Lift, power, endurance and signal range all follow from a handful of physical laws. We design to them from the first sketch.
01 · Momentum theory
Why bigger rotors hover longer
Pideal = T3/2 / √(2ρA)
To hold weight, a rotor must accelerate air downward. Spreading the same thrust over a larger disk area A moves more air more slowly, which cuts the power needed. This is why efficient endurance aircraft carry large, lightly loaded propellers.
02 · Rotor efficiency
Figure of merit
FM = Pideal / Pactual
Real propellers lose energy to drag, tip effects and swirl. Blade shape, tip speed and motor matching decide how close we get to the ideal. Higher figure of merit means more minutes in the air for the same battery.
03 · Energy budget
Endurance
t = η · Ebatt / Phover
Flight time is usable battery energy divided by power draw. Extra battery adds weight, which needs more thrust and more power, so returns diminish fast. Good endurance comes from balancing the whole system.
04 · Lift capability
Payload ratio
PR = mpayload / maircraft
A high ratio demands high thrust-to-weight, torque-dense motors and a structure that is both stiff and light. Our 2:1 result at the DARPA Lift Challenge came from optimising all of these together.
05 · Communications
Link budget
Pr = Pt Gt Gr (λ / 4πR)²
Signal strength falls with the square of distance. Antenna gain, frequency and placement on the airframe decide how far and how reliably a drone stays connected, which is why antenna design is core to long-range work.
06 · Thermal control
Protecting sensitive cargo
Q = U · A · ΔT
Heat leaking into a payload bay scales with its surface area, insulation quality and the temperature difference to the outside. Medical payloads are designed so the cargo stays in range for the full mission, including delays.
Estimated hover endurance
0min
0 WElectrical hover power
0 N/m²Disk loading
0 g/WThrust per watt
0Air density (kg/m³)
Assumes 80% usable battery, 85% combined motor and speed-controller efficiency, and ISA standard atmosphere. Hover only, with no wind, climb or payload manoeuvres. Real endurance depends on detailed design and conditions.