Micro Hybrid

[Silverfish]

Hi again :D,

I have recently purchased a Micro Hybrid rocket motor (24mm) from Eclipse Rocketry, and am very excited at the thought of launching it, however I have some points that I need to clarify.

Firstly, having read the instructions, it tells me that I need to use some form of pre-heater to initiate the motor. It is recommended that I use the grain from a RMS reload, but I would like to avoid having to buy these if possible, and waste everything but the grain itself, and to improvise. One possible thought that I had was to use a coil of plastic igniter cord, but I cant find anywhere in the UK where I can get some.

Another thought is to use the gunpowder from a shot gun cartridge, which I have readily available (I will post pictures of a test I did using an empty BP motor case, an extended igniter and some of the gunpowder). My problem with this idea is how to restrain the powder inside the hybrid, and stop it falling everywhere. It is in a rather inconvenient place, as you can see from the attached photos.

My second query is what rocket to fly it in. I wanted to scratch build a V-2, with an added payload section for the deployment circuitry and charge, any suggestions or ideas are welcome.

Finally, as the motor does not contain an ejection charge, I was wondering if anyone knew of a good (and cheap) altimeter that deploys a parachute, and also what to use as the charge itself?

Thank you in advance for all your help.

Silverfish.

[Gillard]

Over on EMRR there is review on a micro hybrid, with a link to a discussion group, that might help.

http://www.rocketreviews.com/reviews/all/cm_microhybrid.shtml.

please post any success, as i've had a passing interest in micro hybrids but never got round to it. good to see a UKer trying something a bit new

[r1dermon]

i'd try a resistor wire like nichrome. coil it up and see how it works...

i'd definitely shy away from using something like black powder in a confined space like that.

[rocket999]

Hi again :D,

I have recently purchased a Micro Hybrid rocket motor (24mm) from Eclipse Rocketry, and am very excited at the thought of launching it, however I have some points that I need to clarify.

Firstly, having read the instructions, it tells me that I need to use some form of preheater to initiate the motor. It is recommended that I use the grain from a RMS reload, but I would like to avoid having to buy these if possible, and waste everything but the grain itself, and to improvise. One possible thought that I had was to use a coil of plastic igniter cord, but I cant find anywhere in the UK where I can get some.

Another thought is to use the gunpowder from a shot gun cartridge, which I have readily available (I will post pictures of a test I did using an empty BP motor case, an extended igniter and some of the gunpowder). My problem with this idea is how to restrain the powder inside the hybrid, and stop it falling everywhere. It is in a rather inconvenient place, as you can see from the attached photos.

My second query is what rocket to fly it in. I wanted to scratch build a V-2, with an added payload section for the deployment circuitry and charge, any suggestions or ideas are welcome.

Finally, as the motor does not contain an ejection charge, I was wondering if anyone knew of a good (and cheap) altimeter that deploys a parachute, and also what to use as the charge itself?

Thank you in advance for all your help.

Silverfish.

Alright. For a preheater you simply need something that will burn through the fill tube (or in the burst disk in this case), start the fuel burning, and essentially start the motor.

To make some, you could use the APCP grain as stated in the instructions. It is a little bit of a waist, but you only need about 1/2in of propellant. This means you would be able to get 12 pre-heaters our of one reload kit. This is about $1 per.

If you have some EX skills, you can make your own preheaters. This might be the best option. It doesn't even need be APCP. You could make some sugar propellant preheaters for very little $.

I would be a little afraid of using loose shotgun powder in the motor. It isn't black powder, it is nitrocellulose. I know it burns pretty slowly in open air, but if it is contained it can explode violently (like if the nozzle gets clogged). Now I don't want to go into too much detail here so this post doesn't get removed, but you could make a solid preheater from smokeless powder. Now I have never done this, but think of it this way. Nitrocellulose is used in igniters for a binder. It is dissolved in acetone. You could mix a little acetone with your nitrocellulose and form your preheater grain. Once it is dry you would get a solid nitrocellulose preheater. This would bind together your loose powder and solve your problem.

If you do this you should be careful. The grains will vary in burn rate. Maybe you could use pyrodex pellets cut to the correct size.

Is this post within the rules of this forum? I don't mean to cause any trouble and if it isn't ok then I will edit it to be within the rules.

How do you like the micro hybrid? I am thinking of getting one to experiment with different fuels on a small scale.

Sam

[dixontj93060]

Yes, use Triple Seven Pellets (http://www.hodgdon.com/tripleseven-pellets.html) and cut them to size.


Maybe you could use pyrodex pellets cut to the correct size.

[WiK]

Cool, good to see some more people in the UK interested in microhybrids. I've been playing with mine for a year or two now, they're fun little motors.

For ignition, PIC is definitely the best way. Much cheaper than using bits of aerotech reload, and you can use (relatively) cheap Estes igniters to ignite it. What I do is coil it up in the preheater well, then run it down the fuel grain and out of the nozzle, then just tape on an igniter. Takes a couple of seconds to ignite, but as long as you coil it the right way (going from the centre outwards), you're almost guaranteed ignition. You can find it in the UK, but I don't think it can be shipped easily (or at all). Malcolm at Rockets And Things (http://www.rocketsandthings.com) had a couple of reels at IRW in August, drop him an email and see if he's going to any launches near you.
Making any sort of preheater yourself is a bit dodgy under UK explosives law, though I'm not sure what cutting up pyrodex pellets count as. Though if you ask me, getting ahold of PIC is probably going to be easier than pyrodex.

As for flying them, I've only flown mine in an Art Applewhite 24mm saucer. IMO once you add the weight of an altimeter and battery to an already heavy microhybrid motor, things are getting a bit too heavy. The saucer is perfect as it stays low enough for you to see the whole flight and you don't have to worry about recovery at all. You can also tighten down the initiating bolt while the motor is already taped into place.

A couple of videos (more on my youtube account (http://www.youtube.com/user/wikrok))...

Saucer flight at IRW:
t91UdJSe3cs


And a static burn in the back garden:
fKi3jU3Stqc

Cheers,
Phil

[bobkrech]

Folks.

The microhybrid is not a certified motor in the US, and we do not get into the details of ex or research motors here, but I'll keep this open if folks keep the discussion focused on hybrid operation and not ex.

Gillard posted an excellent link to Art Upton's article on EMRR that contains a link to the Yahoo microhybrid group where you will find a small but enthusiastic group of users.

Just as a general warning, do not use BP to ignite a microhybrid, or any other hybrid as you will simply blow it up. BP is used to activate a pyrovalve in larger hybrids, but the actual ignition is always done with a sliver of APCP, or Pyrodex(R) pellets (or similar pellets) that burns for 10's of milliseconds. (Re: Alpha Hybrids)

A simple hot wire will also not ignite a hybrid. You may melt the plastic fill tube with a hot wire, but the nitrous will not decompose due to heat capacity issues. You need the heat of a burning pyrogen to overcome the vaporization induced cooling of the nitrous to get prompt ignition.

Bob Krech. Propulsion Moderator

[rstaff3]

If you have a local research group you can almost always liberate some APCP that's destined for a fire pit. I found a metal tube to ream out a disc of propellant from a discarded 38mm mm grain. The disc is just a tad big so when it's pushed into place it stays on it's own.

[billspad]

A Quickburst twiggy will work.

[Peartree]

I don't know how common this is, but at NARAM I saw a friend's rocket CATO with a single use APCP motor. The nozzle blew off but nothing lit and we found the fuel grains unburnt on the ground. I can't think of what else they would be useful for so if this were to happen at a launch near you perhaps the poor soul would donate the remains to you.

[als57]

Buy some 18mm Blue Thunder reloads from Aerotech (Valuerockets.com) and use slices of that. One grain should yield 3 or 4 slices.

Al

[billspad]

I don't know how common this is, but at NARAM I saw a friend's rocket CATO with a single use APCP motor. The nozzle blew off but nothing lit and we found the fuel grains unburnt on the ground. I can't think of what else they would be useful for so if this were to happen at a launch near you perhaps the poor soul would donate the remains to you.

Way too common. At our launch on Saturday I think we had 4 APCP motor cato's and 2 or 3 black powder. A couple of the APCP motors had leftover propellant.


Rather then do a separate post and since I know Bob is watching us I'm going to ask this first here. Can I tell him about the combination, nozzle, fuel grain and preheater that you saw me use in a microhybrid?

[bobkrech]

Way too common. At our launch on Saturday I think we had 4 APCP motor cato's and 2 or 3 black powder. A couple of the APCP motors had leftover propellant.

Rather then do a separate post and since I know Bob is watching us I'm going to ask this first here. Can I tell him about the combination, nozzle, fuel grain and preheater that you saw me use in a microhybrid?
Bill

Yes. Since we were conducting S&T safety tests of the concept I believe that it is a reasonable subject.

Bob

[billspad]

The i.d. of the microhybrid is slightly bigger than the o.d. of a 18mm motor. If you leave out the nozzle and put in a C6-0 as the fuel grain (you may have to shorten the casing) you've got a combination nozzle, fuel grain and preheater. I thought I had a curve from when we fired it but I can't find it.

[rocket999]

Cool, good to see some more people in the UK interested in microhybrids. I've been playing with mine for a year or two now, they're fun little motors.

For ignition, PIC is definitely the best way. Much cheaper than using bits of aerotech reload, and you can use (relatively) cheap Estes igniters to ignite it. What I do is coil it up in the preheater well, then run it down the fuel grain and out of the nozzle, then just tape on an igniter. Takes a couple of seconds to ignite, but as long as you coil it the right way (going from the centre outwards), you're almost guaranteed ignition. You can find it in the UK, but I don't think it can be shipped easily (or at all). Malcolm at Rockets And Things (http://www.rocketsandthings.com) had a couple of reels at IRW in August, drop him an email and see if he's going to any launches near you.
Making any sort of preheater yourself is
a bit dodgy under UK explosives law, though I'm not sure what cutting up pyrodex pellets count as. Though if you ask me, getting ahold of PIC is probably going to be easier than pyrodex.

As for flying them, I've only flown mine in an Art Applewhite 24mm saucer. IMO once you add the weight of an altimeter and battery to an already heavy microhybrid motor, things are getting a bit too heavy. The saucer is perfect as it stays low enough for you to see the whole flight and you don't have to worry about recovery at all. You can also tighten down the initiating bolt while the motor is already taped into place.

A couple of videos (more on my youtube account (http://www.youtube.com/user/wikrok))...

Saucer flight at IRW:
t91UdJSe3cs


And a static burn in the back garden:
fKi3jU3Stqc

Cheers,
Phil

Don't you need an explosives permit to buy PIC in the U.S.? Do you need a permit for mantitor cord? If not, is there somewhere I could get some?

Sam

[WiK]

I don't know about the US, but here in the UK PIC is licence free. Here the mantitor stuff does require an explosives certificate, as it's in a different class to the old PIC.

Couldn't find the UN number/class for PIC, but for Mantitor it's UN0103 - Fuse, igniter tubular metal clad, Class 1.4G. I'm sure someone more familliar with US law could tell you if that requires any permits or whathaveyou.

Cheers,
Phil

[r1dermon]

1.4g does not require a license in the USA. it's the same DOT classification as consumer fireworks. regular visco fuse is classified as 1.4s, which requires no hazmat and can be shipped via air freight.

for a full break down of all the class 1 explosives, this link has proven invaluable in the past for me.

http://environmentalchemistry.com/yogi/hazmat/placards/class1.html#1.4

[bobkrech]

1.4g does not require a license in the USA. it's the same DOT classification as consumer fireworks. regular visco fuse is classified as 1.4s, which requires no hazmat and can be shipped via air freight.

for a full break down of all the class 1 explosives, this link has proven invaluable in the past for me.

http://environmentalchemistry.com/yogi/hazmat/placards/class1.html#1.4
Misinterpreting certain federal regulation can get you in a heap of trouble. The link you reference is excellent for DOT regulated hazmat shipping, but has little relevance to BATFE or the USPS rules and regulations.

DOT and BATFE are two distinctly separate US government agencies. DOT Division/Class assignments have little to do with BAFTE licensing requirements. The Congress and the courts decide what licenses and permits you need to have for explosive items. If your are a shooter of antique firearms, or hunt with a muzzle loader, Congress says you do not have to have a BATFE explosives permit to purchase and store up to 50 pounds of black powder, however if you fly rockets and want to purchase BP for ejection charges, Congress says you have to have a BATFE permit to do so. Irrespective of BATFE permits, DOT treats BP as a 1.1D high explosive for transportation, however certain limited quantities of BP may be shipped as a class 4.1 flammable solid when labeled as NA0027 BLACK POWDER FOR SMALL ARMS because Congress mandated the exemption. There are 60,000,000 voting gun owners in the US and maybe 6,000 voting high power rocket folks so now you know why the Congressional exemption exists.

We all know US District Court decreed that APCP and APCP rocket motors motors may not be regulated by BATFE because they didn't meet the technical BATFE definition of an explosive. The means you don't need a BATFE permit to possess or use any size APCP rocket motor. This does not effect the shipping of rocket motors because DOT follows DoD and UN testing procedures and classifies APCP rocket motors as 1.4, 1.3, or 1.2 explosive articles for transportation.

These two examples show you can not use DOT classifications as an indicator of whether or not you need a BATFE explosives permit for materials.

Confusing USPS mail and DOT shipping regulations is also problematic. The USPS and DOT are two distinct government agencies and have different rules, based on different Congressional mandates.

The USPS delivers "mail" and by law is excluded from delivering hazmat, and can not charge a hazmat fee. Under USPS regulations, commercial certified model rocket motors or kits containing not more than 30 grams of propellant are not (considered) hazardous and therefore can be mailed by parcel post by A USPS authorized individual if they are packaged and labeled in a prescribed manner. (Written authorization is require before posting.)

DOT shipping regulations control common carriers: commercial delivery services, trucking companies, and rail, air and sea shipments. DOT allows common carriers to carry certain hazardous materials and to charge the shipper a hazmat fee to cover the additional expenses they incur to maintain compliance with DOT hazmat regulations. By DOT definition, materials classified as 1.4S materials are hazmat and will incur a hazmat fee when shipped by a common carrier.

The bottom line is that if you do not properly package, label, mark and document a shipment of rocket motors by common carrier, or mail them via the USPS, you are breaking Federal law and the penalties are severe. If your illegal shipment is discovered by a DOT or USPS inspector, at minimum you will be receive a multi-thousand fine, and in the worst case, prosecuted for a felony, and we don't what this to happen to TRF readers.

Bob

[r1dermon]

i think you're misinterpreting what i said.

i never implied that 1.4s was not a hazmat material, like you said, a 30g slug of APCP can be shipped USPS as it's not considered hazardous material. (most) 1.4s is not considered hazardous material by USPS and therefore can be shipped by them. 1.4s WILL incur a hazmat charge for a private carrier like UPS. as will 1.4g, although, 1.4g is normally carried via. a trucking company because i dont think UPS deals with those materials. (RLcarriers jumps to the front of my mind).

i also never said anything about black powder, which it should be noted, that the main types of black powder produced today fall into two categories. Fg and Fa. so, your primer powder for your firearms would be FFFFg, and your blasting powders, those normally packaged in 50lb polyethylene bags, would be FFFFa. the G denotes a sporting powder. so chances are, if you're buying Fg powder, it's being packaged in 1lb seperate containers intended for sporting use.

no assumptions should be made about DOT regulations in regards to the requirements of BATFE licensing requirements. however, i only said that 1.4g articles in the USA are not subject (unless im missing something) to BATFE licensing at this time. there are certain 1.4s articles which may or may not be subject to licensing for posession or use by the BATFE, the easiest way to check is to call your AHJ or fire marshal. either way, no implication was intended that the DOT regulations were to be a guideline for BATFE requirements.

[rocket999]

So, if I don't need a permit, where is someplace I can get some? It seems like shipping would be very hard (expensive) to do. I have never seen anyone who sells it in the US. Does anyone know of anyone?

Sam

[bobkrech]

You can get them at Aerocon Systems. http://aeroconsystems.com/motors/Screamer_folder/screamer.htm

Just remember that they are not certified motors, and as such may not be launched at NAR or Tripoli sanctioned launches. They may be flown at Tripoli Research launches or on your own.

Bob

[Silverfish]

Thanks to you all for your replies. It sounds like it's time to experiment :D .... I'm going to try to get hold of some PIC, and have already contacted a local specialist in muskets and such-like, who may be able to get hold of some Pyrodex pellets (he normally sells powder/grain, but not the pellets - and as a propellant rather than an ex., is not restricted here), as well as trying some of my own ideas. It's intriguing that there is so much difference between the States and the UK in these matters - and just want to add that the last thing I want to do is create any problems for the moderators..

I've also decided to run some test-bed trials before putting the motor in anything, although I'm still hopeful of eventually launching a rocket with parachute recovery etc. using it. In the interim, I might try a simple tumble/glide design just to get the thing off the ground.

Can't wait to get started, and I'll update with my experiments.

Silverfish

[rocket999]

Does anyone know were PIC or mantitor cord is available in the U.S.? I live in MI and I think it would be a pain to ship it, and it seems like it would be good at igniting solid motors as well as micro hybrids.

Sam

[bobkrech]

Does anyone know were PIC or mantitor cord is available in the U.S.? I live in MI and I think it would be a pain to ship it, and it seems like it would be good at igniting solid motors as well as micro hybrids.

Sam
Unless you have a BATFE permit, no manitor cord.

Read Billspad's post on doing it the easy way with a Estes C6-0 booster motor. In the method, you light the C6-0 conventionally, and the burn through starts the hybrid using the cardboard casing as the fuel. Can't get any simplier.

Bob

[WiK]

Does the C6-0 have enough thrust to lift the microhybrid, recovery electronics and rocket safely, or are things getting a bit heavy then?

[billspad]

Does the C6-0 have enough thrust to lift the microhybrid, recovery electronics and rocket safely, or are things getting a bit heavy then?

It was a static test too see if it would work. I agree it's on the edge but I think it can be done.

[rocket999]

Just a quick question. What is the nozzle throat diameter on the micro hybrid?

[RocketMonkey]

This is available here in the US and looks to be based on the same design. But as Bob said, not certified and should be treated as such.
http://www.aeroconsystems.com/motors/Screamer_folder/screamer.htm

[Bender222]

an alluminum or charcoal based fuel would burn too fast to be an effective grain wouldnt it? I read somewhere that the optimal oxidizer/fuel ratio is 7/1 for hybrids. considering that the n02 is only 8grams dont we have a bit too much fuel? anyone thought of trying a larger tank such as the 16g bulbs? maybe even fabricated a cheap tank to hold even larger quantities of n02.

[bobkrech]

A B6-0 would be a better choice than the C6-0 for a heavy rocket as the low thrust tail is rather long with the C.

The micro hybrid is what it is: a hybrid using an off-the-shelf Nitrous whipette. It's not optimized for being a hybrid. The fuel can be anything that burns, even a paper motor casing.

Bob

[Bender222]

would there be any specific materials which would create a large thrust advantage over just kraft paper or nylon. Are there certain properties that you would look for? The SpaceShipOne used a hybrid engine for its top stage utilizing No2 and HTPB rubber. What would be there reason for selecting HTPB as the fuel?
Once the bulb is pierced the pressure release is random. Would there be a cheap way to regulate it so that you could have more preditable burn sequence?

[rocket999]

would there be any specific materials which would create a large thrust advantage over just kraft paper or nylon. Are there certain properties that you would look for? The SpaceShipOne used a hybrid engine for its top stage utilizing No2 and HTPB rubber. What would be there reason for selecting HTPB as the fuel?
Once the bulb is pierced the pressure release is random. Would there be a cheap way to regulate it so that you could have more preditable burn sequence?

I am not sure about why SpaceShipOne chose HTPB, but I do know that aluminum powder will increase isp. Add some of this to your fuel before you cast it. Also Wax is a good fuel. I have read it has about 10 isp more then HTPB (I can't remember where I read it though.). So if you were to cast some fuel grains from wax and AL (or just wax) you would get a good advantage over the paper fuel grains.

Epoxy also works as a fuel. Someone posted in this thread a video of a micro hybrid fueled by epoxy and aluminum.

What do you mean exactly about regulating the flow? I just grabbed my skyripper 29mm motor and it's injector is just a hole, nothing fancy.

Sam

[Bender222]

the speed and amount of gas escaping from the bulb will change as the bulb is emptied. I don't think there is a cheap way to control the flow so that it is constant until depleted.
I have ordered one to experiment with. I live in the US so i do not iknow when to expect it. Anyway my intention is to set up a static test stand and determine the best fuel aswell as what I can do to tweak the Isp. I have 16g capacity No2 bulbs once I scale and fabricate another set of parts to use with them.

[WiK]

Presumably if you found a way to keep the flow constant until all the nitrous is used, you'd end up with a very long, low flow rate (which would be useless in a micro)?


Epoxy with aluminium powder certainly gives it a nice flame, really need to get a test stand together and get some numbers for it...

Phil

[Bender222]

you could control the speed of the flow could you not? making it fast or slow. I would assume you could throttle the entire engine so that you could have a low thrust long burning engine for altitude flights and a high thrust short burn for speed flights.

[WiK]

But if you're trying to keep the flow constant until depleted, wouldn't the flow have to be really low?

I dunno, I just stick the nitrous charger in the motor and tighten the bolt. ;)

[Bender222]

I guess thats the only way for now. it would be nice to be able to tweak the engine for certain tasks. Any thoughts on the oxidizer to fuel ratio? seeing as how the no2 is always going to be 8 grams, having three grams of fuel seems pretty far from 7/1.

[bobkrech]

I guess thats the only way for now. it would be nice to be able to tweak the engine for certain tasks. Any thoughts on the oxidizer to fuel ratio? seeing as how the NO2is always going to be 8 grams, having three grams of fuel seems pretty far from 7/1.
Bender

Nitrous is N2O, not NO2.

There's only so much you can do with a microhybrid, and it's not much.

The generic combustion balance for nitrous with a hydrocarbon is

3x N2O + (CH2)x ==> 3x N2 + xCO2 + xH2O so the O/F ratio is 9.4:1

In other words 9.4 grams of nitrous is required to burn 1 gram of hydrocarbon. This provides the best heat release and energy per gram of propellant.

Paper or sugar contain oxygen and so the chemical balance is

2x N2O + (CH2O)x ==> 2x N2 + xCO2 + xH2O so the O/F ratio is 2.9:1

Since paper or sugar already contain oxygen (and are partially oxidized already), the combustion produces less energy and is less efficient so you get poorer performance on a propellant weight basis and it takes 2.9 grams of nitrous to burn 1 gram of propellant.

Regardless, the issue is that the microhybrid is really too small to get good performance. As I stated earlier, it is what it is.

Bob

[Silverfish]

I have finally got round to testing the micro hybrid, and boy does it fire well!! My first test was a failure, and a rather stupid one at that. I built the motor, and rigged up a test stand... lit the quick match... the pre-heater burned... and then... nothing! :confused: It was then that I realized that I hadn't tightened the bolt to release the NOX :bang:!!! So anyway, I rebuilt the hybrid, TIGHTENED THE BOLT TO RELEASE THE GAS, and tried again. The second test couldn't have gone any better. The motor lit perfectly (thanks to a combination of quick match and PIC) and then came to life with lots of noise, and it burned for a long time (at least 10 seconds) :wave: (I did film the test, but my camera has broken, so I cannot show you guys the video :()

After this good initial result, I plan to do some experimentation with different fuel grains (I just used a paper one for the test), and I have built an Art Applewhite Stealth saucer (see attached photo) for it to fly in. Ill post updates when I do any further testing.

Silverfish

[WiK]

Hmm, 10 seconds sounds like an oddly long burn. They usually only burn for 3 seconds or so. Did you fire it with the nozzle pointing upwards?

Oh, and you really don't need the Krytox lube for the MH, if the O-rings aren't sliding easily then a bit of spit on them does the trick. Start putting krytox in it and the O-ring lube becomes the most expensive part of the motor. ;)

Phil

[Silverfish]

I have managed to capture another test of the Micro hybrid on video: ne1IgBAuMVc
I think that the short burn time is due to the fact that the first piece of quick match that I used was old, and did not light the PIC. I then had to get a new piece of fuse, and insert it into the motor, all whilst the NOX bulb was pierced. I think this allowed some of the NOX to escape, thus the weak and short burn.

Silverfish

[troj]

You're going to get different burn characteristics with the motor horizontal, as opposed to vertical for flight, as you'll get a shorter period with liquid nitrous going into the burn chamber when the motor is horizontal.

-Kevin

[Bullpup]

Here is my Microhybrid back in 2001 I think.

http://www.rocketsalvo.com/Gallery/main.php?g2_itemId=5521

[Gillard]

there's a micro hybrid system on ebay in the UK at the moment going for £20.
thought 'd let everyone know.