2 Replies Latest reply on Mar 5, 2018 12:33 PM by Bill McEachern

    Lifting simulation for a CubeSat. Linear Dynamic/Base Excitation or Static/Gravity Force?

    Chris Jan

      I'm trying to simulate the launch of  CubeSat which is essentially a lifting simulation.

      Now I am having trouble as to which force to use.

       

      One option is using Linear Dynamic->Base Excitation Force.

      Second option is using Static->Gravity Force.

       

      In this paper (page 68) https://web.wpi.edu/Pubs/E-project/Available/E-project-031212-121649/unrestricted/Mechanical,_Power,_and_Thermal_Subsyst…  Option 1 is used.

      The second option would be the more logical option I'm guessing though.

       

      I've ran the simulation using both methods and I get very similar but slightly different results. Which force should I use to best simulate static loads acting on the CubeSat during launch.

        • Re: Lifting simulation for a CubeSat. Linear Dynamic/Base Excitation or Static/Gravity Force?
          Chris Jan

          Has this been posted, can people see this thread? I'm getting a message at the top saying "Please note: your content was added successfully, but a moderator needs to approve it before it can be posted."

            • Re: Lifting simulation for a CubeSat. Linear Dynamic/Base Excitation or Static/Gravity Force?
              Bill McEachern

              In my experience it generally works like this: Some one (typically the launcher authority) does a CLA (coupled loads analysis) of the launch vehicle with the satellites using payload masses and this will provide you with the quasi static loads and it will typically give you what frequencies are likely to be encounter. You run natural frequency calc's on your payload and try to get a minimum first mode above some number - might be supplied by the bus manufacturer - the frequencies that the CLA produces with all the relevant masses and structures (bus) included other than the payloads. You run the sine environment to gauge susceptibility to vibrations typically under 100 Hz. Your quality factor (damping factor) essentially drives the response at resonances. You may also have a random environment. You design your payload and qualify it to the environment, then another CLA is done to confirm all is within the previously defined regime. It may take more than one cycle to sort it all out. Acoustic is another case but it is usually handled by test.

              I suspect that a cube Sat in its entirety would be considered a payload as it is likely stuck on some other structure and it is not the primary payload of the launch vehicle. It would be stuck on another satellite or a distributor (the bit that all the satellites attach to if many are being launched). The attached document gives a description of the process that might be helpful.