Using the NASA ER-2 aircraft, based at the NASA Dryden Flight Research Center in California, researchers measured radiation at altitudes between 52,000 and 70,000 feet. This radiation data is being used to characterize and define the radiation environment for both crew members and the frequently flying public on future HSCTs. The broad aim of the ER-2 flight measurements campaign was to understand the composition, distribution and intensities of cosmic and solar radiation at commercial supersonic transport cruise altitudes. The primary concern is the level of uncertainties in the knowledge of the upper atmosphere's radiation environment and the biological response to that type of environment. A second purpose of the ER-2 testing was to develop and validate techniques and monitoring devices for the protection of crew members who may work many hours at cruise altitudes up to 68,000 feet.
Researchers believe that long-term radiation exposure can be managed by crew rotation scheduling.
The resolution of these environmental issues has been a centerpiece of the HSR Program since its inception in 1990. Great strides have been made in understanding these issues and their potential impact on the HSCT design, its propulsion components and on HSCT operational procedures. Even the routes flown by the airplane could be influenced by the desire to ensure that this airplane does not pose any hazards to the environment, or human and marine populations. These environmental principles are now firmly rooted in the HSCT development process. As new aeronautical technologies are introduced into the evolving HSCT design, the engineering team must test each new concept for its ability to meet the environmental constraints.