A semi-outsiders view...

What exactly is wrong with current hybrids?

The Hypertech M hybrid has an intial thrust of about 400lbs. With the large tank, it has 10098ns of total impulse.

I've talked to Anthony Cesaroni, and they do have other larger hybrids, but they are for commerical and military applications. Cesaroni doesn't have any interest in certifiying anything larger due to lack of demand. Anthony indicated it would cost about $40,000 to bring out something larger for the rocketry market.

Brian Elfert

In High Power Rocketry, nothing beats the cost vs. performance of a hybrid. Period. A Rattworks M class reload is $80... and the NOS required can be had for less than $20.

You can use wax, good stuff, but the additives and processing needed make it 'hold' without being brittle are a pain in the butt.

R45 works well with hybrids as is... so does Polyethylene... available at McMaster Carr in up to 5 inch diameter rods! We're talking O-P motor!!!

You can dope R45 with an oxidizer to improve the ISP if you wish... or dope it to make a 'fireworks' sparky (Red, White, Blue Flame) motor if that's your thing.

No, Scott... the simplicity of the Hybrid and the floating bulkhead makes this the rocket of choice of Amateurs... build it yourself with DIY Purple... very simple.

Composites are still fun, don't get me wrong.

The only draw back is the Ground Support Equipment required.

But if you're launching smaller hybrids it's a piece of cake to fill your NOS beforehand with Bobs 12 and 20 oz DOT rated bottles! GSE is all but eliminated!!!

Same with plastic, which is what other hybrid systems currently use.

What about ignition? Also, how expensive and bulky is the GSE?

Um Scott... Hybrids offer better performance than do solids. In a nutt shell, the order of Specific Impulse performance starting from lowest to highest are as follows:

Solids - Hybrids - Liquids.

Goddard discovered this waaaaaaaaaay back in the 1930s. So I am a ... ah never mind ...

There's actually a considerable degree of overlap,

-dave w

VAriants on paraffin make far superior fuels than, say, polyethylene (granted: that's basicaly a very long chain wax) and plexi. This is due to improved burn rate and mixing... higher thrust and greater Isp potential out of a smaller motor.

That can be done any of a number of ways, anything from a small butane source (available at hardware stores adn the like) hooked up to a stun gun to make an internal torch, to a small (way less than 65 grams) solid propellant gas generator, to black powder.

Depends on how into it you want to get; do you want to have your own NOS tank that you fill up niow and then, and then transfer N2O to the vehicle just before flight (call it $500 to maybe $1000, depending on details), or do you want to stop by the "Supershops" or equivalent on the way to the launch site? If the latter, your GSE need not be much more - if any more - than what you'd have for a solid.

Yes. But the commercially available hybrids fall far short of *their*

Can you shed some light as to why it would cost so much to produce larger hybrids for the hobby market?

You could use a leakless tank but it would not be DOT certified.

However I do believe non-commercial users are EXEMPT from DOT regulations entirely.

So the manufacturers have been unnecessarily self-limiting.

Jerry

Nothing about that is difficult. NOS tanks can get up to a few gallons in capacity... if this isn't enough to fill up your rockets, then you're way beyond the average model rocketeer...

This wasn't the production cost of rockets, this was the setup and labor cost estimate to go from blank sheet of paper to heavyweight teststand motor with at least several firings under the belt. Remember, this was an Honeast To God Aerospace Firm with boatloads of overhead, and developing new hybrid fuels.

The expectation was that at least initially (after the propellants had been proven in the heavyweight motor) we'd get some COTS high-power aluminum amateur rocket cases (I believe they were Aerotech cases, the biggest available) and convert them into hybrid combustors, with new injector heads, graphite nozzles and phenolic mixing plates. These we'd fly a few times to gen up some interest upstairs at corporate, and then go to carbon fiber combustors.

But then the company fell to bits, and that was that.

AT used the same tanks that paintballers use, which are apparently acceptable by DOT.

Bummer.

Indeed.

As they say, s*it happens. When I get settled in my new digs (Woo hoo! I'm finally gonna leave this craphole of a third-world state!!!), I just make take a stab at doing this little project on my lonesome. Might irritate the neighbors, though...

The problem with the "wax hybrid" approach is that, to a first order, producing grains will be roughly as labour intensive (and thus expensive) as solid composites. Any process that involves casting fuel grains will be more expensive than an extrude-and-machine approach, or an injection-moulding approach. The higher price of solid composites is only marginally a result of ingredients cost, and more a result of the crude labour involved. I have witnessed propellant production operations, and it's very far from completely automated.

Several current hybrids use OTS materials (IPS schedule plastic pipe) that undergoes a light machining, and then it's ready to burn. Leveraging the massive economies of scale of plastic pipe manufacture is a distinct advantage when selling into the hobby market, which is price sensitive.

Hypertek fuel grains are injection moulded, which has a much higher startup cost, but producing them is (I imagine) quite cheap.

Both Propulsion Polymers and West Coast hybrids have an entirely non-pyro start sequence, as does Hypertek (the details differ, but the end result is the same--no LEUP required for ignition supplies...).

Having pre-filled flight tanks comes with a downside--the tankage must be DOT rated, unless you plan to travel entirely on unassumed roads the entire way between the speed shop and range. No, I didn't think so. DOT rating comes with a mass penalty that could easily outweight any improvements in Isp from funky new combustor schemes...

Untrue. I made several wax test grains in my kitchen using nothign other than an electric hot-pot, a stick and the basic materials. Mixing HTPB/Al powder and AP would be considerably more complex, not to mention spookier. The hot-pot at one point overheated, and the wax caught fire; problem was solved by turning it off and putting a plate over the hot pot - work then continued. This would not be possible with solid fuel.

Any process that involves casting

So, extrude your wax propellant. or cast in large billets and machine to shape... save the shavings, melt down and start again.

Yes, but again, the performance blows in comparison to what it could be. Rocketeers are willing to pay for performance. Does an N motor cost more than a B?

Then NOS tank in the car and fill the rocket at the pad seems the better approach.

The one thing lacking today is something CERTIFIED for the smaller rocket market. Something that can be flown for MR/LMR sized rockets. I'd buy one today if it were available.

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

I'd be interested in anything say D-G. I want something I can fly at a regular NIRA launch. Which means it's got to be certified, and flyable under

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

Product liability more then anything else. major cost to sell these certified to "consumers" in the mid power market would be the huge liability insurance for the corporation making them.