UltraSail was conceived of in 2003 by the CU Aerospace / University of Illinois team and is an ultra-large, ultra-lightweight, square-kilometer class solar sail concept with spinning blades capable of performing a variety of interplanetary and Lagrange point missions on timescales comparable to other existing low-thrust technologies. A primary advantage of UltraSail is the ability to deliver payload mass fractions as high as 60%, thereby enabling smaller launch vehicles to be used and correspondingly lower launch costs.

CU Aerospace and the University of Illinois are currently contracted to build a low-cost flight experiment based on the UltraSail concept. This experiment, called CubeSail, uses two CubeSat satellites to deploy a 20 sq. meter solar sail, followed by a demonstration of orbit raising using solar photon momentum transfer.