Hybrids For 2016

Hi there, just joined up after flying for many years.
Getting back into hybrids.
I have flown most makes and sizes over the years but I am mostly flying Contrail at the moment.
The reason I popped on here is that I have "acquired" a set of contrail Trojan hybrid motors 54/75/98
I have used the hypertek and these were going to be used as a replacement for them.
I know these motors were never certified and can find no data at all on the net.
I have emailed Tom a few times but have had nothing back (dont even know if he still makes motors)
These motors are all a single port design, whereas the other 75mm motors are multiport.
Just wondering what the injector side for each motor is and what impulse they would be.
The tubed I have are
1/4 for the 75mm?
5/16 for the 54mm?
3/8 for the 98mm?
Any info please as I don't want to launch a large rocket with an under powered motor.
I am guessing these will be a long burn low thrust motor with having the single injector.
Thanks
Colin

majordude said:

Wow! I've never seen a clustered hybrid! Pretty bad assed!

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This is a cluster!
6 O6300 STAGED 4 Motors to 2 motors

Rocket_Col said:

I know these motors were never certified and can find no data at all on the net.

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I have a set of docs I imaged. Unfortunately they are individual pdfs that have the text imaged. In other words the TRF upload process won't allow them to be attached to the post as they are too large. If you have a suggestion as to where to post them I can do that. Else I can send via personal email. I too have a Trojan 98mm motor that I hope to fly some day. I would also be interested in acquiring a 75mm Trojan if you know where I can get one.

StanO

Rocket_Col said:

This is a cluster!
6 O6300 STAGED 4 Motors to 2 motors

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Can you share more info on this? Where was it flown? It's a little hard to understand what i'm looking at in the picture, other than something way more complex than I can do

StanO said:

I have a set of docs I imaged. Unfortunately they are individual pdfs that have the text imaged. In other words the TRF upload process won't allow them to be attached to the post as they are too large. If you have a suggestion as to where to post them I can do that. Else I can send via personal email. I too have a Trojan 98mm motor that I hope to fly some day. I would also be interested in acquiring a 75mm Trojan if you know where I can get one.

StanO

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I have approached Tom Sanders of Contrail a couple times and asked about the Trojan line-up, and although he stated he had plenty of inventory, he always steered me away... so how did you come by the 98mm hardware? I would love to see images of Trojan goodies. I believe in Europe, the hardware came with standard tubing style tanks, instead of the available HyperTEK tanks.

I guess I don't understand something here, if Contrail has plenty of stock why don't we ever hear anything form them? I though they were out of the rocket motor business.

djs said:

Can you share more info on this? Where was it flown? It's a little hard to understand what i'm looking at in the picture, other than something way more complex than I can do

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Looks like the lovely Robin Reliant Shuttle
[video=youtube;pJdrlWR-yFM]https://www.youtube.com/watch?v=pJdrlWR-yFM[/video]

Reinhard

DRAGON64 said:

I have approached Tom Sanders of Contrail a couple times and asked about the Trojan line-up, and although he stated he had plenty of inventory, he always steered me away... so how did you come by the 98mm hardware? I would love to see images of Trojan goodies. I believe in Europe, the hardware came with standard tubing style tanks, instead of the available HyperTEK tanks.

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I'm pretty sure it was Tom I talked to. I told him I was buying for EX. So he sold me one with one reload without an N2O TANK. This was about 4-5 years ago. Perhaps he was worried about liability as they weren't certified. Also I started documenting what I could find in the attached Excel. It has thrust levels, etc. Data I captured about parts at McMaster-Carr are years old. I have no pictures in documents except in the manual I copied which is too big to attach. Ooops, the Excel is too large also. Do you know where I can store the file then link to it?

StanO said:

I'm pretty sure it was Tom I talked to. I told him I was buying for EX. So he sold me one with one reload without an N2O TANK. This was about 4-5 years ago. Perhaps he was worried about liability as they weren't certified. Also I started documenting what I could find in the attached Excel. It has thrust levels, etc. Data I captured about parts at McMaster-Carr are years old. I have no pictures in documents except in the manual I copied which is too big to attach. Ooops, the Excel is too large also. Do you know where I can store the file then link to it?

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If you do not already have an account, you can get one, and then upload the files into the file section of this Hybrid Rocket Motor yahoo group:

https://groups.yahoo.com/neo/groups/hybridrocketmotors/info

I talked to tom a few months ago, Contrail is in business and supporting the contrail hardware he sold.

Mike k

Here are pictures of a bisected grain after firing. The motor is 3" diameter, 10 pounds of nitrous oxide. The grain is 18" long, uses 2.5" SCH 80 PVC as a liner, turned down to 2.74" OD.


This is approximately 9-inches of the grain near the nozzle. You can see the squish of the PVC that happens during operation. I typically only see this on flight motors.

This is a detail of the nozzle end. Things get a bit toasty.

This is just a close up of how the PVC is left after firing. Insulation is still there even after 10 pounds of nitrous oxide.

Edward

Dragon64, thanks for the suggestion. Docs are now at link below.

https://groups.yahoo.com/neo/groups/hybridrocketmotors/conversations/messages/9252

I'll work on getting some pictures.

Cheers,
StanO

Here is a picture of a simple U/C style injector that I use. Diverges the stream of nitrous oxide well.



Edward

DRAGON64 said:

Not at all, with anything new we need to make sure the alarms are in place. One thing I will point out, 3D printing is not very cost effective for me at the moment, as these 2 grains cost me $26 with all of the fees and tax. The original reloads from SkyRipper cost $29, which included (3) of everything: all tubes, fittings, starter grains, and fuel grains. Granted, SkyRipper is no more, and having this option is far better than nothing at all. If this works out well, I will look into getting a 3D printer of my own... Lord knows I have enough assets laying around that I could sell something to fund it.

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Hey there, I'm getting back into rocketry and would love to get my SRS motors running again. I also happen to own a 3D printer and can make ABS prints for these all day long, crazy cheap too, I make my own filament so ABS runs me about $2/lb. If you need some for testing and such, let me know. The printer has some available time, I imagine a 38mm grain would probably take an hour or less to print, and I could make a few at a time.

38mm would be good, I would think that 54mm would be highly sought after as well...

I have found that 54mm grains for SRS are much easier to subtractive machine that additive manufacture. I made clones of the grains and it came out to about $2 per motor. The harder part to find is the paper liner and phenolic washer.

Edward

I saw the STL files, I'll download them and give them a go. I don't have a static testing setup though. I could take them to an EX launch, once I get my TRA membership renewed.

I'm also kind of curious about adding stuff to the mix eventually. Metal powder is pretty easy to add to filament, drives the cost up some though. What I'm not sure about is if there's a reason to bother. I know you can make various effects with solid motors that way, but hybrids are a little different and I haven't quite worked out all the details of how the combustion works in them. So unless an expert thinks it's worth messing with, I'll stick to pure ABS for now.

I own the 38mm set and the long 54mm motor. I don't have any 29mm stuff to test with, but if I have files I can print grains for people that want to test them. I don't have the printer capacity to manufacture them for sale or anything, but helping prove out the designs is worthwhile.

AlphaHybrids said:

I have found that 54mm grains for SRS are much easier to subtractive machine that additive manufacture. I made clones of the grains and it came out to about $2 per motor. The harder part to find is the paper liner and phenolic washer.

Edward

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Thanks for the info Edward. I think you are likely right about it being easier to machine them, but I suspect people will be more likely to have access to 3D printing than CNC milling. Of course, since I have one in my house that's easy for me to say... I guess I could be way off base.

Good point about the other parts. For the washer, I would think we could get close with a hole saw then stack a bunch together on a drill press with a sanding block to get the OD right. Obviously, we could print those in various materials, but I worry that the printed parts might not be able to handle the forces involved. For the liner, would casting tubes or liners used for AP grains work?

The 38mm and 29mm reloads are simple PVC or Polypropylene pipe with the ends machined to accept the nozzle and injector. Those shouldn't be 3d printed as the raw materials are very, very inexpensive.

The cost of the washer isn't that much, buy you have to buy in a quantity to make it worth it. I'm sure you could find sheet that would work and cut them out. The liners are custom - Todd had them made to his specifications. They are thicker than traditional liners use for AP, and are made of just paper. I'm sure you could convolute wind them.

Adding things to grains is certainly possible, but typically done in a liquid binder instead of a solid plastic. I have had people cast soft rubber grains that had 25% aluminum added to them.

Edward

I was pretty sure the 38mm were PVC pipe. I think some of mine had the writing on the side of the pipe still. The STL models being posted made me doubt that though. So one could make grains with a PVC cutter and a drill press. I'm sure a lathe would be more accurate though. For those, perhaps the thing to do is make a good jig for boring them. I have a few unused reload sets, I'll have to break out the calipers and see what's what.

Rubber with aluminum, interesting idea. Cast the grain like a solid motor without the AP then? That could be an interesting option to explore, particularly for the 54mm since the pipe grains are so cheap for the others... Is there documentation on the results of different additives in hybrid designs? I'm in the EX forum here, so if we get too far into the weeds on that feel free to direct me to threads over there. I've read a lot of info about various effects with solids, but it doesn't seem many are that interested in hybrids.

What's the paper liner doing here, thermal insulation? Prevent the hot grain from melting to the chamber? I know it could act as a fuel source in a hybrid, but I doubt that's the intended purpose here.

The paper liner is thermal insulation - keeping heat away from the casing.

You can add a lot to hybrid reloads.

Here is a good reference:

https://www.amazon.com/dp/1563477033/?tag=skimlinks_replacement-20

For these U/C style hybrids the largest increase in performance can be had that is easy is from the injector style. Nitrous going down the middle doesn't have the largest surface area to react with the fuel, especially when it is a hard plastic pipe. I will give you an example - I'm working with a university team that had a single, center injector. They were seeing and ISP of around 160. They changed to a showerhead style injector and the ISP jumped to 215.

Edward

Thanks! I have Terry's book on the list for if I decide to make solids, but I wasn't sure about hybrids. I'll have to see about getting a copy before I do anything significant with materials. I'd like to get more in depth knowledge on the actual science of the motors before modding them too much.

Good point on the injector. I assume it's just easier to make single hole injectors and that's why they are so common in hobby motors. And I'm not sure how one would control the flow of N2O in a showerhead style. Burst disk? It seems like it might be worth trying some things with the 54mm, gives more room for that sort of thing. I don't suppose you want to make some U/C injectors? Or supplying some of those nozzle style injectors you pictured above? That would probably work in the 38mm as well.

U/C injectors are because it is a very ingenious fill/fire method. Fill the motor, fire by melting through and you don't have any moving parts.

You can do showerhead injectors that are U/C - but they have more moving parts. I don't do any special style of U/C injector under 75mm. The main reason is that the core of your grain is too small on 54mm and 38mm to make it worth that size. 75mm is the smallest where I use a showerhead U/C style injector. You can do multiple tube U/C style injectors, but making sure they all burn through at the same time can be hard.

You can do a showerhead injector in any size if you use a pre-filled oxidizer tank hybrid. Burst disc systems are more complicated, quarter turn plug valves using servos are simpler. You have a much higher mass penalty with pre-fill systems vs U/C fill on the pad.

Edward

Is there any interested in a limited run of true 3.00" x .125" wall x 60" long U/C hybrid motors. They would hold ~6 pounds of oxidizer and have ~200lbs thrust. Simple SRS U/C style valve (flipped compression fitting with injector orifice) and a PVC liner where you could cast your own fuel in. I don't have access to a lathe that can turn snap rings in 60" tubing, so these would use dowel pins for retaining the closures.

Cost of the motor would be ~$250, and would come with a print of the liner dimensions that you can have your buddy with a lathe turn for your, or I would provide additional ones up front. The motor would be strictly for research launches, non-certified.

Edward

AlphaHybrids said:

Is there any interested in a limited run of true 3.00" x .125" wall x 60" long U/C hybrid motors. They would hold ~6 pounds of oxidizer and have ~200lbs thrust. Simple SRS U/C style valve (flipped compression fitting with injector orifice) and a PVC liner where you could cast your own fuel in. I don't have access to a lathe that can turn snap rings in 60" tubing, so these would use dowel pins for retaining the closures.

Cost of the motor would be ~$250, and would come with a print of the liner dimensions that you can have your buddy with a lathe turn for your, or I would provide additional ones up front. The motor would be strictly for research launches, non-certified.

Edward

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I would have interest. Could you post a bit more on the closure/pin design?

There would be 12 evenly spaced dowel pins around that would fit into a ring that holds the closures. On the forward end, the pins are held in by the forward closure and a wrap of tape on the outside On the nozzle end, they go into a larger ring that the nozzle passes through. There is also another ring on the outside to act as a thrust ring.

If I could find someone locally that could reasonably turn snap rings, I would. The quote that I have currently for turning three grooves (snap rings plus thrust ring) is $50 a tube.

Edward

Out of curiosity, I pulled out a poly grain for SRS 38mm. The closest drill bit I have is 1", but it's a bit big. Anyone know what the exact size to get is? It actually looks like 24mm would be a good match from the measurements I took, I don't have any metric drills that big though.

I'll measure tonight, but I'm sure it is a bore based off of the forward closure dimension and o-ring rather than a drill bit size.

Edward

My google-fu is failing.... I want to add a vent sensor to my hybrid GSE. It looks like it could be as simple as a thermistor that you wire to an analog input and watch for a sudden temp spike. Am I missing something here?

I measured my 38mm grains and the step is 1.000" diameter x .675" deep.

Edward