Space warfare is a main theme and central setting of science fiction that can trace its roots back to classical times, and to the "future war" novels of the 19th century.
Science writer and spaceflight popularizer Willy Ley claimed in 1939 that bullets would be a more effective weapon in a real space battle.
For example, the space warships in the Stargate television series do battle with directed-energy weapons that are described as being powered by a fictional metal, called naquadah.
[4][better source needed] It has been calculated that a force on the order of 1032 joules of energy, or roughly the total output of the sun in a week, would be required to overcome the gravity that holds together an Earth-sized planet.
[citation needed] The destruction of Alderaan in Star Wars: Episode IV – A New Hope is estimated to require 1.0 × 1038 joules of energy, millions of times more than would be necessary to break the planet apart at a slower rate.
[citation needed] Though the details do differ between various science fiction intellectual properties (IPs for short), classes of ships are most commonly based on those of World War II.
Prominent examples include the X-wing from Star Wars, the Colonial Viper from Battlestar Galactica and the Starfury from Babylon 5.
Griffith's last "future war" story was The Lord of Labour, written in 1906 and published in 1911, which included such technology as disintegrator rays and missiles.
Joe Haldeman's The Forever War, was partly a response to or a rebuttal of Robert A. Heinlein's Starship Troopers, wherein space warfare involved the effects of time dilation and resulted in the alienation of the protagonists from the human civilization on whose behalf they were fighting.
[citation needed] Science fiction writers from the end of World War II onwards have examined the morality and consequences of space warfare.
Opposing them are Murray Leinster's "First Contact" (1945), Barry Longyear's "Enemy Mine," Kim Stanley Robinson's "The Lucky Strike," Connie Willis' "Schwarzchild Radius," and John Kessel's "Invaders.
Garrett P. Serviss' 1898 newspaper serial "Edison's Conquest of Mars" was inspired by Wells and intended as a sequel to "Fighters from Mars," an un-authorized and heavily altered Edisonade version of The War of the Worlds[14][full citation needed] in which the human race, led by Thomas Edison, pursues the invading Martians back to their home planet.
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.
[18] Other examples of military space opera are the Battlestar Galactica franchise and Robert A. Heinlein's 1959 novel Starship Troopers.
Writers would submit stories in both genres,[20] and science-fiction magazines sometimes mimicked Western cover art to showcase parallels.