Chair Force Engineer

Tuesday, December 09, 2008

DynaSoar Extinction

No single name curdles the blood of space enthusiasts like that of Jeffrey Bell. The University of Hawaii professor and "recovering pro-space activist" often lends a cynical commentary that douses water on the dreams of NASA-lovers and NewSpacers alike. While I can't say that I always agree with Dr. Bell, he crafts a rational argument and often serves to inject a dose of harsh reality into the kool-aid drinkers who deal effective setbacks to space programs by peddling unrealistic fantasies.

In his new piece, Jeffrey Bell strikes back at the “Cult of the DynaSoar,” the aviation enthusiasts who lament the cancellation of the Air Force spaceplane program of the 50’s and 60’s. I will admit that I would probably be labeled as a member of the DynaSoar cult, based on my past polemics about how we needed the X-20, or something like it, to blaze the trail for the operational Space Shuttle. Part of it stems from a desire I share with Dr. Bell, the belief that a small-scale spaceplane demo would have steered decision-makers away from many ill-fated design choices during the Space Shuttle program. Another part of it stemmed from my lack of appreciation for how ineffective the DynaSoar thermal management system was. I didn’t read about the silicon coatings or the liquid hydrogen tank that was essential to keep the cabin cool until Jeff Bell brought attention to them.

Admittedly, DynaSoar was clearly an extreme example of undisciplined requirements creep leading to the death of an acquisition program. Conceived as a suborbital bomber, it evolved through four stages into an orbital spaceplane. The personnel who set goals for the DynaSoar program must have been unaware of the materials science realities of the time. It was a shining example of how a bad acquisition program is run.

If DynaSoar would have served as an example of how not to build a reusable spacecraft, and if the Space Shuttle has served as an example of how not to build a reusable spacecraft, then what approaches are left to try? The shuttle’s thermal protection system is effective but fragile. DynaSoar’s thermal protection system was impractical but robust. But Shuttle and DynaSoar are both examples of what would be called “dense” reentry vehicles. Perhaps the solution is to design a vehicle that carries its propellant tanks to orbit, ensuring that it will have a low wing loading (and low heat loading) when it hits the atmosphere. It would be able to get away with a robust metallic thermal protection system because it would be so “fluffy” that heating would be reduced. That was one of many goals in the X-33 program. And because I brought up X-33, that will undoubtedly be the subject of Jeff Bell’s next polemic.