Aviation company Boeing has contracted with NASA to build the world's most powerful rocket, intended -- eventually -- to propel astronauts to the moon, Mars, asteroids and the deep space beyond.

Boeing and NASA signed a $2.8 million contract this week, tasking the aerospace company with developing two rocket cores as part of the completion of the Space Launch System, a heavy launch vehicle meant to carry both crew and cargo that will be upgraded over time.

"Our teams have dedicated themselves to ensuring that the SLS -- the largest ever -- will be built safely, affordably and on time," promised Virginia Barnes, Boeing's Space Launch System vice president and program manager.

The contract agreement comes after the space agency reviewed and approved Boeing's SLS core stage designs, a major milestone for the system. The last time NASA completed a critical review of a deep-space human rocket, the year was 1961 and the space agency was on its way to building the Saturn V, the vehicle that would eventually launch the first men to walk the moon.

"The SLS program team completed the core stage critical design review ahead of schedule and continues to make excellent progress towards delivering the rocket to the launch pad," said Todd May, NASA's SLS program manager. "Our entire prime contractor and government team has been working full-steam on this program since its inception."

The two SLS rockets will be even more powerful than the Saturn V. The first version, which is set to launch in 2017 carrying an unmanned Orion capsule, will stand 321 feet tall, weigh 5.5 million pounds and be boosted by four hydrogen-fueled engines left over from the now extinct space shuttle program.

Scientists and engineers have criticized the agency for incorporating spare parts and outdated technology in their construction plans.

The second rocket will be taller and more powerful. Standing 384 feet tall and weighing 6.5 million pounds, the second version will launch a manned mission in 2021 using more powerful J-2X engines and strap-on boosters.