Direct measurements of cosmic rays using balloon borne experiments

Direct measurements of cosmic rays with balloon-borne detectors are used for understanding cosmic ray origin, acceleration and propagation, as well as exploring the supernova acceleration limit and searching for exotic sources such as dark matter. The energy reach of direct measurements is currently limited to ∼1015 eV by the detector size and exposure time, but incident particles are identified element-by-element with excellent charge resolution. A challenge of balloon-borne experiments is that the detectors must be large enough to collect adequate statistics, yet stay within the weight limit available for balloon flight. Innovative approaches now promise high quality measurements over an energy range that was not previously possible. Recent results and their implications are reviewed. The outlook of existing and future experiments is also discussed.