I have seen only one shuttle space launch from Cape Canaveral - and yes, it was breathtaking. I saw it from many miles south and what was most striking was that it did not go straight up, but at a steep angle out over the sea. The sheer, inexorable power of the craft and its thrust was what took the breath away; thinking there were seven fallible human beings inside at the mercy of such power was peculiarly moving.
For those of us who can remember early space adventures, it is all still quite wondrous. But after the Columbia shuttle exploded on 1 February as it headed back to earth, I heard a teenager say: "What's the big deal? I mean, there were only seven people killed." For those under 30, space travel is now something taken completely for granted, the Challenger shuttle disaster of 1986 a dim aberration of long ago, the moonwalks something that happened in olden days. But when Columbia - after 15 days in space - started to break up somewhere over California at around 203,000ft and still travelling at 12,500 miles per hour, the wonder and horror returned to older people in equal measures.
Columbia was the oldest of Nasa's five shuttles, and the heaviest. It had two million separate parts (11 per cent of which have now been recovered) and 200 miles of wiring; it was first launched on 12 April 1981 to the good wishes of President Reagan. It underwent a $160m upgrade in 2001 - that alone lasted 18 months - and was designed to last 100 missions. But Flight STS-107, its last, was only its 28th. Most of its technology dated back to the 1970s: the five computers controlling each shuttle mission have one megabyte of memory, when even a basic home computer now has more than 100 megabytes. The astronauts overcame this by bringing their own laptops, which they plugged in and used for e-mail.
The inquests into what went wrong are revealing once again the secretive, macho culture of Nasa, which is rather like that of the CIA or FBI. Everyone agrees that as Columbia was re-entering the atmosphere, heat pierced its left wing and led to the break-up. But why? Nasa now admits that three particles of the foam used to insulate the fuel tank on the way up broke off and (possibly) hit the underside of the left wing (the foam, by that stage, having become hard, so that a hit would be at the equivalent of 400mph). The other, less likely possibility is that the craft was hit by a piece of space debris: a small, unidentified object was monitored by mission control on the day after launch. Unbelievably, there are now 9,000 pieces of such man-made junk orbiting the earth.
But questions are also being asked of Nasa itself. In its 28 flights, Columbia had serious problems on 20 of them; it nearly had a disaster because of its wiring in 1999, but that was largely hushed up. From 1995-99, shuttles took 1,239 hits while in flight. Each shuttle is covered with 34,000, two-inch silica tiles that are supposed to absorb the heat of re-entry. Very likely, a significant number of these tiles were lost or damaged in the recent disaster; on its maiden flight in 1981, Columbia lost 16 tiles and 148 were damaged, a clear indication of a basic design flaw.
Just as with the FBI after 9/11, it now emerges that mid-level Nasa employees saw it all coming. Robert Daugherty, an engineer, wrote in an e-mail shortly before the disaster that a problem caused by falling chunks of foam on the ascent was "survivable but marginal" and that "I am advised that the fact that this incident occurred is not being widely discussed". A colleague e-mailed three days before the tragedy: "We can't imagine why getting information is being treated like the plague." Supposedly no Nasa high-up saw these e-mails; but the crucial question is whether they knew of the problem and were simply keeping their fingers crossed that the shuttle would return safely. Columbia did not carry repair materials or an airlock that would have allowed it to dock with the International Space Station, which might have provided the seven astronauts with refuge.
Each shuttle flight costs between $400m and $500m; the International Space Station is costing $100bn, a third of which is being paid by the US. Columbia was carrying around 80 experiments in everything from heart disease to perfume, but most of them could have been performed just as easily by robots. Flight STS-107 was certainly part of the great romance of space travel, but was it strictly necessary? More voices are now being raised, suggesting the future lies only in unmanned space travel.
The real problem is that since the trips to the moon, everything Nasa has done is an anticlimax; its chief project is now the space station, but that does not grab attention. Budgets are at best static - and political infighting proliferates. Few dream of going to the moon again, let alone Mars. No wonder the enormous achievement of space travel no longer grabs the imagination of the young.