# Accession Number:

## AD0911383

# Title:

## Comparison of Approximate Methods for Airborne Gunnery Ballistics Calculations

# Descriptive Note:

## Technical rept. Apr-Oct 1971

# Corporate Author:

## TEXAS UNIV AT AUSTIN APPLIED RESEARCH LABS

# Personal Author(s):

# Report Date:

## 1973-04-01

# Pagination or Media Count:

## 109.0

# Abstract:

Practical bounds on computer capacity and computation time dictate a need for simplified methods of airborne gunnery ballistics computation, particularly under conditions which involve large ballistic yaw. The projectile trajectory data needed for on-board solution of the fire control problem can be obtained in two ways 1 trajectory computation on board the aircraft, 2 curve fitting precomputed trajectory data. This report contains a comparison of two approaches to on-board trajectory computation and polynomial curve fitting of precomputed trajectory data. When the yaw-drag and windage-jump corrections are used with the Siacci method, a closed-form solution to the ballistic trajectory equations is obtained. This method is almost as accurate as the simplified set of equations above, except for time-of-flight calculations. It is sufficiently accurate for air-to-air applications out to a range of approximately 3000 ft. If time of flight is not important, as, for example, in air-to-ground applications, then this method yields results of sufficient accuracy out to moderate ranges for most geometries. Also, this method appears to be 20 to 100 times as fast as point-mass integration and 500 to 1500 times as fast as numerical integration of the Eglin approximate equations of motion. A method of polynomial curve fitting of ballistic lead angles for air-to-ground applications is presented. This method may be useful in situations where onboard calculations are not possible.

# Descriptors:

- *TERMINAL BALLISTICS
- *EXTERIOR BALLISTICS
- *AERIAL GUNNERY
- *AIRCRAFT AMMUNITION
- KINEMATICS
- VELOCITY
- DENSITY
- NUMERICAL INTEGRATION
- ERRORS
- AERIAL TARGETS
- DRAG
- FLIGHT PATHS
- RANGE TABLES
- MAGNUS EFFECT
- FIRE CONTROL COMPUTERS
- AIRCRAFT GUNS
- AIRCRAFT FIRE CONTROL SYSTEMS
- FORCE(MECHANICS)
- AIR TO AIR
- PROJECTILE TRAJECTORIES
- LIFT
- SPINNING(MOTION)
- JET FIGHTERS
- AIR TO SURFACE
- YAW
- DEFLECTION
- ACCURACY

# Subject Categories:

- Numerical Mathematics
- Ammunition and Explosives
- Fire Control and Bombing Systems