The first step to building a rocket in garry's mod is to download smartsnap, weight advanced tool and sprops.
the reason for all of this is because number 1, your rocket thrusters and seats have to be aligned perfectly, doesnt matter about the seat that much but the thrusters have to be aligned if you want the result of going straight forward or if on an angle during liftoff go sideways, and forward.
Sprops is an abbreviation for Special Props, the reason you want this addon to in order to build your rocket is because it has very slick collision detection and is the addon i reccomend because i built my first rocket with it.
Now that we have all of that out of the way.
You want to start with your seat, if you want the true rocket experience i suggest you build your rocket with the Kerbal Space Program props adon because it is way better to use that if you want to make your rocket look like one you would build in Kerbal.
You would want to have your seat facing up towards the skybox, which is usually at the top of the map, basically when you sit down on a seat, the front of the seat is named the frt, frt is front for short,
you want your frt facing the top of the map because when you go forward you dont want to be sitting upright, thats not a very authentic rocket experience.
you then want to use the weight tool to make the seat lighter because when you start flying you dont want the seat to change your direction of flight.
now im gonna stfu and tell you how to make the actual rocket,
get the body from sprops, ideally a rectangular prism.
attach 4 thrusters evenly spaced out on the prop you use for the rocket.
and set the thrust power to 3000 for a very slow but very nasa-1969 esque lift off,
weld the seat to the other side of the rocket body opposite the thrusters like i told you near the beginning.
set your rocket upright or however you want (the idea is to put it upright on a proper surface made of concrete)
and start the countdown, 10, 9, 8, apple, 1, press the button you binded the thrusters to go forward and (BOOM) Liftoff!.

if you guys want me to explain anything about the guide or have any questions about what i am planning to do on the gmod community then you can email me at gaben@val-
but seriously, you can message me on steam and ask about said questions. thank you for reading.
-UniversalCorporations