Free-Return

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March 12, 2003

Why Free-Return?

Several years ago, I had the pleasure of sharing a road trip of appearances with Jim Lovell, the astronaut who piloted Apollo 13. Over several weeks, I got to hear Jim repeat time and again his chilling tale about the troubled Apollo 13 mission.

One point stood out.

Jim explains to non-science types like me that there is a natural "free-return course" that one can draw around the Earth and the Moon. It's this free-return course that gives a spacecraft the benefit of the Earth's pull once it circles the moon. Kind of like staying within the bounds of a space highway with momentum in your favor.

As it turns out, during the trouble-free part of the Apollo 13 flight, Mission Control decided to take Apollo 13 off its free-return course. As I recall, the reason was to put Apollo 13 on a course that would bring it closer to the Moon for the benefit of photo opportunities.

Jim tells the story that shortly after he made the manuever, all Hell broke loose on the spacecraft. It wasn't until sometime after, as everyone at Mission Control and on the spacecraft were crazed trying to figure out what to do next, that it hit Jim. Mission Control had taken him off the free-return course. Suddenly the slingshot manuever around the Moon and back to Earth wasn't workable. Momentum was no longer in his favor. Apollo 13 could very well be buzzing off into the far reaches of space. Forever.

The folks on the ground realized it some time later.

No doubt you may remember the scene from the movie when Jim gets just one chance, with his last boost of power, to put Apollo 13 back on track. Back on its free-return course.

Ever since Jim told that story, I think of the elegance of free-return. A few degree change in anything can make all the difference. Set out to do most anything and it's good to have thought through a "free-return".

In business and life in general, things happen. Gravity is unforgiving. Timing a "burst" that can get you back to free-return can make the difference.

It sure did for Lovell and crew.
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And of course if you find yourself less than satisfied with my oversimplification of Free Return, you can always visit places like http://web.mit.edu/12.000/www/finalpresentation/traj/free.html

Posted by at March 12, 2003 10:29 AM

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