FEA is used to determine stress and vibration in optical instruments
When designing optical instruments for space vehicles, one must take specific into account certain considerations, to ensure successful performance capabilities. This blog hopes to introduce the following: (1) the importance of material selection; (2) environmental considerations; and (3) challenges that optomechanical engineering teams encounter.
Effective mechanical engineering design of optical instruments requires advance knowledge of the adverse environments under which the product is expected to successfully operate, e.g. temperature, pressure, vibration, shock, moisture, corrosion, contamination, fungus, abrasion, erosion, and high radiation. These all can affect the performance of optical instruments and their useful life cycle in space and elsewhere. The optomechanical engineer must carefully select the materials to maximize environmental resistance, in order to ensure the proper operation of the product over the expected useful lifetime. Often an optomechanical engineer relies on the combined skills of an engineering team composed of other specialists. Mechanical engineers may perform FEA to determine stress and vibration; electrical engineers may help design the controls and electronics. Materials scientists and materials engineers help to specify and test the materials of design. Ocassionally, one even finds a use for a physicist.
Environmental conditions in space vary widely, and may be severe. In the extreme conditions of space, optical instruments must be able to survive without progressive deterioration or permanent damage, yet still perform in accordance with project specifications. Therefore, defining the expected environment of the optical instruments in space as well as under launch, operating, storage and transportation logistics are absolutely critical. All conditions must be managed as early in the design phase as possible to ensure appropriate provisions are made.
Space provides a harsh environment that challenges scientists, and engineers to meet design optical payload requirements in this type of environment. Various environments exist for operation, storage, and transportation of flight hardware such as optical systems. In a controlled environment, such as a laboratory, the product would have a different set of conditions than a system designed for the military, or space flight.
One common mistake novice optomechanical engineering teams make when designing for space is to neglect the vacuum of space. Human beings are used to atmospheric pressure of 101 kPa (14.7 psi) and 21% oxygen. Astronauts require this ambient pressure, but it creates an internal pressure on a space vehicle. The pressure differentials can cause fractures or deformations in the structure, loss of hardware functionality, even explosions, not to mention millions of dollars lost on the project.
An example of this is an optomechanical engineering team forgot to take pressure differentials into account when design a portion of a satellite. One of the multi layer insulation blankets came loose and covered up most of the optical mirror. This essentially took away most of the satellite’s vision and resulted in limited data retrieval.
Space is the final frontier and represents a myriad of unknowns that can compromise space vehicles used for human exploration. Optomechanical engineering personnel must attempt to account for all of the conditions that could affect their optical instruments, or risk damaged equipment and million dollars wasted.