﻿ Mathematical and Physical Constants

# Mathematical and Physical Constants

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The Constants object gives users access to basic mathematical and physical constants via a static object that is available in all Mission Plans. The provided constants encompass those commonly found within the realms of electricity and magnetism, orbital mechanics, and fundamental mathematics. The Constants object can only be accessed through scripting and all of its properties are read-only.

## Available Constants

The values of the mathematical and scientific constants and their sources are listed in the table below.

 Constant Name FreeFlyer Property Value Units Description Source Astronomical Unit AU 1.49597870699999988e8 One AU is defined as the mean distance between the center of the Earth and the center of the Sun. NASA JPL Boltzmann’s Constant 1.380649e-29 Boltzmann's constant defines the relation between absolute temperature and kinetic energy in a molecule of an ideal gas. BIPM 2019 International System of Units Speed of Light 2.99792458e5 The speed of light is defined as the speed that light travels in a vacuum. NASA JPL e e 2.718281828459046 Unitless The constant e, is defined based on the following limit: Derived from a mathematical equation Gravitational Constant 6.67430e-20 The gravitational constant is the constant used in Newton's universal gravitation calculations. NASA JPL Golden Ratio GoldenRatio 1.618033988749895 Unitless Defined as the greater root of the polynomial which is equal to Derived from a mathematical equation Planck’s Constant 6.62607015e-40 Planck's constant is the quantum of electromagnetic action that relates a photon's energy to its frequency. BIPM 2019 International System of Units pi Pi 3.141592653589793 Unitless The constant pi, is defined as a circle's circumference C divided by its diameter d. Derived from a mathematical equation Solar Constant SolarConstant 1358.0 The Solar Constant, also known as Mean Solar Flux, is the mean Total Solar Irradiance (TSI) at one AU (astronomical unit). This parameter is used in Solar Radiation Pressure (SRP) modeling. Space Mission Analysis and Design (Larson and Wertz) Stefan-Boltzmann Constant StefanBoltzmann 5.670374419184433e-02 The Stefan-Boltzmann constant is defined based on the following combination of other constants: Derived from other constants

## Using the Constants Object

The Constants object can only be accessed through scripting. Users can access the values of different constants through the static properties of this object. The values of the constants can be used anywhere a Variable object could be used.

 // Set Variable to Constant value Variable pi = Constants.Pi; Variable k  = Constants.Boltzmann;   Spacecraft Spacecraft1; Spacecraft1.OrbitWizardGeoSynchSetup(Spacecraft1.Epoch, Constants.Pi, 0, 0, 0); Spacecraft1.A = Constants.AU;   // Override Constant values with Static Methods Constants.SetAU(149597871); Constants.SetSolarConstant(1366.1);