When is a rocket still the same rocket?

Let's say you crash your rocket. Ever the optimist, you say "it will fly again!"
What does that mean exactly? Everyone knows that if you repair a zipper or
fix a cracked fin, it's still the same rocket. But what if you replace a major body tube? Or the fincan? Is it the same rocket, or not?
Not that it's a big deal, but I could the flights on all my high power rockets. I have a magnum that has 35 flights, and it just suffered its third CATO. I just replaced the top 12" of the booster and the 20" body tube section between the booster and the altimeter bay. Is the next flight going to be #36 for the magnum, or #1 for some freakish mutant of the magnum?
Looking for your opinions!
-- David
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I consider the fincan the "rocket". Replace that, and it's a new bird.
--
Joe Michel
NAR 82797 L2
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J.A. Michel wrote:

Same here. In fact my rockets are designed with a removable tail section (fin can) to facilitate replacement of the forward airframe if it becomes damaged. My payloads are all interchangeable and get switched from one rocket to another as needed.
Sometimes I've taken a fin can that has intact fins but suffered some airframe damage, stripped it down to motor mount and fins, and built a new airframe around it. In cases like that I still use the same "rocket number" but add a version number. For instance, "BB-6" becomes "BB-6A".
a
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What if it were a car? If you replaced a just 1 fender, a door, the windshield, a rim, etc. is it the same car?
Maybe it comes down to a percentage. Some of it is, some of it isn't. It's a little of both.
Randy www.vernarockets.com
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What I do, just for my own preference, is say that it's the same rocket if I replace less than 50% of the original weight. On most rockets, the fin can/motor mount is usually close to 50% of the weight of the rocket. Bottom line, it's your rocket, call it what you want.
David wrote:

--
Christopher Brian Deem NAR 12308 TRA 2256 level II

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I look at it this way -
("I hold in my hand George Washington's hatchet. Well, the handle cracked a few years ago so I had to replace it. Then the head got very rusted, so I replaced it, too. But it occupies the same space.")
Isn't it the same with rockets?
--
Mike KD7PVT
NAR #70953 - Sr/HPR Level-1 ~ BEMRC - NAR Section #627
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Mike Pearson <see .sig> wrote:

Just like "Star Trek: The Motion Picture". The Enterprise went through a "refit"....yet, when it was said and done....was about 99.999999% different from the original. Oh....wait...it *did* occupy the same coordinates in the "space-time continuum".
:o)
--

Greg Heilers
Registered Linux user #328317 - SlackWare 10.1 (2.6.10)
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I visited the USS Constitution ("Old Ironsides") in Boston Harbor about 15 years ago. They advertise it as the oldest commissioned warship in the U.S. fleet (since early 1800's)...but only 10% of the ship is "original". If the government can do it, so can you.
">> I look at it this way -

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I guess thats why I modularize my rockets back home... I built a fincan, put a couplar there, then a tube, then payload (if any) then nosecone. That way if the thing should zipper, I can replace the tube without having to cut it or anything. Plus I could like mix and match and get all kinds of crazy configs (and color schemes)
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There is a theory regarding the transmigration of rocket sould, so that by preserving a component of the original rocket, its essence will be present in the rebuilt rocket. The components are but a shell, a vessel for the essence of the rocket.
If you believe that, I have some prime real estate in southern Louisiana for sale.
Bill Sullivan
"For every complex problem there is an answer that is clear, simple, and wrong." H. L. Mencken
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David wrote:

To me, it would depend on the extent of repairs at each stage, and whether or not the rocket still maintains any original parts.
If you've replaced everything, it's not the original rocket anymore.
If you replace more than 50% at one time, it's not the original rocket anymore.
-Kevin
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Absolutely. It is a rocket with _history_. Rocket WhatsItsName with n flights and x, y, and z repairs. As long as it is less than 100% per repair, and a flight is executed, then the new parts are as integral as the former and are permanent proxy.
What about a rocket that has interchangeable fin cans based on payload?
What about a rocket with changeable motor mount?
What about removeable fins?
Rockets have no permanent "skeleton" per se. They are rather a system of parts making up a whole, each with a different task.
I have a rocket (an Estes ARV) that does not use a fin can. It instead has twin gliders that act as fins until separation at apogee. I have replaced just about everthing on one glider or the other due to happy young fingers breaking them when they to go to retrieve them or throw them around, or one glider goes missing. I have had to repair both body tubes and all glider mount points. I have upgraded the mount points so they do not break as often (they actually have not broke since). But it is still the same rocket, and is always the highlight of any launch with young people.
For these and other reasons, I feel that rockets are more like a company: employees come and go, owners, shareholders, or CEO may change, locations an equipment may change, but it is the same company, with _history_.
For those who are more into the "science" of rocketry, it may feel appropriate to add a letter or designator, but for me it is still just _history_; the extra designator doesn't add anything with out the knowledge of the history that designator represents.
~ Duane Phillips.
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