Rocketry Planet

WORLD WIDE WEB — New high power certifications were announced today for three motor manufacturers by Tripoli Motor Testing, which included AMW Pro-X, AeroTech and Gorilla Rocket Motors.  The new motors ran the gamut from motors as small as a one-grain G motor all the way up through an N-class sparky motor, the largest motor TMT has tested to date.

The N-class motor, marketed by AMW Pro-X Distributors as an N2801, produced 2775.6 Newtons of average thrust, earning it a TMT designation of N2876.  The 48-inch long 98MM motor, a 17% N motor, uses over 16 pounds of propellant and fits the "AMW Classic" 98-17500 hardware.  In his announcement, Paul Holmes stated the huge N sparky "is a monster motor," the largest motor TMT has certified since the AeroTech 98/18000 N4800T.

AMW Pro-X
N2876SK-PS
98-17500
-------------------------
17% N
Total NS: 11,939.73 NS
Max N: 4,199 N
Burn Time: 5.2 seconds
AverageN: 2775.6
Weight: 13.675 Kg (30.15#)

AeroTech Consumer Aerospace was granted a certification for an L1390 Mojave Green motor, a 54.2% L, which fits the 75-3840 case.

AeroTech
L1390G-PS
75-3840
-------------------------
54.2% L
Total NS: 3948.677 NS
Max N: 1813.99 N
Burn Time: 2.58 seconds
AverageN: 1501.16
Weight" 4.104 Kg (8.85#)

Another series of sparky 38mm motors was certified for AMW Pro-X, 1, 3, 4, 5 and 6-grain variants.  The 2-grain variant was certified last year by CAR.  These reloads fit the AMW Pro-X 38mm motor case, which is a CTI Pro-style case, making the motors available for use in AMW Pro-X and CTI Pro38 hardware.

The 1-grain G69SK was retested by TMT after failing to meet NFPA guidelines for propellant weight to be classified as a high power rocket motor, since the motors produced sparks and couldn't be classified as model rocket motors.  It was the first time a rocket motor fell into an unknown "classification hole" in the NFPA guidelines. 

By raising the motor's propellant weight above 62.5 grams, the motor was able to certified as a high power motor, but it now unfortunately requires a federal explosives permit for purchase, severely limiting the motor's marketability. Note: All earlier G69SK motors previous sold are now "grandfathered" into this certification and shall be allowed to be flown under the high power rules recognized by NAR, TRA and CAR.

AMW Pro-X
G69SK-14A
AMW Pro-X 1G/Pro38-1G
-------------------------
46% G
Total NS: 117.149009 NS
Max N: 91.963344
Burn Time: 1.844582
AverageN: 63.607944
Weight: 198 g

AMW Pro-X
I180SK-14A
AMW Pro-X 3G/Pro38-3G
-------------------------
5% I 
Total NS: 338.42606
Max N: 212.967744
Burn Time: 1.873334
AverageN: 180.907808
Weight: 394g

AMW Pro-X
I223SK-14A
AMW Pro-X 4G/Pro38-4G
-------------------------
35% I
Total NS: 434.050419
Max N: 264.28461
Burn Time: 1.94375
AverageN: 223.392047
Weight: 494g

AMW Pro-X
I297SK-15-A
AMW Pro-X 5G/Pro38-5G
-------------------------
68% I
Total NS: 542.80032
Max N: 375.93867
Burn Time: 1.829582
AverageN: 296.728581
Weight: 591g

AMW Pro-X
J381SK-15A
AMW Pro-X 6G/Pro38-6G
-------------------------
3% J
Total NS: 659.86024
Max N: 503.10276
Burn Time: 1.734584
AverageN: 380.571387
Weight: 688g       

Jim Harris of Gorilla Rocket Motors was granted three new motor certifications for his 75-6000 motor hardware.

Gorilla
M1665WC-PS (White Cloud)
11% M
-------------------------
Total NS: 5705.01125
Max N: 2298.792125
Burn Time: 3.423955
AverageN: 1666.246875
Weight: 5579g (12.5#)

Gorilla
M1355RT-PS (Red Twister)
1% M
-------------------------
Total NS: 5164.64775
Max N: 1980.98425
Burn Time: 3.815625
AverageN: 1353.558725
Weight: 5216g (11.5#)

Gorilla
L1065BL-PS (Black Lightning)
64% L
-------------------------
Total NS: 4209.658
Max N: 1931.923
Burn Time: 3.951045
AverageN: 1065.477
Weight: (11.75#)

Reader comments:

#1 Re: Article: TMT announces new motor testing certifications

Quote:

. . . failing to meet NFPA guidelines for propellant weight to be classified as a high power rocket motor, since the motors produced sparks and couldn't be classified as model rocket motors. It was the first time a rocket motor fell into an unknown "classification hole" in the NFPA guidelines.

By raising the motor's propellant weight above 62.5 grams, the motor was able to certified as a high power motor, but it now unfortunately requires a federal explosives permit for purchase, severely limiting the motor's marketability.

That's not the only hole.

Jerry

Just Jerry on 02-21-2009 09:12 PM

#2 Re: Article: TMT announces new motor testing certifications

AMW Pro-X
G69SK-14A
AMW Pro-X 1G/Pro38-1G
-------------------------
46% G
Total NS: 117.149009 NS
Max N: 91.963344
Burn Time: 1.844582
AverageN: 63.607944
Weight: 198 g


117 NS il 73% of a G not 46%

20333 on 02-23-2009 08:16 AM

#3 Re: Article: TMT announces new motor testing certifications

Quote:

117 NS is 73% of a G not 46%

The measure is taken as the %'age of the distance between a full F, 80Ns, and a full G, 160Ns. 46% of the way between 80 and 160 is 117. IOW, 146% of 80.

I don't care for describing motors this way because of the potential confusion, but that's how it works.

Doug

.

plano_doug on 02-23-2009 08:38 AM

#4 Re: Article: TMT announces new motor testing certifications

Oh! ok That's good to know

Sorry

Dominic

20333 on 02-23-2009 09:00 AM

#5 Re: Article: TMT announces new motor testing certifications

Quote:

Note: All earlier G69SK motors previous sold are now "grandfathered" into this certification and shall be allowed to be flown under the high power rules recognized by NAR, TRA and CAR.

I saw a post on the CAR mailing list this weekend pointing to this, and stated that CAR (and ERD) were not constrained by the 62.5 gram propellant rule, so the motor is allowed in Canada, at CAR launches, to be used as a model rocket motor, since that was what CAR originally certified it as. The poster went on to point out that at TRA launches in Canada, the fliers would be constrained by TRA rules, and have to fly the motor as a high power motor.

ddmobley on 02-23-2009 12:31 PM

#6 Re: Article: TMT announces new motor testing certifications

Quote:

The measure is taken as the %'age of the distance between a full F, 80Ns, and a full G, 160Ns. 46% of the way between 80 and 160 is 117. IOW, 146% of 80.

I don't care for describing motors this way because of the potential confusion, but that's how it works.

Doug

.

I too have always thought that counter-intuitive at best, and misleading at worst.
I'd much prefer to have it actually proportional like most people would guess it is, with a 50% G = 100% F etc....
Maybe someone ought to start a petition...

ACME on 02-23-2009 02:28 PM

#7 Re: Article: TMT announces new motor testing certifications

Quote:

I too have always thought that counter-intuitive at best, and misleading at worst.
I'd much prefer to have it actually proportional like most people would guess it is, with a 50% G = 100% F etc....
Maybe someone ought to start a petition...

FWIW, some vendors have done it that way over the years. Can't cite the exact details, but one vendor sold a 3/4D motor, IIRC, which would be a 50% D in this scheme.

Basically, I see this nomenclature as a TMT tradition. TRA members have been using it for years. We'd be swimming upstream to try and change the culture Plus, Paul Holmes, TMT chair, has a full plate - asking him to do it differently is sorta piling on. So it is what it is. As long as they use Ns and not N/s in their reports, I'm happy

Seriously, I know Paul has been shuttling between Dallas and Austin many weekends doing the motor burns for all these certs. We should all give him a big shout out of thanks and kudos.

Doug

.

plano_doug on 02-23-2009 02:50 PM

#8 Re: Article: TMT announces new motor testing certifications

>> Some pretty cool motors just certified.

>> Thanks to all who volunteer their time and effort to advance the hobby.


The letter designation is good for a rough value of a motor's total impulse.

The Ns number is an exact value of its total impulse.

Both are pretty straightforward, as long as a person is as obsessed with rockets as most of us are.

IMHO the "% of a letter" adds nothing but a more confusing way to characterize total impulse.

delta22 on 02-23-2009 09:53 PM

#9 Re: Article: TMT announces new motor testing certifications

1% M is more meaningful to me than 51% M for what it's worth. I read these as "% over minimum".

So perhaps the measurement should stay the same and the way we think about it should change and the way we write it should change:

M (+1%)
M (+50%)
M (+99%)

Thus a Estes D12 would be D (+68%) and an Estes E9 would be an E (+40%) and an E15 would be an E (+98%)

Something that I still don't understand is how Tripoli lists the E10 as a 90% E when they state it has 41.3 ns total thrust: http://www.tripoli.org/tmt/EFGmotors.shtml

UncleVanya on 02-25-2009 10:24 AM

#10 Re: Article: TMT announces new motor testing certifications

Quote:

1% M is more meaningful to me than 51% M for what it's worth. I read these as "% over minimum".

So perhaps the measurement should stay the same and the way we think about it should change and the way we write it should change:

M (+1%)
M (+50%)
M (+99%)

If you're playing with M motors shouldn't you really be looking at the actual numbers? And the thrust curve?

billspad on 02-25-2009 12:24 PM

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