How did this happen?

[Skivvaxlare]

I built a rocket today. It was a simple three-stage rocket, made of all stock parts and mainly designed for a short flight. I wasn\'t expecting to get much more than 100,000 meters out of it. So imagine my surprise when this goes down:

How does this even happen? I certainly wasn\'t trying to reach 13.5 billion meters. Is this a glitch? My speed is varying between 7000 and 14000 m/s.

Similar experiences, anyone?

[Tiberion]

The speed difference between an orbital velocity and being fast enough to escape the planets gravity and be in a \'solar\' orbit around the star is not very much

So you just over-burned and escaped, and are now in orbit around Kerbol. As long as you haven\'t flown too far, you can burn retro-grade to slow down and stay in planetary orbit.

[Skivvaxlare]

Well, I\'m completely out of fuel, but my orbit isn\'t changing. I can\'t turn my SAS off, nothing is working on the craft. My only hope is that I\'ll cross paths with Kerbin near my apoapsis.

[Bluejayek]

What Tiberion said about orbital velocity is an important point. However, there are some other things I would like to clarify for you that your post indicates you may have confused.

First, the 13 trillion meters you see is the distance from the star (Kerbol) not the planet where you launched. Since kerbin orbits kerbol at this distance, as soon as you break out of Kerbin\'s sphere of influence, you are at this distance from the star, so it is not too crazy to consider getting to this distance.

This brings me to my next point, spheres of influence. The way gravity is coded in this game is that, instead of having the gravity from all bodies simultaneously affecting your craft, only one body will affect you at once. The body that is affecting you is determined by your distances to each body, and their relative mass. You will always be affected by the one that would have the greatest effect, ie, close to Kerbin you are in its SOI, but because Kerbol is so much heavier, once you go some distance from Kerbin you fall out of its SOI.

Escape velocity: This is the velocity required to escape to infinity from a body in the absence of any other bodies gravitational pull. You can read more about it on wikipedia if you wish, but the essential point is that the further you get away, the lower the gravitational pull, so if you get moving fast enough the gravitational pull will decrease quickly enough that you just keep going. Mathematically, you can get this by comparing your kinetic energy to your gravitational potential energy. I don\'t know offhand the escape velocity of kerbin, but I believe its around 6000m/s. Further, because Kerbol exists, the velocity to break free of kerbins SOI is acually somewhat lower, as you can put yourself in a highly eliptical orbit that will leave Kerbin\'s SOI, while not breaking the escape velocity.

Another point: Stating 'I only expected to go 100,000m' doesn\'t really mean much in an orbital sandbox like this. Most rockets can potentially go infinite distance, as you can set them in stable orbits and just leave them. A much more sensible statement is 'I only expected to be able to get into a 100,000m circular orbit' or 'I only expected to reach 100,000m altitude and not get into an orbit'.

Finally, in order to get into orbit around kerbin, you have to actually turn over at some point. If you just thrust straight up you will either a) Reach escape velocity and begin to orbit Kerbol (As you did) or Reach some altitude and fall back to the surface.

I hope this post has enlightened you somewhat, and I apologize if you knew some of this already.

By the way, can you post a screenshot of your ship prelaunch, and perhaps the craft file?

As per your latest post, it will be better off to just leave your brave kerbals to bask in the eternal light of the sun until their air runs out. Sacrifices are expected in such a new space program.

[Skivvaxlare]

Here\'s the ship in the assembly building. It\'s extremely simple.

I\'m rather new to KSP, so the majority of this stuff I was unaware of. I don\'t know how to get the craft file.

When I said that I wasn\'t expecting more than 100,000m, I meant that I expected to reach that altitude and then come back down without covering much ground.

I\'m rather confused as to how I ended up orbiting Kerbol, as I was aiming directly at the Mun the entire time.

I had a bit of an issue with the launch, as the four bottom engines weren\'t enough to push the craft up. I had it set up so that the bottom four would decouple and then the bottom middle engine would fire off, but I had to decouple the four on the launch pad and they pushed me upwards as they were still running at full power.

[Bluejayek]

Nice craft.

As per aiming at moon, the moon is not a very massive body. Therefore, its SOI is very small. Further, even if you aimed directly at it when you launched, it is moving as well. By the time you get to where it was, it has probably moved out of the way, so you miss it and enter the suns SOI instead.

If you are trying to launch to the moon you must take into account this motion and aim ahead of it. I find the most foolproof method is using Hohmman Transfer orbits. To do this, you first set up a circular(ish) orbit around kerbin in the same plane as the moon. Then, when you are oposite about 20 degrees ahead of the moon (the point where the moon will be when you get there) you do another burn until you are in an eliptical orbit intersecting the moons orbit. When you get there, hopefully you are in the moons SOI and can slow down to an orbit or (crash) landing.

Welcome to KSP and happy flying

PS: Craft file is in KSP > ships > (shipname.craft)

PPS: In terms of your issue with the bottom stage being too small, it can be helpful to add a few solid boosters around it. You can set them up to fire at the same time, and they will give it the little boost it needs to leave the ground. It would make your nice ship a bit less symetrical though.

Also, afaik the seconds A.S.A.S. module you have there does absolutely nothing. Deleting it would increase your performance noticeably even if it is a small portion of the total weight of your craft, simply because it is on the final stage. With some rockets, you can even get 100\'s of m/s of extra delta v by removing your parachute. This however is not recomended if you want your kerbals to survive and are not an expert pilot. Powered landings on kerbin can be very dicey.

[thorfinn]

Here\'s the ship in the assembly building. It\'s extremely simple.

I\'m rather new to KSP, so the majority of this stuff I was unaware of. I don\'t know how to get the craft file.

When I said that I wasn\'t expecting more than 100,000m, I meant that I expected to reach that altitude and then come back down without covering much ground.

Kerbin is much smaller than Earth; also, the fuel we use is very energetic, if you do the math. The game will be rebalanced in the future, but for now, you\'ll discover that flying in Kerbal space needs much less imposing designs than in real life

[Skivvaxlare]

Here\'s the craft file if anyone wants it, but I would suggest fixing the launch issue before attempting any serious launch.

http://www./?b1855igd4rkzaqn

Thanks for all the info, I\'ll (try to) put it to good use.

[UmbralRaptor]

The craft file is most likely in /KSP/ships/ (Assuming you didn\'t stick your /KSP/ folder under Program Files). ninja\'d!

For the rocket itself, my ?V estimate is that it may be able to perform a munar landing/return. It in principle has enough first stage thrust, but wasn\'t lifting off due the the 'stick pad' bug. Raising the first stage up on decouplers is a sufficient workaround at this time. Alternatively, drag the engine from stage 6 to stage 8, giving a bit more thrust in the early part of the flight. Also, you may as well remove one of the ASAS modules. There\'s no real need for more than 1 per ship. (Though stacking multiple SAS can make sense in some cases)

It sounds from your comments like you\'re not especially familiar with orbital mechanics. Perhaps a tutorial like this is in order?

[Bluejayek]

I\'ve got some screenshots of one of my craft that is able to achieve Kerbolar orbit. It is very close to being able to achieve kerbol escape velocity in fact. It probably can, but I would have to do a more fuel efficient launch.

You\'ll see that it really is very small. Total of 4.5 units of liquid fuel.

Incidentally, this is also easily capable of making it to the mun, but landing is a real pain without landign struts, and I have not yet made a succesful landing in a state that I could take off again.

A final comment I will make at this time.. To achieve orbit, it is ALWAYS most efficient to turn towards the 90 degrees marker on the navball. The reason for this is Kerbins spin. The spin on its axis gives you a bit of a boost (~200m/s iirc) which significantly reduces your fuel requirements.