Are hybrids always HPR?

Hi Kevin.

as far as the FAA notam issue, being a model rocket engine is not part of the issue. rockets are flown with H128s all the time under FAA Notams.

I believe you would need to weigh the oxidizer, and you can wiegh a PVC fuel grain before and after firing and add to that figure.

determine if the weight exceeded 125g.

we might want to Google on this, as this topic was discussed about the Ratt H70s a few years ago.

If it specifies fuel, I would not consider oxidizer (nitrous oxide) to be part of the 125g restriction.

Of course if someone asks them, they'll probably get confused and say oxidizer is part of it.

FAA only cares about initial propellant mass, not certification.

-Fred Shecter NAR 20117

THere's a good chance that the manufacturer has the info available.

Is that what the regs say?

kevin: No Hybrids aren't always HPR...The skyripper G motors fall into a regulatory black hole, ie there are currently no regulations that apply to a "model rocket" power size hybrid..... The only requirements that I am aware of concerning G hybrids are you must be 18 years of age for purchase, because G size motors require a person to be 18...

This G hybrid an another example of technology outstripping the regulations...

and yes you could throw up 3.3 lb G hybrids all day with FAA notification as a LMR , as its not just the fuel weight or type, its the overall weight (ie 1500 g/3.3ln/53oz) that makes it a LMR....

I wouldn't doubt that you could put this G hybrid in model rockets that weight less than 16 oz....

shockie B)

Hmmm, so NEITHER the N2O or PVC count towards the 125g limit.

BTW, how do you handle check-in for a hybrid? When you weight the model, you're not getting the N2O weight.

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!

Interesting claim. Care to "live the lifestyle" or worse, "get a ruling"?

Jerry

The NFPA 1127 definition of "propellant" covers "the material(s) utilized in a rocket motor that produces thrust by the discharge of a working fluid generated by combustion, decomposition, change of state, or other operation of such material contained within the rocket motor." So, I think, you need to count the nitrous and whatever portion of the fuel grain got consumed...

I couldn't f> >

...

But it does exclude delays and ejections in calculating mass.

Jerry

you need to get the before weight and after burn weight of the fuel grain. this gives you the fuel weight, as part of the grain is structual, and not fuel.

you don't count the total grain weight, just what gets burned in the process.

you only count the burned portion of weight. other functions of the fuel grain is structural.

It is never "propellant". Except possibly the combustion itself.

Just the burned.

That is payload. So could you run a 500g ingredient load, but only convert 125g to propellant?

Or in the case of a ramjet, carry a 125g fuel load but receive 2000g of "free" oxidizer in flight.

Jerry

Now if only you could combust 90% of that structure :)

add more oxidizer.

There comes a point where you melt the casing! On big motors like the Hyperion some of the fuel mass is actually the combustion chamber liner burning too.

Also remember that in a floating-injector hybrid, the fuel grain has to support the force exerted by the nitrous (at 750psi nominal at the start of the firing) on the injector bulkhead.

Keep in mind that total liftoff weight has to be below the notification limit, as well, and that DOES include the oxidizer.

-Kevin