How do you aim a rocket?

Answers to your questions about the news.
July 21 2006 6:04 PM

How To Aim a Rocket

Plus, what's the difference between rockets and missiles?

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Hezbollah has fired more than 900 rockets into Israel since the outbreak of major hostilities in the region on July 12. Despite this high number of strikes, only 15 Israeli civilians have been killed. How do you aim a rocket, anyway?

With a firing table. In military terms, a "rocket" refers to an unguided, self-propelled weapon. Once the Hezbollah militants have picked a target in Israel—say, the city of Haifa—all they have to do is point the rocket in the right direction, set the firing tube at the appropriate angle off the ground, and let 'er rip. They can figure out the direction with a computer and a compass. But to get the angle, they need to check the distance to the target against published data for the particular make of rocket they're using. Then they can improve the accuracy of the attack by correcting the launch angle for temperature, altitude, and wind.

Daniel Engber Daniel Engber

Daniel Engber is a columnist for Slate

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A rocket differs from a regular mortar shell in that it contains an onboard engine, along with some fuel and an oxidizer. That means the rocket won't need outside air to propel itself—in fact, it can even work in a vacuum. The militants did fire a more sophisticated (and expensive) C-802 "cruise missile" last week. The C-802 comes with a jet engine, which uses oxygen from the atmosphere to burn its propellant. This type of engine allows it to maintain its thrust for much longer than a regular rocket.

The other distinguishing feature of the C-802 is its guidance system. After Hezbollah gunners fired the weapon, they were able to use a radar signal to direct it toward its target. That's why we call the C-802 a "missile" and not a "rocket"—you can only direct a rocket before you shoot it into the air.

The distinctions can get a bit tricky. Not all guided munitions are missiles, for example. The Israelis may be dropping laser-guided bombs, which have guidance systems but no engines. They're already moving at high speeds as they fall to the ground; the targeting computer only maneuvers their wings to steer them in the right direction.

Got a question about today's news? Ask the Explainer.

Explainer thanks John Pike of GlobalSecurity.org.

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