|InfoVis.net>Magazine>message nș 114||Published 2003-02-12|
|También disponible en Espańol|
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Last February 1st, we contemplated, astonished, the images on CNN of the trace of disintegration that the Columbia space shuttle was leaving in Texasâ skies.
The tragic accident that took the lives of 7 people could have its origin in the loosening of a piece of the main propellant tank that collided with the left wing of the shuttle during take off.
Since then much speculation has taken place about the actual causes and it has been said that the diminution of the NASA budget for the shuttle program had reached worrying limits.
On its own side, NASA offers a Flash movie where it explains the advances achieved in the shuttle program. Namely, they offer different types of charts showing, for example, that in the last years:
The unfortunate re-entry has been covered graphically, with examples like the newspaper âEl Mundoâ in Spanish or those of Time Magazine. Some websites like the one of NASA or the CNN offer a wide graphical coverage of the catastrophe.
NASA offers a series of charts where the state of all the relevant sensors of the left wing is indicated, in the different phases of re-entry.
The investigation begins now. In a few months weâll know what happened and if, as occurred with the Challenger in 1986, the erroneous interpretation of the data represented in an inefficient way has something to do with the disaster this time or not.
On that occasion the cause of the accident was a rubber ring (O-ring) that sealed the joint between two sections of one of the Challengerâs ancillary rockets (boosters).
The afternoon before the launch, with a temperature forecast between 26 and 29 degrees Fahrenheit, the technicians of Morton Thiokol, manufacturer of the âboostersâ, concerned about the behaviour of the joints at low temperatures, advised against the launching. None of the previous launches had occurred at such low temperatures and some flights had problems related with the joints.
The technicians sent a fax of 13 pages to the NASA officers who found the data and tables insufficient to conclude a relation between low temperatures and the O-ring joint . After an intense debate it was decided to go on with the launch, despite the fact that it was the first time that Morton Thiokol advised a no-launch in 12 years.
The posterior investigation showed that the available data about the launch history would have been enough to relate the temperature with risk of failure of the O-rings properly. (See the accompanying charts or those available at the gallerĂy del of the SCS and the University of Colorado).
Edward Tufte has a complete discussion of this issue in his book âVisual Explanationsâ. He concludes that the technicians needed a quick and clever analysis of the data on one hand and an efficient way to present it to convince the NASA officers to avoid the launch, on the other. An appropriate representation of the data instead of the study of the individual cases would have been definitive in order to avoid the catastrophe.
The correct visualisation of information usually makes a difference. Sometimes in a tragic way.
In memoriam of the Columbia and Challenger crew.
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