Development of the Space Launch System currently includes a lot of computer simulations.
It's possible that no NASA Administrator has enjoyed appearing in front of Congress since the 1960's. Charlie Bolden's testimony in front of both the Senate and House oversight committees for his agency last Wednesday was likely to continue that trend.
Although there was some argument over the 20 percent cuts to the Mars exploration program and NASA's commitments to the ESA, the key issue in both the Senate and House hearings was a philosophical difference over how to get humans into orbit. The legislators favored NASA's Space Launch System, known among its detractors as the "Senate Launch System," over CCDev, the Commercial Crew Development program. The two shouldn't conflict, given that they are meant for completely different purposes, but in these highly-politicized times, they do.
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