Ok, more crap fell off of Discovery's main fuel tank. Fortunately it doesn't seem to have made a difference, except to future missions. But it is indicative of the primary problem with the system...the tank is essentially a giant styrofoam thermos designed to keep the liquid oxygen and hydrogen that are the shuttles fuel cold enough to remain liquid. (-312 degrees F). The foam on the outside not only helps insulate the contents, but it prevents the formation of potentially dangerous ice as a result of the humid Florida air. Of course we have a classic catch-22 here. Lose the foam and you have ice that can fall off during launch and damage the orbiter. Keep the foam, and you have foam that can fall off during launch and damage the orbiter. What to do...what to do?
Fortunately there are solutions, but they are somewhat painful. Retire the shuttles and build something new. That has been in the works for some time now, but the work has been going very, very slowly. There were numerous, well publicized failures in the last decade or so. The X-33, X-34, and Delta Clipper projects were all terminated in the early 2000's with very little progress made. These were all SSO(single stage to orbit) vehicles, looking to further the near-total reusability paradigm that was the genesis of the STS program.(Space Transport System is the shuttle's real name) Unfortunately that ideology is exactly why the shuttle never worked as well as it was planned.
Orginally the shuttle program was to see several launches per month, often with more than one vehicle in orbit at once. Alas, that never happened. The reality is that space flight is a very dangerous proposition, and a very expensive one. Plus the abuse a vehicle recieves during launch and re-entry is staggering. The shuttle is a very, very complex machine that uses technology that was state-of-the-art in the '70s. Rather than being easier to launch, recover, and refit than Apollo capsules it has proven to be just the opposite. It costs somewhere in the vicinity of $30 million per ton of cargo, compared with $3-5 million for more traditional boosters, and takes months of refit time to make flight-ready again. And she is only good for low Earth orbit (LEO). The shuttle was never designed to get to the Moon. Once the ISS is complete, NASA plans to retire the program, but a true successor has yet to surface.
There are two contenders in the race to build the next manned transport system. Not surprisingly they are Lockheed Martin, and Boeing. I'm rather partial to Lockheed Martin, since they make the C-130 Hercules, which is the aircraft I worked on in the Air Force, and they are also the only ones showing what they are working on. This URL http://www.lockheedmartin.com/wms/findPage.do?dsp=fec&ci=16745&rsbci=0&fti=0&ti=0&sc=400 is to their website detailing the CEV(Crew Exploration Vehicle) system. It seems to be a hybrid of shuttle technology, and more traditional multi-stage rocketry. The CEV is launched atop a booster like an Apollo capsule, so all of the propulsion and fuel components are below the spacecraft. Crap can fall off forever and never endanger the crew. Once in LEO the boosters fall away and the CEV links up with whatever mission specific modules have been lifted previously into orbit by cheaper boosters. These can range from simple scientific and repair missions, to boosters and habitation modules designed for lunar or martian sojourns. While the CEV looks like a glider, it returns to Earth using parachutes, and most likely lands in the ocean. I like this system a lot. It maintains a level of reuse, without making the system so complex that it is as unwieldy as the shuttle. Boeing is playing their cards close to the vest, saying only that their system is also more akin to Apollo. We'll see what happens, since the shuttle fleet is scheduled to be decomissioned in 2010.
I have always loved the shuttle program, and watching a launch in person is one of the greatest thrills I have ever experienced, but as with many relationships the time has come to say goodbye. Atlantis, Challenger, Columbia, Discovery, Endeavour, and of course Enterprise have served their country, and planet well and safely (2 losses out of 114 launches is pretty damn good). They have carved their names indellibly on the atmosphere of this globe, but it's time to let them go, and move ahead.