#sim game

KSP allows you to build rockets almost lego style out of modular parts. The game does include a few tutorials which I do recommend you try (imperfect though they are), but here's a few other helpful tips:

there are two ways to attach parts: node attach (connecting parts via those green and black spheres that appear when you're holding a part) and surface attach (connecting parts where your mouse is). If a part can be surface attached, it will always prioritize that over node attach. So if you're trying to put together a rocket tank and the tank keeps trying to attach to the other tank wrong, you have to change your camera angle so that the nodes can come together without your mouse going over the part. The alternative is to hold the ALT key, which will force the part to attach only to a node.

The C key and the X key control angle snap and symmetry mode. There's also buttons for these on the lower left of the u.i. Symmetry is a must for building rockets.

There's three main types of engines: Liquid Fuel rocket engines, which require separate fuel tank parts burning Liquid Fuel and Oxidizer, Solid Rocket Boosters, which contain their own fuel and can not use fuel tanks or be throttled, and Jet Engines, which burn liquid fuel and atmospheric oxygen from air intakes, at a high efficiency.

There's also the ion engine, which uses electricity for power and xenon gas as a propellant for extremely high efficiency and extremely low thrust, the nuclear thermal rocket, which uses an onboard nuclear reactor to heat up liquid fuel propellant for high efficiency and low thrust, and monopropellant RCS, which are steering thrusters that use monopropellant tanks shared between all stages. There's also a single 'normal' engine that burns monopropellant, the Puff.

At a first approximation the game uses real orbital mechanics. To get to space, you just have to go straight up above 70 kilometers. To stay in space, you must enter orbit, which means your sideways velocity has to be somewhere around 2500 meters per second so as you fall you curve around the planet. The M key brings up the map mode, showing you your trajectory. It'll also show you if your orbit intersects the planet, and you can mouse over Ap (your apoapsis, the farthest distance in your orbit) or Pe (your periapsis, the closest approach in your orbit) to see if they are above 70 kilometers.

At first approximation the game uses real rocket science. The more fuel you add, the more fuel you're wasting to carry that fuel. Staging (detaching tanks and engines when they're no longer needed) using decouplers is a must. Parachutes are also a must if you want to preserve the lives of your Kerbals, but remember. This game is realistic. Parachutes will not work on airless bodies like the Mun, and they may not be enough on their own on martian planets like Duna which have only thin atmospheres.

Career mode is kinda... not very well made? I would start with Science Mode. The tech tree will kind of ease you into building with limited parts. But you can always jump right into sandbox mode.

Rocket parts come in a few diameters sizes: 0.625m, 1.25m, 1.875m, 2.5m, 3.75m, and 5m. In addition, there are 1.25m (mk1), diamond-shaped 1.25x2.5 (mk2), and roughly 3.75m (mk3) spaceplane parts. The aerodynamics and structure works out best when same diameter parts are connected together. There are adapter parts to facilitate this, as well as fairings (procedurally shaped aerodynamic casings) and engine plates if you need to get around this.

Turn on Advanced Tweakables in the settings. This will allow you to right click on parts and select "rigid attachment", and to use "autostrut", both of which are necessary for making rockets behave. (you could try and use strut parts, but that can bloat your part count and often times it isnt clear how to even attach a strut in the direction you need) This is one of my least favorite parts of KSP, as this is pretty tedious for a large rocket, but it's necessary to keep it from flopping around. For some reason KSP's developers thought that floppy rockets (even when they should be perfectly rigid), would be more fun. The idea comes from the early days of the game, when the conventional wisdom was "if it moves and it shouldn't, add struts; if it doesn't move and it should, add more boosters." The game has gotten a lot more complicated now, and that design philosophy should have been left in 2012. There's also a mod, Kerbal Joint Reinforcement, that will provide this functionality without needing autostrut and rigid attachment per part.

On efficient launches, you're going to end up looking like you're burning up. This is a limitation of the 1/10th scale planets in KSP, and how that plays with the 7/8ths scale atmospheres. During a real launch as well as an efficient KSP launch, you'll end up travelling at 1500-2000 m/s in the upper atmosphere, but in the real world that's only a fraction of orbital velocity. In KSP, that is near orbital velocity, and so the game is balanced to assume you're in reentry conditions. If you have fairings to protect sensitive parts of your ship, you should be fine.

KSP's small scale makes Apollo's Lunar Orbit Rendezvous approach inefficient for the Mun and Minmus. It's actually cheaper to just directly land on the surface. This can be fixed by installing a rescale mod such as Sigma Dimensions, and setting it to 2.5 rescale and resize, and 1.6 rotation period scale. This makes delta-v 1.6 times larger than stock KSP, resulting in more realistic proportioned rockets. The game honestly isn't any harder in this state, it just needs somewhat bigger rockets. All that aside, the "Apollo style" orbital rendezvous approach works great for all other planets, since interplanetary transfer requires more fuel as do most planetary landings. This approach has two spacecrafts launch either together or separately that travel to the destination planet docked together. The lander then separates, lands, and eventually launches again, but only back into orbit, where the orbiter picks up the crew and they launch back home.