Nelson J. Gernert

Aluminum foil lined composite tubing

This paper describes the development of lightweight aluminum foil lined polymer matrix composite tubing for applications ranging from heat pipe construction to fluid transport tubing and tankage structure for future spacecraft. The metal lining is completely hermetic and endows the tubing with metal like characteristics without compromising its lightweight or strength advantages. It consists of one wrap of 0.076 mm thick aluminum foil that is rolled in a cylindrical shape and seam welded. Each end of the foil tube transitions to a short section of heavy wall aluminum tubing that is welded to the foil tube creating a leak tight lining. Composite fibers are braided over the lining and then resin transfer molded. The epoxy resin bonds to the fibers and to the lining, forming an integral tube. The demonstration tubing that was constructed was 25.4 mm in diameter, 4.57 m long and had an average mass per unit length of 0.131 kg/m. Extension of this technology to other metal lining materials for containment of v...

Advances in High Temperature Titanium‐Water Heat Pipe Technology

A development program has been completed to design, assemble, and test high‐performance titanium/water heat pipes for spacecraft heat rejection applications. Three variations of wick designs were designed, assembled, tested, and delivered to NASA GRC. The heat pipe length was 115.5 cm, the outer diameter was 1.27 cm, and the charged devices weighed 285 g. All wick designs were based on porous‐walled axially grooved titanium wick structures. All three variations exhibited high heat transport capability at adverse tilt conditions. Transport capability of the devices at 225 °C ranged between 800 W and 1000 W against gravity. The results represent a significant advance in the technology capability for passive heat rejection in this temperature range.

Loop heat pipe radiator

This paper describes the design and testing of a Loop Heat Pipe Radiator (LHPR) which was developed as an alternative to state‐of‐the‐art axially‐grooved heat pipes for space‐based heat rejection which would be usable with tubing made of aluminum foil covered with a carbon‐epoxy composite. The LHPR had an aluminum envelope and a polymer wick, and used ammonia as a working fluid. It was 4 meters long with a mass of 1.4 kg. The LHPR transported 500 watts at a 2.3 meter adverse inclination and 1500 watts when horizontal. This non‐optimized LHPR had a 3000 watt‐meter capability, which is four times greater than an axially‐grooved heat pipe of similar power‐handling capability and mass. In addition to a higher power handling capability, the LHPR has a much higher capillary margin than axially‐grooved pipes. That high capillary margin simplifies ground testing in a 1‐g environment by reducing the need for the careful levelling and vibration reduction required by axially‐grooved pipes.

Composite material heat pipe radiator

Organic matrix composite material is recognized for its significant strength to weight ratio when compared to metal and consequently was investigated for reducing the mass of heat pipes for future space missions. The particular heat pipe that was constructed and tested was made from an organic matrix composite material applied to a linear of titanium tubing spun to foil thickness (0.076 mm). The thin liner transitioned to heavier‐walled ends which allowed the tubing to be sealed using conventional welding. More specifically, the heat pipe was 1.14 m long, 24 mm in diameter and had a mass of 0.165 kg. Water was the working fluid. The heat pipe was tested in a Thermacore thermal vacuum chamber under hot and cold wall operating conditions. The heat load dissipated ranged from 10 to 60 watts. Heat pipe operating temperatures varied from 278 K to 403 K. After testing, the heat pipe was delivered to NASA JSC where future thermal vacuum chamber tests are planned.

Life Test Results for Water Heat Pipes Operating at 200 °C to 300 °C

For lunar or planetary bases to be viable, a robust electric generating system will be required for powering the habitat. Water heat pipes offer an attractive solution for lunar base heat rejection, and would serve as a qualification for them on other long duration missions. Successful operation near the upper end of water operating range is a requirement for the application. Results are reported for life tests on water heat pipes that were operated at various temperatures between 200 °C and 300 °C. Tests were conducted on twenty three gravity‐assisted water heat pipes. Eleven titanium/water heat pipes and ten Monel/water heat pipes were tested at temperatures above 200 °C. Two cupronickel heat pipes were also assembled and tested. Titanium alloys tested included CP‐2 titanium, as well as two beta‐titanium alloys, namely 15‐3 and Nitinol alloys. Some of the titanium alloy life tests used wicks fabricated from CP‐2 titanium screen or porous felt. Monel alloys tested included 400 and K‐500 alloys. Some of t...