Todd May (NASA photo)

HUNTSVILLE, Alabama - NASA has a "handshake" agreement with Boeing to build the core stage of the Space Launch System that will lead to a $2.8 billion contract as soon as "the paperwork matches the handshake," SLS Program Manager Todd May said this week.

May was interviewed Thursday about SLS progress at an annual Marshall Space Flight Center update to industry and government leaders at the U.S. Space & Rocket Center about the agreement. The briefing included a summary of NASA's impact on the Alabama economy.

May discussed each of the risks to SLS launching on time in 2017 raised in a General Accountability Office (GAO) report released this week. The GAO cited contracts not nailed down yet as one concern.

"That's the lion's share of what's left to go," Todd said of the Boeing deal. "The only thing left is the ICPS (Interim Cryogenic Propulsion Stage) and that's roughly 2.5 percent of the budget to the first flight. So, the core was the big thing, and we finally got to an agreement there."

Here's what May said about other risks mentioned in the GAO report:

1. Sufficient continued funding. Funding has been steady for the past four years and is locked in through 2015, May said. "That risk to us looks a lot less than it did even a year ago," May said.

2. The tight schedule. "We actually still have margin on our critical path to the delivery date to Stennis (Space Center) of the core," May said. The program has met critical path deadlines since 2011, he said, and is on track.

3. Hardware development. "The riskiest thing in the development of a rocket is the engines themselves," May said. "That hardware is built and sitting down at Stennis today. We're about to take one of those and put it on the stand in July. In my opinion, the biggest hardware risk is already retired."

May was referring to the leftover space shuttle engines being used on the first SLS flights. May also said the issue of liquid hydrogen fuel being too cold for the new rocket's engines has been solved. The SLS tank is on top of the engines, much closer than the external shuttle fuel tank, so the hydrogen fuel has no time to warm up to launch temperatures en route as it did on the shuttle. That's been solved by adding fuel line heaters, May said.