Hybrids 2017

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2 minute sounds about right for my Contrail M +/-20 seconds or so. ALWAYS seems a lot longer when you are filling.

Mike K

What is a typical fill time for the long Contrail M tank? My valved system in THRP-1 ended up right at 2 minutes (from memory; I could verify if necessary). Tank volume is similar but since mine is a chilled system it holds more mass. I'm curious how the fill time compares to Contrail's vented method?

Gerald
 
Getting ready for ROCstock next weekend at Lucerne, for hybrids I have;

Contrail M
Skyripper J
RATT J
RATT I

And possibly a RATT K

anyone bringing up hybrids?

Mike K
 
Getting ready for ROCstock next weekend at Lucerne, for hybrids I have;

Contrail M
Skyripper J
RATT J
RATT I

And possibly a RATT K

anyone bringing up hybrids?

Mike K

I'm going to have to sit this one out (busy getting ready to launch something slightly bigger if you know what I mean.) Maybe in November.
 
I'm going to have to sit this one out (busy getting ready to launch something slightly bigger if you know what I mean.) Maybe in November.

ROCstock got blown out by the wind, I do plan to try again for hybrids in July (weather permitting),

Mike K
 
Flew some skyripper clones today, in a spool fitted with a chute realease. Taped a pool noodle to the top to help protect the case. Works great !

ImageUploadedByRocketry Forum1499568360.369508.jpg

ImageUploadedByRocketry Forum1499568421.688806.jpg
 
Heh... Never considered using a chute release that way. I might have to try it.
 
I've been working quite a bit this summer on tribrids. After quite a few tests with a RattWorks clone I found out that if you size the nitrous and alcohol orifices a certain way you can get a condition where you get choked flow through them. This produces a nice nearly flat (< 2.5% difference from start to end) thrust curve until you run out of liquid nitrous oxide and go into blowdown phase. After I figured out the sizing of the orifices then I worked on using pressure regulation on the nitrous oxide flight tank so that the motor always starts at the same pressure and density. I've probably done 15 tests this summer and about to scale the motor up to a 4-inch size. I've also made some changes to the injector design on the RattWorks so that it doesn't rely on bursting a small inner tube and the motor starts almost instantly in nitrous/alcohol mode. Overall, I'm much more impressed with the tribrids because of the small combustion chamber and ease of scaling impulse up. More impulse, longer tanks. I hate to say but with less variables to deal with I'm not as excited to go back to hybrids because you have to figure out regression rate, insulation, surface area etc. With the tribrid you set those values and can count on them.

Edward
 
Very good!

So far, I've yet to obtain any nitrous (suppliers don't seem to be taking new customers around here due to the shortage), and haven't arranged for a test, so I'm sitting dead in the water at the moment. That's my status. :(

Gerald
 
Bummer about not getting any nitrous! I've went through five 75 pound bottles since the start of June this year. A nitrous surcharge did show up on my invoices, though it was small - $10.

Edward
 
yes i did get my flight in. here is a spool on a j-144. i loaned my hardware right after this flight.

spool-j144.jpg
spool-j144-2.jpg
 
Interesting, in 2008 I flew a J144 once...and only once! The recovery eyelet came unscrewed from the motor bulkhead, and the booster came in hot never to be seen again.
 
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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

Have you looked at nitrous nozzles used for 2000+hp drag racing engines? In the past nozzles were a 90deg spray. You can get straight nozzles and other angles, too. Then you can get optimal flow with replaceable jets, they come in a wide range of sizes or drill your own with precision drills.
Look at nitrous express, they have distribution blocks for multiple nozzles, solenoids, temp-controlled bottle warmers, etc


Sent from my iPad using Rocketry Forum
 
Last edited:
Have you looked at nitrous nozzles used for 2000+hp drag racing engines? In the past nozzles were a 90deg spray. You can get straight nozzles and other angles, too. Then you can get optimal flow with replaceable jets, they come in a wide range of sizes or drill your own with precision drills.
Look at nitrous express, they have distribution blocks for multiple nozzles, solenoids, temp-controlled bottle warmers, etc

Sent from my iPad using Rocketry Forum

Early on I looked at nearly every available spray nozzle for fuel oil, nitrous, etc. I tried some and found out that when you stick any nozzle or fitting into the combustion chamber, more likely than not it will melt. I've melted fittings from 1/8" NPT all the way to 1/2" NPT, brass and stainless alike. You need a robust flowrate of nitrous through your injector to provide cooling.

I tested a lot of BETE nozzles in 54 and 64mm about 12 years ago. I found that the performance difference between those and a straight orifice only ~5%. The BETE nozzles were much more expensive and melted. Injectors with fine textures almost always melt.

Currently most of my injectors are flat faced with multiple orifices drilled into them. The flat face keeps any small mass from being in the combustion chamber and also provides something more massive that stays cooler with the flow of nitrous.

Edward
 
Has anyone tried sapphire/ruby orifices, as from water jet cutters? Is there somewhere I could read up on corundum?
 
What is your goal with using them? Simple drilled orifices in brass/aluminum work.

Fittings intruding into the chamber melt. This year an IREC team melted a 1/2" stainless steel NPT fitting. It has a lot of mass, but it is easily heated because it sticks into the chamber. That gets expensive. I've flown the RATT M900 five times and I've melted the slotted injector three times. It is just a lot of heat to try and dissipate.

Edward
 
What is your goal with using them? Simple drilled orifices in brass/aluminum work.

Fittings intruding into the chamber melt. This year an IREC team melted a 1/2" stainless steel NPT fitting. It has a lot of mass, but it is easily heated because it sticks into the chamber. That gets expensive. I've flown the RATT M900 five times and I've melted the slotted injector three times. It is just a lot of heat to try and dissipate.

Edward
Idle & uninformed webforum speculation is my only goal here :)
 
I know nothing but want to fly one by the end of the year.

Hybrids sound like fun, but I need to learn the basics before I even consider flying them in the future.
It sounds pretty complicated. I'd love to see one launch though!

How about that though?
In 2017 I want to learn as much as I can about hybrid motors and see one fly!

I want to finally get my [new] K240 and K350 Tribrid in the air. My only real holdup is I don't have a rocket with a 66mm or larger motor mount.

I would so like to fly a Tribrid!

I hope to be flying my normal amount but life will tell... Going to maybe do some smaller 38mm Contrail. Been a while since I've flown smaller motors. Thinking a J800 maybe. LOL! Normal would be a 54mm 3 motor cluster Very cool on 3 J416 sparkies and I may do the two stage again. It's a 75mm to 54mm. Throw a couple of HyperTEK in the mix and I'll be a happy camper for flights in! :)

Jason

Alright guys, where are we at with these New Years stances? Are you still working towards your goals of researching, or building, or buying etc?

I'll throw this old link out one more time; it is an out dated yahoo group, but has lots of old files that are still quite useful: https://groups.yahoo.com/neo/groups/hybridrocketmotors/info
 
So I posed a question to the Hybrid Rocket Motor yahoo groups asking for hybrid users to sound off... here is a reply from Thomas Sanders, owner of Contrail Hybrids:

Contrail Rockets is going strong looking for cooler weather in Arizona so I can pour 38 HP grains.

Moving the shop this past year slowed manufacturing but all orders were filled.

Many custom projects mostly for Universities are still happening. Hoping TMT can come up with a west coast tester for some of my new motors.

I am working with an Aerospace Engineer from the University of Tennessee on injector performance he is hoping to take my 38 mm motors from 60% efficiency to 90%. Going on 2 years but will be able to crossover to other Contrail motors.

As the sole owner of Contrail Rockets I get to funnel a lot right back into product development.

Doug from Pratt Hobbies is helping update the website as it has not changed since 2008 but then neither have my prices.
 
Good to hear at least one manufacturer is still around.

I got distracted from Hybrids on my L3 project and flight. That has been successfully completed and I plan to get back to it soon. First thing to do is complete the build of the vehicle for my 54mm SRS motor. It's been a long time coming, but it's about 80%. I also need to rehab my GSE a little, but that's getting closer as well. I'm also seriously considering buying a lathe so I can make some motor parts. And because I miss making chips. :)
 
Some awesome videos from across the pond. These are posted by Colin Rowe at the yahoo group website:

[video=vimeo;223579138]https://vimeo.com/223579138[/video]

[video=vimeo;223579159]https://vimeo.com/223579159[/video]

[video=vimeo;223579169]https://vimeo.com/223579169[/video]

[video=vimeo;186265233]https://vimeo.com/186265233[/video]

[video=vimeo;234903926]https://vimeo.com/234903926[/video]
 
Contrail has expressed some interest in designing 29mm hybrids, and they are asking for a little feedback on what sizes to build, and what type of fuel to use. They have mentioned PVC, and I offered up cast or machined ABS. Anyone else interested in a new line of motors coming from Contrail?
 
Contrail has expressed some interest in designing 29mm hybrids, and they are asking for a little feedback on what sizes to build, and what type of fuel to use. They have mentioned PVC, and I offered up cast or machined ABS. Anyone else interested in a new line of motors coming from Contrail?


It would definitely fill a gap. I don't own any 29mm hybrids. I think SRS was the only ones that made one, and at the time electronics were larger and more expensive. I think it makes more sense to skip anything not HPR though, since the weight of the motors tends to create L1 G impulse motors anyway.

For fuel, I'm not convinced it matters all that much at this size. I emailed AlphaHybrids a lot about various options for fuel and grain geometry for 38s and 54s and with the size limitations it didn't seem like there was a lot to work with to increase isp. And if there is no significant benefit, might as well use cheap stuff like PVC pipe. Cast plastics have a large startup cost for the tooling. Unless they can get this cost down, I'm not sure they can make any money using that. A CNC lathe or mill could probably pump out grains from plastics pretty cheaply. Or 3D printing, but that comes with its own issues.

While I'd like to see it happen, I'm not sure there's enough of a market for them to bother with it. Hybrids are interesting and fun, but they have downsides that are difficult to overcome at a price point that makes sense for 29mm projects. GSE is a big one. It's not a big issue for an M motor, but for a H? A commercial H load is about $30 right now for APCP. One would need to fly a fair bit to make GSE costs work out, and there's N2O to deal with as well. Many clubs don't have GSE available, so you have to find a member that has it, is at the same launch, and is willing to let you use it. And in the past, Contrail loads have been the most expensive. This was, in part anyway, due to materials costs. HTPB costs a lot more than PVC pipes etc.. The only reason I mention that is that I wonder if it's a sustainable business for them. I'd hate to see them lose money on it as they are about the only active Hybrid manufacturer. There are also costs in certification and such to consider. They know all this better than I do, I'm sure, so perhaps they have considered ways to deal with it that I haven't thought of. Great if they have.

If they also offered a simple, inexpensive apogee only electronic deployment option people could put on the motor case or similar, it might help a lot. Something like what AT tried with the EFC.
 
One thought I wanted to toss out there, I have no idea how well this would work or if there would be too many possible issues with it...

GSE and the fill/fire sequence in general puts people off hybrids, particularly for small projects. I've been tossing around an idea I expect isn't new, but I haven't seen it here... What about pad-filled with manual GSE? I'm thinking the internals are pretty much the typical U/C monotube. The fill line has a ball valve close to the motor and one at the tank. The FC has a screw type pressure relief valve, think Propane tanks..

Connect up hoses, arm electronics.
Open fill valve at the bottle, quick check for leaks
Open FC screw valve
Open motor fill valve
Fill till venting
Close FC valve
Close motor and tank valves

This does add some danger as you have liquid N2O venting while you are there. Cryogenic fluids are not nice. One would have to be careful here and the possible liability might make this too risky for a commercial motor. If the vent and screw are 180 degrees apart, that lowers the risk significantly. There is also the 900+ psi pressurized motor to consider.

It also means you are present at the pad with a filled hybrid motor. I don't think it's any worse in my mind than a pre-filled type, but it's something to be aware of. Add a hot pre-heater grain and use redundant igniters to ensure ignition, and it helps with a few of the downsides of hybrid motors. I am unsure if I have considered all the safety issues though. Perhaps a more experienced user will offer suggestions here.
 
It would definitely fill a gap. I don't own any 29mm hybrids. I think SRS was the only ones that made one, and at the time electronics were larger and more expensive. I think it makes more sense to skip anything not HPR though, since the weight of the motors tends to create L1 G impulse motors anyway.

For fuel, I'm not convinced it matters all that much at this size. I emailed AlphaHybrids a lot about various options for fuel and grain geometry for 38s and 54s and with the size limitations it didn't seem like there was a lot to work with to increase isp. And if there is no significant benefit, might as well use cheap stuff like PVC pipe. Cast plastics have a large startup cost for the tooling. Unless they can get this cost down, I'm not sure they can make any money using that. A CNC lathe or mill could probably pump out grains from plastics pretty cheaply. Or 3D printing, but that comes with its own issues.

While I'd like to see it happen, I'm not sure there's enough of a market for them to bother with it. Hybrids are interesting and fun, but they have downsides that are difficult to overcome at a price point that makes sense for 29mm projects. GSE is a big one. It's not a big issue for an M motor, but for a H? A commercial H load is about $30 right now for APCP. One would need to fly a fair bit to make GSE costs work out, and there's N2O to deal with as well. Many clubs don't have GSE available, so you have to find a member that has it, is at the same launch, and is willing to let you use it. And in the past, Contrail loads have been the most expensive. This was, in part anyway, due to materials costs. HTPB costs a lot more than PVC pipes etc.. The only reason I mention that is that I wonder if it's a sustainable business for them. I'd hate to see them lose money on it as they are about the only active Hybrid manufacturer. There are also costs in certification and such to consider. They know all this better than I do, I'm sure, so perhaps they have considered ways to deal with it that I haven't thought of. Great if they have.

If they also offered a simple, inexpensive apogee only electronic deployment option people could put on the motor case or similar, it might help a lot. Something like what AT tried with the EFC.

True, GSE is a concern. Hybrids blossomed from a time when Korey Kline (developer of HyperTEK) offered free GSE to get hybrids on the market. I believe a club had to buy (5) 440cc systems, with (5) fuel grains per system to qualify. Our club jumped on this offer day one! Since the club owned the GSE, the flier only needed to buy their own hybrid system to fly. Back then we also owned the K-cylinder, and we filled every couple months or so. The club sold all of this off years ago due to lack of interest, and a need to spend the money elsewhere. Since I have gone all in so to speak, I now own my GSE and tank, and am self sufficient... and if I am flying at a launch, and you have a 29mm system but no GSE, "No Problem" I can launch that!
 
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