the rails. The patents filed by skyTran for this new system are and History Malewicki conceived the basic idea of skyTran in 1990, filing a US patent application that year that was granted as US Patent #5108052 in 1992. He published several technical papers on skyTran in the following years. In 1991, he presented a paper entitled "People Pods Miniature Magnetic Levitation Vehicles for Personal Non-Stop Transportation" to the Society of Automotive Engineers (SAE) Future Transportation Conference in Portland, Oregon. The paper is a thorough description of the concept at that point, although some important features of the current skyTran design are only discussed as options, including magnetic levitation rather than wheels and hanging below the guideway instead of riding above it. The paper describes how Malewicki had built and driven a freeway-legal 154-MPG car in 1981, but realized it could never be safe on a street surrounded by far larger and heavier vehicles. Elevated tracks would allow a very light vehicle to be safe. They are also basic to the system's inexpensiveness, because there is no need to acquire a huge right of way and tear down buildings. It presents an aerodynamic analysis (Malewicki is an aerospace engineer) supporting claims of very high energy efficiency (the paper claims for skyTran's current two-passenger tandem design, though the Unimodal site claims only, "over "). It also described how a very light vehicle that can squeeze both surfaces of a track simultaneously could reliably achieve a 6-G deceleration, allowing it to brake safely to a stop from in just . This level of deceleration, while mechanically impressive, could potentially result in problems such as ruptured blood vessels. The 2008, energy shortages stimulated renewed interest in green vehicle proposals such as skyTran. The "Maglev skyTran" topic quoted a number of skyTran and personal rapid transit ideas, such as passengers exiting and boarding at off-line elevated "portal" stops while high-speed traffic continues to speed by on its main line. In September 2009, the US NASA (National Aeronautics and Space Administration) signed a Space Act joint development agreement with Unimodal. Unimodal has tested prototype vehicles on short guideway sections at NASA's Ames Research Center, in Mountain View, California. NASA control and vehicle dynamics simulation software was made available to Unimodal, which hired NASA subcontractors to program them using US DOT grant funding. In June 2014, Unimodal and Israel Aerospace Industries (IAI) contracted to build a