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checkpoint: thinking out loud
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‎assets/configs/real-scale/celestials.ron

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‎assets/configs/real-scale/constants.ron

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‎assets/configs/real-scale/satellites.ron

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‎assets/settings.ron

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// Simulation settings.
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(
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// Scale factors allow the simulation to produce realistic results in
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// non-real measurement scales. All calculations are self-consistent with
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// the real-scale units. Scale factors only affect visualizations.
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scale_factors: (
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// All spatial units of measure are multiplied by this scalar.
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space: 0.0001,
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// Number of simulation seconds that occur per system second.
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time: 1000.0,
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)
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physical_constants: (
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// Universal gravitational constant, G, as m^3 kg^-1 s^-2
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gravitational_constant: 6.67430e-11,
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// Speed of light, c, as m s^-1
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speed_of_light: 299792458.0,
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// 100 Julian years as seconds. A Julian year is exactly 365.25 days of
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// 86400 seconds each. This constant is useful for counting centuries in
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// time scales that have leap seconds or leap days.
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julian_century: 36525.0 * 86400.0,
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),
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// Physical characteristics of natural bodies.
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celestials: [
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// Units:
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// mass: kilograms
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// radius: meters (average)
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// rotation_period: seconds
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// gravitational_parameter: m^3/s^2
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// escape_velocity: m/s
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// ),
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(
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name: "Sun",
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mass: 1.9885e30,
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radius: 696340000.0,
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rotation_period: 0.0,
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gravitational_parameter: 1.32712440042e20,
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surface_gravity: 274.0,
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escape_velocity: 617700.0,
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),
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(
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name: "Earth",
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mass: 5.97237e24,
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radius: 6371000.0,
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rotation_period: 86164.09054,
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gravitational_parameter: 3.986004418e14,
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surface_gravity: 9.80665,
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escape_velocity: 11186.0,
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),
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(
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name: "Moon",
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mass: 7.342e22,
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radius: 1737100.0,
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rotation_period: 2360591.5104,
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gravitational_parameter: 4.9048695e12,
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escape_velocity: 2375.0,
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),
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(
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name: "Jupiter",
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mass: 1.8982e27,
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radius: 69911000.0,
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),
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],
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// Characteristics of artificial satellites.
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satellites: [
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// Units:
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// mass: total mass, as kilograms
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// dimensions: size of bounding box, as meters (x,y,z)
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// orbiting: the body the orbit is defined around [Earth, Moon]
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// semi_major_axis: meters
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// eccentricity: number between [0.0,1.0]
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// inclination: radians from the ecliptic
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// clock_type: on-board clock type [USO, CSAC, TCXO]
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// clock_frequency: tick frequency of the on-board clock, as Hz
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// clock_stability: Allan deviation at 1 second (or -1 for unknown)
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(
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name: "International Space Station (ISS)",
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mass: 419725.0,
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dimensions: [72.8, 108.5, 27.5],
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orbiting: "Earth",
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semi_major_axis: 6785000.0,
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eccentricity: 0.0008,
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inclination: 0.9012,
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clock_type: "USO",
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clock_frequency: 10e6,
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clock_stability: 1e-12,
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),
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(
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name: "GPS IIIA-6",
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mass: 2161.0,
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dimensions: [2.55, 2.24, 4.62],
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orbiting: "Earth",
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semi_major_axis: 26559800.0,
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eccentricity: 0.0,
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inclination: 0.9599,
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clock_type: "USO",
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clock_frequency: 10.23e6,
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clock_stability: -1.0,
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),
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(
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name: "GPS IIR-10",
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mass: 2032.0,
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dimensions: [2.44, 2.03, 5.18],
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orbiting: "Earth",
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semi_major_axis: 26559800.0,
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eccentricity: 0.0,
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inclination: 0.9599,
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clock_type: "USO",
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clock_frequency: 10.23e6,
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clock_stability: -1.0,
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),
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(
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name: "GPS IIF-3",
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mass: 1630.0,
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dimensions: [2.4, 2.0, 4.5],
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orbiting: "Earth",
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semi_major_axis: 26559800.0,
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eccentricity: 0.0,
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inclination: 0.9599,
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clock_type: "USO",
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clock_frequency: 10.23e6,
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clock_stability: -1.0,
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),
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(
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name: "GPS IIF-9",
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mass: 1630.0,
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dimensions: [2.4, 2.0, 4.5],
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orbiting: "Earth",
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semi_major_axis: 26559800.0,
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eccentricity: 0.0,
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inclination: 0.9599,
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clock_type: "USO",
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clock_frequency: 10.23e6,
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clock_stability: -1.0,
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),
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(
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name: "Lunar Reconnaissance Orbiter",
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mass: 1916.0,
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dimensions: [3.6, 3.6, 4.4],
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orbiting: "Moon",
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semi_major_axis: 1789000.0,
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eccentricity: 0.0093,
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inclination: 1.5533,
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clock_type: "USO",
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clock_stability: 1e-13,
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clock_frequency: 40e6,
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),
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(
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name: "LADEE",
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mass: 383.0,
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dimensions: [2.37, 2.37, 1.85],
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orbiting: "Moon",
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semi_major_axis: 1866200.0,
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eccentricity: 0.125,
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inclination: 1.57,
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clock_type: "USO",
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clock_frequency: 30e6,
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clock_stability: 1e-14,
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),
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(
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name: "CAPSTONE",
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mass: 25.0,
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dimensions: [0.34, 0.34, 0.64],
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orbiting: "Moon",
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semi_major_axis: 16800000.0,
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eccentricity: 0.1,
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inclination: 1.1,
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clock_type: "TCXO",
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clock_frequency: 1e6,
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clock_stability: 1e-12,
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),
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(
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name: "Chandrayaan-2 Orbiter",
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mass: 2379.0,
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dimensions: [3.2, 5.7, 2.1],
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semi_major_axis: 1800000.0,
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orbiting: "Moon",
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eccentricity: 0.014,
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inclination: 1.533,
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clock_type: "USO",
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clock_frequency: 38e6,
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clock_stability: 1e-13,
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),
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],
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)

‎docs/devlog/v0.2.2.md

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Maybe instead of spending so much time on the orbits, I should spend more time
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on... you know... figuring out the time dilation.
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# 2024-09-15
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Reference frames matter. A lot. I need to spend some time thinking about the
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problem of motion and time from the perspective of "how do we convert between
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reference frames".
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- https://orbital-mechanics.space/intro/reference-frames.html
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- https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/req/frames.html
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- https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/Tutorials/pdf/individual_docs/17_frames_and_coordinate_systems.pdf
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- https://nyxspace.com/nyxspace/MathSpec/models/gravity/
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- https://nyxspace.com/nyxspace/showcase/04_lro_od/
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In this context, the most important reference frames are
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1. Earth-centered Inertial (ECI).
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2. Moon-centered Inertial.
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3. Object-centered Body-fixed (for a given actor).
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I really don't want to have to code up my own reference frame transformations.
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This seals the deal with using Nyx. I'll apply scale factors to help with
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visualizations if I need to. I don't think there's a place for Particular
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anymore. Honestly this might also rule out the necessity for Avian as well.
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Since Nyx is a real astrodynamics crate, I'm basically locked into 3D as well.
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I put settings, constants, etc. in another RON file for safe keeping.

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