Minimum diameter level 1 rocket questions

[FredA]

Kurt - grind your axe elsewhere.
Never said anything but suggesting people to fly what they want to fly and to take advantage of the org's process to learn how to do that best.
Stop at L1 or whatever floats your boat.

The low and slow bit was CLEARLY LABELED with IMHO and I stand behind what I said - I'm sorry you can't respect that people might have opinions outside if yours.

 

[David Schwantz]

All my MD rockets get 2 wraps of aluminum tape around aft end for retention.

 

[rcktnut]

A few years back, it was recommended almost exclusively to K.I.S.S. for a cert flight. Get your cert then go nuts if you wish. Simple flights can fail too, but if really wanting to achieve your cert why not do a flight with a high probability of success?

IMHO the low-and-slow cert is for "punch my ticket" people.
It represents a small corner-case of rocketry and really only demonstrates risk avoidance.

In my opinion, just the way it should be for an L1 cert. If someone came up to me with what the OP wants to do with his L1 cert flight to certify him, I would say unless you use a smaller motor, keeping the entire flight in sight, find someone else. L1 cert with electronics OK, but not out of sight.

 

[FredA]

Prefects / TAPS are NOT PERMITTED to deny a safe flight because they don't like it.
NAR certifiers shouldn't do it either, but I'm unsure of NAR rules.
Totally uncool.

 

[bjphoenix]

I'm not certified, but working on it. I view it differently.

It's your choice and if that's the way you want to do it you can certainly go that way. I think your chance of success is less, going low and slow with motor eject is almost a slam dunk but as such it is not a big challenge. The other issue is a high altitude L1 can't be launched just anywhere, more launch sites can handle an H motor to 1500', but you know what launch sites are available to you.

 

[TheTank]

Complete your cert however you want to do it. Ask questions, find a mentor. Test things while flying mid power. Doing a low and slow flight to get your cert doesnt advance your skills and knowledge anymore than a mid power flight so make your journey your own. If you fail, oh well. Dust yourself off, learn from your mistakes and try it again!

 

[boatgeek]

Prefects / TAPS are NOT PERMITTED to deny a safe flight because they don't like it.
NAR certifiers shouldn't do it either, but I'm unsure of NAR rules.
Totally uncool.

Came here to say this. Unless there’s a safety reason, witnesses should not deny a flight. With the possible exception of a Junior L1 since that expects more guidance from the mentor.

 

[Steve Shannon]

Prefects / TAPS are NOT PERMITTED to deny a safe flight because they don't like it.
NAR certifiers shouldn't do it either, but I'm unsure of NAR rules.
Totally uncool.

I completely agree with this as both a TAP and an L3CC. Certification rules establish the boundaries for certification flights; as a TAP or L3CC I don’t have the authority to require more than the rules require. However, as a TAP or L3CC I am expected to participate in improving the certification procedures for the entire organization when they need it.

 

[Rocketjunkie]

The point of the cert is to denote proficiency in the type of flying that a person will do once certified.

We'll just have to disagree, I guess.

Make sure your certifier is OK with this! This is critical!! You must get it back! It is very hard to see a 29 mm rocket above 3000' My eyes are no longer as good as they once were.

 

[Sooner Boomer]

All my MD rockets get 2 wraps of aluminum tape around aft end for retention.

Please explain. Wraps around the motor case to make it fit snugly? Around the case and body tube both? How would this clear the fins?

 

[loopy]

OR - to put it another way - USE the cert process and the mentors provided within to gain the proficiency needed for your desired style of flying.
As I've often said - the L3 "gateway to unlimited flying" is also the last [required] chance for education.
But the whole process, if used, can be a great educational experience.
Learn to fly what you want to fly.

IMHO the low-and-slow cert is for "punch my ticket" people.
It represents a small corner-case of rocketry and really only demonstrates risk avoidance.

I would disagree with the "punch my ticket" portion of this. I didn't always go low and slow, but chose combinations with a high probability of success, as have most of those I know that have certified. Wanting to keep the rocket in sight helps to know that everything you did worked as planned so you have confidence in it for future flights that may be out of visual range. Being able to see how the rocket performs in that setup educates you by reinforcing that you've done it right. It's not "punch my ticket", it's "validate my process", IMHO.

Bottom line, there's no "wrong" way.

 

[Sooner Boomer]

Liam,
You've gotten a lot of responses. Some address your question. Some did not. Some replies were a little less than gentle in suggesting you try a different method.

Let me bore you a bit with my own "quest for cert". I hooked up with the local NAR/Tripoli guys in about 2000. I jumped in with both feet. I bought a bunch of tubing, nosecones, fin stock, etc. Plus an Aerotech 29/180 case to certify L1 with. I built a nice rocket with a 54mm body tube and 29mm mount. The body tube used 1/2 of a "stick" of PML phenolic. I lost my job at the time, then a bunch of life happened. I flew the rocket a lot, G80's G55s, bunches of single use and reloads. I took me over 20 years to finally load that case and make my L1 cert attempt. I still like to fly that rocket. I know from flying that rocket that, anything going over 2000 feet (about where a G80 sends it), it's going out of sight and will need a tracker.

My advice would be to have fun. If you really think you need to go for orbital altitude for your L1 cert flight, go for it! Just be aware of the risks. I'd suggest a rocket with a little bit less narrow of a performance range that could be down-powered as a park flyer, or ramped up when you have wide open spaces. We're pulling for you!

 

[beeblebrox]

I feel the same way about it.

A cert is just a piece of paper and a pin for your drawer ( or for your young granddaughters )

Why build and fly a rocket to fly low and slow just one time simply to get a certification and then never fly that rocket ever again because you're into speed and altitude ?

High failure rate for minimum diameter rockets. You have to bring it back for inspection after the flight, if you lose it, it fails, even if it functioned properly.

If ripping flight is your cup -o- tea then why not certify that way ?

Build a rocket that would be a nice ripper with a J-Motor, put a small mount for an H in it for cert flight...problem solved.

As @SolarYellow said, that same rocket can fly low and slow on a smaller motor until you've developed your techniques ( dual deployment and tracking ).

And if it takes more than one attempt, so be it -- you can buy as many L1 motors as you need until you get certified.

And the same is true when it comes time to certify L2.

Just my $0.02 ...

-- kjh

 

[beeblebrox]

Remember that even NASA built smaller rockets to test stuff before sending man to the moon in 1969. Using computers that pale in comparison to your smart phone...

 

[SolarYellow]

I didn't always go low and slow, but chose combinations with a high probability of success, as have most of those I know that have certified. Wanting to keep the rocket in sight helps to know that everything you did worked as planned so you have confidence in it for future flights that may be out of visual range. Being able to see how the rocket performs in that setup educates you by reinforcing that you've done it right. It's not "punch my ticket", it's "validate my process", IMHO.

That is exactly my plan, except that the middle two sentences are going to be LPR/MPR, before the cert flight rather than during/after. Out of sight will be high MPR and then low HPR. It will be a ripper on an H or an I, but I'll do all the process validation with much smaller, cheaper motors.

 

[loopy]

That is exactly my plan, except that the middle two sentences are going to be LPR/MPR, before the cert flight rather than during/after. Out of sight will be high MPR and then low HPR. It will be a ripper on an H or an I, but I'll do all the process validation with much smaller, cheaper motors.

That works too. It's personal preference whether or not you want to see the apogee event or not and be able to track the rocket visually on descent. Personally, I like to see my rockets come down so I know where to go to get them. Some don't. lol

 

[David Schwantz]

Slide motor in,wrap tape around motor and after endof rocket, crimp tape around thrust ring. Cut slots for fins if needed.

 

[Tractionengines]

I'll chime in 1 thing here, to anyone thinking if doing this type of flight (minimum diameter) for a certification, [or any certification flight for that matter].

DON'T BE A STRANGER.

If you have a known history of MD rockets with G80's "vaporizing" off the pad, and MD Ultralights with electronic deployment & RF trackers for G12 "Long burn" flights; and you come walking back with them in good shape after recovery, your SIM's match your actual apogee, etc...GREAT.
You walk up with a H135, or a H13, loaded up it's a "typical flight" for you, just a few more N-Sec. The RSO, LCO, Prefect, etc. know you, and are likely to (should) let you make the flight.

On the other hand: walking up "out of the blue" with that same flight you better be ready to answer lots of questions, and justify that you know what your doing, and your sim's are valid, etc. So the officials feel comfortable that you will recover in the acceptable area, have a good recovery, and not bust the waiver... if they are not sure of that... You could be putting their flying field, or waiver, in jeopardy, and they have every right to not allow the flight.

Just my $.02, YMMV.

 

[Art Upton]

That works too. It's personal preference whether or not you want to see the apogee event or not and be able to track the rocket visually on descent. Personally, I like to see my rockets come down so I know where to go to get them. Some don't. lol

Yea, that 3-1/2 mile Supersonic flight of my 4" rocket to the left in my Avatar even in the nice Skies over the Desert; I could not see it all the way up. It had GPS on it and Greg from Big Red Bee was reading off the up and down Altitudes in meters behind me, so I knew things were OK and so did the LCO listening to him who repeated some of them on the PA.

But the guy next to me saw it the whole time as when I mentioned not seeing it pointed to it on the way down, "I've seen it the whole time." I still have it, maybe some day I can fly it on a K motor where I can see it the whole way. Anyway it was one of the Kewlist flights I ever did, and it was not my L3 Cert, it was like the 3rd M motor I had flown.

I flew my Bruiser EXP-4 to 10K for my Cert flight and saw it the whole way, until it landed in a 1/2 mile square corn field and the RDF tracker came in handy. Doing triangulation on a napkin going around the corn, we figgured where it must be and 6 of us walked into the cornfield till one of us ran into the shock cord!

That L3 Cert and corn field was at MWP 2004.

 

[thzero]

Build some MPR rockets first. B70 and BT80 tubes can make fine dual deployment on Fs and Gs.

 

[bjphoenix]

Make sure your certifier is OK with this! This is critical!! You must get it back! It is very hard to see a 29 mm rocket above 3000' My eyes are no longer as good as they once were.

I don't think you can count on seeing it above 1000'.

High failure rate for minimum diameter rockets. You have to bring it back for inspection after the flight, if you lose it, it fails, even if it functioned properly.

This is an important consideration. If you go to high altitude and the rocket lands half a mile away in unknown direction it might take awhile to go there and find it (depends on conditions at your launch site). Be sure your certifier will still be around when you return.

 

[SolarYellow]

If you've successfully used your GPS tracker at 800', 1500', 2500', whatever your apogee is with a G76 or G80, etc., you'll probably be ready when you put that baby H in it.

 

[-Slick-Ice]

There is a big difference between doing your L1 flight with something that might have a potentially lower success rate and an unsafe flight. But if they are going to need to spend 4 hours recovering their rocket they tried to send to the moon I don't want to be the witness for it.
The last L1 certification flight I watched I don't think was minimum diameter but it used more of the ceiling than any flight I have seen this year. With a H130 costing almost the same as a G80 now I wouldn't even suggest test flights as a mid-power.
It also makes no sense to require someone build a rocket specifically for their L1 certification flight if they are never going to fly it again.
The 3" IRIS I used for my L1 has never seen an "H" motor again.

 

[Tractionengines]

With a H130 costing almost the same as a G80 now I wouldn't even suggest test flights as a mid-power.

Same logic I have for L2 vs L1...

Motor. DMS I500T vs J425R
Impulse . 620 nSec 676
Avg. Thrust. 500. N. 425
Max. Thrust. 613. N. 452
Burn time. 1.3. Sec 1.6
Cost. 96.99 $ 102.99
Apogegee difference +~100ft

For $6 more and +~100 ft... If you want to do a test flight OK, great. It's an almost Identical flight, just on both sides of the L1/L2 line on paper. (Manufacting variance could allow them to overlap.) The only REAL different is the color of the exhaust.

If you fly L1 a while and have flown the I500T... then there should be no more stress, or anxiety, for the J425R, because you've done the same flight.

 

[watheyak]

I think the glaring issue here is that a fiberglass DD rocket is too heavy for an I65.

 

[Neutronium95]

I think the glaring issue here is that a fiberglass DD rocket is too heavy for an I65.

I don't see how that's possible. The I65 has a pretty healthy initial thrust spike of about 160N at ignition. People have been flying 4" cardboard rockets on them for years.

I grabbed an old Mach 2 sim, and with a 6 foot rail the I65 has a rail exit speed of 62 ft/s and a maximum acceleration of 10g. That's certainly a lot less than you'll get with pretty much any other motor, but still well within a safe flight envelope.

 

[Art Upton]

I think the glaring issue here is that a fiberglass DD rocket is too heavy for an I65.

Yea, If you build a LOC Caliber ISP light at 3 pounds or so, it is just about right. I still have two more flyable I65s. I also have a collector type old school I65 that has the part Aluminum casing but it's too old to fly at least for me.

I have seen folks with a LOC EZ-I with added ebays/DD and other weight from over building and it was not pretty. The EZ-I was designed back when I65's had motor deploy. When they came back they also had it for awhile, but quickly made them plugged; meaning issues were happening. I have one of those but would fly it plugged not use the motor deploy.

Last one I flew in my LOC ISP I had Altimeter for apogee only deploy located in the payload, and JL Chute Release for the main.

 

[Art Upton]

1. In OpenRocket my current simulation is being designed with a stability caliber of 1. This rocket will have an apogee of around 8000 ft with a max velocity of around mach 0.80. Would I be safe with a stability caliber of 1 or should I aim for something more than 1, and if so, what would be a good number to target?

This is an interesting question we should also ask under the OpenRocket sub-forum.

The OpenRocket Sim of the 4" rocket in my Avatar starts out with a Caliber of .865.
However when graphed with the launch, and watching CP vs Mach number you can see it change below.
Caliber is in Blue on the plot, CP location in yellow. And yes it flew straight and true.

When I built this I was using RockSim and RASaero on a different computer long removed. Each element of the build tree was weigh and over-ridden just for that sub-assembly. I found the RTK file in a backup and moved it over to OR last week.

The rocket flew higher then the sim. I need to ask questions on how to back-sim this to make it match what the two ARTS-1 flight computers produced. I knew how to do it in RockSim but not OR. Only way I can find to change CD is via the paint smoothness in the build portion.

Edit: this can also be flown Min Diameter. The motor mount is not glued in, it is only screwed in at the centering ring with three screws, one each in-between the fins. Think of it simply as a motor adapter.

 

[Peter Kay]

Glad to see I'm not the only one not interested in a Slow and Low flight on an expensive Rocket and Motor. Life is short, and I've already surpassed 2,000 feet many times with Mid Power. My L1 attempt will be with a 4.0 LOC Magg but only because I wanted a fat Rocket for a novelty and plan to only launch it on F-67s after my L1 Cert flight. I did 2,460 feet for under $15 with this Rocket and it was visible the whole time (but only to 2 of us to be fair) , hard to spend hundreds to go lower than that.

 

[Liam Steele]

Hello, I just wanted to close this thread. I decided to go with a more reliable approach for my level 1 certification and built a Madcow Rocketry Super DX3. On 7/27 I successfully completed my level 1 certification with that rocket on an AeroTech I175WS-13A rocket motor. Thank you to everyone for your help and advice, and I will return to this project in the near future.