James Reasoner at Rough Edges has a review of Donald Westlake’s only science fiction novel, Anarchaos.
Donald E. Westlake isn’t that well-known for his science fiction, but he wrote one SF novel, ANARCHAOS, published by Ace Books in 1967 under the pseudonym Curt Clark. I’ve heard this book described as “Parker in space”, and I can kind of see why people would think that. The narrator/protagonist of ANARCHAOS, Rolf Malone, shares some traits with Parker, most notably his willingness to kill quickly and efficiently when he needs to in order to accomplish his goal.
He also points out that Anarchaos is available, along with some Westlake SF short fiction, in the anthology Tomorrow’s Crimes. It’s out of print but used copies are cheap.