If you have ever watched an object enter the earth's atmosphere from space, you have seen the intense radiation as the friction between the object and the atmosphere generates heat and light. The space capsule has to be lined with a material which can withstand this intense heat.
This story has to do with how beryllium heat sinks for the first Project Mercury space capsules were produced. The heat sink was the end of the capsule which took the heat generated when the capsule re-entered the Earth's atmosphere. Beryllium was chosen for its low density and high heat capacity.
Beryllium comes from a long chemical process which starts after beryl ore is melted in an electric furnace. The metal comes from a reaction between beryllium fluoride and magnesium. The cast beryllium is ground to a fine powder in an attrition mill between beryllium discs.
Metallic beryllium is produced by sintering fine beryllium powder in a vacuum furnace at about 2000 degrees F under mechanical pressure of about 100 psi. The furnaces in the Cleveland plant of the Brush Beryllium Co. (now Brush Wellman) were externally gas fired steel or stainless steel horizontal cylindrical retorts. The pressure was applied by rams which entered the retort through packing glands. As steel has very little creep strength at that temperatures, the retorts eventually collapsed and were replaced at great expense.
Brush was called on to make beryllium reflectors for the nuclear reactors for the Nuclear Energy Propulsion of Aircraft (NEPA) program. This program never got off the ground (disgusting, shallow pun intended). But it lasted long enough for Brush to build a furnace/press large enough to make 5 ft. diameter blanks.
I was a callow youth, a boy engineer in the mid '50's, working for Brush in Cleveland, Ohio. I was sent to Luckey, Ohio to the plant in which beryllium was extracted from beryl ore. For the NEPA program, I proposed buying a large electric resistance heated vacuum furnace, to be placed inside an hydraulic press. The pressure ram would enter the furnace through a corrugated stainless steel bellows. The head of the press had to be rolled aside to allow the die and the can of beryllium powder to be placed into and removed from the furnace. I designed and built the furnace/press installation, with the tremendous assistance of John Sofyanos of Sofyanos Associates of Toledo. At one point during the construction, a 2300 volt electric cable was uncovered. I called Bob Cline, the chief engineer, and asked him what to do about it. "Treat it with respect" was his answer.
At any rate, when Project Mercury came along here was Brush with a nice large furnace/press capable of producing the heat sink blanks. The beryllium powder was very carefully introduced into a steel can. The can was placed in a steel die assembly consisting of a cylindrical base and doughnuts flame cut from 12 inch thick steel slabs. The mold release agent was alundum powder introduced between the can and the die. It took a week or more to heat up the furnace, sinter the blanks, and cool down. The steel can was chipped away from the blank. The blanks were acid washed, density checked (the ancient Archimedean method, weighing in air and water) and x-rayed to check for porosity. The blanks were then sent off to the Alcoa plant in Cleveland to be forged out to six feet in diameter. The finish machining was done on a horizontal boring mill at Luckey.
Later in the Mercury program a different technique was used to absorb and dissipate the heat generated during re-entry. The heat sinks were a honeycomb material filled with a material which would melt and disintegrate. The material which ablated took the heat with it.
Lest it be thought that I was the only person involved, let me mention some of the other players: Gene DeJarnette, my immediate boss; Robert Cline, Chief Engineer and Mayor of Luckey, Ohio ("vote early and vote often"); Carl Schwenzfeier, VP Engineering; Dean Rapprich, Mgr Production; Henry Schaffner, VP Production.
Mercury capsules can be viewed at the National Air and Space Museum in Washington, DC. I like to tell people they are my exhibits in the Smithsonian.
PostscriptWe recently visited my wife's sister in a retirement home in Los Gatos, California. She casually mentioned that there was a Mr. Leverett there in the assisted care unit. He turned out to be Dr. Miles C. Leverett, who had been in charge of the NEPA Project. I was astounded. We met. What a family reunion! Our common ancestor was William Leverett, who was born in 1773!