A design for an Astronaut Maneuvering Unit (rocketpack for moving astronauts around in space) from Boeing, 1966. The Manned Maneuvering Unit briefly used on the Shuttle program used compressed nitrogen gas for thrusters. Low specific impulse, but cool exhaust. The AMU *almost* used during the Gemini program used hydrogen peroxide monopropellant… improved Isp at the exhaust of a hot steam exhaust. This Boeing design says “screw that safety crap” and uses hydrazine monopropellant. Sure the Isp is improved even further, at the cost of *really* hot exhaust gas, and nicely toxic fuel.