So I posted a thread recently
and one of the topics that came up is how long LPRs (or certain components inside an LPR) can last. It seems like no one really knows, and there's any number of reasons: people don't keep count of their flights for a rocket, rockets gets lost, destroyed or eaten by trees, rockets that last a while eventually get retired and sit on a shelf, etc.
So here's my question: if I (or anyone else so inclined) were to take a generic BT-50 or BT-60 3FNC or 4FNC type of rocket and run a bunch of engines through it, how many people here would care about the results? For example, I might take an Estes Alpha and build it 100% stock (or with a few mods, like adding a baffle and using a Kevlar shock cord), then run 13mm and 18mm engines through it and see how long the rocket (or one of its components, like a shock cord) lasts until it can no longer fly without major repairs. And if the rocket survives the several dozen engines run through it (and I can no longer afford to buy more engines), I'll do an autopsy of what I find inside the rocket.
So if you'd be interested in such a "study," let me know. And if you have any suggestions or other thoughts, I'm all ears.
How long a rocket lasts depends on the materials used in it's construction. Lets take a box stock normal Estes kit like the Generic E2X. These are thin wall tubes with plastic fins, rubber shock cords and plastic parachute. The first issue you normally run into with these is that the shock cord becomes brittle with from age or the heat from repeated launches and breaks. I've had this happen on the first launch but typically they will last about 3 yrs. or 10 flights before they need to be replaced.
Next is the plastic chutes. Typical issues with these is that they either melt or the lines get pulled through the plastic and detach. Again, This can happen on the first flight or the 10th but it will happen.
Eventually the thin wall body tube will become weakened from the repeated launches and ejections. While this happens less often, it does occur. Obviously the larger the motors you run the more this becomes an issue. I had an old Challenger 1 back when I was a kid that we eventually had to replace the tube on as it became so soft that it was unflyable.
Of course there are all of the little things that happen to a rocket like broken fins, dents in the tube, paint chips, lost nose cones etc. etc.
The good news is that most of these things are preventable but it does take adding some different materials to your build. Let's use my scratch built test rocket as an example. This rocket is the first rocket up at every launch. If we don't like the results we will sometimes send it up a second time until we're happy with the landing. Looking at the logs this rocket has now flown 45 times.
It is built with an 18" Estes BT55 tube. Inside the tube is a coupler that runs from the top of the motor mount and stops approx. 1 inch from the top of the body tube to allow the nose cone to be inserted. This effectively creates a heavy wall tube. The motor mount is a BT50H tube with a plywood upper centering ring and paper rear ring. Inside the motor tube is a small motor block made from cardboard but has been coated in regular TBII wood glue for some heat protection.
A baffle was added inside the coupler approx. 7 inches down from the top. This eliminated the need for wadding and protects the recovery gear from the ejection. Attached to the top plate of the baffle is a section of 700# Kevlar. This serves as a leader and is the attachment point for the shock cord. The Kevlar stops about a 1/4" below the top of the tube. The Shock cord is 1/4" elastic and gets attached to the Kevlar and the nose cone. Like the rubber shock cords, Elastic will eventually need to be replaced but it's a simply job of cutting out the old and attaching a new piece to the Kevlar. As for the parachute, there is a loop in the shock cord where I attach the appropriate sized chute for the field / wind conditions of the day so there is always a fresh chute in the rocket. On the outside of the rocket, the fins are Basswood and were coated with sanding sealer.
With a little planning and some better materials, you can build a rocket that will pretty much last until you lose it
Or you can simply buy a better quality kit that comes with all of this stuff right out of the package.
I've done a few builds here that show these various items in detail if you're looking for examples.