cross brand 75mm and 98mm

I am greatly interested in cross brand reloads at 75mm and 98mm.

Cesaroni lists certain reloads, maybe 20%, as compatible with Aerotech and Monster hardware. However, they sort of imply that all their 75mm and 98mm reloads work like this. Is it simply a matter of testing and certification, or do you need to stick to the listed subset? I do understand needing to stick to certified combinations at regular, non EX launches, but I want to understand how these work physically.

Here's a link to a useful reference...

https://www.nar.org/wp-content/uploads/2014/08/CasingCrossCert.pdf

Is there a CTI reload for the AT style 75/7680 motor???

crossfire said:

Is there a CTI reload for the AT style 75/7680 motor???

Click to expand...

Isn't it simply a 6 grain case? There's a long list.

I am not sure.A guy offered to sell me a 7680 AT case. I looked on AT site and only saw 1 reload from them.

crossfire said:

I am not sure.A guy offered to sell me a 7680 AT case. I looked on AT site and only saw 1 reload from them.

Click to expand...

I have one of the 7680 cases, and I *assumed* that the CTI reloads would work. I'd like to hear from someone here that's actually done it.

There is at least one new load for that case.

https://www.rocketreviews.com/aerotech---m685w-ps-reload-for-rms-75-7680.html

CTI 75 and 98 hardware is generally* compatible with AT. CIT initially made reloads for AT hardware and certified them as such. After a point, they stopped cross-certifying. One story they give is that it's expensive (they need to burn 3 loads in each set of hardware, and for Ms and Ns it can get expensive). If you are flying at a research launch, you can use any reloads with any hardware in 75 and 98mm. At a certified launch**, you can use only the combinations CTI lists here:https://www.pro38.com/faqs.php#certification

Ari.

*The exceptions are reloads that physically won't fit, e.g., Pro98-6G is the same size as RMS98/15360, but CTI makes one size larger, Pro98-6GXL, which has no equivalent in AT.
**I have reason to believe people at Snow Ranch (non-research and non-TRA launch) have flown non-certified combinations of reloads and hardware. While it is against the rules, and may mess with insurance, it is perfectly safe--well, as safe as any high-power rocketry launch can be.

Thanks Ari - good reference.

So, according to this, the Pro75® M1770-P Skidmark™ is certified for the AT 75-7680 case.

That's a motor I'd love to see fly.

Lots of great information so far!

If I read this correctly, does it follow that I could use a Cesaroni spacer in a 98mm3G case down to 2G and use an RMS 98/5120 reload? If I take a small leap of faith, what about a Cesaroni spacer to turn a Monster 75/5120 into 75/3840 and then use a Cesaroni 3G or Aerotech 75/3840 reload? I expect none of this is certified, research EX of course.

I thought you can use CTI reloads in either CTI or Aerotech/Dr Rocket/Rouse tech 75/98 mm hardware, but not the other way around. CTI gives you the o-rings to use in either hardware, but AT only gives you o-rings for their cases...
Spacers are a whole nuther bag o issues. Jeroen will have to weigh in on those.

Adrian

While it may be physically possible (they fit) to interchange either way, the CTI-AT cross certification has to date been only in one direction... CTI reloads in AT hardware. So, those of us that are NAR-only can only use the certified combos and can't swing both ways.

Unsolicited testimonial... I have twice flown the CTI N3180 (98-6G red) in AT 98-15360 hardware, the M3400 (98-4G WT) in AT 98-10240, and numerous CTI L3150 (98-2G Vmax) in AT 98-5120. Never had an issue. I believe that as long as the liner length, including seal discs and nozzle, fits correctly between that closures, the propellant won't know the difference. The different supplied O-rings factors in here as well, and may make up any minor case length difference involved. So with the correct set of O-rings, the research guys in the crowd can try it either way.

Note - the N3180 uses a different, longer nozzle (without the nozzle carrier when used with CTI hardware), and CTI marketed an AT-threaded aft closure specifically for use of this motor in the AT case. (IIRC the M3400 recently changed nozzle types as well and may have affected cross-certification.) Neither motor is currently listed as cross-certified, although they had been previously.

I have flown multiple AT N2000s in a 6 grain CTI case with no issues. I just purchase some extra buna o-rings on McMaster that fit the CTI nozzle holder. Whether this is certified - no idea...most launches are EX these days anywho. Call CTI to make sure compatibility will work - they are awesome.