Hybrids 2023

[G_T]

What prompted the questions was my running into issues getting my fuel cast - not having access to the usual mixers at the moment. Though I could probably just hand mix this one well enough if I get all the chems on hand. Some aren't stored at my place. Plus I don't have a decent mixing location here. I was thinking it would be nice to substitute something else for the R45 as a rubber binder, still include the additives, and avoid the use of any rocketry-specific chemical.

Sorbitol/wax/..., asphault/..., rubber coatings/..., 3D printed ABS (though I don't have a printer yet), Plastisol/..., rolling up rubber saturated nylon fabric, co-melting ABS with additives, and lots of other potential options.

Short-term though, I have less than 2 weeks to the launch.

Next motor design I'd like to ditch reliance on R45 and avoid diisocyanates.

Gerald

 

[rocket_troy]

Next motor design I'd like to ditch reliance on R45 and avoid diisocyanates.

Gerald

Oh, I hear ya on that!

The only time you should be looking at EPDM, however, as an option for hybrid fuels is if you need a *really* low regression rate. There are certain niche applications that might require that eg. Paul Kelly was interested in a 100kft attempt on a long 4" N2O hybrid with a really long burn time, so EPDM was one of the prime candidates as the fuel.
But you're right, there are now sooo many options for N2O hybrid fuels with 3D printing and paraffin casting and whatnot.

TP

 

[G_T]

Getting the GSE together for URRF.

Gerald

 

[Voyager1]

Getting the GSE together for URRF.

Gerald

Nice! Good to see another proud owner of a WFX hybrid setup. Have you considered getting the hybrid monitor module? It would, however, require you to get the pressure sensors for the solenoid manifold.

 

[G_T]

I'm interested in it but don't have anything in the way of details about it.

 

[Voyager1]

I'm interested in it but don't have anything in the way of details about it.

You should contact Wilson F/X for full details about the hybrid monitor. However, briefly the main specifications of the monitor system are:

The Hybrid monitor unit displays the following:

• Fill tank (N2O bottle) (P0) and flight tank (P1) pressures.
• N2O vent temperature (TC)
• Fill tank or rocket mass, depending on where the load cell (LC) is installed. I currently use it for the bottle mass. Installing the load cell to get rocket mass on the rail is a little trickier.
• Pad unit battery voltage

The monitor unit connects to the comms connector of the WFX PBU4W hybrid pad box. This provides 12V and a data connection to the monitor. All information displayed on the monitor is also sent to the launch control unit at the LCO desk via the pad units wireless link.
The monitor has a menu system selected by the 4 toggle switches on the front panel. This menu allows you to calibrate the two pressure sensors and the load cell used to measure the rocket or N2O bottle mass, as well as set the thermocouple type for the vent sensor.
The monitor unit is the orange case on the right, beside the PBU4W-Hybrid unit; the LCU4W-Hybrid is on the left. The load cell is attached to the bench for testing; the N2O bottle with solenoid manifold and pressure sensors in front.

 

[G_T]

Interesting.

 

[Voyager1]

Interesting.

I should add that the monitor unit can be used in a local stand-alone mode, without the need for integrating into the full control system. In that mode you will only get the information at the pad. For full integration into the standard hybrid control system, so that all the information is displayed at the LCU, I believe you will require a firmware upgrade of the PBU, and a firmware and hardware upgrade of the LCU (a switch and a display module). These details should, of course, be confirmed with Wilson F/X.

 

[drewnickel]

For those of you working with hybrids, I've spent the last couple years working on a hybrid motor simulator akin to BurnSim or OpenMotor. It is now available through GitHub. Also attached is a write up on the program.

GitHub - rnickel1/HRAP_Source: Hybrid Rocket Analysis Program

Hybrid Rocket Analysis Program. Contribute to rnickel1/HRAP_Source development by creating an account on GitHub.

github.com

 

[cfb_rolley]

For those of you working with hybrids, I've spent the last couple years working on a hybrid motor simulator akin to BurnSim or OpenMotor. It is now available through GitHub. Also attached is a write up on the program.

I had a play around with this the other night, it's pretty good and fairly easy to use! Thank you for this little gem!

 

[cfb_rolley]

Totally forgot to post about this a couple weeks ago…

I received my new 7” micro-hybrid case and naturally, immediately wanted to fly it ASAP. I used an 82mm 3d printed ABS fuel grain and got some pretty good results.

Apogee was only 20m lower than an aerotech D15 reload in the same rocket despite the micro-hybrid being a much heavier motor. It’s also louder and has a pretty awesome exhaust flame haha.

The big advantage though is the cost imo. This flight cost me less that $2 AUD in consumables. That is *crazy* cheap compared to solid motors here, where even a pair of Estes D12s will set you back close to $60.

 

[Jeremy Sim]

Totally forgot to post about this a couple weeks ago…

I received my new 7” micro-hybrid case and naturally, immediately wanted to fly it ASAP. I used an 82mm 3d printed ABS fuel grain and got some pretty good results.

Apogee was only 20m lower than an aerotech D15 reload in the same rocket despite the micro-hybrid being a much heavier motor. It’s also louder and has a pretty awesome exhaust flame haha.

The big advantage though is the cost imo. This flight cost me less that $2 AUD in consumables. That is *crazy* cheap compared to solid motors here, where even a pair of Estes D12s will set you back close to $60.

View attachment 599709

Can you please give me some more details about the printed fuel grain?
I'm about to start playing with my micro hybrids

 

[cfb_rolley]

Can you please give me some more details about the printed fuel grain?
I'm about to start playing with my micro hybrids

Can do! I’m pretty sure I can PM you the cad and stl files when I get home, but they’re a bit like a rifled grain - a 12 point star port with a 180 degree twist over the length of the grain.

 

[Jeremy Sim]

Totally forgot to post about this a couple weeks ago…

I received my new 7” micro-hybrid case and naturally, immediately wanted to fly it ASAP. I used an 82mm 3d printed ABS fuel grain and got some pretty good results.

Apogee was only 20m lower than an aerotech D15 reload in the same rocket despite the micro-hybrid being a much heavier motor. It’s also louder and has a pretty awesome exhaust flame haha.

The big advantage though is the cost imo. This flight cost me less that $2 AUD in consumables. That is *crazy* cheap compared to solid motors here, where even a pair of Estes D12s will set you back close to $60.

View attachment 599709

Can you please give me some more details about the printed fuel grain?
I'm about to start playing with my micro hybrids

Can do! I’m pretty sure I can PM you the cad and stl files when I get home, but they’re a bit like a rifled grain - a 12 point star port with a 180 degree twist over the length of the grain.

yes please

 

[Jeremy Sim]

Totally forgot to post about this a couple weeks ago…

I received my new 7” micro-hybrid case and naturally, immediately wanted to fly it ASAP. I used an 82mm 3d printed ABS fuel grain and got some pretty good results.

Apogee was only 20m lower than an aerotech D15 reload in the same rocket despite the micro-hybrid being a much heavier motor. It’s also louder and has a pretty awesome exhaust flame haha.

The big advantage though is the cost imo. This flight cost me less that $2 AUD in consumables. That is *crazy* cheap compared to solid motors here, where even a pair of Estes D12s will set you back close to $60.

View attachment 599709

What sort of heights are you getting out of the Micro-Hybrid?

 

[cfb_rolley]

What sort of heights are you getting out of the Micro-Hybrid?

Last flight with the extended case was just over 120m with 312g GLOW, D15 reload in the same rocket ends up being about 40 grams lighter or so and hits just over 140m.

I haven’t had a chance to test the regular length one with an ABS grain yet, it’s been way too windy here haha.

 

[cfb_rolley]

A few questions for the people more knowledgeable on hybrids than I am.
First, what's the reason behind needing to vent the motor before approaching for hybrids? is this specific to Contrail motors or is this for everything? because from my understanding, the old Aerotech motors couldn't be vented remotely, so is this related to not being able to remove the igniter in Contrail motors without disassembly or is it just due to the fact that it's a loaded pressure vessel?

On Contrail motors specifically, the vent at the top of the motor is always open, so obviously in the event of a ground support failure of some kind, this would still mean that the motor will eventually drain, right? I imagine on large motors this would take an excruciatingly long time but for smaller motors like a 16 inch x 38mm, how long does this take?

Finally - more broadly - fuel grain geometry. I've been playing around with pleated grains in my micro hybrid and noticed different behaviour towards the beginning and end of burn compared to just straight port grains. this got me thinking - since the surface area of the port changes through the burn, this should mean the O/F ratio will change. Now, I imagine this would be near impossible to get right, but has there been much research in to matching up the surface area to the oxidiser flow as the pressure in the tank drops in order to optimise O/F ratio for every part of the burn?

 

[Jeremy Sim]

Last flight with the extended case was just over 120m with 312g GLOW, D15 reload in the same rocket ends up being about 40 grams lighter or so and hits just over 140m.

I haven’t had a chance to test the regular length one with an ABS grain yet, it’s been way too windy here haha.

Looks like I have managed to locate some Aluminum N20 Cartridges so should be able to fly them at Tripoli events!! Just waiting for them to arrive from the USA

 

[maddmaxx11]

Where did you find the aluminum N20 cartridges In the USA?
I had thought about trying one of these micro hybrids but can fly because of the steel.

 

[cfb_rolley]

Where did you find the aluminum N20 cartridges In the USA?
I had thought about trying one of these micro hybrids but can fly because of the steel.

Definitely want to know as well, QRS will likely let me launch on their back rails if it's an aluminium cartridge. I'm trying to get a source of 16g cartridges as well so I can order a mini but the only ones I can find in Australia are the growlerwerks ones that are like $35au for a pack of 5... that's still cheaper than APCP motors here though haha.

 

[ContrailRockets]

Contrail Rockets 38 and 54 mm motors vent out the top of motor. These are pad filled using a supply cylinder and solenoid valve. In the manifold is also a tee and a purge valve. This allows the motor to be remotely emptied without approaching a pressurized motor. The 75, 98 and 152 mm motors vent back down through the combustion chamber and then to an external vent fitting. This allow the motor to use the vent gas in the combustion chamber. In addition venting at combustion chamber pressure slows the venting compared to venting to atmosphere pressure.

You can go to our YouTube channel and see a 54mm internal vented motor assembly using a 13 star grain.

Since the Nitrous Oxide motor tank is empty having the igniter installed during assembly is safe. We supply redundant igniters to reduce the need to purge a motor once filled on the pad.

AeroTech Hybrids used a prefilled DOT cylinder.

Our aluminum motors are designed to 3000 psi and tested to 2000 psi. They are not DOT cylinders and should not be approached when pressurized.

 

[cfb_rolley]

AeroTech Hybrids used a prefilled DOT cylinder.

Ahh I see, that makes sense now. I always wondered what the reasoning what happened in the case of an AT hybrid not firing.

Contrail Rockets 38 and 54 mm motors vent out the top of motor.

I'm looking at 16" and 20" 38mm motors, as that'll be the biggest I can fly for now. How quickly do these lose pressure through the vent? For example if you're using this setup where you heat the vent line to failure and the e-match didn't burn through the line, would you just wait it out until the motor has vented through the top?

and when firing these smaller motors, do you just leave the fill solenoid open when firing so that it's full when launched or do you close the fill valve and then just launch straight away?

 

[Voyager1]

I'm looking at 16" and 20" 38mm motors, as that'll be the biggest I can fly for now. How quickly do these lose pressure through the vent? For example if you're using this setup where you heat the vent line to failure and the e-match didn't burn through the line, would you just wait it out until the motor has vented through the top?

I use the 16” and 36” 38mm Contrail motors, but I haven’t waited for them to empty through the vent - I use a dump/purge solenoid as well as fill solenoid to do it quickly when necessary.

and when firing these smaller motors, do you just leave the fill solenoid open when firing so that it's full when launched or do you close the fill valve and then just launch straight away?

I typically leave the fill solenoid on until ignition occurs.

 

[ContrailRockets]

The vent is a .028 inch hole and is venting gas not liquid. If you think of a can dust off when inverted it disperses liquid right side up it I’d gas. As you use it the can cools lowering pressure slowing the flow. As Contrail 38 mm motors are venting from a 100 % full tank and certified by TMT so that fill to a visible vent stream. Stop filling and begin a count down from five.
Wanting to maximize your Nitrous Oxide density or loading by keeping the fill on till ignition is initiated is an option especially if you have a delay from filled ready to launch and a launch hold, an aircraft wondering where all the fuss is about.

I have never timed how long it takes to vent a 140 cc from a 16 inch 38 mm motor. This is not an approved procedure. A purge that dumps liquid from the bottom is required it is visible and positive way of dumping Nitrous Oxide and the pad is not tied up. As you are top venting gas not liquid you could assume the motor is depressurized when in fact pressure remains. Approaching a pressurized hybrid motor is a violation of the safety code.

 

[cfb_rolley]

Approaching a pressurized hybrid motor is a violation of the safety code.

I know, that’s why I was asking what happens if you were using the manifold setup that you have where dumping is done by heating the line to failure and the line didn’t burn through.

On your website it mentions that if it doesn’t burn through, you can attach another e-match. If you can’t approach the motor, I’d imagine that you can’t approach the fill system to attach another e-match to the dump line because it will be next to the pad?

 

[rocket_troy]

Approaching a pressurized hybrid motor is a violation of the safety code.

It's a violation of safe practices *if* the tank's failure point is probably below x3 margin, although there could be an argument for below x2. I don't think it's a violation of the safety code because I don't think it's mentioned in the safety code for that reason.

TP

 

[cfb_rolley]

I don't think it's mentioned in the safety code for that reason.

I actually can’t find anything about hybrid launch procedures in the Tripoli safety code, NAR safety code or NFPA 1122 or 1127 codes. Am I looking in the wrong places or just blind? Regardless, I wouldn’t really want to approach a filled hybrid anyway haha. I’m extremely confident in Contrail casings, but the other world I’m very deeply involved with is dealing with nitromethane and drag racing - If you’re familiar with that, you’ll know that I’ve seen *a lot* of things turn to disaster unexpectedly haha.

That said, I’m sorry for all the questions but I’m literally the only member of my club that has any experience with hybrids, so I’d be the one teaching everyone else about them when I eventually pull the trigger on a full size hybrid. That’s quite a responsibility and I want to make sure I understand every aspect of bigger hybrids before I go launching with the club and teaching others about it.

 

[rocket_troy]

I actually can’t find anything about hybrid launch procedures in the Tripoli safety code, NAR safety code or NFPA 1122 or 1127 codes. Am I looking in the wrong places or just blind? Regardless, I wouldn’t really want to approach a filled hybrid anyway haha.

Well, if you have an Aerotech hybrid of the 90s era, you wouldn't be just approaching a filled hybrid, but also handling one - which is perfectly safe BTW. Point is, if you were to include this stuff into the safety code, the safety code would need to be twice the size it currently is due to the various ifs and buts associated with how much structural margin is within specific flight tanks.
As a general rule, only approach a filled flight tank if you really know what you're dealing with and have intimate knowledge of the tank structure to be confident there's margin in hand OR it's a DOT rated flight tank suitable to store the N2O and that in both cases - the tank is not overfilled. If there's any guessing and/or assuming involved, then stay a safe distance.

TP

 

[ContrailRockets]

I know, that’s why I was asking what happens if you were using the manifold setup that you have where dumping is done by heating the line to failure and the line didn’t burn through.

On your website it mentions that if it doesn’t burn through, you can attach another e-match. If you can’t approach the motor, I’d imagine that you can’t approach the fill system to attach another e-match to the dump line because it will be next to the pad?

That system has zero inventory as we work to improve the valveless purge. Understand that this is a process and we are working to perfect this cost effective solution to purging.
We use resistors not ematches and are working on other heat producing alternatives.
Keep watching.

 

[cfb_rolley]

That system has zero inventory as we work to improve the valveless purge. Understand that this is a process and we are working to perfect this cost effective solution to purging.
We use resistors not ematches and are working on other heat producing alternatives.
Keep watching.

Ahh cool, thanks for that info. Have you considered or tried some kind of non-pyro hose cutter? Don't know know how reliable something like that would be though or if it'd even be cost effective anyway. I do really enjoy seeing what you're working on, and that you're keeping the hybrid option very much alive.