Rocket Motor Test Stand (RMTS)
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Rocket Motor Testing

ROCKET MOTOR TEST STAND (RMTS) 

RMTS DEVELOPMENT
The development of the Rocket Motor Test Stand (RMTS) was undertaken to better define the thrust-time characteristics of rocket motors for improved flight performance analysis. An AeroTech RMS-38/360 rocket motor using an I161-6w reload kit was hot fire tested using the RMTS on March 28, 1998. This system is capable of recording the thrust-time characteristics of rocket motors generating up to 331 pounds of maximum thrust. Overall test-bed dimensions for the RMTS are 19 5/8" long x 12" wide x 16 1/2" high. The RMTS is fabricated from 6061-T6 aluminum using 3/4" thick plate for the rocket motor mounting components of the main chassis. The rocket motor translation plate is supported by two pairs of linear bushings which slide on two precision steel shafts. Shaft alignment is maintained by two 2" square shaft support members bolted to a 1/4" thick x 19 5/8" long x 12" wide plate. The 1/4" plate is bolted to two 3 1/2" x 3 1/2" x 25 1/2" wood beams mounted on two concrete blocks. Rocket motor thrust is measured by a Celtron single-point load cell with a rated safe overload of 331 pounds. A 12 volt, 4 AH lead-acid battery is used to excite the strain gage circuitry in the load cell. The Celtron load cell has a full scale output of 2.0 mV/V. Finally, a DATAQ Instruments data acquisition module is used to record the thrust-time waveform to a laptop computer located 100 feet from the RMTS. The DATAQ DI-158-UP data acquisition module is a 12 bit, 4 channel A/D converter and was selected because it was inexpensive ($199) and connects to the USB port all standard Windows XP computers. In addition, if required this 4 channel device can be used to measure any four combinations of thrust, temperature and pressure.


ROCKET MOTOR HOT FIRE TEST

RMTS OPERATION AND DATA RECORDING
A 26 item countdown check list was used to safely and efficiently operate the RMTS in the field in accordance with the Tripoli Safety Code. An AeroTech Copperhead igniter was used to start the rocket motor using standard high power rocket electrical ignition equipment. WINDAQ waveform recording software was used to process the data stream being sent from the load cell mounted on the RMTS. From within WINDAQ the Gain was set to 100 and the sample rate was set to 240 samples per second. Prior to motor start the environmental temperature was recorded as 56 degrees Fahrenheit. Then, after giving an audible 5 second countdown the rocket motor operated normally and the thrust waveform data was successfully recorded by the WINDAQ software onto the laptop computer's hard drive. This concluded the first use of the RMTS on a warm spring day.


RMS-38/360 (I161) THRUST-TIME PLOT

DATA REDUCTION AND PLOTTING
The data reduction of the successful test of the Rocket Motor Test Stand (RMTS) was accomplished using the DATAQ Instruments WINDAQ Playback software. A range of waveform data was selected and copied to a file in spreadsheet format. Then, the Microsoft Works Spreadsheet computer program was used to plot the thrust-time data. The resulting plot indicates that the maximum thrust is about 50 pounds and the burn-time is approximately 2.4 seconds. Finally, a graphical analysis of the RMTS thrust-time data indicates that the Total Impulse (I) of the RMS-38/360 (I161) motor is 78 lbf-sec.

Rocket Motor Thrust-Time Response by In-Flight Measurement
A rocket flight using an IA-X96 Cambridge accelerometer was performed to produce in-flight data to verify the thrust-time response recorded by the RMTS. The Cambridge accelerometer was flown aboard a modified single stage Quantum Leap rocket. The Cambridge IA-X96 recorded the Quantum Leap's time dependant values of acceleration, altitude, and velocity. The maximum values of acceleration, altitude and velocity recorded by the accelerometer were respectively: 10.22 G's, 2,355 ft. and 291.18 mph (427 ft/sec). The Quantum Leap weighed 4.5 pounds at liftoff and used an RMS-38/360 (I161-10 w) rocket motor for propulsion.


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