Watch SpaceX try launching a new Starship rocket 6 miles above Texas on Tuesday

• SpaceX is poised to fly the SN9 prototype of its Starship rocket system six miles above south Texas on Tuesday, with a backup launch window on Wednesday.
• Elon Musk publicly blasted the FAA for refusing to approve this flight last week. The agency cited "outstanding safety issues."
• SpaceX's last attempt, which ended with an explosion, violated the company's launch license and triggered an FAA investigation.
• Watch live video feeds of the SN9 launch attempt below.

Update: Although SpaceX's Starship SN9 prototype successfully launched to 10 kilometers (6.2 miles), the rocket exploded upon landing. Read our full coverage here.

SpaceX is set to launch a new prototype of its Starship rocket ship six miles above south Texas on Tuesday, according to government notices.

The launch attempt follows a public quarrel between Elon Musk the Federal Aviation Administration over regulatory roadblocks last week, and a reported investigation into SpaceX violating its launch license.

The tricky launch involves the 16-story rocket soaring to 10 kilometers (6.2 miles), belly-flopping toward the ground, reigniting its three Raptor engines, and turning upright just before touching down on a landing pad. If successful, the flight would be the highest and most ambitious yet for a Starship vehicle.

Musk, who founded SpaceX in 2002, wants the final Starship-Super Heavy launch system - which may stand 120 meters (394 feet) tall - to be fully reusable. If it works, Starship might slash the cost of reaching space about 1,000-fold, power round-the-world hypersonic travel on Earth, and fly astronauts to the moon. Musk's ultimate plan is to build 1,000 Starships, use them to fly people and cargo to Mars, and build an independent, self-sustaining city there.

SpaceX first launched a Starship prototype of this kind in early December. Called Starship serial No. 8, or SN8, it roared tens of thousands of feet above the company's facilities in Boca Chica, Texas. As SN8 neared the ground in a belly-flop-like freefall, it re-fired its engines to flip upright and slow its descent. However, low pressure in a propellant tank caused the spaceship to fall too fast, slam into its landing pad, and explode.

SpaceX considered the seven-minute test flight a success because it was an experiment. The vehicle flew higher than ever before and performed unprecedented maneuvers like sequential engine shutdowns and aerial flips; prior test flights had been "hops" of a few hundred feet.

The goal with launching the new prototype, SN9, is to land the rocket in one piece.

Watch SN9's launch attempt live on YouTube

The FAA has issued an airspace closure notice over Boca Chica for Tuesday from 8 a.m. to 5 p.m. CST. A judge in Cameron County, Texas, also issued road-closure notices for Boca Chica - another necessary prerequisite for a launch attempt - for Tuesday from 9 a.m. to 6 p.m. CST.

SpaceX began a live broadcast of the attempt live on YouTube at about 2:20 p.m. CST, after loading propellant into the rocket's engines:

Fans of the company are also on the ground and streaming their own live video of the launch site. An added bonus: SpaceX rolled out an even newer prototype, the SN10, last week. Broadcasts show the two Starships standing side by side.

We recommend starting with NASASpaceflight's video stream, given the broadcasters' knowledge and multiple quality camera views.

LabPadre also offers live commentary of launch attempts, along with six unique views of the Starship launch site. Below is the channel's main 4K-resolution feed.

For a more distant view of the launch site - broadcast from the top of a hotel resort in South Padre Island about 6 miles away - check out SPadre's 24-hour live feed.

A series of events typically precedes a Starship prototype launch. A couple of hours beforehand, SpaceX will clear the launch site of personnel. Roughly an hour ahead of the flight, storage tanks at the launch site will begin venting gases as SpaceX prepares to fuel Starship with cryogenic fuels. That fueling later causes Starship to vent gases out of its top, a signal that launch could occur within minutes.

However, poor weather, a technical glitch, or a boat that gets within the launch's danger zone - a new challenge for Starship - could lead to further delays. The FAA and the Cameron County judge have also issued such notices for Wednesday in case of a delay.

SpaceX violated its launch license, triggering SN9 delays

The SN8 flight violated the terms of SpaceX's launch license with the FAA, Joey Roulette of The Verge first reported on Friday.

In a statement emailed to Insider on Tuesday, an FAA spokesperson indicated that the SN8 flight did not adhere to federal safety standards. Prior to the launch, "SpaceX sought a waiver to exceed the maximum public risk allowed by federal safety regulations. After the FAA denied the request, SpaceX proceeded with the flight," the spokesperson said.

"As a result of this non-compliance, the FAA required SpaceX to conduct an investigation of the incident. All testing that could affect public safety at the Boca Chica, Texas, launch site was suspended until the investigation was completed and the FAA approved the company's corrective actions to protect public safety."

That investigation seems to be the reason the regulatory agency scrubbed SpaceX's planned launch last week. Now, the spokesperson said, "corrective actions" from the SN8 incident have been incorporated into a launch license for SN9.

"The FAA determined late Monday (Feb.1 ) that SpaceX complies with all safety and related federal regulations and is authorized to conduct Starship SN9 flight operations in accordance with its launch license," the spokesperson said.

That set up SpaceX to attempt a launch of the prototype on Tuesday. It's not clear what caused SpaceX to exceed the FAA's public-risk regulations with SN8 or what the corrective actions were for SN9.

The FAA wouldn't approve an SN9 launch last week due to 'safety issues'

Launching and landing Starships without damaging them will be key to Musk's vision of making the launch system fully and rapidly reusable. Unlike SN8, the SN9 test flight could stick the landing.

The company announced its intention to make that attempt on Thursday, and workers prepared to remotely load propellant into the rocket's fuel tanks. But as the day progressed, it became clear that the FAA had not given SpaceX approval to launch. The agency yanked its airspace closure - a requirement for launch - and issued an advisory that the flight attempt was officially scrubbed.

Musk vented on Twitter in response.

"Unlike its aircraft division, which is fine, the FAA space division has a fundamentally broken regulatory structure," he wrote Thursday afternoon. "Their rules are meant for a handful of expendable launches per year from a few government facilities. Under those rules, humanity will never get to Mars." (The agency recently streamlined its rocket-launch rules, though that policy shift is not set to take effect until later this year.)

SpaceX began to load liquid fuel onto the rocket, possibly hoping to obtain approval by the time the engines were ready to roar. But the FAA did not budge, and SpaceX unloaded the fuel as its launch window closed.

"We will continue working with SpaceX to resolve outstanding safety issues before we approve the next test flight," an FAA spokesperson said in a statement emailed to Insider.

The next day, the agency issued a more detailed statement. It seems to indicate that the agency was still evaluating updates to SpaceX's launch license that resulted from the SN8 investigation.

"The FAA will continue to work with SpaceX to evaluate additional information provided by the company as part of its application to modify its launch license," the FAA spokesperson said on Friday. "While we recognize the importance of moving quickly to foster growth and innovation in commercial space, the FAA will not compromise its responsibility to protect public safety. We will approve the modification only after we are satisfied that SpaceX has taken the necessary steps to comply with regulatory requirements."

It's still unclear what those modifications are. Musk tweeted early on Tuesday that he would be "off Twitter for a while."

This post has been updated with new information. It was originally published on January 15, 2021.