Structure

Current Design Status

The figure below shows the current CAD model of LISSA as of June 25 2025. Currently the FM primary structure is being manufactured to test and verify Phase D FM solar array deployment requirements  

Model Philosophy

Four models will be used when developing the structure for LI Bus. A CAD model was made in Phase A and will be updated as the spacecraft is developed. This model will be used extensively through all phases. Requirements which are verified by design or analysis will use the aforementioned CAD model. A 3D printed breadboard model (BBM) was also created early in Phase B. This model is used to assist with assembly designing and planning, specifically for harnessing tests and practice. The BBM will be updated when major changes are made to the structural design or layout, and will be used to as one of the checks to make sure that the new design fits together well. The engineering model (EM) will be used for practice and test assemblies similar to the BBM, though with more detail and fidelity. Critically, the EM will be capable of performing functional tests of the deployable components. Finally, a flight model (FM) structure will be manufactured in Phase D. This will be used for the final assembly of the bus when it is to fly in space.

The following diagram shows the functions of the structure, and how they flow down to lower levels. Three upper-level functions are defined: mounting, deploying, and protecting. These serve as the basic purposes of the structure subsystem. With specific regards to the protecting function of the structure, design decisions will be made based on the expected launch and handling loads, as these will be significantly greater than any on-orbit loads. 

Model Coordinate System

Deployer Coordinate System: based on ISIS Advised Envelope, 6-Unit CubeSat Dimensions, ISIS.STS.0.1.006 Rev D.  

Overall Structure Layout

The overall structural layout is shown in the figure below. More detailed information can be found in the ICD page.

Mass Budget 

The table below should be used as a general guide for all other subsystems when considering the maximum mass constraint of the satellite as determined by requirement R-LIB-STR-60. 

General Physical Properties

Total Mass (according to CAD model): 7.5 kg

Center of Mass: (7.3 mm, 18.7 mm) away from the geometric center in the (closed, open) configuration. 

Inertia Tensor (about the center of mass with respect to model coordinate system):

Testing Methodology

As of the end of Phase C an EM of LI-Bus is built. This EM will serve as a physical testing/prototyping model that will be used to create the final FM version of LISSA. Specifically, solar wing deployment and harnessing related tasks will be conducted on this model to ensure the FM version of LISSA is built according to all specified requirements.