You are not logged in.
This illustration in post 150 just above shows the real point to be made here: the launch trajectory has an apogee altitude, where it has gone horizontal before starting downward. At this point, there is some horizontal speed. You make this same point in space your perigee point for a transfer ellipse, with its apogee on the other side of the Earth at your desired circular orbit altitude.
Use the orbits+ course orbit mechanics spreadsheet "orbit basics.xlsx, using the two-endpoints worksheet, set up for Earth. Plug in your perigee altitude and your apogee altitude, and use the average Earth radius value since the inclination is unlikely to be zero. It will give you the transfer ellipse perigee and apogee speeds, and it will also report circular orbit speed at perigee (which you do not need) and at apogee (which you do need).
The difference between transfer ellipse perigee speed and your launch trajectory apogee speed is the ideal dV you need, to get onto the transfer ellipse from your launch trajectory. This might need a little bit of factor-up to cover some small gravity and/or drag losses, more if you do not burn quickly enough to be "impulsive".
You will return to perigee if you do not circularize at apogee. If you do, it is below the entry interface altitude effective for orbital class speeds. That means you will re-enter, unless you raise your transfer ellipse perigee altitude above the entry interface altitude. You do that with a small burn at your transfer orbit apogee.
You avoid that fate and get where you really want to go by burning at apogee to raise your perigee all the way up to that apogee altitude. That IS circularization, exactly per the 1st 3 lessons in the orbits+ course set! The dV there is the difference between circular orbit speed and transfer ellipse apogee speed. It needs no factor-up as long as you do it quickly enough to be "impulsive".
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
Offline