Tom Godwin 
Space Prison [EPUB ebook] 

The sound came swiftly nearer, rising in pitch and swelling in volume. Then it broke through the clouds, tall and black and beautifully deadly — the Gern battle cruiser, come to seek them out and destroy them. Humbolt dropped inside the stockade, exulting. For two hundred years his people had been waiting for the chance to fight the mighty Gern Empire… with bows and arrows against blasters and bombs!