orbit_calc

defmodule OrbitCalc do
  @moduledoc """
  Documentation for `OrbitCalc`.
  """

  @doc """
  Hello world.

  ## Examples

      iex> OrbitCalc.hello()
      :world

  """

  alias Decimal, as: D

  @earth_mass D.new("5.9722E+24")
  @earth_radius D.new("6.371E+6")
  @g_const D.new("6.674301515151515E-11")

  def circular_earth_orbit(height, precision) do
    D.set_context(%D.Context{D.get_context | precision: precision, rounding: :half_up})
    radius = D.add(height, @earth_radius)
    speed = D.mult(@g_const, @earth_mass) |> D.div(radius) |> D.sqrt()
    time = D.from_float(:math.pi) |> D.mult(2) |> D.mult(radius) |> D.div(speed)
    %{:speed => speed, :time => time}
  end
end