periapsis

Just because it's moving below circular orbital speed doesn't mean the periapsis is in the atmosphere.

Anything it loses to the solar wind on the flyby comes off the apoapsis, not the periapsis.

Changing the initial launch position makes it easier to choose what area of the planet the periapsis will be over.

The lowest possible altitude of the fragments in orbit (i.e the periapsis) is the same that of the impact point.

Until Apollo 14, the LM would enter a 50,000 ft periapsis on the way to landing.

With periapsis's in different positions, you can get birds into rarely colliding 'resonances' of sorts.

Every time around my apoapsis would drop, the periapsis stayed almost constant through many orbits.

Is this the most efficient way to bring up the periapsis?

When I launch the birds, unless I take great care to do otherwise, my periapsis tends to slightly after my launch position.

But since the impact point isn't guaranteed to be the periapsis or apoapsis, the above mentioned diametrically-opposing point also cannot be guaranteed to be an apsis.

The periapsis will always pass through where the collision happened.

Also, inclination burns can be combined with raising periapsis, which allows you to save some fuel thanks to the way they are at a 90 degree angle.

I had fun "getting into orbit" and watching my velocity increase at periapsis and decrease at apoapsis, then descending and landing with the rocket power button ([Space]).