AAWSAP DIRD, Laser Lightcraft Nanosatellites, November 2010

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The communications subsystem is further complicated by constellations requiring spin­
stabilized nanosats. A spinning nanosat cannot easily point an antenna toward Earth.
Therefore, a low gain omni antenna is assumed and communications must take place
near perigee, when the range is 3 to 5 Earth radii. A large ground antenna and high
data rate compression must be used to achieve reasonable data rates with minimum
power. This places an additional burden on the ground stations for both sensitive
receivers/bit synchronizers and advanced decoders. These same considerations limit
data rate for satellite-to-satellite communication.
Although the inclusion of an onboard command receiver is highly desired, it puts an
additional strain on an already challenged nanosat mass and power budget. For this
reason, the concept of a totally autonomous, receiverless nanosat design appears most
attractive. However, "receiver-on-a-chip" technology has advanced to the point where
including a receiver onboard looks feasible. The biggest disadvantage of a receiver now
becomes the ground personnel and software needed to support the ability to command
the nanosat. Command actions taken onboard will of course be limited to basic
functions such as "transmit data" because of the lack of redundancy and mechanical
functions. Although scenarios have been defined to allow nanosats to autonomously
determine when to transmit their stored data, utilizing a receiver to control the
telemetry downlink from the ground still has value. The capability of uploading flight
software changes, as well as sending a master reset if necessary, would also exist with
such an onboard command receiver.
MECHANICAL AND STRUCTURES
The nanosat mechanical system will be kept as simple as possible. The ideal nanosat
mechanical design should consist of a one-piece structure on which all other
components are mounted.
Multifunctional structures can provide thermal control, shielding and serve as substrates
for printed circuit boards. For example, diamond facesheet honeycomb panels can
serve as a structure, thermal conductor and radiator, and printed circuit board
substrates. The diamond facesheet provides ten times greater thermal conductivity
than aluminum and can dissipate heat from high power density electronics modules
with a low mass comparable to carbon fiber composites. Another example is the
structural battery system. It consists of a honeycomb panel whose core is filled with
the cells of a nickel-hydrogen battery (or other flight qualified cell technology).
Concurrent engineering and fabrication techniques will be used to create a single
computer model for the design, analysis (structural, thermal, and dynamic), and
fabrication of the nanosat and its components. Dynamic modeling capabilities to
simulate nanosat deployments will provide faster designs and a reduction in the amount
of deployment testing required. This approach will significantly lower development
costs by reducing duplication of effort, chances of errors, the number of drawings and
paperwork required.
Mass production techniques not traditionally used for spaceflight hardware will be used,
such as casting and injection molding. Options being considered for the nanosat
structure material are: cast aluminum; cast aluminum-beryllium alloy; injection molded
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