How a Vertical Dive Becomes Forward Motion
The Scarlet Knight did not need a propeller to push water backward. Instead, it repeatedly changed its buoyancy—the tendency to rise or sink—then used its wings to turn that vertical movement into a forward glide.
Inside the glider, a pump moved mineral oil between an internal reservoir and a flexible bladder on the outside. When oil expanded the outer bladder, the vehicle displaced more water and became slightly buoyant, so it rose. Pulling oil back inside made it denser relative to the water around it, sending it downward. Its fixed wings were angled so that either motion also carried it forward, much as a glider converts a descent through air into forward travel.
A Slow, Repeating Route Through the Ocean
The vehicle traced a sawtooth path: glide upward, turn, glide downward, and repeat. Small control adjustments steered it while it traveled. Each cycle covered distance without a continuously running propeller, which would have demanded far more electrical power over a journey lasting months.
That did not mean the crossing used no energy. The pump, steering, navigation, and onboard electronics still required power. The advantage was that the ocean supplied the forces doing most of the moving: buoyancy and gravity drove the climb-and-dive cycle, while the wings shaped that motion into a glide.
The Tradeoff Behind the Crossing
An underwater glider is not built for speed. Its gentle pace is the price of conserving energy, and its route depends on managing a vehicle moving through currents rather than steering a fast, direct course. But it can remain at sea far longer than a conventional propeller-driven underwater drone carrying a comparable energy supply.
For the Scarlet Knight, the essential design choice was to stop trying to power every meter of forward motion. By repeatedly adjusting its buoyancy, it turned a small internal change—moving oil in or out of a bladder—into another long stretch of travel across the Atlantic.
