Why we need a fast courier rocket service

In article ,
Mary Shafer wrote:
The problem is considerably reduced for rockets because of their very
short transit time. In particular, that makes it feasible to have a small
vehicle that makes ten trips a day, rather than a big one which can only
make one trip a day...

What about the airspace? I assume that the rockets will launch and
land near large cities, but large cities have multiple airports and
restricted airspace and air traffic. If the rocket is flying city
pairs, not hub and spoke, there's going to be a lot of rocket launches
and landings at ten trips a day between city pairs.

It's going to mean real changes to airspace allocation and traffic control.
Even less-frequent rocket traffic is going to require changes to the
latter, because (like really-high-performance aircraft) rockets can't just
wait around for a few minutes while ATC sorts out some snafu -- if they
are coming in for a 3:47 landing, they're going to land *at 3:47* and ATC
will have to be organized to accommodate that.

If you adopt my favorite approach -- VTVL -- then one obvious option is to
have vertical columns of reserved airspace, off limits to winged traffic,
extending from ground level up to the top of winged-vehicle airspace.
(The columns don't need to be all that wide: a rocket can't dawdle around
in mid-air for a few minutes to shuffle sideways, so it's going to have to
be capable of aiming pretty precisely at its landing point quite early in
descent, and it can aim at the top of the column instead. Similarly,
traffic control within a column will not be a big deal, because whether
going up or down, a rocket traverses the full height of the column pretty
quickly.) This completely separates rocket traffic from airplane traffic,
except in emergencies.
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