This might sound crazy, but I’ve been pursuing a Bachelor’s degree for about six years. What’s crazier is that I’m only half way done. I can explain: I go part time, and I needed a lot of pre-requisites that weren’t included in my previous degree.
What’s possibly even more crazy is that I have had ideas for my senior project since before I even started the program. I am here today to discuss one of those ideas. When I first had this idea, I had only a cursory knowledge of the technical details. Furthermore, I knew it was possible, just not what all it entailed.
If you read the title, you know the idea. Perhaps it’s about time I just said what it was. … I could just keep referring to it as “it” and prolong the anticipation for the big reveal. That is, of course, assuming you have not read the title of this post.
The idea is guided artillery. Not a new concept. However, most guided artillery is designed with one major criteria that we will be leaving out of this project:
Traditional Guided Artillery Design Criteria
- Kill People
However, my idea still involves guiding a projectile at a person (in theory). However, this projectile would not explode on impact. It wouldn’t explode at some proximity. It wouldn’t explode at all. In fact, it would be soft, and grippy… Like a Nerf football.
So, let’s list the desired end-user functionality of this guided artillery football:
Toy Guided Artillery Design Criteria
- Be throwable, like a football.
- Be catchable, like a football.
- Change direction during flight so as to minimize the distance between itself and some designated target.
Numbers one and two seem simple enough. There might be some off-the-shelf items that could cover those bases. I don’t know, maybe I’m underestimating the difficulty of those two criteria.
Number three is the real challenge. How the hell do you make a football guide itself to a target? The first problem that comes to my mind is that the ball’s flight time is limited by who threw or kicked it. That greatly limits its ability to reach a target. Secondly, the ball has no control surfaces with which it could change its direction during flight. Along those same lines, it requires a lot of practice to develop the skill required to throw a stable-flying football. Finally, and probably the worst part, it takes A LOT of fast-moving data and sensing to fly anything toward a target.
So, let’s split this big problem up into little bite-size, chewy pieces.
- The Guidance System
- Navigation – “Where am I?”
- Guidance – “Where am I going?”
- Control – “We’re in the pipe, 5 by 5!”
- Control Surfaces
The guidance system may be the most complex part of the project. However, flight isn’t easy. Flight is mostly a mechanical issue. And, in this case, the control surfaces will be totally experimental. Therefore, the flight surfaces cannot be trusted. Stabilization is easy enough, though. We just need to stick some fins on the back. Or a long, flowing tail.
The control surfaces themselves are rather difficult. In order for the football to be throwable and catchable, the control surfaces need to be discrete. In other words, they need to be hidden away until they’re needed. Furthermore, typical control surfaces on an air plane take advantage of the large lift-generating wing in front of them to alter the lift output. The football will have small stabilizer wings, if any wings at all. That means that it will not generate its own lift. Therefore, the control surfaces are actually going to be simple air brakes.
Now that we have the “simple” part out of the way, let’s move on to the complex part. The guidance system needs to answer two questions continously: 1. “Where am I?” and 2. “Where am I going?” The answers to these questions will determine which control surfaces deploy and at what time. However, answering these questions is potentially very difficult.
“And you may ask yourself
Well, how did I get here?”
I propose that the guidance system use an inertial measurement unit and a fixed-point reference (the starting location) to determine where it is. To do this, the football will require an accessory: A throwing glove. The throwing glove will have magnets embedded at strategic locations along the gripping surfaces. The ball will have hall effect sensors in close proximity to its outer surface. In this way, the ball will know when it has left the thrower’s hand.
Next, the ball will have an accelerometer and possibly a gyroscope. Many accelerometers are now capable of measuring the constant pull of gravity and comparing it to the X, Y, and Z axis. When the hall effect sensors detect that the ball has left the thrower’s glove, and by measuring the change in acceleration on 3 axes and comparing them to the acceleration of gravity, the ball will know approximately its location relative to its starting point.
But, how does it know where to go? I’ve been putting a lot of thought into this. The best I have right now is, “I don’t know.” I don’t know, because of the following reasons:
Reasons I Don’t Know
- The form factor limits the complexity and fragility of on board sensors.
- The form factor also limits the accuracy of on board sensors, because the ball cannot be expect to be precisely stable. In fact it may intentionally be spun about its axis to gain distance.
Anyway, while writing those last two sentences, I had an idea aside from all the commonplace ideas (cameras, infrared, radar, GPS, etc). However, this idea greatly limits the “fun factor” of the concept. Although, it does use the existing hardware and adds only one more accessory:
THE CATCHER’S GLOVE.
The catcher’s glove will essentially just be another thrower’s glove. It will be exactly the same. The difference, though, is how it is used. Before the ball is thrown, it must be told what mode it is in. The first mode will be “target mode”, wherein the catcher makes contact with the ball. While making contact with the catcher, the ball initializes all of its location variables. Essentially, X=0, Y=0, Z=0. Next, the ball is placed in “launch mode”. In this mode, it is recording changes in its location and waiting to both make contact with the thrower’s glove AND to lose that contact. Upon losing contact, the ball enters “flight mode”, wherein it tries to get all of the axial changes back to zero by actuating the control surfaces accordingly.
And that, my friends, is the football that can’t not be caught.