[NRV Rocketry] How To Get into High Power Rockets

[Thomas Weeks]

Someone at the meeting the other night asked me, 
        "Tweeks.. how do I 'graduate' from fun little model rockets to these
         big ones that I've seen fly at some of these local NRVR launches?"

What's the Same, and What's Different for High Power?
============================================================
For those who are wanting to move to, or even just dabble in High Power 
rocketry, here are some of the most common differences between model rockets 
(A, B, C, D motors), medium power (E, F and G motors) and bigger beefier High 
Power (generally, H, I and up motors):

Some construction and flight principals stay the same as low power/model rocketry:
-What makes a rocket stable
  -Center of Gravity in front of Center of Pressure by 1.5 Body tube diameters
   (remember the string, "spin test"?)
  -You need a 5:1 thrust(N) to weight(N) ratio 
   or weight of rocket(lbs) x 4.45(N/lb) x 5   ~ or < avg thrust of motor (N)
   Ex: 1lb rocket needs at least 22.25 Newtons of thrust motor, something
    like an F23 or bigger
    http://www.apogeerockets.com/Rocket_Motors/AeroTech_Motors/29mm_Motors_Single_Use
-Undistracted attention to packing your own chute
 (feels to tight.. do it again)


The biggest differences between model/low-power and what you need to do for
high power rockets construction and design wise are:
-Higher speed flight = MUCH more violent component stresses
-More stresses = Design Changes: "Beef-Up" everything
  -Move from glue to epoxy
  -beef up motor mount/bulkhead strength
  -move from elastic shock cords to nylon/kevlar shock cord
  -move from 2ft shock cord to 20ft shock cord
  -move from chute snap swivels to 1/4" quick links
  -zipper proofing your design or body tube
  -reinforce body tube strength (fiberglass/kevlar/carbon fiber)
  -reinforce fin root edge/mounting strength (through tube mounting)
  -use BEEFY fin fillets (epoxy, metal putty epoxy, etc)
  -high speed = greater internal pressure = popped nosecones = make vent holes
  -for chute protection move from paper wadding to kevlar cute cover
  -move from launch lugs to rail buttons
-If in doubt, over design (to a point :)
-Bigger rockets = more weight (more violent launches & ejections)
-More weight requires slower/safer recoveries = larger chutes
-Larger Chutes = more drift and...
  -need for smaller drogue chutes (more toward L2) to slow them down first
  -need for altimeter controlled drogue & main chutes ejections
  -need for Ebay/electronics and static port holes
  -need for secondary/backup ejection systems
  -ground ejection system testing
-Higher speed/altitude/mass = MUCH more violent ejections
  -need for nosecone sheer pins to hold main chute in until needed
-Preflight check list(s) (due to added ejection system complexities)
-Compare notes, ask questions, learn from the experts (end THEIR mistakes ;)

Also.. this is a great illustrated book to much of what I list above and more:
	"Modern High-Power Rocketry 2", by Mark Canepa
	http://www.amazon.com/dp/1412058104
	(we just gave a copy away at the last meeting!) 


What High Power Certification Is, And What's Required:
========================================================
To even purchase these high power motors though requires a certification. So 
that's one reason why people even bother getting certified.  
You want to fly big rockets?
You need to get certified (which is the industries way of keeping everything safe).

Here is some info on what certification actually means:
https://en.wikipedia.org/wiki/High-power_rocketry#Certification_in_the_USA_.26_Canada

This means that you'll first need to either become a formal member of either NAR or 
TRA (Tripoli):
	http://www.tripoli.org/Certifications/tabid/80/Default.aspx
	http://www.nar.org/NARjoin.html

NRVR is currently a TRA group(#143), but we can certify NAR members also,
and the certifications are cross group compatible.

You very first HP motor purchase is allowed, but you'll want to contact our
group's RSO (rso at nrvr dot org) to go over your rocket, the motor you want, 
and announce that you desire to do a certification launch attempt. At this 
point, you do not have to be a member of NRVR, VAST, or any other local 
"club", but this is where most people go ahead and do join, as we will be 
helping you a lot during your journey to becoming certified. Here's how
to join NRV Rocketry (our local club in the NRV):
	http://nrvr.org/membership/


Get Your Level-1 Cert with a Rocket That Can Fly Both Medium & High Power:
==============================================================================
I always recommend that folks in the NRV start off with a dual purpose rocket 
that can fly as either medium power (F-G) or high power (H, I etc).  Especially
since some of our launches are medium and model rocket flights only, while only
some (at this point) allow for high power flights. Here are several good 
Rockets to choose from, many of which can handle both medium power (F & G) 
as well as starter High Power (H) motors:
	http://www.apogeerockets.com/Rocket_Kits/Level_1_Certification_Kits

NOTE: Personally, I recommend getting one with a 38mm motor mount. Cessaroni
motors are the easiest (and cleanest) to work with.  And they have a deal 
right now.  If you're buying a "cert motor refill", the y give you the metal 
motor casing (a $40-50 value) for free! Just mention it when buying your 
Cessaroni motor refill grains. :)

Also. here are a few really nice little videos (from Apogee) on the 
ins and outs of "Level-1" HP rocketry and certification:

Intro to Level 1 Certification Rockets
http://www.apogeerockets.com/Advanced_Construction_Videos/Rocketry_Video_60


and then if you really want to see what building a Level-1 Rocket is like from 
start to finish, here's a really nice ten part video series on how to construct 
high power rockets, from beginning to end:


Building Your First High Power Rocket - Part 1	
http://www.apogeerockets.com/Advanced_Construction_Videos/Rocketry_Video_61


these videos above make for a really of useful set of starter videos to help 
those interested in moving a bit beyond the basic Estes model rockets of our 
childhood.

Any other certified members have anything similar to share? Suggestions? 
Gotchas? Lessons Learned?

Tweeks
NRV Rocketry Founder