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SpaceX begins testing first flightworthy Super Heavy booster
More than three months after the building-sized Starship booster’s latest return to Starbase’s orbital launch site, SpaceX has finally begun the process of testing what CEO Elon Musk says is still the first flightworthy Super Heavy.
After completing a number of pad tests in the days prior, SpaceX began filling Super Heavy Booster 4 (B4) with liquid nitrogen – supplied by the first orbital-class Starship launch – for the first time on December 17th. It’s unclear exactly what was done during the test but regardless of what transpired, the test and B4’s survival were a major, long-awaited milestone for both the Starship booster and the orbital launch site (OLS).
At this point in time, the general consensus among close followers of SpaceX’s Starship program is that the unprecedented amount of time it’s taken the company to complete Booster 4’s first test was not because of the rocket itself but rather because the orbital launch site needed to fully test it had yet to be completed. While it was SpaceX’s choice to not perform some kind of initial testing with B4 at one of the site’s two suborbital test and launch mounts, it’s clear that the company ultimately concluded that Super Heavy Booster 3’s successful July 2021 tests – including a cryogenic proof virtually identical to Booster 4’s first test – made such partial testing redundant.
Put a different way, SpaceX must already be confident enough in the quality of the first few Super Heavies rolling out of its Starbase factory to deem it unnecessary to verify the structural integrity of the first truly completed Super Heavy booster before putting the one and only orbital Starship launch site directly in the line of fire. Nonetheless, depending on how far Super Heavy Booster 4’s first cryogenic proof test went, it appears that SpaceX’s presumptions were correct.
On December 17th, SpaceX subjected Super Heavy B4 to a cryogenic proof test about twice as ambitious as B3’s, filling the booster maybe a sixth of the way with a few hundred tons of liquid nitrogen (LN2). What isn’t clear is if that test also raised the booster’s propellant tanks to flight pressures (6-8 bar or 90-115 psi). If Booster 4 did reach those pressures, the test is even more significant – partially proving that the rocket is ready for flight. On December 21st, SpaceX performed a similar series of cryogenic tests, again partially filling Booster 4 with about the same amount of liquid nitrogen but doing so two or three times in a row. Again, the Super Heavy survived the several-hour ordeal without any obvious issues. Still, a number of additional tests – some even more important – are still in front of SpaceX and Super Heavy B4.
The most obvious is simple enough: SpaceX needs to fully fill a Super Heavy booster for the first time. Depending on the storage situation, that process will likely begin by filling Booster 4 with about 2500 tons (5.5M lb) of liquid nitrogen (LN2) – about two-thirds full. If SpaceX also temporarily fills one of the orbital tank farm’s liquid oxygen (LOx) or methane (LCH4) tanks with nitrogen, it could fully load Booster 4 with around 3500 tons (7.7M lb) of nitrogen. At least according to SpaceX’s own website, that’s about the same weight as the propellant (3400t/7.5M lb) Super Heavy is designed to lift off with. If that full cryoproof goes well, SpaceX will then likely perform one or several wet dress rehearsals, ultimately filling Booster 4 with approximately 2900 tons (6.4M lb) of cryogenic oxygen and 500 tons (1.1M lb) of cryogenic methane.
Finally, SpaceX will probably kick off static fire testing, likely beginning by igniting just one or a few of Super Heavy’s many engines. Eventually, that process could culminate in the ignition of all 29 of Booster 4’s Raptors, briefly producing a bit less than 5400 tons (~11.9M lbf) of thrust – 50% more powerful than NASA’s retired Saturn V Moon rocket.
According to Elon Musk, despite a number of recent signs and reports to the contrary, SpaceX still intends to fly Booster 4 and Ship 20 on Starship’s first orbital-velocity launch attempt, so the scope and scale of testing are only likely to grow over the next several weeks.
Elon Musk
Elon Musk gives his most telling Tesla-SpaceX merger conversation yet
Elon Musk hinted a Tesla-SpaceX merger could be coming, and Wall Street is taking notice.
Elon Musk gave his clearest signal yet that Tesla and SpaceX could eventually combine, telling the All-In Summit in Los Angeles that the two companies’ deepening collaboration makes the question worth asking. Sawyer Merritt first surfaced the highlight on X Tuesday.
Asked directly why Tesla and SpaceX remain separate given how closely they already work together, Musk told hosts at the summit: “Great question there. With all this collaboration, on so many levels, who can imagine what action one might take when there’s so much close collaboration in so many areas.” SpaceX President Gwynne Shotwell, who joined Musk on stage, added that SpaceX personnel have already moved into xAI to fill leadership and engineering gaps, saying the businesses are integrating “faster than I thought,” though “not fully integrated yet,”
The comments landed on top of merger speculation that has been building on Wall Street for months. JPMorgan has called a tie-up “strategically coherent on paper,” pointing to overlapping ambitions in AI, robotics, energy, transportation and space. Jefferies went further, estimating Musk could retain roughly 55.3 percent voting control in a deal structured without a premium, a scenario that would still leave room for Tesla shareholders to come out ahead. On Kalshi, traders now put the odds of a merger before 2028 at 66 percent.
Tesla’s stake in SpaceX, still under one percent, traces back to its earlier investment in xAI, which converted to SpaceX equity after SpaceX absorbed the AI company. The two are also jointly building Terafab, a chip facility in Austin meant to serve both Tesla’s AI computing needs and SpaceX’s satellite ambitions. Wedbush analyst Dan Ives has stood by a 2027 merger timeline for months, and Cathie Wood’s ARK Invest recently floated a similar case, an idea Musk pushed back on directly at the time.
Another Tesla SpaceX merger prediction by ARK Invest has Elon Musk talking
The timing adds another layer. Tesla has scheduled an October 1 unveiling for its next generation Roadster at a venue near SpaceX’s McGregor, Texas test site, using the phrase “Go for launch” in its promotional material. Both stocks dipped roughly 2 percent Monday before recovering slightly in premarket trading Tuesday, with SpaceX shares up about 0.4 percent and Tesla essentially flat.
Musk stopped short of confirming anything is in motion. But unlike his past denials of a corporate restructuring, this response didn’t rule one out, and it came with Shotwell sitting next to him describing an integration that’s already underway.
The Tesla Roadster unveiling is getting hyped up by the company’s CEO Elon Musk, who has been a big reason the product has such high expectations due to delayed timelines and a constant need to make it even more insane than before.
Tesla announced on September 12 that it would officially unveil the Roadster in Waco, Texas, on October 1, ending years of patience for fans and reservation holders who have waited for the all-electric supercar to enter production since 2017.
Musk has said that this event will be well worth the wait on several occasions, and last year on the Joe Rogan Experience, he said that there should be a closing chapter to supercars- the end of cars that aren’t focused on safety.
He said:
“Whether it’s good or bad, it will be unforgettable. My friend Peter Thiel once reflected that the future was supposed to have flying cars, but we don’t have flying cars. I think if Peter wants a flying car, he should be able to buy one. I think it has a shot at being the most memorable product unveil ever. This is some crazy technology in this car. Let’s just put it this way: if you took all the James Bond cars and combined them, it’s crazier than that.”
Musk’s teases have continued, and now that the event is roughly two weeks away, it seems like Roadster is finally going to show up and blow some minds:
It’s out of this world
— Elon Musk (@elonmusk) September 13, 2026
Excitement guaranteed
— Elon Musk (@elonmusk) September 13, 2026
Tesla has definitely dragged out the development of the Roadster, but there is a good reason for it.
Tesla has been working on many other projects, most notably self-driving efforts to increase passenger safety, and those simply took priority over the Roadster, a low-volume, high-performance sports car that has a lightning-fast acceleration rate of 0-60 MPH in just 1.1 seconds, could potentially fly, and contributes very little to the company’s mission.
However, many people have the Roadster on pre-order through the referral program or with their own money, and it is time that Tesla delivers on that.
Elon Musk
Elon Musk’s Boring Company has big plans for Las Vegas by year’s end
Elon Musk’s Boring Company says Vegas Loop stations will double by year end once again.
The Boring Company says the Vegas Loop’s station count will double by the end of the year, tying the target to a hiring push for drivers and operations managers in Las Vegas. “Vegas Loop is getting bigger – the station count will double by end of year!” the company wrote in a post on X, attaching listings for a Loop driver and a senior Loop operations manager.
The number checks out against what’s already public, with the Vegas Loop currently running 14 operational stations, while the Boring Company’s own project page lists 28 as the target for the end of 2026.
Vegas Loop is getting bigger – the station count will double by end of year!
Urgently hiring exceptional and enthusiastic Drivers and Ops Managers.
Apply here!
Driverhttps://t.co/ZUPXBYTONb
Senior Loop Ops Managerhttps://t.co/mV6V22V8jH pic.twitter.com/IZ9FqIw8WY
— The Boring Company (@boringcompany) September 14, 2026
Much of that growth is tied to tunnels that are already built and waiting on an opening date. A roughly two-mile dual tunnel system under Paradise Road, connecting Westgate to a planned station at 4744 Paradise Road, is expected to open in stages over the coming weeks, Las Vegas Convention and Visitors Authority chief executive Steve Hill told the Review-Journal last week. New stations at 4744 Paradise, Virgin Hotels Las Vegas, and the former Gordon Biersch site would come online with it, several of them built to speed up rides to Harry Reid International Airport ahead of Formula 1’s Las Vegas Grand Prix.
Clark County entitled Vegas Loop for 123 stations after approving 19 more in August, as Teslarati reported at the time. Entitlement and construction move at different speeds on this project, so county approval alone does not guarantee a station opens on any particular schedule.
Clark County approved 18 additional stations back in 2023, part of a plan that pushed the system’s target to 69 stations across 65 miles, doubling the network on paper for the first time. The target kept climbing after that, to roughly 93 stations by the end of that year and 104 by last year, before August’s vote pushed it to 123. This week’s announcement is the first time that doubling language has been attached to stations actually running rather than stations merely approved on a county map.
Ridership gives some sense of what a denser network could carry. Boring Company executive Mike Baier said in July that the Vegas Loop already moves around 40,000 passengers on busy convention days, a total that tops most light rail systems in the country despite the system running on a fraction of its planned tunnel mileage. Company leadership has projected ridership could triple or quadruple once the airport connector tunnels fully open.
Boring Company did not say which stations beyond those already under construction would open by year end, or whether the hiring push points to a fleet expansion alongside the new stops.
Elon Musk gives his most telling Tesla-SpaceX merger conversation yet
Tesla Roadster unveiling is getting hyped up by Elon Musk
