  To reach the flyer plate velocities in excess of 1000km/sec required for
impact ignition, it is proposed to combine the ablation acceleration of a dense
hydrogen jet by its isentropic compression in a convergent Prandtl-Meyer flow,
magnetically insulated by the Nernst effect against the wall confining the flow
to reduce friction losses. A flyer plate placed at the front of the flow can
there be accelerated to much higher velocities.
