Level 1 Certification Attempt with RockeTV38 Booster…

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RockeTV38 Booster Construction

Motor Mount and Retainer

  Three #8 x 32 tpi machine screws, nuts, and wing nuts

  One Steel Washer from ACE Hardware, 2-1/4” OD, 1-3/8” ID

  One 38mm ID Motor Mount Tube, 16” long

  Two 38mm to 2.6” Centering Rings

 

  

 

Baffle Ejection Gas Cooling System

  One BT80 2.6” Tube, 5” long, Cut Lengthwise, then glued to make a perfect fit coupler for the LOC style airframe tube

  Coarse Steel Wool

  Two coupler bulk plates drilled with gas escape holes

  One screw eye for attaching 100# Dacron braided line shock cord

 

 

 

Fins and Fin Mount Parts

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RockeTV38 Flights

Level One Certification Flight on 10/12/2002 Details:

Initially I was planning on launching with a Pro38 H110-10 2 grain reloadable motor. However, my motor was not available and the difficult decision to use an I205-11 was made after about 15 minutes of discussion and inspection for CG shift, etc. The failure on the second flight probably would not have occurred if only H110 motors were used or if a Cyanoacrylate reinforced Estes BT-80 tube had not been used for the 9.125” payload section. The remainder of the rocket airframe was made with LOC style 2.6” tubing which is considerably stronger.

 

Good launch on Pro38 I205-11, ~4200 feet AGL altitude, good deployment under 36” nylon parachute. Drift downwind and soft landing approximately ¾ to 1 mile from launch pad. Rocket recovered and inspected. Level One certification achieved!

 

Second Flight on 10/13/2002 Details:

Altitude and speed estimates are calculated from WRASP.EXE. Thrust estimates are from ThrustCurve.org data. Time from ignition measurements are from a frame by frame analysis of onboard video transmitted to ground station and recorded on VHS VCR. Post mortem analysis of airframe and internal components performed to determine cause of flight failure.

Details

1.      Good ignition, initial acceleration, little to no spin 766.7 ms after ignition a substantial spin rate occurs, ~216 mph @ ~114 feet
AGL, near max thrust of 50 lbs,  payload section tubing near balsa bulkhead block compromised, causes slight payload section misalignment.

2.      1.900 sec after ignition, disintegration of payload, ~510 mph @ ~736 feet, near burn out time, thrust ~ 0.0 lbs, payload section misalignment with high velocity and increased drag results in instability (center of pressure is moved forward dramatically).

3.      Booster sustains no damage upon impact with ground. No damage to booster during flight. Damage to Parachute compartment is limited to zippering from the shock cord at premature recovery system deployment.

4.      Payload section sustains minor lengthwise tubing crease upon horizontal impact with ground.

5.      Electronics sustain no further damage upon impact with ground. Photocell triggered piezo siren is still sounding when electronics are found.

6.      Parachute slowly tumbles to ground and sustains no damage.

 

Conclusion

Instability causes increased spin and more force on compromised part of payload tube, payload tube splits from around balsa bulkhead block, bulkhead block pulled out from payload compartment which rips electronics out, block also pulled out of parachute compartment resulting in parachute early deployment. Early deployment overloads shock cord made from 33 feet of 100 lb braided dacron and 1" nylon elastic shock absorbers. Parachute with majority of shock cord tumbles to ground, electronics (transmitter, photocell, battery packs, siren, LED, and part of switch tumble to ground with bulkhead block. Empty payload compartment with camera and nosecone with about 3 feet of shock cord attached flutter to ground, booster with length of shock cord attached to ejection baffle tumbles to ground and lands butt first.