The authors have studied the entry and impact behavior of an isotope heat source for space nuclear power that disassembles into a number of modules that would enter the Earth's atmosphere separately if a flight aborted. These modules are disk-shaped units, each with its own re-entry heat shield and protective impact container. In normal operation, the disk modules are stacked inside the generator, but during a re-entry abort they separate and fly as individual units of low ballistic coefficient. Flight tests at hypersonic speeds have confirmed that a stack of disks will separate and assume a flat-forward mode of flight. Free-fall tests of single disks have demonstrated a nominal impact velocity of 30 m/sec at sea level for a practical range of ballistic coefficients. Thermal and structural calculations indicate re-entry survival under all possible re-entry conditions for speeds up to and including Earth escape speed.
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