a> the blast wave from large incidence angles. shock tube work may resolve some of the Next in priority was Pam ceo Future aS analysis and em eee ae land-surface burst. Both electronic andPeclf-recording pressure p gages ob~ tained excellent, correlatable data. Observed was a precursor-type wave of limited extent — dying out at the close range of about 45 psi. Direct shock photography from the Mack tower failed. However, shock photography of the rocket trails from cameras on Runit should give pressure-distance data vertically over the burst and at horizontal range. Dragforce gages of model shapes recorded good loading data at two ranges in the clean Mach region. These models will be studied in the shock tube, data from which will be compared with that obtained on the shot. It is hoped that a correlation can be established to determine criteria for estimating or predicting drag forces on different targets by laboratory experiments. D ¢ ‘wemem 2 surface burst in the was instrumented with self-recording gages to obtain basic blast data on the ground surface and, with shock photography, to obtain pressure-distance data in the free air and along the water surface. The blast gages were placed on two lines f from GZ, 180° apart, towards Enlirikku and down the Eninman complex. At present there seems to be a difference in the pressure-distance curve plotted for each line. Further study may reveal a reason for this, or it may turn out to be no more than normal scatter of the data. The pressure- time records from both blast lines show distorted wave shapes similar to those associated with a precursor. Excellent photography of both high- and low-level rockets should give good data vertically over the burst and at horizontal range over a water surface. A study of blast diffraction was made on a concrete cubical target, instrumented with flush-mounted gages on the front and side walls and on the top. D was instrumented with surface gages to document the propagation of a precursor shock over a vegetated and over a cleared surface. The precursor was observed to be less severe over the vegetated surface than over the cleared area, showing later arrival times, higher overpressures, and lowerd c pressures. ED The was instrumented with self-recording surface gages to obtain basic blast data. Data were recorded which are expected, upon further analysis, to validate the height-of-burst curves for a fractional-kiloton device. Crater measurements were made on all ground-surface shots. Meas- urements consisted of aerial photography to obtain crater diameter by means of stereoptic analysis and lead-line sounding surveys for depth pro- file. Preliminary results give crater size as follows: (1 a Ee dD - 28 - 7 arwi! fan Zo