Damaged tile on the underside of the space shuttle Endeavour/Nasa
Once again Nasa has got itself into a tizzy about damage to a space shuttle. At the weekend, astronauts examined the underside of Endeavour to work out how serious a gash in the craft's heat shield is.
After the Columbia tragedy in 2003, when seven astronauts died as the shuttle disintegrated on re-entry to the atmosphere, Nasa has been rightly cautious of damage to the heat shield that lines the underside of the shuttle. In that instance, a briefcase-sized chunk of insulating foam fell from the main fuel tank and gouged a hole in the heat tiles of the orbiter's wing. Superheated air rushed into the wing as the shuttle came back to Earth and melted the spacecraft from the inside.
Nasa subsequently grounded the shuttle programme and spent several years devising methods to look for and fix damage to the heat shield when the shuttle is in space. It's a critical issue because the foam that ended up causing Columbia's demise regularly falls off the fuel tank during launch. Last week, engineers estimated that nine pieces fell off the tank, one of them causing the damage to Endeavour.
So the underside of the orbiter is now photographed from the International Space Station on every mission and the images are analysed back in Houston. The craft's robotic arm has a laser and a camera attached to look at the heat shield in extreme detail. If damage is discovered, it can be fixed (theoretically) using a range of ideas developed and tested on Earth. These include painting over the crack, plugging the hole with a filler material, or attaching a new shielding panel.
A decision on whether Endeavour needs any fixing is expected on Wednesday but the problem highlights an issue that many critics of human spaceflight continually point to: much of the effort in sending people space seems to focus on keeping them safe rather than useful science.
There's little doubt that there is a case for sending people into space (if properly resourced, a human can do far more useful science than a robot according to a report by the Royal Astronomical Society in 2005) but what's the point in sending people up into space on a rickety old space shuttle? Should space agencies save their cash and self-impose a moratorium on human spaceflight until we build better and more reliable spacecraft?
