Frangible_Sphere_Salient_Requirements.docx

Atlantic Test Ranges Aircraft Signature & Avionics Measurement Branch Patuxent River, MD Salient Requirements for Frangible Sphere

1. Sphere Materials:

a. Sphere shell material must be TC-852 Polyurethane Resin or HapCo Ultralloy 103 Resin. Material manufacturer preparation and curing processes shall be followed. A threaded fastener insert shall be placed in the mold for each sphere. The insert shall be an 8-32 tee-nut, McMaster-Carr item 90975A009 or equivalent. The sphere shall be painted with an epoxy primer coat of MIL-PRF-23377 Type 1 Class C2, and a final application of Spraylat 599-83755 paint with Spraylat 599-84045 thinner (4:1 mixture).

2. Sphere Geometry:

a. The sphere shell must be formed using the Naval Air Warfare Center Aircraft Division) NAWCAD Air Vehicle Modification and Instrumentation (AVMI) Directorate rotational cavity mold or equivalent. Drawing number for the mold is 42710M3001 (24 August 2010).

b. The sphere OD from mold shall be 11.995 inches.

c. The sphere ID will be approximately 11.78 inches.

d. The sphere primer coat of paint shall cover the entire external surface of the sphere, and the Spraylat paint coating shall be of a minimum thickness of 0.002".

3. Sphere Mass:

a . Total sphere mass must be no less than 2 lb. and no more than 2.4 lb.

4. Sphere Conductivity

a. Conductivity of less than or equal to 0.5 ohms/sq using a 4-point probe Guardian Surface Resistivity Meter SRM-232-10, or equivalent, measured randomly across entire sphere surface quadrants.

b. 10% of the Lot ordered will be measured at 48 points by the customer.

5. Sphere Shell and Surface Geometry Rejection Criteria:

a. Each sphere may not have more than 2 external surface defects observable under unmagnified visual inspection that exceed 0.025" depth or height (measured from the un-deformed sphere nominal surface).

b. External surface defects shall not have a depth or height (measured from the un-deformed sphere nominal external surface) greater than 0.03".

c. For external surface defects higher or deeper than 0.015", that defect's largest measurable edge-to-edge width shall be no greater than 0.15" (width measurement shall only include portions of that defect that are 0.01" or more-higher or deeper than the nominal sphere shell external surface).

d. Sphere shell shall have no observable foreign material embedded in it.

e. Sphere shell thickness shall not be less than 0.080" over any contiguous area larger than 0.062 in2.

f. Sphere thickness shall not be less than 0.04" at any location.