Big Dumb Boosters (was Re: FT3, details of needed changes)

Excerpts from FT: 8-Oct-96 Re: FT3, details of needed .. by Oerjan
Ohlson@nada.kth.s 
> On Mon, 7 Oct 1996, Aaron P Teske wrote:
> > Anyway, if anyone wants a copy of an article on this, just let me
know. 
> > (Or I could post it; it's only 4-5K or so.)
>  
> Yes please! It's always nice to check fantasy with facts <g>

Eh, what the heck... here she comes.

		    Aaron Teske
		    Mithramuse+@cmu.edu
		    Space Fleet web page at:
		   
http://www.contrib.andrew.cmu.edu/usr/at2u/sfleet.html
---cut here---
Newsgroups: sci.space
From: dietz@cs.rochester.edu (Paul Dietz)
Subject: Sea Dragon (was Re: reviving saturn v)

In article <CL6qLx.M22@cscns.com> random@cscns.com (Doug Jones) writes:

> Hey, people, if we're going to resurrect a heavy lifter from the
sixties, do
> it right-- build Sea Dragon.

Time to repost the passage from Ed Regis's "Great Mambo Chicken"...

--------------------

The Sea Dragon was a launch vehicle of stupendous proportions that
Truax had designed back when he was director of advanced development
at Aerojet General.  The best perk of that high office was the $1
million budget that he could spend any way he wanted to.  Truax used
it to test his pet theory that the *cost* of a rocket had nothing to
do with how *big* the rocket was.  You could make a given rocket just
as big as you pleased and it would cost about the same as one that was
about half the size, or smaller.

This went against conventional wisdom and common sense, but at Aerojet
Truax collected enough facts and figures to prove its truth beyond a
doubt.	Indeed, he'd been assembling the necessary data from the time
he'd been in the navy, where he'd had access to all sorts of cost
information.

Take Agena versus Thor, for example.  These two rockets were identical
in every way: each had one engine, one set of propellant tanks, and so
forth; the only significant difference between them was size.  The
Thor was far bigger than the Agena, but the surprise was that the
*bigger* rocket had cost *less* to develop.

"I was shocked to discover the Agena cost more than the Thor," Truax
said later.  "The Thor was between five and ten times as big!  I said
to myself, We've been tilting at windmills all this time!  If all
rockets cost the same to make, why try to improve the
payload-to-weight ratio?  If you want more payload, make the rocket
bigger."

The same anomaly cropped up again in the case of the two-stage Titan I
launch vehicle: the upper stage was *smaller*, a miniature version of
the lower stage, yet the smaller stage cost *more* to make.

It seemed irrational, but all of it made sense once you went through
the costs item by item.  Engineering costs, for example, were the same
no matter what the size of the rocket.	"You do the same engineering
for the two vehicles, only for the bigger rocket you put ten to the
sixth after a given quantity rather than ten to the third or
whatever," Truax said.

The same was true for lab tests.  "The cost of lab tests is a function
of the size of your testing machine and the size of the sample you run
tests on, not the size of the product."

Ditto for documentation, spec sheets, manuals, and so forth.  The cost
here was a function of the *number* of parts and not the *size* of the
parts.	"There are absolutely no more documents associated with a big
thing than a small thing, as long as you're talking about the same
article."

By this time Truax had accounted for a healthy chunk of the total cost
of a given launch vehicle.  About the only thing that *did* vary
directly with a rocket's size was the cost of the raw materials that
went into making it, but raw materials constituted only *2 percent* of
the total cost of a rocket.  "Two percent is almost insignificant!"
he said.  "And even with raw materials, if you buy a ton of it you get
it at a lower unit price than if you buy a pound.  And this is
especially true of rocket propellants."

So if all this was true, if engineering, lab tests, documentation and
so forth didn't determine a launch vehicle's price tag, *what did*?
Essentially, three things: parts count, design margins, and
innovation.  Other things being equal, the more parts a machine had,
the more it was going to cost.	The more you wanted it to approach
perfection, the more expensive it would end up being.  And finally,
the newer and more pioneering the design, the more you'd end up paying
for it.

"We came up with a set of ground rules for designing a launch
vehicle," Truax said.  "Make it big, make it simple, make it reusable.
Don't push the state of the art, and don't make it any more reliable
that it has to be.  And *never* mix people and cargo, because the
reliability requirements are worlds apart.  For people you can have a
very small vehicle on which you lavish all your attention; everything
else is cargo, and for this all you need is a Big Dumb Booster."

--------------------

	Paul F. Dietz
	dietz@cs.rochester.edu

	"If I'd been in my grave, I'd have rolled over."
		R. Truax on the decision to build the Space Shuttle