How Long Do LPRs Last? (And Does Anyone Even Care?)

[mh9162013]

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.

 

[Starfire73]

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.

I think it would be an interesting study, but I would prefer to see it conducted with the rocket built stock, 100% according to the instructions. Then document the parts and systems as they fail. If needed, once a part fails then you could upgrade and mod the parts which failed in order to keep the study going to test the other parts which haven’t failed yet.

My money would be on plastic chute (including shroud lines) failing first, then the cheap rubber band shock cord, then eventually the body tube near the front end of the motor mount where the pressure and heat from ejection will weaken it over time.

Maybe not count fin damage and repair as that tends to not be related to the rocket’s longevity issues. Or perhaps it might be interesting to see how many times you had to repair or re-glue a fin.

Once you’re all done with that, then mod/upgrade a new version of the same model and start over - comparing the results between the two. See how effective your mods were.

 

[Tractionengines]

You might want to look at this thread. https://www.rocketryforum.com/threads/most-flights-you-ever-got-out-of-a-rocket.168932/#post-2191928 Some of these are counting into the 100's of flights, but have had repairs over that time.

The next question is what are you going to call "normal wear and tear"? Then is that fixed, or left go. ie. Say you find a soft spot at a tube sprial. Do you: 1) Just keep going to failure. 2) Add a coupler for reinforcement, and keep going. 3) Tear off the body (or section) and replace it. 4) Consider that the end of life and report that as the max # of flights for that rocket. All of these could be done.

Personally I fly with a number of young kids... (4, 6, 9). They are "harder" on the LPR rockets than anything else, but it's all in the learning curve. Also, in our area field size is small with lots of hungry trees. I have lost more of my "good" rockets as a BAR to trees, than anything else.

 

[mh9162013]

Once you’re all done with that, then mod a new version of the same model and start over - comparing the results between the two.

I agree, that would be ideal. But that would double the cost of the study. Doing just one run with a stock rocket would probably cost anywhere from $50-$100 dollars. With an upgraded rocket, probably $75-$200.

So yes, that's ideal, but I may only be able to afford just one run through.

 

[mh9162013]

The next question is what are you going to call "normal wear and tear"? Then is that fixed, or left go. ie. Say you find a soft spot at a tube sprial. Do you: 1) Just keep going to failure. 2) Add a coupler for reinforcement, and keep going. 3) Tear off the body (or section) and replace it. 4) Consider that the end of life and report that as the max # of flights for that rocket. All of these could be done.

That's a great point. Definitely something I'd have to decide on before running the test.

 

[neil_w]

Most Flights You Ever Got Out Of A Rocket?

I imagine this question has been asked many times before here, but not seeing such a discussion myself, I have to ask: What if the total number of flights you ever got out of a single rocket? Before it just plain wore out? Or otherwise lost it to a failure? Or a tree? Really would like to...

www.rocketryforum.com

 

[Spitfire222]

Fwiw, I have a Google Sheets document that logs the status and flights of all of my rockets. It's mostly to keep track of motor options and flight results/altitudes, but it's interesting to see which of my rockets has flown the most. Full disclaimer, I'm a pilot and engineer, so data collection and logging flights is in my DNA I guess!

 

[Scott_650]

My most common failure point on my oldest rockets - all built from kits (various makers, mostly Estes) and now well over ten years old - have been the motor mount centering ring to the body tube glue joint. The next most likely has been the rubber shock cord. Granted we’re only talking roughly a dozen or so data points but outside of crash and/or tree related damage it’s been those two areas that have experienced multiple failures. Only one has been unrepairable though, technically, I could’ve just built an entire new motor mount but I chose retirement to display duty instead.

Unfortunately I wasn’t tracking number of flights to failure so there’s no hard numbers just my general anecdotal impressions - I’d guestimate at least a 10-15 flights until failure as a minimum. This looks like a good topic for next year’s vNARCON…

 

[Grog6]

I've got a few rockets that are over 30 years old; they don't typically wear out, they usually come to some traumatic end: river, ballistic recovery,cato, dog, cow, and rattlesnake come to mind.

 

[CalebJ]

Rattlesnake?

 

[BEC]

As noted in that other thread here #7 I have a couple of BT-50-based LPRs with just over 100 flights on them, but with some component replacement/repairs over that time. Shock cords and 'chutes are the two components that were multiply replaced in both models. More details in the linked post.

I would expect, based on my experience, that if you built a stock Alpha, using the current components in the kit — a reasonably long rubber shock cord in a tri-fold mount and the supplied orange/white plastic 'chute — and you were lucky with getting the right amount of wadding in there to protect that stock 'chute yet still get that 'chute out reliably (so no lawn darts), that the shock cord would fail at or near the mount 40-50 flights in. Depending on the flying site, partially deployed 'chutes may or may not lead to broken fins (this would also depend on the nature of the balsa in the kit you based your experiment on as there is quite a bit of variation there).

Kevlar shock cords won't last longer, especially if you tie to it the motor mount. There it will burn through in anywhere from 2 to 30+ flights. If put in via a tri-fold, it will eventually get sawn through by the upper end of the body tube. I put a heat-shrink tube on kevlar shock cords where they rub against the top of the body now to alleviate that, but don't have enough flights on a model set up that way to be confident in saying that doing that solves the problem. The regular rubber shock cords actually will survive this longer, but they do dry out over time, so in part it will depend on the time frame over which this experiment is conducted.

For my own purposes I consider 'chutes and shock cords to be wear items and just replace them when needed. The Alpha, if the shock cord fails at the top of the body, will often streamline in...and that, of course, can lead to severe body damage if you're flying over most surfaces.

 

[rharshberger]

Rattlesnake?

Snake has it, snakey keeps it, I aint fightin a rattler for a rocket...

 

[dr wogz]

reminds me of this:

 

[hobie1dog]

I've only shot off less than 20 rockets in my life, age 66, they will outlast me.

 

[BigMacDaddy]

In my opinion, not worth it to do a dedicated study -- better to survey experienced rocketeers about the history / life of their favorite rockets... Would actually be more representative / generalizable data.

 

[Cape Byron]

"How many cabs in New York City?
How many angels on a pin?
How many notes in a saxophone?
How many tears in a bottle of gin?
How many times did you call my name?
Knock at the door but you couldn't get in?"

Paul Kelly, 'Careless'

 

[smstachwick]

In my opinion, not worth it to do a dedicated study -- better to survey experienced rocketeers about the history / life of their favorite rockets... Would actually be more representative / generalizable data.

Well hey, look at that! We’ve got ourselves a survey right here!

 

[mh9162013]

In my opinion, not worth it to do a dedicated study -- better to survey experienced rocketeers about the history / life of their favorite rockets... Would actually be more representative / generalizable data.

You may be right...

 

[bjphoenix]

My oldest rocket is about 54 years old so the components can last a long time. I know someone who has one Estes rocket that they have launched over 200 times.

 

[beeblebrox]

Rocket longevity is inversely proportional to the degree of finish...lol

When that rocket you built that has a finish that would make Ferrari jealous explodes on the pad with a massive cato...

 

[Back_at_it]

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.

 

[afadeev]

So I [...] 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.

Most of my rockets last WAY longer than my interest in flying them.
I move on, building and flying newer/other rockets. The older ones that had been built and flown (I fly all of them at least once) and are now sitting in storage and will last until they get either damaged during another flight, another relocation, get handed out to scouts, or get thrown out.

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?

Without knowing your exact methods of building and "improving" on "stock" construction methods - not too many.
I haven't built a "stock" LP rocket in ages. No more elastic shocks cords (Kevlar braided string only), plastic chutes (nylon only), metal spring motor retainers, or non-papered balsa wood components for me. Consequently, any results of durability for rockets absent of those improvements are ... of little practical value.

Net of those improvements - I know a rocket will outlast my interest in flying it. Unless a tree or the winds claim it first.

 

[mh9162013]

I haven't built a "stock" LP rocket in ages. No more elastic shocks cords(Kevlar braided string only), plastic chutes (nylon only), metal spring motor retainers, or non-papered balsa wood components for me. Consequently, any results of durability for rockets absent of those improvements are ... of little practical value.

I hear ya. I'm inclined to to a test with certain improvements. But then the problems arises with how those improvements are implemented. So that supports the idea of using a stock rocket for the tests.

I've concluded that doing a durability test will require at least two types of rockets (stock and modified). But I can't afford to do that. Even if I could, I don't think the overall interest would justify the time, money and effort.

This isn't to say the results wouldn't be interesting. But anyone who's seriously into rockets to care about this type of experimentation and data would probably be shifting their focus to MPRs and HPRs...or at least heavily modified LPRs.

 

[BEC]

This isn't to say the results wouldn't be interesting. But anyone who's seriously into rockets to care about this type of experimentation and data would probably be shifting their focus to MPRs and HPRs...or at least heavily modified LPRs.

I don’t know about that. I’ve already described in similar threads on this topic what mods I do to my LPRs. The ones I like get flown quite a bit. I have many LPRs with over 30 flights on them, and at least four I can think of with 75 or more. This is all with stock ’chutes (at least at first, and after they are worn out/burnt up they get replaced with similar plastic ones), and stock shock cords (though they are often attached to a foot or so of Kevlar — and it’s the Kevlar that fails as often as not when the shock cord does fail).

As I said in my prior post, I consider ‘chutes, streamers and shock cords as wear parts, like belts or tires on your car, though they generally get replaced “on condition” — that is, when they fail — rather than before they do as one would normally do for your car.

The last couple of Nova Payloaders I have built have a stage coupler inside the body tube right above the motor mount. This is because with that model’s long fins, even a reasonable landing can tweak the body tube right where the LE of the fin meets the body. That, and not flying them more than a couple of times with Aerotech single-use D10s or D24s which have a blowtorch of an ejection charge, and I have no more problems with body buckling there. The currently active one’s next flight will be number 97. That one has had a bunch of Q-Jet C12-6FJs and a few C18-6Ws and D16-6FJs, as well as a D20W or two in it. They don’t seem to be the problem the D10/D24s are. That particular model has been flown once, I think, on a D10-7W.

None of this is what I would characterize as a “heavy modification”.

Most all the MPRs I fly are just big Estes kits or use similar parts. I do have a couple of LOC models (a ”park flyer” IRIS and a Weasel), and every time I pick one up I notice how much heavier they are. To me the extra weight is not a good trade. I may or may not see how long the LOC-supplied elastic shock cords last before they let go on these models.

I will probably never take any MPR model to anywhere near 100 flights. I only have a few with more than a handful of flights. These are my Semroc SLS Aero Dart (currently at 28 flights), which most often flies on an Estes E16 or F15 or the new Aerotech/Enerjet F52C, and my 256% upscaled Nova Payloader (currently at 20 flights, usually on Gs, but two on H impulse motors), which is built from Estes PSII builder-series kit parts. I wish I’d reinforced it with a coupler at that spot where the fin LE comes to the body. The Aero Dart is on its second nylon ‘chute I think, and I’ve had several different ‘chutes in the big Nova Payloader depending on the flying site, winds, motor and whether or not I’m running a Chute Release in it for a given flight.

 

[mh9162013]

I don’t know about that. I’ve already described in similar threads on this topic what mods I do to my LPRs. The ones I like get flown quite a bit. I have many LPRs with over 30 flights on them, and at least four I can think of with 75 or more. This is all with stock ’chutes (at least at first, and after they are worn out/burnt up they get replaced with similar plastic ones), and stock shock cords (though they are often attached to a foot or so of Kevlar — and it’s the Kevlar that fails as often as not when the shock cord does fail).

Do you consider yourself to be in the model rocketry majority or minority in this respect?

 

[BEC]

Do you consider yourself to be in the model rocketry majority or minority in this respect?

I‘m probably an outlier…but you said “anyone who’s seriously into rockets”, not “most people who are seriously in to rockets”.

I also fly altimeters in just about everything, which is also not the most common thing, but I still consider myself within “anyone who‘s seriously into rockets”.

 

[MidOH]

Rocket longevity is inversely proportional to the degree of finish...lol

When that rocket you built that has a finish that would make Ferrari jealous explodes on the pad with a massive cato...

My Ferrari had a terrible paint job. Thin. The Ducati's paint is much finer, but neither machine is meant to be scratch free, ever.

It's the primer only "until it's tested" guys, that really attract Murphy. I always paint now. But the first scheme is the simplest. The repair schemes are when I add stripes and such.

I laugh when Nasa or whoever pushes rocketry as a ''science'' hobby that leads to engineering. Because it's mostly autobody dust bunny stuff.

 

[mh9162013]

I‘m probably an outlier…but you said “anyone who’s seriously into rockets”, not “most people who are seriously in to rockets”.

Fair enough. Thank you for your input, it's much appreciated.

 

[rharshberger]

Fair enough. Thank you for your input, it's much appreciated.

Believe me Bernard is seriously into rockets, he flies more in a weekend that me and my three kids do in a year, and my kids rockets eat Estes 24packs faster than I like buying them....

 

[jrap330]

I've got a few rockets that are over 30 years old; they don't typically wear out, they usually come to some traumatic end: river, ballistic recovery,cato, dog, cow, and rattlesnake come to mind.

did the rattlesnake eat it?