Abstract: Production and trapping of small numbers of antiprotons for space applications are reviewed, setting the stage for antiproton-catalyzed microfission/fusion (ACMF) reactions as a source of propulsive power. A spacecraft designed around an ACMF engine has been designed. Details, including Isp, thrust, structural features, power systems, radiation shields, ion drivers, payload and system masses, are reviewed.

ACMF engine design

More info here.

If you want to know how close we are (by 'we' I mean mankind, obviously a small group of scientists deserve the credit) to producing enough antiprotons see the following website:

The Antimatter Factory at CERN in Switzerland