On Fri, 22 Jun 2001, Alberto Monteiro wrote:
> Gautam Mukunda wrote:
> >> India has recently launched a satellite; and an ICBM is much
> >> simpler than a satellite.
> > Are you sure?
> No, but your question did motivate me to do some calculations.
>
> But now I am convinced that it's easier to put a satellite in orbit
> than launch an ICBM - because a satellite may be of any
> size, and a nuclear warhead has a minimum size.
>
> > I'm not a hundred percent certain that is the case. Didn't
> > the Soviets launch Sputnik before they had ICBMs?
> Yes, but as soon as Sputnik was launched the world was
> aware that they had the power to send a nuke anywhere they
> wanted.
Well, that was the world's belief, but it wasn't necessarily the case,
after all. Even by the time of the Cuban missile crisis the Soviets had
only a handful of ICBMs of questionable reliability, and that was years
later.
> > For that mattter,
> > there's the question of miniaturization. I'm not sure what the status of
> > Indian nuclear technology is, but it's at least possible that they haven't
> > miniaturized enough for practical use in ICBMs.
> 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. 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.
> > Certainly the Indian
> > nuclear tests that caused such a stir a few years ago were not entirely
> > successful - most were fizzles, I believe. Finally there's the question
> > of reentry, right, which is something that satellites don't have to deal
> > with.
> 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.
<snipping your math - I agree with all of it anyways>
> 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.
>
> Alberto Monteiro
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? 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.
Gautam
