Gemini spacecraft

Solid polymer electrolyte FCs (SPEFCs) were developed last, but, paradoxically, they were the first to have a "commercial" application they powered the on-board instrumentation of the Gemini spacecraft and still power that of the biosatellite. Their acid electrolyte is micro-encapsxilated or laminated onto a proton-exchange membrane. The working temperature is a little above r. t (60-90 C) [7]. 

A first version of polymer electrolyte membrane fuel cells, which had a power of 1 kW, was built in the early 1960s by the General Electric for the Gemini spacecraft. 

Corrosion of the plates not only detracts from their mechanical properties but also gives rise to undesirable corrosion products, namely, heavy-metal ions, which, when depositing on the catalysts, strongly depress their activity. The corrosion processes also give rise to superficial oxide films on the metal parts, and these cause contact resistance of the surfaces. For a lower contact resistance, metallic bipolar plates sometimes have a surface layer of a more stable metal. Thus, in the first polymer electrolyte membrane fuel cell, developed by General Electric for the Gemini spacecraft, the bipolar plates consisted of niobium and tantalum coated with a thin layer of gold. A bipolar plate could also be coated with a layer of carbide or nitride. 

From the very beginning of modem fuel cell development, potential applications for military purposes were an important driving force and source of financing of this R D work. In the early 1960s, for example, the work of General Electric on membrane-type fuel cells that led to the power plants for Gemini spacecraft was financed, in part, by the US Navy s Bureau of Ships (Electronic Division) and by the US Army Signal Corps. 

The improved PMFC for the Gemini spacecraft was based on a perfluori-nated Nafion membrane. This membrane possesses substantially improved characteristics compared to the PSSA membranes particular types of Nafion membranes are characterised by a hfetime of 50 000 h. Different types of Nafion membranes have different equivalent masses (grammes of polymer per mole H+), namely, 1200 (Nafion 120), 1100 (Nafion 117 and Nafion 115) and 1000 (Nafion 105). 

First models of hydrogen-oxygen fuel cells with an ion-exchange membrane as the electrolyte were built and used in NASA s Gemini spacecraft. After a very long break, this development was taken up and led to the modem PEMFCs described in Chapter 3. 

As to the use of fuel cell-based power plants in other transport means, we have repeatedly spoken in the present book about practical applications of such plants in manned spacecraft. The first examples were 1-kW PEMFC plants used in the 1960s in Gemini spacecraft, now outdated then three 1.5-kW AFC plants each used in Apollo-ty t spacecraft in the 1970s, and finally, three 12-kW AFC plants each in the Orbiter space shuttles used until the present. 

The early versions of the PEMFC, as used in the NASA Gemini spacecraft, had a lifetime of only about 500 h, but that was sufficient for those limited early missions. The development program continued with the incorporation of a new polymer membrane in 1967 called Naflon, a registered trademark of Dupont. This type of membrane, outlined in Section 4.2, became standard for the PEMFC, as it still is today. 

The fiiel cells that use electrolyte gels are polymer electrolyte fuel cells (PEFCs). These fuel cells were used in the Gemini spacecraft during the 1960s and also the first to be commercially available. 

The thickness of the electrolyte layer may be as little as 1 mm. In the fuel cells used in the Gemini spacecraft the electrolyte was replaced by an ion-exchange membrane. This provided a conducting bridge between the electrodes, and contributed to the mechanical strength it also supplied a source of drinking water, since the product of the cell reaction (one pint of water per kilowatt-hour) could be collected in a pure state. 

These cells are also known as solid polymer fuel cells (SPFC) (Fig. 1.9). These fuel cells were used in NASA Gemini Spacecraft (manned space vehicles) and were developed in 1960 by General Electric (USA). The following key features of PEMFC make them very popular ... 

---