it was not until the mid-1970s that the air force launched an ambitious program to reduce radar observability to near zero, resulting in the lockheed f-117a and northrop b-2. what made them possible were breakthroughs in the three cs: computers, composites, and coatings. computers solved the stability problem because they can automatically analyze problems and make flight corrections in microseconds. if computers make low-observable shapes flyable, then composites make them light and strong enough to get off the ground they give designers much greater specific strength and modulus than metals, making possible designs that would otherwise be unworkable along with composites and computers, a third breakthrough came in coatings, and radar-absorbing material (ram) coatings in particular like carbon fibers, ram coatings absorb radar waves by converting their electromagnetic energy into motion. the ram coatings developed by tdk and nippon electric use ferrites, ceramic magnets that are lighter and better microwave absorbers than metals. plessey microwave materials has developed ram products that are either magnetic or dielectric absorbers magnetic absorbers consist of a rubber, polyurethane, fluoroelastomer, or silicone matrix loaded with ferrites or graphites. these bleed off radar energy by vibrating when they come in contact with the magnetic component of an electro-magnetic field. plessey's second class of ram, dielectric absorbers, have graded electrical properties. while their surface impedance closely matches that of air, it gradually rises to sap the energy of a radar pul