NASA has continued to make progress with the development of its large Space Launch System (SLS) rocket as work continued on its critical core stage throughout the partial government shutdown, and the agency is nearing critical hardware tests. However, it now seems all but certain that NASA will miss its latest launch date for the first flight of the rocket, June 2020.

Multiple sources have told Ars that while NASA is still targeting sometime later in 2020 for a test launch of the SLS rocket and Orion spacecraft, known as Exploration Mission-1, this flight is likely to slip into 2021.

This week, in response to a query about potential delays, a spokeswoman for the agency's exploration program, Kathryn Hambleton, said the agency is not ready to discuss a new schedule yet. "NASA is still assessing impacts as a result of the shutdown, but we are still working toward a launch in 2020," she told Ars.

Hardware moving

The core stage of the rocket, consisting of a large, liquid hydrogen fuel tank, a smaller but still considerable liquid oxygen tank, and four main engines, is coming together. In January, the agency installed the large liquid hydrogen tank onto a test stand at Marshall Space Flight Center in Huntsville, Alabama for a "structural test." This tank, identical to one that will be used during a mission, will be subjected to the same stresses and loads it will endure during liftoff and flight.

Following this step, the agency will perform a similar structural test of the liquid oxygen fuel tank before what is known as a "green run" test. For this exercise, NASA will assemble the two large tanks and then integrate them with the rocket's four main RS-25 engines. Then, at a test stand in southern Mississippi, the rocket will fire its engines through a standard launch of the rocket.

NASA/Steven Seipel

NASA

NASA

NASA

NASA

NASA

NASA has yet to formally set a date for this "green run" test, but whenever it does occur will be a key indicator for when we will see the first actual launch of the SLS rocket. If the green run test is conducted late in 2019, there would still be a chance for a 2020 launch. However, the agency and its prime contractor for the core stage, Boeing, are on a tight timeline that has little margin for technical problems that might occur during the structural tests of the tank or the green run tests. Historically, during this integration and test process with other large rocket programs, major problems have often occurred.

It is not clear how deeply the shutdown affected the SLS timeline, even though core stage work did proceed. "The shutdown impacted at least day for day," one source said of the schedule. "But I am sure it was more than that."

NASA originally planned to launch the SLS rocket on its maiden flight in November 2017, so the rocket will now be at least three years later than originally anticipated. The program's budget is more than $2 billion a year, so these delays have cost the agency considerably.

Upper stage concerns

This week, NASA also confirmed that it has ordered three Interim Cryogenic Propulsion Stages from United Launch Alliance. Originally, NASA had planned to use this placeholder upper stage for its SLS rocket for a single flight. But now it will almost certainly use the ICPS stage for at least three flights, if not several more. This raises questions about the viability of the agency's plan to have Boeing build a more powerful second stage, known as the Exploration Upper Stage.

Hambleton told Ars, "NASA has placed orders for three ICPS’ to use on SLS Block 1 for the first three flights, which currently include the first test flight of SLS and Orion (Exploration Mission-1), the first crewed flight (Exploration Mission-2), and the Europa Clipper mission."

There is some flexibility to this, however. As Ars has previously reported, NASA is seriously considering using the Falcon Heavy rocket with a Star 48 kick stage for the Europa Clipper mission. That could push the agency toward using the ICPS for a third exploration mission, which presently is scheduled to begin construction of a Lunar Gateway near the Moon.

Meanwhile, work by Boeing and NASA on the Exploration Upper Stage has slowed. This is partly because the agency is looking at alternative designs to bring Boeing's projected cost of the stage down. Ars has also learned that NASA is looking at potential scenarios in which it constructs the Gateway with the initial Block 1 configuration of the SLS rocket with the ICPS upper stage because the more powerful upper stage will not be ready in time.

Publicly, at least, NASA has not changed its posture on the more powerful upper stage. In an interview late in 2018, NASA Administrator Jim Bridenstine acknowledged that the agency is focused on core stage development now rather than the Exploration Upper Stage. "We have closer alligators to the canoe right now, and that would include the core stage." But he said NASA remains committed to the Exploration Upper Stage, calling it a "critical component."

Priorities

In his State of the Union speech on Tuesday night, President Trump mentioned the forthcoming 50th anniversary of the Apollo 11 Moon landings, and he also gave a nod to the commercial crew program, which may launch humans from Florida late this year. However, Trump did not mention his own return-to-the-Moon plans or the rocket NASA says it needs to carry this out.

"It is somewhat surprising that Trump did not use the occasion tonight to point to his own initiative with at least a phrase if not an entire sentence," Marcia Smith noted on her website, Space Policy Online. "The omission may portend a constrained FY2020 budget request for NASA’s human spaceflight program." An outline of the president's budget is expected March 11.

However, if NASA is to bring the SLS to the launch pad in late 2020, it will probably need more money for the program, not less. A report by NASA's inspector general critical of Boeing's management of the SLS project, published last October, warned of a funding crunch. The report found that NASA would probably need an additional $1 billion on top of its existing funds to complete the rocket by next year.