Johndale Solem origin of the shape of rubble-pile asteroids. His analytic theory of the breakup of comets by planetary tidal forces resulted in his calculation of the diameter and density of the parent comet of Shoemaker-Levy 9 as it was before breaking up in the tidal field of Jupiter in 1994 (1994a). Solem's research on interplanetary travel culminated in his MEDUSA concept, a nuclear explosive propelled spacecraft for interplanetary space travel (1994b). Gregory Matloff said this was "a surprising [propulsion] concept which might greatly reduce spacecraft mass." The concept inspired research and elaboration by the aerospace community. At the behest of NASA's
The Elves and the Shoemaker In the 2003 Christmas movie "Elf", shoe making is one of the jobs for elves. The Elves and the Shoemaker "The Elves and the Shoemaker" is an often copied and re-made 1806 story about a poor shoemaker who receives much-needed help from elves. The original story is the first of three fairy tales, contained as entry 39 in the German "Grimm's Fairy Tales" under the common title "Die Wichtelmänner". In her translation of 1884 Margaret Hunt chose The Elves as title for these three stories. The Aarne–Thompson folklore classification system categorizes the story as type 503*: Helpful Elves and also