How to reach orbit, and a (sandbox) rocket to do it with.

[Vanamonde]

So you want to get into space and stay there. But gravity will always be pulling your ship down. There's nothing you can do to stop that. But what you can do is move to the side fast enough that as gravity pulls you down, you just keep missing the thing you're orbiting. So staying in space is not a matter of reaching a place or an altitude, but of going fast enough. Orbit is a velocity, and here's how to reach it.

Here's how Isaac Newton figured it out.

He pictured a canon firing from a hill, and the faster the canonball went, the farther it could go before hitting the curved surface of the earth. As it goes faster and faster, eventually, there would be a velocity at which the canonball falls forever without hitting the ground, and that is what we call orbit.

This is what you want your KSP ships to be able to do, but there's a complication, which is that Kerbin has an atmosphere, and moving through atmosphere slows you down. So there's an added step to reaching orbit in the game, and that is that you must go up for a while, to get clear of the air, before you start applying all of your ship's thrust to reaching orbital velocity. You will start off going straight up, and then gradually rotate so that the ship is pointing horizontally. This way you escape most of the air's effects while building up to orbital speed.

Here's a ship you can use to fly this tutorial explanation: the M120 Trailblazer.

Craft file: https://kerbalx.com/Vanamonde/M120-Trailblazer

For the sake of keeping things simple, this ship was made in sandbox mode, and is not meant to be used in career, as not all of its parts will be available to you at the start of a campaign.

(Note: there is nothing magical about the exact angles and numbers I give in this guide, and others may give different advice. This guide is meant simply to be an example that works, though other approaches will work as well.)

Turn the thrust all the way up with the left-shift key, hit the T key for stability assist, and press the spacebar to fire the engine. The weight of this ship is balanced against the thrust in such a way that you will not need to turn the throttle up or down during the flight. It should either be firing at full thrust, or turned off.

Because the current version of the game's aerodynamics can make holding a turn difficult, I like to begin to tilt the ship a few degrees right after launch. This leaves less of the turning to be done later, when the air is fighting you harder.

Notice that I am turning toward the east, which is the line marked 90 on the navball instrument.

This is because the planet is already rotating in that direction, so you are adding that rotation speed to your ship's speed to help you reach orbit. This saves you a little fuel and leaves you lined up better for flying to other worlds, but you can also reach orbit by flying in any other direction.

Watch the highest point marker, the apoapsis, to help turn by steps. When it gets to 25,000m, turn the ship so that it's facing 45 degrees toward the east.

The air flow will be fighting you pretty strongly at this time, trying to force your ship to go back to its previous heading. You will need to keep applying steering control until it settles on the 45 degree angle, which is why I have given this rocket those nice big steering fins.

When the apoapsis reaches 45,000m, turn the ship so that it is facing just a few degrees above the horizon.

Somewhere about this point in the flight, the first stage will run out of fuel and should be ejected. Hit the space bar to do so, and continue the flight.

And when the apoapsis reaches 60,000m, turn the ship fully horizontal and keep it pointed that way,

until the apoapsis reaches 80,000m, then shut the engine down with the X key. This is because the atmosphere ends at about 70,000m, so if you go up to 80,000, you will be free of it and air resistence will no longer be slowing you down.

However, as you can see in that last picture, you are not going fast enough to stay in orbit yet, and will just fall back down unless you do something more. So let the ship coast until it reaches 80,000m, then make sure the ship is pointed horizontally again, and fire the engine once more, at full thrust, with the Z key. Watch the opposite marker, the periapsis, until it too rises to around 80,000m. (Note that it does not matter if the periapsis and apoapsis are at the same height. As long as both are above atmosphere, that's good enough.)

When that lowest point in your ship's path is also above the upper limit of the atmosphere, the ship can just keep falling forever without hitting the planet, and you are in orbit. Shut the engine down now, and leave it off.

From here you can just watch the scenery for a while, or send the Kerbal out on EVA.

Steering him back inside the ship can be tricky, though, so maybe leave that for another day.

Anyway, when you are done orbiting, it's time to bring the ship home. Turn it until it is pointing at the retrograde navball marker, and burn the engine.

This will cause the lowest point of your orbit to sink. You do not need to put this marker all the way down to the ground. All you need to do is put that point low enough in the atmosphere that air will slow the ship the rest of the way for you. A higher initial periapsis takes longer to brake to a fall, and lower may expose the ship to dangerous heat or even a surface impact. For the sake of this practice mission, put it between 45,000 and 30,000 to ensure a safe return.

Anyway, once your descent has been set, you no longer need the engine and any remaining fuel. To make it easier for the ship to land safely without that useless weight, the second stage should now be ejected with the spacebar.

Once you are on the way down, hit the spacebar to open the parachute and watch the capsule float to a landing.

And that's it: your first orbital flight. I hope this is helpful.

[Phil deCube]

Nice. Like it.

[micha]

On the whole a nice intro, but you want to gradually turn all the way to space, not perform sudden turns when you hit special markers. With the new aero that is a very easy way to flip out and as you noted you'll be fighting atmospheric drag - which wastes dV.

A good Rule of thumb is to be at roughly 45degrees when you're 10-15km up, and you'll be wanting to go around 300-350m/s at that stage.

If you time everything absolutely perfectly, you never shut down your engines and circularise into an orbit just as you reach apoapsis. This is not easy.

Also, your orbital velocity at ~72km altitude is ~2285m/s which you can also use to guestimate when you're reaching orbit.

[Vanamonde]

micha, as I said, this is only one method. And it's not intended to be the most efficient, but rather an easy one with clear instructions for newbies to follow. And I always test my ships and guides carefully before posting them, and the example ship I've provided has enough control authority, with those big fins, that it never had trouble with flipping.

[Dispatcher]

That's very nice, Vanamonde. Thanks for sharing that; I'll probably show it to a few relatives and friends who have KSP but don't play much.

[Chiron0224]

nice tutorial. Two things I would change.

1. You have your hotkeys backwards: Z is full throttle and X is kill throttle

2. I would include the conditions for a safe chute deployment without having to watch the indicator i.e. speed <~250m/s

[klesh]

then shut the engine down with the Z key.

fire the engine once more, at full thrust, with the X key.

I think you have your X and Z's backwards (unless I remapped them to be the reverse of that, which I don't think I did).

Edit: Looks like he beat me to it ^ (I just read through the first post).

[Vanamonde]

Oops. Forgot I had changed my keybindings from the stock ones. Blame Claw; he proofread it for me. Fixed now.

As for the chutes, didn't want to overwhelm newbies with numbers.

[metl]

Now that is a well crafted beginners guide to orbit!

[Smart Boy]

I actually got my periapsis above 0, it’s so close!

[Vanamonde]

18 hours ago, Smart Boy said:

I actually got my periapsis above 0, it’s so close!

Keep plugging!