The Outward Urge is a science fiction fix-up novel by British writer John Wyndham. It was originally published with four chapters in 1959. A fifth chapter, originally published in 1961 as the separate short story "The Emptiness of Space", was included in later versions. The novel's stated authorship has a peculiar history. It was published as co-written by John Wyndham and Lucas Parkes, but they were different pen-names for the same writer. He had used the pen-name Lucas Parkes earlier in his career. Unlike most of Wyndham's novels, The Outward Urge was conventional hard science fiction and his publishers decided that they wanted to use the Wyndham and Parkes byline because it was "not your usual Wyndham style". Source: Wikipedia (en)