Heat　pumps　are　needed　to　provide　a　suitable　temperature　for　both　people　and　equipment　in　spacecraft.　This　paper　reports　on　work　designed　to　see　if　vapor　compression　heat　pumps,　in　particular,　can　be　expected　to　function　normally　in　space.　A　vapor　compression　heat　pump　was　built　and　tested　under　conditions　of　high　temperature　(70　degrees　C),　low　temperature　(0　degrees　C),　and　near-vacuum　(10(-4)　Pa).　It　was　found　that　the　coefficient　of　performance　of　this　heat　pump　was　2.99　at　both　high　and　low　temperatures,　and　was　2.1　under　near　vacuum　conditions.　The　results　suggest　that　vapor　compression　heat　pumps　are　suitable　for　use　in　space.