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Let's visit NASA's Stennis Space Center in Mississippi.

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There, NASA scientists are testing engines to make the X-33 more efficient.

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The difference between the linear aerospike engine and conventional engines is the shape of the nozzle.

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Conventional engines have a nozzle that's shaped like a bell,

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and the hot combusted gases expand along the inner surface of this bell.

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However, with the aerospike engine, the nozzle is in the shape of a V called a ramp,

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and the hot combusted gases expand along this outer surface.

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This unusual design allows for a more efficient performance from the engine

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and a more optimal vehicle design.

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Once all the information is gathered from the various tests, it comes time to put the data to use.

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Music

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How do engineers use their models to test their ideas?

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What can you learn from a scale model?

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Jennifer and Ben, welcome to the Skunk Works in Palmdale, California.

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This is the location where we build the X-33 vehicle.

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You can see some of the parts of the X-33 behind me.

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That's the vertical stabilizer.

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Those parts are mounted in the back of the vehicle to keep it steady during its flight.

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And you can see it mounted here on this scale model.

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This model is used to evaluate the aerodynamics performance in a wind tunnel.

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So it is built in exact proportions to the actual vehicle.

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Now, the vehicle is under construction right here.

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This is the X-33.

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And it is also a proportionate vehicle.

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It is proportional to a much larger vehicle called Venture Star.

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Now, we've learned a lot from proportioning this vehicle.

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We've already changed the design of Venture Star based on what we've learned in the proportioning exercise on X-33.