Woo Hoo !
I lightly scuffed the cores and ends of the three grains in an Aerotech RMS 38/360 I357T-Long ( Batch AUG 20 1996 ) last week and flew it at an AARG Launch in Hutto, TX on Sunday, Feb 18 2024.
I was more than a little apprehensive about the age and condition of the propellant but it sure looked OK.
The delay grain was a tad swollen but I trimmed the ends flush with the delay insulator and it fit fine in the forward closure and I was flying dual deployment so I wasn't worried about the burn rate of the delay.
The early morning temperature was cold but it was a crystal clear morning and while the morning was windy, the afternoon was perfect !
Open Rocket sim'd Spock's Johnson to 4109 ft and 686 ft/sec with 118 ft/sec off an 8-foot rail after I adjusted the Launch Conditions to match the actual contitions at Hutto when I launched the rocket:
Temperature: 52 F
Pressure ..: 1001 mB
Wind Speed : 5 mph NNW ( estimated -- need to replace my anemometer )
Rail Length: 8 ft
Diameter ..: 2.26 in
Length ....: 54.4 in
Motor Mass : 356 g
Final Mass : 182 g
Launch Mass: 1643 g
The actual Altitude reported by the Blue Raven was 4011 ft and 680 ft/sec !
I think I got all my Impulse from that old Motor !
This is the best photo I could get from a video capture -- the rocket was scootin'
No smoke and that's what I like to NOT see with Blue Thunder Propellant !
A little data ... Since this is the Propulsion Sub-Forum, let's start with the raw, unprocessed Drag and Thrust Curve data.
This is the Acceleration -vs- Velocity 'bun' along with air density thru the thrust and coast phase:
This Data along with the Rocket Mass thru the flight from liftoff to apogee can be used to extract Drag Force -vs- Velocity and then the Thrust Force can be adjusted for Drag Force -vs- Velocity and finally Thrust -vs- Time can be calculated from the raw acceleration data.
I've not completed those calculations yet, but the 28-year old I357T I flew Sunday is definitely 'in the ball park'.
Burn Time was estimated by inspecting the raw acceleration data and now that I've plotted the results, it may be a few msec short.
Burn Time accuracy can be improved on subsonic flights by fitting a curve to the coast phase Drag -vs- Velocity data and then finding the point where the Drag Force diverges from the fitted curve.
This is the raw axial acceleration and velocity and altitude reintegrated via the trapezoid rule after adjusting liftoff time by -0.092 sec from the Blue Raven Flight_Time=0:
These are the three altitude -vs- time plots from the Blue Raven Data:
PAlt is the raw altitude data reported by the Blue Raven. DAlt is the density altitude corrected for the site temperature and the temperature standard lapse rate. IAlt is the inertial altitude twice integrated from acceleration via the Trapezoid Rule. Note that IAlt is meaningless after apogee. Also note that my Hobby Lobby 'Simply Tacky' goo leaked a bit when the MAIN was deployed at 500 ft.
Inspecting raw gyro -vs- time data for the first few milliseconds show that the rocket left the 8-foot rail at 0.141 sec after liftoff and the rocket was moving about 113 ft/sec at 7 feet above ground level. Pretty close for an 8-foot rail since the upper rail guide is 12.5 inches above the tail:
This data also matches the Open Rocket sim very well ( 118 ft sec for an 8-foot rail ).
Next are raw gyro data and tilt and roll from liftoff to apogee:
These results look pretty good for a fairly calm day. Interestingly Spock's Johnson also exhibited a 'Roll Reversal" on an I225FJ on a Dec 30 2023 flight with 10 mph SE winds.
Dual Deployment worked without issue with 4F BP charges of 1.4 g ( APO) and 1.2 g ( MAIN )
TLAR ( thanks for the great FLA @Rschub )
Finally, I flew @Brainstormz123's Comspec Transmitter for a second time and it worked fine but the rocket landed only 970 feet from the pad, just about exactly where @JimJarvis50 predicted the day before the launch!
Woo Hoo !
So I feel good about all the old Blue Thunder in my magazine !
For the time being, I'll be buying new White Lightning from Harry the Motorman but I'll try an old Black Jack Motor next.
Thanks for all the advice on how to prep the propellant in my old motors all'Y'all !
-- kjh
I lightly scuffed the cores and ends of the three grains in an Aerotech RMS 38/360 I357T-Long ( Batch AUG 20 1996 ) last week and flew it at an AARG Launch in Hutto, TX on Sunday, Feb 18 2024.
I was more than a little apprehensive about the age and condition of the propellant but it sure looked OK.
The delay grain was a tad swollen but I trimmed the ends flush with the delay insulator and it fit fine in the forward closure and I was flying dual deployment so I wasn't worried about the burn rate of the delay.
The early morning temperature was cold but it was a crystal clear morning and while the morning was windy, the afternoon was perfect !
Open Rocket sim'd Spock's Johnson to 4109 ft and 686 ft/sec with 118 ft/sec off an 8-foot rail after I adjusted the Launch Conditions to match the actual contitions at Hutto when I launched the rocket:
Temperature: 52 F
Pressure ..: 1001 mB
Wind Speed : 5 mph NNW ( estimated -- need to replace my anemometer )
Rail Length: 8 ft
Diameter ..: 2.26 in
Length ....: 54.4 in
Motor Mass : 356 g
Final Mass : 182 g
Launch Mass: 1643 g
The actual Altitude reported by the Blue Raven was 4011 ft and 680 ft/sec !
I think I got all my Impulse from that old Motor !
This is the best photo I could get from a video capture -- the rocket was scootin'
No smoke and that's what I like to NOT see with Blue Thunder Propellant !
A little data ... Since this is the Propulsion Sub-Forum, let's start with the raw, unprocessed Drag and Thrust Curve data.
This is the Acceleration -vs- Velocity 'bun' along with air density thru the thrust and coast phase:
This Data along with the Rocket Mass thru the flight from liftoff to apogee can be used to extract Drag Force -vs- Velocity and then the Thrust Force can be adjusted for Drag Force -vs- Velocity and finally Thrust -vs- Time can be calculated from the raw acceleration data.
I've not completed those calculations yet, but the 28-year old I357T I flew Sunday is definitely 'in the ball park'.
Burn Time was estimated by inspecting the raw acceleration data and now that I've plotted the results, it may be a few msec short.
Burn Time accuracy can be improved on subsonic flights by fitting a curve to the coast phase Drag -vs- Velocity data and then finding the point where the Drag Force diverges from the fitted curve.
This is the raw axial acceleration and velocity and altitude reintegrated via the trapezoid rule after adjusting liftoff time by -0.092 sec from the Blue Raven Flight_Time=0:
These are the three altitude -vs- time plots from the Blue Raven Data:
PAlt is the raw altitude data reported by the Blue Raven. DAlt is the density altitude corrected for the site temperature and the temperature standard lapse rate. IAlt is the inertial altitude twice integrated from acceleration via the Trapezoid Rule. Note that IAlt is meaningless after apogee. Also note that my Hobby Lobby 'Simply Tacky' goo leaked a bit when the MAIN was deployed at 500 ft.
Inspecting raw gyro -vs- time data for the first few milliseconds show that the rocket left the 8-foot rail at 0.141 sec after liftoff and the rocket was moving about 113 ft/sec at 7 feet above ground level. Pretty close for an 8-foot rail since the upper rail guide is 12.5 inches above the tail:
This data also matches the Open Rocket sim very well ( 118 ft sec for an 8-foot rail ).
Next are raw gyro data and tilt and roll from liftoff to apogee:
These results look pretty good for a fairly calm day. Interestingly Spock's Johnson also exhibited a 'Roll Reversal" on an I225FJ on a Dec 30 2023 flight with 10 mph SE winds.
Dual Deployment worked without issue with 4F BP charges of 1.4 g ( APO) and 1.2 g ( MAIN )
TLAR ( thanks for the great FLA @Rschub )
Finally, I flew @Brainstormz123's Comspec Transmitter for a second time and it worked fine but the rocket landed only 970 feet from the pad, just about exactly where @JimJarvis50 predicted the day before the launch!
Woo Hoo !
So I feel good about all the old Blue Thunder in my magazine !
For the time being, I'll be buying new White Lightning from Harry the Motorman but I'll try an old Black Jack Motor next.
Thanks for all the advice on how to prep the propellant in my old motors all'Y'all !
-- kjh
