Improving Productivity of Low-Altitude Airspace: Speed vs Direction Control

Emerging unmanned aircraft systems (UAS) operations propose to introduce flights orders of magnitude higher than what the airspace handles today. What type of onboard control for enroute separation assurance increases productivity without compromising safety in the low-altitude airspace? This article quantifies the impact of two conflict detection and resolution approaches - pure speed control and pure direction control - on airspace productivity. We focus on small UAS traffic for goods movement in low altitude (under 400 feet) airspace. We compute three types of metrics, namely throughput, travel time extension and energy consumption, from simulations of unmanned traffic over a representative square area. As the inflow rates are increased, the corresponding outflow rates (throughput), travel time extensions and energy consumption for each type of control are measured. A representative power consumption model is developed for aircraft with both kinds of control. Without compromising safety, both direction control and speed control are equally good, unless the UAS are designed to be highly efficient while hovering. If the UAS have a hover power consumption that is equal to or less than one and a half times the minimum power consumption, speed control increases airspace productivity more than direction control.