Friday, September 08, 2006

Latest Lab Report

Here is my Lab Report column for the October issue of Prospect. And while I’m about it, I’d like to mention the excellent comment on Prospect’s web site about the shameful issue of Britain’s stance on the Trident nuclear submarines. Sadly, this kind of clear-headedness doesn’t find a voice in Westminster.


In-flight chemistry

It is not easy to make TNT, as I discovered by boiling toluene and nitric acid to no great effect during a school lunchtime. Admittedly it is not terribly hard either, if you have the right recipe, equipment and ingredients – the details can be found on the web, and the raw materials at DIY stores – but a little practical experience with chemistry provides some perspective on the notion of concocting an aircraft-busting explosive in the cabin toilet.

So it’s not surprising that some chemists have expressed doubts about the alleged terrorist plot to blow up transatlantic flights. Could two liquids really be combined to make an instant, deadly explosive?

Speculation has it that the plotters were going to mix up triacetone triperoxide (TATP), an explosive allegedly used in the London tube bombings last year. In principle this can be made from hydrogen peroxide (bleach), acetone (paint thinner) and sulphuric acid (drain cleaner). But like so much of chemistry, it’s not that straightforward. The ingredients have to be highly concentrated, so can’t easily be passed off as mineral water or shampoo. The reaction needs to be carried out at low temperature. And even if you succeed in making TATP, it isn’t dangerous until purified and crystallized. In other words, you’d be smuggling into the loo not just highly potent liquids but also a refrigerant and distilling apparatus – and the job might take several hours. Gerry Murray of the Forensic Science Agency of Northern Ireland told Chemistry World magazine that making TATP in-flight would be “extremely difficult.”

Why not just smuggle a ready-made liquid explosive on board? Some media reports suggested that the plotters intended instead to use bottled nitroglycerine. But you’d need a lot of it to do serious damage, and it is so delicate that it could well go off during check-in. The same is true for pure TATP itself (a solid resembling sugar), which is why the unconfirmed suggestion that it was used for the tube bombings has met with some scepticism.

What does this mean for the security measures currently in place? It is hard to understand the obsession with liquids and gels. It’s not clear, for example, that there is any vital component of any ‘mixable’ explosive that would be odourless and pass a ‘swig test’, let alone be feasibly used in flight to brew up a lethal charge. Why are solids not subject to the same scrutiny? Most explosives (including TATP) in any case emit volatile fumes that can be detected at very low concentrations.

When airports instigated the ‘no liquids’ policy in August, they were making an understandable quick response to a poorly known threat. But they now seem to be at risk of perpetuating a myth about how easy it is to do complex chemistry.

Moon crash

Smashing spacecraft into celestial bodies has become something of a craze among space scientists. In 1999 they disposed of the Lunar Prospector craft, at the end of its mission to survey the moon for water ice and magnetic fields, by crashing it into a lunar crater in the hope that the impact would throw up evidence of water visible from telescopes. (It didn’t.) The Deep Impact mission ploughed into the comet Tempel 1 last February, revealing a puff of ice hidden below the surface. A rocket stage used to send a new satellite to the moon in 2008 has been proposed for a more massive re-run of the Prospector experiment. And the THOR mission pencilled in for 2011 would send a 100-kg copper projectile crashing into Mars, creating a 50-m wide crater and possibly ejecting ice, organic compounds and other materials.

The most recent of these kamikaze missions is SMART-1, the European Space Agency’s moon-observing satellite, which ended its career on 3 September by smashing into the lunar Lake of Excellence. Again, the aim was to analyse images of the impact to identify the chemical composition of the debris, using the technique of spectroscopy. SMART-1 had already stayed active for longer than originally expected, and its experimental ion-thrust propulsion system was exhausted, making a lunar crash landing inevitable anyway. This was another case of wringing a last bit of value from a moribund mission. The disposal of a washing-machine-sized probe on the moon is hardly the most heinous act of fly-tipping – but it can’t be long before this trend starts to raise mutters of environmental disapproval.

Perhaps we can clear up the mess when we return to the moon. Lockheed Martin has recently been awarded the NASA contract to build the Orion Crew Exploration Vehicle, the replacement for the beleaguered space shuttle and the basis of a new manned moon shot. Scheduled for 2014 at the latest, Orion will ditch the airplane chic of the shuttle, comprising a single-use tubular rocket with a lunar lander and re-entry capsule in its tip, the latter provided with heat shield and parachutes. Lockheed Martin has presumably been working hard on this design, but cynics might suspect they just stole the idea from that film with Tom Hanks in it.

The Macbeth effect

Shakespeare’s insight into the human psyche is vindicated once again. The impulse to wash after committing an unethical act, immortalized in Lady Macbeth’s “Out, damned spot!”, has been confirmed as a genuine psychological phenomenon. Two social scientists say that ‘cleansing-related words’ were more readily produced in exercises by subjects who had first been asked to recall an unethical deed. These subjects were also more likely to take a proffered antiseptic wipe – and, rather alarmingly, such physical cleansing seemed to expunge their guilt and make them less likely to show philanthropic behaviour afterwards. There is nothing particularly godly about cleanliness, then, which is a sign of a guilty conscience cheaply assuaged.


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