HOUSTON SPACEPORT— A cloudy day at the end of March, Andrew Duggleby guided me a safe distance away from a rocket engine. We didn’t have to go far, maybe 50 meters, because the prototype engine designed and built by his small engineering team is not that big.
We waited a few minutes before steam began to rush out of the engine. And then, for a few seconds, the engine made a distinct whistling sound. “There it is!” exclaimed Duggleby. Past The, he meant the sound of a rotating detonation motor firing after its ignition. The sound indicated that a reaction successfully rotated 20,000 times per second around the engine.
Duggleby is the technical director of a company he founded with his wife Sassie. Venus Aerospace aims to build a hypersonic aircraft that can carry perhaps a dozen passengers and travel at the astonishingly high speed of Mach 9, or more than 11,000 kilometers per hour.
“How much does the world change if you can get somewhere in an hour?” Sassie Duggleby asked me.
Walking really fast
Quite a lot, probably. And I had come to Venus Aerospace’s facilities in southeast Houston to see if there was any chance the company could achieve this ambitious goal.
Sure, I had some doubts. One problem is that Mach 9 is really, really damn fast. No airplane has ever gone this fast. The fastest aircraft ever built is Lockheed’s SR-71 “Blackbird”, which traveled at Mach 3.2. Anything above Mach 9 and you lose communication with the ground, as plasma begins to envelop the vehicle, as if it were a spacecraft returning to Earth through the upper atmosphere.
In terms of passenger travel comparisons, the Concorde traveled supersonic at Mach 2, or about 2,100 km/h. Most of the new generation of supersonic aircraft being developed today are in roughly the same range, such as the Boom Supersonic’s cruising speed of Mach 1.7
The Dugglebys propose a radically different flight profile. They intend for their aircraft to take off and then perform a 10-minute boost with its rocket engine. This will send the aircraft to an altitude of about 50 km, or halfway to space. Oh, and they’re aiming for an airport-like operational cadence of four flights a day.
To this end, the company recently decided on a fuel mixture for its engine: room temperature hydrogen peroxide and Jet-A, the fuel used by the majority of jet aircraft already flying at airports. The company’s engineers also recently achieved liquid peroxide and Jet A detonation, which is important for using a stable fuel composition.
An efficient engine
A key to making all of this work is to use a new type of engine based on “rotary detonation.” Governments around the world have been researching this technology for more than a decade because it has the potential to increase fuel efficiency in a variety of applications, from US Navy ships to rocket engines.
In a traditional rocket engine, a high-pressure propellant and an oxidizer are injected into a combustion chamber where they burn and produce an extremely energetic plume of exhaust gas – Newton’s second law of motion in action. A rotary detonation engine is different in that a detonation wave travels around a circular channel. This is maintained by the injection of fuel and oxidizer and produces a shock wave that travels outwards at supersonic speed.
It all sounds quite complicated and it is. But an increasing number of groups in Japan, Europe, the US and elsewhere have produced and tested such engines, so they are more than just theoretical. In lab tests, the engines have provided around a 10 percent increase in fuel efficiency.
That might not sound like a lot, but it’s a make-or-break number for Venus Aerospace. By mass, hypersonic aircraft are about 80 percent fuel and oxidizer. By increasing that fuel efficiency, there’s actually mass left over for important things like landing gear, wings, and even some passengers. “It allows us to really build a vehicle that is like an airplane,” said Andrew Duggleby.
Send in the drones
While Venus Aerospace is working on its rocket engine, the company has also begun testing drones to refine the shape of its plane. Recently, a 5-foot-long drone demonstrated a fully autonomous flight in California. Venus aims to go supersonic with an 8-foot drone before the end of this year and reach Mach 3 in early 2024 with a rotary detonation engine.
The company has approximately 80 full-time employees and 20 contractors, the majority of whom work in the company’s hangar at the Houston Spaceport. Venus Aerospace has raised $41 million so far, led by Prime Movers Lab, and Sassie Duggleby said she is working on raising a second round of funding.
She and her husband both previously worked for Virgin Orbit before founding Venus Aerospace in the summer of 2020. They feel it is important to have a company that both works hard, but also works reasonable hours.
“We like to say ‘Home for dinner,'” she said. “It’s both for our employees and our customers who travel around the world.”
Venus Aerospace has a very, very long way to go. But it seems to be taking the right steps at the beginning of its journey.
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