Editing Cosmic ray (section)

===Direct detection===
Direct detection is possible by all kinds of particle detectors at the [[ISS]], on satellites, or high-altitude balloons. However, there are constraints in weight and size limiting the choices of detectors.

An example for the direct detection technique is a method based on [[nuclear track]]s developed by Robert Fleischer, [[P. Buford Price|P.&nbsp;Buford Price]], and [[Robert M. Walker (physicist)|Robert&nbsp;M. Walker]] for use in high-altitude balloons.<ref>{{cite book|author1=R.L. Fleischer|author2=P.B. Price|author3=R.M. Walker|date=1975|title=Nuclear tracks in solids: Principles and applications|publisher=[[University of California Press]]|bibcode=1975ucb..book.....F }}</ref> In this method, sheets of clear plastic, like 0.25&nbsp;[[millimetre|mm]] [[Lexan]] polycarbonate, are stacked together and exposed directly to cosmic rays in space or high altitude. The nuclear charge causes chemical bond breaking or [[ionization]] in the plastic. At the top of the plastic stack the ionization is less, due to the high cosmic ray speed. As the cosmic ray speed decreases due to deceleration in the stack, the ionization increases along the path. The resulting plastic sheets are "etched" or slowly dissolved in warm caustic [[sodium hydroxide]] solution, that removes the surface material at a slow, known rate. The caustic sodium hydroxide dissolves the plastic at a faster rate along the path of the ionized plastic. The net result is a conical etch pit in the plastic. The etch pits are measured under a high-power microscope (typically 1600× oil-immersion), and the etch rate is plotted as a function of the depth in the stacked plastic.

This technique yields a unique curve for each atomic nucleus from 1 to&nbsp;92, allowing identification of both the charge and energy of the cosmic ray that traverses the plastic stack. The more extensive the ionization along the path, the higher the charge. In addition to its uses for cosmic-ray detection, the technique is also used to detect nuclei created as products of [[nuclear fission]].