How I decided on my L3 project in high power rocketry

Once I completed my level 2 certification, I had been spending a lot of time thinking about what, exactly, I should build for my level 3 project. And more generally, how should I approach it?

Cardboard or fiberglass?

I’ve built both cardboard and fiberglass rockets, and each has advantages depending on what you’re trying to achieve. I had initially assumed any L3 project would need to be fiberglass, and I’d been looking at some very large and very heavy rockets.

Fiberglass is more durable than cardboard, and is the strongest building material aside from metal. It won’t change size based on fluctuations in temperature, and it won’t swell up or get ruined if wet. This is particularly important since the rocket parts need to slide over each other using couplers. But the primary drawback of fiberglass is that it’s really heavy.

Cardboard (especially when properly reinforced with epoxy) is still durable but more lightweight, and that is a key characteristic when you are trying to defy gravity and launch something into the air. A cardboard rocket will go a lot higher than a fiberglass rocket on the same motor.

While agonizing over this fundamental choice, a solution appeared, from out of nowhere.

Deus ex machina

I had previously met and worked with Scott Binder, the owner of Scott Binder Rocketry (“SBR”), creator of the Fusion Rocket, as well as high power rocket motors and accessories. Scott’s shop is located in Walla Walla, Washington. His flagship rocket is the Fusion, but he’s recently been developing a new, larger version of the Fusion that is specifically for L3 certification – and long story short, I agreed to do some beta testing on this rocket.

white rocket with red and black design
L3 Fusion finished design

In addition to building the rocket and using it for my L3 cert, I am going to create a video tutorial with Scott for the construction of this rocket, from start to finish. I’ll link to that as soon as it’s ready.

L3 Fusion

The L3 Fusion itself is roughly 90 inches in length and a 5.5 inch diameter. With a 75mm motor mount tube, it’s capable of flying an M motor, and I plan to fly it on an Aerotech M1297 for the cert flight. The great part about cardboard is that this rocket only weighs about 22 lbs fully loaded, and it should come close to 10,000 ft. at apogee on the M1297.

L3 Fusion rendering in Open Rocket

The electronics bay will have two RRC3 altimeters, each powered by a 9V battery, and will use omni-directional black powder charges for separation and deployment of the parachutes during flight. The drogue chute is 24 inches and the main chute is 84 in. Descent should be less than 20 feet per second under the main chute.

There are more details forthcoming, but right now I’m excited to dive into this L3 project! I need to begin putting together a comprehensive document describing the rocket, with a lot of technical information. Later, once I begin building, I’ll include a lot of detail about the construction process and materials, with plenty of photos documenting the build step by step. And much later, once it’s complete, the most exciting part: flight!

More to come soon!

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