This Phase II project was directed towards meeting the objectives of the Deepstar consortium project entitled: ?Seismic-while-drilling to improve pore pressure prediction ahead of the bit.? The objective is a real-time display of the formation from the bit to 300 m (1000 ft) below the bit at a resolution of 15-m. A downhole hydraulic impulse tool for reverse vertical seismic profiling and look-ahead seismic while drilling was developed and demonstrated successfully in a well. The HydroSeis? tool generates a stream of powerful impulses below the bit by periodically blocking mud flow to the bit. The tool utilizes a mud-activated poppet valve, located directly above the bit, that rapidly closes for about 3 ms and then rapidly reopens for about 50 to 100 ms. The valve creates pressure pulses at frequencies from about 10 to 20 Hz. The HydroSeis? tool is equipped with a frequency modulator device that varies the pulse frequency from minimum to maximum over a period of about 5 seconds. This provides a periodic broad-band point seismic source at the bit.