原创 The Space Shuttle program in review

Hindsight is one of those things which separates humans from other species: as far as we know, they don't have next-day meetings to tackle how the previous day's hunt went. Being human, though, we do like to look back, assess, and analyze.

These reviews usually fall into one of two broad categories: as a learning experience (what did we learn, anticipate/not anticipate, do smart/not-so-smart, and react properly/incorrectly) or an opportunity for grandstanding and finger-pointing by pseudo-experts who really haven't got a clue (why didn't you anticipate 'x', how could you have not known about 'y', shouldn't you have done 'z'). As engineers, we try to focus on the former, of course.

The end of the Space Shuttle program this year is a good opportunity for hindsight and review. First, some basic statistics about the fleet of five shuttles (now down to three, due to the loss of Challenger in 1986 and Columbia in 2003):

- Flew 135 missions
- Made 20,000 orbits of Earth
- Carried 363 people (some multiple times)
- Burned 660,000 pounds of solid fuel and 45,000 gallons of liquid hydrogen per minute at peak thrust
- Accelerates to 17,500 mph in 8.5 minutes
- Cost 14 astronaut lives
- The longest mission lasted 17 days.

Before we assess the Space Shuttle program, let's get the tragic loss of two shuttles and their crew members out of the way. Despite planning, precautions, and attempts to anticipate and minimize risk, there is no avoiding the reality that rocketry, space flight, and their associated activities are risky business, and everyone knows that. If you want a guarantee that nothing will go wrong—and if it does, no one will get hurt—you might also be interested in a bridge in Brooklyn I own and can sell you cheap.

Looking back to the origins of the shuttle program, it was presented as a low-cost, relatively simple, largely re-usable, frequent "cab service" to low-Earth orbit. Reality was, of course, quite different, with each flight a challenge of pre-flight logistics, maintenance and upkeep issues, and an extraordinarily complex "flying" machine. [Some Apollo-program engineers, such as Homer Hickam (author of the autobiographical book Rocket Boys, later made into the movie October Sky), maintain that the basic design of a manned shuttle strapped to the side of the booster, rather than the top, was inherently flawed and foolish, and extremely dangerous.]

Where to start?

- Was the original proposal unrealistic because it was tailored to meet politically correct and attractive-sounding goals?
- Or was it actually a lack of true understanding of what such a program and vehicle would really require?
- Was the basic concept of a vehicle that could be used in orbit, but also land on its own like an airplane (or flying brick, some have called it), fundamentally too much of a compromise?
- Did the program spur many basic or applied technologies, much as the Cold War and the Apollo program did?
- Was it worthwhile because it kept so many scientists, engineers, and other skilled staff employed, and added to the overall skill set and knowledge base?
- Did it consume resources (mostly money) that NASA could have used for other space programs, or even successor craft and programs?
- Did it inspire young people to consider technology careers, rather than hoping to become sports stars or rappers?

This list of questions can go on much longer. Certainly, the shuttle did not accomplish many of its original goals. But it also did things that were not on its agenda, such as the complex repair of the Hubble Space Telescope with that incorrect lens construction (there's another long and sad story) which required developing a deep understanding about the challenges of doing real work in space, well beyond doing earth-science data acquisition from a convenient platform way up high.

The answers to questions on the value of the program are complex, not simple black-and-white, and it is probably too soon to have the needed broader perspective and retrospective understanding. But it is not too early to at least start thinking abut it.

What questions would you add to the list? What are your thoughts on the good, bad, and even ugly of the Space Shuttle program, in terms of the various perspectives and priorities?