I just created a Modelica Model of a rocket landing in vacuum. Now I attempt to verify it against reality. However, I have a hard time to figure out some plausible initial parameters. Apollo 11's Eagle had a Periapsis of 15km. But what was its initial speed?
I assume that everyone does one deorbit burn and later attempts to get as close to a suicide burn as reasonable. So I modeled my experiment after a falling mass under retrograde thrust in a cartesian coordinate system. Obviosuly, this model has a hard time when it comes to very long landing approaches (since the cartesian coordinates to not take into account the curvature of the target body), so lowering the periapsis to 0 is not an option right now (although probably the most efficient approach). I arbitrarily choose an initial surface velocity of 1km/s which gave me a landing at 140km.
So what is a plausible surface speed after the deorbit burn?