David Colby 
Shattered Sky [EPUB ebook] 
Lunar Cycle Book 2

Publishers Weekly calls Lunar Cycle Book 1 “Appealingly reminiscent of an updated Heinlein juvenile, it’s a story of wartime bravery, principles, and self-sacrifice.”
The year: 2068
The place: The war-torn and ecologically devastated Earth.
The objective: Survive.
Sixteen-year-old Drusilla Zhao has done the impossible and escaped the meat grinder of space warfare alive. Now she and her only remaining comrade, Jillian, are about to be rotated right back into the firing line, and away from Dru’s love, Sarah.