ROL NEWS: AeroTech L1120W-P Motor Recertified as M1297W-P

[jetra2]

(ROL Newswire) -- AeroTech, Inc. pleased to announce that the White Lightning reload kit originally designed for the RMS-75/5120 casing, that is being manufactured at the AeroTech Cedar City, UT plant has been recertified as an M1297W-P.

The 4-grain motor in the AeroTech 75mm RMS line (formerly the L1120W-P) was tested on February 27, 2004 by the Tripoli Motor Testing (TMT) Committee and has been renamed and recertified to the M1297W-P designation as a 5% M motor, and is certified until June 30, 2009.

The TMT test data for the M1297W-P motor is as follows:

Total Impulse: 5,416.6 N-sec (1,217.8 lb-sec)
Burn Time: 4.17 sec.
Average Thrust: 1,297 N (291.6 lb)
Maximum Thrust: 2,049 N (460.7 lb)
Loaded Weight: 4,637 grams (10.22 lb)
Propellant Weight: 2,722 grams (6.00 lb)
Specific Impulse: 199 sec.

Previously manufactured AeroTech L1120-P labeled motors will enter a three year burn period in line with current TMT certification policy.

The suggested retail price of the M1297W-P reload is $259.95, making it the lowest cost 'M' solid propellant reload kit on the market, and is perfect for Level 3 certification and general sport flying.

Source: AeroTech

This is exciting! CARL! Get one of these and throw it in the BLU!

Yahoo! It looks like some of cheapskates might actually be able to afford L3 now! Droool.....M1297....ahhhhgggggg!



Jason

 

[Ryan S.]

wow that is a cheap M.....small too but really cheap.

No one has an excuse not to cert now

 

[rocwizard]

Dangit This may be good for many others but this basically killed my project i am working on. I have been building my attempt at the L altitude record which was built specifically for the L1120W. It was supposed to fly at BALLS this year. I doubt that Cesaroni will have a full L released in the States by then. WHAT to do?!?! We won't be L3 till at least Nov. and even if we had it by Sept. I don't think this could take the M record, even on an M1315


Any ideas?

 

[UhClem]

The motor hasn't changed (so Gary claims) but we are expected to believe that this motor magically grew 10% more powerfull.


I wonder when and how the TMT test stand was last calibrated.

 

[Mark Clark]

Originally posted by UhClem
The motor hasn't changed (so Gary claims) but we are expected to believe that this motor magically grew 10% more powerfull.


I wonder when and how the TMT test stand was last calibrated.

Stand is calibrated before every test session. A calibration weight is placed on the cell, in this case it was about 75 lbs.
We questioned this data too and rechecked the calibration and it is good. The other motors fired at the same time were very close to historical or expected data.


Why is it the new data is always wrong and the old is perfect and written in stone?

Mark
TMT

 

[rocwizard]

Hey Mark, any chance you could test it again, and bump back to an L temporarily just before BALLS?

 

[Mark Clark]

Call around to dealers and those with caches of motors, see if there are any of the old ones out there. They are still certified as an L.

Mark

 

[rocwizard]

ahh, of course! I will start firing off the emails now.

 

[UhClem]

Re: calibration

I did not say that the old data was correct and the new data suspect. There has been a significant change in this motors performance. Why?

Placing a known 75 pound load on the stand does not a calibration make. At most it can verify a previously performed calibration. It is industry practice to perform NIST traceable calibration on load cells once a year. This measures the cell sensitivity, nonlinearity, and hysterisis. Is the TMT load cell(s) sent to a calibration lab each year?

 

[cls]

Mark Clark wrote:

Why is it the new data is always wrong and the old is perfect and written in stone?

conversely Mark, why is the old test wrong??

why was the motor retested?

what made you suspect the old test was wrong?

and what other old tests are now suspect!?!???


... just standard QA questions ...

 

[UhClem]

Originally posted by Mark Clark
Stand is calibrated before every test session. A calibration weight is placed
on the cell, in this case it was about 75 lbs.
We questioned this data too and rechecked the calibration and it is good. The
other motors fired at the same time were very close to historical or expected data.


Why is it the new data is always wrong and the old is perfect and written in stone?

Mark
TMT

No response to my question on when the load cell was last sent out for
calibration so I must assume that the answer is that it has never been calibrated.

The other claim here is that the other motors fired that day looked good. TMT
has finally posted that data to the TRA web site so lets take a look.

The motors tested along with the L1120 on 27 Feb 04 fall into three groups:

1) New certification: no historical data for comparison. (G20, G37, H275, J110, J148, K475)
2) recertification but thrust doesn't exceed 75 pounds. (H220, H238, I195)
3) Recertification and data does exceed 75 pounds. (I435)

Only one motor is in group 3 and it isn't of any use in verifying the L1120 data for two reasons:

1) Peak and average thrust far below the level of the L1120. Peak thrust of the I435 was 176 pounds.
2) Data for the I435 was clipped.

https://www.tripoli.org/tmt/new_motors/AT I435T jun 09.pdf

There is a very flat and constant thrust during the early part of the burn.
This amazingly constant thrust stands out in a thrust curve that is otherwise
never constant. Now the clipped data is less than a tenth of a second long and wouldn't have a huge impact on total impulse if it were the only problem. But there is no way to know that this is the only symptom of whatever caused this problem.

Once upon a time, TMT also made sample raw data files available in zip format. If that were still available, it would be possible to examine the raw data to determine if the post processing required to the produce the graph in the pdf document was at fault.



TMT also finally posted data from testing done last year. In this testing,
two other Aerotech 75mm motors (K560 and L850) were tested. These motors use the same propellant as the L1120 but fewer grains. (Two for the K560 and three for the L850)

How did they compare to previous testing?

Motor Prev. Impulse Current Impulse ISP
K560 2510 2417 179
L850 3736 3646 179
L1120 4946 181
M1297 5416 199


The K560 and L850 seem to have tested with slightly lower impulse than the
previous tests. This makes it quite odd that the L1120 has increased.

The M1315 (the other Aerotech 75mm white lightning reload) uses a different
propellant formulation as a result of an early round of CATO's. This propellant
burns slower but the TMT data for the M1315 shows an ISP of 195 so perhaps Aerotech switched to this propellant in the M1297. Except that you would expect the burn time of the M1297 to be longer. It is 4.17 seconds, the L1120 was 4.43 seconds, and the M1315 was 5.4 seconds.


At one point I thought it was a toss up as to which data set was in error. But
in light of the lack of calibration, defects in another data set from the same
session, and tests of other motors in the same family it is much more likely
that the data for the 27 Feb. 2004 L1120 test is in error.


At the very least TMT must send their load cell(s) out for calibration. These
results must then be compared to the last calibration data (all new load cells
are shipped with calibration data) to see if there has been any change. If there has, then all data collected between the two calibrations is suspect.

Relying on the application of single test weight of less than the expected
thrust level is not a sufficient calibration. The single weigh method has a few problems:

1) The test weight should have a NIST traceable measurement.
2) A two point calibration (the other point is zero) assumes that the load cell is linear. It probably is but if something bad has happened it might not be. If you don't test for linearity, you don't know. A minimum of three points are required to test for linearity.
3) Calibrating to 75 pounds and then using the load cell to over 400 pounds is called extrapolation. Is the load cell really linear at loads over 75 pounds? If you don't test it, you don't know.

 

[Jerry Irvine]

Originally posted by UhClem
No response to my question on when the load cell was last sent out for
calibration so I must assume that the answer is that it has never been calibrated.

2) Data for the I435 was clipped.

TMT also finally posted data from testing done last year. In this testing,
two other Aerotech 75mm motors (K560 and L850) were tested. These motors use the same propellant as the L1120 but fewer grains. (Two for the K560 and three for the L850)

How did they compare to previous testing?

Motor Prev. Impulse Current Impulse ISP
K560 2510 2417 179
L850 3736 3646 179
L1120 4946 181
M1297 5416 199


The K560 and L850 seem to have tested with slightly lower impulse than the
previous tests. This makes it quite odd that the L1120 has increased.

The M1315 (the other Aerotech 75mm white lightning reload) uses a different
propellant formulation as a result of an early round of CATO's.

At one point I thought it was a toss up as to which data set was in error. But
in light of the lack of calibration, defects in another data set from the same
session, and tests of other motors in the same family it is much more likely
that the data for the 27 Feb. 2004 L1120 test is in error.

1. There are two White Lightming propellants but not two EX numbers?

2. There is a provision where a manufacturer can declare a power or letter class within 2 standard deviations of the tested value. Was this the case here but simply not disclosed? Purpose: to make the motor more marketable as a "cheater M motor".

3. Data clipped? Certify it. Data inconsistent? Certify it. The ethicis made visible in this Schultz factual presentation are notable.

4. This is not the first time TMT has had irregularities

Jerry

 

[DPatell]

People make mistakes. They are not always out to get someone. Rocketry is not as political as it may seem to some people.

If there was a problem, it's fixed now, I'm sure they're trying.

I may be wrong in saying this, because I sure don't know everything that has happened in the past. But they are doing a good job to me. I have certed motors to fly.