TransferSim

• A Python program simulating transfer orbits between planets in the solar system
• Developed by Cutter Beck in collaboration with Chris Baxter and Sean Nuzio at Worcester Polytechnic Institute (WPI)

Getting Started

• Install Python 3.11 or higher
• Install all dependencies found in requirements.txt using the command pip install -r requirements.txt

Running Gravity Assists

• Open src/gravity-assists in a terminal
• Run python gravity-assists.py
  • In the current configuration, clicking +10 Days will increment the simulation by 10 days, and -10 Days will decrement the simulation by 10 days
• The following variables can be changed to set how the simulation runs
  • YEAR will set the starting year of the simulation
  • MONTH will set the starting month of the simulation
  • DAY will set the starting day of the simulation
  • BUTTONS determines whether the simulation will run with interactive buttons or if it will run automatically in the background and save a GIF
  • STEP determines how many days at a time the simulation will increase, this changes the value on the buttons as well
  • SUN_SCALE determines the relative size of the Sun in the simulation
  • PLANET_SCALE determines the relative size of the planets in the simulation
  • CRAFT_SCALE determines the relative size of the spacecraft in the simulation
  • TO_DRAW determines which planets will be drawn in the simulation
  • Changing flight_angle and delta_v will change the flight path of the spacecraft
  • Changing craft will change starting values of the spacecraft

Solving Lambert's Problem

• Open src/lamberts in a terminal
• Run python lambert.py
  • This calculates the 4 possible paths between two bodies, like Earth and Mars, based on a solved Lambert's problem
  • It prints the following in the current configuration:

    Point: (1.000 AU, 0.000 AU, 0.000 AU)
    Point: (-1.307 AU, 0.755 AU, 0.106 AU)
    Min TOF: 106.022 d
    Max TOF: 250.115 d
    

    • The points are the X, Y, and Z coordinates of each of the bodies (i.e. Earth and Mars)
    • The minimum and maximum time of flight (TOF) are the minimum and maximum time it would take to travel between the two bodies
• To edit the configuration, edit lines 348 and 353, which are Point objects, which represent the locations of the bodies

  class Point():
      def __init__(self, deg, semimajor, semiminor, rotX):
          """
          ### Parameters
          - deg: float, in degrees
          - semimajor: float, in AU
          - semiminor: float, in AU
          - rotX: float, in degrees
          """
          self.deg = deg * u.deg
          self.rad = self.deg.to(u.rad)
  
          self.rotX = rotX
          self.rotX_rad = ((90 - (90 + self.rotX)) * u.deg).to(u.rad)
  
          self.x = (semimajor * np.cos(self.rad) * np.cos(self.rotX_rad))
          self.y = (semiminor * np.sin(self.rad))
          self.z = u.au * (np.cos(self.rad) * np.sin(self.rotX_rad))
  
      def __str__(self):
          return f"Point: ({self.x:.3f}, {self.y:.3f}, {self.z:.3f})"
  

  348 point1 = Point(0, (1 * u.au), (0.98 * u.au), 0)
  353 point2 = Point(150, (1.52 * u.au), (1.51 * u.au), 7)
  

Viewing a Transfer Orbit Solved by Lambert's Problem

• Open src/lamberts in a terminal
• Run python transfer_orbit.py
  • This will show a 3D plot of the transfer orbit between two bodies, like Earth and Mars, based on a solved Lambert's problem
  • It also prints out the maximum and minimum time of flight (TOF) between the two bodies
• To edit the configuration,
  • Change the string START_YEAR to the starting year of the simulation
  • Change the string START_MONTH to the starting month of the simulation
  • Change the string START_DAY to the starting day of the simulation
  • Change planets_to_sim to be a list of names of the planets you want to simulate
    • The list of available planets to simulate can be seen in the dictionary PLANETS
  • Change STEP_DAYS to be the number of days you want to increment the simulation by
  • Change SUN_SCALE to be the relative size of the Sun in the simulation
  • Change PLANET_SCALE to be the relative size of the planets in the simulation
• To run the simulation manually, set ANIMATE to False, to run it in the background and save a GIF, set ANIMATE to True
  • anim_length determines the number of frames in the GIF; the number of days simulated can be inferred by anim_length * STEP_DAYS