We played the first session of a "rockets and rayguns" pulp sci-fi game using a modified version of Rocket Age for 5e. The characters were:
Jones: human, ex-soldier
Lor' el-Am: Hadozee engineer
Mitchell: another human and ex-Space Marine
Trzkt: Vrusk scientist
All were marking time in Ziszkhar, a minor spaceport and domed city of Marva, when Trzkt was approached by another Vrusk named Niszk Zrnn, who was acting as an agent for an insurance claims for a big New Terran shipping insurance firm. The firm was interested in hiring a crew for a salvage mission in the Belt. Niszk thought Trzkt might know a suitable group. In fact, she did, and they agreed to meet the insurance agent.
Arlik Taine told them that his company was preparing to pay out a significant amount on the Aurora Queen, a new luxury spaceliner that had mysteriously disappeared in the Belt, just days from Marva. It's inaugural cruise with only a small group of passengers had been a cruise out to Kronion's moons. It was coming back when contact was lost. A prospector in the belt had a caught a glimpse of a derelict in the distance that might by the Queen, so Taine was willing to pay to have it checked out.
He added that there was a famous archeologist on board, Dr. Brennan Carter, who was returning from an expedition to one of the nameless moons of Vurania, with a treasure in exotic gems.
The crew was outfitted with an aging but serviceable cruiser, and they set out for the Belt, to the coordinates extrapolated from the prospector's sighting. They find the ship, powerless and tumbling through space. Attaching themselves with a magnetic grapple, they went inside. There was evidence of some bloody conflict in gruesome stains on walls and doors, but no bodies. In the ship's control room they found the bleeding and concussed officer in the uniform of the line, Captain Cyril Falconer. He tells them there is an invisible monster on the ship that has been slaughtering the crew and passengers!