Myth: 1 G barrel rolls are impossible.

The intitial velocity limitation says 'vertical'.

I haven't really been following the thread, so I don't know what the
initial thing is (except, by the thread title, that it's a
miscommunication about whether the 1g force one feels standing still is
to be "counted" or not, and whether a degenerate case of the barrel roll
"counts".

I don't care what size the 'walnut' is,
it will be impacted given there was no
horizontal velocity component.

True. But if there is =no= horizontal component, you don't have a very
interesting maneuver.

btw, is a satellite "in orbit" if it blows up before it completes a
complete revolution (even though it would have completed it just like
any other orbiting satellite?)

Even if there was, by the way, the Newtonian physics demand the path
will cross the starting point,

True (fsvo starting point)

and the implication to most readers
would be that was on a surface.

Depends on the situation. Rockets start from the surface, but don't
"enter orbit" until they are far from that surface (yes, this involves
acceleration).

Jose, I don't think from an initial impluse, which is the model I
described, you can avoid impact unless the mass of the projectile is
such that conservation of momentum would demand the launching surface
move enough out of the way of the way to avoid the impact.

If by "impulse" you mean "instantaneous change in velocity" then you
would need the launching surface (if there be one) to move out of the
way. But you don't need a launching surface. You can jump into the air
(vertically) and then apply a (huge) impulse horizontally while you are
still airborne, and you will be in orbit. (IF we are talking about
instantaneous impluses, why not extend the fantasy)

If by impluse you merely mean "very fast change in veolocity", then
there will be some value of "very" for which you can avoid impact.

Jose
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