LETTER: Re-entry Flashback

When I heard Saturday that the North Korean ICBM did nor survive re-entry, I had a sixty-year flashback.

From 1956 until 1962 I worked at the Langley Aeronautical Laboratory of the National Advisory Committee for Aeronautics (NACA), which in 1959 became the Langley Research Center of the National Aeronautics and Space administration (NASA). We were trying to figure out how to make missiles and spacecraft survive the intense heating of re-entry.

We tried thick copper nosecones (worked up to a point, but they were too heavy), titanium (reacts with nitrogen and burns), zirconium oxide (brittle and heavy, but zirconium oxide foam was developed for the space shuttle skin), transpiration cooling (plumbing heavy and unreliable), pyrolytic graphite (a variation was used for the space shuttle leading edges), thorium oxide (radioactive), molybdenum (heavy; burns in air when hot), molybdenum protected by a silicide coating (used for some applications), etc. etc. We settled on a thermosetting plastic reinforced by quartz fibers (later replaced by quartz microballoons) for the Mercury, Gemini, and Apollo spacecraft. It’s called ablation material. The plastic chars, outgasses, and radiates heat away.

We tested these materials in hot air jets and on the noses of multi-stage rockets using surplus military solid propellant boosters. We had a six-stager that fired thee stages up and three back down to produce the extreme heating of re-entry. We burned up a lot of nosecones.
The stuff we did is mostly in the public domain now; apparently the North Koreans didn’t read about it. Or maybe their dictator copied Hitler, who delayed the first jet fighter, the Me 262, by objecting to its use of the US-developed tricycle landing gear.

The North Koreans do not yet have an ICBM capable of reaching the US. It not only has to get up and over; it must get back down intact!

Jerry L. Modisette
Cabezon Canyon

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