Fire on the Mountain
remembering 1986-11-22
Michael Olberg
Song by Grateful Dead (lyrics)
Fire on the mountain
The year 1986
January 1
Spain and Portugal enter the European Community
January 28
Space Shuttle Challenger disaster; disintegrates 73 seconds after launch from the United States, killing the crew of 7 astronauts, including schoolteacher Christa McAuliffe.
February 9
Halley's Comet reaches its perihelion, the closest point to the Sun, during its second visit to the solar system in the 20th century (the first was in 1910).
February 28
Swedish Prime Minister Olof Palme is shot to death on his way home from the cinema in Stockholm.
April 26
Chernobyl disaster
June 22
In one of the most famous FIFA World Cup matches, Argentinian football player Diego Maradona scores one handball goal, nicknamed the "Hand of God".
September 7
Chilean dictator Augusto Pinochet survives an assassination attempt by the FPMR; 5 of his bodyguards are killed.
October 10
The 5.7 Mw San Salvador earthquake shook San Salvador, El Salvador with a maximum Mercalli intensity of IX (Violent). Up to 1,500 people were killed.
November 25
Iran-Contra affair: U.S. Attorney General Edwin Meese announces that profits from covert weapons sales to Iran were illegally diverted to the anti-communist Contra rebels in Nicaragua.
The people
ESO director general, Lodewijk Woltjer, and acting director of La Silla, Hans Emil Schuster.
ESO representative in Chile, Daniel Hofstadt.
ESO chief administrator, Gerhard Bachman, and SEST support astronomer, Peter Shaver.
IRAM engineer, Dietmar Plathner, with further IRAM and Chilean staff.
Director of Onsala Space Observatory, Roy Booth, and microwave engineer, Magne Hagström, with visitors.
Microwave engineer, Nick Whyborn, watching the installation of the SEST subreflector.
Magne Hagström and Guillermo Delgado studying wild life near SEST.
Albert Greve, IRAM, Lars E.B. Johansson and Lars Göran Gunnarson, Onsala Space Observatory.
The telescope
The announcement
The Plateau de Bure radio interferometer in the French Alps.
Construction
The incidence
- Author: P. Shaver
- Date: Nov 22, 1986
- Present on site: D. Plathner, IRAM + 2 Chilean fitters
Report on SEST assembly incident
Status of the assembly at time of incident
Late on Nov 21 the quadrupod with subreflector was placed on the main reflector structure because the wind has calmed down and there were excellent weather conditions.
However, the legs of the quadrupod could only be fixed provisionally.
Final installation with all bars and application of Loctite and nominal torque to the screws continued on Nov 22.
As the quadrupod legs are not covered with a coherent and reflecting alu-layer, some problems were expected in the upper part of the legs due to reflected Sun radiation. The legs were therefore protected by stone wool with a reflective alu foil on top.
Report on incident
Shortly before noon one of the switches on the handset broke with which the reflector can be rotated from the top of the scaffold.
To avoid any risks with the newly installed quadrupod it was decided that D. Plathner would stay with one of the fitters on the site while the other was taking his meal.
Bringing the first fitter to the canteen, D. Plathner looked for the electrician on turno. He decided to come to the site before lunch and repair the handset.
At 1.00 pm the fitters were exchanged before or after their respective lunch time. Work continued on the quadrupod legs.
At about 1.30 pm smoke was stated at the edge of the subreflector. It was decided to rotate the reflector, but it did not help.
D. Plathner went down from the scaffold into the barrack to call the firebrigade, asking the electrician to continue rotating the reflector in the still possible direction to limit the fire.
The firebrigade came and the way how to act was discussed and defined. The only possibility was to project light water. However, the wind was that strong that only occasionally the water would reach the fire.
It was furthermore decided to tilt the reflector which was difficult in several respects:
- the quadrupod legs were not yet fully fixed (only two of the four)
- in the region where the reflector should have been tilted (out of the Sun) was the assembly scaffold.
- the tilting operation is only possible from inside the telescope base so that a visual check is not possible.
The reflector was finally tilted but although it was carefully done it hit the scaffold with two bars of the support structure.
Obviously the obtained tilt angle or the Sun rotation changed the situation. In any case the fire was slowing down although the wind had still increased.
At 3.00 pm all was absolutely calm and at 5.00 pm the firemen left the site.
Damages stated
- two quadrupod legs
- the secondary mirror plus its support structure
- a number of main reflector panels
- two bars of the reflector structure
Reason for incident
For this assembly step (installation of quadrupod on main reflector) the influence of the Sun and in particular the reflective quality of the polished looking aluminium surface of the secondary mirror were underestimated. This lead to an excessive heat concentration and as a consequence to ignition in the secondary mirror structure.
La Silla, Nov 25, 1986
signed D. Plathner
The damage
