Ever since I began dabbling in the model rocketry hobby, I’ve been struggling with one particular issue – how do I keep the rocket stable before launch, and launch safely? As we saw from HORIZON I, using a simple wood base is not sufficient for the safe launching of model rockets. This launch pad is made out of a mix of ¼” aluminum, 3D printed parts, and wood. This launch pad also boasts an articulating launch tower, allowing you to fine-tune the rocket’s attitude before launch, and arm the rocket much more easily.
The launch pad consists of a square of 20/20 aluminum extrusion with a ¼” sheet of aluminum bolted on top. This sheet holds the pivot brackets and acts as our main launch pad base. A smaller, ¼” piece of aluminum is suspended above this base and connected with the pivot brackets to allow it to articulate 90 degrees. This is the pivot base. A 2 ½” x 1” wood plank is bolted to this pivot base to act as the launch tower. On the launch tower, servos are attached to hold the rocket in place and allow for release of the rocket when the engine lights. Furthermore, a cylinder-looking piece is bolted to the pivot base to raise the rocket up for access to the motor and extra clearance.
As for stability, the simple 20/20 aluminum extrusion square isn’t enough. That’s why I developed these “wings” that increase the surface area of the rocket base and make it heavier, causing the pivot bracket to not tip the whole launch pad when it’s lowered. Four of these are necessary, one on each corner, for proper use of the launch pad.
Importance of a Launch Pad
The importance of having a safe launch pad for rockets cannot be understated. The gyroscope sensors used on STARLIGHT and all other MEMS-style sensors are relative, meaning they measure degrees/second. While it would be possible to detect absolute pitch & roll with the accelerometer, and actually do collect this data, it’s simply not accurate enough for proper launching of rockets. For a thrust vector controlled rocket, it’s typical to have to align the rocket to +-0.1 degrees of its target attitude (sometimes more). This is simply impossible to do without a launch pad with an articulating axis. The pivot was also added to help access the bottom of the rocket, for pre-flight checks, easy assembly, and access to the motor.
The launch tower is necessary for holding the servos in place and keeping the rocket steady, no matter the angle the pivot base is at. Aluminum was chosen for many of these pieces because of its strength.
Risk Mitigation
Now, the main concern – these parts are expensive. What would my plan be if this design simply doesn’t work? I have safe-measures and tests in place to mitigate this risk as much as possible.
Before I order any aluminum pieces, I 3D print replicas of the pieces and make sure they fit with each other and with the servos and aluminum extrusion. However, some pieces (like the base and wings) are too big to be 3D printed. These will be made in aluminum directly, as they aren’t too expensive nor complex.
I have an entire CAD mockup of this design in Fusion 360, so I can validate that holes are the right sizes, dimensions are accurate, and everything will fit together nicely. Many of the connecting pieces are 3D printed as well, so given poor tolerance from the factory or a wrong measurement, I can easily re-print the connecting pieces and not touch the aluminum.
Conclusion
In order to launch the next iterations of HORIZON, a safe launch pad is necessary. After much research and many, many visits to the BPS Space website, I have determined that this is one of the most cost-effective and practical ways of launching rockets. Simply put, launch pads are the best way of launching rockets, even at the model scale.
Cost Breakdown
I decided to include my estimated cost breakdown for this project, if you’re interested! Some small parts like servos and screws aren’t included, this is mostly the large, more expensive parts.
