what the heck is imax

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watermelonman

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I can find mention of Cesaroni Vmax all over the place, and it seems fairly obvious that the V is for velocity, but what the heck is Imax? The only places I see it mentioned describe the flame color and burn duration. It does not look like the I is for impulse, but maybe. Image? It does look cool if nothing else.
 
From Cesaroni web site:
The Imax™ propellant packs the maximum total impulse in a given motor envelope (hence the name). The total impulse of Imax™ reloads is about 10-15% higher than that of any other reload in the same motor hardware. Imax™ reloads feature a large flame – with a hint of green and lot’s of dense smoke. The performance of Imax™ is obvious from the large total impulse of our 6GXL reload: 1115 Ns! This is 44% more total impulse than the largest Pro38® reload available prior to the 6GXL case size release!
 
I can find mention of Cesaroni Vmax all over the place, and it seems fairly obvious that the V is for velocity, but what the heck is Imax? The only places I see it mentioned describe the flame color and burn duration. It does not look like the I is for impulse, but maybe. Image? It does look cool if nothing else.

Imax is the coolest looking, best-performing smoky motor available.
 
From Cesaroni web site:
The Imax™ propellant packs the maximum total impulse in a given motor envelope (hence the name). The total impulse of Imax™ reloads is about 10-15% higher than that of any other reload in the same motor hardware. Imax™ reloads feature a large flame – with a hint of green and lot’s of dense smoke. The performance of Imax™ is obvious from the large total impulse of our 6GXL reload: 1115 Ns! This is 44% more total impulse than the largest Pro38® reload available prior to the 6GXL case size release!

Weird, when I look at their propellent types page about 25% of them show with title and broken image logo only. Sorry about that, the answer was in the obvious place all along!
 
I think that's out of date - C-Star seems to have a higher ISP on all the reloads I've looked at.
 
Not sure that's actually helpful for the performance of the rocket though. Even if you get more newton-seconds the fact that the propellant weighs more negates any benefit from the extra power. You're actually worse off with an Imax in the end.
 
C* will have better Isp, but the product of density and specific impulse means you can pack more total Newton-seconds in the case with Imax. It's a neat trick :)

Yes, I believe the CTi L935 is the most NS you can get in a commercial 54 mm motor in California. Have burned one, have another for the right occasion.
 
Not sure that's actually helpful for the performance of the rocket though. Even if you get more newton-seconds the fact that the propellant weighs more negates any benefit from the extra power. You're actually worse off with an Imax in the end.


L935 is 3.4 seconds of kickass power baby! Yeah.
 
Not sure that's actually helpful for the performance of the rocket though. Even if you get more newton-seconds the fact that the propellant weighs more negates any benefit from the extra power. You're actually worse off with an Imax in the end.

It depends on the mass of the rocket. Looking at the rocket equation shows, that the lighter the rocket becomes, the more important Isp becomes in relation to total impulse - and vice versa. If you compare, for example, the N5800 C-Star with the O3400 Imax (both in the same Pro98-6GXL casing), you'll find out that the N5800 will deliver the better performance for rockets up to about 10kg (22lbs). In heavier rockets, the O3400 will perform better.

N5800_O3400-.png

Note, the graph is only based on the rocket equation and ignores things like drag and gravity losses which are dependent on additional factors like the burn time.


Reinhard
 
It depends on the mass of the rocket. Looking at the rocket equation shows, that the lighter the rocket becomes, the more important Isp becomes in relation to total impulse - and vice versa. If you compare, for example, the N5800 C-Star with the O3400 Imax (both in the same Pro98-6GXL casing), you'll find out that the N5800 will deliver the better performance for rockets up to about 10kg (22lbs). In heavier rockets, the O3400 will perform better.

View attachment 247665

Note, the graph is only based on the rocket equation and ignores things like drag and gravity losses which are dependent on additional factors like the burn time.


Reinhard

So for example, if one was to do a crazy 2-stage with Pro98-6GXL motors, you'd want an Imax on the bottom and C-star on the top.

Apparently the same thing is true down to 38mm motors: if you count the impulse per total loaded mass, the J420 Classic has better performance than the J530. But you'd want a J530 on the bottom because there the impulse matters more than Isp.
 
watermelonman said:
It does not look like the I is for impulse, but maybe.

I think that's out of date - C-Star seems to have a higher ISP on all the reloads I've looked at.

Ah! That explains why I thought I was not for impulse; one of the other propellants is now higher in that category.
 
Ah! That explains why I thought I was not for impulse; one of the other propellants is now higher in that category.
Specific impulse (Isp) is different than total impulse. CStar is more efficient pound-for-pound than Imax, so its specific impulse is higher. However, because of its density, you can fit more pounds of Imax propellant in a given size case, so the total impulse of many Imax reloads ends up higher than that of the equivalent CStar load.

It's kind of like getting better gas mileage (CStar) vs. having a bigger gas tank in the same size car (Imax). Imax is usually the total impulse winner, hence the name-- maximum impulse.
 
It depends on the mass of the rocket. Looking at the rocket equation shows, that the lighter the rocket becomes, the more important Isp becomes in relation to total impulse - and vice versa. If you compare, for example, the N5800 C-Star with the O3400 Imax (both in the same Pro98-6GXL casing), you'll find out that the N5800 will deliver the better performance for rockets up to about 10kg (22lbs). In heavier rockets, the O3400 will perform better.
Interesting stuff! Big N's/baby O's, something like that. ;)

So for example, if one was to do a crazy 2-stage with Pro98-6GXL motors, you'd want an Imax on the bottom and C-star on the top.
Or do as Neil Anderson did at BALLS this year which was C-Star in the booster and White Longburn in the sustainer. (Again, both 98mm-6XL.) That worked well enough...
 
My one and only experience with Imax wasn't very good. Granted, the rocket had a great flight - it really whipped my Thor clone off the pad! Everything looked normal, all events happened on time, although there seemed to more smoke than normal during the coast after main motor burnout.

After getting the rocket back, I removed the motor and found it had burned through the casing - Imax is powerful stuff. Unfortunately, my Thor was totally cooked inside. Ken from Performance Hobbies warrantied the motor case, so I am back in business. My favorite reload in the 38mm 6xl size is the J453W.

Not sure if this has happened to anyone else with this propellant? After flying hundreds of motors, this has been my only failure so far. I've avoided using Imax ever since.

imax1.jpg

imax2.jpg
 
Not sure if this has happened to anyone else with this propellant? After flying hundreds of motors, this has been my only failure so far. I've avoided using Imax ever since.

Yes....if it was the 6xl 38 [J-530?] there was a recall on a batch of them last year, due to bad casting tube.

Check with your dealer to be sure it was this load, you should get a replacement case & a load for it.

All other sizes were fine and so are the one's made since.
 
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Yes....if it was the 6xl 38 [J-530?] there was a recall on a batch of them last year, due to bad casting tube.

Check with your dealer to be sure it was this load, you should get a replacement case & a load for it.

I did get the case replaced under warranty. I actually declined to get a replacement J530 reload - somehow it wouldn't feel honest as I wasn't even aware there was an issue until I removed the motor after recovery. The rocket flew great, I think the burn through must have happened in the last fraction of a second. The insides are cooked, but it was actually a very good flight. Had it exploded on the pad, that would have been a different story and I certainly would have accepted a replacement reload.
 
IMAX is my favorite and has a awesome flame and smoke. Have done a couple of M2020's and L935's in my 6" Kraken.

Ekraken1.jpg
 
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