unknown object.
The ship then landed at the location reported by the scout, but saw nothing unusual in the location, and started setting up a base.
The scout which was lost earlier was then spotted flying past and crashing, killing the pilot – on examining the crash site they could find no clue as to where he had been for the last few months.
Disheartened, they decide to return to Earth, but when they arrive they find an unpopulated primitive world. They finally realise that every time they used the stardrive they had travelled into the past.