This Electromagnetic Model Aircraft Launcher Is a Perfect Example of Iterative Design

The runways at international airports often need to be more than two miles long to provide enough distance for takeoff, but an aircraft carrier’s runway might only be about 300 feet long. How is that possible? Part of the answer is the aircraft carrier’s catapult launcher system. Inspiring by such systems, Tom Stanton created this electromagnetic model aircraft launcher and it is a perfect example of iterative design.

Traditional aircraft carrier catapult systems relied on steam pressure to actuate a piston at tremendous speed, pulling the plane along with enough acceleration to reach the necessary takeoff airspeed within the short length of the runway. But it takes a long time to build up enough steam pressure and that process is very inefficient, so the US Navy began experimenting with the Electromagnetic Aircraft Launch System (EMALS). That was first installed on the USS Gerald R. Ford in 2015 and it works a bit like a linear electric motor or a rail gun: synchronized electromagnetic attraction and repulsion convert electricity into motion. Stanton’s launcher works in the same way.

Stanton first attempted an electromagnetic launcher about two years ago, but he wasn’t very satisfied with the results. He used a microcontroller to control dozens of electromagnets, energizing them in sequence to accelerate the sled (and therefore aircraft). The big problem with that design it requires precise timing at extremely high speed, which can be difficult to achieve with digital control.

After a couple of years of thought, Stanton went back to the drawing board and developed a new idea: a purely electromechanical control system. It doesn’t have a microcontroller or any control electronics whatsoever. There isn’t anything electronic at all — everything is electric.

This takes the “linear electric motor” concept and applies it very literally. As the sled slides along, brushes touch contacts on the rails. When they do, they complete circuits to the energize the electromagnet on the sled. While energized, it is simultaneously attracted to permanent magnets on the rail ahead of it and repulsed by opposing permanent magnets on the rail behind it.

That concept worked surprisingly well right off the bat, but it is Stanton’s iterative design process that makes the video particularly interesting. For example, he found that off-the-shelf brushes were expensive, but that copper solder wick works just as well and is far more affordable. He also discovered that his original starting switch design bounced and that disrupted the intended energization sequence, killing performance. That led him to the creation of a new magnetic switch inspired by Reed switches, which barely bounces at all.

There are similar design evolutions shown throughout the video and they ultimately helped Stanton accomplish his goal: launching an RC airplane using magnets.