Video: Latest NASA test of Moon-bound rocket core ends abruptly, confusing scientists

We have ignition... but that was about it. On Saturday, January 16, NASA fired the engines of the rocket that will return humans to the Moon — albeit for a far briefer time than expected.

Supposed to last eight minutes, the fire only burned for a little over one minute.

The hot fire, which started at 5:27 p.m. Eastern, was the first time NASA had fired all four of the Space Launch System core stage's RS-25 engines at the same time. The test is the last in a year-long series of eight trials dubbed the "Green Run." But unfortunately for the space agency, the test did not go according to plan.

Why it matters — The test is an important step in NASA's human spaceflight plans. The Space Launch System will support the Artemis program, which aims to send the next man and first woman to the Moon as early as 2024. This deadline was described in a September 2020 document as "the most ambitious date possible."

Without a functioning Space Launch System, that date gets harder to meet. So every test on the road to getting a crewed mission going matters.

What they did — NASA's latest Space Launch System test brings the agency's goal a little closer. The test took place at the Stennis Space Center, located near Bay St. Louis, Mississippi. The core stage, which measures 212 feet tall, was stationed in the B-2 Test Stand. It's the tallest rocket stage the agency has ever built, capable of holding 733,000 gallons of liquid hydrogen and oxygen to power the engines.

The team ensured the rocket had 330,000 gallons of water per minute during the test, plus necessary power and gases. The test was expected to last just over eight minutes — enough time to send the rocket to space during a real launch. But the engines shut off after just over a minute, and the reasons why were not immediately obvious.

Watch the test in action below:

Here's the background — The core stage is designed to support every configuration of the Space Launch System. This four-engine stage generates 1.6 million pounds of thrust at liftoff. The core is paired with two solid rocket boosters on the sides.

The initial Block 1 variant will generate 8.8 million pounds of thrust in total — more than SpaceX's Falcon Heavy, which was billed as the world's most powerful operational rocket when it first launched in February 2018. It's able to launch up to 27 metric tons, or 59,500 pounds, to orbits beyond the moon.

A slightly more powerful Block 1B variant will be able to send the Orion spacecraft to the Moon alongside crew and cargo, ideal for a more sustained human presence on the Moon. It's able to launch up to 38 metric tons, or 83,700 pounds to deep space.

Another variant, Block 2, will offer 9.5 million pounds of thrust at liftoff. That vehicle will be able to send 46 metric tons, or 101,400 pounds, to deep space.

At the core of all of these, as the name suggests, is the core stage.

What's next — Paramount for NASA to move forward, the team now plans to evaluate the test data to understand what exactly happened. But ultimately, this was a big step for the agency, even if it didn't go off quite as planned.

“Seeing all four engines ignite for the first time during the core stage hot fire test was a big milestone for the Space Launch System team” John Honeycutt, the SLS program manager at NASA’s Marshall Space Flight Center in Huntsville, Alabama, said in a statement.

“We will analyze the data, and what we learned from today’s test will help us plan the right path forward for verifying this new core stage is ready for flight on the Artemis I mission.”

The Inverse analysis — As of Tuesday morning, NASA officials had not yet revealed exactly why the test was so short.

Comments from NASA program manager John Honeycutt in a post-test conference said the team saw "a little bit of a flash" from near the interface on engine four, hinting at a source for the problem.

At a January 12 press conference, SLS program manager at Boeing John Shannon claimed the team would get enough data to move on to next steps after some 250 seconds of firing, or around four minutes. Despite missing the target, NASA administrator Jim Bridenstine claimed at a post-test event NASA may still be able to meet its launch deadlines — if the fix is relatively straightforward.

One small stumble for NASA... The giant leap may have to wait.