Advanced Soaring Concepts Apex


The Advanced Soaring Concepts Apex was a remotely piloted, high-altitude research sailplane developed by Advanced Soaring Concepts in collaboration with NASA's Dryden Flight Research Center. The project aimed to study aerodynamic phenomena in the upper atmosphere, particularly at altitudes around 100,000 feet, to inform the design of future high-altitude aircraft and potential Mars exploration vehicles.

Design and development

The Apex was based on a modified Schweizer SGS 1-36 sailplane, extensively redesigned to withstand the rigors of high-altitude flight. The airframe incorporated graphite/epoxy and boron/epoxy composites to achieve the necessary strength-to-weight ratio.
A distinctive feature of the Apex was its custom-designed wing, utilizing the "APEX-16" airfoil developed by Dr. Mark Drela of the Massachusetts Institute of Technology. This airfoil was optimized for stable flight in the low-density, low-Reynolds-number conditions of the upper atmosphere.
The sailplane measured approximately 22.7 feet in length with a wingspan of 41.2 feet and a wing aspect ratio of 13.6. It was designed for a target gross weight of 600 pounds and a 5-g maneuver load factor.

Mission profile

The planned mission profile involved lifting the Apex to an altitude of about 105,000 feet using a high-altitude balloon. Upon release, the sailplane would descend nose-down, transitioning to horizontal flight with the assistance of a small rocket motor. Once stabilized, it would conduct a series of aerodynamic measurements during its glide back to lower altitudes.
Instrumentation included a "wake rake" mounted behind the wing to measure drag and other aerodynamic parameters. Data collected would have contributed to the validation of computational models for high-altitude flight and the development of future aircraft operating in similar conditions.

Project status

Initially scheduled for flight tests in 1998, the Apex project faced multiple delays due to technical challenges. By January 1999, the aircraft was under construction, with delivery to NASA's Dryden Flight Research Center anticipated in March or April. However, the project was mothballed before completion.
The program saw a brief revival in 2000 but was ultimately canceled. Subsequent high-altitude research objectives were achieved through other NASA projects, such as the Helios Prototype|Helios] solar-powered aircraft, which reached altitudes exceeding 96,000 feet in 2001.