Sunday, October 04, 2009

Apollo +50: Little Joe 6

I am writing this series about the start of the manned space program because it is an excellent example of how to use a system of experimentation, searching for a natural explanation for the results of one's experiements, and making modifications. It is also an excellent example of what can be accomplished and how quickly it can be accomplished if one uses this system.

50 years ago today, engineers and others working on the manned Mercury program could not have possibly known that, in less than 9 years and 10 months, the United States would land astronauts on the moon.

In fact, 50 years ago today, nobody had yet flown in space. They had hoped, "maybe next year."

They were wrong, as it turned out. Humans would not fly in space for another 18 months.

NASA was finding out how difficult this task of sending people into space really was. On August 21st, it tried to test the Mercury capsule by launching one on top of a new rocket called the Little Joe. Thirty minutes before the scheduled launch, the emergency escape tower unexpectedly fired, ripped the capsule off of the Little Joe rocket, and spashed it into the ocean a few miles off shore.

Little Joe did not even launch.

Because of this failure, NASA decided it needed to take a step back and go a little bit slower. The first thing it needed to do was to find out if this Little Joe configuration would work. It was not a simple rocket. It was, in fact, a gaggle of cheap rockets all strapped together - all of which had to work.

The reason that this launch was called Little Joe 6 is because NASA had made a roadmap for its Little Joe rockets. It had designed five launches for five different tests named Little Joe 1 through 5. When it decided that it just wanted to test the Little Joe rocket itself, NASA gave it the next available number - Little Joe 6 - even though this was destined to be only the second attempted launch (and the first actual launch) of a Little Joe rocket.

NASA wanted to know what would happen to a capsule at max-Q. To test this, they did not need a rocket that would launch a capsule as high or as fast as the Redstone or Atlas rockets. They simply needed a rocket that could reach max-Q - and one that could do so without costing as much as a Mercury capsule cost.

What is max-Q?

Well, as a rocket rises, it goes faster and faster through the air. However, the air gets thinner and thinner. There is a point, called max-Q, where this combination of air density and speed put the maximum amount of stress on a spacecraft.

On one side of the launch, you have the capsule sitting on top of a rocket on the ground. The atmospheric dynamic pressure on the capsule sitting on top of the rocket is the same as the atmospheric dynamic pressure on the people working on the rocket. It's not creating that much stress.

On the other side of the launch, the spacecraft is moving at over 17.500 miles per hour. However, it is moving through the vaccum of space. So, there is no atmospheric dynamic pressure. Heck, there's no atmosphere.

Somewhere in between the capsule experiences its maximum atmospheric dynamic pressure.

This actually happens fairly close to the ground - approximately 7 to 9 miles in altitude, depending on the specific rocket.

With the Little Joe launch, NASA simply needed the rocket to reach the equivalent to what max-Q would be on the Mercury manned flights. After that, everything that happened to the rocket was because of inertia, in both the physical and the metaphorical sense. A rocket that reached max-Q still had fuel to burn. Even when it ran out of fuel, inertia would still carry it up a bit higher. This is why the Little Joe 6 test reached a height of 37 miles.

What it proved was that it could do the work it needed to do at an altitude of 7 to 9 miles.

As a result of this test, NASA knew that it had a test platform for testing the Mercury spacecraft under max-Q. The next thing it needed to do was to actually test the Mercury spacecraft under max-Q.

1 comment:

Luke said...

Did you finish your series on The Purpose of Life?