Level 3 Cert with Cable Cutter?

[grizzly]

I reviewed the level 3 cert rules regarding deployment at the NAR and Tripoli websites.

Obviously, electronic deployment is required for the level 3 cert from both organizations.

Would a motor deploy,drogueless, cable cutter type arrangement chute deployment pass muster for level 3 cert for either organization, or is this a grey area at this time?

 

[daveyfire]

Would a motor deploy,drogueless, cable cutter type arrangement chute deployment pass muster for level 3 cert for either organization, or is this a grey area at this time?

There are no presently certified M, N, or O motors with a motor deploy option.

 

[Area66]

If you want to pass a lev3 you have to submit your project to a committee for approval, for Tripoli it's the TAP (Technical Advisory Panel)

 

[troj]

Would a motor deploy,drogueless, cable cutter type arrangement chute deployment pass muster for level 3 cert for either organization, or is this a grey area at this time?

NFPA 1127 does not allow for motor ejection in motors that large.

In addition, I'd have concerns about a drogueless deployment being able to extract a main that was using a cable cutter.

-Kevin

 

[rocketgeek101]

I presume he didn't use motor deploy, but I believe this guy did his level 3 cert with a cable cutter:
[video=youtube;ytXc0egQkgE]https://www.youtube.com/watch?v=ytXc0egQkgE[/video]

 

[grizzly]

Yes thanks, but is it possible for CTI or Aerotech to include a delay in a 75mm M class motor?

If so, theoretically speaking for now, would the scenerio above likely pass muster for a level 3 cert?

 

[lkal32]

I presume he didn't use motor deploy, but I believe this guy did his level 3 cert with a cable cutter:
[video=youtube;ytXc0egQkgE]https://www.youtube.com/watch?v=ytXc0egQkgE[/video]

That looks more like a tether. The Cable Cutter 'typically' has the chute out into the airflow already, and it would appear to just burst open and inflate. The chute in the video (@ 3:30) comes out of the main body tube.

 

[daveyfire]

Yes thanks, but is it possible for CTI or Aerotech to include a delay in a 75mm M class motor?

If so, theoretically speaking for now, would the scenerio above likely pass muster for a level 3 cert?

Kevin already answered this:

NFPA 1127 does not allow for motor ejection in motors that large.

Speaking as a TAP and a "motor guy", I would not sign off on a L3 project using motor ejection. Delay columns can be highly susceptible to timing errors (cf. ±20% requirement in NFPA 1125) and on a project that large, a deployment timing error involves unsafe levels of energy. If you can't afford $70 for a Missileworks or Perfectflite altimeter, you can't afford to do an L3 project safely.

 

[troj]

A minor correction -- NFPA 1127 requires that rockets with an M or above have electronics as the primary or backup:

4.10.2 A high power rocket launched with an installed total impulse greater than 2560 N-sec (576 lb-sec) shall use an electronically actuated recovery system as either a primary or backup deployment method.

I'm not a TAP, but I am a Prefect and even if the rules permitted it and the motors existed, I'd have serious concerns about something doing an M+ flight with motor ejection at our launch site.

I'm not sure what the motivation is to avoid electronic deployment, but if it's to save money then I'd have to question why you're even interested in attempting Level 3.

As far as delays go, CTI cases in 75mm and larger are all plugged forward closures. AeroTech I think used to make some 75mm without plugged forward closures but I haven't seen one in a long time. None of the production hardware from Rouse-Tech, CTI or Loki has the capacity for an ejection charge in 75mm and larger.

-Kevin

 

[grizzly]

A minor correction -- NFPA 1127 requires that rockets with an M or above have electronics as the primary or backup:



I'm not a TAP, but I am a Prefect and even if the rules permitted it and the motors existed, I'd have serious concerns about something doing an M+ flight with motor ejection at our launch site.

I'm not sure what the motivation is to avoid electronic deployment, but if it's to save money then I'd have to question why you're even interested in attempting Level 3.

As far as delays go, CTI cases in 75mm and larger are all plugged forward closures. AeroTech I think used to make some 75mm without plugged forward closures but I haven't seen one in a long time. None of the production hardware from Rouse-Tech, CTI or Loki has the capacity for an ejection charge in 75mm and larger.

-Kevin

I'm not sure where you and Dave are getting the idea that this is a money issue?
To be clear, I am talking about using a dual Archetype Cable cutter set up with dual altimeters.
This is a new area to explore, obviously.

 

[grizzly]

A minor correction -- NFPA 1127 requires that rockets with an M or above have electronics as the primary or backup:
-Kevin

This is a pretty major correction as it pertains to this discussion. Not that it matters, as it fits at least the back up criteria, but would the cable cutter be reguarded as the primary or back up?

It would appear that the only limitation placed on this idea is the lack of available motor ejection on M class or above motors. That is, unless someone can quote a Tripoli or NAR rule against it?

 

[daveyfire]

I'm not sure where you and Dave are getting the idea that this is a money issue?To be clear, I am talking about using a dual Archetype Cable cutter set up with dual altimeters.This is a new area to explore, obviously.

I'm having trouble understanding why you would want to use a pyrotechnic delay when a far more reliable and accurate system is already on board? Delays used in hobby rocket motors are far from, e.g., delays used for ordinance timing.Aerotech used to make 98mm motors with delay and ejection. Rarely, if ever, did I see one work as designed and fire on time. If you have the equipment on board to perform electronically-controlled apogee ejection, why not use it?

 

[rdbones]

that is, unless someone can quote a Tripoli or NAR rule against it?

From the TRA Certification Document - Section Level 3 Subsection Electronics

"Electronics
– Prior to a level 3 certification flight, the flyer shall successfully fly at least one rocket in the level 2 range using an electronic device as the primary means of recovery
system deployment. Level 3 certification flights shall include at least two completely separate electronic devices, with independent power sources, wire harnesses, and
ignition devices for the primary and back-up means of recovery system deployment.

The way I read this - TRA has a rule against it.

 

[grizzly]

From the TRA Certification Document - Section Level 3 Subsection Electronics

"Electronics
– Prior to a level 3 certification flight, the flyer shall successfully fly at least one rocket in the level 2 range using an electronic device as the primary means of recovery
system deployment. Level 3 certification flights shall include at least two completely separate electronic devices, with independent power sources, wire harnesses, and
ignition devices for the primary and back-up means of recovery system deployment.

The way I read this - TRA has a rule against it.

The way I read it, it does not.

 

[rdbones]

The way I read it, it does not.

How does that not when both the Primary and Secondary means of recovery system deployment require electronic devices?

Motor Eject is NOT electronic in nature !

 

[grizzly]

Aerotech used to make 98mm motors with delay and ejection.

Interesting. So it is indeed possible for them to do so, as they have done it in the past. I'm sure CTI could do it as well.

Would said motor have to be recertified by Tripoli and NAR?

 

[Area66]

I don't build motors ejection rockets anymore since I discover altimeter. Even my Mid-power Aerotech are now using altimeter. A M motor with motor ejection !!!!

 

[daveyfire]

Interesting. So it is indeed possible for them to do so, as they have done it in the past. I'm sure CTI could do it as well.

Would said motor have to be recertified by Tripoli and NAR?

Yes, it would. But the motors were discontinued due to reliability reasons. And so far, three certifying authorities on this thread have said they wouldn't accept it. What application are you thinking about that would need a pyro delay?

 

[Area66]

Would said motor have to be recertified by Tripoli and NAR?

this guy is a troll for sure

 

[DizWolf]

Interesting. So it is indeed possible for them to do so, as they have done it in the past. I'm sure CTI could do it as well.

Would said motor have to be recertified by Tripoli and NAR?

I'm confused as to why you'd want to go through the effort of trying to get the manufactures to go back to an old style of motor, that they stopped making and would need to be certified. Especially when you would have a much more accurate and effective means onboard already to fire off the cable cutters. Most altimeters will fire multiple events. Drop an apogee charge off each one, and a cable cutter on each one. Why the need (desire?) to go motor eject?

 

[grizzly]

2.3 Each parachute event must be initiated by redundant control systems. Redundancy must
be present in the power sources, safe and arm provisions, control logic, and output devices
(e.g. bridgewires, electric matches). Redundancy is not required in the energetic materials
(e.g. black powder charges), parachutes, attach points, risers, and disconnects. Motor
ejection charges may be used as a redundant system, but rockets depending primarily on
motor ejection for any recovery event are specifically disallowed. A safe rate of decent.
(20ft/ second is recommended) for any component weighing in excess of eight ounces.

It looks like NAR would not allow motor eject either. Excellent help guys, thanks.

I was considering getting my level 3 on a PML AGM 600 Pitbull strengthened with the PML fiberglass option to the airframe, .125 inch G10 fin option, and the 75mm motor tube. Nosecone and fincan strengthened with PML expanding foam. I really like the PML piston motor eject system, so I wanted to try to incorporate that, in conjunction with a cable cutter set up in the nosecone. Many ways to skin a cat, or so I thought.

 

[troj]

I was considering getting my level 3 on a PML AGM 600 Pitbull strengthened with the PML fiberglass option to the airframe, .125 inch G10 fin option, and the 75mm motor tube. Nosecone and fincan strengthened with PML expanding foam. I really like the PML piston motor eject system, so I wanted to try to incorporate that, in conjunction with a cable cutter set up in the nosecone. Many ways to skin a cat, or so I thought.

With a bit of creativity, I'm sure you could modify the kit to allow you to still use the piston, but use electronics to fire the ejection charges instead of using something from the motor.

-Kevin

 

[bobkrech]

Yes thanks, but is it possible for CTI or Aerotech to include a delay in a 75mm M class motor?

If so, theoretically speaking for now, would the scenerio above likely pass muster for a level 3 cert?

No. Theoretically speaking it is not possible.

You must used a certified M, N or O motor for a L3 cert flight, and S&T, TMT and MTC will not certify any motors larger than K-impulse with an ejection charge because they are not permitted by NFPA 1125 and NFPA 1127 which is bases for the high power safety codes of NAR, TRA and CAR.

End of story.

Bob Krech, NAR S&T

 

[ClayD]

I know people who are concreted into motor eject. I however, kind of have a tad of ughhh!!! about them... Ew its iky....(the motor eject... NoT the rocket guys that like motor eject.......well maybe... i am not sure.... )

I like sensing the lowest velocy to separate my rockets, than to try to predict when it will occur. On a 7 second flight, its fairly easy 20% is not a big deal..(8.4 second apogee.) 1.4 seconds isnothing on a 1lb rocket.. Hey, if your a second off who cares.....

Could you imagine being 6 seconds off of a 30 second apogee.......couple 6 seconds of freefall acceloration with a 100mph apogee velocity, and you have a FAIL.


If you are going to fly cable cutters, you should be able to use a single separation point, and tie the main as a drouge. Use your Dual Deploy altimeter as the Apogee charge, then the line cutter at main altitude...

I love my line cutter... Archtype makes good stuff.

 

[MClark]

When the cert 3 rules were first done they were different. I signed off at least one AT M1939 using motor eject for a level 3, a simple timer as a back up.
I used to have the AT 98 with the eject forward closure until someone drilled it into the ground using electronics that failed

Mark

 

[grizzly]

Mark,

Thanks for the reply. I was beginning to question my sanity.:wink:

 

[grizzly]

With a bit of creativity, I'm sure you could modify the kit to allow you to still use the piston, but use electronics to fire the ejection charges instead of using something from the motor.

-Kevin

Let me run this by you.

1. Use the rather large piston for dual purposes.
-create an av bay by putting a bulkhead with aft firing charges at the aft end of the piston.

2. Put another av bay in the large nosecone for the cable cutter.

Or

1. Av bay in nosecone for cable cutter as above.

2. Second av bay aft of forward centering ring with cargo bay access between aft fins.


Looking at 4 alts either way.

 

[Reinhard]

With a bit of creativity, I'm sure you could modify the kit to allow you to still use the piston, but use electronics to fire the ejection charges instead of using something from the motor.

I think Denis' approach (electronics between motor tube and body tube) should be quite suitable here:
https://www.rocketryforum.com/showthread.php?45220-Madcow-Mega-Cowabunga-XXL
https://www.rocketryforum.com/showthread.php?46433-8-inches-V2

Adrian's concept (electronics on top of the motor) might be adapted too, but some details will get tricky to figure out (e.g. proper venting of the barometer, arming on the pad):
https://www.rocketryforum.com/showthread.php?26383-Level-3-high-performance-design-and-build-thread

Reinhard

 

[Reinhard]

Let me run this by you.

1. Use the rather large piston for dual purposes.
-create an av bay by putting a bulkhead with aft firing charges at the aft end of the piston.

2. Put another av bay in the large nosecone for the cable cutter.

I guess, you could do both with the same ebay. Use a long shock cord between the piston and the lower part of the rocket, and connect the parachute directly (or with a short shock cord) to the ebay/piston. In any case, make sure that you can power on the electronics after you have assembled the rocket. Otherwise, you have a high chance of triggering the altimeter due to the pressure changes inside the rocket when you push in the piston (something I've seen twice so far). If you want to be extra safe, keep the piston in place with shear pins until the apogee charge fires.

Reinhard

 

[grizzly]

I guess, you could do both with the same ebay. Use a long shock cord between the piston and the lower part of the rocket, and connect the parachute directly (or with a short shock cord) to the ebay/piston. In any case, make sure that you can power on the electronics after[/IB] you have assembled the rocket. Otherwise, you have a high chance of triggering the altimeter due to the pressure changes inside the rocket when you push in the piston (something I've seen twice so far). If you want to be extra safe, keep the piston in place with shear pins until the apogee charge fires.
Reinhard

I like this idea. The Raven has a magnetic switch that I could use to arm the altimeters on the rail. Due to its small size, two should fit easily in the piston. Very efficient. Tracker in nosecone if needed.

I'm wondering if this arrangement would effect the function of the piston?