User:TomPN

Hi! I'm TomPN, and I'm an avid fan of Kerbal Space Program.

Comms satellites

For any of you out there using RemoteTech, here's a little fact that I've just worked out:

In order for a three-satellite network to provide constant uplink to a particular spot, the orbital altitude of the satellites must be greater than or equal to the radius of the body they are orbiting.

Orbital calculator

I'd like to upload my (now upgraded) program for calculating whether you should use a Hohmann transfer or a Bi-elliptical transfer, but it's an exe so I can't. I can post the source code, however, so here goes (You'll need a C++ emulator (can be found online) or compiler (can be downloaded) to run the code):

#include <math.h>
#include <iostream>
#include <cstdlib>

using namespace std;

void bi_elliptical_delta_v (double current_orbit, double bi_elliptical_apoapsis, double final_orbit, double standard_gravitational_parameter, double planet_radius)
{
  double delta_v_1, delta_v_2, delta_v_3, delta_v_total;
  delta_v_1 = sqrt (((2*standard_gravitational_parameter)/current_orbit)-((2*standard_gravitational_parameter)/(current_orbit + bi_elliptical_apoapsis))) - sqrt (standard_gravitational_parameter/current_orbit);
  delta_v_2 = sqrt (((2*standard_gravitational_parameter)/bi_elliptical_apoapsis)-((2*standard_gravitational_parameter)/(final_orbit + bi_elliptical_apoapsis))) - sqrt (((2*standard_gravitational_parameter)/bi_elliptical_apoapsis)-((2*standard_gravitational_parameter)/(current_orbit + bi_elliptical_apoapsis)));
  delta_v_3 = sqrt (((2*standard_gravitational_parameter)/final_orbit)-((2*standard_gravitational_parameter)/(final_orbit + bi_elliptical_apoapsis))) - sqrt (standard_gravitational_parameter/final_orbit);
  delta_v_total = delta_v_1 + delta_v_2 + delta_v_3;
  string fore;
  if (current_orbit < final_orbit)
  {
    fore = "prograde";
  }
  else if (current_orbit > final_orbit)
  {
    fore = "retrograde";
  }
  cout << "Bi-elliptcal transfer stats:" << endl << "Bi-elliptical apoapsis: " << bi_elliptical_apoapsis - planet_radius << "m above sea level" << endl << "Burn 1 = " << delta_v_1 << "m/s prograde" << endl << "Burn 2: " << delta_v_2 << "m/s " << fore << endl << "Burn 3 = " << delta_v_3 << "m/s retrograde" << endl << "Total delta v: " << delta_v_total << "m/s" << endl;
}

void hohmann_delta_v (double current_orbit, double final_orbit, double standard_gravitational_parameter)
{
  double delta_v_1, delta_v_2, delta_v_total;
  delta_v_1 = sqrt (((2*standard_gravitational_parameter)/current_orbit)-((2*standard_gravitational_parameter)/(current_orbit + final_orbit))) - sqrt (standard_gravitational_parameter/current_orbit);
  delta_v_2 = sqrt (((standard_gravitational_parameter)/final_orbit)) - sqrt (((2*standard_gravitational_parameter)/final_orbit)-((2*standard_gravitational_parameter)/(current_orbit + final_orbit)));
  delta_v_total = delta_v_1 + delta_v_2;
  string fore;
  if (current_orbit < final_orbit)
  {
    fore = "prograde";
  }
  else if (current_orbit > final_orbit)
  {
    fore = "retrograde";
  }
  cout << "Hohmann transfer stats:" << endl << "Burn 1 = " << delta_v_1 << "m/s " << fore << endl << "Burn 2: " << delta_v_2 << "m/s " << fore << endl  << "Total delta v: " << delta_v_total << "m/s" << endl;
}

int main ()
{
  cout << "Orbital transfer calculator v2.0\nWritten by TomPN\n18/01/2016\n" << endl;
  double planet_mass;
  cout << "Please enter the mass of the body you are in orbit around (in kilograms x10^20): ";
  cin >> planet_mass;
  double mass_multiplier = 100000000000000000000.0;
  planet_mass *= mass_multiplier;
  double standard_gravitational_parameter = planet_mass*0.0000000000667;
  double planet_radius;
  cout << "Please enter the radius of the body you are in orbit around (in metres): ";
  cin >> planet_radius;
  double current_orbit;
  cout << "Please enter your current orbital altitude above sea level (in metres): ";
  cin >> current_orbit;
  current_orbit += planet_radius;
  double final_orbit;
  cout << "Please enter your desired orbital altitude above sea level (in metres): ";
  cin >> final_orbit;
  final_orbit += planet_radius;
  double sphere_of_influence;
  cout << "Please enter the radius of the sphere of influence of the body that you are\n currently in orbit around (in metres): ";
  cin >> sphere_of_influence;
  cout << endl;
  double bi_elliptical_apoapsis = (0.9*(sphere_of_influence - final_orbit)) + final_orbit;
  hohmann_delta_v (current_orbit, final_orbit, standard_gravitational_parameter);
  cout << endl;
  bi_elliptical_delta_v (current_orbit, bi_elliptical_apoapsis, final_orbit, standard_gravitational_parameter, planet_radius);
  cout << endl;
  system ("PAUSE");
  return 0;
}

The calculator can be used for raising or lowering your orbit. Please do not edit the source code. If you find an error, point it out to me and I will attempt to fix it.