NASA has finally started moving forward with the Space Launch System (SLS). Costs through 2017 are expected to reach $18 billion, according to the agency. Where's the money going and what will it accomplish?

At the top level, NASA will get roughly $3 billion dollars over the next six years to build a big heavy-lift rocket for $10 billion, put an additional $6 billion into the Orion Multi-Purpose Crew Vehicle (MPCV) and $2 billion for infrastructure improvements at Kennedy Space Center. The rocket will be capable of carrying both crew and cargo. 

By the end of 2017 – but more likely in 2018 by most calculations – a baseline heavy-lift rocket will make its first test flight from Kennedy Space Center, most likely carrying an unmanned MPCV and a Delta IV second stage. The first stage will use three surplus space shuttle Pratt-Whitney Rocketdyne RS-25D engines, and have a diameter of 8.4 meters – the same size as the space shuttle external tank (ET).

Assembly of the first core stage will likely take place at the Michoud Assembly Facility in New Orleans. The stage will be built vertically to save money, rather than horizontally like the shuttle's ET. NASA pictures of SLS show the first stage of the ET painted in white and black in a throwback to the Saturn V, but other reports indicate the first stage will be covered in the orange thermal foam , just like the shuttle ET. Attached to the first stage will be a pair of ATK (News - Alert) five segment solid-rocket boosters (SRBs), bigger cousins of the shuttle's four segment SRBs.

The second stage on the test flight is expected to be a Boeing Delta IV upper stage. Future launches would swap out the Delta IV for an upper stage powered by a single Pratt Whitney Rocketdyne J-2X (News - Alert) engine derived from J-2 engine used during the Apollo program.

To evolve the rocket up to a Congressionally-mandated 130 metric tons, the first stage would move from 3 to 5 RS-25 engines, and those engines would be RS-25Es, specifically designed for one-use affordability rather than built for reusability like the RS-25Ds.

Building the first stage core is the biggest technical risk in the test-flight configuration, according to NASA officials and I can see why. The surplus RS-25D engines are known entities, having flown on (and returned) on numerous shuttle missions. ATK has run several full-up tests of the five segment SSME, and the Delta IV upper stage also has a solid flight history.

A preliminary iteration of the Lockheed Martin (News - Alert)-built Orion MPCV should also be available, given NASA was boasting about making the first weld on the first "space-bound" capsule on September 9 at Michoud. It isn't clear if the SLS test will use a factory-new Orion or recycle/reuse an Orion capsule from a previous test. The MPCV is intended to be re-used and refitted for multiple flights.

In some respects, $18 billion is a lot of money, but in others, it barely gets SLS to an unmanned test flight. More money will be needed to mature SLS to take a manned spin around the moon by 2021.