In article ,
says...
Perhaps a brief refueling in LEO before attempting its fly-by-rocket
landing. Of course we'd have to place a sufficient spare amount of HTP
plus a little something else of a hydrocarbon on orbit first.


You just made the problem much harder.

The fuel you need to get the 1st stage into orbit is what you would use for
landing.

And if you get it into orbit, it has a LOT more energy you have to lose
before landing.

Agreed. We are talking about recovering the first stage of Falcon 9,
which separates from the second stage at a relatively low velocity when
compared to orbital velocity. The fuel needed to fly that first stage
back to the launch site is far less than what would be needed compared
to the fuel needed to put it into orbit.

Some people are making this whole thing out to be harder than it really
is. Losing a satellite, or putting it into the wrong orbit, because one
out of nine engines fails is absolutely unacceptable. To mitigate this,
Falcon 9's first stage *already* needs to carry extra fuel in order to
handle engine out scenarios. Because of this, if no engines fail, there
will already be extra fuel in the tanks. This extra fuel is then re-
purposed to provide much of the delta-V necessary to fly the stage back
to the launch site. So, there is far less "wasted fuel" used to recover
the first stage than the "performance uber alles" crowd would have you
believe.

The downside is that if you lose an engine on ascent, there simply won't
be enough fuel to fly back to the launch site, so you'll likely lose the
first stage. SpaceX would then have to "eat" the cost of that stage, so
pricing launches will have to take into account the occasional loss of a
first stage. But, do note that even in this case, the payload makes it
into its proper orbit, so this is not a "launch" failure, it's a
"recovery" failure. In this business, NO ONE CARES about "recovery"
failures, since the competition doesn't even *try* to do this! So there
is very little downside in *trying* to recover the first stage. With
the exception of the shuttle SRB's, it's actually quite shocking to me
that no one before SpaceX has ever made a serious attempt to do this.

To sum up, the primary goal is always to get the payload into the proper
orbit. Price your launches such that recovering the used first stage is
gravy, and every recovered stage is extra profit which can be used to
fund the eventual reuse of the upper stage. This approach to
reusability is actually quite elegant.

Jeff
--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer