Tuesday, March 04, 2008

Video Del Fuego, Part III

I haven't fallen into a rut, honest I haven't, but (a) I'm convalescing from a cold, and don't care to engage in serious thinking; and (b) I just figured out how to embed videos into blog posts. Today, Video Del Fuego lives up to its name, as we honor the Saturn V.

So far as I'm aware, the Saturn V has no nickname. Gods have no nicknames. You approach them with fear and trembling, not with easy familiarity.

This is the most powerful machine ever built by human hands:

Brief science lesson: A fast stream of fluid, like a jet or rocket's exhaust, will drag the neighboring air along with it. So, during a launch, you'll see a very brief puff of smoke at the rocket's base, then see that puff sucked back down into the exhaust channel as the thrust builds up.

Another curious thing you'll see is that the plume coming right out of the nozzle isn't as bright as the flow just downstream. There are two reasons for this. One, the nozzle itself is cooled by a flow of liquid oxygen, so the flow right next to the wall is much cooler than it would be ordinarily. Second, the fuel-oxidizer mixture has not completely burnt up yet. There's just not enough time between the thrust chamber and the end of the nozzle. It's mostly burnt, but not completely.

Musical note: This sequence was set to "Mars, the Bringer of War" from Gustav Holst's suite "The Planets". It's an appropriate piece. The business end of an F-1 engine running full-bore isn't a very friendly place to be.

Bonus double feature: the liftoff of Apollo 8.

This is about the best launch sequence I've seen from this era. You see all the important bits, all the way up through staging. Two things to look for: first, as the vehicle climbs up into the high, thin air of the upper atmosphere, the exaust plume expands. It was designed to match pressures at sea level. But as it gets higher, it's working against thinner air, and the plume expands until it reaches equilibrium. Second, when the second stage lights off, you don't see an exhaust plume. Its J-2 engines burn liquid hydrogen and liquid oxygen, producing a clear flame. There's exhaust, we just can't see it.

In many ways, this was our finest hour: we built the most powerful machines ever so that we could go somewhere we'd never been, and learn something new we didn't know before.

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