TCC NAR Competition Primer: USMRSC Rule 20, Altitude Competition (ALT)
This primer presents, in one place, all the information you need to succeed in NAR model rocket competition in this event.
TCC has provided a link to the official rules whenever we discuss a rule.
Your entry must:
* Be a model rocket as described by the United States Model Rocket Sporting Code. USMRSC 3.1-3.9
* NOT eject its motor casing(s) without a recovery system. USMRSC 9.2
* Have your NAR number or your name on the outside, large and clear enough that the contest officials can easily read it. Teams must use the Team number or name. USMRSC 9.4
* Have been constructed by yourself or by one or more members of your Team. You may not enter Ready-To-Fly rockets (no construction required) in NAR sanctioned competition. USMRSC 9.9
Know the rules
Your having a grasp of the bigger picture can increase your enjoyment of NAR competition. You can read the Pink Book Lite to see only the rules for competitors, not for Contest Directors or other contest officials. Read the full USMRSC (Pink Book) to see all the rules.
* Pink Book Lite: http://ojames3.tripod.com/tccnarcontesttips/USMRSCLight.html
* Full USMRSC: http://www.nar.org/pinkbook/
General Competition Tips:
Contest Etiquette by Kevin Paul Wickart, NAR 59720, cr 1998, the author
Beginning Competition -- The RSVP Principle by Kevin Paul Wickart, NAR 59720, cr 1998, the author
Guide to NAR Contest Rocketry Information for Beginners by Jeff Vincent, NAR 27910, Northeast Regional Contest Chair
Which are the Main USMRSC Rules for This Event?
What is the Goal?
* The goal of Altitude Competition (ALT) is to attain the highest altitude. USMRSC 20.1
Are There Any Special Considerations?
* Contest officials will use optical tracking (theodolites) as the preferred means of determining your entry’s altitude. USMRSC 14.1
* Contest officials have the option of requiring contestants to use an electronic altimeter. USMRSC 14.10
* ALT is divided into event classes based on the total impulse you can use. USMRSC 20.2
* Your entry can be single stage, multi-stage, or clustered as USMRSC 20 does not specify otherwise.
* ALT can be flown in FAI mode. This mode restricts the size and shape of the rocket. Contest officials will not allow your entry to fly if it does not conform to FAI restrictions. USMRSC 9.13
* NAR altitude flights are tracked to apogee or to ejection. You should be prepared for either method by knowing the altitude your model is likely to achieve at both apogee and ejection. Contact the Contest Director and ask which method they will use. USMRSC 14.3
Do I Have to Return My Entry?
* NO. However, the Contest Director can require that you return your entry. USMRSC 9.10
How Many Flights Can I Make?
* You can make up to two flights. USMRSC 10.1
* You can use more than one model. USMRSC 9.7
How is the Competition Scored?
* Highest altitude on a single flight wins.
What Will Disqualify My Entry?
* Your entry will be disqualified if it spins or loops and does not fly straight. USMRSC 9.3
* Your entry may be disqualified if, in the opinion of the contest officials, it does not comply with the competition rules or is unsafe in operation. (USMRSC 11.1, 11.2)
How About Some Suggestions for New Competitors?
* Keep it simple. Build a kit using the manufacturer’s directions and fly it using the recommended motor(s).
* Many kits that are available in your local hobby store are suitable for ALT. Three fins are better than four, but four is ok. Check the manufacturer’s list of recommended motors to ensure motor you want to use is recommended. Weight is your enemy. Pick a kit that is light in weight. Drag is your enemy. Pick a kit that has the smallest possible diameter.
* For your first few contests, use a single stage model flying on one motor. You can experiment with staging and clustering later.
* Weight is your enemy. The more paint your use, the more your rocket will weigh. You can use permanent markers to add color without adding a lot of weight.
* Weigh your model using a scale that is accurate to at least 0.1 ounce or 0.5 gram. If don’t weigh your model, fly it on different motors (before the contest) to see which goes higher. See Motor Selection and Delay Selection below.
* Optically tracked: The trackers/officials MUST be able to see your entry to track its altitude. This is easier for the lower powered events. For higher powered events or if trackers are having difficulty spotting the rockets, you should consider using “tracking powder”. Tracking powder is colored powdered chalk or dry Tempra paint that you pack in your rocket so that it is ejected with the recovery system. You can buy chalk for a carpenter’s chalk line at almost any hardware store. Chose a color that contrasts with the cloud/sky conditions you expect to encounter. Red works well in most conditions. Don’t use blue unless white clouds cover the sky. When you pack your recovery system, leave some space at the top for the powder. Tracking powder is messy. You can simply pour the powder in or wrap the powder in a small piece of recovery wadding to minimize the mess. Powder adds weight. Experiment before the contest to determine the minimum amount you can use and still get a noticeable cloud of powder at ejection. For example, for B ALT (about 1000 feet), using a ¾ inch body tube, use enough powder to fill the tube for ¾ inch (one caliber). This will be about 0.1 ounce of carpenter’s chalk.
More info on using tracking powder: http://www.apogeerockets.com/education/downloads/newsletter76.pdf
* Electronic Altimeter: Follow the manufacturer’s instructions and USMRSC 14.10. Check with your HPR buddies or others who use electronic altimeters for suggestions.
* Use a streamer for recovery. It’s easier to pack and will make your entry easier to recover.
* Use a piston launcher, tower launcher or pop-lug to reduce drag by eliminating the launch lug.
Piston Launcher: Qualified Competition Rockets: http://www.cybertravelog.com/qcr/pistons.html
Simple Tower: by Bob Supak, NAR 65523
- Take 3 1/4" aluminum rods, each about 24" long.
- Depending on what size model you want to launch, take an 18" piece of same body tube and put a few wraps of tape at each end.
- Place the 3 rods in a triangle around the body tube and secure with rubber bands, leaving 6" of the ends of the rods exposed.
- Now place the rods into a coffee can full of wet cement or plaster and let set. Voila - launch tower!
Pop-lug: Competition Model Rockets, Howard Kuhn http://www.oldrocketplans.com/pubs/CMR/pop_lug.pdf
* Motor Selection:
Select a motor that fits the event class. A impulse for A ALT, B motor for B ALT, etc. Generally, a lower average thrust (the number after the motor letter) will achieve a higher altitude and be easier to track. Use the minimum body tube diameter for the motor you want to use. Use a computer simulation (wRASP http://www.wrasp.com/ or wRASP32 http://tccnar.tripod.com/sims/082_wRASP32_221.zip) to help you select the best motor.
* Delay Selection:
Check with the contest officials to see if trackers will follow your entry to apogee of to ejection. If they are tracking to apogee, select a delay time such that ejection occurs after apogee. If they are tracking to ejection, select a delay time such that ejection occurs as close to apogee as possible; before or after apogee. Use a computer simulation (wRASP http://www.wrasp.com/ or wRASP32 http://tccnar.tripod.com/sims/082_wRASP32_221.zip) to help you select the best delay time.
Many vendors have competition models and/or competition supplies:
What Else & What Next?
What Type of Fins Shape is Best by Tim Van Milligan:
Design, Construction, and Flying Strategies for Achieving Maximum Altitudes by Tim Van Milligan
Take No Prisoners Tracking Powder
Simple Tower: by Bob Supak, NAR 65523
Take 3 1/4" aluminum rods, each about 24" long. Depending on what size model you want to launch, take an 18" piece of same body tube and put a few wraps of tape at each end. Place the 3 rods in a triangle around the body tube and secure with rubber bands, leaving 6" of the ends of the rods exposed. Now place the rods into a coffee can full of wet cement or plaster and let set. Voila - launch tower
Piston Launchers Explained – Apogee Components:
Floating Head Piston Launcher – The Odd Couple Team T-085, Jeff Vincent NAR 27910 and Chuck Weiss NAR 35775:
Yahoo group for discussing model rocket competition:
Use computer simulations to determine altitude and sink rate for various rocket/motor/parachute combinations.
* Free altitude simulations:
wRASP - http://www.wrasp.com/
* Free sink rate simulation:
US Spacemodeling (International Competition Tips):
US Spacemodeling Home Page (International Competition):
Aerospace Specialty Products Streamer and Parachute Tips:
George Gassaway’s Competition Tips – Take No Prisoners!
rmr Frequently Asked Questions – Part 9: Competition and Records: