Early Wednesday (Nov. 16) morning, NASA finally launched its powerful Space Launch System (SLS) rocket, a key milestone in the planned Artemis program to return humans to the moon.
This was the fourth attempt to launch the 322-foot-tall (98 meters) rocket, which was initially supposed to take off on Aug. 29, then again on Sept. 3, and once more on Sept. 27, but each time the agency faced disruptions that stopped the launch.
So, why was the most powerful rocket ever built so plagued with setbacks and delays?
"We can forget sometimes that this is the first launch of a brand new system. So every time we do this, we're learning about how to launch a brand new rocket," Jake Bleacher, chief exploration scientist in the Human Exploration and Operations Mission Directorate at NASA headquarters, told Live Science.
Why do rocket launches get delayed?
Rocket launch delays are extremely common. A planned launch can be scrubbed for dozens of reasons, ranging from adverse weather to technical malfunctions to last-minute obstructions in the rocket's flight path. NASA's SLS launch has been no exception.
On Aug. 29, mission engineers scrubbed the launch because of lightning. NASA's weather criteria are strict. Before even making it to the launchpad, there must be no lightning within 20 nautical miles (that's about 23 miles, or 37 kilometers), no more than a 5% chance of hail, no wind exceeding speeds of 46 mph (74 km/h), or if the temperature is lower than 40 degrees Fahrenheit (4 degrees Celsius) or higher than 95 F (35 C). While on the launchpad, the rocket cannot launch if there are any thunderstorms or lightning sighted in the area.
On Sept. 3, the launch was scrubbed because of a leak in a line that fed liquid hydrogen into the rocket. SLS depends on four RS-25 engines fueled by liquid hydrogen and oxygen. When that propellant is ignited at liftoff, the hydrogen and oxygen react to form water — explosively. Water vapor shoots out of the engine nozzles at 10,000 mph (16,093 km/h) and helps provide enough thrust to send the rocket to space.
NASA's next opportunity to launch would have been Sept. 27, but mother nature had different ideas. The mission team decided to roll the rocket back into the Vehicle Assembly building on Sept. 26, just two days before Hurricane Ian wreaked havoc on Florida's southwestern coast. Another hurricane, this time named Nicole, disrupted launch plans for Nov. 14.
Is delaying a rocket launch a problem?
Even if Wednesday's launch had been scrubbed, NASA would have still had more opportunities to launch Artemis. Every month, there are "a number of opportunities over a two-plus week period of time, where we can [launch] most of those days during that time period," Bleacher said.
But delays shouldn't be seen as all bad, Bleacher noted. "[A] scrub is not bad. It's us reacting to something that needs to be addressed. And it ensures that we have the opportunity to launch this rocket."
With every delay, whether it's due to a mechanical problem or mother nature, means the team can learn more about launching a rocket.
"The one thing that absolutely has to be true is we have to get it right," Bleacher said.
Now successfully launched, NASA's SLS rocket is carrying the Orion capsule (uncrewed for now, except for its manikin astronauts, or "moonikins") into space toward a lunar orbit. It is also carrying a handful of CubeSat satellites designed for various scientific investigations, such as studying the lunar surface or deep space radiation. Orion will travel to and orbit the moon for about two and a half weeks before returning to Earth.
Future missions in the Artemis program will see humans ride the Orion capsule to the moon, and touch down on its surface for the first time since 1972.