Longest burn time commercial or EX amatuer motors?

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FredA said:
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.
Click to expand...

You are not going to run 2000 psi and long burn unless you use a steel casing.
 
Some you guys probably know this already, but I'll add it as an item of interest for those who don't.

Many of the endburning sounding rockets used silver wire strands suspended longitudinally in the fuel to get more usable thrust. This is one way to get a great mass fraction and L/D ratio as well.
 
I recall one thing about the Arcas motor -- the liner was asbestos.
 
J Blatz said:
Some you guys probably know this already, but I'll add it as an item of interest for those who don't.

Many of the endburning sounding rockets used silver wire strands suspended longitudinally in the fuel to get more usable thrust. This is one way to get a great mass fraction and L/D ratio as well.
Click to expand...

I've done that. I got regression rates of 2.5" per second using wires and ferrocene. Initial thrust was still too low to get it off the pad safely without BATES grains at the bottom, but then a catch 22 was that if you designed for the higher pressure of the bumper grains, the pressure was too low for optimum efficiency for the endburning phase. That's why the ARCAS was gun launched or used with a booster. The real interesting tests I did involved aerospike nozzles in conjunction with the wired grains. I burned through a bunch of 75mm cases before I shelved the project.
 
I dug through some emails. Per email on TRA list the rule was an FAA/AST rule of 15 second burn time. With redo of the rules the limit is now 60 seconds. Happened at the same time as the current codification of the waiver/Class 3 application process was put in place.
 
Back to the original poster's question, I get 17 sec with my 98mm D grains. The propellant is APCP with a burn rate very similar to White Lightning.
Search YouTube for N800.
 
J Blatz said:
Some you guys probably know this already, but I'll add it as an item of interest for those who don't.

Many of the endburning sounding rockets used silver wire strands suspended longitudinally in the fuel to get more usable thrust. This is one way to get a great mass fraction and L/D ratio as well.
Click to expand...

How does the silver wire increase thrust? Does it conduct heat back into the grains about to be burned so the next bit of fuel is easier to light? Something else?
 
My record is an almost 3 minute burn. You could argue whether this was actually a rocket motor....

Of course, the rocket never lifted off the pad. In fact, the motor burned through the case, caught the rocket on fire, which then caught the pad on fire. This was an endburner with a bates grain on the bottom. Worked great in testing. Obviously built the motor improperly, and may have lit it improperly as well.

 
Last edited by a moderator:
boatgeek said:
How does the silver wire increase thrust? Does it conduct heat back into the grains about to be burned so the next bit of fuel is easier to light? Something else?
Click to expand...

I have basically zero knowledge in the field of internal ballistics but this is my guess...

Solid fuel is self oxidizing, so it's not necessarily restricted to burning on the surface. However, that's where the heat is, so that's where it lights. The silver wire might be there to get the inside of the grain to heat up and ignite, making sort of a mini-core burner effect where it burns from both the center and the ends. I would imagine it would form a cone type geometry as heat is conducted back from the nozzle.

I have no idea whether that's actually what it's for- just a guess.
 
Ravenex said:
It seems that it increases thermal conduction and difusivity which increases the rate at which propellant particles ignite.

https://www.tdkpropulsion.com/wp-content/uploads/2010/06/WireLitReview.pdf
Click to expand...

OK, the diagram on pg 3 is pretty much what I was thinking it would do.

I wonder if this is a viable option for turning motors like the I59 or F10 that end-burn into easier to use thrust profiles? Maybe a "dual thrust" style endburn with partial metal threads? I'm thinking something like an I109 that would have a burn profile like CTI Dual Thrust motors that use one Vmax grain, just slower.
 
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.
Click to expand...

The propellant used in ARCAS was Arcite-373D. This is about 80% solids, highly aluminized (21%) propellant. Binder system is not HTPB based, but is actually PVC plastisol. PVC plastisol is a mixture of PVC and plasticizer (dioctyl adipate or dibutyl sebacate). This is not a chemical reaction as PVC is already polimerized. When the propellant is heated to curing temperature the PVC disolves in plasticizer and when cooled solidifies in a flexible plastic material.
ARCAS motor used a steel casing 0,04 inches thick, made from 4130 alloy steel. Thermal insulation was 0,15 inches thick, made from molded asbestos/phenolic. Propellant grain had 19 longitudinal silver wires arranged like this:
- 1 wire in the center of the grain
- 6 wires evenly spaced on 1,60˝dia
- 6 wires evenly spaced on 2,77˝dia
- 6 wires evenly spaced on 3,20˝dia
Aft end of the grain also had a six slots 2,38˝deep arranged in a star patern, to increase the thrust at the beggining. Average chamber pressure was about 1000psi (depending on ambient temperature).
The purpose of the wires in the grain is that the wire (silver is very good heat conductor) preheats the propellant in front of the flame zone. Propellant that is hot burns much faster than cold propellant. Therefore you can get about 4-5 times increase in burn rate. Because the propellant next to the wire burns faster than the propellant in the surounding a conical burning pattern forms around the wire, increasing the burning surface.
 
alexzogh said:
My record is an almost 3 minute burn. You could argue whether this was actually a rocket motor....

Of course, the rocket never lifted off the pad. In fact, the motor burned through the case, caught the rocket on fire, which then caught the pad on fire. This was an endburner with a bates grain on the bottom. Worked great in testing. Obviously built the motor improperly, and may have lit it improperly as well.

[video=youtube;2U2nQwL3Nt4]https://www.youtube.com/watch?v=2U2nQwL3Nt4[/video]
Click to expand...

That wasn't a rocket motor, that was a road flare stuck in a saucer... :tongue: :tongue: :lol:
I remember that well.
 
Andrew_ASC said:
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.
Click to expand...
Hay how much each for the 40 second burn
 
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...
ISP’s Pegasus Fin Motors were 5” diameter end burners using 8223AL (Warp-9) propellant and a tapered phenolic liner. Phenolic nozzle with a graphite insert. 20-22 second burn.
 
alexzogh said:
My record is an almost 3 minute burn. You could argue whether this was actually a rocket motor....

Of course, the rocket never lifted off the pad. In fact, the motor burned through the case, caught the rocket on fire, which then caught the pad on fire. This was an endburner with a bates grain on the bottom. Worked great in testing. Obviously built the motor improperly, and may have lit it improperly as well.

Click to expand...


Nice long burn. I fixed the link.
 
I'm next to my 159mm Super Hippo motor that burned 54 seconds and 36 seconds both times utilizing the Moon burner grain developed by Bill Wood. The casing was insulated with SiO2 & CB filled EPDM. For further details download Bill Wood's Report on Moonburners from the RCS website.
 

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