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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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Tesla Full Self-Driving set to get an awesome new feature, Elon Musk says

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Credit: Teslarati

Tesla Full Self-Driving is set to get an awesome new feature in the near future, CEO Elon Musk confirmed on X.

Full Self-Driving is the company’s semi-autonomous driving program, which is among the best available to the general public. It still relies on the driver to ultimately remain in control and pay attention, but it truly does make traveling less stressful and easier.

However, Tesla still continuously refines the software through Over-the-Air updates, which are meant to resolve shortcomings in the performance of the FSD suite. Generally, Tesla does a great job of this, but some updates are definitely regressions, at least with some of the features.

Tesla Cybertruck owner credits FSD for saving life after freeway medical emergency

Tesla and Musk are always trying to improve the suite’s performance by fixing features that are presently available, but they also try to add new things that would be beneficial to owners. One of those things, which is coming soon, is giving the driver the ability to prompt FSD with voice demands.

For example, asking the car to park close to the front door of your destination, or further away in an empty portion of the parking lot, would be an extremely beneficial feature. Adjusting navigation is possible through Grok integration, but it is not always effective.

Musk confirmed that voice prompts for FSD would be possible:

Tesla Full Self-Driving is a really great thing, but it definitely has its shortcomings. Navigation is among the biggest complaints that owners have, and it is easily my biggest frustration with using it. Some of the routes it chooses to take are truly mind-boggling.

Another thing it has had issues with is being situated in the correct lane at confusing intersections or even managing to properly navigate through local traffic signs. For example, in Pennsylvania, there are a lot of stop signs with “Except Right Turn” signs directly under.

This gives those turning right at a stop sign the opportunity to travel through it. FSD has had issues with this on several occasions.

Parking preferences would be highly beneficial and something that could be resolved with this voice prompt program. Grocery stores are full of carts not taken back by customers, and many people choose to park far away. Advising FSD of this preference would be a great advantage to owners.

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Cybertruck

Elon Musk clarifies Tesla Cybertruck ’10 day’ comment, fans respond

Some are arguing that the decision to confirm a price hike in ten days is sort of counterproductive, especially considering it is based on demand. Giving consumers a timeline of just ten days to make a big purchase like a pickup truck for $60,000, and basically stating the price will go up, will only push people to make a reservation.

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Credit: Tesla

Elon Musk has clarified what he meant by his comment on X yesterday that seemed to indicate that Tesla would either do away with the new All-Wheel-Drive configuration of the Cybertruck or adjust the price.

The response was cryptic as nobody truly knew what Musk’s plans were for the newest Tesla Cybertruck trim level. We now have that answer, and fans of the company are responding in a polarizing fashion.

On Thursday night, Tesla launched the Cybertruck All-Wheel-Drive, priced competitively at $59,990. It was a vast improvement from the Rear-Wheel-Drive configuration Tesla launched last year at a similar price point, which was eventually cancelled just a few months later due to low demand.

Tesla launches new Cybertruck trim with more features than ever for a low price

However, Musk said early on Friday, “just for 10 days,” the truck would either be available or priced at $59,990. We can now confirm Tesla will adjust the price based on more recent comments from the CEO.

Musk said the price will fluctuate, but it “depends on how much demand we see at this price level.”

Some are defending the decision, stating that it is simply logical to see how the Cybertruck sells at this price and adjust accordingly.

Others, not so much.

Some are arguing that the decision to confirm a price hike in ten days is sort of counterproductive, especially considering it is based on demand. Giving consumers a timeline of just ten days to make a big purchase like a pickup truck for $60,000, and basically stating the price will go up, will only push people to make a reservation.

Demand will look strong because people want to lock in this price. The price will inevitably go up, and demand for the trim will likely fall a bit because of the increased cost.

Many are arguing Musk should have kept this detail internal, but transparency is a good policy to have. It is a polarizing move to confirm a price increase in just a week-and-a-half, but the community is obviously split on how to feel.

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Cybertruck

Tesla Cybertruck’s newest trim will undergo massive change in ten days, Musk says

It appears as if the new All-Wheel-Drive trim of Cybertruck won’t be around for too long, however. Elon Musk revealed this morning that it will be around “only for the next 10 days.”

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(Credit: Tesla)

Tesla’s new Cybertruck trim has already gotten the axe from CEO Elon Musk, who said the All-Wheel-Drive configuration of the all-electric pickup will only be available “for the next ten days.”

Musk could mean the price, which is $59,990, or the availability of the trim altogether.

Last night, Tesla launched the All-Wheel-Drive configuration of the Cybertruck, a pickup that comes in at less than $60,000 and features a competitive range and features that are not far off from the offerings of the premium trim.

Tesla launches new Cybertruck trim with more features than ever for a low price

It was a nice surprise from Tesla, considering that last year, it offered a Rear-Wheel-Drive trim of the Cybertruck that only lasted a few months. It had extremely underwhelming demand because it was only $10,000 cheaper than the next trim level up, and it was missing a significant number of premium features.

Simply put, it was not worth the money. Tesla killed the RWD Cybertruck just a few months after offering it.

With the news that Tesla was offering this All-Wheel-Drive configuration of the Cybertruck, many fans and consumers were encouraged. The Cybertruck has been an underwhelming seller, and this seemed to be a lot of truck for the price when looking at its features:

  • Dual Motor AWD w/ est. 325 mi of range
  • Powered tonneau cover
  • Bed outlets (2x 120V + 1x 240V) & Powershare capability
  • Coil springs w/ adaptive damping
  • Heated first-row seats w/ textile material that is easy to clean
  • Steer-by-wire & Four Wheel Steering
  • 6’ x 4’ composite bed
  • Towing capacity of up to 7,500 lbs
  • Powered frunk

It appears as if this trim of Cybertruck won’t be around for too long, however. Musk revealed this morning that it will be around “only for the next 10 days.”

Musk could mean the price of the truck and not necessarily the ability to order it. However, most are taking it as a cancellation.

If it is, in fact, a short-term availability decision, it is baffling, especially as Tesla fans and analysts claim that metrics like quarterly deliveries are no longer important. This seems like a way to boost sales short-term, and if so many people are encouraged about this offering, why would it be kept around for such a short period of time?

Some are even considering the potential that Tesla axes the Cybertruck program as a whole. Although Musk said during the recent Q4 Earnings Call that Cybertruck would still be produced, the end of the Model S and Model X programs indicates Tesla might be prepared to do away with any low-volume vehicles that do not contribute to the company’s future visions of autonomy.

The decision to axe the car just ten days after making it available seems like a true head-scratcher.

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