 Further missions depended on the readiness of the Lunar Module . Apollo 8 was planned as the " D " mission , to test the LM in a low Earth orbit in December 1968 by James McDivitt , David Scott and Russell Schweickart , while Borman 's crew would fly the " E " mission , a more rigorous LM test in an elliptical medium Earth orbit as Apollo 9 , in early 1969 . 
