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:

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

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."

[article snipped]

Fun!

Now what about relative engine power as a function of the size...?:)

Very interesting article! Thanks, Aaron!