TARC Resources

[kramer714]

For ROCTOBER, the ROC October Launch at Lucerne Dry Lakebed in California, I was thinking of putting together a few things that may be helpful for TARC teams. I just wanted to ‘feel out the waters’ to see if this sounds helpful. Here are my thoughts,

1) Engine test stand.
A simple stand for 24/29mm motors. The test stand would be able to monitor the load/vs time plus track the exact time of the delay relative to the thrust. My plan it to get a few (maybe 5?) motors of the EXACT same kind, try to get ones from different lots or date codes and run the test. Let the teams get a feel for the statistical variation of the motors thrust and delay. Any motor manufactures willing to support his test by supplying motors?

2) Test Flight.
Take a TARC representative rocket kit (about the same size and weight as a 2011 TARC rocket). Have all the information available ahead of time so a detailed ROCSIM model can be developed by the teams. Have good launch site data available (exact altitude, barometric pressure, winds launch rod length, etc), and let them try to predict the altitude. Launch the SAME rocket 3-5 times maybe using the same motor a few flights and then change the motor for another flight.

3) Chute.
Using a rocket with a payload bay, launch a 15" parachute with a weight on it that is similar to the weight of a TARC rocket. Try to go to a TARC representative altitude. Using the altimeter in the rocket and a camera try to determine the exact time it takes for the chute to land from a known altitude. The weight could be low drag (I was thinking a Racquetball filled with sand to get to the right weight. Again, using whatever calculations or modeling, try to predict the time. Maybe launch different style 15" parachutes.

Any other thoughts? Any Southern California TARC teams that may be interested?

 

[RandyT0001]

Isn't the general idea behind TARC that the various TARC teams do steps 2 and 3 on their own. They design, develop and simulate the rocket using software (ROCSIM, Open Rocket, etc) under various flight conditions and then once they are satisfied with their designed rocket they build it and test fly it several times? If you (or another individual not part of the TARC team) presents a 'representative rocket' (and the only way one could present a representative rocket is if were simulated and built by an outsider) or predetermined recovery rates for parachutes for them to copy as input into a rocket flight simulation program seems to me to be not within the spirit and rules of the contest. Let them do the brainstorming and building; the mentors and advisors provide guidance and encouragement.

 

[bandman444]

I agree with randy.

I would much rather see you show the teams a HPR and get them excited about the hobby!

I started my team last year as a Sophmore and now my team is planning for their second year and are having a blast!!! They watched me as I built my Jr. Level 1 cert (actually I certified last ROCtober!) and so i would like someone show other teams that side of the hobby.

I will be away for ROCtober this year and being my teams president means I HAVE to be at everyone of their launches (I am the only one with more than 1 year of experience and knows what their doing)

But my team will be going to ROCSTOCK in Nov. if you wanted to hook up

 

[ScrapDaddy]

I was/and still am intrested in TARC, I believe the 2011 rules lifted the impulse limit, but the rocket must still be under (2lb?)

SD

 

[kramer714]

The goal isn't to do the work for them in steps 2-3 but to let them learn 'the scientific method' of analysis then experimentation followed by revised analysis. The representative rocket isn't a TARC competitor per se but something of similar size so they can get a feel for Rocsim analysis vs real results.

Most kids think that Rocsim gives them the answer, my thought is to let them learn how Rocsim is a tool, but testing is needed to use the tool effectively (this lesson is lost on many of the right out of college engineers I hire at the 'day job'). After seeing some real world results, it may give them a better feel for what they need to do on their design / testing.

Same idea on the chute, how you pack the chute can change the decent times dramatically in terms of TARC scores, plus getting a feel for how different 15" chutes can be. Again, my goal wasn't to do the work for them but to help them understand the variables as they go forward in their effort.

Are there better things / activities / resources that I could do at the ROCtober launch to support TARC?

P.S. Having demo launches of HPR shouldn't be that hard at Roctober. Bandman, if you need someone at Roctober to help your team launch I'm sure we can do that too.

 

[RandyT0001]

The goal isn't to do the work for them in steps 2-3 but to let them learn 'the scientific method' of analysis then experimentation followed by revised analysis. The representative rocket isn't a TARC competitor per se but something of similar size so they can get a feel for Rocsim analysis vs real results.

Most kids think that Rocsim gives them the answer, my thought is to let them learn how Rocsim is a tool, but testing is needed to use the tool effectively (this lesson is lost on many of the right out of college engineers I hire at the 'day job'). After seeing some real world results, it may give them a better feel for what they need to do on their design / testing.

I think that having a demonstration rocket of similar size (and mass) to a TARC competition rocket provides too much of a basis for them to start their rocket design and development. If you want to show them how Rocsim is used as a tool in the analysis of a rocket design and testing this can be accomplished using single 'B' and/or 'C' motor powered model rocket (non egg lofting) of smaller size (a single B or C motor is not powerful enough to launch an egg to a TARC altitude) and let them use the simulator to predict an altitude that is verified using two station tracking as shown in the Handbook. The idea is to show them that Rocsim (and Open Rocket, etc.) does not provide 'absolute answers' but is a tool that makes testing, analysis and design adjustments more intergrated to achieve an optimal design.

Same idea on the chute, how you pack the chute can change the decent times dramatically in terms of TARC scores, plus getting a feel for how different 15" chutes can be. Again, my goal wasn't to do the work for them but to help them understand the variables as they go forward in their effort.

Hopefully the mentor and the advisor can meet with the TARC team early, before design has begun, so that they can provide guidance to the team as they brainstorm about the elements of a rocket and how the variables of each element may affect the design. So when the team starts looking at the variables associated with the recovery of the rocket and it's parachute you, as mentor/advisor, can mention the two variables (parachute packing and parachute material) listed above to start the discussion. This is their time to excersize critical thinking and make discoveries.

Maybe you should PM or email Mr Barber with your ideas and see what he has to say.

:2:

 

[hardinlw]

I've mentored a team the past two years, and from my perspective the best thing you can do is get them used to the idea that they will need to make multiple test flights to calibrate their simulation. If there is concern that building a TARC-style rocket will prejudice them, build a simple 3FNC rocket and simulate it in Rocksim making the standard beginner mistakes :

1. Put in only the major components with no allowance for glue, paint, centering rings, launch lugs, etc. The simulation will thus weigh far less than the real rocket.

2. Use the default surface finish (glossy) which will calculate a Cd far lower than the actual rocket, especially if you give it a typical beginner finish, e.g. don't fill the spiral groove, leave blobs of glue, etc.

3. Leave the fins squared off instead of airfoiling them.

4. Put one fin on a little skewed so the rocket corkscrews instead of flying straight.

Now fly the thing and ask them why it only went half as high as Rocksim said it would. It is a simple matter to weight the rocket and put a calibration weight into the simulation, but if they don't fix the drag coefficient (or adjust the surface finish to match reality) the altitude prediction will still be off. This leads to a discussion of flight testing to calibrate the drag. If you want to drive another lesson home, pull out a duplicate rocket with a smooth finish and airfoiled fins and demonstrate the difference in altitude.

I've seen all of the above done. In fact, one team arrived at a club launch to qualify and had not made a single test flight. Needless to say, they were not at the finals. Kids today are so indoctrinated by computer games that they are surprised when reality raises its ugly head. If you can bring them face to face with some of these issues early in the process, they'll have the opportunity to redesign and retest, and redesign and retest, ...

 

[n5wd]

...2) Test Flight... rocket kit (about the same size and weight as a 2011 TARC rocket). Have all the information available ahead of time so a detailed ROCSIM model can be developed by the teams. Have good launch site data available (exact altitude, barometric pressure, winds launch rod length, etc), and let them try to predict the altitude. Launch the SAME rocket 3-5 times maybe using the same motor a few flights and then change the motor for another flight.

I think you're on the right track. You might also show them what it takes to reconcile a rocket's actual flight with RockSim's predictions, and then start dialing it in. I know that's where our teams have had a big problem over the last three years, so it's going to be one of our emphasis points in this year's training.

I wouldn't worry about prejudicing them towards any one particular design... they're going to do it their own way, anyway, based on all the factors you're showing them. The 3FNC TARC-task rocket is relatively generic, in the first place.

As for blasting off HP flights for TARC teams, DO NOT EVEN LET THEM SEE ANYTHING LARGER THAN A G being launched. I've had the experience of a team being overwhelmed by a kiddoh that wanted us (the school) to finance his high powered rocket (was really unhappy when we told him "no"), and went ahead and built a rocket that would have been capable of an L1 flight even though we kept telling him that it wasn't going to reach the altitude (750 feet that year- and it didn't break 700 on a G80). TARC isn't about high powered rocketry, and it's not about getting them interested in high powered rocketry (I know I'm preaching to the choir, but there's obviously some of our younger forum members that have high powered fever).

OK, you can let them SEE a high powered launch, but gotta make sure they understand that is NOT the design that'll get them very far in the contest.

 

[n5wd]

Isn't the general idea behind TARC that the various TARC teams do steps 2 and 3 on their own. They design, develop and simulate the rocket using software (ROCSIM, Open Rocket, etc) under various flight conditions and then once they are satisfied with their designed rocket they build it and test fly it several times?

While you're absolutely 100% correct that the idea behind TARC is that the kids research, design, build and fly their own rocket, they (most often) need some reference of what kind of rocket would be capable of performing the task. Letting them see how a TARC-task-capable rocket looks, is constructed, and flies is definitely within the letter and the spirit of the rules - for some of the kids it may be the first time they've ever seen a model rocket fly, and for some who have flown the little Estes models, the first they've seem of a rocket that's capable of being calibrated to a particular repeatable task. It's part of their education to show them what CAN do the job.

Of course, when they start doing the design and construction, you can't steer them one way or the other.

 

[Pippen]

I think that having a demonstration rocket of similar size (and mass) to a TARC competition rocket provides too much of a basis for them to start their rocket design and development. If you want to show them how Rocsim is used as a tool in the analysis of a rocket design and testing this can be accomplished using single 'B' and/or 'C' motor powered model rocket (non egg lofting) of smaller size (a single B or C motor is not powerful enough to launch an egg to a TARC altitude) and let them use the simulator to predict an altitude that is verified using two station tracking as shown in the Handbook. The idea is to show them that Rocsim (and Open Rocket, etc.) does not provide 'absolute answers' but is a tool that makes testing, analysis and design adjustments more intergrated to achieve an optimal design.

Hopefully the mentor and the advisor can meet with the TARC team early, before design has begun, so that they can provide guidance to the team as they brainstorm about the elements of a rocket and how the variables of each element may affect the design. So when the team starts looking at the variables associated with the recovery of the rocket and it's parachute you, as mentor/advisor, can mention the two variables (parachute packing and parachute material) listed above to start the discussion. This is their time to excersize critical thinking and make discoveries.

Maybe you should PM or email Mr Barber with your ideas and see what he has to say.

:2:

I agree.

When you start setting up activities for kids to learn something specific that you have in mind, it crosses the line from independent student-led discovery to teacher/mentor-guided discovery. It's efficient because it defines the problems for them in advance and gets them to the answer sooner, but it shortchanges a discovery-led learning experience.

If team members are wondering what the impact of different size engines are, then brainstorming, researching, and/or experimentation are important parts of the learning process. Mentoring says "Now that you've defined the problem, what are some ways you could go about finding the answer?" Teaching defines the problem ("How does a rocket behave with different sized engines?") and either demonstrates ("Watch as we launch the same rocket with five different engines") or sets up the framework for arriving to a solution ("Here's a rocket kit, now build it and go fly it with five different engines.").

 

[Pippen]

While you're absolutely 100% correct that the idea behind TARC is that the kids research, design, build and fly their own rocket, they (most often) need some reference of what kind of rocket would be capable of performing the task. Letting them see how a TARC-task-capable rocket looks, is constructed, and flies is definitely within the letter and the spirit of the rules - for some of the kids it may be the first time they've ever seen a model rocket fly, and for some who have flown the little Estes models, the first they've seem of a rocket that's capable of being calibrated to a particular repeatable task. .

Don't you think there's a difference between letting them see how a TARC-task-capable rocket looks, is constructed, and flies is different than conducting demonstrations so the members can see how one launches, flies, and lands under different variables?

 

[shreadvector]

Construct a model that is somewhat TARC-like but is not at all like that necessary for this year's contest targets and payload. In other words, make one that carries more eggs and uses a bigger parachute and simulate it and use a target altitude much different (like 500 feet). That way you can do a generic large model simulation comparison to reality and then have them suggest ways to adjust the simulation inputs to "dial it in".

And one of the responders here said that the impule limit has been removed. Not exactly. There is still a limit, it is simply higher than a single F motor (80 N-s). It's now the Model Rocket limit and clusters are allowed. An insane (not that there's anything wrong with that) team could indeed cluster up to any of the limits like the 125 gram total propellant limit or the "2 G" total-impulse limit.

 

[n5wd]

Don't you think there's a difference between letting them see how a TARC-task-capable rocket looks, is constructed, and flies is different than conducting demonstrations so the members can see how one launches, flies, and lands under different variables?

Sure, but you can do both with the same rocket. That way, they begin to see that minute changes can have big swings in performance insted of changing many different variables (say, different rockets) and them having no reference as to what really made the difference.

Understand that, from my perspective as a TARC sponsor, I have approximately 25 hours (5 months, Sept to Jan, one meeting per week, lasting approximately one hour a meeting - occasionally two hours) to get kids who may or may not have ever flown a rocket introduced to all of the principles, plus demonstrations, RockSim practice, etc, ready to design, build, and fly their rockets come the end of January. So I'm looking to maximize the impact of each flight - if I can get double-duty out of the demonstrations, all the much better.

 

[n5wd]

I... It's efficient because it defines the problems for them in advance and gets them to the answer sooner, but it shortchanges a discovery-led learning experience.

If TARC were an open-ended Project Based Learning experience, I'd agree with you. However, it's not. It's a targeted outcome experience with limited time for kids to master the engineering discipline.

 

[shreadvector]

If TARC were an open-ended Project Based Learning experience, I'd agree with you. However, it's not. It's a targeted outcome experience with limited time for kids to master the engineering discipline.

Excellent point. And limted funding (for most teams).

 

[kramer714]

all good feedback!

Sounds like a demo rocket would be worthwhile the goals would be,

1) Intro to a rocket this size, might have interest from people that haven't done a rocket ever or haven't done a larger (f-g size) rocket.

2) Get their feet wet in modeling / simulation of a rocket using the demo rocket as a pathfinder.

3) Get an appreciation of the 'fidelity of the model' by looking at theoretical vs actual results including building variability.

4) Provide a springboard for discussions of their designs.

5) Get familiar with the data generated at a launch before they test their design.

6) Network with other fliers TARC and Non TARC.


Any So-Cal teams think they would come out?

 

[shreadvector]

Be sure to post announcements about this event on both the TARC and SCRA YahooGroups. I'm assuming you'll alert the ROC folks through their forum or mailing list.

https://groups.yahoo.com/group/NARTARC/

https://groups.yahoo.com/group/SoCalRocketNAR430/

 

[kramer714]

I'm pleased to announce TARC day at the annual ROCtober launch at Lucerne Dry lake bed California, October 9th, 2010. Attached is an information sheet on the activities planned.

Thanks for everyone who gave me input on activities that will help out the teams. Teams, Mentors, or Sponsors that would like to attend please E-mail me for more information.

View attachment roctober flyer - TARC 8-14 b.pdf

 

[sunward]

.... launch a 15" parachute ....
Maybe launch different style 15" parachutes....

A little correction here.

It will be very difficult to try "different styles" of parachutes.

The parachute used:

.....return to the ground using only one parachute of 15 inches diameter as its sole deployed recovery
system. Every part of the outer edge of the canopy of this parachute must lie outside a circle of
14 inches diameter and inside a circle of 16 inches diameter. This canopy measurement will be
done with the parachute laid flat, or if the parachute is a shape that will not lay flat, then with
discs that are compared to the base of the inflated canopy.

There is more (using streamer also) but you will be kind of limited to the shape.

 

[kramer714]

Angelo,

Actually decided to skip the parachute demo for TARC day. I thinned out the activities trying to keep the event to a manageable level.

The logic behind the parachute demo was to give the teams an idea on the number factors on 'hang time' and deployment time that a parachute could have including,

How it is packaged
shroud length
weight of the parachute
porosity
spill hole
shape (flat, hemispherical, other)
weight
wadding - barf - piston (not sure how these would affect the deployment time but another variable to think of)


Just my thoughts....

Suggestions on the demo rocket recovery system?

Mike Kramer

 

[Bazookadale]

A little correction here.

It will be very difficult to try "different styles" of parachutes.

The parachute used:

There is more (using streamer also) but you will be kind of limited to the shape.

I think there are plenty of "different style" 15" parachutes - for example you could have 4 shroud lines vs 44 shroud lines ect

 

[sunward]

....Suggestions on the demo rocket recovery system? ...

It seems all the points are small. I wold mention them and let the builders decide on their own.

I think there are plenty of "different style" 15" parachutes - for example you could have 4 shroud lines vs 44 shroud lines ect

True, but this year the size mentioned is very restrictive. A 15" 6 sided will not fit within the specifications. So I see a few disqualifications this year.

 

[kramer714]

True, but this year the size mentioned is very restrictive. A 15" 6 sided will not fit within the specifications. So I see a few disqualifications this year.

That could be something to talk about on TARC day. Have a template and show the teams what makes a 'legal' chute.

 

[sunward]

That could be something to talk about on TARC day. Have a template and show the teams what makes a 'legal' chute.

two circles. One 14 and the other 16" in diameter.

I also checked and drew with Illustrator the two circles with a 6 sided parachute. Won't fit regardless of the size. (Didn't check for more than 6 sides.)

 

[kramer714]

I kind of wonder how the 'sky angle' or 'Rocketman' chutes would measure up..

 

[n5wd]

Hmmm... do you think that an X-form with rounded outer edges would meet the spirit and letter of the rule?

 

[sunward]

Hmmm... do you think that an X-form with rounded outer edges would meet the spirit and letter of the rule?

I have attached a diagram with the 14 and 16 inch circle. Also shown are a 16" - 6 sided and a 16in - 8 sided parachute.

A 6 sided parachute won't work. Even at the largest size allowed, some of the sides will be inside the 14in circle. You could do an 8 sided, but not much play. You may have extra work and weight for the shroud lines.

You could start rounding rounding corners, but is it worth the extra work?

The rules just say it has to fit inside the 2 circles. Laid flat if it has a shape. There may be some problems with weird shapes, but I don't see that being a problem.

 

[kramer714]

This canopy measurement will be
done with the parachute laid flat, or if the parachute is a shape that will not lay flat, then with
discs that are compared to the base of the inflated canopy.

From the TARC 2011 rules.

I'm not sure how to interpret the spirit and letter of the rule, hoping someone from TARC will weigh in.

I have no doubt that Sunward has a chute that meets the requirements. The phrase 'inflated canopy' is the one that is bugging me, on a 'Sky Angle' or hemispheric chute would the diameter be the inflated diameter at the widest part? Seems you could use a significantly larger chute that way, I don't think that is what they had in mind but would like to get clarification to keep it fair.

Time for clarification from TARC

 

[shreadvector]

From the TARC 2011 rules.

I'm not sure how to interpret the spirit and letter of the rule, hoping someone from TARC will weigh in.

I have no doubt that Sunward has a chute that meets the requirements. The phrase 'inflated canopy' is the one that is bugging me, on a 'Sky Angle' or hemispheric chute would the diameter be the inflated diameter at the widest part? Seems you could use a significantly larger chute that way, I don't think that is what they had in mind but would like to get clarification to keep it fair.

Time for clarification from TARC

Ask Trip for clarification on the TARC YahooGroup. Then we will get the answer. until then, I'm assuming that you hold the parachute as if it was inflated. For a hemisperical or similar sewn together parachute, the bottom will reach it's maximum size when it is held open as far as it will go. For a flat parasheet, this is a simple flat shape, but for a sewn together 3-D parachute, the bottom will simply be whatever the size it is when opened out to the limits of the fabric.

yes, that will be annoying to measure and verify out on the field, but it can be done.

And now to go back to points touched on way earlier in the thread:

I love the idea of demonstrating for them on a generic rocket how the real world rocket will not go as high as the simulation - forcing them to find out why (glue weight, incorrect drag coefficient in simulation, motor performance variation, etc.). Excellent. Thanks.

Please also empasize that this a MODEL ROCKET comepetition, not a HIGH POWER ROCKET competition. Last year, every team that use HPR building techniques and materials was unable to meet the altitude and/or duration targets. Mostly it was the duration. This year, they will have a hard time with the parchute size if they have a grossly heavy rocket.

Also, please emphasize the importance of fins only in the rear and that the fins need to stick out into the airstream (instead of fins that are have tiny spans and long roots and sit inside the turbulent boundary layer and don't work much until the rocket has deviated from it's intended trajectory). MANY teams think the simulations are telling them their rocket sare overstable and they build smaller fins or add fins at the top to "fix" the overstability. This is a disaster. mentors should stop disasters before they occur as this is not designing the rocket for them, it is providing basic science, experience and safety advice.

 

[kramer714]

Fred,

All good points, the key thing you hit on was

MANY teams think the simulations are telling them their rocket sare overstable and they build smaller fins or add fins at the top to "fix" the overstability.

One of the goals of this effort is to get the teams really thinking about what is going into their simulations, the old garbage in garbage out theory. I plan to make 2 'identical' rockets, both will have the same parts list, but the construction methods will be different. Both will be launched with F62 motors, I picked this motor because I have a bunch of them. Any suggestions of alternate motors should include a box of free reloads, really.

On one I plan to use good 'appropriate' building methods, sand the fins (thin ply) nice bevel on the leading and trailing edges, yellow glue, nice small fillets, fill in the spiral, simple Kaplow Clip retention. Fins nice and straight jig bonded.

On the other one I plan to use epoxy / milled glass for all the joints, less than optimal fin orientation (eyeball in place fins), minimal finishing, minimal fin bevel (just break the sharp edge).

Both will have a hemispherical nose cone, it is easy for me to make (self funded effort here folks) plus I didn't want to try to steer them to a particular flavor / design. I figured it was either conical or hemispherical, and the hemis are more durable.

I am going to have a clear payload section for the altimeter. I had some clear tube the same diameter as my body tube, The tube is a bit thicker than they would use but adds about the same weight as an egg (and again, I had it around, price was right). I specifically don't want to address the egg container, let them figure that out in their own.

My hope is the two rockets sitting on the table will give the mentors something to discuss with the teams. The flight results should get the kids thinking about what the simulation is really doing. Start the discussion, not solve the problem for them, get them thinking that they don't know what they don't know.

Fred, Think you are going to come out for TARC Day?

Mike Kramer

P.S. If I make the 'kit' want to build one of them? (no pressure, really)

P.P.S. Msg sent to NARTARC yahoo group