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How can you improve the performance of a bicycle?

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Explain two forces that affect both X-33s and a bike's performance, and could you tell

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us how they relate to each other?

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Okay, so we've collected the baseline information from Van's one-mile test run, and I think

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we can all agree that some improvements need to be made.

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Now, obviously, we can't change the size of the bike, but, I mean, can't we improve some

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of the bike's technologies or something?

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Yeah, make it lighter so it's easier to pedal, maybe.

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Right.

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You can decrease the force that will take the pedal by decreasing the weight of the

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bike.

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One way that you can do it is to replace the frame with one that is made of a new, lighter,

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stronger composite material instead of this heavy steel.

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That's something we have to do with the X-33.

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We already learned from our subscale testing that both for the X-33 and the larger Venture

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Star, we're going to need to use composite materials in order for both of them to reach

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space.

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You know, it seems to me that part of Van's struggle was the bike's poor aerodynamics.

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That's another common challenge the X-33 and your bike share, moving through the air easily

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and with less resistance.

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A lot of this has to do with the geometry, so the shape of the vehicle is critical.

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The X-33 has a wedge-shaped design.

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I suggest you look for ways to make the bike more aerodynamic, otherwise you're just fighting

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the force of drag.

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Drag is simply the resistance of an object caused by the air, in this case, through which

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it is moving.

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Yeah.

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Since X-33 is a flying machine, we also need to generate lift.

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That's the force that supports objects as they move through the air.

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Well, you can't test that with a test run like mine.

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No, but we can simulate it on a computer, or we can run small-scale models in the wind

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tunnel.

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Oh.

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So we can make the bike less resistant to air and gravity, but what else can we do?

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One thing you can do is you can make the power source more efficient.

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Now on the bike, you're the engine.

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Are you sure you're using the gears correctly?

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No, I don't even know how they work.

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I normally just keep it in third.

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Well, you know what?

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Let me show you how they work.

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It's really easy, and it'll make you a lot more efficient.

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Well, Van, those gears are there for a reason.

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See, when you are riding or racing bikes, you want to use your energy as efficiently

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as possible.

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To do this, you need to use your gears correctly.

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They will help you pedal at the same rate throughout the race and help conserve your

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energy.

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For instance, when biking uphill, use a low gear, and when biking downhill or on a flat

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road, use a higher gear.

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Like the gears on your bike, the X-33 will also make the most efficient use of the environment

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by using two revolutionary linear aerospike engines.

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That's so cool.

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Hey, let's head to Cookville, Tennessee.

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There, we're going to meet some students who are making their own models of the X-33.