We had attached to the lunar module a 60,000 pound dead mass, the command service module. Now the lunar module maneuvers around by itself because the little attitude thrusters fire through the center of gravity. That's why when you push it one way, it goes that way. But now the center of gravity is not in the center of the lunar module, it's out to the command service module someplace. Therefore when I first started to maneuver, I didn't realize this, and I wanted to go left, it went to some other place.

Why the hell are we maneuvering at all now? Are we still bent? Well we're at home for once, I mean we're at the river pole. No, I mean why can't you know I'm out somewhere? Every time I try to, I can't take that dog on roll-ups. When

I go right, I want to go up, go on again. What's going on here? Then at dawn, now that we had this command service module, I literally had to learn how to maneuver all over again.

That's what you need to play with. Okay, we'll try that. Let me get around though, let's roll, let me get a little roll all the way. You can't let it roll all the way. I know, I know. But I mean, I'll

get into it. Compared to the slick, a neatly finished command module with its three couches and room enough for the whole crew, the lunar module seemed comparatively cramped and basic. With Swigert, it was a new and unnerving experience. Remarkably, Jack

had never been in the lunar module. A real one, I mean in flight. Or certainly not in flight obviously, but out on the ground. I mean he had never been in the lunar module. He was the command module expert. So, what concerned him was the limb in comparison, has no inner walls, netting material. Just sort of keeps you from bumping in the wiring bundles and plumbing. And it's noisy, comparatively speaking, to the command module which is building a battleship to survive entry and launch. And I think that for whatever reason the glycol cooling system made occasional gurgles. And the pump ran at different frequencies. It was kind of wind. And he never heard that before. And when questioned he asked, do you think this thing will make it?

With the lunar module's life support systems powered up, attention now turns to focus on how to get back to Earth. Apollo 13 is currently still on a course designed to get them to the surface of the Moon and its current trajectory won't get them back home. If they do nothing, they'll eventually swing past the Moon but then miss the Earth by thousands of miles. They have to take action. They could choose to turn around and come back directly, reversing their path before they reach the Moon. But that option, the direct return, would need the powerful thrust of the command and service modules main engine and that is plagued with problems. For such a drastic maneuver they would have to burn the engine until its fuel was almost exhausted, leaving them little opportunity to correct their trajectory later if needed. But still, no one can be sure that the main engine on the service module hasn't been damaged by the explosion, which happened in the same section of the spacecraft. The only other option then is to continue forward but make a small course correction exploiting a path that would take them round the Moon and right back to Earth. This would require very little thrust, using gravity to get them home like a skateboarder turning round at the top of a steep ramp. But that isn't without challenges. For a start, that would take much longer to get back to Earth, threatening their precious supply of consumables, things like oxygen, water, food and electrical power. And if they're to do it, they have to make that course correction urgently, firing the lunar modules to send tension briefly but precisely to put them on this so-called free return trajectory. Bight Dynamics Officer Jerry

Bostik was responsible for that decision. That was kind of a given. There were no other options. And the main thing was to get to a free return trajectory.

You know, let's bring this thing headed back to the Earth. At that point, we thought that we could do that maneuver without a problem but you've just had a big explosion and you don't know what caused it. Where there are other

problems.

Poppy Northcutt, retro support on Apollo 13. You

had people all over the world working on trying to solve that problem.

We powered up the limit about 10.50 in the evening on April

13th. This is George Kalen, a software engineer from MIT, the contractor which designed and built the Apollo spacecraft's guidance and navigation system. During Apollo 13, Kalen is working with NASA in Houston, providing expertise on the computer's control of the critical engine

burn. The burn was scheduled for about 230 to 245 on Tuesday, April 14th in the morning, which is only about three and a half hours away. We did it in time and yes, we developed the test procedures and tested them and got them up to the astronauts in time for the

burn.