  The rupture of rubber differs from conventional fracture. It is supersonic,
and the speed is determined by strain levels ahead of the tip rather than total
strain energy as for ordinary cracks. Dissipation plays a very important role
in allowing the propagation of ruptures, and the back edges of ruptures must
toughen as they contract, or the rupture is unstable. This article presents
several levels of theoretical description of this phenomenon: first, a
numerical procedure capable of incorporating large extensions, dynamics, and
bond rupture; second, a simple continuum model that can be solved analytically,
and which reproduces several features of elementary shock physics; and third,
an analytically solvable discrete model that accurately reproduces numerical
and experimental results, and explains the scaling laws that underly this new
failure mode. Predictions for rupture speed compare well with experiment.
