It's my understanding that the F-16 or F-104 (maybe both) were designed so a complete engine swap was possible (by experts) in 20 minutes. I attended a lecture by Buzz Aldrin where he presented a second generation shuttle concept based upon an airframe and thermal protection system designed like a suit of clothes that could be put over any sort of propulsion system. I think the concept as presented by Dr. Aldrin was flawed for reasons of mass fraction (got to keep it low). However the idea of having one basic airframe on a TSTO that could be used either on a booster or an orbit vehicle through interchangeable cores is a good concept.

On the subject of automobile reliability: My household has three cars. My wife drives a very practical and economical 1996 Saturn SL-1. I own two old cars, i.e. a 1964 Rambler American (my daily driver) and a 1968 Karman Ghia (my fun car). My wife's car is a miracle of modern technology, i.e. a modestly priced, reliable car, that burns very little gas (32 miles/gallon) and causes little air pollution. Her car does this by using an electronic ignition and fuel injection system that is monitored by a range of sensors, e.g. oxygen sensor on the exhaust manifold, mass flow, barometer and temperature sensors on the intake, crank angle sensor, etc. The complete engine operates on a closed loop feedback system controlled by a self diagnostic Power train Control Module (PCM). The PCM is based upon the Motorolla 68HC11F microcontroller. By the way, some people like to say the only spin-offs from space exploration was trivial stuff like Tang, Teflon, etc. Baloney! Modern automobile engine systems are pure rocket science lifted directing from aerospace applications.

Anyway, my wife's car is a marvel. Unfortunately, fixing it when something does go wrong is a major pain in the rear. In stark contrast, my 1964 Rambler American is trivial to work on. For example, I can replace the generator on my Rambler faster than I can replace a tire (it took me 4 hours to replace the alternator on the Saturn). It takes about 45 minutes to replace the water pump on my Ramber but to replace the water pump on the Saturn is an all day job. Of course, I'm alway fooling around with the Rambler because the car has no intelligence and does not use a closed loop control system. That's the trade off. If you make a car super simple then it's easy to fix but you're always fooling with it. On the other side of the coin, you can design a car to be super sophisticated such that it runs trouble free for years. However when anything fails, you have to junk the entire car because it's too difficult to fix. People argue back and forth about the merits of these two design philosophies. However I find myself wondering if there will be any 1996 Saturns on the road in the year 2035? There is a good chance that my 1964 Rambler will still be running then.

Gary