Our Lady of the Stars. The Prospectors, #4

Cat Dads in outer space. When Ahab hurts his knee Gert tries everything but nothing works. Luckily they manage to contact nearby hospital ship Our Lady of the Stars, which say they can help.  They dock with the ship and Ahab is taken by a robot nurse to see the doctor. While Gert waits he sees Sunny's spaceship arriving and goes to investigate. When Gert discovers the real and sinister purpose of the hospital ship it's almost too late, but help comes from an unexpected source.