circularization

It is not very hard to use Vizzy to get a craft in orbit, it is less easy to get a (near) perfect circular orbit. I tried and ended up with something that works.

circularization pseudo code:

Have heading locked on prograde

Last phase of ascent: burn until intended apoapsis is reached

set variable: Intended orbital velocity =~ 3450m/s (for ~85km circular orbit)

set variable: TTAfactor =~ 40 (tweak to adjust from how many seconds before reaching Apo the burn will take place) (TTA means Time To Apoapsis)

While current orbital velocity is below intended orbital velocity:

Calculated burn moment in seconds before reaching Apo = (intended orbital velocity - current orbital velocity) / TTAfactor

Burn when TTA is less than calculated burn moment (take into account that burn may still be occurring when Apo has been passed, in which case TTA is large; so include check for TTA >= a few minutes). If tweaked correctly, burn will pulse while calculated burn moment hovers around actual TTA.

When current periapsis is larger than 40000 or thereabout, engage low throttle setting (to reduce overshooting of Apo and Peri)

(optional: to compensate for low TWR, have a pitchup time window relative to TTA; lock heading on current, set pitch, return to lock on prograde after pitchup window)

When current periapsis is equal or larger than intended periapsis, stop burn and exit this While loop

(End While)

It still requires some tweaking, but a close to perfect circular orbit can be achieved much easier than tweaking a series of events that rely on 'wait x seconds'. Example: with intended apoapsis at 85km and intended periapsis at 84km, a ~87 by ~87 km orbit can be reached.

screenshot of Vizzy circularization segment:
https://steamcommunity.com/sharedfiles/filedetails/?id=1939698450

download craft:
https://www.simplerockets.com/c/yAfQxN/Vizzy-circular-orbit-demo