Generating short X-ray pulses using a dipole magnet kicker was demonstrated at the Advanced Photon Source. A 4-ps long pulse containing about 10% of the flux from a bunch was captured in the experiment. The pulse could be even shorter for different machines. In this paper we estimate that a sub-picosecond pulse can be obtained from the proposed National Synchrotron Light Source II. A 100 fs pulse can be produced if we combine the lower momentum compaction method and the vertical kick method. Flux and pulse length are compared for different schemes.