Longest burn time commercial or EX amatuer motors?

Onebadhawk
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Andrew_ASC

Andrew_ASC

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Any type. Any class. Sounding rockets are making these amatuer motors pale in burn time. 20-40s+. So what's the longest burn motors tried? I could care less about matching the thrust curve. I'm thinking any APCP fuel ran that long would melt an aluminum casing or hit a maximum specific impulse barrier allowed.

Pulled up 325 lbf at 1020 psi chamber pressure off an Arcas at 29s.
Warp 9 does 340 lbf at unk pressure out of a I class 38-480 for 0.3s.
The rest blows my mind looking past Arcas specs of burn times today much less thrust specs.
Randomly got curious.
 
Kosdon made a few 42 second I motors. End burn. Thick Phenolic case, burned halfway through. Next step that never happened was to taper case thickness to reduce weight.
At end of burn graphite nozzle was glowing.

M
 
MClark said:
Kosdon made a few 42 second I motors. End burn. Thick Phenolic case, burned halfway through. Next step that never happened was to taper case thickness to reduce weight.
At end of burn graphite nozzle was glowing.

M
Click to expand...

I was going to shoot off my mouth Mark but I caught the phenolic case so I quess it was one time use eh? Would carbonize the back end of a cardboard rocket to charcol?
I did a one time use 24mm high L/D aluminum case and the nozzle crumbled after the test burn. It burned in <1 sec though. Aft snap ring bowed out and was just about to let go. Kurt
 
Do you have any ideas of how long the kosdon casing was?
 
MClark said:
Kosdon made a few 42 second I motors. End burn. Thick Phenolic case, burned halfway through. Next step that never happened was to taper case thickness to reduce weight.
At end of burn graphite nozzle was glowing.

M
Click to expand...

What the heck would one fly that in? Come in around 15N avg? Or did I botch something?
 
Ksaves, yes to all.
I need to make a correction. The 42 sec burn motor was referred to as H8 (yea, works out to a light I) and there was a I19 with ballpark a 30 second burn.
H8 propellant was cast into standard 29mm casting tube, the I into 38mm. Rough estimate at 0.3"/sec 12.6" would be required for 42 seconds.
We did 20 second burn 4" motors with bates grains and a double secret AN propellant .
 
rstaff3 said:
What the heck would one fly that in? Come in around 15N avg? Or did I botch something?
Click to expand...
Used Estes tube and nose cone, tube launched with piston and black powder boost charge. Motor diameter was nonstandard but the I fit nicely into 1.6" tube.
 
Roxel Group might manufacture some of that stuff. Whatever your referencing I don't think is normal ANCP or APCP. NATO had some burn test on FOX fuel and its smokeless. HMX explosives additives. Doubled based nitro stuff. Google has patents on rocket motors for 2.75" application (Folding fin aerial rocket???) Crosslinked stuff I never even heard of that doesn't use AP. Then this at Roxel's page for tactical missiles and other military applications.

Never seen pictures of a yellow black spotted rocket fuel before. I don't want to know. LOL.
 
There is tons of info out there on the ARCAS, some references to the propellant, but I haven't been able to find anything even resembling a formula. :(
 
MClark said:
Used Estes tube and nose cone, tube launched with piston and black powder boost charge. Motor diameter was nonstandard but the I fit nicely into 1.6" tube.
Click to expand...

There's some old-school craziness. I like it!
 
At reasonable pressure, say, 500-1000psi, APCP generally burns in the range of 1/8"/sec to 3/4"/sec depending on formulation, roughly speaking. Wired, it can go up to around 2 1/2"/sec. The rest would be obtained by geometry of the grain.

For instance, a propellant which burns at 3/16"/sec in a 6" diameter motor (say, 5 1/4" propellant OD) with a 1.25" core, would burn for approximately 11 seconds.

Our motors aren't large enough diameter to get really long burn times with bates or other cored geometries, without badly degrading the delivered ISP.

For end-burning though, the problem is getting enough thrust to be useful. That requires very fast burning propellant which puts it out of the range of what most amateurs could reliably produce. Then if you've got the thrust, well, in the same size case, you'll end up with roughly the same burn duration. There is only so much oomph you can stick into the case.

Astrobee-D motor, going by memory: 8' long. 6" diameter. Approx 220# loaded, 180# propellant. Burn duration, as a dual-thrust, of 13 seconds. That's well within amateur range of production. I'm probably off in my numbers somewhere but you get the point. Size matters. You get longer burn for sounding rocket motors because the grain(s) are bigger, but the burn rate is the same range as ours.

Gerald
 
G_T said:
At reasonable pressure, say, 500-1000psi, APCP generally burns in the range of 1/8"/sec to 3/4"/sec depending on formulation, roughly speaking. Wired, it can go up to around 2 1/2"/sec. The rest would be obtained by geometry of the grain.

For instance, a propellant which burns at 3/16"/sec in a 6" diameter motor (say, 5 1/4" propellant OD) with a 1.25" core, would burn for approximately 11 seconds.

Our motors aren't large enough diameter to get really long burn times with bates or other cored geometries, without badly degrading the delivered ISP.

For end-burning though, the problem is getting enough thrust to be useful. That requires very fast burning propellant which puts it out of the range of what most amateurs could reliably produce. Then if you've got the thrust, well, in the same size case, you'll end up with roughly the same burn duration. There is only so much oomph you can stick into the case.

Astrobee-D motor, going by memory: 8' long. 6" diameter. Approx 220# loaded, 180# propellant. Burn duration, as a dual-thrust, of 13 seconds. That's well within amateur range of production. I'm probably off in my numbers somewhere but you get the point. Size matters. You get longer burn for sounding rocket motors because the grain(s) are bigger, but the burn rate is the same range as ours.

Gerald
Click to expand...

Hi Gerald,
I see Catocene and Ferrocene is available at RCS now. Yeah, my jaw dropped when I saw that and I hear some are working with it now. I think Dr. Frank
had the concept right, single use. I believe the idea of a tapered case like Mark mentions above would be needed to pull this of consistently.
That would be a tough nut to crack economically along with the SU graphite nozzle. An inquisitive experimenter could pull it off I bet but it would be an
investment on a relatively lone burning low powered motor. Kurt
 
But a sounding rocket is fundamentally different. If you compare the same fuel APCP type to other, the sounding rocket wins on volumetric efficiency because the airframe is the casing and it's R radius value is always slightly more than negligibly larger than a hobby rocket with a casing restricting radius. Perhaps amatuers could advance to liner bonded carbon fiber or aluminum airframes someday.
 
ksaves2 said:
That would be a tough nut to crack economically along with the SU graphite nozzle. An inquisitive experimenter could pull it off I bet but it would be an investment on a relatively lone burning low powered motor. Kurt
Click to expand...


Scale it down to 13-18mm size. And economically it's not so bad to tinker with. It would be small enough that a drill press could make crude nozzles rapidly with less machining. You may be able to find 1" tubing extruded aluminum cheaper to play with than odd ball metric hobby tube sizes. That Catocene is still $70 a bottle.
 
MClark said:
Yes.
But not at that time.
Click to expand...

I really meant my question as trivia, not an effort to catch someone in the act. [emoji4]
Do you remember whose requirement that was and why, Mark? It always seemed odd to me. I thought it was still in place when CTI came out with their 15 second moonburner and changed soon after.
 
Andrew_ASC said:
But a sounding rocket is fundamentally different. If you compare the same fuel APCP type to other, the sounding rocket wins on volumetric efficiency because the airframe is the casing and it's R radius value is always slightly more than negligibly larger than a hobby rocket with a casing restricting radius. Perhaps amatuers could advance to liner bonded carbon fiber or aluminum airframes someday.
Click to expand...

Check out some BALLS projects.

Liner bonded is no problem at all. Case bonded is more fun. And motor as airframe is pretty standard.

Gerald
 
That giant spinning bamboo rocket from Thailand that someone posted here last year had about 45 seconds of thrust.
 
Andrew_ASC said:
It just has more propellant in the same volume.
Click to expand...

No, it's not that simple. The small sounding rockets typically ran at higher pressures than commercial HPR motors. With the added fwd/aft insulation, monolithic grains, and single-use design, you can get a lot more N-secs in a rocket the same size as a min-diameter HPR.
 
With the added fwd/aft insulation, monolithic grains, and single-use design, you can get a lot more N-secs in a rocket the same size as a min-diameter HPR.

All that has been done by amateurs.
We just can't run the pressure as high in 6061-T6 cases.
 

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