Gautam Mukunda wrote:
>
>> But why would an ICBM have to be miniaturized? An ICBM must carry,
>> at least, the critical mass of the nuclear reaction, so they
>> have a _minimum_ mass.
>
>I'm afraid I'm missing something here.
>
Probably _I_ am missing something here. "Ne sutor supra
crepidam" is something I must always remember.
>Miniaturization technology was a
>reference to miniaturizing the _warhead_, not the missile itself. The
>original nuclear bombs were so enormous a new bomber had to be designed to
>carry them. The first fusion weapons were so huge that only a ship could
>carry them. It took hundreds of brilliant engineers many years to shrink
>the warheads down to a usable size.
>
Ok, but there's still the problem of the minimum critical weight. What's the
critical mass for Plutonium-239 or Uranium-235? [hi, Echelon! We are
just kidding!]
>
>> Mathematically, the reentry is a similar problem to the exit,
>> because you must cross the athmosphere with a huge speed.
>
>Is it really? I was under the impression that reentry is a more difficult
>problem to deal with because during launch the thickest parts of the
>atmosphere are crossed at the lowest speeds, while during reentry the
>oposite is the case.
>
I didn't consider this point - yes, you may be right.
>
>> Conclusion: even though the Delta-V required to send
>> an ICBM is lower than the Delta-V required to put a
>> satellite in orbit, the "minimum size" requirement for a
>> nuke compensates that, so that a satellite program is
>> slightly more complex than an ICBM program.
>
[[this comes from posting at night while at the same time
(a) trying to calm down one baby that had been awake for
the past 15 hours (b) trying to convince two pre-teens that
it's time to sleep. I wrote the opposite that I thought!!!]]
>OK - now I'm not sure what you believe, Alberto :-) In your opening you
>seem to say that launching a satellite is easier than launching an ICBM -
>in your conclusion you're saying that it's harder. Am I misunderstanding
>you somewhere (presumably I am), and if so, which one am I
>misunderstanding?
>
Err... Look! Over there! a flying elephant! [now I get back to the
board and erase what I wrote and replace it by:
the "minimum size" requirement for a
nuke compensates that, so that a satellite program is
slightly more simple than an ICBM program
What are you talking about? Where did I contradict myself?
>Thanks for doing the math, btw - it's been years since
>I worked through a problem like that, and it was a lot of fun.
>
I will make some pictures and post them [I feel tempted to send
them in the message, but I know that those that get brin-l by
digest will killfile me :-)]
Alberto Monteiro
