Metal matrix sheets

Gas flow holes through sheet

Figure 7.22. Fuel element structure and assembly inside a MITEE reactor (MITEE http:// ).

Outwardly similar to conventional NTR (see Figure 7.21) , MITEE designs use fuel elements where hydrogen propellant flows radially inwards, crossing the metal matrix composite encapsulating the fissioning fuel, as shown in Figure 7.22. This flow topology produces a compact NTR. While most initial MITEE designs used only 235U as fuel, recent MITEE proposals include also 233U and 242mAm, since these materials produce even more compact engines (242mAm has a critical mass about a hundred times less than that of uranium). Published estimates of engine size and mass are surprising: total engine mass (using 235U) 200 kg for a 75-MW NTR, with Isp = 1,000 to 1,250 s for the combined cycle described below (and assuming realistically that nozzle expansion is frozen) and a thrust of order 1.4 x 104N. The engine mass is estimated to drop to 100 kg replacing 235U with the much scarcer 242mAm metastable isotope [Powell et al., 1998, 1999, 2004; Maise et al., 2000]. A recent MITEE NTR design is claimed to be capable of Isp about 1,000 s (based upon a hydrogen exit temperature 3,000 K), overall weight 140 kg, total one-time burn of several hours, with engine diameter 50 cm corresponding to a power density of order 10 MW/liter. Figure 7.23 shows a comparison between a hypothetical MITEE-class nuclear rocket and some typical chemical rockets for interplanetary missions already proposed or considered.

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Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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