Commercial suborbital point-to-point flights

wrote in message . com...
OK, then let's reduce its range to 2,462 miles (3,961 km), New York to
LA. Make it a 4-passenger bizspaceship. Assume jet take-off and
landing, jet fuel (or maybe RP1) & LOX rocket engine. What kind of
delta-vee is required? Resulting max velocity? Trip time? Etc.

5500ish m/sec, trip time about 30 minutes (including reentry and glide
to landing).

Is that the delta-vee required or the max velocity or the average
velocity?

Not sure of the answer but presumably the ship would have to withstand much
higher mach numbers than SS1 which implies much more expensive construction.

There's the rub. A ballistic trajectory is going to come back in at
about a 30 degree angle, which means just the vertical component is
over 2500 m/sec. Let's see, in airplane terms, that's a sink rate of
500,000 feet per minute... You get into thick air very quickly at
that sink rate.

If you can pull out at 10 g eyeballs down, you reach the bottom of
your dive at 66,000 feet. Unfortunately you do this at Mach 14, hit a
peak indicated airspeed of 2300 knots, and pull 12 g eyeballs out in
addition to the 10 g eyeballs down. I don't know of a material that
can handle Mach 14 at 66,000 feet, but if you can build a ship out of
holysmokium gadzookite, and your passengers don't mind 15 g on
reentry, go for it.

If you can pull 15 g eyeballs down, you pull out at 106,000 feet and
Mach 17. Peak indicated airspeed is about 1050 knots, and eyeballs
out is negligible. This might actually work for an unmanned vehicle;
an F-104 has flown over 1000 knots on the deck at Bonneville.

I don't understand: the Shuttle re-enters much faster and yet
experiences much lower deceleration. The bizspaceship, if entering at
5500 m/sec, could spend 3 minutes decelerating at 3 gees, starting 500
km from the landing site. What am I not seeing?

At a bizjet share-ware site,
http://www.airelite.com/membership01a.html we see that a $99,500
memberships gets you 25 hours of flight time, presumably at something
like 560 mph (250 m/sec)so you're paying for 14,000 miles or about
three round-trips NY/LA.

That's very good to know. That says that if the technical problems
can be overcome, the market problems - mostly subsonic bizjets eating
your lunch - may not be insuperable.

The bizjets seem to survive competing against the ordinary airlines,
even though the bizjet service mentioned above seems to charge about
$33,000 for a NY/LA roundtrip ticket. Similarly, a bizspaceship might
be able to survive servicing those folks to whom shaving 6 or so hours
off their round-trip is worth paying 3 times the bizjet rate.

(Bill Bogen) wrote in message . com...

5500ish m/sec, trip time about 30 minutes (including reentry and glide
to landing).

Is that the delta-vee required or the max velocity or the average
velocity?

That's the delta-v. It's rough; I haven't rebuilt the vis-viva model
I lost when my laptop died.

I don't understand: the Shuttle re-enters much faster and yet
experiences much lower deceleration. The bizspaceship, if entering at
5500 m/sec, could spend 3 minutes decelerating at 3 gees, starting 500
km from the landing site. What am I not seeing?

There's a fundamental difference between a reentry from orbit and a
reentry from a transcontinetal flight. Coming down from orbit, you
have a very shallow dive angle, so you have plenty of time to arrest
what little sink rate you pick up. Coming down from TC, you have a
very high sink rate due to the high loft angle you had to use to keep
your delta-v down: with a Shuttle-like dive angle coming in, you could
only have gotten a few hundred miles with the correspondng loft angle
and a mere 5500 m/sec.

For hypersonic transports, it may actually be easier to accelerate
nearly to orbital velocity even if you don't need it for range, just
to be able to depress your trajectory and keep the sink rate down when
you come back in. We know how to get to orbital velocity. We don't
know how to survive slowing from Mach 15 to subsonic in 30 seconds.

The bizjets seem to survive competing against the ordinary airlines,
even though the bizjet service mentioned above seems to charge about
$33,000 for a NY/LA roundtrip ticket.

You might look into that some more. It's a subsidiary of Delta, and
it may be a loss leader, created to ensure Delta can do anything the
business traveler needs. 60 times the JetBlue round trip fare is
pretty extreme.

-R