  Launching large (> 1 g) well-characterized projectiles to velocities beyond
10 km/s is of interest for a number of scientific fields but is beyond the
reach of current hypervelocity launcher technology. This paper reports the
development of an explosively driven light-gas gun that has demonstrated the
ability to launch 8 mm diameter, 0.36 g magnesium projectiles to 10.4 km/s. The
implosion-driven launcher (IDL) uses the linear implosion of a pressurized tube
to shock-compress helium gas to a pressure of \SI{5}{\giga\pascal}, which then
expands to propel a projectile to hypervelocity. The launch cycle of the IDL is
explored with the use of down-bore velocimetry experiments and a
quasi-one-dimensional internal ballistics solver. A detailed overview of the
design of the 8 mm launcher is presented, with an emphasis on the unique
considerations which arise from the explosively driven propellant compression
and the resulting extreme pressures and temperatures. The high average driving
pressure results in a launcher that is compact, with a total length typically
less than a meter. The possibility to scale the design to larger projectile
sizes (25 mm diameter) is demonstrated. Finally, concepts for a modified launch
cycle which may allow the IDL to reach significantly greater projectile
velocities are explored conceptually and with preliminary experiments.
