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Sensors for Space Telescope Lens Testing

By on May 23, 2019 in Cryogenic environments, Displacement Sensor, Fiber Optic Vacuum Passthru, Fiberoptic Sensors, multiplexing sensors, Non-Contact Sensing, Quality Control, space cryogenics, Space Telescope Lens

The Euclid Satellite project a good example of Philtec’s sensors being used with excellent results in cryogenic conditions. A technical paper published in 2012  shows Philtec’s high precision sensors were successfully used at 150°K to verify the distortion of lens holders to be <1 micron,  well within the project requirements.

This month Philtec has again delivered sensor systems for space telescope lens distortion measurements. These are 2-channel fiber optic displacement sensor systems designed for 3.2 mm operation in vacuum.

2-Channel Displacement Sensor with BvF120 Vacuum Passthru Assembly

Seven 2-channel sensor systems were delivered with the following options:

  • Multi-Channel Vacuum Passthru Assembly in 120 mm Custom Flange
  • SS Interlok Cable Jacket in Vacuum
  • 6m Total Fiberoptic Cable Length (1.5 in air, 4.5 in vacuum)
  • Low CTE Invar Tips

The fiber optic cables are trifurcated for connection to the vacuum passthru (one transmit bundle and two receivers). With 14 sensor channels x 3 legs each, 42 vacuum ports were required. Each BvF120 has 16 ports, and therefore three BvF120 assemblies were used to pass all channels.

Multi-Channel Vacuum Passthru Assembly

REFERENCE

‘Test Results of High-Precision Large Cryogenic Lens Holders’, 2012, Proceedings of the SPIE Publication “Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II”.

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Probes for Cryogenic Turbo Pumps

By on December 11, 2018 in Aerospace, Cryogenic environments, cryogenic turbopumps, Fiberoptic Sensors, High pressure environments, Liquid Oxygen, Non-Contact Sensing, space cryogenics, Space Launch Vehicles, Uncategorized

Philtec builds custom displacement sensor systems to meet application requirements, which often include extreme environments. This month we delivered 8 sensors having 200 KHz bandwidth (sensor speed). The probe tips are threaded and connectorized so they may be separated from the sensor electronics.

Probes are Connectorized to the Electronic Modules 
Probe Tips are Immersed in LOX at -300°F and 1,000 psi
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Aerospace Customer References

By on June 25, 2018 in Aerospace, Cryogenic environments, cryogenic turbopumps, Fiberoptic Sensors, High pressure environments, Space Launch Vehicles

Philtec is well known throughout the worldwide aerospace community. Here are some of the companies that have used Philtec’s sensors in their test and development programs..

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ROCKET ENGINES for SPACE LAUNCH VEHICLES

By on April 3, 2018 in Cryogenic environments, cryogenic turbopumps, Fiberoptic Sensors, High pressure environments, Measurements in fluids, Non-Contact Sensing, Rotor Dynamics, Space Launch Vehicles

A new generation of LOX/Methane engines are under development, and many have used Philtec’s FODS (Fiber Optic Displacement Sensors) for rotor dynamics measurements in the testing phase. Fiber optic probes are an ideal sensor choice in these applications where they are exposed to pressurized cryogenic fluids.

In 2016-2017, 100 sensors are delivered to companies testing advanced turbopump designs.

READ MORE

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Fiber Optic Displacement Probes in Liquid Oxygen

By on February 9, 2018 in Cryogenic environments, cryogenic turbopumps, Fiberoptic Sensors, Liquid Oxygen, Methane, Non-Contact Sensing, Submerged in fluids

When the cryogenic medium is Liquid Oxygen (or Liquid Natural Gas), calibration in water is a better approximation than calibration in air:
Air Refractive Index = 1.000
Liquid Oxygen Refractive index = 1.221
LNG Refractive Index = 1.286
Water Refractive Index = 1.332

A sensor’s operating range is extended in proportion to the ratio of the refractive indices.

For example, to calculate a sensor’s response in LOX, first calibrate the sensor submerged in water. Then remap the displacement data by the ratio 1.221/1.332.

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Cryogenic Turbopumps

By on March 17, 2017 in Cryogenic environments, cryogenic turbopumps, Fiberoptic Sensors, High pressure environments, Liquid Hydrogen, Liquid Nitrogen, Liquid Oxygen, Measurements in fluids, Methane, Space Launch Vehicles, Submerged in fluids

Space launch vehicles use liquid propellant rocket engines with high-pressured turbopumps to deliver extremely low temperature propellants of liquid hydrogen, liquid nitrogen, liquid oxygen or liquid natural gas (methane) to a combustion chamber in the engine. During developmental testing of advanced turbopump designs, engineers monitor the radial and axial displacements of the rotors over the entire speed range of operation.

Philtec’s FODS (Fiber Optic Displacement Sensors) are being successfully used for rotor dynamics measurements in cryogenic fluids. When a fiber optic probe is submersed in a fluid, light rays diverging from the probe tip are more collimated than they would be in air. This increases the operating range of the sensor. The degree of collimation is proportional to the index of refraction of the fluid.

Refractive Index of Common Cryogenic Fluids

1.0002926   Air

1.0974   Liquid Hydrogen

1.2053   Liquid Nitrogen

1.221      Liquid Oxygen

1.286     Liquid Natural Gas (Methane)

OPERATION IN CRYOGENIC FLUID, EXAMPLE

Philtec provides the rocket engineers with a calculated best estimate of sensor performance following this example:

  • calibrate the displacement sensor in air (or water), then
  • rescale the gap data to derive an estimate of the sensor output in the cryo fluid.

For example, a sensor is calibrated to a target surface in Air with Refractive index of 1.0002926

For a probe immersed in Liquid Hydrogen with Refractive index of 1.0974, the sensor’s calibration gap data is scaled by the ratio of the Refractive Indices:

1.0974 ÷ 1.0002926 = 1.0971

Two calibration charts are provided: One for operation in Air; one for operation in LH2

Example Chart_LH2

 

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