1. Cryo-Tracker Level, Temperature, and Mass Gauging Fluid Sensors

2. Behavior of Sub-cooled Propellants in Room Temp.
Fig: Liquid Nitrogen unloaded from a small a Dewar Flask to a bucket in a laboratory.

3. Dewar Flask Fig: A 25 l liquid nitrogen laboratory Dewar flask.
Inner wall linings are silvered to reduce heat leakage.

4. Flexible Sensing Probe
Probe is made of series of polyimide layers of thickness mm.
Rakes made of stainless steel tubing, wire, and phenolic insulators weigh (6.70 g/cm).

5. Internal Structure of Cryo-Tracker
Silicon diode sensors incorporated with the probe.
Conductor Traces which constitute the rake of the temp- element

6. Installed Cryo-Tracker Probe
Cryo-Tracker probe 60 ft. long.
2.5 cm wide.
containing 26 silicon diode sensors.
It’s weight is less than 0.59 kg.

7. Stratification of Sub-cooled Propellants
The heat leak causes the propellant to warm and stratify due to natural buoyancy forces.

8. Cryo-Tracker
Initially designed for incorporating in the propellant vessels of reusable launch vehicles.

9. Purpose of Cryo-Tracker
For knowing the amount of propellant loaded in.
For knowing the liquid & ullage temperature.
For knowing liquid level.

10. Mass Gauging Method
The entire liquid and ullage temperature profile is first obtained.
Tank pressure can then be used to calculate a liquid density profile.
Liquid density profile is integrated over the known tank volume.

11. Dual-Purpose Probe. Temperature measured using silicon diode sensors.
Liquid level detection accuracy is a function of the sensor spacing.
For 12 inch sensor spacing, the overall liquid level accuracy is ± 6 inches.

12. Performance Consistent thermal response can be
seen between the sensing elements in
a dual-element probe when it’s thermal-cycled in liquid nitrogen.

13. Hot-Fire Test (anomaly condition)
The probe is also capable of measuring transient fluid temperature changes.
Figure : Tracking the rapid change in liquid oxygen temperature when warm gases injected into the tank mixed the contents.

14. Advantages of Cryo-Tracker
Operating Costs
Accuracy
Reliability
Safety
Efficiency
Scalability
Flexibility

15. Commercial Applications
Cryogenic storage and transport tanks
Home oxygen vessels
Medevac helicopter and military field hospital oxygen-generating systems
Automobiles running on liquid hydrogen or liqufied natural gas