THRP-1

[G_T]

Hello everyone,

Somewhere around a decade ago I was thinking about getting L3. I had done L1 and L2 with conventional 3FNC solid rockets. I wanted to do L3 differently, so I designed a 3" minimum diameter hybrid rocket around a Contrail M motor. At that time there were some east sites that had enough waiver that I could push the altitude some. I spent a lot of time on that design.

But in the end, I went a different direction: https://www.rocketryforum.com/threads/sprite-6-and-a-baby-o.37382/

I've always had interest in liquids and hybrids. So I designed and build an EX M hybrid motor. Tiny Hybrid Rocket Project 1. For those of you with access to the Research forum, here's the link: https://www.rocketryforum.com/threads/thrp-1-an-ex-hybrid-project.139372/ You can find out just about anything you'd want to know about the motor in that thread. It uses regulated chilled nitrous, three impinging injectors, and a high turbulence fuel. It's a bit different than conventional hobby hybrids, and burns very smoothly. It is loud, but more like a smooth burning solid. No throaty sounds or resonances from this one.

In this thread I'll show some of the construction of the minimum diameter rocket I'm building to fly that motor at places like Potter (URRF) or MDRA or possibly Battle Park. The rocket is being overbuilt to knock a few thousand feet of potential altitude off the top end, to keep it safely under the various waivers. The rocket has some resemblence of what I designed years ago, just with a lot more pork added! Nonetheless I'm finding it an interesting rocket.

I want actual flight data from the motor. After all, what's the point of developing a motor if not to fly it?

I've attached a picture from a static test, with the motor mounted onto a launch tower. I did tie the tower down with aircraft retainers as the startup thrust is predicted to be in the ballpark of the weight of that tower. Flying the tower was not part of the plan!

I've also attached some old pictures of the motor, from the thread in the Research section.

Lots of the thumbnails are getting clipped, so you might have to click on a picture to see the full image.

Gerald

 

[G_T]

Here's a quick, rather poor sketch, showing the basic layout of the rocket.

At the top of the flight tank, there is a regulator/vent. The little bay for the vent is also used for head end retention of the motor.

Above that is the electronics bay. This will contain an RRC3 and a Raven, and a RunCam for video. At the top of that bay, there is a Peregrine CO2 ejection system, and a TD-2 tether.

Above that is the deployment bag for the main - an old Rocket Rage chute, and above that is the drogue nested into the nosecone coupler. In the nosecone is a tracker.

To speed up making the rocket - since I've little time left - I'm using a Max-Q fincan.

Originally I'd planned on stuffing all the electronics into the nosecone using an extended coupler, but I changed over to this method to add some weight to keep the altitude a little lower.

I'll be posting a lot of pics as the construction goes along. Note that in many of the pictures, the part(s) shown won't be in their final form. Consider the pictures work in progress.

If you have any questions, feel free to ask!

Gerald

 

[G_T]

The regulator vent at the top of the nitrous tank points straight up. That's fine for static tests but not so much so for flying.

I went to a local hardware store, plumbing section, and found this brass elbow that I could remachine into a vent elbow to route the vented gas out the side of the rocket. The little Taig microlathe is quite useful for little odd jobs such as this!

I put the final 3/4-20 thread on holding the large die in large channel lock pliers since I don't have a large enough die stock for it. Then I turned the chuck by hand. I knew I was going to have to do this, so the threads are only about 50%. I'm using plumber's teflon tape on the threads.

I'm showing the partially completed motor retention and vent bay in the other pictures. This shows the placement of the vent out the side of the rocket.

Gerald

PS - I'm using RocketPoxy. Unfortunately it tends to slowly flow over a long period of time. But otherwise it seems to be pretty good.

PPS - For those who have trouble putting nice holes in fiberglass, here are some ideas. Start the hole with a sacrificial #11 exacto blade, spinning the point where you want the hole. Then drill small, and step through until you get large enough to switch over to a grinding point. At low RPM, use the point to essentially sand the hole to size. Beware the dust!

PPPS - The bulk plates were cut on a router with a circle cutting jig, over at Jerry O's place (thanks Jerry!). Any circular depressions you see in bulk plates - there will be a lot - are done at slow speed on a drill press with Forstner and related bits.

 

[G_T]

Here is the work in progress on the upper bulkhead and carrier that goes at the top of the electronics bay.

The CO2 ejection system is a Peregrine, oversized on the CO2 cylinder used. I always oversize with CO2. CO2 does not pressurize as rapidly as black powder, so there isn't an overpressurization risk with going one size up. Is it necessary to upsize? No. But in case ejection gets sticky for some reason, having a longer push time and potentially higher max pressure might just make the difference between successful deployment and a lawn dart. It costs a little more volume and weight, but I consider it cheap insurance.

You can see I trimmed the flange to make the Peregrine fit the 3" rocket better.

The tether is the new TD-2 that was just released. However, I'm not mounting it as intended. Originally it would mount to an eyebolt or U-bolt, and mount completely outside the electronics bay. Since the device has a narrow shoulder where it screws apart, I'm using that to transfer the load to the thick wooden bulkhead. This lets me move half the unit inside the electronics bay.

As a consequence, no wires go outside the bay. That's a feature I like.

I made a brass strip (K&S brass, I had it on hand) to keep the TD-2 from rotating. It is also snugged up with some masking tape. It is quite secure.

Of course it isn't necessary to use a double bulkhead. But this will allow the lower bulkhead to stay on top the electronics bay, while the upper bulkhead can be removed for prep. That will be more obvious later in this thread.

Also when I made those bulkheads, all the electronics were going to go in the nosecone and nosecone shoulder. I changed the design afterwards. Doing it this way - deploying out the rocket body at the top - has lower odds of producing a tangle. I've done it this way for a number of flights on another rocket without any issues. Others I fly with have done it many times as well. It is one of the most reliable methods.

Gerald

 

[Hobie1dog]

WOW I wish I lived next door to you.

 

[G_T]

Thanks Marty!

Here is the cagebay, sort of an open electronics bay. That will make it very convenient to work on the electronics for prep and after-flight operations. There is a lot of flexability for how the volume can be used.

The rods are 6mm stainless: https://www.amazon.com/dp/B07H7NLYVZ?psc=1&ref=ppx_yo2ov_dt_b_product_details This is by far the nicest allthread I've ever seen. The rods are straight, well packaged, and very smooth. The nylon lock nuts and washers are also stainless. I prefer using stainless, just in case the rocket gets left out in the rain hanging on some tree for a few days. I hope that doesn't happen, of course!

The final length of the rods will be determined once I've completed the electronics layout. Since I need weight, I might not actually cut the rods. I have room to telescope a couple inches of excess length down into the retainer ventbay.

It should be getting obvious that the design is essentially a flying motor with everything bolted on top. The rocket body tube is just a tube with holes cut in it, sort of an aero fairing. The recovery loads are transferred from the eyebolts through the allthread rods to the motor retention bulkhead. It is a fairly strong arrangement.

The allthread rods are also capable of transferring the thrust loads since the electronics, forward bulkhead, and chutes with lines are not very heavy.

There is much more to it of course, but that is for later posts This catches the thread up to where I am now, mostly.

Since the body tube is basically just a tube with holes, prep will be very easy. Everything except the drogue and nosecone gets laid out on the table in packing order. Wires get connected to boards and screw switches. Quick links get attached to eyebolts. The drogue line gets dropped through the body tube, and the tube slid down over everything. Then hook up the drogue at the top of the tube and pin the nosecone.

It should be the most convenient prep plan I've tried so far.

Gerald

 

[G_T]

I put a side question on the Research forum looking for a finish or finish combo for the ventbay which is going to get some N2O gas exposure and has some potential for liquid N2O exposure which would be more of an issue. N2O is a strongly polar solvent and is easy to sensitize with organics. So I'm being cautious.

I will be taking pains to minimize the exposure of course. But lots of rocketry is (A) minimizing odds of something bad happening (B) maximizing odds of successful mission even if A does happen.

https://www.rocketryforum.com/threads/n2o-and-suitable-finishes.173016/

 

[G_T]

I've been working a bit on the video camera mount. The mount is quite solid, and it is easy to insert or remove the camera. There's no need to remove the camera to connect a cable.

The camera mounting part is done, but this subassembly will also be holding the batteries for the electronics boards.

I did thin the camera locking tab so the camera goes in and comes out more easily.

To keep the rocketpoxy from running, I added roughly its volume of milled fiberglass as a thickening agent.

I went over the bonding surfaces of the plastic mount with a Shinto saw rasp to give a much better bonding surface. If you haven't used one of those rasps and use wood rasps, get one!

Gerald

 

[rocket_troy]

Nice work Gerald.

TP

 

[G_T]

Thanks Troy!

Here is the first form-fitted battery pocket completed. I have not made the retention yet.

These lithium batteries are slightly larger than the old 9v batteries so either will fit. Some rechargeables should fit as well I would think.

I wrapped a battery in cling wrap, and used mixing stick sections and epoxy to form the pocket. I used some gentle clamping on the sticks to keep the pocket snug.

I may orient this battery connector downwards. With the exception of popping the nosecone, all significant G loading - boost, deployment, grounding - is in the downward direction. Orienting connector down keeps the internals of the cell loaded downwards towards the connector which can be important for some internal configurations of regular 9v batteries.

The battery can be flipped either way. For at least some lithium batteries it is better to have the connector upwards. I'll research the internals of these batteries then decide the orientation.

I did goof a bit. I missed the camera mounting location by about 1/16" from where I intended. Cumulative errors... Now there is perhaps barely room to mount the second battery on the other side of the camera.

Gerald

 

[G_T]

The second battery fits. I'm about halfway through making the pocket for it in these pictures.

The controls for the camera are accessible to the left of the second battery, That volume needed to be left clear.

Gerald

 

[tsmith1315]

Very cool, Gerald!

 

[G_T]

Thanks Tim!

Battery mounts completed, but the hold-downs are not on in this picture. I just have to finish making them.

I finally found someone to supply the nitrous I need for the flight. The source is quite pricy though. It will work for this flight, but I'll be looking for cheaper sources after this burn.

Is the way I'm documenting this build ok? Or are there things you want to see that I'm not showing?

Any questions, ask away!

Gerald

 

[Tractionengines]

I finally found someone to supply the nitrous I need for the flight. The source is quite pricy though. It will work for this flight, but I'll be looking for cheaper sources after this burn.

Ok. Dumb question....I don't know much about hybrid motors...

Is the NOS you need, any different than the NOS used for racing? There are a number of NOS fill stations around here whenever the drag strips are running. (Fewer in mid winter.)

https://www.holley.com/nos_refill_locations/

 

[OzHybrid]

In Aus I get mine from Speed For Sale. Same as the Holley shops. They are better with unusual fill requests and don't throw up their hands in horror. OMG you want nitrous oxide.......

Ok. Dumb question....I don't know much about hybrid motors...

Is the NOS you need, any different than the NOS used for racing? There are a number of NOS fill stations around here whenever the drag strips are running. (Fewer in mid winter.)

https://www.holley.com/nos_refill_locations/

 

[John Kemker]

Ok. Dumb question....I don't know much about hybrid motors...

Is the NOS you need, any different than the NOS used for racing? There are a number of NOS fill stations around here whenever the drag strips are running. (Fewer in mid winter.)

https://www.holley.com/nos_refill_locations/

Nope. Same stuff.

 

[OzHybrid]

Supposedly the performance NOS has sulphur added to stop people inhaling it for recreational purposes. As you can buy an unlimited quantity of whipped cream bulbs ( like the CO2 bulbs but doesn't curdle the cream) it's kind of moot.
I've noticed no trace of sulfur in mine. I don't think they still put use it in Aus. Market is too small.
Good luck with your launch.

 

[G_T]

Thanks; I might need the luck. I haven't tested the GSE or any of the electronics yet!

The shroud is now epoxied to the upper electronics bay bulkhead. The bulkhead above that which hosts the CO2 and tether systems is removable. Just undo the three nuts. Actually the "fixed" shrouded bulkhead can be removed that way as well.

I shortened the electronics bay a little bit by telescoping the allthread into the ventbay. It's now about the length I expect to need for the two altimeter boards.

I aligned everything, and test fit the body tube. It slides on fine, but does take some force. I expect it might be a 2 person job to disassemble, and possibly a 2 person job to assemble. The tube slides over much of the tank portion of the motor. There is a slight taper to the inside of the tube so it get tighter as it is slid in place.

Aligning was adjusting the relative angles of the upper and lower bulkheads to the allthread by adjusting the nylon lock screws. If it is off by more than a tiny bit, the tube won't slide on. It was a bit fiddly. I also took off a little wood here and there from the camera and battery bay bulkheads so they did not interfere with the tube. Touching is fine; pressuring is not. I don't want it binding.

Gerald

 

[OzHybrid]

What are you using for your fuel grain? I remember someone vaguely saying they had a PTFE grain. Was that you.

 

[G_T]

No. I'm not sure how much specifics I can discuss here on that. I do have details under the Research forum. But it is a blend of parafffin and HTPB with metal (not aluminum) and a nitrous decomposition catalyst, designed to enhance high turbulence mixing of fuel and oxidizer during the burn. I've attached a picture of a partial burn, so you can see what I mean by having the grain promote high turbulence mixing. More on that in the next post.

Many things can work ok as hybrid fuel, but I would not expect Teflon to be one of them. There are some specific uses where Teflon makes sense in other types of motors, but as amateurs I strongly recommend avoiding any burning of Teflon. It is better to avoid the fluorine compounds as a class of exhaust products.

Paraffin by itself is fine up to perhaps 6" motors at the largest, if opacified. But it has big issues starting around that size. Slumping leading to CATO being one of them. Blending it with something else can help with those issues. Some choices can enhance the performance in one way or another.

You can check out the various university teams around the world working on (on average) 6" diameter nitrous rockets. You can find some good ideas there, though not every idea you find will be fully thought out! There are some cool projects out there.

Gerald

 

[G_T]

Ok, a bit more about that fuel.

Most every hybrid you encounter has some serious issues.

The combustion products are nearly completely gaseous. Compressed gasses transmit acoustic energy extremely efficiently. A sound wave passing the length of the chamber and reflected back suffers little loss of energy. So there can be a fair bit of acoustic energy in there.

Liquid propulsion systems suffer from this issue. Lots of design work is involved in handling it. The larger the motor, the more of an issue. If it is not handled with a liquid system, combustion is unstable.

Depending on the injectors and the pressure drop through the injectors, a high pressure peak hitting the injectors decreases the nitrous flow into the combustion chamber. Less oxidizer going in, and the combustion pressure drops. Combustion pressure drops, then the pressure drop across the injectors increases, so oxidizer flow increases.

One ends up with rapid oscillations in chamber pressure, and that "classic" hybrid sound. That classic sound is evidence of a poorly operating motor. Combustion instability. It should be cringe-worthy, but is considered a feature by many.

Those pressure oscillations go along with rapid thrust oscillations. An accelerometer needs to have a fair bit higher sample rate for such unstable hybrids or the altitude measured will be off a lot. Barometric apogee deployment is necessary for such motors.

That rough burning surface I posted has higher resistance to flow down the core, like a clogged-up pipe. It generates a lot of turbulence. It scatters sound waves. That improves the situation quite a bit.

Additionally, the grain contains a fair bit of metal. This produces a fog of burning metal droplets and metal oxides. This fog helps absorb acoustic energy, dampening the sound. It does little to improve the ISP; that's not what it is there for.

In a test burn, this hybrid burned super smoothly.

Gerald

 

[G_T]

The vent should jet gaseous and liquid N2O out at pretty good speed, right out the side of the rocket... But in rocketry, if it can go wrong, it probably will...

N2O is a strong polar solvent and gets sensitized by even just traces of organics. Of course it also evaporates very quickly...

I'm being cautious!

I've MGS epoxy coated the plywood and internal surfaces of the ventbay to seal it from liquids. You've probably not used MGS (285, 286, 287), but it is one of the best professional laminating resins out there, particularly for not needing to be post-cured to have pretty good properties. Though, it can be post cured to have even better properties. It is very watery which makes wetout and drydown of fabric easy compared to most other resins. Blend fast and slow hardeners to set the desired working time. Nice stuff, but pricy. Being so thin, it will soak into wood somewhat.

Thankfully MGS lasts a long time. Mine is quite old stock. Heck, even my unopened gallon of resin and quarts of hardener are old stock now.

I expect to be painting on a second coat of something else TBD later, time permitting.

Really the ventbay should not be using plywood. But I didn't have the time to machine aluminum parts.

The rest of the plywood parts might get a seal coating of some sort, if I have the time. That's just to protect against water if the rocket lands in the only ditch in the area (been there) or the only puddle on the whole field (done that) or has to spend some time in the rain up a tree (thankfully, NOT done that!). I'm tempted to just hit them with permalyn sealer since I have an opened container on hand, but I'm not sure it won't dissolve the plastic camera mount!

The ventbay and probably the forward bulkhead shroud will be getting T-nuts to accept button head cap screws for bolting on the airframe tube. I'm not doing that until I have the nosecone done, so I can see how compact I can squish the recovery materials to minimize the length of this long thin rocket. I always like to have the recovery under a little bit of compression. That way stuff cannot shift around under G loads. If it can't shift, it stays just the way you planned. I think that improves repeatability and reliability.

Gerald

 

[G_T]

Epoxy getting a post-cure heat treatment, caveman style. That's a halogen bulb. Temperature control is via distance. If I were more serious about it, I'd do my usual aluminum foil reflector under it and around the sides. That concentrates the heat and makes it more uniform - less turning of parts.

I have an IR thermometer I can use to check and thereby control temperature, but I've done this enough over the years that I don't need to. All I need really is about 120F, to perhaps 140F depending on what I'm using and what I'm trying to achieve. Here I'm using the lower end of the temperature range.

This shouldn't be done with all epoxy of course. West Systems for instance has a low Tg and post-cure heat treating does nothing to improve it. You just soften the epoxy while it is hot. Some epoxy such as the 5min and 15min stuff is probably rendered more brittle by doing this, but I've never tested. It might not post-cure at all. Some professional epoxy requires post-cure. To get the best properties, follow the manufacturer's recommended post-cure schedule.

Note - This is Post Cure. It has already hardened to the touch to the point that it is ok to handle. This is not speeding the initial cure. Generally you DO NOT WANT to speed the initial cure. That's a way to make brittle stressed epoxy. It becomes a failure waiting to happen.

Room temperature epoxy generally takes about a week to reach it's full cure. Most people don't realize that. One thing post-cure does is complete the curing process much faster. It also helps the cure to go to completeness beyond what it would do at room temperature. Lastly if properly done it will de-stress the epoxy.

Ok, enough of that.

How small dare I pack my old 6' Rocket Rage chute? I think it's a Rocket Rage. I bought it 2nd hand about 10 years ago. It is sort of like the Iris chutes, but IMHO not quite as draggy. It packs smaller than the standard Iris but not as small as the lightweight ones.

How tight to pack is of course a tradeoff. That is what is labeled as a 6" deployment bag, but I consider it to be 7". I also have a 9" bag. In the 9" bag it packs more easily of course, and falls out more easily. So deployment is easier. Packing in the smaller bag shown is more of a stuffing operation of course. But it does fit.

I've packed tighter using what I call a tacobag. I may use a tacobag instead of a deployment bag for this rocket. I'll test packing both ways and see. I've put a 54" chute in 5" of a 2" airframe using a tacobag. Length dimension by memory. That was tightly compressed stuffing.

Since there is no pyro exposure in this rocket, I could even make the tacobag out of some tyvek. Hmmm, that's tempting. Low bulk and moderately low friction. I also have some, so that makes it cheap.

Do not pack this tightly with a lightweight rocket or an overly small drogue. You have to make sure there is enough force between the drogue and the rocket body's weight to pull out the main when it is released. If that isn't reliable, it doesn't matter how small you've managed to pack the main.

I'll post packing details sometime later, when I get serious about it rather than just playing with the chute and bags.

Gerald

 

[OzHybrid]

Epoxy getting a post-cure heat treatment, caveman style. That's a halogen bulb. Temperature control is via distance. If I were more serious about it, I'd do my usual aluminum foil reflector under it and around the sides. That concentrates the heat and makes it more uniform - less turning of parts.

I have an IR thermometer I can use to check and thereby control temperature, but I've done this enough over the years that I don't need to. All I need really is about 120F, to perhaps 140F depending on what I'm using and what I'm trying to achieve. Here I'm using the lower end of the temperature range.

This shouldn't be done with all epoxy of course. West Systems for instance has a low Tg and post-cure heat treating does nothing to improve it. You just soften the epoxy while it is hot. Some epoxy such as the 5min and 15min stuff is probably rendered more brittle by doing this, but I've never tested. It might not post-cure at all. Some professional epoxy requires post-cure. To get the best properties, follow the manufacturer's recommended post-cure schedule.

Note - This is Post Cure. It has already hardened to the touch to the point that it is ok to handle. This is not speeding the initial cure. Generally you DO NOT WANT to speed the initial cure. That's a way to make brittle stressed epoxy. It becomes a failure waiting to happen.

Room temperature epoxy generally takes about a week to reach it's full cure. Most people don't realize that. One thing post-cure does is complete the curing process much faster. It also helps the cure to go to completeness beyond what it would do at room temperature. Lastly if properly done it will de-stress the epoxy.

Ok, enough of that.

How small dare I pack my old 6' Rocket Rage chute? I think it's a Rocket Rage. I bought it 2nd hand about 10 years ago. It is sort of like the Iris chutes, but IMHO not quite as draggy. It packs smaller than the standard Iris but not as small as the lightweight ones.

How tight to pack is of course a tradeoff. That is what is labeled as a 6" deployment bag, but I consider it to be 7". I also have a 9" bag. In the 9" bag it packs more easily of course, and falls out more easily. So deployment is easier. Packing in the smaller bag shown is more of a stuffing operation of course. But it does fit.

I've packed tighter using what I call a tacobag. I may use a tacobag instead of a deployment bag for this rocket. I'll test packing both ways and see. I've put a 54" chute in 5" of a 2" airframe using a tacobag. Length dimension by memory. That was tightly compressed stuffing.

Since there is no pyro exposure in this rocket, I could even make the tacobag out of some tyvek. Hmmm, that's tempting. Low bulk and moderately low friction. I also have some, so that makes it cheap.

Do not pack this tightly with a lightweight rocket or an overly small drogue. You have to make sure there is enough force between the drogue and the rocket body's weight to pull out the main when it is released. If that isn't reliable, it doesn't matter how small you've managed to pack the main.

I'll post packing details sometime later, when I get serious about it rather than just playing with the chute and bags.

Gerald

Are the rocks for nose weight?

 

[OzHybrid]

Sent you a PM.

 

[RalfB]

Hello Gerald, I read your post with interest. I'm also experimenting with hybrid grains. I made a grain with a helix out of paraffin and epoxy. Combustion is very even, indicating proper turbulence. I am particularly interested in your metal additions to get the sound problem under control. Can you tell more about that? Unfortunately, I do not have access to the experimental forum and cannot view your post. I've been experimenting with titanium. But that doesn't work because it only burns outside the combustion chamber.
Greetings Ralf

 

[G_T]

Hi Ralf,

I noticed that about Ti. But even so it will help with the acoustic dampening by adding some fog to the combustion chamber. I think the problems with Ti can be summed up:

1) Need rather small particle size. I have that; you might not.
2) Wax in the grain will froth out to burn, but it will also encapsulate the metals until the wax is consumed. Therefore a longer combustion chamber or a post-combustion chamber is needed to give metals a better chance to burn. It needs residence time, even more so than in a solid propellant motor.

The biggest help for combustion stability is the highly irregular burning surface produced by this fuel grain. That resists pressure waves and scatters sound in general. So a sound wave or a pressure wave (point of view) traveling through that core is going to lose a lot more energy through lots of random little reflections than would be the case for a soother core.

That doesn't depend on the metal content. Anyway on careful inspection of a partial test burn, some Ti did burn in the motor. Because of how this grain sort of self-cleans at the end of the burn due to the filming produced by the wax, it is hard to assess how much burned in the motor and how much in the air. But this is a dinky short combustion chamber without a post-combustion chamber. Metalizing the fuel in such a case is always a compromise. I wanted the fog. And in the future I hope to be working with motors large enough to actually use the metal as fuel.

A very crude rule of thumb that I've been working from and has proven out in my testing of various motors, is to have a minimum of 2% fog in the combustion chamber. Hard to achieve with liquids of course! But easy enough with solids and hybrids. It may be unnecessary with the sort of fuel grain I'm using in this experiment.

Gerald

 

[StreuB1]

Try HTPB + 4% -325 or finer AL and 0.5% Manganese Dioxide

Do not forget lamp black, it is critical.

Metals in a nitrous hybrid are completely worthless without a catalyst specifically designed to help them out. MnO does that well and is also a catalyst for N2O decomposition.

;-)

 

[G_T]

Using a different catalyst, and have that stuff already in there. I did a lot of PEP analysis to get to the fuel I'm using for this test. In any event, in this size motor with the wax present, Al won't burn very much inside the combustion chamber.

The motor is not designed to be able to use a grain that does not contain a fair bit of wax. A lower regression rate material would require different dimensions for the combustion chamber. If this motor were designed around a primarily HTPB based fuel, then the Ti I'm using would burn in the motor. Wax changes things a lot.

Very fine MnO and MnO2 have been on my search list for a while now. I've only found relatively coarse material, though I've not looked in a while. I'm using one of the other catalysts that is also a good decomposition catalyst for N2O, and an opacifier. So it serves triple duty.

Thanks,

Gerald

 

[rocket_troy]

Metals in a nitrous hybrid are completely worthless without a catalyst specifically designed to help them out. MnO does that well and is also a catalyst for N2O decomposition.

I would strongly disagree with that.

TP