ballistics-engine

High-performance ballistics trajectory engine with professional physics modeling.

Features

• Professional-grade trajectory calculations with multiple drag models (G1, G7, G8)
• Advanced physics including wind effects and atmospheric modeling
• Fast Rust implementation with Python bindings via PyO3
• Imperial units API (grains, fps, yards, inches) with automatic metric conversion

Installation

pip install ballistics-engine

Quick Start

from ballistics_engine import BallisticInputs, TrajectorySolver, WindConditions, AtmosphericConditions, DragModel

# Create ballistic inputs (all imperial units)
inputs = BallisticInputs(
    bc=0.505,                        # G7 BC
    bullet_weight_grains=168,        # grains
    muzzle_velocity_fps=2650,        # feet per second
    bullet_diameter_inches=0.308,    # inches
    bullet_length_inches=1.24,       # inches
    sight_height_inches=1.5,         # inches above bore
    zero_distance_yards=100,         # yards
    twist_rate_inches=11.25,         # inches per turn
)
inputs.drag_model = DragModel.g7()  # Use G7 drag model

# Create wind conditions (optional)
wind = WindConditions(
    speed_mph=10,                    # mph
    direction_degrees=90,            # degrees (0=headwind, 90=from right)
)

# Create atmospheric conditions (optional)
atmosphere = AtmosphericConditions(
    temperature_f=59,                # Fahrenheit
    pressure_inhg=29.92,             # inHg
    humidity_percent=50,             # percent
    altitude_feet=0,                 # feet
)

# Solve trajectory
solver = TrajectorySolver(inputs, wind=wind, atmosphere=atmosphere)
result = solver.solve()

# Print results
print(f"Max range: {result.max_range_yards:.1f} yards")
print(f"Time of flight: {result.time_of_flight:.2f} seconds")
print(f"Impact velocity: {result.impact_velocity_fps:.1f} fps")
print(f"Impact energy: {result.impact_energy_ftlbs:.1f} ft-lbs")

# Iterate through trajectory points
for point in result.points:
    print(f"Time: {point.time:.2f}s, X: {point.x:.1f}yd, Y: {point.y:.3f}yd, V: {point.velocity_fps:.1f}fps")

Units

The Python API uses imperial units for convenience:

• Mass: grains (gr)
• Velocity: feet per second (fps)
• Distance: yards (yd) and inches (in)
• Pressure: inches of mercury (inHg)
• Temperature: Fahrenheit (°F)
• Wind speed: miles per hour (mph)

All conversions to metric (used internally by the Rust engine) are handled automatically.

API Reference

BallisticInputs

Main input parameters for trajectory calculation.

Parameters:

• bc (float): Ballistic coefficient
• bullet_weight_grains (float): Bullet mass in grains
• muzzle_velocity_fps (float): Muzzle velocity in fps
• bullet_diameter_inches (float): Bullet diameter in inches
• bullet_length_inches (float): Bullet length in inches
• sight_height_inches (float): Sight height above bore in inches
• zero_distance_yards (float): Zero distance in yards
• shooting_angle_degrees (float): Uphill/downhill angle in degrees
• twist_rate_inches (float): Barrel twist rate (inches per turn)
• is_right_twist (bool): True for right-hand twist (default: True)

WindConditions

Wind parameters.

Parameters:

• speed_mph (float): Wind speed in mph (default: 0)
• direction_degrees (float): Wind direction in degrees (0=headwind, 90=from right, default: 0)

AtmosphericConditions

Atmospheric parameters.

Parameters:

• temperature_f (float): Temperature in Fahrenheit (default: 59)
• pressure_inhg (float): Barometric pressure in inHg (default: 29.92)
• humidity_percent (float): Relative humidity percentage (default: 50)
• altitude_feet (float): Altitude in feet (default: 0)

TrajectorySolver

Trajectory calculation engine.

Methods:

• __init__(inputs, wind=None, atmosphere=None): Create solver with inputs
• solve(): Calculate trajectory, returns TrajectoryResult

TrajectoryResult

Trajectory calculation results.

Properties:

• max_range_yards (float): Maximum range in yards
• max_height_yards (float): Maximum height in yards
• time_of_flight (float): Total flight time in seconds
• impact_velocity_fps (float): Impact velocity in fps
• impact_energy_ftlbs (float): Impact energy in ft-lbs
• points (list[TrajectoryPoint]): List of trajectory points

TrajectoryPoint

Individual point along trajectory.

Properties:

• time (float): Time in seconds
• x (float): Downrange distance in yards
• y (float): Vertical position in yards (relative to line of sight)
• z (float): Lateral position in yards
• velocity_fps (float): Velocity in fps
• energy_ftlbs (float): Kinetic energy in ft-lbs

DragModel

Drag model selection.

Static methods:

• DragModel.g1(): G1 drag model (flat base)
• DragModel.g7(): G7 drag model (boat tail)
• DragModel.g8(): G8 drag model (boat tail with meplat)

License

Dual licensed under MIT or Apache-2.0.

Links

• Homepage: https://ballistics.rs/
• Repository: https://github.com/ajokela/ballistics-engine
• Documentation: https://docs.rs/ballistics-engine