function dy=gravf(t,y);

G=6.67E-11;
M=5.97E24;
R=6375000;

m=90;
C=.42;
A=1;
rho=1.29;

dy(1,1)=y(2);
dy(2,1)=-G*M/(R+y(1)).^2+.5*rho*C*A*y(2).^2/m;