rockets of all kinds

I notice that Dow Reider is bitching about the "fusion rocket" in MT.
Admittedly, he has excellent reasons to bitch.  However, I notice that
noone has bothered to say anything rude about the OTHER rocket types
presented in Hard Times and COACC.
Herein are my own complaints:

    1)  Basic and advanced rocket - specific impulse 16000+ each.  The SSME
has a specific impulse of 459 (last I heard).

    2)  The Nuclear thermal rocket (NERVA, I presume?) - specific impulse
is 550,000+.   The NERVA we built a few decades ago was tested on the
ground at a specific impulse of 780-odd.  It was expected to reach 800+ in
actual operation.  The most wildly optimistic extrapolations of the NERVA
produced specific impulse in the range of 10,000 at most, if certain
insurmountable problems could be overcome by future materials technology.

    3)  he "resistojet" - specific impulse 1.8 (salute!).  Admittedly, this
is a steam rocket out of a boiler, but REAL steam engines produce steam
with specific impulse much higher than that, by a factor of 10 to 100,
depending on steam pressure.

    4)  Likewise the mass driver rocket.  specific impulse 100.  Real  ones
were cobbled together in labs with ten times the specific impulse.  There
was not found to be any real difficulty making them ten times better still.

    5)  The ion rocket - It is hard to argue with a system so open-ended as
an ion rocket, but I will anyway.  specific impulse 1,200,000.  Most
real-world design work has produced ion drives with specific impulse less
than 50,000.  There is no good reason that an ion drive could not have ANY
specific impulse less than light speed.  It's just inefficient to do so.
MY big quibble is the power required.  Their ion drive SHOULD use at least
2.88+ Gw per unit.  It uses 500 Kw per unit.  MIRACULOUS PERFORMANCE!  The
mind boggles...

    6)  The solid rocket - specific impulse 3000.  Real world examples
seldom reach 300.

    7)  The others - mostly have been bitched at by other experts.  My 2
cents worth would be wasted.

    8)  The LALV (Lift-Assisted Launch Vehicle).  What a concept!  A NASP
(National Aero-Space Plane) that uses more fuel than an equivelant-sized
rocket.  The LALV uses FAR more fuel than a straght rocket, and requires
more engine weight and less payload.  SO WHAT'S THE POINT???  Why build a
device that doesn't work as well as the nearest alternative?

    And 9)  The notion (used in Hard Times_[}, and on Rob Dean's recent TL8
rocket posted here) that any sane man would put battleship armor plate on a
rocket of any kind.  factor 40 armor is equivelant to over 13" of steel
(33.6 cm to all of us who use SI as a way of life).  Putting that kind of
armor on a rocket is less reasonable than doing it on your automobile.  A
more realistic figure would be armor 8 (or perhaps 4).  Then the
performance of your machine would be higher, and the cost would be lower.

Later...

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I have learned to use the word "impossible" with the greatest caution.
                                    --W. von Braun