NASA

NASA

NASA

NASA

NASA

NASA

NASA

NASA/MSFC/Emmett Given

NASA

NASA

NASA

NASA

NASA

NASA/Bill Ingalls

NASA/Bill Ingalls

NASA

For most of the last five years, NASA’s space launch system has been largely a PowerPoint rocket, consisting of designs on computers and disparate hardware in various stages of development across the United States. But now the massive SLS rocket is starting to come together, and senior NASA managers are optimistic about its future.

“This is an amazing period of time in US spaceflight,” Bill Gerstenmaier, chief of human spaceflight for NASA, said last week during a meeting of the agency’s advisory council. “I’m starting to see a real shift from just kind of hardware development to almost a flight cadence. The volume of work is just amazing.” He added that with “roughly” two years to go before the first launch of SLS and the Orion spacecraft, the agency is beginning to test flight hardware.

Barring further delays, the maiden launch of SLS will occur between September and November 2018. Until now NASA has been mostly designing and building individual components of the massive rocket, which will have an initial capability to heft 70 metric tons to low-Earth orbit but may eventually grow into a 130-ton rocket. However, now the focus is turning toward testing that hardware and, later next year and in 2018, beginning to integrate it for launch.

Historically during development programs, this is where the most problems and potential delays occur, as systems may not work together exactly as intended. And the SLS rocket has a lot of different parts. For the core stage, which provides the primary thrust, there is the liquid oxygen tank, the intertank, the liquid hydrogen tank, and the engine section. The core stage also houses the vehicle’s avionics. At the side of the core stage are two solid rocket boosters, which provide initial thrust off the pad. Then, atop the core stage, is the upper stage which provides thrust later during the flight. Finally there is the payload itself, the Orion spacecraft and its service module, which are also under schedule pressure to meet the 2018 flight.

Gerstenmaier acknowledged as much during his comments last week. “We’ve got reasonable margin in our schedules,” he said. “It’s foolish to think there won’t be problems ahead of us, that’s the nature of a development program. I guarantee there will be more stuff coming. But we’re in the process of building a robust schedule that can deal with the challenges ahead of us.”

Costs

It is costing NASA a lot of money to do all of this work. The agency has committed to spending $23 billion (~£17 billion) from 2011 through 2018 to get SLS and Orion ready for a maiden flight, and that doesn’t include another $9 billion spent before 2011 during the Constellation Program, under which work began on Orion and a precursor rocket to the SLS.

NASA has not said how much it will cost to continue development of these launch systems beyond 2018, nor, critically, has it specified the amount of the ongoing, or fixed costs, once the SLS begins flying once every other year during the mid-2020s. These fixed costs for the space shuttle were about $2.5 billion annually, meaning that much was spent on expenses whether the vehicle flew or not. NASA luminaries such as Chris Kraft have warned that the SLS fixed costs will "eat NASA alive."

Accordingly, one of the biggest concerns when it comes to the SLS and Orion is that the vehicles will cost so much to build and fly, precious little money will be left behind to develop hardware for meaningful missions, such as lunar orbit stations or flights beyond the Earth-Moon system. “I can understand where one would come to that conclusion,” Bill Hill, the headquarters official who oversees development of SLS and Orion for NASA, told Ars in an interview. “We are in the process of defining flight test objectives, and we believe at least for now we can do a lot of this under the current budget level. We’re trying to pace ourselves.”

“Better than I expected”

But to get to those test objectives in space, NASA must first complete them on the ground. At the Michoud Assembly Facility, Hill said, work is proceeding on “qualification” tanks for both liquid hydrogen and liquid oxygen. These tanks will be shipped to the Marshall Space Flight Center later this year for testing. Meanwhile work is also proceeding on the actual fuel tanks to be used for the 2018 test flight, Exploration Mission-1. Additionally, four of the 10 segments for the flight test’s solid rocket boosters have been poured, and main engine test firings continue.

After this testing and assembly, a big moment for the SLS program will come during the fall of 2017. At that time, NASA plans a “hot fire test” of the full core stage at Stennis Space Center in southern Mississippi. During this test the core stage will be clamped down while a full thrust test of the launch system is performed. This test will go a long way toward proving that the large, 200-foot-tall core stage is ready for spaceflight.

Despite the concerns about costs and low-flight rate, Hill said NASA views the SLS rocket and Orion spacecraft as “foundational” to its efforts to press ahead with deep space exploration. And all things considered, he said NASA is doing well with the budgets the president and Congress have provided. “At the funding levels we have we’re doing a lot better than I expected,” he said.

Listing image by NASA