In missions to other planets, it was learned that there will always be errors.
In the first U.S. planetary mission, which went to Venus, scientists and engineers argued whether a tank of propellant and a rocket engine would be needed for a midcourse correction maneuver. At first it was believed that we could launch the Mariner spacecraft directly at Venus and that the craft would coast all the way to the planet without significant error.
It was like shooting an arrow at a target. Once the arrow leaves the bow you have no control over where it lands. The only control you have is the direction you point it in.
Some engineers calculated the effect of the pointing error of the launch vehicle (and other effects such as the very small force of solar radiation on the spacecraft) and discovered that the Mariner spacecraft could easily miss Venus by a million miles. But to perform the scientific observations, the craft had to be within 20,000 miles of the cloud-enshrouded planet. Putting an extra propulsion system on a spacecraft increases the weight and complexity—which increases the cost significantly. Up to this point, rocket scientists had not conceived the idea of a trajectory correction maneuver (or TCM). Eventually, the engineers convinced project managers that a midcourse correction maneuver (and the requisite propulsion system) was absolutely necessary if the Mariner spacecraft were to get to Venus.
Nowadays, TCMs are old hat. You wouldn't begin to think of designing an interplanetary mission without incorporating a series of trajectory correction maneuvers to bring the spacecraft back on course. We often hear of the extraordinary accuracy of space shots. "It was like hitting a dime in New York with a rifle in Los Angeles." These analogies are not entirely true. A better analogy was given by my friend Bob Cesarone, who was for all practical purposes the remote pilot of the Voyager spacecraft that went to Neptune. The way Bob put it, "It's not like hitting a hole in one. It's more like a series of precise, short putts on a golf course. Each putt gets you closer to the target."
So rocket scientists are not perfect and neither are their spacecraft. Errors are expected and accounted for. Small mistakes will always be present.
By knowing you live in a world of errors, you can plan to take corrective action. Don't be afraid to make trajectory corrections in your life. If you expect they will be necessary, then making a correction will not be an admission of failure but a reflection of wisdom and foresight.
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