Failed test could further delay NASA’s SLS rocket

The January 16 “Green Run” test of NASA’s Space Launch System (SLS) was to be the last step before the super heavy transport thruster was moved to Cape Canaveral ahead of its inaugural Artemis I mission in November 2021. The total duration The static fire test was designed to simulate a typical launch, with the main rocket engines burning for approximately eight minutes at maximum power. But despite a thunderous start, the vehicle’s on-board systems triggered an automatic shutdown after just 67 seconds; making it the latest in a long line of disappointments surrounding the controversial booster.

When it was first offered in 2011, the SLS seemed so simple. Rather than spending the time and money to develop a brand new rocket, the super heavy thruster would be based on slightly modified versions of the Space Shuttle components. All the engineers had to do was attach four of the Orbiter’s RS-25 engines to the bottom of an enlarged external tank and attach a pair of solid rocket thrusters of the same aspect ratio. Instead of the intricate Winged Orbiter, the crew and cargo would ascend to the top of the rocket using an upper stage and capsule much like what was used in the Apollo program.

There are very few things that could be called “easy” when it comes to spaceflight, but SLS was certainly designed to take the path of least resistance. Using flight-proven components assembled at existing production facilities, NASA estimated that the first SLS could be ready for a test flight in 2016.

If all went according to plan, the agency expected it to be ready to send astronauts beyond low earth orbit by the early 2020s. Just in time to meet the lofty targets spelled out by President Obama in a 2010 address to the Kennedy Space Center, including crewed operation of a nearby asteroid by 2025 and a potential mission to Mars in the 2030s.

But of course, none of this ever happened. By the time SLS was scheduled to make its maiden flight in 2016, with nearly $ 10 billion already spent on the program, only a few structural test items had been assembled. Each year, NASA has pushed back the date for the booster’s first tune-up flight, as the project missed deadlines in 2017, 2018, 2019 and 2020. After the recent engine test, engineers were able to collect the necessary data. To ensure the vehicle could safely perform a full burn, outgoing NASA administrator Jim Bridenstine said it was too early to say if the booster would fly again this year.

What did not go well? As business entities like SpaceX and Blue Origin evolve in leaps and bounds, NASA seems stuck in the past. How did such a simple project get so late and over budget?

The rocket to nowhere

Perhaps the most pressing problem with the SLS program is that it lacks a clear objective. As a congressionally mandated project, NASA must continue to develop, whether or not it has a use for it. Critics have often referred to the program as the “Senate launch system” because they believe that the concept derived from the shuttle was conceived primarily as a way to ensure that the manufacturing facilities used to build the engines, tanks rocket propellants and solid rocket boosters for the Space Shuttle would remain in service even after the program’s withdrawal.

Without a clear mission for the SLS, it has been difficult for NASA engineers to develop long-term development plans. What payload should the booster carry, and where to, are key questions to be answered. NASA is no longer pursuing a mission to recover a near-Earth asteroid, and a human mission to Mars is decades away. SLS should initiate Europa Clipper to Jupiter in 2025, although the Falcon Heavy is already considered a backup if it isn’t ready on time.

While its ultimate effectiveness is questionable, the design of the space shuttle was driven by a very specific goal: to transport large objects to and from low earth orbit inside its cargo hold. Every decision made during the duration of the program revolved around this fundamental principle. Without similar guidance, the Space Launch System found itself adrift.

Simply put, the only defining characteristic of the SLS is the sheer mass it is able to put into space. The basic configuration of Block I of the rocket is designed to put 95,000 kg (209,000 lb) into low earth orbit, and the later version of Block II 130,000 kg (290,000 lb). But while these are impressive numbers, it’s not immediately clear what kind of mission architecture would require launching such massive modules in one fell swoop. The 50 years of experience gained since the Apollo era has taught us that modular systems, launched on competitively priced boosters and assembled in orbit, are the key to creating sustainable space infrastructure.

Wasted reusability

From the start, the space shuttle was designed to be almost completely reusable architecture. Aside from the external tank, every component in the system could be salvaged, refurbished and stolen again. The idea being that it would be cheaper and faster to reuse the same vehicle than to build a new one for each mission.

Unfortunately, the complexity and cost of the renovation process were greatly underestimated, in part due to the technical and material limitations of the time. In the end, the Shuttle has never been launched so affordably and quickly as its designers had hoped, but the lessons learned during the program have helped shape modern reusable spacecraft such as the Dream. Chaser of Sierra Nevada Corporation and the Boeing X-37B.

But despite the current trend towards reusable rockets and spacecraft, NASA is taking a step backwards with the SLS by using components that were designed to be refurbished and throwing them away at the end of every flight. The RS-25 engines installed on the first SLS rocket were not newly manufactured, they were literally the same engines that were taken out of the shuttle orbiters when they were placed in museums. The same is true with Solid Rocket Boosters (SRB); the new stretched boosters use segments of the original Shuttle SRBs, but instead of descending on parachutes to be retrieved, they will crash into the ocean and sink.

Each SLS flight will destroy four Shuttle-era RS-25 engines and two SRBs, just because they took up space in a NASA warehouse. From a historical point of view, it is odious. But more concretely, integrating these decades-old components into a modern launcher has proven to be much more difficult than expected. While they’ve seen improvements since the Shuttle’s retirement, it’s no exaggeration to say that some of the people working on the SLS today weren’t born when its engines were built.

Currently, NASA has only enough RS-25 engines from the Shuttle program to support four SLS flights. To solve this problem, the agency has already hired Aerojet Rocketdyne to produce a new version of the engine called the RS-25E, designed to be consumable. Unfortunately, these design changes come at a high price. Each RS-25E will cost NASA nearly $ 150 million, which is more than what SpaceX charges for a flight on the Falcon Heavy. With a price per launch that will easily exceed that of the infamously expensive space shuttle, it’s hard to imagine how SLS can possibly remain competitive with reusable commercial vehicles that are expected to start operating in the current decade, such as the SpaceX spacecraft and the New Glenn from Blue Origin.

A calculated risk

After reviewing the data, NASA said the automated shutdown during the Jan.16 engine test was due to intentionally conservative test limits meant to avoid unnecessary stress on the booster. During a press conference, Administrator Bridenstine said if it was an actual flight the engines would have continued to fire for as long as it takes to reach orbit. He went on to explain that there is an inherent risk if NASA or prime contractor Boeing decides to run the full duration test fire again, as the thruster tanks can only be filled and emptied in a limited number. of times.

Although nothing has been determined yet, these statements seem to indicate that NASA may decide not to repeat the test firing and continue the Artemis I mission to ensure it reaches the current November launch date. 2021. Conventional wisdom would say this is not wise, but since the first flight will have no human occupants, the space agency, usually risk averse, might be willing to roll the dice if that means it can. avoid another costly delay on a program it is already facing. fierce criticism.

On the other hand, broadcasting the explosion of their first Space Launch System rocket live to millions of viewers around the world will hardly improve matters. A catastrophic failure during Artemis I would also most likely cause a delay of the crewed Artemis II which is tentatively scheduled for August 2023. The resulting domino effect would likely make it almost impossible for NASA to make the already ambitious deadline to put the first woman. and the next man on the lunar surface by 2024.