Notes from Independent Study Meeting
                      Feb 14, 2022

Present: Richmond, Dayal

  - Dayal shows the results of a sail placed into an initially
          circular orbit around the Sun

          - if no photon pressure, sail continues to orbit in a circle

          - if add photon pressure, sail makes an orbit, but
                 not quite a right shape: start at x=+1.5E11 m,
                 go to y=+1.7E11 m (good so far), but then 
                 the minimum x value is about -1.6E11, and the
                 then when it returns to the positive x-axis,
                 it is back at starting point x=+1.5E11.

          - in other words, it looks as if the size of the orbit grew
                 for the first two quadrants, but then shrank for the
                 second two quadrants

          - we expect the radius to increase steadily all the way around 
                 the orbit

  - goals for next meeting (Thu, Feb 17): 
   
          - compute the size of a thin-film sail needed to take
                 a payload the mass of Voyager 1 to Saturn in 2 years

          - investigate code for a possible error in the sign of 
                 acceleration components.  If necessary, print out
                 photon accel values ax, ay together with other
                 quantities on each timestep

          - modify code so that one can set it to print out values
                 every N timesteps, rather than every timestep