market size as a function of launcher size

Parallax wrote:

Dick Morris wrote in message ...
Parallax wrote:

Although it would be very nice to have a very heavy launcher like
Saturn V or Energia, there is little market for it. The small market
doesn't justify development or the infrastructure for it. The market
can handle various smaller launchers. Is there any way to use
combinations of smaller launchers to achieve a very heavy launcher
when it is needed without developing the infrastructure for the very
heavy launcher?

A medium-lift (which I define to be 40-80,000 lb. payload) launcher can
substitute for an HLLV in some circumstances, such as manned lunar or
Mars flights. A large majority of the Initial Mass in LEO (IMLEO) of a
lunar or Mars ship will be propellants, which are easily divided into
smaller packages. Several tanker flights of a medium-lift RLV can
deliver propellants to a propellant depot in LEO. An additional flight
can deliver the hardware, which is then docked to the propellant depot
where the tanks are filled. That eliminates the need for an HLLV and
gives us a vehicle which can be used for many other purposes as well.

In some cases, this could work. However, if the medium lifter is
expensive, then several are even more so.

My proposal is for a medium-lift, VTOL RLV, so the recurring cost would
be quite low. The recurring cost for the 4-6 RLV flights to do a manned
lunar or Mars flight would be much less than the recurring cost of an
expendable HLLV required to launch the same payload mass.

Is the cost proportional to
the number of launches? Would the cost be significantly less with
fewer but larger launches? Truax says the cost does not increase
significantly with rocket size so big rockets are about the same
overall cost as smaller ones to launch (cost is mostly overhead).

The total cost-per-flight is not a linear function of either vehicle
size or flight rate. Other factors being equal, a large rocket will
have a lower recurring-cost per pound of payload than a smaller rocket
due to economies of scale, but the large rocket will have a lower flight
rate for a given mass of payload delivered to LEO, so the fixed-cost per
flight will tend to be higher. You'd have to plug some actual numbers
into a spreadsheet to know which is cheaper.

However, there is little need for HLLV but when it is needed, it might
really save $ if the development and overhead cost ws not much more
more than a smaller rocket. So, this means that clustering smaller
rockets might make sense if these smaller rockets are used when
smaller payloads are desired.

Clustering of existing booster stages would work, and would save a
substantial amount of development cost vs. starting from scratch with a
unitary design. Historically, development cost tends to scale as the
dry mass to the 2/3 power, so even if the clustered module was a new
design, it would save a significant amount of development cost vs. a new
unitary design.

For this, hybrids might really make sense. They are fairly simple and
reliable with better performance than pure solids. They are almost
environmentally benign and some of the fuels (and oxidizers) are very
safe and easy to handle. Maybe the H2O2/Wax combination would be good
for this.

Here's a program for calculating the performance of propellant
combinations:
http://www.dunnspace.com/isp.htm

One could imagine very cheap production of many of these engines and
an easy clustering system for arbitrary enlargement. Tow the cluster
to near the equator in the ocean away from silly govt regs, tilt it
upright as in Seadragon and launch. Each engine could be fed from a
common oxidizer tank with its valve independently controlled to
balance the cluster thrust or to shut one down if it went bonkers.
Outer engines in cluster could be fed oxidizer to burn faster for
faster staging and then are ejected from the core. Inner engines
initially have low thrust but on staging they pour it on.
Forget reuseability, this is cheap enough to throw away after each
use.

I disagree that there will ever be a launch vehicle that's cheap enough
to throw away after each flight and be low enough cost to generate any
significant new markets. If Mr. Truax, or anybody else, thinks they can
prove otherwise, they are certainly welcome to try.

No nasty Nitrogen tetroxide, no ammonium perchlorate, no
cryogenics, just cheap, reliable, few safety problems and
environmentally benign.
I know I greatly oversimplify, but basically take a large wax
cylinder, drill a hole down the middle, wrap the outside with
fibreglass cloth, carbon fiber matting using boat building technology
so its done in quantity, add the nozzle and pressure and temp guaging,
and a computer controlled throttle valve. Oxidizer tanks are made
from welded Al with carbon fiber matting around outside resined on.
Its just a Little Dumb Booster that can be clustered to make various
sized Big Dumb Boosters when needed.

The devil's in the details ;-). (A company by the name of OTRAG tried
something similar back in the late 70's and was not successful. Don't
remember exactly why. Their modules used pressure-fed storable
liquids.)

I clearly have too much time on my hands since I know little about
rockets.

Use some of the first problem to deal with the second. Get a copy of
"Rocket Propulsion Elements" by Sutton for a comprehensive treatment of
the principles of rocket propulsion. See also a book called "Modern
Engineering for Design of Liquid-Propellant Rocket Engines" by Dieter
Huzel (one of the Von Braun team at Peenemunde), and others, for more
details on actual hardware design. Those are college level books, but
you can certainly find more basic information on the web if you want to.

On Tue, 23 Sep 2003 20:50:02 GMT, in a place far, far away, Dick
Morris made the phosphor on my
monitor glow in such a way as to indicate that:


I disagree that there will ever be a launch vehicle that's cheap enough
to throw away after each flight and be low enough cost to generate any
significant new markets. If Mr. Truax, or anybody else, thinks they can
prove otherwise, they are certainly welcome to try.

Sea Dragon was meant to be reusable.

--
simberg.interglobal.org * 310 372-7963 (CA) 307 739-1296 (Jackson Hole)
interglobal space lines * 307 733-1715 (Fax) http://www.interglobal.org

"Extraordinary launch vehicles require extraordinary markets..."
Swap the first . and @ and throw out the ".trash" to email me.
Here's my email address for autospammers:

Rand Simberg wrote:

On Tue, 23 Sep 2003 20:50:02 GMT, in a place far, far away, Dick
Morris made the phosphor on my
monitor glow in such a way as to indicate that:

I disagree that there will ever be a launch vehicle that's cheap enough
to throw away after each flight and be low enough cost to generate any
significant new markets. If Mr. Truax, or anybody else, thinks they can
prove otherwise, they are certainly welcome to try.

Sea Dragon was meant to be reusable.

OK. Make that "If anybody thinks..."

--
simberg.interglobal.org * 310 372-7963 (CA) 307 739-1296 (Jackson Hole)
interglobal space lines * 307 733-1715 (Fax) http://www.interglobal.org

"Extraordinary launch vehicles require extraordinary markets..."
Swap the first . and @ and throw out the ".trash" to email me.
Here's my email address for autospammers: