An Irishman's Diary

THE APOLLO 11mission, which landed a man on the moon 40 years ago this week, is rightly hailed as one of the great triumphs of human endeavour. Few, though, appreciate how perilously close the whole enterprise came to disaster.

The Apolloastronauts accepted risk in a manner in which our modern health and safety obsessed society would never countenance. Many put their chances of landing on the moon at 50:50 with a one-in-10 chance of being killed in the process.

These were odds which the Apolloastronauts, former fighter pilots or test pilots for the most part, were prepared to accept.

Anything could have gone wrong. The launch on board a giant firecracker, otherwise known as a Saturn V rocket, could have resulted in instant death. The orbital manoeuvres and re-entry procedures needed to be absolutely precise or the astronauts would have found themselves flying into infinity and certain oblivion.

Given all that could have gone wrong, Apollo 11went very right – except in one critical respect.

As Neil Armstrong and Buzz Aldrin descended to the moon, Aldrin, who was the lunar module pilot, noticed they were off course.

Instead of encountering a smooth surface in the evocatively named Sea of Tranquillity, the two were confronted with a sea of boulders which would have snapped the flimsy lunar module Eagle’s legs off. The Eagle was known with black humour by the astronauts as the “flying bedstead” because of its lightweight construction.

With time running out, Armstrong took manual control of the Eagle.

Amid all the chatter from Houston, came the ominous warning “60 second”. They had 60 seconds of fuel left, then the 30 second call came, then they descended into the “deadman zone” where they could not abort and had to land.

By this time, millions of US television viewers were watching a simulated version of the lander on CBS. The simulated model, which had been programmed to match the precise movements of the Eagle, was sitting pretty on the surface as the frantic chatter continued between the lunar module and Houston.

The Eagle did make it on to the surface just in time. Back in Houston, came the memorable response. “There’s a bunch of guys about to turn blue. We’re breathing again”.

Watching too in Houston was a 24-year-old Irishman Paddy Norris. A native of Dublin and a mathematical graduate from UCD, Paddy had emigrated to the UK like so many of his generation.

Paddy joined the Apollospace programme through a Houston-based company TRW which developed the software to guide the critical navigation systems for the Apollo landers.

Apollotook a famously exacting toll on all its employees. In the year prior to the moon landings, Norris took only two days off. The problems Norris and his team had to deal with taxed their ingenuity to the last. Four years before the lunar landing, the Apolloteam first noticed that gravity on

the moon was not smooth, but lumpy. Irregularities were alternatively speeding up and slowing down craft. It made it not only difficult to calculate trajectories for landing, but also to determine the position of the craft.

The discrepancy was only 10 to 20mm per second, but that distance became a metre a minute, 60 metres an hour and by the time, the Apollo 11 command module had circled the moon dozens of time, the discrepancy could be measured in kilometres.

It become known as the “perilune wiggle” and defeated the best brains of Nasa.

The Eagle ended up being way off its intended target – six kilometres in total.

Nasa could not afford another near miss.

Paddy was part of the team which worked on the problem in the hiatus between Apollo 11and Apollo 12in November that year.

The solution became a matter of mathematics and was relatively simple to understand. They measured the actual position of the spacecraft as it emerged from the far side of the moon, out of contact with the Earth.

By calculating where the spacecraft actually was and where it should have been according to conventional physics, they could do some old-fashioned pen and paper calculations and then feed the data into the guidance computer.

“Crude and inelegant as this approach was, it proved successful,” Paddy recalls.

The measure was used to spectacular effect on Apollo 12.It was charged with setting down near the Surveyor IIIspacecraft which had been sent to the moon two and a half years previously.

Surveyor IIIwas conducting some valuable experiments which the crew of Apollo 12had to recover, though the most famous result was unplanned. Scientists would later find that bacteria trapped in the lens of Surveyor's camera survived for two and a half years in the vacuum of space on the Moon.

Apollo 12commander Pete Conrad could hardly contain his excitement as he came into land and he spotted Surveyor IIIat the top of a crater as planned.

Conrad exclaimed: "Hey, there it is! There it is! Son of a gun! Right down the middle of the road!" The sight of Surveyor IIIjust 300 metres from the lunar module Intrepid remains the enduring image of Apollo 12, a testament to man's ingenuity and the dedication of men like Paddy Norris who were willing to work night and day to achieve the improbable.