The Secretary of Defense and the Secretaries of the military departments may each buy ordnance, signal, chemical activity, transportation, energy, medical, space-flight, telecommunications, and aeronautical supplies, including parts and accessories, and designs thereof, that the Secretary of Defense or the Secretary concerned considers necessary for experimental or test purposes in the development of the best supplies that are needed for the national defense.

Purchases under this section may be made inside or outside the United States and by contract or otherwise. Chapter 137 1 of this title applies only when such purchases are made in quantities greater than necessary for experimentation, technical evaluation, assessment of operational utility, or safety or to provide a residual operational capability.