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SpaceX’s Starship Raptor Vacuum engine plans laid out by CEO Elon Musk
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.
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.
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.
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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SpaceX just picked up another $1.6 billion from the Pentagon, with the U.S. Space Force awarding two task orders worth $1.6 billion to fly 18 Falcon 9 missions from Vandenberg Space Force Base in California through the end of 2027. The launches will carry satellites for the Space Based Sensing and Targeting portfolio, a set of programs meant to help the military detect and track airborne threats and relay that information across forces in near real time.
The award falls under National Security Space Launch Phase 3 Lane 1, the Space Force’s faster, commercial style procurement track for missions that do not require the military’s most demanding certification process. It is also the largest single order publicly disclosed under that program so far, and the first task order issued since the Space Force nearly tripled Lane 1’s contract ceiling from $5.6 billion to $17 billion on July 17.
SpaceX to become America’s Military data backbone for missiles, drones, and warfighters
Eric Zarybnisky, the Space Force’s acting portfolio acquisition executive for space access, said the entire process, from identifying the requirement to signing the contract, took about two months, including a month set aside for companies to prepare proposals.
SpaceX is not just launching these satellites. It already holds the contracts to build two of the programs within the same portfolio, $4.16 billion for the Space Based Airborne Moving Target Indicator system and $2.29 billion for the Space Data Network Backbone, which Teslarati covered in May. That means SpaceX is now responsible for both building key pieces of the military’s next generation sensing network and getting them into orbit.
With this latest award, SpaceX’s Pentagon contract total for 2026 alone tops $8 billion, adding to a defense portfolio that already includes the Golden Dome missile defense software group SpaceX joined in April and a string of GPS launches it inherited after ULA’s Vulcan rocket ran into a booster anomaly, which we detailed in March.
Lane 1’s vendor pool technically includes seven companies: SpaceX, ULA, Blue Origin, Rocket Lab, Stoke Space, Impulse Space, and Relativity Space. In practice, SpaceX remains the only provider with the combination of launch cadence, flight proven Falcon 9 hardware, and West Coast infrastructure to support a campaign requiring roughly one Vandenberg launch a month for the next year and a half.
Some lawmakers have flagged the growing concentration of national security launches with one company as a risk worth watching. For now, the Space Force keeps backing SpaceX, with it being the company that shows up ready to launch.
Elon Musk shed two new bits of detail on Starship following its 13th test launch, which was an overwhelming success.
SpaceX launched Starship for the 13th time last Friday after two delays: one on Monday when several Raptor engines did not ignite, and another on Thursday due to unfavorable weather conditions in Starbase, Texas.
The launch was overwhelmingly successful. SpaceX was able to complete a necessary test of the heat shield tiles by increasing the acceleration of Starship from launch throughout the flight; 20 Starlink v3 satellites were released with no issue; the Super Heavy Booster landed safely in the Gulf of America, Ship successfully reignited engines while in space; and it also splashed down without incident in the Indian Ocean.
SpaceX Starship just nailed something it’s never done before
Nevertheless, more details are coming out about Starship, and Musk is doing the talking.
Starship Will Be Retrieved in the Ocean
Musk revealed on Tuesday night that Starship would be recovered by a ship in the Indian Ocean. SpaceX routinely tries to recover Starship after splashdown in an effort to find out more about the flight by examining the spacecraft afterward.
We’re sending a ship out to recover Starship https://t.co/fUqUZTITO9
— Elon Musk (@elonmusk) July 28, 2026
This helps engineers find out more about why things might have happened, allows them to examine any potential damage or anomalies that might have occurred, and increases the chances of an even more successful flight next time thanks to the additional information recovered.
Ship Could Have Been Caught by Tower Arms, Musk claims
Musk has already indicated that SpaceX will plan to attempt a catch of Starship with the 14th test flight. While this would be a major accomplishment, it would be an expected next step, considering the fact that the Super Heavy Booster has already been caught by the chopsticks on numerous occasions.
The ship landing was precise, meaning that it would have been caught by the tower arms https://t.co/6nbNrRfX9P
— Elon Musk (@elonmusk) July 29, 2026
A ship catch would be a great indication of where SpaceX stands in terms of reusability and launch cadence. A successful catch with relatively no incidents would be a good sign that SpaceX is nearing a more frequent launch of Starship, but also that the reusability of the massive rocket would be something many would expect in the near future.
It is a necessity to make life multiplanetary.
Elon Musk has updated his timeline for when humans will walk on Mars and for when ships will simply get there.
The objective of getting to Mars has been one of Musk’s biggest goals since becoming a serial entrepreneur and realizing that time on Earth is limited. Musk has said several times he hopes to die on Mars, and not by impact.
Musk now believes that people will be on Mars in “roughly 5 to 7 years.” He said that a Mars lander will get there “a few years sooner.”
People on Mars in roughly 5 to 7 years.
Mars lander a few years sooner.
— Elon Musk (@elonmusk) July 29, 2026
The response from Musk comes after NASA Administrator Jared Isaacman said that SpaceX’s biggest priority is the Moon and not Mars. Because of this, Isaacman conceded that he believes nuclear power and propulsion investments will provide “potentially the pathway with the fewest miracles required to put four people on Mars in the next 10 to 15 years.”
Of course, this is what NASA can do through taxpayer funding and nuclear investments, he added.
Musk’s grand ambitions are much more optimistic than most, and it is certainly a double-edged sword. This is not the first time timelines for Mars have been somewhat lofty, especially to those normal thinkers like you and me, not super geniuses like Musk.
In fact, the SpaceX and Tesla frontman has said on at least a dozen occasions that we could be on Mars in the coming years. Musk said 2020 would be the big year as early as 2009. In 2020, he was “highly confident” of a landing in 2026, and had even said 2024 in a best-case scenario.
The point is, the range has varied, and it’s anyone’s guess when we’ll get there. This latest adjustment to the timeline is typical of Musk, and while the Moon has seemingly taken priority over Mars, it is still worth mentioning that the ultimate goal is to make life multiplanetary, and it starts potentially with the Red Planet.
SpaceX scores another massive Pentagon deal to support military satellites
Elon Musk sheds two new bits of detail on Starship after 13th test launch
