At 05:50 AM 6/22/01, Alberto Monteiro wrote:
>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.
> >
FWIW, "Little Boy" was 10 feet (3.048 m) long and 2 feet 4 inches (71.12
cm) wide, while "Fat Man" was 10 feet 8 inches (3.2512 m) long and 5 feet
(1.524 m) wide.
>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!]
Bet you can find it on the Internet.
(I happen to know the answer, but it's not that hard to find. It's not
like it's still secret after 60 years. You could easily carry it. Though
probably not after you put enough shielding around it to make it safe for
you to carry.)
> >
> >> 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!
Little birdie in the sky,
Why'd you do that in my eye?
Little birdie, flying high,
I'm so glad elephants can't fly.
>[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
Early satellites:
USSR:
Sputnik 1 (October 4, 1957) 184.3 lb (83.6 kg)
Sputnik 2 (November 3, 1957) 1121 lb (508.3 kg) with dog Laika as passenger
Sputnik 3 (May 15, 1958) 2,926 lb (1,327 kg)
USA:
Explorer 1 (January 31, 1958) 31 lb (14 kg)
Vanguard 1 (March 17, 1958) 3 1/4 lb (1.47 kg)
>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 :-)]
-- Ronn! :)
