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Voyager1

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I understand.

In this particular design I can’t have a fixed bulkhead, so I employ a multi-layered Nomex blanket on the forward end of the CR secured to the tether that attaches to the forward closure of the motor. Probably the wrong example to provide.

In my other hybrid boosters I use exactly the same technique as you have used with the fitted bulkhead at the head of the booster and a CR just below the bulkhead coupler near the top of the motor.
 

Dan Griffing

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I understand.

In this particular design I can’t have a fixed bulkhead, so I employ a multi-layered Nomex blanket on the forward end of the CR secured to the tether that attaches to the forward closure of the motor. Probably the wrong example to provide.

In my other hybrid boosters I use exactly the same technique as you have used with the fitted bulkhead at the head of the booster and a CR just below the bulkhead coupler near the top of the motor.
These are only my RockSim designs, because I have yet to launch any of the hybrid motors that I have. But its good to know that my thoughts on the subject aren’t that different from yours.

After assessing the RockSim simulation performance of the full range of Contrail hybrids for the different length configuration in 38, 54, and 75mm motors, I’m about ready to order the hybrid loads I’ll be using over the next year.

I have another question. What is the resistance of the big resistor that Contrail Rockets uses as an igniter?
 

DRAGON64

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My 98mm Contrail is 59" long, and my mount is 36" long. I plan to 3D print a ring that will steady the tank end while in the rocket, but there will be no tube installed in the ring.
 

Dan Griffing

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Contrail Rockets newest motor that has had R&D fights before COVID-19. This 54 mm motor is only 20 inches long. It has 10% more NOS than it’s 28 inch certified cousin. More importantly it’s loaded weight is 25% less. The New Black Smoke 4 inch grain has more surface area than the 12 inch grain used in the existing motor. This motor incorporates the CNVA developed to improve NOS dispersal using a vortex pattern which rotates at 1200 RPM as it exits the injector into the combustion chamber. View attachment 428720View attachment 428721View attachment 428722View attachment 428723View attachment 428724View attachment 428725
Has Contrail started selling these?

I have two 54mm hybrid rockets on my RockSim drawing board, with the kits and extra parts purchased. And because I’m using RockSim’s subassembly feature, I have separate configurations for each hybrid motor length.

So it would be helpful to know if I need a 20” motor length configuration for each RockSim design.
 

Voyager1

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I have another question. What is the resistance of the big resistor that Contrail Rockets uses as an igniter?
From memory the resistance is 10 Ohms. However, I stopped using them fairly early in my hybrid launching and use standard high power igniters embedded in a 1cm length of 24 mm or 29 mm APCP grain, depending on the hybrid grain core diameter. The resistors were intended to ignite Pyrodex pellets, but we can’t easily get them over here in Australia. This technique has proven to be very reliable.
 

Voyager1

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My 98mm Contrail is 59" long, and my mount is 36" long. I plan to 3D print a ring that will steady the tank end while in the rocket, but there will be no tube installed in the ring.
The 3D CRs that I print now are stepped to fit over the forward closure end of the motor tube. Previously I had them fitted directly over the motor tube (without any motor mount tube) just back from the forward end. In either case, they can be secured in position by screws through the airframe for ease of removal.
 

Dan Griffing

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I have my own supply of Pyrodex which I bought but didn't like using for my deer hunting muzzle loader because it fowls the rifle as badly as black powder.

I also have several different gauges of Nichrome wire and have been winding my own 1-2 Ohm dual deployment igniters using 1-2" of 32 gauge. My Eggtimer Proton and Quantum flight computers set these off quite well for BP chute ejection with their LiPo 2S 4.3V batteries.

My overall agenda is to get away from needing 24v to launch a hybrid rocket with the Contrail GSE because the normal ACP wireless systems that our club uses is only 12 volts. So if I know what the resistance is, I can back-calculate to know what current is being used to set off the Pyrodex, and either get a resistor or wrap my own Nichrome igniter to meet the requirement. Or simpler still, if a certain current is necessary to ignite a Pyrodex pellet, then according to Ohm's Law, 12 volts will need half the resistance to draw the same current.

Since I already have Pyrodex pellets, I can even test my igniters or resistors on the pellets here without it being in a loaded Contrail hybrid motor.
 

Voyager1

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Yes, the 24V requirement was a show-stopper for me , too. I have also used Nichrome wire igniters into the APCP ignition grain. I have found that even the mid power igniters are quite OK to poke into the APCP ignition grain, but you do have to extend the leads because they are far too short. I have actually used e-matches to ignite the AP ignition grain in tests. However, I want to be 100% certain that the hybrid grain starts to vaporize and burn, and the fill tube severs, so using a HP igniter has been very reliable. Having to reload a hybrid motor after an ignition failure is a real PITA!

I will pursue the Nichrome wire option further, because HP igniters are becoming ridiculously expensive. I have a 100m roll of it that cost the same as 4 igniters.
 

Dan Griffing

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Yes, the 24V requirement was a show-stopper for me , too. I have also used Nichrome wire igniters into the APCP ignition grain. I have found that even the mid power igniters are quite OK to poke into the APCP ignition grain, but you do have to extend the leads because they are far too short. I have actually used e-matches to ignite the AP ignition grain in tests. However, I want to be 100% certain that the hybrid grain starts to vaporize and burn, and the fill tube severs, so using a HP igniter has been very reliable. Having to reload a hybrid motor after an ignition failure is a real PITA!

I will pursue the Nichrome wire option further, because HP igniters are becoming ridiculously expensive. I have a 100m roll of it that cost the same as 4 igniters.
What will probably work is the equivalent I^2*R heating with 12volts as happened with 24. I’ll thoroughly test it with the same Pyrodex grains that Contrail Rocketry calls for. And if there’s any doubt, I can always fall back to 24volts with relays to isolate it from the 12volt club launch system. As an engineer I’ve designed a number of similar systems.
 

Voyager1

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Yep, that should work. It appears we have a similar professional background, as I'm a retired engineer. I, too, designed and built our club's multi-channel launch system.

Have you got your own GSE or does your club support hybrids? We purchased a couple of the Pratt Hobbies valve manifolds and use our own 12V hybrid launch system.
 

DRAGON64

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Ahhh... the good old days when clubs had GSE on hand. In my case I purchased the HyperTEK GSE from our club, but ultimately sold it when I decided not to fly HyperTEK. I have had a number of iterations of GSE, which I have sold off over the years. I am about to take possession of yet another custom system, built for me by a TRF member. Hopefully this system will get used and stick around for a while.
 

Voyager1

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I should add that one of our valve manifolds (amongst other things) was due to the generosity of Tripoli's Prefecture Improvement Plan.

I am gradually converting some of our members over to the 'light side' to embrace hybrids, so we are actively kitting out the club with hybrid GSE.
 

Dan Griffing

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Yep, that should work. It appears we have a similar professional background, as I'm a retired engineer. I, too, designed and built our club's multi-channel launch system.

Have you got your own GSE or does your club support hybrids? We purchased a couple of the Pratt Hobbies valve manifolds and use our own 12V hybrid launch system.
The same Big Sky Rocketry Association club member who loaned me his 38mm and 75mm Contrail hybrid motors (his wife’s brother loaned me his 54mm motor set) for the next few years — also loaned me his GSE, but said I would probably need to rework it. They also said they’d make me a REALLY good deal if I eventually wanted to buy the whole setup.

It also turns out that the other two principles at the Big Sky Rocketry Association — including Steve Shannon— had their hybrid phases. Both Steve Shannon, former Tripoli president, and Dale Emerson, got their L3’s with hybrids.
I’m walking in their footsteps.
 

Voyager1

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If/when I decide to move up to L3, I would love to do it with a hybrid. The thought of lighting up an M Contrail has a certain appeal.
 

Dan Griffing

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I should add that one of our valve manifolds (amongst other things) was due to the generosity of Tripoli's Prefecture Improvement Plan.

I am gradually converting some of our members over to the 'light side' to embrace hybrids, so we are actively kitting out the club with hybrid GSE.
Valve manifolds — One of the appeals of hybrid rockets is that my degree is in chemical engineering, which I’ve mostly never used. So there’s an unscratched itch that I’m hoping hybrids will satisfy. Its totally different from simply popping a solid fuel cartridge in and launching.
 

Dan Griffing

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If/when I decide to move up to L3, I would love to do it with a hybrid. The thought of lighting up an M Contrail has a certain appeal.
The M711 reload I’m fancying for my L3 only costs $95. That’s about 25% as much as equivalent Ammonium Perchlorate motors.

All of this has been made possible by the hybrid motor hardware and GSE that’s been so generously loaned to me. There must be some catch or downside to using hybrids, but before actually using any hybrids, I haven’t discovered it yet.
 

Voyager1

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Yes, I do. It's a basic wired launcher without relays. However, I'm currently building a wireless relay-based controller for the hybrid. It was supposed to be completed for this year's HPR launches, but that got shelved due to COVID.

The ARM/CONT and LAUNCH buttons are illuminated momentary push buttons; the FILL and DUMP are illuminated push-on/push-off.
 

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karlbaum

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I figured this is probably the best thread to ask- what does the Contrail GSE include? I was under the impression that it came with everything needed to fire one of their motors, but is it just the wires and launch controller? It seems to defeat the point of a plug and play commercial system if I had to go source my own plumbing equipment (ie. fill and dump solenoids). Plenty of people fly Contrail though, so I'm curious what the deal is.

Based on additional researching, I'm thinking that's a no, which seems odd to me that Contrail doesn't explicitly say "We recommend these valves, here's where you can buy them" on their website.
The Contrail GSE is a simple relay control system that can control the following: fill solenoid, dump solenoid, and igniter leads. You will need to find another source for your nitrous manifold. It is not difficult to make one yourself. I like these solenoid valves from Wilson manifolds https://www.wilsonmanifolds.com/products/nitrous-solenoids variant=33897420095532 . I use the .180 solenoid to fill and the .073 for a dump solenoid. You can get pipe fittings from McMaster Carr. You will also need a CGA nipple for your fill tank. You can get it from Amazon. There are two types of nitrous tank valves in the US. CGA 326, and CGA 660. One thing I believe that is missing in the Contrail GSE is a solenoid saver circuit. The solenoid saver prevents solenoids from overheating from too much current. I use a pair of 25 watt 30 ohm resistors and a 12V 11000 microfarad capacitor wired parallel. I would be happy to send schematics of my GSE to anyone interested. My email is karlbaum@comcast.net
 
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karlbaum

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Thanks. Given that hybrids used to be way more common and are still decently popular (thanks to Contrail holding out), I'm surprised that there isn't some sort of GSE guide out there. I guess there just aren't that many people building the full setup.
I have made some videos of GSE I made.
,
,
I've added a couple of minor features since making that GSE. Making GSE is somewhat labor intensive so I'm thinking if someone else wants to do it like Tom Sanders I'd be happy to share my plans. I really like this GSE because it incorporates a solenoid saver circuit and it has a vent sensor circuit. These features aren't necessary but I like having them.
 

ContrailRockets

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I have had requests to eliminate the top vent on my 54 mm motor line. Installing a vent through the combustion chamber as in the 75 mm motors and larger. The 20 inch 54 mm is the first to incorporate this concept. As pictured The J-200 BS uses the pleated Black Smoke grain and # 2 CNVA. The internal vent allows this motor to use the vent gas in the combustion process. Venting into a pressurized combustion chamber slows the venting process while adding to the total Newton’s this motor produces. In addition this is the first Contrail Rockets motor to eliminate the need for an external restrictor vent as needed in the 75 mm and above motors.
From memory the resistance is 10 Ohms. However, I stopped using them fairly early in my hybrid launching and use standard high power igniters embedded in a 1cm length of 24 mm or 29 mm APCP grain, depending on the hybrid grain core diameter. The resistors were intended to ignite Pyrodex pellets, but we can’t easily get them over here in Australia. This technique has proven to be very reliable.
The original 24 volt ignition was 10 ohm. The Iron Thermite used in TMT certification required an intense heat source to ignite. Motors were later Re-certified using Pyrodex
42036626-8057-411B-A4FB-5C9738CDCD00.jpeg
58EB5EDB-77A2-4ED5-ABBC-28DE28F7C65D.jpeg
A1B154FF-8ADC-4808-A1EC-F6D863CB0377.jpeg
327A188F-7930-4EE7-BE4D-A4EBACFB60CF.jpeg
73C0DE98-A74E-48E6-AD53-922DCE3568C9.jpeg
 

Dan Griffing

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So is this a new floating bulkhead that Contrail is selling?

I have a set of 54mm Contrail motor hardware (on a longterm loan). What do I need to order to use this?

Are there other 54mm hybrid reloads that work with this?

I have two 54mm rocket’s under construction (three if I swap a 54mm for a 38mm MMT on my carbon fiber laminated Apogee Peregrine) that are configurable for different length hybrid motors and need to know if side venting is a thing of the past.
 

ericm541

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I have had requests to eliminate the top vent on my 54 mm motor line. Installing a vent through the combustion chamber as in the 75 mm motors and larger. The 20 inch 54 mm is the first to incorporate this concept. As pictured The J-200 BS uses the pleated Black Smoke grain and # 2 CNVA. The internal vent allows this motor to use the vent gas in the combustion process. Venting into a pressurized combustion chamber slows the venting process while adding to the total Newton’s this motor produces. In addition this is the first Contrail Rockets motor to eliminate the need for an external restrictor vent as needed in the 75 mm and above motors.

The original 24 volt ignition was 10 ohm. The Iron Thermite used in TMT certification required an intense heat source to ignite. Motors were later Re-certified using Pyrodex

Will this be standard on all hardware orders now? I'm assuming you can see the gas venting when its ready to fire.
 

ContrailRockets

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So is this a new floating bulkhead that Contrail is selling?

I have a set of 54mm Contrail motor hardware (on a longterm loan). What do I need to order to use this?

Are there other 54mm hybrid reloads that work with this?

I have two 54mm rocket’s under construction (three if I swap a 54mm for a 38mm MMT on my carbon fiber laminated Apogee Peregrine) that are configurable for different length hybrid motors and need to know if side venting is a thing of the past.
Newest 54 mm motors eliminate need to drill holes in side of rocket. The ContrailRockets.net site has the new CNVA injector and CNVA I have yet to put reloads on the site.
 

ContrailRockets

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Will this be standard on all hardware orders now? I'm assuming you can see the gas venting when its ready to fire.
Just like the 75 mm and up the vent line attached to the injector baffle then exits the nozzle where it it secured so as venting becomes visible. This is the 3/16 clear line.
 

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This is great, i've been using your 38MM system as a means to learn, I intend to fly M hybrid motors however, seeing this I may invest in the 54MM.
 

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ContrailRockets

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This is great, i've been using your 38MM system as a means to learn, I intend to fly M hybrid motors however, seeing this I may invest in the 54MM.
Can’t fit vent in existing 38 mm configuration. If there is a strong enough demand I can design an internal vent system into the 38 mm motor system.
 

ericm541

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Doesn't matter to me if you do, I wasn't implying you to do so anyway. Just one question though, If I order 54MM system would it come with this new venting?
 

Dan Griffing

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The new 54mm CNVA injector was what caused me to switch out a 38mm MMT on the new carbon fiber laminate — modified Apogee Peregrine that I’m building.

If you had 38mm CNVA injectors with motor loads I wouldn’t have switched. I have a full set of 38mm hybrid motors, and like the price and performance of the 38s.

What do I have to do to express demand?

I’m also waiting to see the Contrail Rockets and Pratt Hobbies websites updated. I also need the RockSim motors database updated at the same time so that I can simulate the new motor loads.
 

ContrailRockets

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I wouldn't mind getting into hybrid rocketry, but I can't even find a single hybrid-ready kit. And I just don't feel like spending endless amounts of time designing and looking for parts and then paying to have stuff delivered from who knows how many different places.
Playing with the 20 inch Full J or 11.25 I motor both will have venting through the combustion chamber.
 
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