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Wow, this is so neat. This must be an electronic classroom.

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It certainly is. I'm Bob Starr. Have a seat.

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We heard you could hook us up with any NASA researcher.

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Yes, I can. In the electronic classroom, we use two-way audio-video communications over the phone lines.

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I've been doing a little research, and I found that NASA's Dryden Flight Research Center in California

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uses experimental planes to test out new futuristic ways of flight.

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It tested NASA's first space shuttle before it went into space.

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That sounds risky, too. That must be where they find out if the new designs are going to really work.

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Hey, I know a researcher who's an expert in stability. His name is Al Bowers. Let me try to contact him.

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Hi, I'm Al Bowers, an aerospace engineer at NASA's Dryden Flight Research Center.

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I understand you have some questions about airplanes.

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We have a lot of them. Could you tell us about weight, one of the four forces, and how it affects flight?

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One way that weight affects an airplane is the way the weight is distributed.

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The weight is distributed on an airplane so that there's a balance point,

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and that balance point is called the center of gravity.

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How does the center of gravity help you design planes?

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I'm glad you asked, because we use the center of gravity to determine where to place the wings on an airplane.

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On a normal airplane, like this one, we place the wings just behind the center of gravity,

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and that helps to keep the front end of the airplane pointed forwards.

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Our plane always flies to the right. Is there anything we can do to fix this problem?

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That's the purpose of the tail.

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The tail of the airplane keeps the nose from going up too high or dropping too low or slicing off to the left or right.

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Here, let me show you.

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This is an F-104 Starfighter aircraft.

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It has the center of gravity just in front of the wings where the lift is produced,

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and the tail is on the back end of the airplane.

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All of that makes this a very stable aircraft.

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Wow, what kind of plane is that next to you? I've never seen anything like that before.

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Oh, this is the X-29.

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I'm sure you noticed right away that the wings are on backwards,

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and that we put the tail on the front of the airplane.

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Backwards? And a tail on the front?

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Yes, even backwards we can make it work with the tail on the front of the airplane,

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just like on Burt Rutan's airplane.

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How can it fly like that?

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Let me show you with this broomstick.

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This broomstick is like a traditional airplane where the center of gravity is in front of the wings, and it's stable.

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If we move it to a new position, the broomstick just follows along.

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But the X-29 was unstable.

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The center of gravity was behind the wings, and so it was like your egg crate airplane.

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And it didn't fly very well.

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But on the X-29, we had advanced technology in the form of very fast computers.

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Those computers could compensate for the instabilities in the airplane.

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Let's go back to the broomstick for a second.

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It's like your hand moving back and forth to compensate for the instability.

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And that was the way we were able to make the X-29 fly.

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Wow, I never thought a plane like that would have been able to fly.

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I guess we need to find our center of gravity and make sure it's in front of our lift.

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Yeah, that'll make our plane more stable.

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Thanks for all your help, Mr. Bowers. Bye.