The Rocket Rev's Sermons - Getting started in High Power Rocketry

So you want to know what's involved with obtaining a Level 1 High Power Rocketry Tripoli Certification?  Well you came to the right place to find out.  I'll try to be as concise as possible.  But there is a lot involved with high power certifications.  So sit back, read, and absorb.

The first thing you must do is decide whether or not you want to join Tripoli first and certify later OR join Tripoli and certify at the same time.  If you haven’t done much with rocketry, you probably want to join now and certify later.  That way, you'll have plenty of time to learn what you need to learn about how to build rockets and fly them before you try the larger motors that make up the classification called "high power rocketry."

FOR THOSE WHO HAVE LITTLE ROCKETRY EXPERIENCE, START HERE!
(or skip to the next section)

First off, don’t buy anything that is called Ready To Fly.  It is a waste of your time to fly something somebody else built!  I would suggest starting with a couple of Estes kits like the MK-109, the Bandit, or a Fat Boy (a very popular kit).  Or if you don’t want to go with Estes, try a Quest low power rocket kit like the Tomahawk SLCM, the Falcon, or one of my all time favorites, the Quest scale model Nike Smoke.  These will fly on up to “C” motors.  Then move up to “D” motors with an Estes Silver Comet, a Python, or a Super Nova Payloader.   If you get really ambitious try an Estes Phoenix Missile.  This baby will fly on “D” and “E” powered motors.  These are all considered “low power” rockets and motors.  After you’ve built and successfully flown these babies you are ready to move up to more power!

Now you are ready to graduate to medium power rocket kits.  I would suggest you try one of Aerotech’s 2.6 in diameter kits like the Initiator, the Wart-Hog, or the Strong Arm.  Any one or more of these three kits are perfect to bring you right up to the very edge of high power!  They fly on “F” and “G” motors.

If you've built and flown model rockets before, you probably have it figured out that an A motor is half the size of a B motor which is half the size of a C motor which is half the size of a D motor which is half the...etcetera.  Get the idea?  By the time you get to high power you have doubled the size of your original A motor 7 times and that's a lot of power.  You may or may not know that each motor size is actually a range of total power between set guidelines. Motors are classed by the amount of energy that is released during their "burn" and which is generally measured in Newtons, a unit of force.  For instance, a D class motor has between 21 and 40 newtons of total power, an F class motor has between 41 and 80 newtons of total power, and a G class motor has between 81 and 160 newtons of total power.  When you reach 161 newtons of power and beyond, you have passed out of what is called "model rocketry" and reached what is called "high power rocketry."  The government says that in order for a civilian to be involved with high power rocketry, that person must be at least 18 years of age and a member of either a college or university, or a member of some other form of educational organization that will have oversight over the safe usage of the high power rocket motors.  The government also says that we need an FAA waiver to fly our high power rockets. Tripoli is one of these educational, safety oversight, and amateur High Power Rocketry organizations in the country.

Having experience building and flying model rockets before getting into high power rocketry is a big plus, because you should have already learned a great deal about things like center of gravity and center of pressure, stability, recovery systems, rods, pads, launch systems, etc. This hobby is an amateur version of rocket science.  You do not need to be a scientist, but you must learn the basic principles of rocket science to avoid "ye old" crash and burn experiences.  Some will be unavoidable, but it is always good to learn from the mistakes of others when possible.

So if you have a lot to learn before you build that first high power rocket, you should join Tripoli now, get the magazine (maybe some back issues?) and start learning the basics. One can learn a lot from flying model rockets!  I certainly did!  Check out the Tripoli web site. There is plenty there to read, learn, and absorb.  One thing to remember with high power rocketry: use two part EPOXY for construction.  Put the Elmers away.  I have used cyanoacrilate (CA or super glue) for a couple of smaller mid power rockets, but for your cert flight, stick with EPOXY.
 

FOR THOSE WHO HAVE BEEN BUILDING AND FLYING MODEL ROCKETS, START HERE!

Now if you already have lots of model rocketry experience building, designing, flying, repairing, flying again, and recovering, with kits as well as scratch building, then you are probably ready to buy your first high power kit and try for that Level One certification.  The advantage to the experienced rocketeer is that you can buy your L-1 kit, build it, and then talk to a vendor in order to purchase a reloadable high power motor and reload kit.  I have lots of suggestions on this too. Then you can bring your completed rocket to any Tripoli sanctioned launch with money for your membership and JOIN Tripoli on the flying field.  Then you can attempt your Level One (L-1) certification flight right on the spot!  This way, when you succeed (I’m thinking positively here) and your Tripoli membership papers come, your Membership card will already have that wonderful L-1 in the corner to show one and all that you are a high power certified flier!

Now, let's look at what kind of rocket kit you should buy.  Remember that this is NOT A CHEAP HOBBY!  Be prepared to spend money.  Whether you scratch build or get a kit, it will cost money!  Now for your first high power certification flight, I would suggest that you purchase a kit.  This will make motor and ejection charge delay selection easier (one of the hardest parts of this hobby) as the kit's manufacturer already has suggested motors and delays to use for each of their kits. You will notice right away that I prefer the large diameter rockets.  The larger airframes are easier to build, because you can get your hands down into them while you build and when you prep your rocket for flight.  This is a big advantage over the smaller airframes that one can only look into!  I would suggest that you avoid minimum diameter stuff until you have more experience with the hobby.  Minimum Diameter means that the motor tube is the same as the airframe tubing, i.e. a 38 mm motor in a 38 mm airframe!  High Power minimum diameter can put your rocket out of sight so fast that recovery becomes problematic.  Most of the lost rockets I know about were smaller diameters, and that's just the way it is.  The bigger the rocket the harder it is to loose it!  You will of course need to make up your own mind on this one. The disadvantage to larger diameter is larger price tags.   There are two main high power rocket kit manufacturers, Public Missiles Limited and LOC Precision.  Each manufacturer and each kit has its own set of advantages and disadvantages.  So I will try to let you know my take on the subject.  Also not to confuse you more, but both PML and LOC Precision will give you lots of different kit choices, in lots of different airframe diameters, and lots of different price ranges.  One last note, the manufacturer’s designation for their airframe tubing is the inside diameter of the tube.  So a tube that is called a BT3.00 or a PT 3.00 is actually 3 inches in its inside diameter.  LOC’s BT3.00 is actually 3.100 inches in OD and PML’s PT3.00 is actually 3.125 in OD measurement.  Nose cones are designated by which airframe tube they are designed to fit.

Public Missiles Limited (PML) has two kinds of rocket kits available based upon two different airframe (body of the rocket) materials: Phenolic tubing and their new Quantum tubing.  It has been a standing joke for the last decade that with PML Phenolic airframes you "fly it/repair it then fly it/ repair it then...."  The Phenolic airframe material is VERY STRONG, no doubt about it.  But so was the Titanic.  The steel rivets with which the Titanic was built were very strong but they were also very brittle and that contributed to the ships demise.  Well Phenolic is very strong but like the steel rivets in the Titanic, Phenolic is also brittle.  I would suggest that you avoid Phenolic airframes like they were the plague!  But PML's new Quantum Tubing is quite serviceable if only available up to 4 inches in diameter at this time.  The Quantum material is a filled plastic composite.  Unfortunately, PML has not yet been able to manufacture tube couplers  from their new Quantum material.   A tube coupler is the part that connects two sections of the same airframe tubing together and also used for payload sections and airframe extensions.  But they will be doing so in the near future.  Right now, their QT kits have the same old Phenolic tube couplers and there have been a lot of complaints about this mismatch of materials.  The Phenolic and Quantum materials expand and contract at different rates causing various flight problems including stuck parachutes that can't deploy because the Phenolic tube coupler is stuck in the QT airframe.  This is NOT a good thing.  For the time being, I would avoid any PML kit that has a payload section in order to avoid the Phenolic tube couplers. Which diameter kit depends partly on your preferences and pocket book?  The smaller diameters are a bit cheaper, but they are harder to work on because you can't get your hand inside the airframe!  PML also uses G-10 fiberglass fins.  They are incredibly strong for their size and PML uses "to the motor mount" fin attachment. (more on this in a minute).  Our webmaster, Dean Cory has had his Quantum Tube based 2.6" Small Endeavour, fall over 2,500 feet doing a nice core sample in the sod with no damage to the Quantum Tube or The G-10 fiberglass fins.  Dean recommends the following PML kits: 3" Ariel, 3" AMRAM, 4" AMRAM and the 4" Endeavor as you can do level 1 and level 2 on the same kit!  Remember to follow kit building instructions carefully!

As to LOC/Precision kits, you can take your pick.  LOC uses paper airframe tubing.  It is pretty much like the tubing for model rocket kits except that the tubing is MUCH THICKER and Far Stronger!  Also, instead of plastic or balsa fin material, LOC uses aircraft grade birch plywood fins.  These are usually 5-7 layers of ply and around .125" thick and thicker!  Now, I did my first high power flight with a LOC parts rocket, and since PML's quantum tubing only came out about a year ago, I've spent most of my time building LOC kits and using LOC parts.  What I love about LOC airframes is that with the large diameters they have a great deal of durability built in to the airframe.  I had my LOC Magnum 5.38 inch diameter kit fall from 2000 feet up, land sideways in the grass, and I flew it an hour later after re-prepping the rocket.  Yes, the tube had been creased along the length of it and the paint was the worse for the wear, but it was still ready to fly without any repair work.  I love LOC's 5.38 airframe tubing.  The OD is 5.54 inches if you were wondering.  Now LOC has two great kits in this size tubing that are suitable for a Level One certification flight.  The first is the LOC Mini-Mag and the other is the LOC I-ROC. Both are superb kits and the I-ROC is large enough that you could easily do your level 2 certification flight with it if you wanted to.   I've been flying my Mini-Mag for eight years now.  Take a look at it at the next launch and see that I’ve replaced two fins and the front end of the airframe, but “Mr. Cone Head” keeps coming back for more!   Both of these kits have a 38 mm motor mount tube, which is the most versatile motor size on the market.  More on motors later in this article.  The disadvantage to LOC kits was also one of its earliest advantages.  LOC was the first company to sell kits with slots ready for "through the wall" fin mounting. This was a design feature that dramatically increased the strength of the fin mounting.  NO longer were fins simply epoxied to the outside of the airframe with two epoxy fillets.  LOC slotted their airframes and made the fins to stick through so that epoxy could be applied both on the inside and the outside of the rocket.  The "through the wall" gave four fillets per fin which was a doubling of the strength of surface mounting.  But this "through the wall" technique has been greatly improved upon with what is now called "to the motor mount" fin attachment.

With “to the motor mount tube” fin attachment, the fin is epoxied to the motor mount tube, to the inside of the airframe, and to the outside of the airframe.  That’s six fillets per fin.  This also gives a much stiffer fin mounting for less flutter.  Unfortunately, not many of LOC’s kits come with “to the motor mount” fin attachment yet.  Ask your dealer which ones already have it.  You can also do what I’ve done and cut your own fins for your LOC rocket kits with longer tangs.  The tang is the part of the fin that sticks into the airframe.   This way you can make your own “to motor mount” fin attachments out of aircraft grade plywood.  But do not use cheap grades of plywood as they will fall apart with high power rocketry applications!   Use ONLY Aircraft Grade plywood!  Most hobby shops carry good stuff.  For instance, 1/8 inch thick aircraft grade plywood (suitable for up to 5.54 inch diameter non mach busting rockets) should have a minimum of 5 layers of cross hatched ply.  Six or seven layers are even better.   For the really big 5.38 LOC kits that use 54mm and larger motors, LOC uses ¼ inch aircraft grade plywood.  And on one LOC kit, the “K-Load,” they utilize g-10 fins!  Of course this bad puppy has a 98 mm motor mount squeezed into the 5.38 airframe.  I love mine though I’ve only ever flown it on 54mm and 75mm motors.

As to what motor to buy for certifying?  I'd suggest that you go with something in the Aerotech or Dr. Rocket  38 mm line of reloadable motor systems. Your kit will show you which motors and delays are suitable for which rocket kits. You can get anything from small H motors to the almost full J Aerotech J-570 motors in 38 mm.  Aerotech has 14 different reloads kits for their 38 mm motors.  That's a lot of choices.  Aerotech is also producing the Kosdon Fast and Slow propellant formulations for the Aerotech/Dr. Rocket  reloadable motors, which should be available by the time you read this.  Also in the summer of 2001 Aerotech is scheduled to have available the REDLINE propellant also available for the Aerotech/Dr. Rocket 38 systems.  Generally speaking, the 38-240 motor is one of my favorites.  It is very versatile and I use mine a great deal. I like the 38 mm size because you can still at least get a couple of fingers inside to help load the motor and to clean it after the flight.  Of course what size motor you want to get depends on what size rocket you want to fly and how high you want to fly it!  But anything bigger than 38 mm will probably require you to have a BATF Low Explosives User’s Permit (see Tripoli Web Site for more info).  The kit you purchase will partly determine which motor you need to buy.  Of course there are many fliers who would gladly loan you a motor casing for your cert flight, but you probably will want to fly it again sometime, so you might as well purchase your very own motor to reload.  Aerotech reloads are the most reliable on the market and the most easily available.  I'm quite sure that Tim from Al's hobbies would be glad to sell you one for your flight.

One other thing to think about with motor selection is environmental conditions.  Wind is one big factor to keep always in mind.  When there is no wind, a nice slow dramatic take off can be a beautiful thing to see.  But that same dramatic nice and slow takeoff in a 15 mile per hour wind can be disastrous!  When a rocket’s vertical acceleration is NOT stronger than the wind’s sideways push; a rocket will turn into the direction of the wind.  This is called “weather-cocking” and it can spell the doom of any rocket.  The higher the wind, the higher the average thrust motor you want to use.  This helps avoid having your rocket turn sharply into the wind after it leaves the launch pad and flying sideways way downrange to crash and experience a ground disassembly (not a good thing).   Rocket Kit manufacturers often name appropriate motors and delays to use in their specific rockets.  But these motor/delay selections are made with little wind in mind and with the expectation of a vertical flight.  When a rocket turns into the wind even just a few degrees, it will reach its maximum altitude quicker than if it had gone straight up.  Then guess what?  The motor’s delay selection is suddenly way too long. Let’s look at a hypothetical rocket to show you what I mean.

Let’s take a four inch diameter 4 pound rocket (fully loaded) that flies nice and straight up on a 5 mph windy day to a perfect apogee deployment with a 10 second delay on an Aerotech H-73j-Medium (a 10 second) delay reload.  It exits the launch rod at 40 feet per second.  This same rocket and same motor on a day with a 15 mph wind might weather-cock 25 to 30 degrees reaching apogee in only 6 seconds.  The rocket weathercocks because it is only moving at 40 feet per second vertically while the 15 mph wind is pushing the fins sideways at 22 feet per second when it exits the launch rod.  This will cause a severe weather cock.  The problem is you still have a 10 second delay in place.  So what happens?  The rocket it arcing over in ballistic fashion, far short of it’s expected altitude and moving downrange still at a fast speed, and in fact the parachute deployment is now four seconds after apogee with the rocket moving at over a 150 feet per second.  This can cause separations, parachute stripping, and zippers.  A separation is when something disconnects and the rocket falls in two or more pieces (not good).  A parachute stripping is just that, the parachute strips itself into long thin strips of parachute material causing another ground recovery (NOT GOOD).  A zipper is when part of the recovery harness is actually ripped right through the airframe (also NOT GOOD).  To avoid these problems I suggest that in a higher wind, use a higher average thrust motor to overcome the effects of the wind.  That same rocket earlier in this paragraph on the H-123 would leave the launch rod at approximately 60 feet per second and only be deflected about 15 degrees off vertical by the wind.  This same rocket on the H-242 would blast off at over 100 feet per second off the launch rod and you would hardly notice the 5 degrees off vertical deflection caused by the wind.    All three of these reloads, the H-73-J, the H-123-W, and the H-242-T fit the same 38-240 motor casing, but they give dramatically different results.  There are many things with motors to think about but that’s another rocket sermon all by itself.
 
Anyway, I hope this helps you to understand about how to get started in this hobby.  If you have any other questions, feel free to ask.  I always try to help.

See you on the flight line!

Brad, the Rocket Rev., Wilson
Tripoli #01630
NAR #70929
Dual high power certified L-3
President of Tripoli Quad Cities
Prefecture #39

NAR Vs. Tripoli

NAR or Tripoli, which should I join? I get this question a lot, so here's my answer!

Just to let you know, I am a member of both NAR and Tripoli.  So the following remarks come from my years of
experience with BOTH organizations.  What follows is my opinion, but it is at least, both an informed and experienced opinion.  Now, I willingly admit that annually it will cost $23 more to join Tripoli than it costs to join NAR.  But high power rocketry is an expensive hobby by its very definition.  If a $23 difference is going to decide for you, then I'll be honest with you and say right up front that doing high power rocketry in either organization is probably NOT for you.  The $23 cost differential between NAR and Tripoli is only one factor among many, in deciding which organization you should join.  Well if money isn’t your deciding issue then read on.

What about joining either NAR at the launch and doing an high power certification at the same time?  Well, there is a slight problem with joining NAR at any launch that I’ve ever been to; there is just no way to join NAR at a local launch.  There is therefore no way to certify high power with NAR on the same day you join.  NAR does not have a mechanism for doing field memberships at local launches.  The quickest way to join NAR is to go on line and use their "secure" on-line credit card method of payment.  This does work.  BUT, you need to know that until you have your current NAR membership card in hand along with the necessary NAR high power certification paperwork, you CANNOT even ATTEMPT to certify high power at either any launch.  It might take several weeks (or more) for your stuff to clear NAR headquarters and get back to you by snail mail before you can attempt a level one certification.

 Competition is something else to put into the mix of things to think about.  If you are interested in LOTS of competitions, then NAR is the organization that you want to join.  NAR is a competition driven group.  NAR does some incredible things with competitions.  I have had a lot of fun doing NAR competitions.  I have also felt like the competition stuff was getting in the way of having fun.  But that’s me!  If you like compiling competition points then NAR is for you.

Also, NAR is slowly getting into high power rocketry.  But it is an afterthought.  NAR was reluctantly brought into high power by some of its membership who said "get into high power or we quit NAR."  For a competition driven organization it has taken them years to begin any high power competitions.  And even now, they are only just starting with a couple of small 29 mm H motor competitions because of membership demand. There was a time when NAR worked against high power rocketry but that is thankfully in the past.  But one can at least now fly high power with NAR.  And NAR does now have a multi-level high power certification program (based upon Tripoli’s program if I may be so bold).   But their program is a day late and a dollar short as far as I am concerned.   Personally, I don’t like what appears to be a lack of oversight for NAR’s high power program.  It just seems to be lacking the teeth to make it a great high power program like Tripoli’s.

Now to the reasons that I believe you should join Tripoli.  Tripoli is the easiest rocketry association to join.  You can fill out the "Tripoli Field Membership" paperwork that every Tripoli Prefect (head of a local Tripoli group, that’s me) brings to every launch.  You then pay the prefect (me) your Tripoli membership fee (cash, check, or credit card), and then you can immediately attempt your level-1 high power certification flight right on the same day you joined.  If your L-1 certification flight is successful (and you can continue trying on that same day as long as you have a rocket that is still fly-able at level one) when your membership card comes, it will already have your high power certification listed right on your Tripoli membership card.  You even get a copy of your Membership/Level-1 Certification paperwork right on the spot.  This way, you can go to any NAR or Tripoli launch and fly high power or go to any vendor and they can then sell you all the L-1 motors you can afford, even before your paperwork clears Tripoli HQ!  Tim with Al's Hobbies, our on site vendor, will gladly sell you all the L-1 stuff you want with this paper in your hand!

If you are interested in high power rocketry sport flying, then there is really only one organization for you.  It is the first and oldest (still operating) national (and now international) high power rocketry organization in the world.  It was the first  organization to create a multi-level high power certification program.  And it is the only one which was created by high  power rocketeers, for the sole purpose of the promotion of safe high power rocketry in all its forms (sport, experimental, research, certification, competitions both fun and serious, etc.).  That organization is the Tripoli Rocketry Association.

Let me know what you think.  I will listen to one and all, though as you can tell, my mind is name up.  I continue to belong to both organizations.  If you are into high power, then Tripoli is the organization for you!

Brad, the “Rocket Rev.,” Wilson
Tripoli #01630
NAR #70929
Dual L-3 High Power Certification
President of Tripoli Quad Cities