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APPENDIX H

M26/M28 ROCKET CREST CLEARANCE TABLES


The purpose of these tables is to provide leaders a planning tool which allows them to assess the impact of intervening crests on rocket trajectories. Then were developed by the MLRS project office of U.S. Army Missile Command (MICOM) for the U.S. Army Field Artillery School.


Assumptions

These tables establish minimum planning ranges for launchers in specific firing areas which ensure that rockets will not only clear a crest, but that warhead event will not occur until the crest is cleared. The tables use five launch altitudes: sea level, +400 m, +800 m, +1200 m, and +3048 m. They do not represent an absolute launcher ballistic algorithm and should not be used as a firing solution safety check. The tables are based on several assumptions and conditions:

  • European rockets or those with lot number VGT072 or higher were used. These lots have more aerodynamic fins and therefore produce longer ranges with lower trajectories.
  • A warhead event will not occur until the crest is cleared.
  • Standard atmospheric conditions with 99% global wind conditions (head and tail) were applied to account for low level winds. Rockets were conditioned both cold and hot to account for temperature extremes.
  • 3.3 sigma range and height dispersion errors were used to account for occasion-to-occasion (bias) and round-to-round (precision) errors.
  • 100 m altitude subtracted to account for vegetation and terrain effects.
  • Ballistic algorithm version 6.06 with no high QE mode.

Procedures

There are two entry arguments for the tables: Range (to crest) and Angle of Site (to crest). If the angle of site cannot be directly measured, then leaders can calculate it by using the mil relation formula below:

If the actual target location and altitude are known, the angle of site can be modified to account for the differences in launch and target altitude using the formula below:



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