Constants
Global physical and atmospheric constants for ballistic calculations.
This module defines scientific constants used throughout the ballistic calculations, including atmospheric model constants, physical constants, and runtime limits. All constants follow international standards (ISA, ICAO) where applicable.
Constant Categories
- Global atmosphere constants: Standard conditions and coefficients
- ISA metric constants: International Standard Atmosphere in metric units
- ICAO constants: International Civil Aviation Organization standards
- Conversion factors: Unit conversion constants
- Runtime limits: Computational bounds and validation limits
References
- ISA: https://www.engineeringtoolbox.com/international-standard-atmosphere-d_985.html
- ICAO: International Civil Aviation Organization standards
- Physical constants: NIST and other authoritative sources
Attributes:
| Name | Type | Description |
|---|---|---|
cStandardHumidity |
Final[float]
|
Standard relative humidity used in atmospheric calculations (%) |
cPressureExponent |
Final[float]
|
Pressure exponent constant for barometric formula (dimensionless) |
cStandardTemperatureC |
Final[float]
|
Standard temperature at sea level in Celsius (°C) |
cLapseRateKperFoot |
Final[float]
|
Temperature lapse rate in Kelvin per foot (K/ft) |
cLapseRateMetric |
Final[float]
|
Temperature lapse rate in metric units (°C/m) |
cStandardPressureMetric |
Final[float]
|
Standard atmospheric pressure at sea level (hPa) |
cSpeedOfSoundMetric |
Final[float]
|
Speed of sound coefficient in metric units (m/s per √K) |
cStandardDensityMetric |
Final[float]
|
Standard air density at sea level in metric units (kg/m³) |
cStandardTemperatureF |
Final[float]
|
Standard temperature at sea level in Fahrenheit (°F) |
cLapseRateImperial |
Final[float]
|
Temperature lapse rate in imperial units (°F/ft) |
cStandardPressure |
Final[float]
|
Standard atmospheric pressure at sea level (InHg) |
cSpeedOfSoundImperial |
Final[float]
|
Speed of sound coefficient in imperial units (fps per √°R) |
cStandardDensity |
Final[float]
|
Standard air density at sea level in imperial units (lb/ft³) |
cDegreesCtoK |
Final[float]
|
Celsius to Kelvin conversion constant (K) |
cDegreesFtoR |
Final[float]
|
Fahrenheit to Rankine conversion constant (°R) |
cDensityImperialToMetric |
Final[float]
|
Density conversion factor from imperial to metric units (kg/m³ per lb/ft³) |
cLowestTempF |
Final[float]
|
Minimum allowed temperature for atmospheric calculations (°F) |
cMaxWindDistanceFeet |
Final[float]
|
Maximum wind effect distance for computational limits (ft) |
module-attribute
¶
cStandardHumidity: Final[float] = 0.0
Standard relative humidity used in atmospheric calculations (%)
module-attribute
¶
cPressureExponent: Final[float] = 5.255876
Pressure exponent constant for barometric formula (dimensionless)
module-attribute
¶
cStandardTemperatureC: Final[float] = 15.0
Standard temperature at sea level in Celsius (°C)
module-attribute
¶
cLapseRateKperFoot: Final[float] = -0.0019812
Temperature lapse rate in Kelvin per foot (K/ft)
module-attribute
¶
cLapseRateMetric: Final[float] = -0.0065
Temperature lapse rate in metric units (°C/m)
module-attribute
¶
cStandardPressureMetric: Final[float] = 1013.25
Standard atmospheric pressure at sea level (hPa)
module-attribute
¶
cSpeedOfSoundMetric: Final[float] = 20.0467
Speed of sound coefficient in metric units (m/s per √K)
module-attribute
¶
cStandardDensityMetric: Final[float] = 1.225
Standard air density at sea level in metric units (kg/m³)
module-attribute
¶
cStandardTemperatureF: Final[float] = 59.0
Standard temperature at sea level in Fahrenheit (°F)
module-attribute
¶
cLapseRateImperial: Final[float] = -0.00356616
Temperature lapse rate in imperial units (°F/ft)
module-attribute
¶
cStandardPressure: Final[float] = 29.92
Standard atmospheric pressure at sea level (InHg)
module-attribute
¶
cSpeedOfSoundImperial: Final[float] = 49.0223
Speed of sound coefficient in imperial units (fps per √°R)
module-attribute
¶
cStandardDensity: Final[float] = 0.076474
Standard air density at sea level in imperial units (lb/ft³)
module-attribute
¶
cDegreesCtoK: Final[float] = 273.15
Celsius to Kelvin conversion constant (K)
module-attribute
¶
cDegreesFtoR: Final[float] = 459.67
Fahrenheit to Rankine conversion constant (°R)
module-attribute
¶
cDensityImperialToMetric: Final[float] = 16.0185
Density conversion factor from imperial to metric units (kg/m³ per lb/ft³)
Global atmosphere constants¶
| Constant | Description | Value | Unit / Notes |
|---|---|---|---|
cStandardHumidity |
Relative Humidity in percents | 0.0 | % |
cPressureExponent |
=gM/RL | 5.255876 | - |
cA0 |
Coefficient A0 | 1.24871 | - |
cA1 |
Coefficient A1 | 0.0988438 | - |
cA2 |
Coefficient A2 | 0.00152907 | - |
cA3 |
Coefficient A3 | -3.07031e-06 | - |
cA4 |
Coefficient A4 | 4.21329e-07 | - |
cA5 |
Coefficient A5 | 3.342e-04 | - |
ISA, metric prefer_units¶
| Constant | Description | Value | Unit / Notes |
|---|---|---|---|
cDegreesCtoK |
Celsius to Kelvin conversion | 273.15 | °K = °C + 273.15 |
cStandardTemperatureC |
Standard temperature in Celsius | 15.0 | °C |
cLapseRateMetric |
Metric lapse rate | -6.5e-03 | °C/m |
cStandardPressureMetric |
Standard pressure (metric) | 1013.25 | hPa |
cSpeedOfSoundMetric |
Speed of sound in metric | 331.3 | m/s |
cStandardDensityMetric |
Standard air density (metric) | 1.2250 | kg/m³ |
cDensityImperialToMetric |
Density conversion (imperial to metric) | 16.0185 | lb/ft³ to kg/m³ |
ICAO standard atmosphere¶
| Constant | Description | Value | Unit / Notes |
|---|---|---|---|
cDegreesFtoR |
Fahrenheit to Rankine conversion | 459.67 | °R = °F + 459.67 |
cStandardTemperatureF |
Standard temperature in Fahrenheit | 59.0 | °F |
cLapseRateImperial |
Imperial lapse rate | -3.56616e-03 | °F/ft |
cStandardPressure |
Standard pressure (imperial) | 29.92 | InHg |
cSpeedOfSoundImperial |
Speed of sound (imperial) | 49.0223 | fps |
cStandardDensity |
Standard air density (imperial) | 0.076474 | lb/ft³ |
Runtime limits constants¶
| Constant | Description | Value | Unit / Notes |
|---|---|---|---|
cLowestTempF |
Lowest temperature recorded | -130 | °F |
cMaxWindDistanceFeet |
Maximum wind distance | 1e8 | ft |