Why rain is a problem for hypersonic missiles, and how Auriga tests it

Auriga Space, a California company building electromagnetic launch technology, wants to fix one of the slowest steps in developing American hypersonic weapons: testing their materials and parts on the ground. Instead of a rocket-powered sled racing down steel rails, its Prometheus accelerator uses an electric linear motor to push a magnetically levitated test article through a sealed tube, at air pressures matched to real flight conditions, then slows it down so engineers can recover it intact and run it again within minutes.

Prometheus has reached supersonic speeds and is working toward hypersonic ones, according to the company. Auriga says it is operating under contracts with the U.S. Air Force and the Missile Defense Agency, and in July it launched a commercial service that fires materials and coatings through real water droplets and airborne particles at speed, with Axiom Materials as its first customer. The company has also partnered with the U.S. Army to study electromagnetic launchers for shooting down drones, and is now planning Thor, a much larger outdoor track with an 8-foot-wide tube for testing full subsystems.

The Defence Blog asked Auriga founder and Chief Executive Officer Winnie Lai how the company moved from electromagnetic space launch into hypersonic testing, what Prometheus can do today, what real-weather tests have revealed that simulations missed, and what it will take to bring Thor online. Her answers are published below in full.

Q: Auriga originally emerged around electromagnetic launch technology. How did that work lead you toward hypersonic ground testing, and why did you see this as an area where your technology could make a practical difference?

A: Auriga was founded in 2023 with the long-term goal of making space launch more efficient in support of the ever-growing need for space access for commercial and defense applications. That said, space launch capabilities have historically been challenging to develop and require significant time and capital. As such, we looked for near-term revenue opportunities for the technology we’re developing.

Early on, we asked where our technology could make a difference today. Hypersonic testing stood out because there’s a real shortage of affordable test capacity in the U.S. A limited number of tests are conducted each year, and there is a multi-year backlog. Hypersonic testing is a natural fit for an electromagnetic accelerator because it involves accelerating payloads to very high speeds using only electricity. We can bring an object to high speed precisely, run tests again quickly, and recover the test article when needed. And because we use the technology stack that we need for launch, that work feeds directly into our space roadmap. I think of it the way SpaceX thinks of Starlink: the near-term business helps fund the long-term goal.

The weather box. Photo courtesy of Auriga Space

Q: For readers who may not be familiar with Prometheus, could you walk us through how a typical test works and what makes the electromagnetic approach different from a conventional rocket-sled test?

A: A conventional rocket sled is propelled by a rocket motor and rides on steel rails. That contact creates vibration that can show up in the test data, and once the motor ignites, there’s no stopping the run or recovering the test article. Tests also happen at sea-level pressure, so the results don’t fully reflect flight conditions, which typically involve lower pressures at higher altitudes. The track requires regular inspections, and test frequency is limited by the availability of rocket motors. Demand exceeds supply, leading to multi-year wait times.

Prometheus, our electromagnetic accelerator for hypersonic testing, takes a different approach. Tests take place inside a sealed tube, where we can set the pressure to match the flight conditions the customer wants to study. A linear electric motor accelerates the test article, which is magnetically levitated to provide a low-vibration environment. Because the system is electrically powered, we can also customize the speed through software and, if desired, slow the article down so it can be recovered for inspection. By eliminating the need for rocket motors and reducing maintenance between tests, we can lower the cost per test and run tests more frequently.

Q: One of the advantages you highlight is the ability to recover test hardware and repeat tests quickly. How does that change the way engineers can develop and validate hypersonic materials or components?

A: When a test article can’t be recovered, engineers have to rely on data collected during the test, which is often limited. But when you can recover it, you can examine the article in much greater detail.

One of the tests we offer is materials testing under different weather conditions. For example, engineers can study how specific materials and coatings respond to raindrops and other environmental conditions at high speeds, which can cause damage, cracking, or delamination. By recovering the test article, they can inspect the material and measure the exact deformation and damage.

It also means they can run the same article again under the same or different conditions. Right now, many programs have to pack years of learning into a handful of expensive tests, so they test late and slow down development. If testing is frequent and affordable, teams can try a design change and see the results quickly, allowing them to iterate faster. This lets hardware teams work more like software teams and catch problems on the ground instead of discovering them during an expensive flight test.

Q: What level of performance has Prometheus demonstrated so far in terms of speed, test article size, and turnaround between runs?

A: We’ve reached supersonic speeds and are continuing to advance our performance and capabilities toward hypersonic speeds. One of the key advantages of our electromagnetic accelerator is its turnaround time. Because it runs entirely on electricity and doesn’t require rocket motors, we can be ready for the next run in minutes, with a target cadence of multiple tests per day.

Right now, our test article size is limited by the 4-inch diameter of our tube. That’s one of the reasons we’re developing Thor, a larger outdoor track that will allow us to accommodate larger test articles and expand our testing capabilities. Beyond hypersonic testing, the technology can also support high-G testing for fuzes and maneuverability, as well as testing the effects of different weather conditions.

Schlieren image of a test article in Prometheus. Photo courtesy of Auriga Space

Q: Hypersonic vehicles face a combination of heat, vibration, aerodynamic loads, rain, ice, and particle impacts. Which of these conditions can your current system reproduce, and where are the main technical challenges still ahead?

A: Our current system can support several types of testing, including aerodynamics, controlled acceleration and high-G testing, impact testing, and weather-effects testing. For high-acceleration testing, we can test electronic components, sensors, IMUs, fuzes, and structures designed for high-G maneuvering. For weather-effects testing, we can expose materials and coatings to real water droplets and airborne particles at precise locations along the test article’s path, under relevant flight pressures. This lets engineers study erosion, impact damage, and material degradation. We can also conduct impact testing to evaluate lethality, as well as aerodynamic testing to study aerodynamic forces and control surfaces. Our goal is to generate high-fidelity trajectory and environmental data that can validate modeling and simulation, including digital twins.

Our plan ahead includes adding additional weather-effects testing capabilities, expanding the range of flight conditions we can reproduce, and reaching higher speeds. Thor, our planned larger outdoor accelerator, will enable us to move beyond small components to larger test articles.

Q: Auriga has also introduced testing involving real rain and airborne particles at high speed. What have you learned from those tests that was difficult to capture through simulation or more traditional laboratory methods?

A: Simulation and modeling are only as good as the data used to validate them, which is where inexpensive, high-cadence testing makes a difference. We’re testing with real weather conditions, too. Many facilities use nylon beads to simulate rain. They can approximate an impact, but they don’t behave like real water or ice. A real water droplet deforms and breaks apart on impact with the test article, which is difficult to model accurately and reproduce with nylon beads. We can also test at relevant flight pressures.

One thing we’ve observed is that the incoming bow shock deforms water droplets before impact, changing their shape and, in turn, how they impact the test article. Nylon beads can’t replicate this.

We levitate water droplets and other particles and position them precisely in the article’s path, so the material experiences the kinds of erosion and impacts it would encounter in flight. Because engineers can recover the samples, they can study the damage in detail. They can also test the cumulative effects of repeated weather impacts and compare how different article shapes respond. Effects can vary by geometry and whether the impact occurs at the leading edge or elsewhere on the article.

Q: Looking at the broader U.S. hypersonic effort, where do you see the greatest need for more testing capacity today, and how could faster, repeatable ground testing affect development timelines?

A: The greatest need is early-stage testing capacity. The Pentagon requested $3.9 billion for hypersonic weapons in 2026, but ground testing on rocket sleds is still expensive and slow to schedule. When every test is that costly, programs ration testing and save it for later stages, when a failure is most expensive to fix. That means materials and components often go to flight with less ground data than engineers would like.

Faster, repeatable ground testing changes that. If a program can test frequently, at lower cost, and get its hardware back, it can find problems in months that might otherwise surface years later in a flight test. That compresses the timeline from test to field, which is critical given how quickly adversaries are advancing their own hypersonic programs.

Q: You are now working toward a larger outdoor electromagnetic track. What new kinds of testing would that make possible, and what are the main milestones Auriga needs to reach before that system becomes operational?

A: Our full-scale system, Thor, will be an outdoor electromagnetic accelerator with a target tube diameter of 8 feet. It will be modular, allowing us to add length as testing requirements evolve and increase its performance capabilities over time. This will allow us to move beyond individual materials and small components to testing larger subsystems and full systems. At full operational capacity, we anticipate conducting multiple tests per week, helping address the shortage of hypersonic ground-test capacity in the U.S.

The main milestones are scaling up our technology to support larger test articles, integrating and validating the higher-power systems, and identifying a suitable site for construction. We’ll then need to complete system integration, commission the track, and validate its performance before it becomes operational.