Quote:
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).
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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.
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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.