Question: Which British designer and publisher of tabletop and role-playing games coauthored Mutants in Orbit with Kevin Siembieda?

Context paragraphs:
Rifts (role-playing game): Rifts is a multi-genre role-playing game created by Kevin Siembieda in August 1990 and published continuously by Palladium Books since then.  "Rifts" takes place in a post-apocalyptic future, deriving elements from cyberpunk, science fiction, fantasy, horror, western, mythology and many other genres.

Kevin Siembieda: Kevin Siembieda (born April 2, 1956) is an American artist, writer, designer and publisher of role-playing games.

The Mechanoid Invasion: The Mechanoid Invasion (and its source books, supplements and sequels) was the first role-playing game from Palladium Books, conceived and written by Kevin Siembieda, with contributions from Erick Wujcik.

Palladium Books: Palladium Books is a publisher of role-playing games (RPGs) perhaps best known for its popular, expansive "Rifts" series (1990–present).  Palladium was founded April 1981 in Detroit, Michigan by current president and lead game designer Kevin Siembieda, and is now based in Westland, Michigan.  The company enjoys the support of a small but dedicated fanbase who praise its various game series for their innovative settings and ease of adaptability to various personal preferences, play styles, and power levels.

List of role-playing games by genre: This is a list of role-playing games, subdivided by genre (although many games do not fit clearly into one genre or another).  It does not include role-playing video games, MMORPGs, or any other video games with RPG elements.  Most of these games are tabletop role-playing games; other types of games are noted as such where appropriate.

History of live action role-playing games: Live action role-playing games, known as LARPs, are a form of role-playing game in which live players/actors assume roles as specific characters and play out a scenario in-character.  Technically, many childhood games may be thought of as simple LARPs, as they often involve the assumption of character roles.  However, the scope of this article concerns itself mainly with LARPing in a technical sense: the organized live-action role-playing games whose origins are closely related to the invention of tabletop role-playing games in America in the 1970s.

James Wallis (games designer): James Wallis is a British designer and publisher of tabletop and role-playing games.

Mutants in Orbit: Mutants in Orbit is an adventure and sourcebook for the "After the Bomb" and "Rifts" role-playing games, authored by James Wallis and Kevin Siembieda.  It was released by Palladium Books in March 1992.  The book deals with life of space colonies.  The setting is on the same time scale as the "After the Bomb" and "Rifts", only from the space colonies' point of view, but is in no way limited to that use.

Japanese role-playing game: Japanese role-playing games are role-playing games made in Japan.  Japanese role-playing games made their first appearance during the 1980s.  Today, there are hundreds of Japanese-designed games as well as several translated games.  Traditional RPGs are referred to as "tabletop RPGs" or "table-talk RPGs" ("TTRPG", or "TRPG") in Japan to distinguish them from the video role-playing game genre.

Heroes Unlimited: Heroes Unlimited is a superhero role-playing game written by Kevin Siembieda and first published by Palladium Books in 1984.  The game is based upon the Palladium Books Megaversal system and is compatible with other games that use the Palladium system.

Supporting paragraphs: Mutants in Orbit James Wallis (games designer)
Answer: James Wallis