Several subsets of military science fiction overlap with space opera, concentrating on large-scale space battles with futuristic weapons. At one extreme, the genre is used to speculate about future wars involving space travel, or the effects of such a war on humans; at the other, it consists of the use of military fiction plots with some superficial science fiction trappings. The term "military space opera" is occasionally used to denote this subgenre, as used for example by critic Sylvia Kelso when describing Lois McMaster Bujold's Vorkosigan Saga. Another example of military space opera would be the Battlestar Galactica franchise and Robert A. Heinlein's 1959 novel "Starship Troopers".