Public Missiles Ltd. Thunder & Lightning

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My project for 1999 was the two-stage PML Thunder & Lightning. My master plan at that time was to get experience with a two-stage, dual-deployment project and follow on with a bigger two-stage project afterwards using the sustainer only for  Level 3 certification.

I ordered the Thunder & Lightning (I'll call it T&L from here on out) with pre-fiberglassed phenolic tubing and PML's original CPR dual deployment system. I was hoping to modify it to use my existing Altacc, and I purchased a model ES236 dual sequential stager from Adept to do the staging. The T&L is a 2.5" diameter kit with a 38mm motor mount. It has three fins for each stage and an ogive nose, and a cast polyurethane boat tail in the booster. 

I figured that I would learn a lot with this project: first through-the-wall fins, first two stage, first electronic deployment, first fiberglass fins.  Yikes.

I wanted to use rail buttons rather than the supplied launch lugs. Since I couldn't think of a better way to support the rail button screws, I had several 1/2"W by 6L"x 1/8" deep strips of aluminum machined with a 1.25" radius to use as backing supports for the rail buttons. This was absolute overkill and subsequently I've learned more efficient ways to do this, but nevertheless, those aluminum backing strips got built in. 

I started with the booster section (bad idea) using hobby shop epoxy. All went well through completion although I left the issue of constructing a hatch for access to the interstage coupler electronics as a TBD.

I also completed the lower section of the sustainer, comprising the fin can and the motor mount. In the meantime, PML had announced a newer version of the CPR  hardware and had a retrofit kit available. I ordered the "CPR 2000" retrofit kit and looked it over carefully upon receipt This retrofit would make it much easier to assemble in the field, replacing many shear pins with two screw-together sections. However, it was still built around a specific altimeter (I forget which one) and didn't quite fit my Altacc. I stopped constructing and started chewing this problem. I went off on some tangents with electronic bay modifications. I was also still chewing the hatch problem for the interstage coupler. These problems, combined with a crunch at work ended up stalling me out completely and I walked away from the project for a few months. 

In retrospect, I think I just felt uncomfortable with this rocket, and I think I doubted that it would fly without crashing. There were several things I didn't like, including putting a hatch in the naked phenolic coupler, and the wide nylon strapping and recovery pistons. I stopped thinking about rockets for a while, let my AERO-PAC membership lapse, and spent my hobby time playing golf.

I finally got interested in rockets again in late 2000, and decided just to walk away from this thing without finishing and get a fresh start with a straightforward single stage for a level 3 attempt. I ended up using the various subassemblies of the T&L to practice techniques for the next project. On one such practice session, I had laid up carbon fiber tab reinforcements on the T&L booster section fins, and at one stage of the curing, had it standing upright on one of my barbecues. I went on an errand to drop the daughters at music lessons and a slight breeze came up while I was gone. The booster fell off the barbecue and dropped thirty inches to the cement patio. This minor accident caused a 1/2" crack on the top edge of the airframe! The gods didn't mean for this one to happen, and I happily threw it all in the trash. (This result should not reflect badly on PML or this kit, I believe this was just the wrong project at the wrong time for me).

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