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SpaceX’s Starship Raptor Vacuum engine plans laid out by CEO Elon Musk

A 2016 render of Raptor Vacuum. Much has changed about the engine's design in the three years since, but SpaceX is still pursuing a vacuum variant. (SpaceX)

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Elon Musk says that SpaceX Starship engine upgrades are on track to begin static fire tests of a Raptor Vacuum variant as few as a “couple months” from now.

Designed to enable more efficient performance in thin atmosphere or vacuum, Musk admitted that the first version(s) of Raptor Vacuum (RVac) will likely be a compromise between efficiency and speed of development. Nevertheless, the faster SpaceX can prepare Raptor Vacuum for flight, the easier it will be for Starship to begin serious (sub)orbital flight tests.

As it turns out, SpaceX’s first and only official render of Raptor – published in September 2016 – showed the engine’s vacuum-optimized variant. In the years since, CEO Elon Musk has vacillated between keeping the vacuum engines as a central Starship feature and simply replacing them with regular sea level Raptors to expedite the spacecraft’s debut. The 2016 and 2017 vehicles featured a mixture of vacuum and sea-level engines, whereas Musk revealed a vehicle with sea-level engines only in 2018.

Known as the Interplanetary Transport System in 2016, the ship featured six vacuum Raptors and 3 SL engines. (SpaceX)
In 2017, Big Falcon Spaceship shrunk and changed to 4 x RVac and 3x x Raptor SL engines. (SpaceX)
In 2018, Musk decided to sidestep vacuum engines entirely, moving to 7 SL Raptors. (SpaceX)

Perhaps less than a month after Musk’s September 2018 presentation, the SpaceX CEO made the decision to radically redesign the vehicle – newly christened Starship and Super Heavy – by moving from a carbon composite aerostructure to stainless steel. At first, the seven SL Raptors remained a part of the design, but Musk took to Twitter in 2019 to indicate that SpaceX had changed gears again and had reprioritized Raptor Vacuum development.

This came as a bit of surprise and it should go without saying that there’s a significant chance that Musk/SpaceX will oscillate in the opposite direction once again before Raptor Vacuum is actually ready for flight. This time, though, Musk has sketched out a development schedule and strategy that suggests SpaceX is much more serious this time.

Most notably, Musk claims that the first Raptor Vacuum prototype could be ready for static fire testing just a “couple months” from now, an immensely ambitious schedule for any large liquid rocket engine development program. Nevertheless, Musk did indicate that the “V1.0” Raptor Vacuum design would be significantly compromised and “suboptimal”, an intentional decision to prioritize the engine’s “speed of development”.

Even then, Musk believes that the first variant – featuring a shortened bell nozzle – could still be up to 12% more efficient than sea level Raptors and thus already 70-80% of the way to the physical limit of methane-oxygen rocket efficiency.

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A sea-level Raptor engine is static-fired at SpaceX’s McGregor, TX test facilities. (SpaceX)

On a positive note, shrinking V1.0 Raptor Vacuum’s nozzle a bit from its nominal length will likely mean that SpaceX can static fire fully-integrated engines at its McGregor, TX test facilities, critical for speedy development. If not, the company has experience with alternatives through Merlin Vacuum, which can only be tested on the ground with its lengthy nozzle detached. This method just makes it dramatically harder to optimize a vacuum nozzle design, as full-scale, flight-like testing is nearly impossible if a given vacuum engine can’t be tested on the ground with said nozzle installed.

Vacuum engines need such large and unwieldy nozzles in order to make them as efficient as possible. In a very simplistic sense, a rocket engine nozzle directs the flow of superheated, ultrafast gases in order to squeeze as much momentum transfer as possible out of available propellant. The lower the pressure of the surrounding atmosphere is, the more those gases will expand immediately after leaving the nozzle – giant vacuum nozzles simply try to harness the additional momentum available from that extra expansion. This is why rocket exhausts appear to spread and thin out as launch vehicles reach higher and higher altitudes.

A Falcon 9 upper stage’s vacuum nozzle glows white hot during an orbital MVac burn. (SpaceX)

In this sense, the perfect theoretical vacuum nozzle is quite literally infinitely long. The job of vacuum rocket engineers is to find the perfect balance between that impractical theoretical perfection and the limits of real-world materials and dynamics. In theory, SpaceX’s sea-level Raptor engines have already been designed to operate in vacuum conditions, while the engine’s closed-cycle design and regeneratively (i.e. propellant) cooled nozzle should apply well to a vacuum design.

If SpaceX is lucky, there will be few roadblocks in the way of simply lengthening a SL Raptor-style nozzle and calling it a day, in which case it would be impressive but not all that surprising if SpaceX is actually able to begin RVac testing before the end of 2019. Once a rough V1.0 engine is in place, the process of optimizing efficiency can be done slowly and methodically, all while exploiting an unprecedented wealth of data from flight and orbit-tested Raptor Vacuum engines.

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Eric Ralph is Teslarati's senior spaceflight reporter and has been covering the industry in some capacity for almost half a decade, largely spurred in 2016 by a trip to Mexico to watch Elon Musk reveal SpaceX's plans for Mars in person. Aside from spreading interest and excitement about spaceflight far and wide, his primary goal is to cover humanity's ongoing efforts to expand beyond Earth to the Moon, Mars, and elsewhere.

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Musk bankers looking to trim xAI debt after SpaceX merger: report

xAI has built up $18 billion in debt over the past few years, with some of this being attributed to the purchase of social media platform Twitter (now X) and the creation of the AI development company. A new financing deal would help trim some of the financial burden that is currently present ahead of the plan to take SpaceX public sometime this year.

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Credit: SpaceX

Elon Musk’s bankers are looking to trim the debt that xAI has taken on over the past few years, following the company’s merger with SpaceX, a new report from Bloomberg says.

xAI has built up $18 billion in debt over the past few years, with some of this being attributed to the purchase of social media platform Twitter (now X) and the creation of the AI development company. Bankers are trying to create some kind of financing plan that would trim “some of the heavy interest costs” that come with the debt.

The financing deal would help trim some of the financial burden that is currently present ahead of the plan to take SpaceX public sometime this year. Musk has essentially confirmed that SpaceX would be heading toward an IPO last month.

SpaceX IPO is coming, CEO Elon Musk confirms

The report indicates that Morgan Stanley is expected to take the leading role in any financing plan, citing people familiar with the matter. Morgan Stanley, along with Goldman Sachs, Bank of America, and JPMorgan Chase & Co., are all expected to be in the lineup of banks leading SpaceX’s potential IPO.

Since Musk acquired X, he has also had what Bloomberg says is a “mixed track record with debt markets.” Since purchasing X a few years ago with a $12.5 billion financing package, X pays “tens of millions in interest payments every month.”

That debt is held by Bank of America, Barclays, Mitsubishi, UFJ Financial, BNP Paribas SA, Mizuho, and Société Générale SA.

X merged with xAI last March, which brought the valuation to $45 billion, including the debt.

SpaceX announced the merger with xAI earlier this month, a major move in Musk’s plan to alleviate Earth of necessary data centers and replace them with orbital options that will be lower cost:

“In the long term, space-based AI is obviously the only way to scale. To harness even a millionth of our Sun’s energy would require over a million times more energy than our civilization currently uses! The only logical solution, therefore, is to transport these resource-intensive efforts to a location with vast power and space. I mean, space is called “space” for a reason.”

The merger has many advantages, but one of the most crucial is that it positions the now-merged companies to fund broader goals, fueled by revenue from the Starlink expansion, potential IPO, and AI-driven applications that could accelerate the development of lunar bases.

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Tesla pushes Full Self-Driving outright purchasing option back in one market

Tesla announced last month that it would eliminate the ability to purchase the Full Self-Driving software outright, instead opting for a subscription-only program, which will require users to pay monthly.

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Credit: Tesla

Tesla has pushed the opportunity to purchase the Full Self-Driving suite outright in one market: Australia.

The date remains February 14 in North America, but Tesla has pushed the date back to March 31, 2026, in Australia.

Tesla announced last month that it would eliminate the ability to purchase the Full Self-Driving software outright, instead opting for a subscription-only program, which will require users to pay monthly.

If you have already purchased the suite outright, you will not be required to subscribe once again, but once the outright purchase option is gone, drivers will be required to pay the monthly fee.

The reason for the adjustment is likely due to the short period of time the Full Self-Driving suite has been available in the country. In North America, it has been available for years.

Tesla hits major milestone with Full Self-Driving subscriptions

However, Tesla just launched it just last year in Australia.

Full Self-Driving is currently available in seven countries: the United States, Canada, China, Mexico, Australia, New Zealand, and South Korea.

The company has worked extensively for the past few years to launch the suite in Europe. It has not made it quite yet, but Tesla hopes to get it launched by the end of this year.

In North America, Tesla is only giving customers one more day to buy the suite outright before they will be committed to the subscription-based option for good.

The price is expected to go up as the capabilities improve, but there are no indications as to when Tesla will be doing that, nor what type of offering it plans to roll out for owners.

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Starlink terminals smuggled into Iran amid protest crackdown: report

Roughly 6,000 units were delivered following January’s unrest.

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Credit: Starlink/X

The United States quietly moved thousands of Starlink terminals into Iran after authorities imposed internet shutdowns as part of its crackdown on protests, as per information shared by U.S. officials to The Wall Street Journal

Roughly 6,000 units were delivered following January’s unrest, marking the first known instance of Washington directly supplying the satellite systems inside the country.

Iran’s government significantly restricted online access as demonstrations spread across the country earlier this year. In response, the U.S. purchased nearly 7,000 Starlink terminals in recent months, with most acquisitions occurring in January. Officials stated that funding was reallocated from other internet access initiatives to support the satellite deployment.

President Donald Trump was aware of the effort, though it remains unclear whether he personally authorized it. The White House has not issued a comment about the matter publicly.

Possession of a Starlink terminal is illegal under Iranian law and can result in significant prison time. Despite this, the WSJ estimated that tens of thousands of residents still rely on the satellite service to bypass state controls. Authorities have reportedly conducted inspections of private homes and rooftops to locate unauthorized equipment.

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Earlier this year, Trump and Elon Musk discussed maintaining Starlink access for Iranians during the unrest. Tehran has repeatedly accused Washington of encouraging dissent, though U.S. officials have mostly denied the allegations.

The decision to prioritize Starlink sparked internal debate within U.S. agencies. Some officials argued that shifting resources away from Virtual Private Networks (VPNs) could weaken broader internet access efforts. VPNs had previously played a major role in keeping Iranians connected during earlier protest waves, though VPNs are not effective when the actual internet gets cut.

According to State Department figures, about 30 million Iranians used U.S.-funded VPN services during demonstrations in 2022. During a near-total blackout in June 2025, roughly one-fifth of users were still able to access limited connectivity through VPN tools.

Critics have argued that satellite access without VPN protection may expose users to geolocation risks. After funds were redirected to acquire Starlink equipment, support reportedly lapsed for two of five VPN providers operating in Iran.

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A State Department official has stated that the U.S. continues to back multiple technologies,  including VPNs alongside Starlink, to sustain people’s internet access amidst the government’s shutdowns.

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