# Balls in Orbit Trajectory Today

When I was growing up, trajectory was a word we usually heard Walter Cronkite applying to an Apollo spacecraft.

The lunar modules trajectory will carry it over the moons massive Sea of Tranquility, the most trusted man in America would intone, tranquilly yet authoritatively, and we would imagine the module, tinted gold by the sun, in a grand parabola of flight over the lunar grayness.

And thats the way it is. Or was. Nowadays, trajectory brings to my mind (and many others) the flight of something we all want to put into orbit: a golf ball.

What influences the vertical shape of the flight of a golf ball? Beyond raw distance, we all want to see a balls flight line take a certain shape, so it will roll out on drives and land obediently on iron shots. Of course, the clubhead matters. The shape, size, loft, resistance to twisting ' these all play a part that most of us know pretty well. But what about the other participants in this 500 microsecond physics experiment?

Lets begin with the pellet.

The overall construction of a golf ball usually impacts the initial launch, says Dean Snell, chief golf ball engineer at TaylorMade-adidas Golf. Softer compression balls will have a tendency to fly [at a] lower [angle] off the face. The trajectory is then determined a few key factors: first, the ball speed. The second is how much spin the ball has. Lower spin will not lift or carry higher, and higher spin will have a tendency to carry up higher.

So were in the familiar zone of each persons unique swing characteristics. Naturally, your particular launch habits, including how much spin you put on the ball, will help decide how your ball flies. But tell us more about the features on the ball itself. Those holes and bumps aint decoration.

The dimple shapes, depths and edge angles can control the trajectory all by themselves, Snell says. If you launch the two balls at the exact same spin, speed and launch, and have shallow dimples on one, and deep dimples on the other, they will have two completely different flights. The shallow dimples will fly much higher and not roll as much, while the deeper dimples fly much lower and will roll out more with shorter carry.

So, there are three influencers here, as Snell sees it.

Construction controls initial launch (and also helps control some of the spin), the player controls ball speed and spin, and the dimples and spin control the flight in the air.

Great. Now, if your game requires a change, the ball might be a good place to start. But do you run straight for the store? It might be a good idea to take a more measured approach.

For most consumers, todays balls all have very similar spin, so they dont have to worry about that anymore, Snell says. If they are looking for balls that launch higher, then the higher compression or firmer balls will help them do that. But if they truly want to be the best launch for their specific swing, then should get fit on a system to try to optimize trajectory that includes carry and roll. Getting your launch angle to 12-14 degrees and getting your spin to 2500-3000 rpm will help you achieve best carry and roll.

Fitting is more expensive than a new dozen, but is more likely to offer lasting results. But the analysis has just begun. What about shafts?

The flex profile of a shaft has the most profound effect on trajectory, says John Oldenburg, chief design engineer at shaft company Aldila. For a large majority of golfers, shafts with softer tips will give a higher launch with an increase in spin. The shaft effects trajectory by changing the actual loft (dynamic loft) of the head at the moment of impact. Softer tip shafts allow for a greater change in dynamic loft due to shaft bending being more concentrated in the lower end of the shaft closer to the head. Torque also can have an effect on trajectory and spin by its effect on face angle at impact.

So if a fitting tells you ' or you have the time, dollars and willingness to experiment ' could a new shaft be the ticket?

Yes, changing a shaft can definitely change trajectory, Oldenburg says. The player needs to remember that optimal launch conditions vary with relation to their ball speed. Higher ball speeds need a lower launch angle and lower spin to optimize performance. Slower ball speeds require a higher launch with more spin. So, when a player is seeking a trajectory change they need to make sure they choose a product that gives them an optimal combination of ball speed, launch angle, and spin rate. Sacrificing one of these three parameters to change one of the other two can have an adverse effect on performance.
So whats the intelligent way to go about making a change?

A good way for the consumer to choose is to determine the characteristics of their current shafts, most importantly tip stiffness. Oldenburg says. And then, to get accurate information on the shafts they are considering so they can make a valid comparison. If the consumer is looking increase the launch angle, they should shop for a product with a softer tip than they currently use, and vice versa. This information is typically available from professional clubmakers, and from shaft manufacturers websites, or by contacting the customer service department at the shaft manufacturer directly.

The absolute best way to tell how a shaft performs for your particular swing is to demo a product before buying, because no two golf swings are the same, so no one shaft will perform equally for any two players.

Viewed from one angle, trajectory is the result of a three-part machine (the golf club, with its head, shaft and grip) operating on a two-to-four-part machine (depending on the number of layers in the golf ball you choose). So its no surprise that the equation is complex. But as far as your game is concerned, it could be very rewarding to do the math ' especially with some of the equipment innovations coming over the development horizon.

Trajectory management is really finding the combination of clubhead, shaft, and golf ball that optimize the launch conditions for your particular swing, Oldenburg says. All three of those components can have profound effects on performance, and they must be looked at in combination with each other, not as separate entities.

The future of trajectory management might well be found in the new ruling from the USGA on interchangeability of golf clubs. This will enable the player to obtain several heads and shafts that they can combine in a wide array of combinations to fit their swing and performance needs. Players swings and the conditions they play in constantly change, so having the ability to change your shaft/head/ball combination on any given day will really allow a player to manage their trajectory on a day-by-day, round-by-round basis.

And thats the way it is in the modern game.