Specification • The JAS mechanical structure shall consider tooling to hold it while installing and transporting components. Features for mounting the hardware that supports the system shall be included. A static 4 G load shall be used with positive margins per this document. Mechanical Aerospace Ground Equipment (MAGE)
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Margins of Safety
Specification • Margin of Safety (MS) is defined as MS = 1/R - 1, where R is the ratio of the factored applied load (or stress) to the allowable load (or stress) and shall be greater than 0. Margin of Safety Calculation The specific failure theory used to determine the allowable load...
Mass Properties
Specification • The JAS mechanical structure shall attempt to optimize mass, center of gravity, and moments of inertia.
Material Properties and Allowables
Specification • The JAS mechanical structure design of the metallic parts shall use A Basis allowables from MIL-HDBK-5 or equivalent. The design of the composite parts shall use B Basis allowables generated using the methodology in MIL-HDBK-17 or equivalent.
Materials
Specification • The JAS mechanical structure shall be constructed of materials capable of performing at the specified orbit for a minimum of ten years after being stored in an inert gas environment and after exposure to clean air during testing, launch, and ascension. The use of the following materials is prohibited: Zinc,...
Mechanical Interface Design
Specification • The JAS mechanical structure as described in this Mechanical specification will support applications intended for a space environment and will provide stable mechanical structure for the electronics during launch and while operating in a high vacuum.
Mechanical Specification
Specification • The Mechanical Specification provides details about mechanical interface design, environmental impacts, and design constraints that should be considered for implementing mechanical structures in a JAS-based system. The figure below provides context of where the Mechanical Specification resides in the JAS standard. JAS Standard Hierarchy
Molecular Contamination
Specification • For all components that will be in the vicinity of an optical payload and anywhere that contamination at the molecular level is an issue, all parts and materials must comply with ASTM E 595 for less than 1% Total Mass Loss (TML) and 0.1% CVCM. Thermal bake-out of all components...
Molecular Thermovac Testing
Specification • Thermovac temperature testing is required to determine dissipation at full power modes. A test plan needs to be developed and coordinated with the System Engineer.
Mounting Distortion Impact
Specification • The JAS mechanical structure shall maintain the electronics/PCBs listed below within given positions with distortions less than expected for the intended application.
Obscuration
Specification • All JAS mechanical structure components shall be placed to prevent obscuration of the system view of space if the JAS electronics box will be used to radiate. Structural elements shall be kept an appropriate distance away from the JAS electronics housings.
Packaging for Thermal Dissipation
Specification • The preliminary JAS mounting details are defined by the baseplate details in ICD drawing xxxxxx. The JAS electronics box is meant to mount through the blue baseplate shown in the figure below. The figure shows a nominal 3x3 stack in an exploded view. JAS Mounting Exploded View Conducted Self-radiated panels...
Particulate Contamination
Specification • Internal Cavities will be wiped clean with isopropyl alcohol and allowed to air dry for 30 minutes prior to close out; the structure will be covered during the drying process. The surfaces will be visibly clean. Visibly clean is defined as no contamination visible when viewed from 6-18 inches away...
Potential Flight Capability
Specification • Each component of the JAS mechanical structure should consider Flight capability as this will force consideration of design, flight, and test environments described in this specification. The JAS mechanical structure should be designed for the specific application intended.
Screened Venting
Specification • Where venting requires a screen to maintain cleanliness requirements, based on a 5µ Pall Rigidmesh screen, there shall be 1.5 in^2 or greater screen area per ft^3 of volume where the volume is the sum of multiple daisy-chained volumes. The daisy chained volumes shall be vented.
Shielding
Specification • The JAS mechanical structure shall provide EMI shielding which meets 60db shielding effectiveness from 0.1 to 1 GHz for the FPA Sensor box with covers in place.
Strength Qualification
Specification • The JAS mechanical structure design shall possess sufficient strength and rigidity to withstand environmental conditions defined in this document. Load Conditions
Structural Integrity
Specification • The JAS mechanical structure design shall possess sufficient strength and rigidity to withstand environmental conditions defined in this document.
Thermal Impact
Specification • The JAS mechanical structure shall be designed to maintain the electronics/PCBs within given displacements while the system is in operation as applied by determining thermal impacts on the mechanical structure. The operational thermal environments of a nominal orbit need to be applied to the mechanical model as necessary to ensure...
Thermal Loads
Specification • Yield and ultimate thermal loads for hardware subject to thermal tests shall be calculated by either Alternate A or Alternate B, as defined below, whichever produces the maximum load. These thermal loads are not to be used for fatigue. Alternate A: Yield thermal load (YTL) = Predicted thermal load (PTL)...
Unscreened Venting
Specification • All closed volumes in JAS mechanical structure shall have a minimum venting area requirement of 0.25 in^2 or greater venting area per ft^3 of volume.
Vacuum Impact
Specification • The JAS electronics shall consider testing in a thermal vacuum environment because inadequately heat-sunk parts will fail/burn-up. Overheating is the issue, exceeding maximum junction temperatures.
Venting
Specification • The JAS mechanical structure shall have no confined or captured volumes. Venting ports shall be provided to prevent damage, or the release of gases, due to pressure changes during testing, transportation, and launch. Threads need not be vented.
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