New York Times on the Web Forums Science
Russian military leaders have expressed concern about US plans
for a national missile defense system. Will defense technology be
limited by possibilities for a strategic imbalance? Is this just SDI
all over again?
(1737 previous messages)
- 07:59pm Mar 29, 2001 EST (#1738
The 20cm is an estimate based on light relay times, as you
I did it from memory, but I think that's about right
...if a designer included (relatively cheap) auxilary rockets
designed purely to fire randomly in half-second intervals.
Although the angle of deflection of the missile's path will be
minuscle, we can resolve the sideways and forward components of
the rockets motion independently. If a 7000kg rocket had a
1400N rocket thrust applied for 0.1 seconds,...
I think this is the simplist way to look at it. Light goes
3x10**8 m/s. At 100 km. light takes less than 1/1,000,000 of a
second to make the round trip.
Think about it intuitively. How much can you make anything heavy
move in 1/1,000,000 of a second from a standing start? A Saturn V
couldn't do it.
At shorter distances (1km, etc.), it would be easily
We just sold Israel some that will shoot down an old Katuska
rocket at 10 km. It's been in the news. Jerusalem Post for one. I
suppose I'm gonna have to look it up.
Visible, 95% ...UV or greater...IR
Well, there is of course x-rays which you left out which we use
no to see through the clouds.
To start with we would have to use something higher than radio
since it can't be focused smaller than it's wavelength. And there
are often special frequencies, such as the very narrow band of
blue-green light that is the only electromagnetic stuff that will
penetrate seawater. (Other than VLF).
And, what is the effect on the atmosphere of such a large energy
density? Does the air get more or less opaque? What about
modulation? Is the effect the same for a continuous burst as it is
for pulses of some modulation? Lots of things for an engineer to
sink her teeth into.
But x-rays? No problem.
And an important point needs to be made. Knocking one down at 50
km is better than nothing. Good chance the little toad in N. Korea
won't know precisely the effective range. Would have to make a
- 08:03pm Mar 29, 2001 EST (#1739
If the planes can already deal with very high temperatures over
extended periods on much of their contact faces, why would a laser
(with the slight inevitable correction errors) be able to do
significant damage? If the wings have a 4mm protective layer from
the heat now, why not double that to protect against lasers?
The space shuttle, heading back into earth orbit, endures ten of
thousand of degrees C - couldn't the same (admittedly expensive!)
materials be used to cover an ICBM?
- 08:06pm Mar 29, 2001 EST (#1740
- 08:09pm Mar 29, 2001 EST (#1741
rshowalter - 07:26pm Mar 29, 2001 EST (#1729 of 1738)
Robert Showalter firstname.lastname@example.org
Recall that the accelleration from the earth is 1 g -- .01 g,
perpendicular to path, for a short time, throws things out A
We have been able to predict the path of the ICBM since Kepler.
We have known why (the .1g part) since Newton.
--- HOW MANY DATA POINTS IS THE RADAR TAKING ON EACH
If gravity is the only force acting on the warhead, and we got a
velocity doppler reflection, two or three. Otherwise more.
But all this assumes that we are going to shoot some time after
we get the information from the data points. Two, or even one will
do if we shoot fast.
- 08:09pm Mar 29, 2001 EST (#1742
George Johnson -- I'm just about sure it is you -- you don't know
any mathematics. You don't have any engineering background. You're a
superb writer, but we're dealing with an issue that can be tested
and right answers should be morally forcing.
- 08:12pm Mar 29, 2001 EST (#1743
rshowalter - 07:40pm Mar 29, 2001 EST (#1734 of 1741)
dirac - on the top of the wing, pressures are lower by a few
percent -- it is nothing like a vacuum.
I never said it was a vacuum. I said that the kinetic energy of
the air above was not slight as stated. That it moved fast. I did
say something about the missle would hopefully be out of the
atmosphere. Perhaps that is the misunderstanding.
- 08:13pm Mar 29, 2001 EST (#1744
I'm sorry to correct you, but 100km is 10^5m, therefore it takes
10^5/(3*10^8) seconds to travel the distance.
This is 0.33*10^-3 seconds, or 33ms. The round trip takes 66ms
Your suggested time of 1/(1000000) second is 1 microsecond. 66ms
is 66,000 times longer.
I agree with the X-rays, but they pass through thin sheet metal -
the heating would not just occur at the surface and so would be more
defuse than visible which has very low penetration. You'd have to up
the power, correspondingly, as you'd be heating a large amount of
metal at once.
You could of course, sterilise a pilot, but that's just being
- 08:13pm Mar 29, 2001 EST (#1745
New York Times on the Web Forums Science
Enter your response, then click the POST MY MESSAGE
See the quick-edit
help for more information.