Due to the long-duration and long distance nature of future exploration missions, coupled with significant communication delays from ground-based personnel, NASA astronauts will be living and working within confined, isolated environments for significant periods of time. This extreme environment poses concerns for the flight crews' ability to maintain cohesiveness and teamwork. If teamwork behaviors (i.e., communication, coordination, and collaboration) and cohesion are impacted, the mission success and crew safety can be threatened. Teamwork training is critical to ensuring that team cohesion and performance are maintained. Yet, delivering this training is challenging, as spaceflight crews are geographically dispersed across the globe and often train on different schedules. Designing and implementing an eLearning teamwork skills training, which can be delivered asynchronously, is a valuable and necessary initiative. However, questions remain regarding the most effective strategies, sequence and scope for team training. This design-based research constructed and validated a computer-based instructional unit for teamwork skills training, using the educational research and development model. The unit was validated through a formative evaluation process consisting of preliminary and main field-testing. The testing utilized an expert review methodology in which teamwork training subject matter experts at NASA, instructional designers and trainers at NASA, and experts on the astronauts at NASA evaluated the prototype. Upon analyzing the results and feedback, revisions were made to the prototype. The overall results of the data collection stages of the process indicate that a relevant, beneficial and potentially effective teamwork skills training unit was created. The educational research and development process resulted in the development of a teamwork skills training program that is ready for operational testing and dissemination. Additionally, a detailed example of adherence to instructional design principles and processes is provided. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]