I took advantage of the quieter period between Christmas and New Year's Day to pursue one of my favorite relaxation pastimes: reading up on the Apollo lunar-landing missions and the space program. This time, it was Angle of Attack: Harrison Storms and the Race to the Moon by Mike Gray; (thanks to our regular columnist and author Jack Ganssle for recommending it). It's a dramatic recounting with a heavy emphasis on personalities. (note: I found Angle of Attack entertaining while offering some new insights, but not as technically informative or as other books I have read, see my list at the end—plus it doesn’t have a single photo, drawing, or graphic image of any kind, which is pretty amazing, given the subject!).
In reading the book, I was reminded yet again how radical ideas which at first seem contrary to the objective can become the only viable solution to a very difficult, if not apparently unsolvable, problem. In Angle of Attack, the author explains how from the start, the lunar-mission design team knew right from the project beginning that re-entry would be problem, well before the rest of the mission architecture was worked out. The problem is simple to explain: coming back at several thousand miles per hour, the Earth's atmospheric friction will cause the capsule skin to heat up to about 2200°C (4000°F), thus weakening or melting the capsule and cooking the occupants.
The design teams worked on all sorts of configurations for super-streamlined capsules, basically very narrow tubes, to minimize drag and friction and thus heating. After all, this was what aerospace engineers did for aircraft, especially as they went supersonic (see the SR-71 for a great example). They also looked for materials and alloys that could withstand the heat. But they found no shape that provided drag coefficient that was low enough, and no material that was sufficiently light and also strong. The "best" shapes they developed would have put the astronauts one behind the other in an extremely skinny capsule that was impractical except as a return sled, and even that wouldn't survive reentry.
The solution consisted of looking at the problem in a very different way. What if, instead of trying to reduce the drag to a minimum, the capsule was designed with a broad, slightly rounded bottom which would have high drag, thus slowing down the re-entry speed, while a sacrificial heat shield on the bottom burned away? In addition, as the heat shield ablated, it would develop a bow wave--an insulating buffer zone, in effect--in front of itself, one that would keep some of the friction-producing atmosphere away from the capsule,
As we all know, that high-drag design was used, and it worked as predicted, while allowing a capsule form-factor that was much more useful than a skinny tube could ever be. It was an approach that was very much contrary to initial conventional thinking.
Have you had a problem where a solution which is not just an elegant extension or refinement--and which at first seems counter to logical thinking or maybe even a little crazy--ends up as the one that is chosen? Where a crazy idea which seems contrary to the objective actually does the job? Or where a designer even has to endure some ridicule and scorn for such unconventional thinking, until he or she is vindicated? ?
My favorite "Apollo" books:
- Apollo: The Race to the Moon, by Charles Murray and Catherine Bly Cox
- Digital Apollo: Human and Machine in Spaceflight, by David A. Mindell
- Stages to Saturn: A Technological History of the Apollo/Saturn Launch Vehicles, by Roger E. Bilstein