Flight Question Energy transfer and orbit circularization.

[n72.75]

So I'm in a 350x350 km orbit.

Over some period of time my orbit "decays" to 250x500 km.

Now according to my calculations the specific orbital energeries: are as follows:

350x350 km --------> -2.6876e+021 joules
250x500 km --------> -2.6776e+021 joules

So I actually have lost energy.

Now for my question:


Is there a "fuel-efficient" approach to recircularize my orbit that doesn't require me to burn retrograde at periapsis and prograde at apoapsis.

I've tried inward and outward burns, but had little effect.

Also, is there any specific method that I can employ to make my orbits decay in a circular method.

 

[Fabri91]

Maybe I've got an idea, but see it as a wild guess: if you burn "down" 90 degrees when you are at 350km you basically "turn" your velocity vector without changing it's intensity...your speed.
So after doing this a short burn prograde to get back your lost energy and you should be set.

Does this make any sort of sense?

 

[n72.75]

Maybe I've got an idea, but see it as a wild guess: if you burn "down" 90 degrees when you are at 350km you basically "turn" your velocity vector without changing it's intensity...your speed.
So after doing this a short burn prograde to get back your lost energy and you should be set.

Does this make any sort of sense?

I just tried it and it works, but its more specific.


To circularize: burn "inward" when the change in altitude is positive and maximized, burn outward when the change in altitude is negative and maximized.

 

[Urwumpe]

To circularize: burn "inward" when the change in altitude is positive and maximized, burn outward when the change in altitude is negative and maximized.

If I remember correctly, the maximum outward velocities should be at the 90° True Anomaly and 270° true anomaly points.

 

[n72.75]

If I remember correctly, the maximum outward velocities should be at the 90° True Anomaly and 270° true anomaly points.

Well, it worked.


Another source of my problems may be with Orbit MFD:

I watched my orbital alt. for one full orbit. The predicted apoapsis and periapsis are consistently in over 10%(alt. not rad.) error with the true apoapsis and periapsis.

 

[Urwumpe]

That is no problem, but a documented feature. The orbit elements in orbit MFD are osculating elements, kepler orbit approximations of the true orbit, valid only in your current position.

 

[n72.75]

That is no problem, but a documented feature. The orbit elements in orbit MFD are osculating elements, kepler orbit approximations of the true orbit, valid only in your current position.

I didn't mean a problem with the MFD, I meant a problem with what I was trying to do.

 

[Wishbone]

The most efficient way of changing apses is always at the other apsis, firing prograde.

Transversal (inward/outward) impulses are much less efficient, but useful if you do them with RCS thrusters (again, at apses).

Re: spirals. The problem is that Orbiter uses numerical integration to propagate state vectors. You can try symplectic integrator instead of the default Runge-Kutta.