NBC NEWS- The Navy is getting ready to blow a dying spy satellite out of the sky, perhaps as early as Wednesday evening if weather permits.

The Pentagon says it has three specially modified missiles and a ten day window to demolish the space debris.

The Navy is aiming to fire a modified missile like a ballistic sledgehammer to smash the disabled spy satellite into harmless pieces before it can plunge to earth.

NBC News Space Consultant James Oberg said, "It's unlike any collision any of us have ever imagined here on earth."

"There's no pushing one aside, swerving, knocking it off course. It's total destruction," said Oberg.

The highly classified satellite known as USA193 went into a virtual coma shortly after it was launched in 2006.

It's due to plummet earthward next month, much like Skylab did back in 1979.

The Pentagon says USA193 is as big as a bus and is carrying a half-ton of toxic fuel called hydrazine, which can cause severe illness and can even be fatal depending on the intensity at contact.

Pentagon Director for Strategic Plans and Policy, Lieutenant General John Sattler said earlier this week, “I believe we have the responsibility to mitigate the risk to the rest of the world."

Some experts say this is more about protecting military secrets.

John Pike of GlobalSecurity.org said, "If they did not do this intercept half the satellite would survive re-entry. Some of those pieces might be big pieces and the Chinese and the Russians might learn something about our technology."

Some nations complained this is just a U.S. excuse to test its missile defenses.

The USS Lake Erie and another ship are waiting off the Hawaiian coast with three specially modified missiles.

They've got a week and a half to complete a tough shot.

"This is a missile designed for shooting down other missiles, slower, and lower targets. This time it's higher, colder, so less visible to the infrared sensor, and moving much faster," said Oberg.

The government won't say how much it spent on this dud satellite, but the missiles being used to destroy it cost $10 million a piece.