High Power FAQ

This FAQ should answer many of your questions about High Power Rocketry.  See our other FAQ’s for more information.

For reference a High Power rocket is a model weighing more than 1500 grams (3.3 lb) or containing more than 125 grams of propellant or containing any single motor with more than 62.5 grams of propellant. See our Engine page for an overview of the different types of hobby rocket motors.

Q. I’m a successful model rocketeer. What do I need to get into HPR?
A. Here are some suggestions:

  • Start with E/F/G kits with 29mm motor mounts from LOC or Aerotech. These should be the easiest to build.
  • Read and become familiar with the Tripoli and/or NAR High Power Safety Code(s)
  • Get familiar with and use expendable motors before jumping into reloadable technology.
  • Join a high power club if possible (local Tripoli prefecture or NAR section).
  • Be very careful of the construction differences between model and high power rockets. You HAVE to build higher power rockets to be more sturdy than model rockets.
  • If not already a member, join one or both the NAR and Tripoli.

Q. What are the major differences between model and high power rockets, besides size and engines? Are they built differently?
A. Above and beyond all else, high power rockets are built much stronger than standard model rockets. This is due to the higher speeds and acceleration achieved by these models. Some of the construction differences are:

  • High power rockets have stronger, thicker body tubes.
  • They have MUCH stronger engine mounts, bonded using epoxy rather than white or yellow glue.
  • Engine mount rings, adapter rings, etc., are typically made from 1/8″ or thicker aircraft plywood, fiberglass, or phenolic sheet, rather than paper or balsa.
  • Fins are typically made from plywood, fiberglass, phenolic, or waferglass, not balsa; Thick balsa fins have been used on H and I powered models, but they have to be reinforced with fiberglass/epoxy laminate.
  • Fins are often mounted into slots in the body tube with “Through The Wall” (TTW) mounting. Most common and recommended method is glued TTW and directly onto the motor tube.
  • Parachutes are larger and typically made from some type of fabric such as rip-stop nylon (plastic chutes are not strong enough, usually).
  • Heavy tubular nylon cords or Kevlar shock line are used rather than rubber for shock cords, and these are typically attached to the motor mount or a bulkhead via quick link to a U-bolt.
  • Positive motor retention systems (clips, bolts, etc.) are important, as HPR reload casings start to get pretty heavy and expensive.

Q. I’ve heard that you have to be certified to fly High Power. How do I get high power certified?
A. There are two organizations in the U.S. which may certify you to purchase and use high power rocket motors. These are the National Association of Rocketry and the Tripoli Rocketry Association. Note that you must be a member of the organization to certify for high power with that organization. Once certified, both organizations recognize the certification of the other. There are currently three certification levels.

  • Level 1, allowing flights on H and I motors.
  • Level 2, allowing J through L motors.
  • Level 3, unlimited, allowing M power and up.

For details on certifying at each level see the procedures for the national organization to which you belong.

Q. What is a ‘reloadable’ motor. Are they worth the price?
A. A reloadable rocket motor is a metal cylinder with screw-on end pieces. Solid propellant and time delay are purchased separately from the motor casing, in ‘reload kits’. These kits contain all of the expendable, non-reusable materials for a single flight. The cost of the reload is significantly less than the cost of an expendable motor (when talking about F sizes and up). Quite a number of reloadable motors and reload kits are now certified by NAR or Tripoli. Refer to the approved motor lists of each organization to see exactly which motors are currently certified. For more information see the Composite Motor FAQ.

Q. What’s an FAA waiver? Which rocket flights require one?
A. An FAA waiver is official permission by the Federal Aviation Administration allowing the launching of rockets exceeding a certain size. The rules appear in FAR 101. FAR 101 is on the web, go to the FAA website http://www.faa.gov and search for “FAR 101.1”

But in a nutshell FAR 101 dictates that large and high power model rockets must notify the nearest FAA ATC facility that a rocket launch will be taking place. The easiest way to get this done is to fly with a club, because they will have done all the work for you.

Q. What are some good kits to build when first getting into high power rocketry (assuming I have all of the basic model rocketry skills)?
A. When just starting out in High Power you might want to consider these things:

  • Avoid any kit with plastic fins or internal parts.
  • Avoid phenolic tubes, thick cardboard tubes are more familiar and easy to work with.
  • For Large Model Rockets, try a LOC Graduator.
  • For a High Power rocket try a LOC IV or EZI-65.

Once you’ve built your first high power rocket, and have seen what can happen at the higher power levels then you can try out phenolic tube (stronger but more brittle than cardboard) or try your hand at fiberglassing a cardboard tube (makes it much stronger and not as brittle as phenolic).

If you have never flown anything bigger than an Estes D or E motor, you might want to try building one or more F through G kits before tackling H power and up. When you go for your certification, choose a rocket where G and H motors are the low end or mid-range power options. Going with a rocket where your chosen motor is at the high end or above the rocket’s recommended power range is more likely to fail by over-stressing the design. Bigger, slower high power rockets are less stressed and more likely to succeed. Any of the following are good certification rockets:

  • LOC Mini Magg, 38mm mount (G-I motors)
  • LOC EZI-65, 54mm mount (G-I motors)

Q. When is a Federal Low Explosives Permit (LEUP) required?
A. A BATFE permit is no longer required to purchase high power motors.  However, electric matches, which are used by some rocketeers for recovery system deployment, are still regulated by the BATFE.  However, there are kits available that will allow you to make your own electric matches, which would not be regulated.

Q. Just what is a ‘hybrid’ rocket motor? Who makes them?
A. A hybrid motor as sold for model rocketry uses a solid fuel grain and a liquid oxidizer — in the case of commercial model motors, nitrous oxide. A composite motor uses a solid oxidizer — ammonium perchlorate — mixed with a rubber binder/fuel to make a unified solid grain. (We have a page that shows some of the major features of the different types of motors.)

There are several companies currently manufacturing them commercially, Sky Ripper, Ratt Works, Contrail and HyperTEK. They come in sizes from G through O.

Advantages:

  • There is virtually no fire hazard transporting or storing the motor: without the oxidizer in direct contact with it, the fuel grain is almost inert.
  • It is also not covered by the same DOT shipping restrictions, because the tanks are DOT certified and the fuel grain poses no environmental or fire hazard.

Disadvantages:

  • Hybrids require more ground support equipment and are more complicated to use than composite solid rocket motors.
  • They are usually more expensive in the beginning due to their complex nature.

Portions of the FAQ were paraphrased from the RMR Newsgroup FAQ.

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