changes made by lookang:

assignment completed by lookang following Larry Engelhardt useful PDF
made visibility of the flame by adding ( t>0) && ( burnRate>0)
added thrust = (burnRate*v)
added analytic solution
added gravity g = gs/((1+y/Rearth)*(1+y/Rearth));
added gravityforce =-(m+mFuel)*g;
added air resistance in fixed relationship
if (y<44307){
Temperature= Temperatureo- L*y;
Pressure = Pressureo*Math.pow((Temperature/Temperatureo),(g*Molarmassair/R*L*y));// need this to avoid bug in calculation when Pressure <0
}
else if (y>44307){
 Temperature=0.0065;
 Pressure = 0.001;
 }

densityair=Pressure*Molarmassair/(R*Temperature);
DragForce = 0.5*densityair*area*Cd*vy*vy;
added scale to draw forces on rocket world view
added bottom panel as in my usual layout
added timer

enjoy!