never flown to L1 in one step?

[plano-doug]

At our launch this weekend we had several college students from a major engineering school in Cambridge do Level 1 certification flights. Some were successful, some were not, most didn't have a clue about the basics. I really don't care to hear "but the software says it's stable" ever again. They all were old enough and had current NAR cards. It was clear that they built the rockets themselves (also clear that they hadn't done much building before) and the ones that we signed off on were stable, deployed their chutes and recovered intact but I didn't real feel good about doing it. There's nothing in the rules that says you have to have prior experience. I think there should be but can't think of any way that could be done. What do you think?

Reading this, I get the impression that someone knowledgeable was engaged with these kids. Surely they didn't just start a club without a mentor of some sort, eh? Someone directed them to the sim software, the kits, the motors, etc, so they should have known about CP and CG. At the safety check table, if the flier couldn't point to the CP, my inclination would have been to deny the flight. If they could find the CP, then it's easy enough to find the CG, and show them that the margin was small or negative.

Ours is a teaching hobby, sort of like aviation or diving, where we often find ourselves giving quick lessons on various points of the game. In this case, if you have to reject someone's flight card, you try to mitigate it with a 2-minute lesson on CP-CG, then suggest they find some way to add nose weight, and bring it back later for re-check.

Also, if they show up for an L1 flight, then they presumably have someone lined up to observe and sign off. So someone else besides the SCO/RSO shoulda outghta been performing a pre-check prior to the rocket being presented at the safety check table, no?

I feel your frustration, Bill. And knowing myself, if I'd'a been in that situation, I probably would have been even more agitated than you were. But with the 20/20 hindsight afforded me at the relaxed comfort of my keyboard, it's a little easier for me to navigate thru the problem. Basically, I'm thinking the best way to have handled it would have been to conduct forty-eleven 2-minute lessons (or however many were required) at the expense of driving yourself crazy repeating the same lesson over and over, for each student coming up to the table

FWIW, when I got back into the hobby in late 1999, the hot rocketry forum of the day was rmr on usenet. I think I assimilated the CP/CG lesson in my first 20ns of login time there. That is, the fundamental concepts are abundantly available on the web.

So it seems reasonable to me to expect any HPR flier presenting at the safety check table to be able to address that topic. You don't want to hurt anyone's feelings, but it is necessary, and acceptable, for the SCO/RSO to scrutinize the flier's rocket. And, if you have to bounce someone, hopefully the 2-minute lesson on CP-CG (or motor retention or fin alignment, etc) helps restore their enthusiasm.

Doug

.

 

[plano-doug]

..."but the software says it's stable"...

This highlights an emerging potential problem area in engineering. When we first began doing simulations of our circuit board designs back in the 80's, it soon became apparent to me that electronic design automation tools (schematic capture, simulation, board layout, etc) were a double edged sword. Good engineers who mastered the tools could greatly improve their output, while many others simply found the tools a means to achieving ever more spectacular failures

In my present work environment, I see more and more emphasis placed on using simulation. But the results still need to be scrutinized to ensure adequate coverage. And the scrutiny step is where (I think) the failures most often occur. Not enough pointed questions are asked of the designer about how he/she ran the sims.

While it's clear that many of the great engineering accomplishments of the past 30 years could not have been done without the computer, it's still a must to know how the simulator works, to understand a little about what's under the hood. The user doesn't need to do all the analysis brute force by hand, but he/she needs to know enough about the simulating process to know where the tool works well, and where it's iffy.

And, in rocketry, that means knowing that the sim needs to be modified and run one last time with actual measured weights and CG's prior to pushing the button.

Doug

.

 

[billspad]

This highlights an emerging potential problem area in engineering. When we first began doing simulations of our circuit board designs back in the 80's, it soon became apparent to me that electronic design automation tools (schematic capture, simulation, board layout, etc) were a double edged sword. Good engineers who mastered the tools could greatly improve their output, while many others simply found the tools a means to achieving ever more spectacular failures

In my present work environment, I see more and more emphasis placed on using simulation. But the results still need to be scrutinized to ensure adequate coverage. And the scrutiny step is where (I think) the failures most often occur. Not enough pointed questions are asked of the designer about how he/she ran the sims.

While it's clear that many of the great engineering accomplishments of the past 30 years could not have been done without the computer, it's still a must to know how the simulator works. The user doesn't need to do all the analysis brute force by hand, but he/she needs to know enough about the simulating process to know where the tool works well, and where it's iffy.

And, in rocketry, that means knowing that the sim needs to be modified and run one last time with actual measured weights and CG's prior to pushing the button.

Doug

.

Sadly, the over reliance on computers begins at an early age. I remember a post on the TARC mailing list where the flyer said the sim said the rocket would go to 900 feet and the altimeter read 800 feet. He wanted to know what was wrong with his altimeter.

By the way, referring to your previous post, I wasn't really agitated. I'm pretty mellow (although I have two employees who would say otherwise). On the other hand Kenn was agitated. Of course there's a back story to all this. A few weeks ago we were told to expect 30 certification flights. That created somewhat of a panic since that's significantly more than we usually have. Then a couple of days before the launch it was 20. I think there were finally around 10 or so that actually flew. That was somewhat aggravating but not really surprising. If there were 30 of the same of what we saw, I may have become agitated.

 

[ClusterNut]

I was a witness for one attempt. His flight went off well except for the "MIT jiggle". It was pretty minor though. All in all I thought they were fun to have there despite some glitches.

I have to agree with the sentiment that although these were all bright and enthusiastic people, it seems a bit of over-reach to expect them to jump from essentially the textbook to a high power launch. As was pointed out, sims are great but it really takes some experience to have a feel for when the sim is realistic or properly constructed. Actually constructing a rocket requires some practice with the various build techniques. Most of us started with an Estes kit and grew into the hobby by building and flying larger and more complex rockets over time. It helps us look at a sim and scratch our heads when it looks a little odd. IMHO the students, who did really well under the circumstances, would have benefited by a more systematic approach like that taken by NARtrek. They skipped a lot of cool stuff like staging and clustering. I hope they continue on with their work and maybe go back and try some of these other aspects of rocketry. Could be seeing some interesting designs from these folks.

 

[CarVac]

....except that design, and implementation, are two very different things. If you're building a kit and following the instructions, odds are you're going to be successful.

If you're building a kit and deviating, the opportunity for problems increases.

If you're scratch building and don't understand the ramifications of things (such as adding fiberglass to the rear, or that weights in the sim software are estimates and don't necessarily match reality) you can run into problems.

It's the little things that most learn via experience that matter the most. This is why I'd encourage every student team to have an actively involved mentor, to help them along.

-Kevin

I seem to be chronically misunderstood in this thread.

1. Yes, if you build a kit and follow instructions faithfully, you're likely to be successful.
2. If you build a kit and modify it, there are going to be problems.
3. If you scratch-build a rocket, there are going to be fewer problems, simulation-wise, than a modified kit.

I see lots of trading of simulation files on TRF, and that scares me because I'm afraid someone is going to accidentally use a sim file made for another rocket for their own without modification (whether accidentally selecting the wrong one, or forgetting to modify it). That's never going to be a problem with a scratch built rocket.

Secondly, I noted that there should be discussion involved, though I omitted the "with an experienced advisor" portion because I thought that was obvious. Evidently it wasn't.

Spending weeks thinking about building a bridge does not give me the qualification to build one.

That's comparing apples to the International Space Station. A few weeks spent thinking about the design of a high power rocket is most certainly enough time to create a valid design to L1 cert with. Bridges have probably 3 or 4 orders of magnitude more complexity than the typical L1 rocket.

 

[chadrog]

That's comparing apples to the International Space Station. A few weeks spent thinking about the design of a high power rocket is most certainly enough time to create a valid design to L1 cert with. Bridges have probably 3 or 4 orders of magnitude more complexity than the typical L1 rocket.

No, it's comparing someone who knows nothing about a subject with someone else who knows nothing about a subject - apples to apples.

 

[CarVac]

No, it's comparing someone who knows nothing about a subject with someone else who knows nothing about a subject - apples to apples.

Even if I know how to build a bridge that doesn't make me capable of it. That takes much more than a single human is capable of doing alone.

On the other hand, an L1 rocket is by definition done alone. The scope is so incredibly different that I must protest your comparing L1 certification with the singlehanded complete design and construction of a bridge.

 

[chadrog]

Even if I know how to build a bridge that doesn't make me capable of it. That takes much more than a single human is capable of doing alone.

On the other hand, an L1 rocket is by definition done alone. The scope is so incredibly different that I must protest your comparing L1 certification with the singlehanded complete design and construction of a bridge.

If you try to look at it a bit less literally you might understand.

 

[CarVac]

If you try to look at it a bit less literally you might understand.

If I look at it less literally, you might as well have said "Even if you spend weeks thinking about it, that doesn't ensure that your L1 cert will be successful" and I wouldn't have had a problem.

 

[troj]

Even if I know how to build a bridge that doesn't make me capable of it. That takes much more than a single human is capable of doing alone.

On the other hand, an L1 rocket is by definition done alone. The scope is so incredibly different that I must protest your comparing L1 certification with the singlehanded complete design and construction of a bridge.

You're missing his point entirely.

You're entering it assuming that, based on study, someone knows how to build a rocket. That's not necessarily the case, as has been demonstrated by numerous examples over the years. This is especially true of someone with zero model building experience.

This is why programs such as TARC, SLI and USLI are dependent upon experienced mentors -- to provide those nuances that come with experience and often aren't obvious when just reading up on the science of it all.

-Kevin

PS: You realize you're doing a wonderful job of demonstrating an engineer's ability to miss the forest for the trees?

 

[chadrog]

If I look at it less literally, you might as well have said "Even if you spend weeks thinking about it, that doesn't ensure that your L1 cert will be successful" and I wouldn't have had a problem.

 

[CarVac]

To clear this all up:

It's probably ok for someone to go straight to L1 if they spend a lot of time thinking on it AND they consult, and follow the advice of, an experienced mentor during design and construction.

There are cases where that wasn't necessary, but that's very unlikely unless the person had alternatives to the mentorship (such as reading large quantities of TRF archives).

If there isn't mentorship or a suitable substitute, then even weeks of thinking about it will not necessarily discover every contingency.

 

[JoeG]

We too, have had this problem of people showing up to do a certification flight when their knowledge base was.............. less than optimal.

First of all, there are some of you who fly with us on this forum. Don't take this personally.....unless the shoe fits. I am not speaking to or of anyone in particular and have no one in particular in mind. This is just a general rant.

I agree with the sentiment "the more the merrier." What I don't agree with is myself or one of our other club members getting tied up for hours at a launch helping someone certify by answering questions they should already know the answer to, loaning equipment that they should have, showing how to instal an ignitor, setting an altimeter, drilling holes for shear pins, calculating ejection charges or times, etc. We came to fly rockets too. We have already done our certification flights. We don't need to do them again.

Our Board of Directors finally sat down and wrote out some of our own special rules for certification. You can find them here. The realization for the need of these came to our attention when a Level 2 rocket came to the RSO table with the altimeter beeping merrily away and the ignitor already installed in the motor.

https://www.ohioaerospace.net/docs/Ohio_Aero_Modeling_Consortium_Certification_Rules.pdf

They may seem harsh at first but we just want people to know what they are doing and make it safe for everyone. We still have a lot of folks showing up to certify. They seem to be a little more knowledgeable these days though.

Remember, once the member gets his L2 cert s/he is free to fly a full L. I want to feel good about that not have a sinking sensation in my stomach.

 

[GregGleason]

... Our Board of Directors finally sat down and wrote out some of our own special rules for certification. You can find them here. The realization for the need of these came to our attention when a Level 2 rocket came to the RSO table with the altimeter beeping merrily away and the ignitor already installed in the motor.

https://www.ohioaerospace.net/docs/Ohio_Aero_Modeling_Consortium_Certification_Rules.pdf

They may seem harsh at first but we just want people to know what they are doing and make it safe for everyone. We still have a lot of folks showing up to certify. They seem to be a little more knowledgeable these days though...

That's a pretty good document. Let's everyone know ahead of time the level of expectations the club has for those seeking cert flights.

I might suggest a similar document to the club I belong to.

Greg

 

[dward]

We too, have had this problem of people showing up to do a certification flight when their knowledge base was.............. less than optimal.

First of all, there are some of you who fly with us on this forum. Don't take this personally.....unless the shoe fits. I am not speaking to or of anyone in particular and have no one in particular in mind. This is just a general rant.

I agree with the sentiment "the more the merrier." What I don't agree with is myself or one of our other club members getting tied up for hours at a launch helping someone certify by answering questions they should already know the answer to, loaning equipment that they should have, showing how to instal an ignitor, setting an altimeter, drilling holes for shear pins, calculating ejection charges or times, etc. We came to fly rockets too. We have already done our certification flights. We don't need to do them again.

Our Board of Directors finally sat down and wrote out some of our own special rules for certification. You can find them here. The realization for the need of these came to our attention when a Level 2 rocket came to the RSO table with the altimeter beeping merrily away and the ignitor already installed in the motor.

https://www.ohioaerospace.net/docs/Ohio_Aero_Modeling_Consortium_Certification_Rules.pdf

They may seem harsh at first but we just want people to know what they are doing and make it safe for everyone. We still have a lot of folks showing up to certify. They seem to be a little more knowledgeable these days though.

Remember, once the member gets his L2 cert s/he is free to fly a full L. I want to feel good about that not have a sinking sensation in my stomach.

Is there a reason OpenRocket is missing from the list of simulation programs?

 

[JoeG]

Is there a reason OpenRocket is missing from the list of simulation programs?

No reason other than omission. I would accept simulations from open rocket. A call ahead would confirm that.

We are not trying to be hard to get along with. Just want to make sure that the folks doing the certifying know what they are doing. There may be other programs or methods out there that are just as valid.

 

[DizWolf]

We have two college clubs who fly with us. Lots of fun having them, and some great flights. Kinda shocked this is such an issue all over.

My first club launch I put up a few G's and then asked if I could do an L1. Before that day I had no idea what to expect. Not quite sure what an RSO or LCO was, or customary procedures like flight cards or the like. I did have quite a bit of prep/knowledge of my rocket. I'm glad I joined a welcoming club, and that Bill Clune is an awesome and helpful guy (as is everyone I've met in Potter)

 

[KennB]

We have two college clubs who fly with us. Lots of fun having them, and some great flights. Kinda shocked this is such an issue all over.

I haven't been in too much contact with this student group (as Bill said, I was agitated) but I wonder how many of them we'll see again. I hope we get some regulars out of this and that they'll take a step back, get the basics down and grow from there. It sounds like you've got a good, ongoing relationship going with your college clubs; that's good. I'm afraid most of the students that visited us are just involved in it for the semester so they can say they did this and they'll be off to the fencing club in the next term.

 

[DizWolf]

I'm wondering if a short "this is how you build/load/prep a rocket" and " this is what's expected at a launch" pamphlet would be useful for college clubs/new HPR people

 

[grouch]

I'm wondering if a short "this is how you build/load/prep a rocket" and " this is what's expected at a launch" pamphlet would be useful for college clubs/new HPR people

Or give them a program called Open Launch that allows them to "engineer" their own launch by picking from an assorted selection of launching behaviors. Some of these behaviors would be best practices, some would be questionable, and some would be down right dangerous but it would allow them to custom pick their own launch experience and the simulator would predict if they will be successful or not. That way they can be a part of the design process from start to finish.

 

[JoeG]

I'm wondering if a short "this is how you build/load/prep a rocket" and " this is what's expected at a launch" pamphlet would be useful for college clubs/new HPR people

We are in the process of preparing a "welcome" packet for new members or those who are attending a launch for the first time. Not necessarily just those who are attempting to certify. It is in the planning stages right now but we hope to offer information to make a stranger feel more at home. Kind of a FAQ thing maybe.

 

[H_Rocket]

Our Board of Directors finally sat down and wrote out some of our own special rules for certification. You can find them here. The realization for the need of these came to our attention when a Level 2 rocket came to the RSO table with the altimeter beeping merrily away and the ignitor already installed in the motor.

https://www.ohioaerospace.net/docs/Ohio_Aero_Modeling_Consortium_Certification_Rules.pdf

They may seem harsh at first but we just want people to know what they are doing and make it safe for everyone.

Harsh, heck no. This should be the basis (IMHO) for the national organizations to look at in making HPR certification a real basis for safety. We have made HPR certification a right rather than a privilege. It should be a challenge and a journey, not a ticket you get punched.

1. Yes, if you build a kit and follow instructions faithfully, you're likely to be successful.
2. If you build a kit and modify it, there are going to be problems.
3. If you scratch-build a rocket, there are going to be fewer problems, simulation-wise, than a modified kit.

That makes no sense at all - please explain why you would encounter more problems in a simulation with a kit-bash than a scratch build.

 

[green dragon]

They are obvious smart or they would not have been accepted to college, but being typical students, it appeared they relied a bit too much on simulations instead of putting a lot of thought into building their rockets. What was mildly amusing that about half of the rockets were fiberglassed on the aft end only. I'm pretty sure that the students did their stability calculations without considering the extra aft weight of the fiberglass. When asked about the Cg-Cp relationship, they estimated about 2 calibers stability, but the RSO balance test showed it had been an overestimate. The ones with ~1 caliber stability had noticeable tail wiggles on the way up. I'm sure they learned that building and flying is different than idealized simulations.

Bob

This itself shows the ' not in the real world' overtones.... a L1 bird should NEVER need glass, most L2 birds do not need glass, and those of us flying HPR since the beginning never had to glass anything, just well built and keep it together.
Was there a reason there was fiberglass on these rockets ? if so, why ? were they high performance and needed the reinforcment ? if LEARNING was the key ingredient, then why not start simple , even if starting at Level 1 , then KISS principle should be obvious.
I agree with posters' comments re: starting at G motors or similar, not much difference sizewise from most G powered birds, to most entry level L1 H powered models, or even low I birds.
Not saying students should fly Estes for years before HPR or MPR, but jumping in with the biggest and baddest might not be the best... like race drivers starting with Top Fuel or NASCAR ? never happens. should not happen in rocketry, either.

leaves soapbox

 

[CarVac]

....except that design, and implementation, are two very different things. If you're building a kit and following the instructions, odds are you're going to be successful.

If you're building a kit and deviating, the opportunity for problems increases.

If you're scratch building and don't understand the ramifications of things (such as adding fiberglass to the rear, or that weights in the sim software are estimates and don't necessarily match reality) you can run into problems.

It's the little things that most learn via experience that matter the most. This is why I'd encourage every student team to have an actively involved mentor, to help them along.

-Kevin

Spending weeks thinking about building a bridge does not give me the qualification to build one.

Harsh, heck no. This should be the basis (IMHO) for the national organizations to look at in making HPR certification a real basis for safety. We have made HPR certification a right rather than a privilege. It should be a challenge and a journey, not a ticket you get punched.




That makes no sense at all - please explain why you would encounter more problems in a simulation with a kit-bash than a scratch build.

I think a scratch-builder is more likely to model every part of their rocket rather than assuming that part of a manufacturer's provided file is accurate.

This is only in the case that the person is modifying an existing file, not making their own file. Does this make ssense?

 

[green dragon]

Guess I'm missing something here about all the simulations, and making or modifying a file, etc - YES, I use the programs to 'test fly' stuff myself, but - we're talking INTRO level, level one flights here - NOT oddball designs or high performance flights.
3fnc with maybe some dual deploy thrown in - it's an overgrown model rocket - and SHOULD be easily accomplished by someone with average modelling or craftsmanship skills.
I see no reason someone going for L1 should be building anything other than a simple 'rocket looking' rocket - probabally from a kit, although scratchbuilding is fine, I've seen 13 yr olds scratchbuild midpower / low HPR level birds with success.
And an experienced RSO should be able to eyeball the CP on anything with normal geometry, and CG is a matter of holding it in your hand and balancing it - how complicated does this have to be ?
Should a new flyer understand CG/CP relationships, etc - I think yes, but how many of us knew that when we started in model rockets ? it's a learning PROCESS, as you go, on the job training.

 

[cerving]

I think the mentor should have acted as a pro-forma RSO in terms of the safety and prep issues. It would have been relatively simple to have the rockets checked by the mentor first before taking it to the club's RSO table. Better yet, the mentor should have had their designs submitted to him/her prior to construction so that issues such as the aforementioned inadequate fins could have been rectified.

The RSO has the ultimate responsibility for the safety of the range, so they have to be able to say "No, you cannot fly this rocket". It's probably not done enough... they don't want to discourage newbies or alienate members, but sometimes a manager has to assert their authority for the betterment of the team.

 

[H_Rocket]

I think a scratch-builder is more likely to model every part of their rocket rather than assuming that part of a manufacturer's provided file is accurate.

This is only in the case that the person is modifying an existing file, not making their own file. Does this make ssense?

Not really as in the design part of a simulation the only things that matter are the airframe profile and mass. If those are correct in the simulation, it will be as accurate as can be if EVERY other variable (launch conditions) is dialed in right. One of the most accurate simulation packages is RAS Aero and at no point do you need to enter couplers, parachutes, centering rings, etc. Airflow does not care what is under the skin.

 

[blackbrandt]

Guess I'm missing something here about all the simulations, and making or modifying a file, etc - YES, I use the programs to 'test fly' stuff myself, but - we're talking INTRO level, level one flights here - NOT oddball designs or high performance flights.
3fnc with maybe some dual deploy thrown in - it's an overgrown model rocket - and SHOULD be easily accomplished by someone with average modelling or craftsmanship skills.
I see no reason someone going for L1 should be building anything other than a simple 'rocket looking' rocket - probabally from a kit, although scratchbuilding is fine, I've seen 13 yr olds scratchbuild midpower / low HPR level birds with success.
And an experienced RSO should be able to eyeball the CP on anything with normal geometry, and CG is a matter of holding it in your hand and balancing it - how complicated does this have to be ?
Should a new flyer understand CG/CP relationships, etc - I think yes, but how many of us knew that when we started in model rockets ? it's a learning PROCESS, as you go, on the job training.

Heck, I just turned 15 and I fly H motors without an issue. I guess it comes from my building of rockets like anti-tank rounds...


Matt

 

[chadrog]

Heck, I just turned 15 and I fly H motors without an issue. I guess it comes from my building of rockets like anti-tank rounds...


Matt

Probably not something you should publicize.

 

[Rex R]

you know...when you think of it, from a structural PoV barns, covered bridges, and the ISS do have a lot in common (google trusses).
Rex