From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: SDI update
Date: Fri, 10 Apr 1992 19:21:56 GMT
Organization: U of Toronto Zoology

In article <GABRIELE.92Apr9094352@solecism.aero.org> gabriele@aero.org (Mark Gabriele) writes:
>>For another, if worst comes to worst, you can always send a maintenance
>>crew up to hit it with a rock...
>
>This assumes that you *can* send up a maintenance crew...

Uh, so does the "blow up the Patriot with a grenade" approach.  What reason
might there be for us *not* being able to send up a maintenance crew?  Bear
in mind that (a) "we" has a good chance of including Russia now, (b) even
in the post-Challenger hiatus, the US had the capability to fly a shuttle
mission in an emergency, and (c) if maintenance access is deemed crucial,
it's no big trick for the US to set up a quick-reaction manned launch
system to assure maintenance access -- the US has a man-rated launcher
(Titan II) that was built to sit on standby for years and then react
in minutes.

>and that the
>system doesn't think that they are an enemy and try to shoot them
>down...

Just how big and how credible a failure are we talking about here?  We
*were* talking about failures of individual interceptors, not the entire
system going berserk.

>there's NO WAY to turn it off...

Oh come now.  In literature, there is the notion of an "idiot plot", a
sequence of events that is plausible only if all the characters involved
are idiots.  Let us not discuss idiot systems, which would be launched
only if all the designers were idiots.

As I said before, this is what destruct systems are for:  to absolutely,
positively disable a malfunctioning rocket.  We *know* how to build such
things so we have control over them even when malfunctions occur.

>... Those are the only 100% certain ways to deactivate it.

I will say this again, for the last time:  why are you demanding 100%
certainty in this case when no analogous demand is made in any other?
This is a political ploy, not a technical argument.

>Henry points out that there are other circumstances, like space
>launchers, that could go haywire and take out a big chunk of a major
>city.  He's right.  But in those cases, we weigh the risks of disaster
>against the possible gains and decide to do it.  In this case, you are
>dealing with a weapon.  The only possible gain is that in the event of
>a missile attack, then, maybe, if it's the right kind of attack, we
>can engage the enemy and (again maybe) hit some percentage of his
>weapons.

The same argument applies to things like fire extinguishers.  (Yes, some
types of fire-extinguishing system involve significant hazards.)  A
defence system is insurance against (certain classes of) attacks; the
payoff is that if such an attack comes, you don't get hurt, or don't get
hurt as badly as you would otherwise.  If you assess the risk of an attack
as significant (deterrence is all very well, but it didn't stop Saddam
Hussein) and the consequences as costly, it is rational to accept some
degree of risk in a defence system that is likely to stop such attacks.
-- 
GCC 2.0 is to C as SVR4 is to Unix.     | Henry Spencer @ U of Toronto Zoology
                             -Dick Dunn |  henry@zoo.toronto.edu  utzoo!henry
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