Is suborbital a real market?

Sylvia Else wrote:

Well, I think you know my preference for SSTO, but yes, a TSTO would
provide a clearer path - at least, apart from the hypersonic separation
issue, if it really is one.

It seems to have been at least once, on 30 July 1966, when the D-21
drone "was trapped in the shock wave of the aircraft, forcing the
drone back into the M-21 [modifeed A-12], causing the aircraft to
break-up at Mach 3." Of course, it could be that that was a unique
quirk at that speed, and everything would be just dandy at Mach 6 or 8
or 10.

Or if the second stage were, say, a pig.

Sylvia Else wrote in
u:

Rand Simberg wrote:
On Fri, 23 Nov 2007 09:38:52 +1100, in a place far, far away, Sylvia
Else made the phosphor on my monitor
glow in such a way as to indicate that:

Rand Simberg wrote:

As Jeff Greason of XCOR says, it's a lot easier to build something
that's operable and affordable, and gradually expand its performance
envelope, than to take something that achieves the needed performance
at an insanely high cost, and make it operable and affordable.

It's the "gradually expand its performance envelope" that is in
question. Can this be done with a suborbital craft to the point where
it becomes an orbital one? It seems more likely to me that you simply
reach a point where a complete rethink is required.

As has been pointed out there is the obvious path of expansion to
develope a TSTO based on a suborbital vehicle with considerable payload
capacity.

The problem of hypersonic separation is diminished if the second
stage/payload is detached at or close to the apex of the ballistic
trajectory - at 100 km the air is pretty thin.

As to why one would want to develope a reusable ballistic vehicle with a
payload capacity of several tonnes - think of a reusable ballistic
missile. How much cheaper it becomes to lob multi-ton warheads to the
other side of the globe if one has a reusable first stage that can fly
several times a day.

Indeed we are approaching the future where even relatively small
countries can afford to have quite significant ICBM capacity. Cheaper
launch in combination with improved accuracy makes even use of
conventional warheads much more attractive.

A decade or so and we are bound to see first examples of these vehicles
at Paris air show.

H Tavaila

On Nov 23, 7:42 am, Monte Davis wrote:
Sylvia Else wrote:
Well, I think you know my preference for SSTO, but yes, a TSTO would
provide a clearer path - at least, apart from the hypersonic separation
issue, if it really is one.

It seems to have been at least once, on 30 July 1966, when the D-21
drone "was trapped in the shock wave of the aircraft, forcing the
drone back into the M-21 [modifeed A-12], causing the aircraft to
break-up at Mach 3." Of course, it could be that that was a unique
quirk at that speed, and everything would be just dandy at Mach 6 or 8
or 10.

Or if the second stage were, say, a pig.

I have a lot of respect for the potential problems
of supersonic separation, Monte. IMO, the trick
is to stage at low dynamic pressure--but not so
low as to make abort and normal first stage
recovery a problem for a winged first stage. We
think that our staging at mach 2 at 40 km fits the
requirement. At this staging point, the fully loaded
orbiter is relatively unaffected by the thin air.
However, the empty "kite-plane" carrier stage with
its huge wing area can actually pull about 2 g's
in this thin air--enough, we hope, to actually be a
significant help in separation. If necessary, the
two-stage system can also abort from this point
--after jettisoning orbiter propellants. The two-
stage system can then glide back to the launch
site and make a powered landing at the launch-
site runway.

As project engineer/program manager for
fighter systems at North American Rockwell
in the early 70's, I was quite aware of the
problems of supersonic separation of stores.

Len

Monte Davis wrote:
Sylvia Else wrote:

Well, I think you know my preference for SSTO, but yes, a TSTO would
provide a clearer path - at least, apart from the hypersonic separation
issue, if it really is one.

It seems to have been at least once, on 30 July 1966, when the D-21
drone "was trapped in the shock wave of the aircraft, forcing the
drone back into the M-21 [modifeed A-12], causing the aircraft to
break-up at Mach 3." Of course, it could be that that was a unique
quirk at that speed, and everything would be just dandy at Mach 6 or 8
or 10.

More likely it's a quirk of attempting an aerodynamic-only sep at that
dynamic pressure, which other vehicles avoided by:

1) Sep at lower velocity (WK/SS1)
2) Sep at higher altitude (almost everyone else)
3) Sep assisted by dedicated sep motors (space shuttle, several others)

So yes, it is a problem, but one which can be avoided with the proper
staging conditions - which, of course, further drives the design of both
stages.

On Nov 22, 9:50 pm, Sylvia Else wrote:
Len wrote:
On Nov 22, 7:09 pm, Sylvia Else wrote:
Rand Simberg wrote:
On Fri, 23 Nov 2007 09:38:52 +1100, in a place far, far away, Sylvia
Else made the phosphor on my monitor glow
in such a way as to indicate that:
Rand Simberg wrote:
It's not only not "easy," it's not possible. Getting to orbit
requires an entirely different vehicle, which they'll learn how to
build by building suborbital vehicles first.
That's what is in question. What does one learn from building suborbital
vehicles that is useful for building craft that can reach orbit and
return from it?
One learns how to build operable, affordable reusable rocket vehicles.
As Jeff Greason of XCOR says, it's a lot easier to build something
that's operable and affordable, and gradually expand its performance
envelope, than to take something that achieves the needed performance
at an insanely high cost, and make it operable and affordable.
It's the "gradually expand its performance envelope" that is in
question. Can this be done with a suborbital craft to the point where it
becomes an orbital one? It seems more likely to me that you simply reach
a point where a complete rethink is required.

Correct.

I think that "gradually expanding the performance
envelope" is something that we might all agree
upon. IMO, a properly designed HTOHL, TSTO
space transport can allow a very logical and
appropriate, step-by-step expansion of the
performance envelope with safe recovery
likely with each step. Low-cost, relatively safe
incremental flight testing is the key. Suborbital
offers only limited appropriateness because it is
literally not on the right technical path--or business
path, for that matter.

Well, I think you know my preference for SSTO, but yes, a TSTO would
provide a clearer path - at least, apart from the hypersonic separation
issue, if it really is one.

Sylvia.

We all prefer SSTO--but it just isn't
that doable at this time. Supersonic
(hypersonic) separation can be a
problem; however, as I replied to
Monte, I think this potential problem
is quite manageable. As for other
operational aspects, TSTO may
actually have advantages over SSTO.
For example, powered landing of the
carrier stage--or aborted landing of the
two-stage system is quite reasonable
for TSTO, but not for SSTO.

Incidentally, I pushed SSTOs myself
for quite a long time. In certain limited
circles in the early 60's and again, in
the early 70's, I was known as Mr.
single-stage-to-orbit. With enough
not-now-available technology--or with
very large vehicles--SSTO becomes
feasible. However, for the present time,
smaller, but still large, TSTOs will make
more technical sense and--because of
size effects on traffic level--more business
sense for some time to come.

Len

On Fri, 23 Nov 2007 08:35:33 -0800 (PST), in a place far, far away,
Len made the phosphor on my monitor glow in such
a way as to indicate that:

We all prefer SSTO--but it just isn't
that doable at this time. Supersonic
(hypersonic) separation can be a
problem; however, as I replied to
Monte, I think this potential problem
is quite manageable. As for other
operational aspects, TSTO may
actually have advantages over SSTO.
For example, powered landing of the
carrier stage--or aborted landing of the
two-stage system is quite reasonable
for TSTO, but not for SSTO.

Also, SSTO has horrible off-design performance (increasing altitude or
inclination), because of the large dry mass. For instance, it would
be absurd to go to the moon in a single stage (though refueling the
same vehicle may make sense under some circumstances).

There's a reason we stage. Ideally, one wants to find an affordable
sweet spot between minimizing operational complexities of staging
and/or payload transfer, and minimizing vehicle dry weight.

In article
,
wrote:

The Ansari X prize was great but then we see all these guys who say
they will make money sending people into 5 minutes of weightlessness.
Do you buy this?

I sure would if I had that much disposable income. As it is, I'll have
to let the thousands of wealthier passengers who are already signed up
be the trailblazers, and wait until the price comes down for myself.

You might say that this is a step towards an orbital market but all
you have to do is to compare E=mgh to E=1/2 mv^2 where v is orbital
velocity to see that suborbital isnt a real step toward orbital.

No, you'd have to do a great deal more than that, and of the people who
have seriously done so, at least some of them see it as a useful step.
(Those who don't are generally contemplating a very different path to
orbit than those who do, and that's OK -- we shouldn't be trying to
choose which path is best, but instead just let the market sort it out.)

For orbital, you gotta carry a whole lotta fuel and I dont see Virgin or
Blue Origin or the others trying to do so.

Then maybe you're not looking forward far enough.

--
"Polywell" fusion -- an approach to nuclear fusion that might actually work.
Learn more and discuss via: http://www.strout.net/info/science/polywell/

In article ,
Harri Tavaila wrote:

As has been pointed out there is the obvious path of expansion to
develope a TSTO based on a suborbital vehicle with considerable payload
capacity.

And then there are less obvious paths of expansion, such as a suborbital
vehicle that docks (or transfers payload to) a rotovator.

--
"Polywell" fusion -- an approach to nuclear fusion that might actually work.
Learn more and discuss via: http://www.strout.net/info/science/polywell/

In article
,
Len wrote:

Sure, going to orbit is going to be more expensive--but not
necessarily that much more difficult than suborbital. However, the
ratio of potential market to investment is far better with orbital
than with suborbital.

Well, if you're right, I think you'll find the investment climate much
more receptive to it after suborbital flight has become routine. That's
the point at which wealthy customers will want something new, and if you
can come along with a safe orbital launch system that is not that much
more difficult than the suborbital systems already in service, you
should have no trouble raising money for it. Compare that to now -- or
even more so, five years ago -- when your proposal for a commercial
orbital launch system would most likely get laughed out of the room.

So, if nothing else, the suborbital market should quell the laughter and
loosen the purse strings for orbital enterprise.

--
"Polywell" fusion -- an approach to nuclear fusion that might actually work.
Learn more and discuss via: http://www.strout.net/info/science/polywell/

On Nov 24, 6:28 pm, Joe Strout wrote:
In article
,

Len wrote:
Sure, going to orbit is going to be more expensive--but not
necessarily that much more difficult than suborbital. However, the
ratio of potential market to investment is far better with orbital
than with suborbital.

Well, if you're right, I think you'll find the investment climate much
more receptive to it after suborbital flight has become routine. That's
the point at which wealthy customers will want something new, and if you
can come along with a safe orbital launch system that is not that much
more difficult than the suborbital systems already in service, you
should have no trouble raising money for it. Compare that to now -- or
even more so, five years ago -- when your proposal for a commercial
orbital launch system would most likely get laughed out of the room.

The investment climate argument is about the
only reason that I've had any tolerance at all to
the suborbital (low speed at 100 km) strategy.
I think this is false thinking on the part of the
investment community; however, that doesn't
mean that it isn't real.

As for being laughed out of the room five years
ago, how about 40 years ago, when I first tried
to raise money for an orbital system.

So, if nothing else, the suborbital market should quell the laughter and
loosen the purse strings for orbital enterprise.

Whatever works. We're hopeful the direct
investment approach is finally going to work.

Len

--
"Polywell" fusion -- an approach to nuclear fusion that might actually work.
Learn more and discuss via: http://www.strout.net/info/science/polywell/