Specification • The JAS mechanical structure shall implement a coordinate system as a reference point for the design. The mounting of each component should be considered as the coordinate reference. The coordinate frame can originate on a pin-and-slot mounting. [Placeholder: Defining a coordinate frame helps to determine center of gravity, mass, envelopes...
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Cube Connected Cycles
Other • Cube-connected cycles (CCC) are structures based on hypercubes (see Figure). Given a hypercube of dimension d, each hypercube node is replaced with a ring of size d. This causes the node degree of all nodes to be fixed at 3 regardless of network size! This structure excels when the port...
Custom Communications
Specification • Custom communications specifications by definition are not described by any single specification. The electrical parameters will be determined by the components involved in the design. For example, if the communications utilize gigabit (GTX) transceivers in an FPGA then the electrical requirements will be prescribed by the GTX specifications.
Data Transmit Queue
Specification • When packets from more than one channel are available for transmit, packets shall be transmitted in the order in which they are queued and in accordance with the transmit priority described above.
Data Types
Specification • The JAS standard does not require a specific length or encoding format for data types. Systems can define these based on what best suits their needs. Sizes, endianness, byte ordering, and bit ordering are typically driven based on the processing and memory architectures that are used. However, in order to...
Delayed Case
Specification • A delayed but recoverable scenario occurs when a receive TEP receives at least one CLOSE packet but the transmit TEP does not receive any ACK packets as shown in Figure 3. In this case the receive TEP will eventually transition to the CLOSED state via the timeout and the transmit...
Design Constraints
Specification • The following sections define some important design constraints that the program will levy on the system. The constraints will drive many of the choices in designing the mechanical system.
Design Thickness
Specification • For strength and buckling analyses, minimum material thickness shall be used. Minimum thickness is defined as the nominal thickness minus the lower tolerance and applies to metallic and nonmetallic structural elements. For modeling purposes and stiffness calculations, use nominal or expected values. For flexures the Maximum blade thickness shall be...
Design Ultimate Load
Specification • The JAS mechanical structure shall have sufficient strength to simultaneously withstand design ultimate loads, the corresponding temperature, pressure and accompanying environmental phenomena without failure.
Design Yield Load
Specification • The JAS mechanical structure shall withstand design yield loads, the corresponding temperature, pressure and associated environmental phenomena without permanent deformations, or permanent misalignments, of all components.
Device Access Service
Specification • The device access service, service type address 128, is used to request parameters from or command parameters to a specific device. The currently defined device access service parameters are shown in the following table. Service Type Service Subtype Subtype Description Cmd Tlm Service Parameters Data Types and Description 128 1...
ECSS Packet Utilization Standard
Specification • The figures below show a PUS telecommand and telemetry packet and their utilization within the CCSDS space packet specification. The PUS specification uses the user-definable fields of the CCSDS space packet in order to create a PUS packet. The specification defines a secondary header that provides additional metadata such as...
Electrical Bonding
Specification • Each equipment design shall provide electrical continuity across mechanical interfaces in accordance with the design requirements of this specification. Electrical continuity will be achieved to the maximum practical extent by direct metal-to-metal contact across the entire interface surface. If the electrical resistance across mechanical interfaces is measured to be less...
Electromagnetic Compatibility
Specification • Electromagnetic Interference (EMI) and Electromagnetic Compatibility (EMC) are important design considerations which can be mitigated by the mechanical structure. EMI limits may be in place due to application-specific requirements, but more importantly, EMI can be detrimental to electronics because of the sensitive nature of many of the modern systems and...
Entangled Networks
Other • Entangled networks are a class of networks that attempt to maximize the algebraic connectivity of the topology. These networks can be constructed with explicit complex mathematical methods or approximated by a repetitive random optimization algorithm (which is the method chosen for this analysis) (see Figure). Sample Entangled Networks The repetitive...
Envelope
Specification • The assembled JAS mechanical structure shall attempt to fit the space available without violating any system-level keep out zones.
Environmental Exposure
Specification • Unless otherwise specified, the JAS mechanical structure shall meet these specifications during or after exposure to all environmental conditions specified in the Environmental specification. All of the intended application’s performance parameters must be considered to determine if the mechanical design can withstand the impacts of all environments.
Environmental Specification
Specification • The Environmental Specification provides details about environmental design considerations that should be considered for space applications of JAS. The figure below provides context of where the Environmental Specification resides in the JAS standard. JAS Standard Hierarchy
Environmental Test Flow
Specification • Programs using JAS should practice testing per industry standards wherever possible. The following tests and operational environments shall be applied to the components or structure in the following order. Events 1 through 5 shall be used for qualification acceptance testing. Events 1-6 shall be considered for fatigue calculations. 1) 24ea,...
Error Detection
Specification • Packet errors shall be detected by adding a CRC to each packet transmitted, checking it at the receiver, and discarding any erroneous packet.
Ethernet
Specification • Ethernet comprises a family of networking technologies with numerous media types and standards; 100Base-T (IEEE 802.3-2008:section 8) and 1000Base-T (IEEE 802.3-2008:section 40) the most popular in use today.
Expansion Profile
Other • The Expansion Profile describes a board that provides new capabilities and/or additional resources that would otherwise not be available in standard node instantiations. These modules are not intended to operate standalone and will usually not have individual processing capabilities. Rather, these boards will be populated with components that allow for...
Exposure to Space Environment
Specification • This section is a system level consideration and is included for information purposes only. The view to space shall be considered for both thermal and radiation effects. Thermal-related issue: heat-dissipation Radiation-related: TID (lifetime), SEE, shielding and impact on mass
Factors of Safety
Specification • The JAS mechanical structure shall have strength margins of safety greater than zero when calculated from analytically derived structural loads. The factors of safety (FS), shown in the first table below, and test load factors, shown in the second table below, shall be applied to the limit loads. All laminated...
Fatigue
Specification • The JAS mechanical structure metallic elements shall be designed to withstand the effects of cyclic load condition caused by the design environment. The design environment includes all ground handling transportation, testing, launch and on orbit operational environments indicated in the Environmental Specification. MSFC-HDBK-505 Chapter 7 shall be implemented for fatigue...
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