Igniter Details

One of the most critical aspects of launching the Black Brant is going to be ensuring all motors light and come up to pressure as quickly as possible. The following pictures diagram the igniter to be used with each of the 54,000 Newton-Second "P" motors. Prior to finalizing this design a number of test will be run using a test stand and a specially constructed "boiler plate" motor to determine the actual amount of heat and pressurization each igniter will develop.

	Starting with a 38mm Blue Thunder grain, the casting tube is stripped off and the core is enlarged to 0.50 inches. The length of each grain will also be cut to 1.5 inches which is less that the diameter of the nozzle throat. Since three 38mm Blue Thunder grains will be needed one for each motor, the grains will be taken from an Aerotech I357.

	Six holes 0.250" holes will be drilled through the length of the grain. Once drilled, 1/8" slots will be cut from the outer edge of the grain to the holes. Daveyfires will be placed in the holes and the slots will give a path for the advancing flame front to exit towards the core of the "P" motors.

	Three "Pyrodex" pellets will be used for each of the igniters. These pellets will be 50 grain and 50 caliber. These pellets will be used to ensure rapid pressurization of the motor core.

	The "Pyrodex" pellets will be inserted into the center of each blue thunder grain.

	Six Daveyfire 28F electric matches will be used for each igniter. Each one of the Daveyfires will be folded and dipped before being inserted into the blue thunder grains. The use of six matches will ensure a virtual failure proof ignition source and an extremely high heat source.

Igniter testing will be conducted using a specially constructed boiler plate motor. This motor will be equipped with a pressure transducer and connected to a data acquisition system to accurately measure the resulting pressure rise. Initial tests will be conducted with "Pyrodex" pellets in the core. An additional set of runs with the "Pyrodex" pellets replaced with a high energy Magnesium/Teflon pyrogen.

Igniter Testing Setup

Test Motor

	An Animal Motor Works 75/76000 case was used as the test motor.
	The forward closure was drilled to accept a 1/4" NPT pipe thread and the brass fittings were screwed in.
	A nozzle from a 75/3500 AMW nozzle was drilled to 1.6" same as would be used in the "P" motor.
	This setup yielded a motor and nozzle combination that matched the free volume of the "P" motor core.

Cutting

	Using the front edge of the miter box as a guide all tubes were cut.
	90 degrees at a time were cut, then the box & tube were rotated to make the next 90 degree cut.
	Before each cut the alignment was checked.

38mm Blue Thunder Grain

	As described above a single 38mm Blue thunder grain was drilled and cut.
	Three 50 caliber pyrodex pellets were inserted into the core, and 6 folded and dipped Daveyfire 28F igniters were inserted into the holes.

Testing Results

First Day

Test #1 38mm Blue Thunder

	The first test was the 38mm grain. An Animal Motor Works 75/76000 case was used as the test motor.
	This test resulted in zero thrust and zero pressure build up within the core.

Test #2 25 grams thermite

	72 pounds of thrust was developed for about 25 milliseconds.
	Estimated pressure was 28 PSI
	The ringing was due to test stand oscillation.
	This test represents about 1/2 the thermite Darren recommended, and the same amount used in the Liberty Project

Test #3 32 grams thermite

	150 pounds of thrust was developed for about 75 milliseconds.
	Pressure reading was 60 PSI

Live Motor Test

	Jeff Anesetti's Nike-Ajax was used in the all up motor testing of the thermite.
	3.0 grams for thermite and two Daveyfire 28F (not dipped) igniters were used for each motor. Additional motor prep included sanding with 60 grit paper all grain surfaces.
	Jeff's rocket used five K1275 REDLINE motors with the newly redesigned single throat nozzle. These nozzles easily allowed the thermite package to be insert 2/3 of the way into the motor.
	Show to the right are two consecutive frames of a digital video camera. At 30 frames per second this represents an elapsed time of 33 milliseconds.

Second Day

Test #4 50 grams thermite

	275 pounds of thrust was developed for about 75 milliseconds.
	Pressure reading was 150 PSI
	Overall a very sharp rise and fall in pressure

Test #5 100 grams thermite

	275 pounds of thrust was developed for about 100 milliseconds.
	Pressure reading was 130 PSI
	Overall a very sharp rise with a sustained value and then dropping off quickly.
	Large amount of slag was left in the motor.

Test #6 J-350 Motor

	Aerotech sponsor the last test. A thrust measurement of a standard J-350 motor.
	The test used 1.5 grams of thermite which is twice the calculated amount.
	The thrust curve shows the motor coming up to pressure in 25 milliseconds with no over-pressurization.

Other Tests

	Neil McGilvray lit his O motor with an internal core structure similar to the Black Brant "P" motor.
	Neil used 25 grams of thermite to light this motor.
	Watch the video carefully, there seems to be no startup time, the motor goes from off to full pressure instantly.

Omotor.wmv

Credits

The Black Brant team would like to thank the following people:

	Bill Seiders for the use of his test stand.
	Gates Brothers Rocketry for the use of their AMW 75/7600 motor case.
	Aerotech rocketry for their donation of a J-350 motor.
	Jeff Anesetti for allowing this to be done on a live rocket.
	Bill Seiders, Buck Gomez, Jimmy Oldham, and Rick Dickinson for their help in performing these tests.

For problems or questions regarding this web contact WebMaster@BlackBrant2.com

This page looks best when viewed on my computer and was last updated on 06/06/07

THE BLACK BRANT PROJECT on the verge of insanity