[Spaceships] It seems that TL7 Chemical Rocket's acceleration is an overspec.

[Agemegos]

Originally Posted by Pectus Solentis

When I played Kerbal Space Program, only 1.2G-1.6G was sufficient to escape Kerbin. And I know that TWR of real-world Saturn V is 1.15G.



But at GURPS Spaceships p21, it says that TL7 Chemical Rocket provides 3G accelerations. It seems that it is an astounding overspec. It is greater than real-world TL7 Chemical Rockets, and it is greater than even TL9 HDEM Chemical Rocket (it provides 2G).

Are you taking into account that the reaction engines in Spaceships are 5% of the mass of the entire ship including propellant?

A Saturn V all-up launch weight was 3,270 US tons. Its first-stage engines, five Rocketdyne F-1, totalled 46.25 US tons mass. That's one seventieth of the vehicle mass (1.4%), not one-twentieth of vehicle mass (5%).

In Spaceships' terms a Saturn V had less than one third of a system of reaction engine, chemical rocket (TL7). Build it as a smaller system using the rules in Spaceships 7 on page 4 — then you will be complaining that the TL7 chemical rocket is actually slightly under-spec¹ and that a Saturn V cannot take off until it has burned part of its fuel and if you write house rules for the changing acceleration as ship mass diminishes.

___________

¹ TL7 chemical rockets in Spaceships have a thrust-to-weight ratio of 60 g₀, Rocketdyne F-1 engines had a thrust-to-weight ratio of 84 g₀.