Peter's Quasi-Daily Blah-g

Space startup Astrobotic put its rotating detonation rocket engine (RDRE) to the test for the first time, demonstrating a potentially groundbreaking technology that generates thrust by supersonic combustion.

Astrobotic completed a series of hot-fire tests on two engine prototypes at NASA’s Marshall Space Flight Center in Alabama. Each engine produced more than 4,000 pounds of thrust (1,800 kilograms) for a combined 470 seconds of total runtime, including a single 300-second burn.

The recent demonstration brings the private space industry one step closer to a more efficient rocket propulsion system that could allow crewed landers to travel to deep space destinations such as the Moon and Mars.

Fire in the hole

An RDRE produces thrust through a series of detonations that travel around a circular channel, combining highly pressurized propellant with an oxidizer inside a combustion chamber. While traditional rocket engines ignite vehicles through exhaust, RDREs are propelled by shockwaves. As a result, RDREs are designed to be more efficient, using less fuel than other types of propulsion systems, in addition to being compact.

Astrobotic’s prototype engine, named Chakram, is designed and developed with support from two NASA Small Business Innovation Research awards and a Space Act Agreement with NASA Marshall. “This was pulled off by a small group working on a modest budget,” Travis Vazansky, Astrobotic’s RDRE program manager, said in a statement. “Seeing the engine perform flawlessly on its first attempt is a testament to their acumen, ingenuity, and scrappiness.”

The Pittsburgh-based company said that the engine prototypes aced the eight hot fire tests, with no evidence of damage to the engines during the firing. “With any cutting-edge technology like an RDRE, moving from design into testing, you’re always worried about unknown factors that could be critical to performance. But the engine performed even better than expected,” Bryant Avalos, Astrobotic’s principal investigator for the Chakram program, said in a statement.

Over the Moon

Astrobotic is a self-proclaimed Moon company, developing lunar landers for NASA’s Commercial Lunar Payload Services (CLPS) program. The startup became the first U.S. commercial company to launch a lander to the Moon in 2024 with its Peregrine mission, which unfortunately botched its lunar touchdown due to a propulsion system anomaly.

A follow-up mission to the lunar south pole is currently in the works and scheduled to launch sometime this year. Astrobotic is hoping to use engines like Chakram to power its upcoming lunar landers. “RDRE technology could support a wide range of Astrobotic missions, from propulsion on future lunar landers to in-space orbital transfer vehicles, and other capabilities that will help expand operations throughout cislunar space,” Avalos said.

Following the recent hot fire test, Astrobotic will continue developing its engine through a series of upcoming design iterations and test campaigns.

The company is not alone in working to mature the new technology. In May 2025, Houston-based propulsion company Venus Aerospace used its own RDRE to propel a small rocket to an altitude of 4,400 feet (1,340 meters) above the New Mexico desert.

NASA is also developing its own detonating engine, which the agency first began testing in 2022. A year later, a 3D printed prototype of the engine produced more than 5,800 pounds of thrust for a total of 251 seconds during a hot fire test.

Related article: Gizmodo Science Fair: A Rocket Engine That Turns Controlled Explosions Into Thrust

If you bought a Tesla from before 2023 in the hopes that a future software upgrade would render it capable of unsupervised full self-driving—the as-yet unrealized dream of a truly self driving car, in other words—that’s never going to happen, Elon Musk admitted on an earnings call Wednesday.

It’s possible you might be able to get a hardware upgrade, rather than having to trade in your Tesla for a new one, but from the sound of it, retrofitting hundreds of thousands of cars with new computers and cameras is going to be a colossal new project for Tesla.

The FSD hardware packaged known as Hardware 3 was standard until Hardware 4 came along in early 2023, though it took until May of that year for Hardware 4 to reach all models. (To tell which version you have, go to Settings in your infotainment system, then tap Software, and then Additional Vehicle Information).

“Unfortunately, Hardware 3, I wish it were otherwise, but Hardware 3 simply does not have the capability to achieve unsupervised FSD,” Musk said during the call on Wednesday. “We did think at one point it would, but relative to Hardware 4 it has only 1/8 the memory bandwidth of Hardware 4.”

Some customers have voiced frustration about Tesla not delivering FSD, and Tesla faces a class action lawsuit in Australia alleging that “Despite statements or representations to the contrary, the hardware on Tesla vehicles is incapable of supporting fully autonomous or close to autonomous driving.”

Seemingly in an effort to stave off a customer revolt over the revelation that the Hardware 3 package will never be capable of unsupervised driving, Musk has described the following program:

“For customers that have bought FSD, what we’re offering is essentially a trade-in, like a discounted trade-in, for cars that have AI4 hardware. And we’ll also be offering the ability to upgrade the car to replace the computer.”

He also threw in this curveball:

“And you also need to replace the cameras, unfortunately, to go to Hardware 4.”

In other words, your car has to be retrofit with multiple new parts in order to even stand a chance of ever receiving a software upgrade that enables Tesla’s unsupervised self-driving mode.

Musk claimed on the call that Tesla plans to create “micro-factories, or small factories,” concentrated in population centers, where “mini production lines” will change out the hardware. Relying on local service centers, where mechanics would intersperse this hardware upgrade with their other tasks, would be “extremely slow,” he said.