why are hybrid rocket motors regulated by NFPA?

So it could easily be certified as a MR motor with a reduced fuel load. However, given the different nature of hybrid vs. solids, I'd like to see the limits increased for hybrid MR motors to 4 Oz. of propellant, or to at least 160 N-s with a propellant load under 4 Oz.

The regulations were written at a time when only large HPR hybrids were seriously considered.

I'd argue that even solid MR motors are not toys. OK, hybrid motors are a bit moor sophisticated. There is nothing wrong with a little rocket science in the sport. I was not advocating the sale of hybrid motors to rocket scientists under the age of 18. The question is, would you sell a small hybrid rocket motor to a 50 year old aerospace engineer without HPR user certification?

So what else is new. ;) I think the original NFPA hybrid motor regs were essentially authored by the NAR, or NAR/TRA, with little regard for small hybrid motors.

I agree. Solids are much easier and higher performing than sport rocket hybrid motors. No terrorist would use a hybrid motor. However, a sport rocketeer might want to try the challenge, or just fly larger motors without LEUP storage.

Alan

The Contrail Hybrids are far from low performers. An I-500. A K-888. A M-2281.

I'm not familiar with the Contrail Hybrid motors. My general perception is that the sport rocket APCP motors outperform the Nitrous based hybrid sport rocket motors. I'm not trying to dis the hybrid motors. They have an acceptable level of performance. However, I'd challenge you to beat an APCP E6 or F10 in an altitude competition with a hybrid motor. I'd challenge you to break the model rocket vertical speed record of M1.42 using an APCP AT F80 with a hybrid motor, all of the same delivered total impulse of course. I agree that comparisons should be made between actual motors, rather than generalizations, but there not always suitable motors in both categories to make the comparisons. In general the APCP motors deliver higher ISP, and higher propellant mass fraction (E.g. lower motor empty weight enabling more payload to be lofted.) So far, hybrid motors have not delivered the high peak thrust or thrust tailoring of many APCP motors. It is also true that LOX based hybrid motors can have higher ISP than APCP motors...

The advantages of hybrid motors are acceptable levels of performance without requiring LEUP storage or hazmat shipping, and lower flight cost for those rocketeers who make frequent flights without losing or damaging the hybrid motor.

Alan

Ray is pretty much correct. The only thing NAR/TRA/CAR flyer certification really does is to allow you to fly at NAR/TRA/CAR sanctioned launches. It has nothing to do with the ATFE or a LEUP.

There is nothing that precludes anyone who is not a NAR/TRA/CAR member from finding a launch site, buying insurance, obtaining a LEUP & buying motors, and flying high power rockets.

DSC

We've had the discussion before about states that have adopted NFPA codes as state law. Where I live NFPA 1127 has the force of law. That means you have to have a NAR or TRA certification to fly high power. Unless you are flying for the government or a University...

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