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Notes from IEEE:

- change in temperature less than 2K across tank [nearly isothermic] 

-24 hour turnover rate of fluid from cryogenic pump

  • Sensors:
    • Static 
    • Floating around 

Would a moving sensor affect the thermodynamics/temperature of the liquid?

Look into: 

  • https://www.realpars.com/blog/thermocouple Thermocoupling 
    • Requires no battery or power draw
  • What homogeneous temperature are we trying to achieve? [so that we know what temperature the sensors have to withstand]
  • Is cost an important factor to the sensor?
  • What is the goal of the sensor suites across the multiple tests? 
    • Is it measuring temperature for all of them?
      • No, look below for the explanation of each test.


  • Optimal Placements for Thermocouplers in the Tank 

1. Tank wall thermocouples

Where: Directly on the metal surface of the cryogenic tank itself, under the MLI, touching the tank’s skin.
How many: Often 8–20, spaced around the circumference and length (top, mid, bottom).
Purpose: Detect hot spots, cold spots, and how evenly the tank is cooled.

Think: small metal dots glued right onto the tank’s external shell.

2. Cooling-loop inlet thermocouple

Where: On the tube that carries cold refrigerant into the BAC loop, right before it touches the tank.
Purpose: Measures the temperature of the coolant before it absorbs heat from the tank.

This is the “entry temperature” of the cooling system.

3. Cooling-loop outlet thermocouple

Where: On the tube where the refrigerant exits the BAC loop, right after it has passed along the tank’s surface.
Purpose: Shows how much warmer the coolant got after absorbing heat.

This is the “exit temperature.”

Inlet vs outlet difference = actual heat absorbed from the tank.

4. MLI outer-surface thermocouples

Where: On the outermost layer of the insulation blanket that wraps the tank, fully outside the MLI stack.
Purpose: Shows how hot the outside of the insulation gets from chamber radiation and heaters.

These sit on top of the MLI, not touching metal.

5. Heater / IR panel thermocouples

Where: Stuck directly on the surface of the heater panels or IR lamp housings that are pointed at the tank.
Purpose: Monitor the temperature of the “fake Sun” to confirm your heat input is stable and known.

  • Understand what each test is doing c

Tests our sensor setups have to perform in:

  • Cryocooler Performance Test
  • Baffle & Pump Cryogenic Flow Test 
  • Thermal Subsystem Demo 
  • Mixing Subsystem Demo 


Thermal Subsystem Demo: 

Testing whether a cryogenic tank wrapped in insulation and cooled by a cryocooler can keep its liquid from boiling away in a space-like vacuum environment.

How-to-test:

  • Boil-off flow: mass-flow meter on vent line (gas phase)

  • Mass loss: weigh the filled tank before/after

  • Level sensor (capacitance/RTD stack) to track liquid height over time

  • Temperatures: many thermocouples on tank wall, loop inlet/outlet, MLI outer surface, heater panels


Mixing Subsystem Demo - Testing that the pump can mix cold fluids with induced heat stratification in low gravity environments. Flight test on parabolic arc with 20 second periods of microgravity, or ground test by spinning the tank to create and artificial gravity and then stopping the tank suddenly.

  • Sensors: thermocouples(mixing of fluid), pressure sensor(LN_2 boils off easily), liquid level sensor(detect sloshing and boil off), flow meter(how much fluid is being moved), IMU/accelerometer(identify periods of microgravity), voltage sensor(how much heat is added for induced stratification)


Sensor recommendations:


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