Satellite Configuration Design - Finite Element Analysis for Satellite Structures - page 29

A circular shape will also be a difficult choice because components require flat
mounting surfaces. In addition, it will be more difficult to package flat solar arrays
on a cylindrical body. The hexagonal shape is reliable, but is more complex in
configuration design. Moreover, it cannot provide the minimal volume criterion for
Small Sat, because it produces relatively large unused spacing inside the configu-
ration envelope. Thus, only square and rectangular shapes can be considered to
provide Small Sat packaging in minimal envelope. However, they present structural
problems at the adapter interface where launch loads are highest. These problems
can be solved during structural design phase by designing a suitable launch vehicle
adapter with sufficient number of fixation connections. The selection between
square and rectangular shapes depends on the packaging approach.
2.7.4 Packaging Approach
The next step is to find the packaging approach that will provide the most surface
area for mounting components. From the previous discussions, the Small Sat
primary structure is a combination between open and closed architecture with
square or rectangular shape, so components can be mounted internally and
externally on structural members. The best packaging option is enclosing the
MBEI, which is the largest component, within the primary structure, while other
components can be mounted externally on structural members. The primary
structure for Small Sat consists of the main load path structure, which is covered
by two plates at the aft and forward ends. Figure 2.7 illustrates the primary
structure of Small Sat.
The main load path structure encloses the payload, so it should take suitable
shape and dimensions to provide mounting the payload inside it and the rest of
equipment outside. The square shape is the best choice for the main load path.
The two plates covering the main load path provide enough surface area to mount
the external components. The first plate, which connects the main load path
structure to the launch vehicle adapter, is called the base plate, while the other
plate at the forward end is called the mounting plate. This plate should contain a
suitable hole to pass the MBEI forward end. Packaging the rest of equipment on
the main load path structure decides the final shape and dimensions of the two
plates. The shape can be square or rectangular, while the outer in-plane dimensions
should be the same with different thicknesses. The outer surface of the mounting
plate carries the components that are directed to the earth. These components are
the X-band antenna, one of the GPS receiver antennae, and two conical antennae
of the S-band equipment. On the other hand, the outer surface of the base plate,
which is connected to the launch vehicle adapter, carries the other GPS receiver
antenna and the dipole antenna of the S-band equipment. The inner surfaces of
both base and mounting plates are suitable areas for mounting other components.
As mentioned before, the total area of the required solar arrays is 3.2 m 2 , which
is divided into four solar arrays. Each solar array is connected to one side of the