The Ares was meant to be simpler, cheaper and more reliable than the shuttles. If it ever carries astronauts, they will be in a cone-shaped capsule on top of the rocket -- considered safer than the shuttles, which are attached to the side of their external tanks and have often been hit by debris falling from the tanks during launch.
The 2003 Columbia tragedy was believed caused by foam from the fuel tank, coming off and damaging the shuttle's wing.
Ares has been plagued by cost issues. The Constellation program to replace the shuttles, of which the Ares rockets are a part, was originally slated to cost $28 billion, but may ultimately reach $44 billion -- if it continues as currently planned.
When Ares was first conceived during the Bush administration, NASA expected it would be launching crews by 2012. But an independent White House panel, chaired by former aerospace executive Norman Augustine, said last week it would be surprised if an Ares carried astronauts before 2017. The Augustine Commission said one option, among many, for the Obama administration would be to cancel the Ares 1 and look for alternatives.
ABC News' Gina Sunseri contributed reporting from the Kennedy Space Center.