Does mass determine orbit needed?

[annallia]

Been trying to make a super tanker to require less stops at my station for me to refuel it. In the end the tanker alone weighs just shy of 280 tons. Didn't actually check how much it weighs with the rocket.

Anyway, my attempts at getting it into orbit have been failing miserably. At first due to structural failures on launch which have been fixed, now my orbits are degrading, and rapidly.

I have been attempting to put it into higher, and higher orbits but each time before I can send it to my station its orbit degrades and it ends coming back down to Kerbin. I started with 80km orbit, went to 90, 100, 125, 150, testing 200 now and even so I see it coming back down. If I switch to the map screen I see my orbit as showing as stable with the closest me getting to kerbin around 180 but for some reason I am continually coming back.

Edited August 2, 2013 by annallia

[ferram4]

Any orbit above 70km should not decay. Odds are there are two possible sources to your problem:

You're spending a lot of time in orbit with physics running; this is timewarp < 5x

Physics simulations aren't perfect, and errors will grow the longer you're using that approximate solution to the orbital equations. Accelerating to higher timewarps will fix this by clamping it to the exact solution of the 2-body problem.

You're not setting the throttle to zero while you're in orbit

This would cause your orbit to change a lot. Make sure that your throttle is actually set to zero. If you're using an unmanned probe, make sure that you aren't running out of electricity, which would make changing throttle impossible.

[longhornchris]

It shouldn't. The orbit is determined by velocity, independent of mass, provided you get periapsis above 70km where the drag kicks in (for Kerbin, see the wiki for other planets). Now it does take a lot more propellant to get more mass to orbit, hence normalizing fuel using delta-V rather than propellant mass (it also accounts for the logarithmic nature of the rocket equation). For 2 different rockets the delta-V to achieve the same orbit should be close - with the flight path and drag being the key additional variables. Two spacecraft in the same orbit should have the exact same velocity at the same point in their orbit (angle relative periapsis).

[annallia]

I will try time warping to fix it, it cannot be energy, all of my refuelers have generators on them (just in case I clip more panels on the station..) and enough that even with everything on they don't ever run out of energy. As well as an ample supply of batteries.

And yes I am sure I was shutting everything down, I have my throttle controls (up, down, kill) mapped to my mouse.

Edited July 29, 2013 by annallia

[Alfondoo]

A screenshot of your orbit would be helpful I think.