Re: Missile vs. Satellite: Go Navy!

On Feb 20, 12:53 pm, j...@xxxxxxxxx (John Dallman) wrote:
In article <47bc6645.1334...@xxxxxxxxxxxxxxxx>, eugene@xxxxxxxxxxxxxxx

(Eugene Griessel) wrote:
j...@xxxxxxxxx (John Dallman) wrote:
They get further shots, but not on the same pass. That satellite is
coming over /fast/, much faster than the missile's top speed. The
situation is like trying to hit an artillery shell with a Sea Wolf,
not

I would posit that your analogy is a tad flawed. Unless you can show
me an artillery shell capable of doing 7750 m/sec!

It is not exact. But we have a dumb target coming much faster than a
smart interceptor, in both cases. I was trying to draw the contrast with
the CIWS vs Harpoon situation, where the interceptors are faster than
the target.

Basically the missile has to be there when the satellite arrives. No
real room for error.

Yup!

--
John Dallman, j...@xxxxxxxxx, HTML mail is treated as probable spam.

I would say the kinetics require the missile and satellite to be on
opposite tracks and collide "head on" so the missile weight is
augmented by the closing speed.

I would estimate the SM-3 warhead at something between 400-800 pounds,
the USA 193 is "guestimated" at 5,000 pounds. The 193 is at orbital
velocity, 7-8 kilometers per second , the SM-3 at perhaps 3-4 kps.


Inside America's Satellite-Killing Missile
By Noah Shachtman EmailFebruary 15, 2008 | 12:05:39 PMCategories:
Missiles, Space

Sm3_diagram_2 The weapon that the Pentagon wants to use to shoot down
a failing satellite is well-tested. But its one weakness could pose a
problem, as the military tries to take out that satellite before it
hits the atmosphere. Center for Defense Information missile
specialist Victoria Samson explains...

Today, the U.S. Aegis Ballistic Missile Defense system uses the
Standard Missile (SM)-3 to make what are known as "direct
intercepts." That means there's no explosion in space. Instead, the
SM-3 destroys its target by ramming into with lots and lots of sheer
kinetic energy -- more than 130 megajoules worth, or "the equivalent
of a 10 ton truck traveling at 600 miles per hour," it maker says.
The missile uses two stages to get into near-space, and a third,
kinetic warhead to strike. The interceptor finds its targets largely
because its seeker has been programmed to look for a certain type of
object. (The SM-3 Block1B, the upgrade to the current model, is
supposed to have a two-color infrared seeker which presumably would
increase its discrimination capabilities.)

Right now, the SM-3 has tested against short- and medium-range
ballistic missiles, and has made twelve intercepts out of fourteen
attempts during testing. These intercepts have been made while the
target is in space (tests have been at altitudes of over 100 miles),
which provides it with a hot target against the cold environs of
space. The most recent flight test intercept attempt by a U.S. ship
occurred on Nov.6, 2007 and was a success.

Raytheon, which makes the interceptor, explains how it's supposed to
work:



As a ballistic missile threat rises above the horizon, [the]
ship's radar acquires, begins tracking, and the weapon system begins
calculating the engagement solution. Upon command from the ship's
weapon system, the SM-3 boosts out of the launcher and establishes
radio communication with the ship. After MK 72 booster burnout, the MK
104 Dual Thrust Rocket Motor (DTRM) ignites. In-flight communications
from the ship guide the missile toward the predicted intercept point.
After MK 104 burnout and separation, the MK 136 Third Stage Rocket
Motor (TSRM) ignites, propelling the third stage out of the
atmosphere. Throughout its flight, the missile continues to receive in-
flight target updates from the ship to refine the intercept guidance
solution. The TSRM contains two separate pulses that can be initiated
to optimize the engagement timeline. During flyout, the third stage
pitches over and ejects the nosecone, exposing the SM-3 Kinetic
Warhead (KW). Following TSRM burnout roughly 30 seconds before
intercept, the SM-3 KW separates from the third stage and immediately
searches for the target based on pointing data received from the ship.
The KW acquires the ballistic missile warhead with its long-wavelength
imaging infrared seeker. The KW's Solid Divert and Attitude Control
System precisely maneuvers the KW to enable a hit-to-kill intercept.
As the KW closes on the target, it will identify the lethal payload
area and shift its guidance aimpoint to ensure a lethal hit,
destroying the target with more than 130 megajoules of kinetic energy,
or the equivalent of a 10 ton truck traveling at 600 miles per hour.

But things have gone wrong. The primary cause of one of the few U.S.
flight test failures is the new guidance control system, the Divert
and Attitude Control System, whose ceramic components cracked during a
test. This problem has not been remedied and is not being used in its
most advanced mode. Which means that the SM-3's maneuverability
against more demanding targets may be affected. Given how all of the
tests so far have dealt with targets that we knew down to the smallest
detail how they would behave in-flight, this means that it has not
been tested against unknown targets that may require last-minute
changes in its trajectory.

The Pentagon has, as of the end of 2007, 21 SM-3 interceptors. It's
not like they have a huge inventory to draw upon. For this proposed
shoot-down, the Pentagon is claiming that it will make modifications
to three SM-3 interceptors so that they can look for the
malfunctioning satellite. The modifications involve changing the
software to target a satellite rather than a missile, David Wright of
the Union of Concerned Scientists tells New Scientist. "This
interceptor is really intended for missiles traveling at 3 to 4
kilometers per second; the satellite they're going to be shooting at
has a speed of 7 to 8 kilometers per second."

But the change draws attention to one of the program's biggest flaws:
if it doesn't know what to look for, it is unlikely to make an
intercept (situational awareness is pretty slim). And since the tests
to date have all been highly scripted, the system has not had any
practice of on the fly (if you'll excuse the phrase) intercept
attempts.

-- Victoria Samson

http://blog.wired.com/defense/2008/02/the-weapon-that.html
.

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