The facts: The actual Service Propulsion System of the Apollo C/SM was a small low-efficiency hypergolic engine with 91 kN thrust and a specific impulse of 319 seconds. The J-2 rocket engine on the Saturn V was a high efficiency rocket engine with 421 seconds Isp, and 486 kN of thrust. The Wolfhound is the in-game SPS analogue. It has an Isp of 412 seconds and a thrust of 375 kN.  The Skiff is the in-game J-2 analogue. It has an Isp of 330 seconds and a thrust of 300 k