  We study explosions of stars using a one-dimensional Lagrangian hydrodynamics
code. We calculate how much mass is liberated as a function of the energy of
explosion for a variety of pre-explosion stellar structures and for equations
of state with a range of radiation-to-gas pressure ratios. The results show
that simple assumptions about the amount of mass lost in an explosion can be
quite inaccurate, and that even one-dimensional stars exhibit a rich
phenomenology. The mass loss fraction rises from about 50 to 100 per cent as a
function of the explosion energy in an approximately discontinuous manner.
Combining our results with those of other, more realistic models, we suggest
that Nova Scorpii (J1655-40) may have experienced significant mass fallback
because the explosion energy was less than the critical value. We infer that
the original progenitor was less than twice the mass of today's remnant.
