My CATS concept.

"charlie" wrote in message ...
(ed kyle) wrote:

vehicle, it would only be capable of putting 13.5 tons into low
earth orbit (assuming 420 sec ISP and 9000 m/s ideal delta V, before
gravity and drag losses). That includes both the payload mass

Point 3: Total delta V for the TWO rocket stages can probably be
as low as 8500m/s and still reach LEO, or so I've read for airlaunch.

I'll accept that. 8500 m/s is about what Pegasus XL produces
for a 440 kg payload carried to a 185 km orbit.

Point 4: TWO stages. Boosters are dropped after about 2500m/s,
and make a parafoil recovery. That alone adds about than 3 tons
to the total mass delivered to LEO. Don't limit your mindset to the
SSTO mentality.

I don't know what your booster mass is, so I calculate:

420 * 9.805 * ln[120 tons/X] = 3000 m/s

(assuming 3000 m/s ideal delta V to offset gravity
losses in order to reach your 2500 m/s staging velocity)
for first stage flight, where X is the mass remaining
at the end of first stage flight, including the empty
mass of both boosters. This gives X = 58 tons, indicating
that the booster propellant mass is 62 tons.

The closest vehicle that can compare with your design
would be Kistler K-1. Its recoverable first stage was
projected to have a gross mass of 250 tons and a dry
mass of 20.5 tons, or a mass fraction of 12.2. Using
this mass fraction, your boosters would have a total
dry mass of 62/12.2, or about 5 tons. Your core stage
plus payload mass would then be 58 - 5 = 53 tons.

Second stage flight, then, would be:

420 * 9.805 * ln[53 tons/Y] = 5500 m/s

where Y = 14 tons is the mass injected into orbit.

The key question is, how heavy does your recoverable second
stage have to be? The recoverable Kister K-1 second stage
design was projected to have an on-orbit mass of 13.1 tons
for a 4.5 ton payload (a factor of about 3). X-38 had a
mass of about 8 tons and a payload of about 1.5 tons (a
factor of about 5). Let's split the difference and use
a factor of 4. That gives:

(14-PL)/PL = 4

so that

PL mass = 2.8 tons

the more optimistic 3 factor gives a 3.5 ton payload mass,
about equivalent to a Titan II (which also has about a
120 ton GLOW, BTW).

That's O.K., but realize that only 9 of the 39 space
launches conducted worldwide so far this year were
performed by launch vehicles of this payload class or
smaller. The busiest rockets are Soyuz/Molniya and
Delta II (5-7.5 tons to LEO), which have flown 14 times
and the various big GTO launchers (typically 5 tons to
GTO or 12-20 tons to LEO), which have flown 15 times.


Why not dispense with the carrier jet and launch vertically?
The carrier jet adds little velocity and it limits your gross
take off weight.

Good question. It brings us to:

Point 5: Vertical Launch facilities can be quite expensive.
Ask anyone who builds/operates them. If you can leverage the
existing infrastructure of an airport, you can lower your
startup costs.


A new 747-400, your launch facility, can cost $150 million.
You would have to modify it and certify the new design, an
effort that would add a few more tens of millions. Right
there you've just about equalled the cost of building a
fixed pad for a vehicle of this size.

Then there is the operating cost. It will probably cost
$8,000-10,000 per hour to fly the plane, not including crew
costs, etc. Your airborne launch pad would require more
intensive maintenance than a fixed ground-based structure.
There will be other costs involved with tracking and
communicating with your flying launch pad.

Point 6: By using a carrier jet, your first-stage boosters can
land near your takeoff point, while avoiding the risks of
having a rocket that might lose power and crash over land.


On paper, air launch does offer flexibility and the possibility
of infrastructure savings. Your single flying "launch pad"
would be able to launch from more than one site. A ground based
launch system would require a new pad at each site. It only
pays off if you expect to launch from multiple sites.

- Ed Kyle

Rand Simberg wrote:

On Wed, 27 Aug 2003 08:37:04 +0300, in a place far, far away,
"charlie" made the phosphor on my monitor glow in such a way
as to indicate that:

I tried posting this to sci.space.tech, but it didn't go up.

Some ISPs, including mine, seem to have trouble with moderated
groups that don't have an indication that they are moderated in their
title. Mine has been on-and-off. I used to be able to successfully
post from adelphia.net but no longer. Since Adelphia is in bankrupcy
I don't have much hope things will get changed so, unfortunately, some
technical stuff will have to be posted to the "catch-all" policy group.



My Concept for a fully-reusable 2 and 1/2 stage design:

Who cares?

Rocket designs are a secondary (at best) issue when it comes to
reducing launch costs. Figure out how to raise the money, and get
back to us.

Some of us like to read this stuff. However, I couldn't help note
all of the innovative stuff mentioned and come to the belief that it
was not only going to take big bucks to develop the concept, but
that $500K per flight sounded quite low.

Rand, you may regard rocket designs as a secondary issue compared
to raising money, but raising money from people requires a credible
concept and that has to come first.

This includes suborbital tourist traffic. In order to raise the money
you have to have some kind of a concept fairly well defined.

Mike Walsh

Rand Simberg wrote:

On Wed, 27 Aug 2003 20:25:02 -0400, in a place far, far away, Alain
Fournier made the phosphor on my monitor glow
in such a way as to indicate that:

I get a little tired of people who think that the problem is going to
be solved by drawing pictures of rockets.

Maybe you should go to another newsgroup. This is the place to discuss a
"Concept for a fully-reusable 2 and 1/2 stage design".

No, it's not actually. That's sci.space.tech. This is the newsgroup
to discuss space policy.

Well, that is fine, but being able to post to sci.space.tech or other
moderated newsgroups is sometimes a function of the Isp. I suppose
we could take the alternate route I once saw mentioned of emailing
moderator George Herbert in order to get posts into the group, but
it is annoying not to be able to post comments on other people's
posts.

And you are wrong.

Fully reusable rocket designs from commercial groups are an
integral part of space policy.

Mike Walsh

charlie wrote:

ed kyle ) wrote:

Why not dispense with the carrier jet and launch vertically?
The carrier jet adds little velocity and it limits your gross
take off weight.

I left out (perhaps) the most critical point.

Point 8: Vertical rocket launch from the ground requires the use
of sea-level capable rocket engines. The only existing rocket
engine that I would consider "sufficiently re-usable" for 100's
of missions that is also sea-level capable is the RL10-5, which
has low thrust and would have to be clustered in a big way.

The relatively low pressure RL-10 engine is not suitable as a
sea-level engine for anything other than test purposes where you
really don't care about performance, such as the DC-X.

The
Russian NK-33/RD-180 class engines are only re-usable 10-20
times, and the SSME requires expensive and time consuming service
between launches. Launch from 12km altitude allows you to use
better, more re-usable engines on your rocket without SL support.

For that matter, I don't believe you can count on 100 flights of
a standard RL-10. "Only re-usable 10-20 time" is pretty good
for an already designed and built engine.

These are just side comments. Air launch is a valid idea. You
might search around for some of Len Cormier's proposals.
Yours seems to be around the same lines.

Len's proposals for air launch look as good as any I have seen
detailed in this newsgroup. I do think that both your concept
and his will be more expensive than expected, but that is another
story.

Mike Walsh

John Carmack wrote:

Michael Walsh wrote in message ...
charlie wrote:

ed kyle ) wrote:

Why not dispense with the carrier jet and launch vertically?
The carrier jet adds little velocity and it limits your gross
take off weight.

I left out (perhaps) the most critical point.

Point 8: Vertical rocket launch from the ground requires the use
of sea-level capable rocket engines. The only existing rocket
engine that I would consider "sufficiently re-usable" for 100's
of missions that is also sea-level capable is the RL10-5, which
has low thrust and would have to be clustered in a big way.

The relatively low pressure RL-10 engine is not suitable as a
sea-level engine for anything other than test purposes where you
really don't care about performance, such as the DC-X.

That is the classic aerospace error -- that something lower in
performance is automatically not suitable. I could quite easily
imagine designs where a cheap, highly reusable engine is more suitable
than a higher performance engine that costs a lot and requires a bunch
of maintenance, even if it gives up quite a lot of performance. I'm
not an authority on production engines, but I suspect that a TSTO RLV
built around RL-10s might well be a better overall design than one
built around, say, SSMEs.

The "performance" that comes from pressure, which is an Isp increase,
is not the important metric for system design. Cost effectiveness
does not seem to be strongly correlated with Isp, and, in fact, with
current launchers seems to have a negative correlation, as the
cheapest launchers are not hydrogen fueled.

John Carmack
www.armadilloaerospace.com

Nope. If you wish to launch large payloads into orbit from sea level you
will have some performance limitations. At sea level conditions you have
a 14.7 psia back pressure and low pressure engines take a big penalty.
Unless you start playing around with the fuels, as proposed, for the
upper stage the RL-10 also has the penalty that you mentioned of
being hydrogen fueled.

You are not going to face that kind of a problem on an X-Prize
vehicle but you will if you are trying to build a credible orbital
launcher.

I claim that a clustered RL-10 first stage would not be competitive
costwise with a set of SSMEs.

I might as well be insufferable and say you could argue the point,
but you would be wrong. I think you would be on sounder ground
arguing that neither one of them is a good choice.

However, Boeing seems to believe in a LO2-LH2 combination with
their RS-68 engine that builds a lower cost expendable engine with
less performance than the SSME.

Mike Walsh

Michael Walsh wrote:
John Carmack wrote:
The "performance" that comes from pressure, which is an Isp increase,
is not the important metric for system design. Cost effectiveness
does not seem to be strongly correlated with Isp, and, in fact, with
current launchers seems to have a negative correlation, as the
cheapest launchers are not hydrogen fueled.

Nope. If you wish to launch large payloads into orbit from sea level you
will have some performance limitations. At sea level conditions you have
a 14.7 psia back pressure and low pressure engines take a big penalty.
Unless you start playing around with the fuels, as proposed, for the
upper stage the RL-10 also has the penalty that you mentioned of
being hydrogen fueled.

You are not going to face that kind of a problem on an X-Prize
vehicle but you will if you are trying to build a credible orbital
launcher.

The backpressure hurts porportionally less if you go to
more rather than less stages.

I believe that a credible case can be made for an expendable
multi-stage lifting off with sea level ISP as low as ... oh, 150.
I will not justify that in detail for a couple more weeks, though.


-george william herbert

charlie wrote:
I tried posting this to sci.space.tech, but it didn't go up.

My Concept for a fully-reusable 2 and 1/2 stage design:

1) The Zero-Stage: Modified 747-class turbojet
Carries a 120-150 ton rocket to 12km altitude, 300m/s


Did you consider other first stage carriers?

An-124 - takes 120 tons as is
Airbus 380 freight - takes 150 tons as is

the first is available now, the second relatively soon. Even
getting more An-225s custom built might be cheaper than a 747
derivative, and would of course give much more cargo handling
capability

Biut you have to be of a mindset that allows non-US components.

--
Sander

+++ Out of cheese error +++

ed kyle wrote:

Then there is the operating cost. It will probably cost
$8,000-10,000 per hour to fly the plane, not including crew
costs, etc. Your airborne launch pad would require more
intensive maintenance than a fixed ground-based structure.
There will be other costs involved with tracking and
communicating with your flying launch pad.

Point 6: By using a carrier jet, your first-stage boosters can
land near your takeoff point, while avoiding the risks of
having a rocket that might lose power and crash over land.


On paper, air launch does offer flexibility and the possibility
of infrastructure savings. Your single flying "launch pad"
would be able to launch from more than one site. A ground based
launch system would require a new pad at each site. It only
pays off if you expect to launch from multiple sites.

Isn't fast turnaround the other plus for a plane based first stage?
Planes are sedigned to launch several times a day (just imagine
the plane takiong weeks to be readied? no way). So you could be
limited by as to how fast you can load the next stages into the plane
and launch say daily.


- Ed Kyle

--
Sander

+++ Out of cheese error +++

There are a zillion workable launcher concepts out there, none of them
has really generated enough investment to be test flown into space.
Good luck to you in getting that investment.

I believe that William Mook used to pollute sci.space.policy with his
Design of the Week, and the newbies would all end up arguing about ISP
and the like. I also suggest moving these conversations to
sci.space.tech where there are people who know this stuff.

Anyway, I won't charge you for this, but the secret to making a 747
class aircraft useful in this area is to outfit it with 777 engines.

Michael Walsh wrote:
George William Herbert wrote:
Michael Walsh wrote:
[...]
You are not going to face that kind of a problem on an X-Prize
vehicle but you will if you are trying to build a credible orbital
launcher.

The backpressure hurts porportionally less if you go to
more rather than less stages.

I believe that a credible case can be made for an expendable
multi-stage lifting off with sea level ISP as low as ... oh, 150.
I will not justify that in detail for a couple more weeks, though.

I would assume you would want to stage rather quickly or
possibly have a very large first stage.

A TSTO lifting off with Isp of 150 would be In A Bad Way;
staging a lot helps a lot if you're optimizing stages for
their conditions to the detriment of other flight regimes.

Back to the "big dumb booster" argument?

We left it? 8-)

Then you get back to the pressure fed engines with very low
cost engines and tank materials. And you then get into trade-offs
with solid propellant systems.

Right.

Safety concerns alone suggest against solids.
VLS-3 and the pour that exploded at the San Jose
plant a few weeks ago are plenty of evidence
that those risks are ongoing...

I see you removed my claim that someone might disagree with
me, but they would be wrong. I admit to just saying that to be
a bit insufferable but you didn't rise to the bait. The case is,
truly, arguable.

Lots of things are arguable. One of the things that isn't is
that different system approaches are going to optimize in radically
different ways... so trying to argue optimization separately from
system approach is likely to be frustrating 8-)

Overgeneralization is an enemy as always.


-george william herbert