Sea of Shadows eBook - Navy Thriller.com

310 JEFF EDWARDS
The chief shook her head. “It is, sir. But this water is too shallow even
for the modified ASROCs. They’ll end up buried in the sea bottom.”
“Is there any way to reprogram the ASROCs?” the XO asked.
“I wish we could, sir,” Chief McPherson said. “But it’s not a software
issue. It’s a physics problem. We call it dynamic overshoot. An ASROC
missile drops its torpedo from an altitude of about ten thousand feet. Even
with the parachute pack to slow it down, when it hits the water, an
ASROC-launched torpedo is moving fast. The saltwater batteries start the
motor up almost immediately after the weapon splashes down, but the
torpedo is still sinking fast. The computer takes control of the rudder fins
and elevator fins and starts leveling off the torpedo as quickly as it can—
sort of like a pilot trying to pull an airplane out of a steep dive. If the
water is deep enough, the torpedo levels itself off and goes into its search
pattern. If the water is too shallow, the weapon slams into the sea bottom
before it can level off. Maybe the bottom is soft mud, and it buries itself.
Maybe the bottom is hard-packed sand, and the torpedo is demolished by
the impact. Either way, the torpedo is history.”
The XO scratched his chin. “And this water is definitely too shallow?”
“Yes, sir,” the chief said. “An ASROC torpedo will hit the water, run
its motor for maybe ten seconds, and then crash into the bottom. It’ll make
a bunch of noise, but it won’t do anything useful.”
The XO’s eyebrows went up. “If the water is so shallow, what’s going
to keep our tube-launched torpedoes from hitting the bottom? Or any
torpedo dropped by the helo?”
Chief McPherson held up two fingers. “Two things, sir. First: overthe-side
torpedoes and helo-dropped torpedoes hit the water with only a
slight nose-down angle, so they’re much closer to being level when the
motor starts up. And second: they don’t fall as far, so they don’t build up
much inertia. Our torpedo tubes are only about twenty feet above the
water. The helo drops its torpedoes from an altitude of only a few hundred
feet, not ten thousand feet like an ASROC. They’re not moving all that
fast when they hit the water, so they don’t sink very far before they can
level off.”
“I see,” the captain said. “And there’s no way to program the ASROCs
to drop their torpedoes from a lower altitude? Or maybe program the
ASROC torpedoes to strike the water at a shallower angle?”
“Sir, it would take a complete redesign of the ASROC missile,” Chief
McPherson said. “A team of engineers with a billion-dollar budget could
probably figure out how to do it if they had a couple of years to play
around with the idea. But there’s nothing we can do here and now.”
“So we’re stuck with over-the-side torpedoes,” the XO said.