Kepler's Laws

[Torsen]

So I'm teaching myself physics, and using Kerbal as a fun tool to help me do that. I'm running into some confusing Kerbal measurements that don't add up in my physics calculations.

T² = 4À²(Semi-Major Axis)³ / (GM_Kerbin )

Semi Major Axis = 12.7 million Meters (Apoapsis at the moon's radius, Periapsis about 100km above Kerbin's surface)

When I put the above into the formula, I calculate an orbital period around 155,000 seconds. However, when I actually fly this in Kerbal I get an orbital period around 189,000 seconds.

Big Difference.

Does anybody here know why?

Thank you!

[Brotoro]

SEMI-major axis is only half of the length of the long axis of the ellipse.

[Torsen]

Thanks Brotoro. There's one stupid mistake down.

However now I'm even farther away from the measured orbital period of roughly 189,000 seconds.

Now I'm looking at 53,500 seconds for a full orbit, which still isn't correct.

[Brotoro]

Also...When I just flew that orbit (100 km above Kerbin, out to the Mün's orbit, and back), I measured an orbital period of 53,506 seconds.

[Torsen]

I'm batting a thousand tonight. I'll go take a look at that one again.

Thanks Brotoro.