Small and Simple Hybrids are Possible

I noticed a thread talking about how hybrid motors could be scaled up.
. Nothing wrong with that, but I think the real challenge is to
make efficient small hybrids and make them less expensive and easier to
work with. The G and H region is what needs attention, in my view.
There's a Yahoo group called "microhybrids" with info about motors
using tiny, disposable, 8-gram cylinders (or bulbs) of nitrous oxide.
If you've ever seen the little 8-gram bulbs of liquid CO2 used to
charge up soda fountains, or the 12-gram bulbs used in airguns, you
have the idea. It appears that the little nitrous bulbs are used in
some manner to make whipped cream. When used in rockets, they produce
about high-D to E power. (Here's the group, by the way:
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)
There are some shortcomings. . . The bulbs are too tiny, we need
something with more juice. The total impulse is right in the area
where composite or even black powder motors are inexpensive and easily
available, so some will ask what's the point? And the bulb requires a
hardware mechanism to support it and hold it tightly sealed against the
injector assembly, which increases the size and weight.
If we could get a larger disposable cylinder manufactured with a
threaded neck, it could solve a lot of problems. At least one company
is already making such a cylinder filled with CO2, for use in air
rifles or paintball guns:
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That holds 88 grams of CO2. So if we had these filled with nitrous,
that could put us up into the realm of H motors, at a rough guess. The
threaded neck raises the prospect of a hybrid motor that you simply
screw together and launch -- no need to transfer liquid nitrous between
tanks.
One other nice thing about disposable bulbs is, the walls don't have to
be made extra thick to withstand multiple fill-and-empty cycles (and
the resulting metal fatigue as years go by), so they can be lighter
weight. They can also be filled more precisely at the factory than
anybody fiddling with a set of scales at home could do, so you *don't*
need to leave as much empty space in the bottle as a safety factor
against over-filling it. That should allow them to be somewhat more
size and weight efficient than current hybrid designs.
Reply to
Tony Belding
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Ratts and SkyRippers cover H real well already.
If you want a "G", you could get them to cut the H70 Ratt tank down. I don't think they make a G Ratt, because the market for it is not their, and the whole problem of consumer vs hpr hybrids.
Hybrids tend to have a lower average impulse. They also have more weight due to tankage.
Scaling up makes economic since. Scaling down makes them weight too much. Also, cost and time consuming to work with compared to $3 "D" engine the micro hybrids tend to be the same impulse as, but weigh more.
I would ask that you ask Marcus at PP about the 22mm market and why it does not make economic since for him to sell his 22mm motors he has. He has them, so why does he not sell them ?
Reply to
almax
There used to be a 12" version :)
I have some :)
Reply to
Jerry Irvine
Try more like C to D, with a motor twice the weight
hmmm, seems most people think that in order to improve a motor, give it more fuel. the Microhybrids have plenty of other areas to increase efficiency (like weight for one)
they have small threaded tanks, last I heard was that somone was going to make a mostly plastic casing to reduce weight.
reducing safety factr aint gonna make some people happy, unless you can back it up with thousands (millions) of safe flights.
then there is the fact of no ejection system. not an issue for saucers or gliders (ask art applewhite!)
Reply to
tater schuld
I was merely repeating what I saw posted in the microhybrids group, or on a page linked from there (I don't recall exactly). I've never owned or tested any of them.
I'm aiming for the "regulation gap". If composite motors in the upper-G impulse range and higher are restricted, and most available hybrids are J and K -- not to mention expensive and awkward to work with -- then there's a gap in the G-I area that stands to be filled. That's where I'd like to see it fall. (And yes, I'm also aware that the regulations are going to be revised again. We'll see how that goes.)
I never said reduce the safety factor. I was trying to say a disposable tank should allow us to reduce the thickness of the tank walls and fill it to a higher percentage *without* reducing the safety factor. Although it hasn't been done with nitrous (that I'm aware of) beyond the tiny 8-gram bulbs, this is a technology proven with liquid CO2 as far back as the 1940s -- when they were used to inflate emergency life rafts, I think.
Electronic ejection is cool anyhow, and simple timers don't cost that much.
Reply to
Tony Belding
Tony,
I don't see the same 'gap' that you see in the H-I hybrid motor line...
Hypertek makes a few different 54mm I motors, RATT works has 3 different 29mm motors in the H/I range. For 38mm, WCH has a G and H motor (Not certfified yet, but soon), and an I motor. Propulsion Polymers has a H motor, and two I motors, and Sky Ripper Systems is soon going to market with one H motor and four I motors for 38mm. I have been toying around with a 29mm G also...
As far as a 'gap' in H-I motors, I don't see it. There are many options out there, and by mid summer the pool just gets more full.
One reason you are likely not going to see any G motors is due to expense. Hybrid hardware is pretty expensive. Scaling it back to smaller total impulses doesn't really change the price that much. So, if a 29mm H motor is 70 bucks, a 29mm G motor is going to be about the same... A 29mm F motor, about the same... a 29mm E motor...etc.
Marcus' 22mm motors look very cool, and I do hope he goes to market with them. It would begin to fill the mid-power hole, but I'm not sure how many people will be willing to invest in the hardware. I would imagine it's going to be expensive as compared to solid hardware in the same size range.
Todd
> > reducing safety factr aint gonna make some people happy, unless you can back > > it up with thousands (millions) of safe flights. > > I never said reduce the safety factor. I was trying to say a > disposable tank should allow us to reduce the thickness of the tank > walls and fill it to a higher percentage *without* reducing the safety > factor. Although it hasn't been done with nitrous (that I'm aware of) > beyond the tiny 8-gram bulbs, this is a technology proven with liquid > CO2 as far back as the 1940s -- when they were used to inflate > emergency life rafts, I think. > > > > then there is the fact of no ejection system. not an issue for saucers or > > gliders (ask art applewhite!) > > Electronic ejection is cool anyhow, and simple timers don't cost that much.
Reply to
Todd Moore
Actually, so does PP. We have had 4 38mm motor combinations certified since 2002, covering 'H' through 'J'.
Because I have yet to receive enough committed pre-orders to justify a production run, and the substantial certification costs. The 22mm motors are cute, and they compete quite favourably in the weight area with the microhybrid approach. That isn't enough to cause people to order them in droves. A 22mm set covering 'D' through 'G' range would include 4 motor tubes, an injector, tank-end closure, nozzles, a bunch of flow-control orifii, and the necessary snap-rings. The MSRP would be in the $300 range, and it would use existing GSE to fill and fire.
Reply to
Marcus Leech
Don't those micro hybrids use steel N2O tanks??
RDH8
Reply to
Robert DeHate
Why is that? What's the big expense?
The fuel grain shouldn't be expensive, it's just plastic or paper. The casing -- if it even needs one -- should be similar to what we already use with solids. The disposable nitrous tanks shouldn't cost much (although the per-flight cost would be higher than a reusable tank that gets flown many times). Is it just. . . what, the injectors? I dunno.
Reply to
Tony Belding
The material itself is cheap, but it takes time to make the grains, and that's the expensive part, especially if the source material is too far off what it needs to look like.
-Kevin
Reply to
Kevin Trojanowski
Well, Check the cost of a RATT H70. Now, cut it down by 5" or so. Now it's a G motor. How much less does it cost? It has all of the original internal parts, but it's only 5" worth of tube less expensive to make. That isn't very much, I can tell you. Even scaling down the size from 29 to 24 mm... Still have to cut and face a tube, add ring grooves or threads. Still have to make a bulkhead. Still have to make an injector, Nozzle... that 5mm smaller piece of stock your are using isn't really a factor. The raw aluminum material used in 24~38mm motors doesn't differ in price that much. It's really all about the cost of machining, and a 29mm injector takes about the same number of machining steps as a 24mm one does.
Hope this makes the hardware expense issue clearer...
Ahh.. Ok. With the disposable nitrous tanks, you are only going to get a D impulse motor. There just isn't enough oxidizer there to get any more. Soo, if that's what you are talking about, look around at the micro hybrid hardware that is already out there, and tell me what you find in regards to a cost. I'll give you a hint; It's expensive ;) There is also a problem with reliable ignition. I built my micro hybrid, and failed 4 out of 6 times to get ignition.
If you are serious about this, I have designed a totally plastic injection molded micro hybrid, that cuts the weight down to just a little more than a D12 when fully loaded (from memory.. Haven't worked on it for a while).
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I was looking into doing this project, then I decided that I had other things I should be messing with. If someone wants to actually follow thru on this, contact me and I'll be happy to talk over the design with you. I am a plastic injection mold maker, so I have a 'source' for economical tooling... Anyone want to get into the exciting business of rocket motor manufacturing? ;)
Todd
Reply to
Todd Moore
On this, we can all agree. Particularly in a niche market in which the required quality and tolerances are very close to "aerospace grade", but the pricing tolerance of the end users is "hobby/toy".
The repeated refrain "but it's just a chunk of machined aluminum" burns my a$$. Most of the products we hobby aerospace manufacturers make could reasonably be sold into the "real" aerospace market for 3-5 times the MSRP we're charging into the hobby market. It's just a good thing that most of us in the business have real jobs as well, or our families would surely starve...
People like Dave Griffith have a bit of an edge, since they own?/operate a "captive" CNC machine shop which can produce the hobby product during "idle" time in the shop. Todd is placed in such a way that his access to cheap injection moulding tooling could allow him to produce these funky microhybrids without the usual tooling costs for such an endeavour. They can both partially leverage their "day job" to support the hobby manufacturing end of things.
My "day job" is hopelessly unrelated to aerospace or hardware manufacturing. Which means that I have to pay "fair market value" for machining services, etc. Although most of the prototype work I do myself using access to a highschool machine shop.
A sober end-to-end business review of most small hobby aerospace manufacturers would put them on the edge of being "charities" rather than businesses...
Reply to
Marcus Leech
This should be in the FAQ.
Near the top.
Jerry
Past the edge.
Reply to
Jerry Irvine
And I would like to add my thanks to all of the folks who do this for love of the hobby (though I'd love for them to be successful enough for it to be 'real')!
David Erbas-White
Reply to
David Erbas-White
You have seen how much resistence there is for even the most basic and obvious of club policies that would further that goal.
Sadly it is not in our immediate future.
I would gladly chair a committee to modify club policies to return growth and tolerance to sport rocketry.
Please bring common sense back to rocketry administration.
Jerry
Reply to
Jerry Irvine
OK, Jerry, here's the challenge to the community.
Which manufacturers out there, other than Jerry, believe that the difficulties that they are having with growing their business in this hobby is due to the 'club policies'. Please state who you are, what you manufacture, and what specific changes would need to be made to CLUB policies in order to facilitate your business.
David Erbas-White
Reply to
David Erbas-White
Direct from the horses mouth. ;)
Reply to
Alan Jones
Yeah, but making it a "club policy" to ignore the ATF and DOT; and permit shipping of unclassified hazmat as "model aircraft parts", really isn't a good idea.
Reply to
RayDunakin
When are YOU going to get past it?
The LAW got past it in 1972 ish.
27 CFR 555.141-a-8
Jerry
Reply to
Jerry Irvine
Jerry wrote:
This isn't about the law, nor is it about TRA/NAR. It's about the ATF. Get your facts straight and quit trying to turn everything in a "TRA/NAR vs Jerry" issue.
Reply to
RayDunakin

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