Connect with us

News

Ex-SpaceX engineer leads Stratolaunch to major rocket engine test milestone

Stratolaunch has successfully completed the first full-scale test of its 200,000-lbf thrust PGA rocket engine. (Stratolaunch)

Published

7 years ago

on

Led by rocket propulsion expert Jeff Thornburg, Stratolaunch – famous for owning the largest fixed-wing aircraft ever built – has completed the first hot-fire test of a full-scale rocket engine component known as the preburner, a major milestone in the development of any launch vehicle or propulsion system.

Despite the significant size and power of the component, destined to support an engine that will generate 200,000 pounds (~900 kN) of thrust, Thornburg and his team of engineers and technicians have managed to go from designing the preburner to successfully hot-firing a full-scale test article, an extraordinary achievement by any measure.

Aside from SpaceX, Blue Origin, and Aerojet-Rocketdyne, Stratolaunch is the only private entity developing – let alone testing full-scale parts for – a liquid-fueled rocket engine as large as PGA. Shorthand for the Stratolaunch’s late founder and bankroller Paul G. Allen, PGA is a fuel-rich staged combustion cycle engine that uses liquid hydrogen and oxygen (hydrolox) fuel and oxidizer, typically resulting in high efficiency. In terms of scale and thrust, PGA is very closely comparable to SpaceX’s Merlin 1D engine, which uses kerosene instead of hydrogen but produces roughly 190,000 lbf (850 kN) of thrust and stands 4 feet (1.2m) wide and ~10 feet (~3m) tall.

Advertisement

Another major difference between PGA and Merlin 1D is the fact Merlin 1D’s nozzle is largely optimized for sea level while PGA is being built for a rocket that will be “launched” from a massive plane flying around 35,000 feet (~10.5 km), ultimately resulting in a nozzle that is much wider and longer, featuring nearly the same proportions as fully vacuum-optimized engines like SpaceX’s MVac. By widening the nozzle relative to the rest of the engine, rocket engines are able to operate far more efficiently at higher altitudes, where Earth’s atmosphere thins and exerts less pressure on the escaping exhaust gases. This is visualized well by the visible expansion of rocket exhausts during launches, morphing from a straight cylinder to a massive teardrop-shaped plume. At lower altitudes (and thus higher atmospheric pressures), wider nozzles can produce extreme turbulence and will ultimately shake themselves to destruction, preventing their usage on ground-launched rocket boosters.

Judging from official renders of the engine, PGA’s in-atmosphere variant appears to utilize a form of regenerative nozzle cooling very similar to that used on M1D, where liquid propellant flows through thin capillaries sandwiched between two or more layers of metal to cool the nozzle much like cold water chills the skin of an uninsulated water bottle.

Testing rocket engine preburners

In the case of staged combustion cycle hydrolox rocket engines, a small portion of liquid oxygen and all of the liquid hydrogen (hence “fuel-rich”) are mixed and combusted to generate hot gas that then spools up the engine’s primary turbopump(s), ultimately drawing fuel and oxidizer into the combustion quickly enough to ignite the engine and generate sustained thrust. The components that get those main turbopumps started are known collectively as the preburner, which is what Stratolaunch successfully tested – at full-scale – for the first time ever last week. For any liquid rocket engine that cannot solely rely on propellant tank pressure to deliver fuel to the combustion chamber, full-scale tests of preburners or gas-generators effectively mark the moment that engines truly become real.

“This is the first step in proving the performance and highly efficient design of the PGA engine. The hot-fire test is an incredible milestone for both the propulsion team and Stratolaunch.” – Jeff Thornburg, VP of Propulsion, Stratolaunch

Stratolaunch’s propulsion team will continue to test the preburner for longer durations and at higher power levels over the next several months, likely optimizing operations and tweaking or upgrading the preburner’s hardware as real tests produce valuable lessons-learned. Built entirely with additive manufacturing (3D printing), the team should be able to rapidly iterate on the physical design of the engine, a rarity in a field where traditional fabrication methods can take weeks or months to produce complex turbomachinery components with mercilessly strict tolerances.

According to Thornburg, the ultimate goal is to continue that additive-manufacturing-only strategy throughout the development of this rocket engine, theoretically enabling unprecedented design flexibility while also slashing production time throughout. PGA will ultimately power the creatively-named Medium Launch Vehicle (MLV), a small-ish air-launched rocket designed to place a respectable 3400 kg into low Earth orbit (LEO) as early as 2022, as well as a Heavy version of MLV and, potentially, a reusable spaceplane somewhere down the line.

Advertisement

 

For prompt updates, on-the-ground perspectives, and unique glimpses of SpaceX’s rocket recovery fleet check out our brand new LaunchPad and LandingZone newsletters!

Related Topics:

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.

Advertisement
Comments

News

Tesla Semi gets new adoptee in latest sighting

Tesla is continuing to increase the number of companies that have access to the Semi.

Published

39 minutes ago

on

May 9, 2025

By

Credit: Tesla

The Tesla Semi looks to have its newest adoptee as US Foods, the second-largest foodservice distributor in the United States, was seen with its badging on the all-electric Class 8 truck.

US Foods trails only Sysco Corporation in terms of foodservice distributors by volume in the United States. The company joined several other massive food industry entities, such as PepsiCo, and its subsidiary, Frito-Lay, have both utilized the Tesla Semi in their fleets.

Tesla Semi futuristic sci-fi acceleration sound will never get old

The Semi in question was spotted by X user Zanegler, a prominent tracker of the Tesla Semi and its factory, which sits near the company’s Gigafactory Nevada plant in Reno:

US Foods also has a distribution center in Reno, which could have something to do with its decision to start using the Semi in regional logistics.

With an influx of EV semitrucks hitting the market from many different manufacturers, it is evident that companies are taking the idea of making their fleets more environmentally friendly very seriously.

Advertisement

Tesla is still very close to unloading the Semi in a more volumized fashion, as the company’s Vice President of Vehicle Engineering, Lars Moravy, said in January:

“We just closed out the Semi factory roofing walls last week in Reno…but we’re prepping for mechanical installation of all the equipment in the coming months… The first builds of the high-volume Semi design come late this year in 2025 and begin ramping early in 2026.”

First Tesla Semi high-volume production builds expected this 2025

With the latest addition of US Foods, Tesla increases its list of companies that are planning or are already using the Semi to help with local logistics and transportation. Among them are:

  • PepsiCo
  • Walmart
  • Sysco
  • Costco
  • Martin Brower
  • Saia Inc.
  • UPS
  • Anheuser-Busch
  • DHL

Many other companies have plans to use the Semi in their fleets. Currently, Tesla appears to be hand-picking those who have access to the vehicle as the pilot program continues.

Advertisement
Continue Reading

Lifestyle

Tesla Cybertruck takes a bump from epic failing Dodge Charger

The Cybertruck seemed unharmed by the charging Charger.

Published

1 hour ago

on

May 9, 2025

By

Credit: Hammer_of_something/Reddit

There comes a time in a driver’s life when one is faced with one’s limitations. For the driver of a Dodge Charger, this time came when he lost control and crashed into a Tesla Cybertruck–an absolute epic fail. 

A video of the rather unfortunate incident was shared on the r/TeslaLounge subreddit.

Charging Charger Fails

As could be seen in the video, which was posted on the subreddit by Model Y owner u/Hammer_of_something, a group of teens in a Dodge Charger decided to do some burnouts at a Tesla Supercharger. Unfortunately, the driver of the Charger failed in his burnout or donut attempt, resulting in the mopar sedan going over a curb and bumping a charging Cybertruck.

Ironically, the Dodge Charger seemed to have been parked at a Supercharger stall before its driver decided to perform the failed stunt. This suggests that the vehicle was likely ICE-ing a charging stall before it had its epic fail moment. Amusingly enough, the subreddit member noted that the Cybertruck did not seem like it took any damage at all despite its bump. The Charger, however, seemed like it ran into some trouble after crashing into the truck.

Alleged Aftermath

As per the the r/TeslaLounge subreddit member, the Cybertruck owner came rushing out to his vehicle after the Dodge Charger crashed into it. The Model Y owner then sent over the full video of the incident, which clearly showed the Charger attempting a burnout, failing, and bumping into the Cybertruck. The Cybertruck owner likely appreciated the video, in part because it showed the driver of the Dodge Charger absolutely freaking out after the incident.

Advertisement

The Cybertruck is not an impregnable vehicle, but it can take bumps pretty well thanks to its thick stainless steel body. Based on this video, it appears that the Cybertruck can even take bumps from a charging Charger, all while chilling and charging at a Supercharger. As for the teens in the Dodge, they likely had to provide a long explanation to authorities after the incident, since the cops were called to the location.

Continue Reading

News

Tesla confronts Service complaints with new AI-backed strategy

Tesla will use a new AI Agent to help expedite Service claims and improve communication with customers.

Published

2 hours ago

on

May 9, 2025

By

tesla service
Credit: Tesla

Tesla is implementing a new AI-based strategy to improve service for owners. Service has routinely been among the biggest complaints of owners, although it has improved drastically over the past few years.

Some of the complaints that Tesla has received regarding its Service platform have evidently been used to develop new strategies to not only streamline the entire experience but also to make things easier for the company, which deals with many claims each week.

As a result of complaints in the past, Tesla has used various strategies to make things better for customers. However, the latest improvement comes as a result of AI, something Tesla leans on in many facets of its business.

Tesla adds ingenious solution to app to streamline Service appointments

Tesla’s AI and IT Infrastructure, Cybersecurity, and Vehicle Service head Raj Jegannathan said on X this week that the company is rolling out a new AI Agent specifically designed to handle service comms with customers.

He said the new Service AI Agent will detect delays in communications between the company and the customers, monitor the sentiment of these conversations, and auto-escalate certain claims directly to leaders.

It will also allow customers to type the word ‘Escalate’ in the message center portion of the phone app after two weeks of delays. This will help customers reach higher-ups more easily and likely will eliminate the complaints that many have had over the past few years.

The company is rolling out the AI Agent in ten pilot locations to start. Its first day being active was May 8.

Jegannathan said:

“Tesla Service’s new AI Agent detects comms delays, monitors sentiment, & auto-escalates to leaders. Starts tomorrow at 10 pilot locations. In 2 weeks, type “Escalate” in ‘message center’ to reach managers. Guardrails in place to prevent abuse. We’ll keep improving!”

Service has had a lot of interesting strategies used to improve things, but it has definitely been a weak point of the Tesla ownership experience. In a perfect world, vehicles wouldn’t need repair for anything, but that is not realistic.

Instead, Tesla has worked to expedite the entire Service experience through various strategies, including F1-style service, and a goal to fix two-thirds of repair claims within the same day.

Parts availability sometimes takes this goal out of reasonableness, but these constant attempts at improving the repair experience show Tesla is doing what it can to make things better for owners.

Continue Reading

Trending