Bolt From The Blue

Biplab Das catches up with a city astrophysicist who says radio 
waves emanating from two stations in San Diego and San Francisco 
gave him the clue that a thunderbolt was the cause of Columbia's gory end 

A research team in Kolkata, led by Professor Sandip Kumar Chakrabarti, an astrophysicist with the S. N. Bose National Centre for Basic Sciences and the Centre for Space Physics claims to have determined what brought the Columbia space shuttle to a gory end. He says a cloud-to-cloud thunderbolt could have struck the left side of the shuttle, triggering a chain of events that ultimately led to its destruction over Texas. 

How he came to this conclusion makes for interesting reading. "At the CSP on the evening of 1 February, we tuned an antenna which listens to long radio waves having Very Low Frequency," says Chakrabarti. "It was precisely 7:26 pm in Kolkata when the antenna began recording radio signals." The antenna was listening to radio waves with a frequency of 18.2 KHz that were emanating from two VLF generating stations in San Diego and San Francisco. Any disturbance in the atmosphere affects radio waves and is measured by the CSP antenna. 

Back home late that night, Chakrabarti witnessed the tragic end of the space shuttle on television. "It was 9 am at the Kennedy Space Centre, Florida, when the space shuttle disintegrated over Texas," he says. "The freely falling debris of the shuttle reminded me of a meteor shower which also emits very low frequency radio waves while burning and darting through the earth's atmosphere." What is more, VLF radio waves travel at the speed of light and for a long distance - as much as 20,000 km on earth - almost without losing their intensity. 

The next day, driven by this insight, Chakrabarti alerted his team and went to the CSP. They checked the signals recorded by the antenna. "We got more than we anticipated," he says. "Actually, the antenna recorded intriguing signals immediately after it was switched on at 7:26 pm." The antenna also recorded signals at 7:30 pm, which coincided with the time the shuttle disintegrated. 

But Chakrabarti and his team were more interested in the signals recorded at 7:26 pm. These showed a noticeable disturbance in the atmosphere when Columbia was making its descent. The signals generated at the time the shuttle's debris was falling freely and emitting VLF radio waves did not count. 

As it was morning in the USA, the sun's ultraviolet rays had formed the lowest layer of the ionosphere. It is well known that the lowest layer of the ionosphere absorbs radio waves, halting their propagation for a long distance. "Despite this fact, the radio signals reached the antenna at the CSP," says Chakrabarti. "So we were curious to know how the signals travelled here all the way from the USA." Only some abnormality in the atmosphere could have strengthened and ferried the signals to the CSP's antenna, he says. "So, we looked for any abnormality in the atmosphere when the space plane was on its way to land at the Kennedy Space Centre, Florida." 

The team's search was rewarded as Nasa released a few photographs taken by an amateur astronomer. With this came the clue to the disaster. Those photographs clearly showed a thunderbolt had struck the craft as it was flying over California. "In California, it was 5:53 am when the bolt struck," says Chakrabarti. "At the same time, sensors of the doomed craft first indicated that something went wrong." 

The cloud-to-cloud thunderbolt formed a lightning channel between the two clouds. "With enormous energy and temperature, the channel might have touched the left side of the craft causing irreversible damage." The energy in that channel was enough to keep an ordinary room air conditioner running for nearly two weeks and the temperature rose to 25,000 degrees Celsius, which could easily vapourise any earthly metal. "Immediately after the bolt struck, sensors on the left side of the craft started to detect an abnormal rise in temperature."

According to a timeline released by Nasa, when Columbia was over Arizona and New Mexico, two sensors on the left wing's upper and lower skin fell off. Two minutes before the disaster, on-board computers detected that the shuttle began to fly off course because of the increased drag on the left wing. "To overcome the drag, the craft desperately turned on its recovery system." 

Columbia automatically fired two of its nose steering jets for 1.5 seconds to counteract this drag. "In the meantime, superhot plasma (a combination of ions and electrons formed due to the craft's friction with the atmosphere) seeped into the crew area," says Chakrabarti. "At 9 am, the Kennedy Space Centre completely lost communication with Columbia, which was then seen breaking into pieces over Texas." 

Nasa experts had ruled out any possibility of an accident caused by the shorn off tiles that protected the craft against the heat produced due to friction between the shuttle and the earth's atmosphere, he says. "What is more, Nasa has ruled out the possibility that landing gear was lowered a few seconds before scheduled time. It enhances the chances of a thunderbolt being the culprit that caused Columbia's demise."