API Question Random Orbit Method

[sfpilot]

I need to make a method(or function i don't know which they are called in C++) that generates a random orbit around the inputted body. before i do so though i wanted to make sure i am not reinventing the wheel. if anyone has ever made this type of method before i would appreciate it if i could use it in my addon. with credit to the developer of the method. i am mostly hoping that someone else has made it because even though i probably could figure it out after a very long time, if someone else has already gone through the trouble to do such a thing why make a second one?

 

[TJohns]

Check out OCALC

Have a look at my OCALC program...with just a reference body mass, and the periapsis & apoapsis distances you can calculate orbital details quite easily. Just use random altitudes (as long as peri <= apo, and above the surface/atmosphere) and you've got your orbit! If it looks ok I can give you all the required calculations.

Trevor

 

[sfpilot]

that looks like exactly the kind of calculations i was looking for. Thank you Very much for helping me with this. it looks like if i could use these calculations in a method then it would make my addon a lot more versatile since it could work with absolutely any gravitational body. and judging by the variables it would output, it could all be stored in an ORBITPARAM structure.

 

[TJohns]

Here's some calculations

Just pulled this straight out of the source code...shouldn't be too hard to work out.

Note: just watch your units...I'm using km for altitudes

  { calculate Periapsis & Apoapsis }
  PeriRad.Value := rRadius.Value + PeriAlt.Value;
  ApoRad.Value := rRadius.Value + ApoAlt.Value;
  { calculate semi-major axis }
  SemiMajor.Value := (PeriRad.Value + ApoRad.Value) / 2.0;
  { eccentricity }
  Eccen.Value := (ApoRad.Value - PeriRad.Value) / (ApoRad.Value + PeriRad.Value);
  { mechanical energy }
  mu := 6.67259E3 * rMass.Value;
  Energy.Value := -mu / (2.0 * SemiMajor.Value);
  { period }
  secs := 2.0 * pi * sqrt(SemiMajor.Value * SemiMajor.Value * SemiMajor.Value / mu);
  Period.Value := secs;
  mins := trunc(secs / 60);
  secs := secs - (mins * 60);
  hours := trunc(mins / 60);
  mins := mins - (hours * 60);
  days := trunc(hours / 24);
  hours := hours - (days * 24);
  edtPeriod.Text := '';
  if (days > 0) then
    edtPeriod.Text := Format('%d d ', [days]);
  edtPeriod.Text := edtPeriod.Text + Format('%2.2d:%2.2d:', [hours, mins]);
  edtPeriod.Text := edtPeriod.Text + formatfloat('00.000', secs);
  { P }
  p.value := SemiMajor.Value * (1.0 - Eccen.Value * Eccen.Value);
  { H }
  h.value := sqrt(p.value * mu);
  { periapsis velocity }
  PeriVel.Value := h.value / PeriRad.Value;
  { apoapsis velocity }
  ApoVel.Value := h.value / ApoRad.Value;