Data Recorders: JABS Bomb Drop

Transcription

1 Data Recorders: JABS Bomb Drop Casey Birmingham NAWCWD China Lake, CA Funded by ONR Approved for Public Release; Distribution is Unlimited

2 Purpose of JDAM JABS Joint Direct Attack Munitions (JDAM) Assault Breaching System (JABS) To clear mines and obstacles to support amphibious assault Two Environments: Surf and Beach Zones System was effective in Beach Zones, and at up to 3 meters of water Extended to include VSW Zone (Very Shallow Water) Water depth of 10 to 40 feet Investigation into what combination of warhead and fuzes was most effective

3 What and How What is needed for High Effectiveness in VSW The acceleration levels seen by the bomb on impact into water and sand How to find these acceleration levels Install data recorders that will survive impact and monitor all crucial components Accelerometers Impact Switches

4 Brief History: The Beginning 1997 Single channel 16 bit x 32k memory Data Recorder Memory stored on SRAM, as power is lost, the data is transferred to EEPROM

5 channel 16 bit x 32k memory Same FPGA Package Memory stored in FRAM memory chips 45 year storage life Two wire trigger Write Mode/Read Mode Save pre-trigger data, write remaining data Design Includes Shock Hardened Capacitors so recorder has power throughout impact regardless of power supply

6 Objective of JABS Drop Tests 1. Record the accelerations acting on fuzes inside fuzewell of a 2000 lb. JDAM during impact 2. Record Impact Switch Closures during impact, compare to accelerations

7 JABS Flight Drop test: Requirements Data Recorder Redundancy Two Recorders per Bomb Two Accelerometers per Recorder Recorder Features Non-Volatile Memory 100 milliseconds of Pre-trigger Data 200 milliseconds of Post-trigger Data Shock Hardened Recorder Pre-flight Confidence Testing Temperature cycling Flight vibration Shock Simulated FZU-48 power enable * Funded by ONR

8 Drop Environments First flight drop into simulated Beach Zone Second flight drop into simulated Surf Zone 10 feet of water, then sand

9 Placement of Recorders Aft Fuze Well FZU-48 Forward Fuze Well

10 JABS DATA RECORDER BZ Block Diagram Battery Pack Voltage Converter Shock-Hardened Capacitors FZU Power Turbine Release Filter Filter and Pulse limiter Mode & Trigger 1 Start Record Power Regulation 200 msec Delay Stop Record Trigger 2 External Recorder I 3 I 4 FZU Data Channel 1 Data Channel 2 Data Channel 3 FORE and AFT IMPACT SWITCHES I 1 Piezoelectric Accelerometer Piezoresistive Accelerometer I 2

11 Results from Beach Zone Mixed Bag Some positive indicators, some recorder anomalies Reasonable acceleration Characterization

12 Results from Beach Zone The negative results included: Unusable Impact Switch closure data Broken wire causing an accelerometer malfunction Power loss or reset on one recorder Non-trigger on one recorder Accelerometer Malfunctioning Power Loss or Reset to the recorder

13 Changes to recorder from Beach Zone to Surf Zone Unusable Impact Switch Data: Changed from a resistor divider, to 1 bit digital signal, monitored each line individually. Recorder No-Trigger: Mass from solder and thick wire gauge resulted in a broken connector Fixed by reducing wire gauge and using less solder. Changed testing procedure to test the connector. Broken Accelerometer Wire: Fixed by increasing the diameter of thru-hole mount on PCB board. Glued strain relief to mounting structure. Power Loss or Reset: Could not recreate in lab, redrew printed circuit board layouts to make sure no existing electrical lead problem would occur again. Team concluded that it was a unique event that would most likely not happen again.

14 Battery Pack JABS DATA RECORDER BZ Block Diagram Voltage Converter Shock-Hardened Capacitors FZU Power Turbine Release FZU Filter Filter and Pulse limiter 1-Bit Digital Mode & Trigger 1 Start Record Data Channel 1 Power Regulation Data Channel msec Delay Stop Record Data Channel 3 Trigger 2 External Recorder FORE and AFT IMPACT SWITCHES I 3 I 4 I 2 I 1 Piezoelectric Accelerometer 2255 Piezoresistive Accelerometer 7270 Piezoelectric Accelerometer 3901

15 Results from Surf Zone Accurate Acceleration Data All accelerometer records stored similar data and recorded like events

16 Results from Surf Zone Some anomalies did occur: Protection diodes for Impact Switch record lines shorted. Voltage on trigger line was recorded instead of switch closure. Common trigger line between Nose and Tail recorders on Bomb 1 failed. Recorders triggered independently of each other. Both recorders on Bomb 2 reset around 15 ms after trigger. Impact event was captured, however this reset event was obviously no longer considered unique.

17 Final Conclusions of Flight Test First Objective: Record Acceleration Levels Acceleration records were accurate Good for Modeling and Simulation Second Objective: Record Impact Switch Closure Difficulty interpreting results from BZ drop Protection diode failure on SZ drop