The Design · DARPA Heavy-Lift Challenge

A 1950s idea,
solved for today.

The tip-powered rotor, reborn for heavy lift.

We took a proven concept the aerospace world set aside seventy years ago and made it work — because the three things it always needed, modern batteries, modern control systems, and modern manufacturing, finally exist.

The Concept

Power the blade tips, not a shaft.

A conventional helicopter spins its rotor from the center. That forces a heavy transmission, a driveshaft, and a tail rotor whose only job is to cancel the torque the engine creates. Our aircraft drives the rotor from its tips instead. With thrust applied at the tips, there is no reaction torque to fight — so there is no tail rotor, no central transmission, and no central fuselage.

Tip-powered rotorcraft were built and flown in the 1950s. They were never practical then. What changed isn't the aerodynamics — it's everything around it: high-density batteries, precise electronic motor control, and flight computers fast enough to hold a delicate balance in real time. We found that balance through a combination of simulation and physical testing, and added our own refinements to make the concept excel at one thing in particular: lifting heavy loads.

"The idea was never wrong. The world just hadn't caught up to it yet."
Revolutionary Aerodynamic Design

Lift comes from disc area — so we chase diameter.

A rotor's ability to lift is governed by disc loading — weight carried per unit of swept area. Lower disc loading means more lift for less power, and a gentler, more efficient downwash.

Here's the leverage: making the rotor bigger is mostly a one-dimensional increase in blade length, but swept area grows with the square of the radius. A little more length buys a lot more disc. That single geometric fact is why a large-diameter, tip-powered rotor is such an efficient heavy lifter.

The tip-battery trick

We place the batteries out at the rotor tips. That does two jobs at once. It puts the power source right next to the motors that need it — no long, heavy runs of conductor to the center. And the mass at the tip dramatically increases centripetal force, which flattens the blade's coning angle. As the cone flattens, that centripetal force carries more of the load and offsets the lift, so the bending moment at the blade root practically disappears — and the blade root can be lighter. Less structure, more payload.

hub coning angle Tip mass ↑ centripetal force → coning angle cancels root bending moment lift centripetal
Batteries at the tips flatten the coning angle until the blade root is practically moment-free.
Revolutionary Powertrain Design

Propellers at the tips. Electric, distributed, and fault-tolerant.

Thrust at the tips → no reaction torque ✕ no tail rotor ✕ no transmission ✕ no central fuselage
Each tip is a self-contained propulsion unit: propeller, motor, and battery.

We drive the tips with propellers, not jets. Tip-jets are simple but thirsty; propellers are far more efficient, and efficiency is what turns a curiosity into a working heavy lifter.

Because each tip carries its own propeller, motor, and battery, the propulsion is fully distributed. There's no single point of failure at the center of the aircraft to lose.

Battery vs. fuel — matched to the mission

Fuel-powered tip-rotors can claim longer range, and we expect to see them at the competition. But our high-efficiency large rotor sips power, so on the challenge's 5 nmi profile batteries are the best choice: cleaner, quieter, simpler, and more controllable. For missions that demand more range, the same airframe accepts a fuel-powered variant — so the platform scales with the customer's need rather than locking them in.

Flight Test

95 lb payload, flying.

A tethered powered-lift test carrying a 95 lb payload — roughly 3× the aircraft's empty weight — in spin mode.

The Evidence

Endurance we've flown, not just modeled.

Two clean weight-bearing hovers — at 45 and 65 lb, on on-board telemetry — anchor our hover-power model, so the curve below is measured-in rather than simulated. The 5 nmi mission closes today at 4.3–4.9× the aircraft's empty weight, and 5× clears with 7–27% margin — with headroom to 5.2–6.0× as efficiency and mass improve.

0102030405060MINPAYLOAD MULTIPLE (× AIRCRAFT EMPTY WEIGHT)MISSION FLOOR · 5 nmi @ 25 mph = 13.8 min4.3–4.9×TODAY5.2–6.0×IMPROVED45 lb FLOWN28.4 g/W65 lb FLOWN23.7 g/WFLIGHT TESTED45 & 65 lbWeight-bearing hovers, on-board telemetryMODELED · TODAY4.3–4.9×Mission-capable payload multipleWITH IMPROVEMENTS5.2–6.0×+17% efficiency, −7% airframe massMISSION COMPLIANCE5× clears with 7–27% marginHover power P = 1,860 W × (total weight / 97.4 lb)ⁿ, n = 1.50–1.77, anchored on flight test.Measured packs 3 × 434.7 Wh = 1,304 Wh (1,174 Wh usable), 4.19 kg · multiples are payload ÷ that configuration’s empty weight.Grey points: two flights flown on stalled propellers, excluded from the fit — a propeller selection since corrected.
The Problem Everyone Else Has

Solving the empty-handed flight problem — gracefully.

A big, low-disc-loading rotor is a superb lifter. But with no payload it's sluggish: it can't reposition quickly, and a stiff headwind can pin it in place and keep it from completing a mission. Every large tip-rotor faces this. We expect other tip-powered aircraft at the competition — but we haven't seen one that solves the unloaded case as cleanly as this.

LIFT MODE rotates · lifts heavy ground convert CRUISE MODE fixed wing · ~60 mph
A ground conversion turns the rotor into a non-rotating, T-shaped tilt-wing airplane.

Two aircraft in one airframe

On the ground, the aircraft converts into a T-shaped tilt-wing airplane. The rotor stops spinning and becomes a fixed wing; the same tip propellers now pull it forward as a conventional aircraft at roughly 60 mph.

The result: it lifts like a large rotor when there's a load to move, and it flies like an airplane when it needs to cover ground empty or punch through wind. One airframe, two flight regimes, and no compromise forced on either.

Built to keep flying when things go wrong.

Fault tolerance & autorotation

  • Loses a motor — or two — and keeps flying, with reduced payload capacity rather than a crash.
  • Can autorotate like a helicopter, gliding down safely on rotor inertia if power is lost.
  • Far safer than a typical multirotor, where losing one motor can mean losing the aircraft.

A flight controller built for the spin

  • We built a custom flight controller to manage the unique dynamics of the rotating, tip-powered lift mode.
  • It is paired with a traditional flight controller for the fixed-wing cruise mode.
  • The two work together so the aircraft is stable and controllable across both flight regimes.
Most Promising

An efficient heavy lifter the market is waiting for.

Efficient, scalable vertical heavy lift opens doors that today's aircraft can't afford to. The heavy-lift drone is the first step.

Low disc loading = efficient lift
2
Flight modes, one airframe
0
Tail rotor · transmission · fuselage
±
Battery or fuel, per mission

Near term

Precision crop spraying, remote-area delivery in places like Alaska, and defense logistics — missions defined by moving real weight to hard-to-reach places.

Scalable

Lift scales with rotor diameter, and range scales with the choice of battery or fuel — so one design language serves many payloads and ranges.

Long term

The same efficient-lift thinking points toward airborne wind energy — power generation aloft to help meet the enormous energy demand of AI data centers.

Designed with AI, engineered by a third-generation team of aircraft builders, and backed by Turner Systems. AI + Aerospace + Turner Systems = opportunity.