Unfortunately, many of those lessons are false. If they are believed and applied, they will result in human spaceflight, at least as performed by NASA, that remains expensive, unsafe and rare. Here are some of the more important things many people learned from the shuttle program that are just plain wrong:
1. The Shuttle Proved That Reusable Launch Vehicles are Not Cost Effective
This is a pernicious myth one that has driven NASA policy for years, since the failure of the X-33 program and through former NASA head Mike Griffin's policy of reverting to expendable systems with the now-canceled Constellation program. But the reality is that the shuttle taught us nothing about the cost of a properly designed, fully reusable launch system, because that's not what it was.
The external tank was thrown away on each flight, and the solid rocket boosters had to be rebuilt every mission. The only "reusable" part of the vehicle, the shuttle orbiter itself, required extensive inspection and maintenance between flights, with a vast army of technicians costing billions per year. These high costs and headaches were not the result of any intrinsic technical issues with reusable vehicles, but were caused by penny-pinching during development in the 1970s. Spending more then could have created a truly reusable vehicle later. But it is always easier to slash budgets now and let some future politician have to worry about operational costs down the road.
2. The Shuttle Proved That We Must Move Beyond Chemical Rockets
The perennial myth is that we simply can't cut the costs of going to space if we're still using rockets. If the most cost-effective rocket-propelled vehicle possible the space shuttle couldn't do it, the thinking goes, it must be time to give up on them. The flaw in this argument is that, as noted, the shuttle wasn't a very cost-effective rocket. And, people who make this argument assume that the high cost of rocketry is all of the fuel that is expended, but in fact fuel costs are typically only about 1 percent of the total operations cost for a rocket-based launcher. Compare this to 30 or 40 percent for an airliner, and it's clear that with reusable rockets, there is a lot of room to bring down costs if we can get the traffic level up. Indeed, if SpaceX really does build its new Falcon Heavy in the next couple years, it will reduce the cost to a thousand dollars per pound (that's more than ten times less than the shuttle costs, and considerably less than other expendable vehicles, such as the Atlas and Delta).
3. The Shuttle Proved that Cargo and Passengers Should Travel on Different Vehicles
After the Challenger accident in 1986, many observers argued that the shuttle should stop risking astronauts's lives delivering satellites that could be launched on unmanned vehicles. After the Columbia loss in 2003, the argument went further: that crew and cargo shouldn't be mixed on a launch.
But this isn't a philosophy that we use with any other form of transportation. Every airliner carries both passengers and cargo, and even cargo transport flights have a flight crew. The real lesson isn't to separate crew and cargo, but to design the launch systems to be more reliable, because both crew and cargo are far too expensive to lose. (And in the case of a reusable vehicle, the vehicle itself is too expensive to lose, even if it flies empty.) One of the reasons that the shuttle was retired was that there were only three left, so each flight put a third of the fleet at risk. Ultimately, this was simply unaffordable.
4: The Shuttle Proved that NASA Should Have Stuck with, and Should Return to, the Safe and Successful Architecture of Apollo's Heavy-Lift Vehicle and Crew Capsule
It is tempting to look at the 1960s as a golden era of spaceflight, when we had great accomplishments in space and no loss of crew on a space mission (the Apollo 1 fire that killed three astronauts happened in a test on the launch pad). But each mission to the moon cost billions in today's dollars, and we came very close to losing a crew on Apollo 13. While the mission team deserves applause for returning the crew safely, there was as much luck involved as skill. Had the liquid-oxygen tank explosion occurred on the way back from the moon, instead of on the way to it (when they still had the lunar module as a backup), they would have died. In fact, one of the main reasons for ending Apollo before all its hardware was used (there were at least two Saturn Vs left over) was that many running the program feared that deaths in space were inevitable if it continued much longer, with terrible effects on the program.
There is nothing intrinsically safe about capsules, or dangerous about wings. They both have their advantages and disadvantages, and the only real way to find out which is best is to actually try multiple approaches. Fortunately, that's now happening. Three of the competitors for NASA's commercial crew program SpaceX, Boeing and Blue Origin are using capsules with parachutes, and oneSierra Nevadaplans to use a lifting body and land on a runway. Since they're all commercial crafts, hopefully the market will determine which approach is best for which missions, not mistaken lessons from the shuttle.
5: The Worst Result of the Shuttle Program was the Death of 14 Astronauts
No doubt, the loss of the crews of the Challenger and Columbia was tragic. But risk is unavoidable in spaceflight, and there is no shortage of people willing and able to do that job even knowing the danger. I would argue that the fact that the nation itself grieved so extensively for them is actually a bad signan indication that we don't think that space is an important enough frontier on which to risk human lives, even though no frontier has ever been opened without such a cost.
From a space policy perspective, the real problem with the shuttle program was that it failed in its promise to make space access affordable and yet we stuck with it for three decades. It was a huge lost opportunity in terms of time, the ultimate irreplaceable commodity.
6: The Ultimate False Lesson: That the Space Shuttle Proved Anything at All
To draw any firm lessons at all from the space shuttle by itself is a fundamental flaw in logic; it is called the fallacy of hasty generalization. Simply, the fallacy is extrapolating to some inductive conclusion from insufficient data. And in this case, there is a single data point: the shuttle.
We can learn from history, but we have to grab a much bigger bite of it than any one example. If we consider the entire history of U.S. human spaceflight, there is a useful lesson to be learned. That is: What we are doing in space is too important to leave to a single monopoly system, developed and run by a government agency. Twice in the past three decades the shuttle was shut down for years, leaving us without the capability of getting into space because there was no alternative, or competition. The Space Launch System that NASA is now planning to build to Congressional specifications (without sufficient funding or a stated mission) will suffer from the same problem. It' s time to open the entire national space transportation infrastructure to competition, to give us robust, redundant capabilities and stop looking for the next space shuttle.