NASA has spent years and billions of dollars developing a giant rocket known as the Space Launch System, designed to take astronauts to moon and perhaps farther out into the solar system someday. But the first launch of the rocket — an uncrewed test flight that will go to the moon and beyond — will not get off the ground until at least November.

This Saturday, though, NASA is scheduled to put on a fiery show as it performs a crucial test: igniting all four engines of the booster stage for up to eight minutes, simulating what would occur during an actual launch to orbit. The booster, however, will remain securely held down at a test stand at NASA’s Stennis Space Center in Mississippi.

The test fire was scheduled for Saturday at 4 p.m. Eastern time, but has been briefly delayed. NASA said there is a two-hour long window during which the test could occur.

NASA Television has started broadcasting coverage of the test, or you can watch it in the video player embedded above.

The ignition of the booster was planned for 5 p.m. originally, but the agency shifted the schedule forward by one hour, saying after it had loaded the rocket with propellant that preparation was ahead by one hour.

However, Alex Cagnola, a NASA engineer, referred to a delay of the current time frame, saying that the test conductors were “working through a few issues on the stand,” without describing the cause of the delay or how long it would last.

A news conference is scheduled to follow about two hours after the test.

A solid rocket booster inside the Kennedy Space Center’s Rotation, Processing and Surge Facility at Cape Canaveral, Fla., this summer.
Credit…Ben Smegelsky/NASA

The Space Launch System is the 21st-century equivalent of the Saturn V that took NASA astronauts to the moon in the 1960s and 1970s. Although there are many other rockets available today, they are too small to launch spacecraft that can carry people to the moon. (A possible exception is SpaceX’s Falcon Heavy, but a human lunar mission would require two separate launches carrying pieces that would then dock together in space or head separately to the moon.)

The Falcon Heavy can lift up to 64 metric tons to low-Earth orbit. The initial version of the S.L.S. is a bit more powerful, capable of lifting 70 metric tons, and future versions of the rocket will be able to loft up to 130 metric tons, more than the rockets that carried the Apollo astronauts to the moon.

Although the Space Launch System will be expensive — up to $2 billion a launch for a rocket that can be used only once — Congress has provided steadfast financial support for it so far. Supporters maintain that it is important for the government to own and operate its own powerful deep-space rocket, and pieces of the system are built by companies across the country, spreading the economic benefits to many states and congressional districts.

The Space Launch System is a key component for Artemis, the program to take NASA astronauts back to the moon in the coming years. Although President Trump pledged to make the trip by the end of 2024, few expected that NASA would actually meet that timeline, even before President-elect Joseph R. Biden Jr. was elected.

When NASA announced its plans for the Space Launch System in 2011, the first launch was scheduled for 2016. As is typical for new rocket designs, the development ran into technical difficulties, such as the need to develop procedures for welding together pieces of metal as large as those in the rocket. NASA also paused work on the rocket for a time last year during the early stages of coronavirus outbreak.

As the date of the first launch slipped several times, the price tag rose. NASA has so far spent more than $10 billion on the rocket and more than $16 billion on the Orion capsule where the astronauts will sit.

In an audit in 2018, NASA’s inspector general blamed poor performance by Boeing, the main contractor building the booster stage, for much of the delay. Another report by the inspector general in 2020 said NASA “continues to struggle managing SLS program costs and schedule.”

The Space Launch System’s liquid hydrogen tank was loaded onto a test stand at the Marshall Space Flight Center in Huntsville, Ala., in January 2019.
Credit…Tyler Martin/NASA

The test fire is part of what NASA calls the green run, a series of tests of the fully assembled booster stage. The same booster will be used for the first flight to space, so engineers want to ensure that it is working as designed before launching it.

Just as with a real launch, technical glitches occur. In an earlier test, known as a wet dress rehearsal, in which the entire countdown was simulated except for igniting the engines, almost everything went well. But in the last few seconds, one of the propellant valves did not close as soon as expected. It turned out that the temperature was a bit lower than predicted, and that made the valve a bit harder to turn. The software has since been adjusted.

A worst case would be if a malfunction led to destruction of the booster. That would add years of delay to the program and renew calls for NASA to consider alternatives.

Several other rockets are under development, and some may be close to their first trips to space.

The United Launch Alliance, a joint venture between Boeing and Lockheed Martin, may launch its Vulcan Centaur in the fourth quarter of the year. The Vulcan Centaur is the successor to Atlas V, a longtime workhorse for launching military and NASA satellites. However, that rocket uses the Russian-built RD-180 engines, and Congress has grown increasingly leery of relying on technology from a country that is often considered an adversary.

Blue Origin, the rocket company started by Jeff Bezos, the billionaire founder of Amazon, has also been developing a reusable rocket called New Glenn that would compete with both Vulcan Centaur and SpaceX’s Falcon 9 rockets. (Blue Origin will also earn money from each Vulcan Centaur launch; that booster uses BE-4 engines made by Blue Origin.)

Most intriguing is the gigantic Starship rocket under development by Elon Musk’s SpaceX. When mounted on top of a huge booster stage, it would dwarf the Space Launch System, yet would be entirely reusable like a passenger jet. It is designed to take people to Mars, and SpaceX has also won a contract to adapt it for taking NASA astronauts to the surface of the moon.


During Wednesday’s test flight of the SpaceX Starship prototype, a rocket Elon Musk envisions ferrying humans to Mars, it launched into the sky but glided back to Earth before it exploded while attempting to land.CreditCredit…By Reuters

Mr. Musk’s engineers have been conducting atmospheric test flights of Starship prototypes at a site in South Texas along the Gulf Coast. During the most recent test, which was livestreamed on the internet, the prototype rocket accomplished a number of technical goals before coming down too fast during its landing and exploding in a spectacular blast. The company appears to be preparing for its next test flight in the days or weeks to come.

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