// satellite.java   compile    javac -cp . satellite.java
//                  execute    java  -cp . satellite

public class satellite
{
  double G = 6.674E-11;  // universal gavitational constant
  double R = 6.378E+6;   // radius of Earth  meter
  double cir = 40.07E+6; // 2 Pi R  meter
  double Me = 5.97E+24;  // mass of earth  kilograms
  double rot = 86400.0;  // 24 hours * 60 minutes * 60 seconds per day
  double Ve = 0.0;       // cir/rot  meter per second
  double d  = 0.0;       // satellite distance to earth center
  double v  = 0.0;       // velocity of satellite
  double Ms = 1000.0;    // mass of satellite
  double VeR = 0.0;      // Ve/R  ratio
  double vd  = 0.0;      // v/d   ratio
  double F = 0.0;        // gravity on satellite
  double Fs = 0.0;       // centripital force on satellite
  double err = 0.0;      // abs(F-Fs)
  double errs = 0.0;     // signed F-Fs
  double dm = 0.0;       // above earth miles
  double vm = 0.0;       // satellite velocity miles per hour

  public satellite()
  {
    System.out.println("satellite.java running");
    System.out.println("G = "+G);
    System.out.println("R = "+R+" meter");
    System.out.println("cir = "+cir+" meter");
    System.out.println("Me = "+Me+" kilogram");
    System.out.println("rot = "+rot+" seconds");
    System.out.println("Ms = "+Ms+" kilogram");

    Ve = cir/rot;
    System.out.println("Ve = "+Ve+" meters per second");
    VeR = Ve/R;
    System.out.println("Ve/R = VeR = "+VeR+" ratio");

    err = funct(4.0*R);
    err = funct(5.0*R);
    err = funct(6.0*R);
    err = funct(7.0*R);
    err = funct(6.5*R);
    err = funct(6.7*R);
    err = funct(6.6*R);

    dm = (d-R)/1.609E+3;
    System.out.println("miles above earth = "+dm+" miles");
    vm = v/2.237;
    System.out.println("satellite speed = "+vm+" miles per hour");

    System.out.println("satellite.java finished");
  } // end satellite

  double funct(double dg) // function to minimize
  {
    d = dg; // guess
    System.out.println("try d = "+d+" meter");
    vd = VeR;
    System.out.println("VeR = vd = "+vd+" ratio");
    v = vd * d;
    System.out.println("v = "+v+" try v  meter per second");
    F = G*Ms*Me /(d*d);
    System.out.println("first F=G*Ms*Me/d*d = "+F+" gravity joule");
    Fs = Ms*v*v/d;
    System.out.println("Fs=Ms*v*v/d = "+Fs+" joule centripital joule");
    err = Math.abs(F-Fs);
    System.out.println("err=abs(F-Fs) = "+err+" joule");
    errs = F -Fs;
    System.out.println("errs=F-Fs = "+errs);
    System.out.println(" ");
    return err;
  } // end funct
  public static void main (String[] args) 
  {
    new satellite(); 
  }
} // end satellite.java