Flight shooting, a form of archery, is an ancient sport with a simple objective: launching arrows as far as possible. The details are complicated. The sport involves many types of bows, each of which has specific requirements about the material composition of the associated arrows. There are also varying draw weights, the peak amount of force an archer can pull when drawing the bowstring.
James Martin has mastered flight shooting with a combination of skill, strength, and physics modeling. In September the archer and physicist at Sandia National Laboratories in Albuquerque, New Mexico, broke two world records at the annual flight archery championships at Bonneville Salt Flats in Utah. He has been collaborating in those pursuits with Alan Case, an engineer working with aerodynamics systems at Daimler Trucks North America in Portland, Oregon. Martin, who studies many-body interactions in magnetic particle suspensions at Sandia, spoke to Physics Today about his achievements and hopes for the future.
PT: How did you become interested in archery?
MARTIN: My interest started when I was five or six, and I got my first real bow when I was eight or nine. I got interested in flight shooting when I was 15 or 16, when I would mess around with my older brother in the fields of Illinois, seeing who could shoot our arrows the farthest. It wasn’t until 2010 that I started combining physics and archery by computing trajectories.
PT: Can you explain the events in which you broke the world records?
MARTIN: My main focus was the unlimited draw weight American longbow, for which arrows need to be made out of wood. I ended up shooting a flight arrow a little over 521 yards, exceeding the record of living legend Hungarian archer József Mónus, who has shot 514 yards. Using the same bow, I shot a broadhead arrow just over 382 yards, beating another of Mónus’s records of 366 yards.
PT: What principles of physics do you use to get an edge?
MARTIN: To shoot an arrow far, you have to have a good bow. Then you need an arrow that matches that bow. Roughly speaking, an arrow has three parameters: mass, shape, and stiffness. Your job is to find the arrow that has the mass, shape, and stiffness to allow that arrow to travel the farthest. We do a lot of external and internal ballistics modeling to figure out how much energy a bow will impart to any particular arrow. The energy goes up with the arrow mass and, to a certain extent, the arrow stiffness.
Once I know the launch velocity of the arrow, I focus on the optimal launch angle. If the launch velocity is much lower than the terminal velocity, then 45° is best. As the launch velocity increases, the launch angle decreases. For my flight arrow, 41° is the best angle.
For all those calculations, you need to know certain things like the drag coefficients of arrows. Alan has created some software to do modeling of those coefficients. Without knowing the drag coefficient, we can’t figure out the optimum mass. We investigate further by computing flight distances for different woods to select the best material.
PT: In your category of the competition, wooden arrows have to be fletched with feathers. What physical principles do you evaluate for those?
MARTIN: We worry about the stability of the arrow. If the fletching at the back is extremely small, the arrow will be really unstable. It’ll wag around in the air for a long time and scrub off velocity. Putting larger fletching on the arrow will stabilize it more quickly but add a lot of drag. There’s an optimum in between.
PT: Do you make the arrows that you use in competition?
MARTIN: In the categories of the competition that require wood to be used, archers make their own arrows or get them from another flight archer. Alan has made me two of his split cane bamboo flight arrows. I make all my wood arrows.
Once I’ve done all the calculations and made the arrows, I go out and test my predictions. Essentially I’m doing fieldwork and asking, Is what I think should happen actually happening?
PT: Do you think you can break your own records?
MARTIN: Alan has designed a bow for me that will be built this year and should push the records that I have right now quite a bit further. He has also created software to design and shoot bows on a computer. Bows are a little bit like violins: They all look the same, but they all sound different. Alan has designed bows that have the unique ability to transfer essentially all their energy to even a very light arrow.
I’m the first person ever to take a record away from Mónus, and he has already told me next year we will be standing side by side to compete against each other. But it is a very friendly activity, and we are open about the equipment we use. Mónus has asked to examine my arrows. I have also done calculations for other flight shooters. That’s how the sport progresses.
Having said all that, I’m not going to reveal my plans for next year’s shoot. Mónus will work all year on getting his records back. If we get Alan’s new bow made, I feel like we’re going to have a really good chance of increasing distances and holding off Mónus.