Hybrids 2017

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You can use regular NPT pipe with a piston for most sizes and make it easy on yourself by using a tee fitting to mount and connect your pressure sensors and gauges to. If someone is doing research hybrids I would strongly recommend going to DOT rated prefilled tanks. You can do all your research and development with known amounts of nitrous oxide and you can start at a known pressure. You can get tanks from one to twelve pound easily and are COTS equipment. If you want to research fuels and configurations a 3-5 pound tank provides plenty of data without using a lot of nitrous and you can evaluate case sizes up to 4 inches easily.

Edward
 
It's nice to see interest in Hybrids. During the litigation against the BATFE, Hybrids became very popular. After the BATFE lost the case, interest died off, as I expected that it would. I hope to see Hybrid usage continue and to expand in the future.

Dave F.
 
I am leaning toward prototype / homebrew as well. Fore & aft are both stainless. Ah well, it's a neat piece. Back on the hunt for AT.
 
Interesting... It looks like an AP grain... I wonder if there's any concern about bits falling off and clogging the nozzle... On an "O", said nozzle is probably big enough not to worry, but still...

I've tossed around trying something like that but 3D printed for a SRS 54mm motor. Not much point till I have a test stand that can fire a hybrid "right side up" though... :)
 
I'll beat this dead horse of mine again, because it bears repeating.

You are FAR FAR better off with hybrids of this size working on a better injector than you are devising a fancy grain geometry.

I have a student group I'm working with that did a fancy grain geometry with their circular port injector. They were getting ISP's less than nitrous as a monopropellant (160s-ish)

I finally got them to try an injector that was like a shower head with a single circular port in the grain. They did a test fire and the ISP from the motor jumped to 205s.

28% increase in performance from a changing the injector. And now they have an easy to fabricate grain with a circular port.

The motor above uses a single circular injector down each port to increase the surface area. I'm not a fan of grains like the above because of the chance of a sliver breaking off, but you pay your money and take your chance.

Edward
 
That's a fair point Edward, but not all of us can make injectors. I looked into having something made, but the costs are too high for sport flying. At least it is for one off stuff from commercial machine shops. Those few that will even talk to someone for jobs this small. It's just not worth their time.

Fooling with the fuel geometry is a simple matter, but as you mentioned, perhaps less useful. Or even not useful at all. It's just random musings from seeing those grains.

It's entirely possible that these smaller monotubes are as good as they are going to get. Not a lot of space in a 54mm tube to play with injector designs. Not as much fuel and nitrous to work with...

To do a shower head style, could one stick with U/C valves or do you need to switch to a more complex control system?

Unless you're offering to make me an injector? :)
 
I am leaning toward prototype / homebrew as well. Fore & aft are both stainless. Ah well, it's a neat piece. Back on the hunt for AT.

I haven't quite given up all hope of Aerotech resuming production of reloads but at some point I am going to have to consider unloading what I have. Which includes, besides the flight hardware, a 10lb tank (nearly full), fill hose, a couple of reloads, and some of the ignition kits.
 
I haven't quite given up all hope of Aerotech resuming production of reloads but at some point I am going to have to consider unloading what I have. Which includes, besides the flight hardware, a 10lb tank (nearly full), fill hose, a couple of reloads, and some of the ignition kits.

Would you consider laying the injector plate and a ruler on a scanner or taking a close-up picture? I can get the forward from RCS, but I'll have to make the plate myself.

If you do get out of AT hybrids, let me know
 
Would you consider laying the injector plate and a ruler on a scanner or taking a close-up picture? I can get the forward from RCS, but I'll have to make the plate myself.

Better, I can take some measurements using some digital callipers. After I find my snap ring pliers so I can take it out...
 
That would be awesome! If you could provide both an image and the measurements that'd be amazing.

I have been unable to turn up a single image online after weeks of occasional intensive searching. 10oz NOS bottles & the rest, no problem.

Oh, what finish are the 3-48 jet plug screws?
 
That would be awesome! If you could provide both an image and the measurements that'd be amazing.

I have been unable to turn up a single image online after weeks of occasional intensive searching. 10oz NOS bottles & the rest, no problem.

Oh, what finish are the 3-48 jet plug screws?

There is a drawing of the assembled forward closure in the assembly and operation manual . It's only a side view but that should be enough.

Finish is unknown. Just shiny metal.

All dimensions in mm.

Main diameter: 17.24
minor diameter: 9.52 (pyrovalve side)
thickness: 3.9
injector pin to injector face:9.76
injector face is 1.75mm higher than main body

There are four injector ports two of which are threaded. There an additional two threaded holes that don't go all the way through that are used to store the inserts used to plug injector ports when they aren't in use.

The injector ports are 1/16" as near as I can tell.
 
Fantastic stuff! I've stared at zoomed-in fig 19 a bunch the last month or two, but this is the most progress I've made.

One step closer!
 
If you want to a pre-filled hybrid, I've got sets of hardware and tanks from Alpha Hybrids that I'd be willing to part with. They don't use any special parts, just 4FFFF BP and pyrodex pellets to ignite.

Edward
 
If you want to a pre-filled hybrid, I've got sets of hardware and tanks from Alpha Hybrids that I'd be willing to part with. They don't use any special parts, just 4FFFF BP and pyrodex pellets to ignite.

You've already got my email address, and now also my attention :). I'm not as familiar with the Alpha gear, but I certainly intend to fix that.
 
Travis,

You make a good point - under 54mm it probably isn't worth the time trying to improve the system much. Your diameter limits you on fuel grain web thickness and oxidizer. For 54mm you can get a good injector - you have a bit of area to work with to create an injector. 75mm and up are a piece of cake and pays off in added impulse and thrust. I have a 3" N motor that wouldn't be possible without the injector to gain the extra efficiency.

You can absolutely do a showerhead injector in 54mm and up with a U/C configuration. It takes up a bit more space, and has a few moving parts, but it works very well. People often forget about HyperTek motors. They had a central fill stem and had multiple injection orifices that worked very well. There are ways that one could improve on the zip tie a rocket down aspect to keep the fill stem in.

This week I spent time with an IREC team with their propulsion and they came up with a very, very simple showerhead system for their motor. I was very impressed on the design. They won't be testing it because they are pursuing a tribrid style motor, but I asked them if I could advance the concept further and test it, which I'll probably start at the 2.5" diameter range.

Edward
 
I would be interested in seeing more info on injector designs and such. If nothing else, it's very interesting to read about.
 
If you want to a pre-filled hybrid, I've got sets of hardware and tanks from Alpha Hybrids that I'd be willing to part with. They don't use any special parts, just 4FFFF BP and pyrodex pellets to ignite.

Edward

You've already got my email address, and now also my attention :). I'm not as familiar with the Alpha gear, but I certainly intend to fix that.

The Alpha Hybrids motor system is a very sweet set-up. Worth looking into for sure!

DSC_5003.jpg DSC_5002.jpg
 
Here's a video of the 10 small scale tests we performed using a ~1 kN (~225 lbf), 4 second burn time hybrid during December of 2016! The performance varies a lot from test to test, but that is mostly due to us testing many different configurations

[video=youtube;nNzxqyBMwqA]https://www.youtube.com/watch?v=nNzxqyBMwqA[/video]
 
Here's a video of the 10 small scale tests we performed using a ~1 kN (~225 lbf), 4 second burn time hybrid during December of 2016! The performance varies a lot from test to test, but that is mostly due to us testing many different configurations

[video=youtube]Cool youtube video here[video]

Nice! Do you have any flight videos?
 
No, these were all static tests to test technologies for Stratos III, our next sounding rocket (total impulse of ~ 400000 Ns). Full scale tests of the 15 kN average thrust, 25s liquid burntime engine are expected in March. Launch is expected by Fall 2017.

A team of newer engineers (2nd year undergrad) are now planning on converting this testing engine to a flight model, while the team that designed and developed the engine (including myself) are now working on this massive hybrid, while helping out these new kids. They plan to launch somewhere this year.

If you have any technical questions, please ask them!
 
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Funnily enough, cutting the grains (~12% overall increase in average thrust). The sealant we used to adhere them back together created a lot of extra turbulence, with the consequence of increased local regression rates and mixing. You can actually hear the high-frequency instabilities due to vortex shedding in test 10!

Other than that, alumized fuels (tests 7,8,9,10) gave a significant performance boost over non-aluminized fuels (~20% increase in average thrust)
 
Funnily enough, cutting the grains (~12% overall increase in average thrust). The sealant we used to adhere them back together created a lot of extra turbulence, with the consequence of increased local regression rates and mixing. You can actually hear the high-frequency instabilities due to vortex shedding in test 10!

Other than that, alumized fuels (tests 7,8,9,10) gave a significant performance boost over non-aluminized fuels (~20% increase in average thrust)

I've also found that rougher surfaces perform better - I've used an HTPB/Powdered wax mixture that feels like a lava rock and that performs very well. 20% is approximately the figure I've seen from adding aluminum. Last year I tested the same injector and amount of nitrous oxide and the total impulse went from 9,000N to just over 11,000N.

I have seen an increase from a central circular injector to a multiple shower head injector, but as far as having the shower head swirl or impinge the results are no better than just orifices that are axially aligned to the grain.

Edward
 
three that I know of; Contrail Hybrids; RattWorks & HyperTEK

It seems that none of the three have updated their websites in ~10 years.


I'm trying to learn more about hybrids, and keep running into the same thing, lots of old/dead links.


Anyone have any suggestions for up-to-date info? Maybe a "Hybrids for Dummies" link?
 
It seems that none of the three have updated their websites in ~10 years.


I'm trying to learn more about hybrids, and keep running into the same thing, lots of old/dead links.


Anyone have any suggestions for up-to-date info? Maybe a "Hybrids for Dummies" link?

The links have not changed, as nothing new has happened since the lawsuit win of `09. What are you wanting to learn?
 
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