  We demonstrate that a common-line method can assemble a 3D oversampled
diffracted intensity distribution suitable for high-resolution structure
solution from a set of measured 2D diffraction patterns, as proposed in
experiments with an X-ray free electron laser (XFEL) (Neutze {\it et al.},
2000). Even for a flat Ewald sphere, we show how the ambiguities due to
Friedel's Law may be overcome. The method breaks down for photon counts below
about 10 per detector pixel, almost 3 orders of magnitude higher than expected
for scattering by a 500 kDa protein with an XFEL beam focused to a 0.1 micron
diameter spot. Even if 10**3 orientationally similar diffraction patterns could
be identified and added to reach the requisite photon count per pixel, the need
for about 10**6 orientational classes for high-resolution structure
determination suggests that about ~ 10**9 diffraction patterns must be
recorded. Assuming pulse and read-out rates of 100 Hz, such measurements would
require ~ 10**7 seconds, i.e. several months of continuous beam time.
