We like to try to fully-equip the TigerSats Lab to perform an in-house nanosat environmental qualification program, to the greatest extent reasonable within the resource, facility, and safety constraints of our undergrad-centric program, while generating enriching mechanical design projects along the way:

Thermal Vacuum

In order to subject our nanosats to the thermal vacuum (TVAC) conditions that they'll eventually suffer as they orbit in and out of the sunlit portions of their orbit, Carter Green ('20) designed, built, and tested a novel, student-safe (no-cryogen!) TVAC chamber.  The vacuum "chamber" itself is a simple classroom bell jar (PN 1003166 from 3B Scientific) that just happens to be a perfect size for 1U CubeSats or ThinSats!  Inside the chamber, a reversible thermoelectric Peltier cooler alternately moves heat back and forth between the test article and a large heatsink, in order to achieve hot and cold extremes in the test article. 

We have yet to use this TVAC chamber for a true flight qualification program, since we are still fine-tuning its performance (primarily its achievable cold extreme, as well as smart management of the losses intrinsic to the heat flow reversals), but even its preliminary achieved temp extremes are showing promise for use in a real qual program.  

This setup is also somewhat usable for outgassing and TML tests of components (or whole nanosats) per ASTM E595.

Thermal Cycling

For more basic (non-vacuum) thermal cycling, the lab is equipped with a legacy unit of Tenney's TJR ("Tenney Junior") temperature test chamber.  The chamber can convectively cycle a large (up to a 6U-sized) CubeSat or test article all the way from +180C down to -70C.  Our legacy unit has a classic analog Honeywell pen-plotter for temperature logging!

For even more rudimentary thermal "cycling", we can use a simple toaster oven and a -20C lab freezer, both sized for at least a 3U CubeSat.  The latter (ABT-HC-UCFS-0220M from American Biotech Supply) features a well-sealed feedthrough port (to allow for instrumentation/telemetry feedthroughs without major cooling losses).  This particular freezer model can also supposedly be tuned even colder by the manufacturer.  For the toaster oven, we just slip telemetry wires around the edge of the front door, since we are not worried about losses in this case.  We've also started experimenting with using this simple oven for reflow soldering as well.

Simply swapping the test article back and forth between the oven and freezer, while providing well-controlled temp extremes ("plateaus"), does not allow for control of the temperature ramp rates.  But note that ramping too fast should always be conservative.  

 Depressurization

 

Similarly, to subject our nanosats to the more simple depressurization that they'll eventually suffer during launch ascent, we like to try to use a simple hand-pumped classroom bell jar (PN 1010126, also from 3B Scientific, and also nicely-sized for 1U CubeSats or ThinSats!).  We place the test article inside the bell jar, and then try to use the hand pump to roughly approximate the depressurization profiles specified by the relevant launch vehicle user's guide, watching carefully to see if the venting of any semi-trapped air volumes within the test article yield any damage to the article itself.  

We hope to enable more precise, controlled, automated depressurization soon.  To Princeton MAE students: come build this for us!

Shock

In order to subject our nanosats to the shock loads that they may suffer during launch (from launch vehicle stage separations and deployments) , Shalaka Madge ('21) designed a shock hammer fixture (above left).  Our TigerSats Lab is small and crowded, so our shock hammer is a small (~3' x 3' x 3') subscale take on Cal Poly's original large shock hammer fixture (above right, and described in depth here).  A hammer pendulum is manually raised to a known height and dropped, to impact a resonating "drum" plate onto which the test article is mounted. 

Our shock hammer fixture has yet to be built.  It is awaiting some intrepid student to build and instrument it with accelerometers, in order to characterize the shock loads that it is capable of generating (similar to the characterization performed in the Cal Poly paper above).  We aren't yet sure if such a small fixture can generate the shock magnitudes recommended by the various launch vehicle user's guides, but we designed it to have natural frequencies near the typically peak frequencies required.  The peak excitation frequency is intentionally tunable (via adjustability the boundary conditions of the drum plate), as is the shock magnitude (via adjustability of the hammer mass and drop height).  To Princeton MAE students: come build this for us!

Vibration / Acoustic

 

 

 

 

 

For vibration-testing of CubeSats and subsystems, the lab is equipped with Labworks' CubeSat Electrodynamic Shaker Test Station (including their DuoBase horizontal slip table, to enable 3-axis testing).  The shaker (above) is nicely-sized to impart NASA GEVS-level loads on a 1U CubeSat (or perhaps more modest loads on a larger CubeSat).  The system can also impart shock loads similar the shock hammer above. 

 

We were also interested in developing  a more DIY vibration test capability that was cheaper and more student-accessible (perhaps accessible to other schools as well?).  Candace Do ('24) designed, built and tested a motorized (eccentric crank-driven) horizontal shaker (above).  Our assumption was that a motor would be easy for other schools to learn to DIY, replicate and operate (easier than perhaps a solenoid- or voice coil-based DIY system).  The reciprocating motor admittedly limits vibration capability to sinusoidal only (rather than random), but Candace was able to demonstrate the ability to drive the system all the way up to qual-level sinusoidal levels, and to also even use the system for rudimentary (coarse) sine sweeps (to probe for resonances in the test article).  

Other schools could choose their own motor size, in order to strike a good balance between budget and required vibe levels.  We chose to repurpose one of our existing ~$500 high-torque motors, in order to really push the envelope of the system's capability. 

 

 

 

 

 

 

For higher vibe levels (or larger test articles), we use nearby Nu Labs (Annandale, NJ).  Shown above is our ProtoSat (ThinSat) payload on their vertical shaker.  We also use Nu Labs for acoustic testing.

We hope to design/build our own (subscale) acoustic chamber soon! To Princeton MAE students: come build this for us!