Can I ask if anyone knows why that it is the last one?
Because multiple generations of American politicians don't have any vision or foresight.
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The Shuttle is a brilliant piece of equipment, but brilliantly flawed. Saturn V (the rocket which took men to the Moon) could loft 140tonnes into Low Earth Orbit, and 40-odd tonnes into Trans Lunar Injection (on the way to the Moon). TLI is important, because really, if you have the capability to achieve TLI, you can achieve trans-anywhere-injection (for instance, to Mars - TMI).
Saturn was hugely expensive to launch, and the Shuttle was proposed as an alternative that would significantly reduce the cost of getting into space. Unfortunately, the Shuttle programme has ended up costing about as much per launch as a Saturn V launch, and, because of the "reusable" factor, take a significant amount of effort to renew for each launch. But compared to the Saturn V's 140 tonnes into LEO, the Shuttle can only aloft 30 tonnes (still more than anything else available, mind you). Furthermore, the Shuttle cannot leave LEO, so as an exploration device doesn't take us anywhere too far (the Shuttle only operated at max 600km altitude; for reference, the Moon is 300,000km away.).
If the Shuttle programme had not commenced, and Saturn continued to be used, at the same funding that the Shuttle enjoyed there could have been 6x Saturn flights a year, at least two of them being manned trips to the Moon.
There's a whole host of other reasons why the Shuttle needs to be replaced. Unlike Saturn/Apollo, there are practically no survivable failure modes during ascent and re-entry. It's a tremendously complicated machine, requiring major refurbishment after each launch. The Solid Rocket Boosters cannot be controlled once they are ignited, which is inherently unsafe. The Thermal Protection System is notoriously fragile. I could go on.
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What is absolutely crazy, though, is cancelling the Shuttle programme
where there is no replacement in place. This goes back to my first comment. US presidents and administrations from George H. W. Bush down to Obama have been hacking away at NASA's budget. Constellation - George W. Bush's initiative - was a badly thought out programme, but at least it was a programme. Now there is a vague desire to develop some sort of new heavy lift capability that will, at least, rival the Shuttle if not Saturn, and an equally vague desire to have commercial manned spaceflight to LEO. All the while NASA's budget is still being reduced - from US$19bn to US$17bn next year.
US$17bn is a lot of money, I hear you say? Well, for context, the US Army
alone spends around US$21bn on airconditioning. Yes. If you look at the Department of Defense budget (with ancillaries) you're looking at between US$800bn and US$1tn. With a ROI of somewhere around 8:1, investing in spaceflight is both cheap and profitable - but I guess invasions are better. Never mind all the things the US space programme has given us - anyone using this forum, it has literally changed our life in every way (from integrated circuits to GPS and communications satellites to modern ceramic materials to more fuzzy subjects like risk and capability management...)
Sorry for the rant, but this is a subject I'm very passionate about. While I watched
Atlantis lift today I found it incredibly hard to accept that this was the last time anyone on Earth would see this awesome sight.