MIT Rocketlab's How to Design Build and Operate Liquid Fueled Rocket Engines

Anyone here used the information from this book? I'm trying to do some
design based on it, although I've found in a couple of places the formula's
make great leaps with no explanation. The main one I'm having problems with
is Step 9.

start quote
The chamber length is found from Eq. (21)


Vc = (1.1) (Ac Lc)


However, we must first determine the chamber area or Ac. We do this by
assuming that the chamber diameter is five times the nozzle throat diameter
or Dc = 5Dt, therefore


Dc = 1.2 in. and Ac = 1.13 in2
Therefore,


Lc = Vc/(1.1)(1.13) = 2.67/1.245 = 2.15 in
end quote

Having a chamber volume of 2.67 in^3 and calculating the the chamber
diameter by Dc = 5Dt, the cross-sectional area of the chamber should be Ac
= 2 pi r = pi * Dc as far as I can tell. But they introduce a figure 1.13
in^2 for Ac, with no explanation. On the formula page they provide a
formula for Ac:

Ac = Dc^2 / 4

This produces a value of 0.35 in^2. Any ideas on what is going on here? What
is the correct value? I've been trying to follow their example so I can
build and validate a spreadsheet for such calculations, but I'm stuck here.
I've also been trying to convert the formulae to metric. Has anyone already
converted it?

Secondly, is there a better publication out there to superseed this book?
This book is aimed at static test articles, do other publications apply
more to flight articles? Lastly, how well will these values apply to an
aerospike type of engine, specifically an annular version? Would I be able
to use the same areas and volumes effectively? Thanks,

David

P.S. Sorry for the cross post, but being a historical book now I think it's
relavent to both.