Superstition Spacemodeling Society

National Association of Rocketry

Level 2 ( J / K / L ) Pre-Certification Test

Study Guide

LAUNCH SITE DIMENSION AND MINIMUM SAFE DISTANCE TABLE
Total Impulse All Motors (Newton-Seconds)	Equiv Motor Type	Min. Safe Distance 1-motor	Min. Safe Distance multiple motors	Around Launcher Clear Distances	Minimum Site Dimensions (feet)	Equivalent Site Dimension
160.01 - 320	H	100	200	50	1,500	Quarter Mile
320.01 - 640	I	100	200	50	2,500	Half mile
640.01 - 1,280	J	100	200	50	5,280	One mile
1,280.01 - 2,560	K	200	300	75	5,280	One mile
2,560.01 - 5,120	L	300	500	100	10,560	Two miles
5,120.01 - 10,240	M	500	1,000	125	15,840	Three miles
10,240.01 - 20,480	N	1,000	1,500	125	21,120	Four miles
20,480.01 - 40,960	O	1,500	2,000	125	26,400	Five miles

Please be aware that when figuring the minimum safe distance for a multiple motor configuration that the total N-sec impulse for all motors is used with the minimum safe distance multiple motors column.
Don't just use the Equivalent Motor Type. The Equivalent Motor letter is only a reference in this case.

As an example:

Incorrect:
A cluster with two J570's using the Equivalent Motor Type column, move right to the multi motors column and the answer is 200ft minimum safe distance. Sorry, this is the wrong answer...see below

Correct:
A cluster with two J570's would need to be launched from the 300ft distance. This is figured by multiplying the impulse times the number of motors (1060N-sec x 2 = 2120N-sec). Using the 2120N-sec number, find which row in the Total Impulse All Motors column the number fits, (in this example it is within the "K" classification) and move to the right and find the number within the minimum safe distance multiple motors column (our number is 300). This is the correct number to use for this configuration for the minimum safe distance to launch.

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