

SpaceX
SpaceX’s Starship hopper spotted with trio of dual-bell Raptor engines
Following a brief ‘hop’ (via crane) off of a concrete build stand, the aft section of SpaceX’s first full-scale Starship hopper (Starhopper?) revealed that SpaceX technicians have already installed what appear to be three real Raptor engines, presumably the first time the propulsion system has ever been mounted to something that might eventually fly.
For a number of reasons, there is a strong chance that these Raptors are actually just boilerplate placeholders standing in as structural guides for the real deal some months down the line. On the other hand, there are also a number of reasons to assume that these apparent engines are indeed real Raptors.
Star ship hopper might be a bit bigger than we thought and with the crane placements over the nose end of the vehicle. This could suggest, @SpaceX are planning to move the segment elsewhere perhaps to the welding stand? We will have to wait and see. (Austin Barnard📸) #2019🚀 pic.twitter.com/kn8hhUPWCU
— Austin Barnard🚀 (@austinbarnard45) January 1, 2019
Despite an already shocking series of rapid-fire developments in the South Texas Starhopper saga, the abrupt appearance of what appears to be three Raptor engines – mirroring CEO Elon Musk’s recent statement that the test vehicle would sport three Raptors – is by far the most unexpected moment yet for the prototype Starship. Purportedly a full-scale prototype of BFR’s upper stage/spaceship (now known as Starship), Musk indicated over the last two weeks that the hopper has been designed to perform a number of hop tests in which the craft’s three Raptors would power it to a range of (relatively low) altitudes above Boca Chica, Texas.
According to a recent FCC filing related to this test program, SpaceX is currently seeking a license for Starship hop tests that will not exceed 5 km (3.1 mi) in altitude and/or 6 minutes in duration. There is admittedly nothing mentioned about the maximum allowed velocity during those tests, but – much like Blue Origin performs supersonic tests of New Shepard in Cape Horn, Texas – SpaceX will likely seek and be granted permission to break the sound barrier during those hypothetical tests. Nevertheless, a 5km ceiling is a fairly significant cap on the range of performance Starhopper will be able to test – accelerating vertically at 2Gs, Starhopper could travel from sea level to 5km in less than 30 seconds while reaching speeds no higher than Mach 1-1.5.
- SpaceX technicians and engineers are continuing to work at a breakneck pace on Starhopper. (NASASpaceflight – bocachicagal)
- At this rate, the hopper will likely wind up around 40m (130 feet) tall. (NASASpaceflight – bocachicagal)
- A close examination of these three engine-like protrusions suggests a level of fit and finish far exceeding a boilerplate stand-in. (NASASpaceflight – bocachicagal)
Combined with the apparent fact that this Starhopper’s fins seem unlikely to ever actuate (i.e. no aerodynamic control surfaces), it’s probable that this ad hoc prototype is only meant to perform a very limited range of hop tests, perhaps as basic as ironing out the kinks of operating a trio of gimballed Raptors and ensuring that they can safely and reliably launch, hover, and land a very large Starship-shaped mass simulator. Falcon 9’s Grasshopper and F9R reusability testbeds performed a very similar task some five years ago, offering SpaceX engineers the opportunity to optimize software and hardware needed to reliably recover real orbital-class rockets after launch. Although Falcon 9 has nine gimballed Merlin 1D engines, SpaceX has long sided with the sole center Merlin as the dedicated landing engine and has only briefly experimented with triple-Merlin landing burns.
Dual-expansion whaaaaat?
According to Musk, Raptor – an advanced liquid methane and oxygen engine with a uniquely efficient propulsion cycle – was expected to produce an impressive ~2000 kN (200 ton, 450K lbf) of thrust in its finished form as of September 2018. However, Musk also mentioned in a late-2017 Reddit AMA that SpaceX engineers were modifying the ship’s design to ensure engine-out reliability during all regimes of flight, landing in particular. To accomplish this feat with an engine as powerful as Raptor, two or three Raptors – capable of producing as much as 600 tons of thrust total – would need to reliably throttle as low as 25%, assuming a landing mass of around 150t. To allow a nearly empty ship (~100t) to still reliably land with three Raptors ignited, the engines would need to be able to throttle to 20% or less.
Known as deep throttling in rocketry, ensuring stable combustion and thrust at 20% (let alone 40%) throttle is an extraordinarily challenging feat, often subjecting engines to forces that can literally tear non-optimized hardware apart. To achieve such a deep throttle capability without excessively disrupting the engine’s design, SpaceX appears to have potentially sided with less efficient but extremely simple alternative, known as a dual-bell (or dual-expansion) rocket nozzle. A 1999 Rocketdyne paper concisely explained the primary draws of such a nozzle:
“The [altitude-compensating] dual-bell nozzle offers a unique combination of performance, simplicity, low weight, and ease of cooling” – Horn & Fisher, 1999
Exactly
— Elon Musk (@elonmusk) December 27, 2018
Given that SpaceX has decided to delay the introduction and certification of a vacuum-optimized Raptor engine, choosing to instead use the same Raptor on both BFR stages, something like a dual-bell nozzle would be one of the best possible ways for the company to retain some of the efficiency benefits of a vacuum engine while also drastically improving design simplicity, ease of manufacturing, and cutting development time. Aside from offering efficiency gains by way of altitude compensation, a dual-bell nozzle also happens to enable a given engine to operate a much wider throttle range by mitigating problems with flow separation and instability.
- A gif of Raptor throttling over the course of a 90+ second static-fire test in McGregor, Texas. (SpaceX)
- Note that Merlin 1D and prior Raptor prototypes both feature traditional single nozzles. (Pauline Acalin)
- An overview of dual-bell and deflection nozzles. Raptor appears to have now graduated to the former style. (Johan Steelant, 2011)
- Starhopper’s Raptors feature a very distinct seam and second curve, indicative of a dual-bell nozzle. (NASASpaceflight /u/bocachicagal)
For Starhopper and Starship, both aspects are an undeniable net-gain and it’s entirely possible that these dual-bell nozzles – if successfully demonstrated – could find their way onto Falcon 9 and Falcon Heavy to further boost their booster performance and efficiency.
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News
SpaceX set to launch Axiom’s mission for diabetes research on the ISS
Axiom’s Ax-4 will test CGMs & insulin stability in microgravity—potentially reshaping diabetes care for Earth & future astronauts.

Axiom Space’s Ax-4 mission is set to launch on a SpaceX Falcon 9 rocket. Ax-4 will advance diabetes research in microgravity, marking a milestone for astronaut health.
Axiom Space’s fourth crewed mission is scheduled to launch with SpaceX on May 29 from NASA’s Kennedy Space Center in Florida. The Ax-4 mission will carry a diverse crew and a record-breaking scientific payload to the International Space Station (ISS).
The Ax-4 crew is led by Axiom’s Peggy Whitson and includes Shubhanshu Shukla from India, Sławosz Uznański from the European Space Agency, and Tibor Kapu from Hungary. The mission represents firsts for India, Hungary, and Poland, with Uznański being Poland’s first astronaut in over 40 years.
Ax-4 will conduct nearly 60 science investigations from 31 countries during its two-week ISS stay. A key focus is the “Suite Ride” initiative, a collaboration with Burjeel Holdings to study diabetes management in microgravity.
“The effort marks a significant milestone in the long-term goal of supporting future astronauts with insulin-dependent diabetes (IDDM), a condition historically deemed disqualifying for spaceflight,” Axiom noted. The mission will test Continuous Glucose Monitors (CGMs) and insulin stability to assess their performance in space.
Axiom explained that testing the behavior of CGMs and insulin delivery technologies in microgravity and observing circadian rhythm disruption could help diabetes experts understand how CGMs and insulin pens can improve diabetes monitoring and care in remote or underserved areas on Earth. The research could benefit diabetes management in isolated regions like oil rigs or rural areas.
The mission’s findings on insulin exposure and CGM performance could pave the way for astronauts with diabetes to safely participate in spaceflight. As Axiom and SpaceX push boundaries, Ax-4’s diabetes research underscores the potential for space-based innovations to transform healthcare on Earth and beyond.
Elon Musk
EU considers SES to augment Starlink services
The EU considers funding SES to support Starlink. With MEO satellites already serving NATO, SES could be key in Europe’s space autonomy push.

European satellite company SES is negotiating with the European Union (EU) and other governments to complement SpaceX’s Starlink, as Europe seeks home-grown space-based communication solutions. The talks aim to bolster regional resilience amid growing concerns over reliance on foreign providers.
In March, the European Commission contacted SES and France’s Eutelsat to assess their potential role if American-based Starlink access for Ukraine was disrupted. The European Commission proposed funding EU-based satellite operators to support Kyiv. Ukraine is considering alternatives to Starlink over concerns about Elon Musk’s reliability.
Arthur De Liedekerke of Rasmussen Global warned, “Elon Musk is, in fact, the guardian of Ukraine’s connectivity on the battlefield. And that’s a strategic vulnerability.” However, SpaceX’s Starlink constellation is leagues ahead of any competition in the EU.
“Now the discussions are much more strategic in nature. They’re much more mid-term, long-term. And what we’re seeing is all of the European governments are serious about increasing their defense spending. There are alternatives, not to completely replace Starlink, that’s not possible, but to augment and complement Starlink,” SES CEO Adel Al-Saleh told Reuters.
SES operates about 70 satellites, including over 20 medium Earth orbit (MEO) units at 8,000 km. The company provides high-speed internet for government, military, and underserved areas. It plans to expand its MEO fleet to 100, enhancing secure communications for NATO and the Pentagon.
“The most significant demand (for us) is European nations investing in space, much more than what they did before,” Al-Saleh said.
Competition from Starlink, Amazon’s Kuiper, and China’s SpaceSail, with their extensive low-Earth orbit constellations, underscores Europe’s push for independence.
“It is not right to say they just want to avoid Starlink or the Chinese. They want to avoid being dependent on one or two providers. They want to have flexibility,” Al-Saleh noted.
SES’s discussions reflect Europe’s strategic shift toward diversified satellite networks, balancing reliance on Starlink with regional capabilities. As governments ramp up defense spending, SES aims to play a pivotal role in complementing global providers, ensuring robust connectivity for military and civilian needs across the continent.
News
Amazon launches Kuiper satellites; Can it rival Starlink?
With 27 satellites in orbit, Amazon kicks off its $10B plan to deliver global broadband. Can Bezos’ Kuiper take on Musk’s Starlink?

Amazon’s Project Kuiper launched its first 27 satellites on Monday, marking the start of a $10 billion effort that could compete with SpaceX’s Starlink with a global broadband internet network.
Amazon’s Kuiper satellites launched aboard a United Launch Alliance Atlas V rocket from Cape Canaveral, Florida. Project Kuiper’s recent launch is the initial step toward deploying Amazon’s 3,236 satellites for low-Earth orbit connectivity. Amazon’s satellite launch was initially set for April 9 but was delayed due to bad weather.
Now that the Kuiper satellites have been launched, Amazon is expected to publicly confirm contact with the satellites from its mission operations center in Redmond, Washington. The company aims to start offering Kuiper services to customers later this year. Project Kuiper was unveiled in 2019 and targets consumers, businesses, and governments who need reliable internet service, similar to Starlink.
Amazon has a deadline from the U.S. Federal Communications Commission to deploy 1,618 satellites by mid-2026. Analysts suggest the company may require an extension to its Kuiper satellite deployment deadline due to the project’s year-long delay from its planned 2024 start.
United Launch Alliance could conduct up to five more Kuiper missions this year, according to ULA CEO Tory Bruno. Amazon noted in a 2020 FCC filing that Kuiper services could begin with 578 satellites, initially covering northern and southern regions.
Kuiper’s launch pits Amazon against SpaceX’s Starlink and telecom giants like AT&T and T-Mobile, with a focus on underserved rural areas.
“There’s an insatiable demand for the internet,” Amazon Executive Chairman Jeff Bezos told Reuters in January. “There’s room for lots of winners there. I predict Starlink will continue to be successful, and I predict Kuiper will be successful as well.”
Global interest in satellite alternatives is rising. Ukraine is exploring Starlink alternatives with the European Union (EU), driven by concerns over Elon Musk. Germany’s military, Bundeswehr, also plans its own constellation to ensure independent communications. However, like Amazon’s Kuiper Project, EU options lag behind Starlink.
Amazon’s consumer expertise and cloud computing infrastructure give Kuiper a competitive edge despite Starlink’s market lead. As Kuiper ramps up launches, its success could reshape broadband access while challenging SpaceX’s dominance in the satellite internet race.
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