Question on allowable reuse of parts for an L3 Cert Rocket

[Bob G]

I recently attended a Tripoli HPR launch and rekindled my teenage love of rockets. After seeing some amazing M & N launches my goal is to become L3 certified. I am cost conscious though and am considering whether or not I can afford this hobby. Can a Tripoli TAP comment on the following:

1. Can a redundant, dual deploy sled + electronics used from a prior L1 or L2 rocket be used on your L3 certification attempt? Must 'brand new' electronics be used? Must you build a new sled?
2. Can the entire redundant dual deploy avionics bay from an L1/L2 rocket be reused on your L3 certification attempt?
3. Can the nose cone from a previously flown L1/L2 rocket be used on your L3 certification attempt? Must a 'brand new' nose cone be used?
4. Can the parachutes - drogue and/or main - from a previously flown L1/L2 rocket be used on your L3 certification attempt? What about the deployment bag and/or nomex?
5. Can the motor casing from a previously flown L2 rocket be used on your L3 certification attempt?

It seems to me that a requirement to have new nose cones/parachutes/motor casings/avionics bay just adds cost to the L3 attempt but does not add to safety. However, reuse of a 'proven, known to work' dual deploy electronics would improve safety over using new, never flown before electronics IMHO. But, I would like to know the rules.

Thank you in advance!

 

[jimzcatz]

I recently attended a Tripoli HPR launch and rekindled my teenage love of rockets. After seeing some amazing M & N launches my goal is to become L3 certified. I am cost conscious though and am considering whether or not I can afford this hobby. Can a Tripoli TAP comment on the following:

1. Can a redundant, dual deploy sled + electronics used from a prior L1 or L2 rocket be used on your L3 certification attempt? Must 'brand new' electronics be used? Must you build a new sled?
2. Can the entire redundant dual deploy avionics bay from an L1/L2 rocket be reused on your L3 certification attempt?
3. Can the nose cone from a previously flown L1/L2 rocket be used on your L3 certification attempt? Must a 'brand new' nose cone be used?
4. Can the parachutes - drogue and/or main - from a previously flown L1/L2 rocket be used on your L3 certification attempt? What about the deployment bag and/or nomex?
5. Can the motor casing from a previously flown L2 rocket be used on your L3 certification attempt?

It seems to me that a requirement to have new nose cones/parachutes/motor casings/avionics bay just adds cost to the L3 attempt but does not add to safety. However, reuse of a 'proven, known to work' dual deploy electronics would improve safety over using new, never flown before electronics IMHO. But, I would like to know the rules.

Thank you in advance!

Yes to all questions.

 

[rfjustin]

I recently attended a Tripoli HPR launch and rekindled my teenage love of rockets. After seeing some amazing M & N launches my goal is to become L3 certified. I am cost conscious though and am considering whether or not I can afford this hobby. Can a Tripoli TAP comment on the following:

1. Can a redundant, dual deploy sled + electronics used from a prior L1 or L2 rocket be used on your L3 certification attempt? Must 'brand new' electronics be used? Must you build a new sled?
2. Can the entire redundant dual deploy avionics bay from an L1/L2 rocket be reused on your L3 certification attempt?
3. Can the nose cone from a previously flown L1/L2 rocket be used on your L3 certification attempt? Must a 'brand new' nose cone be used?
4. Can the parachutes - drogue and/or main - from a previously flown L1/L2 rocket be used on your L3 certification attempt? What about the deployment bag and/or nomex?
5. Can the motor casing from a previously flown L2 rocket be used on your L3 certification attempt?

It seems to me that a requirement to have new nose cones/parachutes/motor casings/avionics bay just adds cost to the L3 attempt but does not add to safety. However, reuse of a 'proven, known to work' dual deploy electronics would improve safety over using new, never flown before electronics IMHO. But, I would like to know the rules.

Thank you in advance!

FPNI

 

[tfish]

Yes..but contact a TAP in your area to get the process started. Those questions are a good starting point.

Tony Alcocer TRA TAP (15+ years)

 

[Bob G]

I given the way I worded those questions above, I want to reconfirm that 'yes' means:

1. Tripoli rules allow reuse of any or all of the motor casing, nose cone, avionics electronics, electronics sled, entire avionics bay, parachute, deployment bag and/or nomex used on a prior Level 1 or Level 2 flight on a Level 3 certification attempt.
2. While Tripoli rules allow this, your local TAP may not

Is this a correct interpretation? Thanks!

 

[tfish]

Your TAP may find that...some of those items are not appropriate, for use in a L3 project based on size, wear, condition, strength or (add other reasons here).
Again contact your local TAP..Tell them what you want to do and see what they have to say.

Tony

 

[Art Upton]

Your TAP may find that...some of those items are not appropriate, for use in a L3 project based on size, wear, condition, strength or (add other reasons here).
Again contact your local TAP..Tell them what you want to do and see what they have to say.

Tony

Yes;, for example the coupler used in an L1/2 rocket AV Bay may collapse in an L3 rocket under the greater G loads.

 

[kramer714]

Cant stress this enough, find a TAP / L3CC early, when you are first starting to think about getting level 3. The TAP /L3CC is trying to asses your skills and understanding of construction, materials, processes your experience etc. Plus they can give you overall guidance on the process and specific thoughts on what you are planing.

The sooner you talk to them the easier the process is... for them and you.

Mike K L3CC

 

[kramer714]

Yes;, for example the coupler used in an L1/2 rocket AV Bay may collapse in an L3 rocket under the greater G loads.

As a L3CC, I might ask, how did you size the coupler for the motor you are planning, how do you ensure that it is capable of what you are planning?

 

[tfish]

I would even go as far as suggesting that....

You should contact a TAP as soon as you figure out..that you're thinking about an L3 cert flight...
Even before asking/discussing it with your wife, significant other, mom or dad ..or even that voice in your head!

....levity...

Tony

 

[Bob G]

Thank you all for this information. I have two equally distant prefects and have not at yet decided which I want to use as my primary prefecture - which would affect who I would use for a TAP L3CC.

@kramer714 - I would size the coupler to assure 2x OD insertion into the booster and main deployment tube section with a 2cm separation ring. I don't know how to answer the 2nd question other than to say guidance given https://www.rocketryforum.com/threads/coupler-length-rules-of-thumb.124497/ and https://www.rocketryforum.com/threads/coupler-length-for-hpr-rocket-determining.107448/ . Coupler length is a tradeoff between stiffness and making sure the sliding friction does not prevent separation when the deployment charge fires. What sort of answer would you expect re that question?

 

[kjhambrick]

FPNI

Thanks for the new FLA Justin

 

[kramer714]

Thank you all for this information. I have two equally distant prefects and have not at yet decided which I want to use as my primary prefecture - which would affect who I would use for a TAP L3CC.

@kramer714 - I would size the coupler to assure 2x OD insertion into the booster and main deployment tube section with a 2cm separation ring. I don't know how to answer the 2nd question other than to say guidance given https://www.rocketryforum.com/threads/coupler-length-rules-of-thumb.124497/ and https://www.rocketryforum.com/threads/coupler-length-for-hpr-rocket-determining.107448/ . Coupler length is a tradeoff between stiffness and making sure the sliding friction does not prevent separation when the deployment charge fires. What sort of answer would you expect re that question?

Dont over think it, but, as a Level 3 you should be able to 'justify' your design. If the answer is the Madcow UberMeshuga kit uses the same design (thicknesses of coupler, switch band 'all thread' u bolts etc. ) and it is routinely flown with similar motors / rocket weights, / rocket length (bending moment) etc. I would be good with that.

Relative to things like shear pins - type / location, I would be looking for a calculation and a ground test to verify. Same goes for how the shock cord loads are transmitted from one end to the other, 'I used XXX home depot all thread which should be good for... " could be good enough. I f your plan was to use high strength bolts and end up substituting the cheep home depot stuff, that is another issue. As a Level 2, 'I built it to the kit instructions, using good building practices and materials..." is a good enough answer. Level 3 should be able to go a bit beyond that.

Where it gets more complicated is if you do a unique design or non standard building methods. I'm ok with you doing that (hey it is your rocket not mine) but I would want to see your justification for saying that the design / parts / methods are suitable for a level 3 sized rocket., specifically the one you plan on flying. Couple of examples;

• If you had a 3d printed bulkhead, I would want to be sure that you have a good justification in saying it is sufficient for the rocket.
• Bolt on fins is another thing that would have me ask how do you know they are suitable for the rocket.
• If you were planning on head end deployment, (again no problem with that), I would ask if you had done that before, if the answer is no i would start asking more questions...

You get the idea, oh and talk to your TAP / L3CC early about all of this

 

[sharkbait]

Dont over think it, but, as a Level 3 you should be able to 'justify' your design. If the answer is the Madcow UberMeshuga kit uses the same design (thicknesses of coupler, switch band 'all thread' u bolts etc. ) and it is routinely flown with similar motors / rocket weights, / rocket length (bending moment) etc. I would be good with that.

Relative to things like shear pins - type / location, I would be looking for a calculation and a ground test to verify. Same goes for how the shock cord loads are transmitted from one end to the other, 'I used XXX home depot all thread which should be good for... " could be good enough. I f your plan was to use high strength bolts and end up substituting the cheep home depot stuff, that is another issue. As a Level 2, 'I built it to the kit instructions, using good building practices and materials..." is a good enough answer. Level 3 should be able to go a bit beyond that.

Where it gets more complicated is if you do a unique design or non standard building methods. I'm ok with you doing that (hey it is your rocket not mine) but I would want to see your justification for saying that the design / parts / methods are suitable for a level 3 sized rocket., specifically the one you plan on flying. Couple of examples;

• If you had a 3d printed bulkhead, I would want to be sure that you have a good justification in saying it is sufficient for the rocket.
• Bolt on fins is another thing that would have me ask how do you know they are suitable for the rocket.
• If you were planning on head end deployment, (again no problem with that), I would ask if you had done that before, if the answer is no i would start asking more questions...

You get the idea, oh and talk to your TAP / L3CC early about all of this

Do you have to special order the Ubermeshuga kit, I don’t see it on the Madcow website

 

[boatgeek]

One challenge I see in all the re-use is that the rocket that works for a L2 cert with a J motor is going to be wildly different on an M. For example, a 4" fiberglass rocket with a 75mm MMT adapted down to 54mm is going to be a fairly sedate flight to a couple thousand feet on a J. On an M, that's going to be a screamer to 10K+. Even if you could make all that work, you may not be able to use the same chute, etc.

 

[Hobie1dog]

What rocket are you thinking about building?

 

[kramer714]

Do you have to special order the Ubermeshuga kit, I don’t see it on the Madcow website

kit bashed it from the Megatchatchke

 

[Handeman]

So my questions is, with all the "reuse", are you trying to cut costs? If money and finance are the primary issues, you might want to reconsider doing L3. Not that you can't do it "on the cheep" but I have to ask, what's the point? Is it just to get an L3 cert and not fly L3 any longer? If so, then by all means go for it. If you want to continue flying L3 after the cert, you should probably redo any analysis you had about the cost and what you can budget.

Generally speaking, L3 rockets run >$1000 each. Each launch is usually >$500.

If that is acceptable for your budget, continue on. If it's excessive, you might want to reconsider what you want to do. You can fly some pretty awesome flight in the L2 range at lower costs.

Of course, people tend to get more disposable income as time goes on, so a tight budget now, many not be so tight a few years from now.

I just recommend looking at the big picture.