The ArcelorMittal Orbit has divided opinion and to some eyes cuts a rather ungainly figure on the Olympic Park skyline.But at night it is transformed by a dynamic lighting display that renders its bizarre geometry intelligible and breathes life into its carcass.Jill Entwistle spoke to its design team leader,Arup Lighting's Florence Lam
The ArcelorMittal Orbit is a Marmite proposition.Even devotees of sculptor Anish Kapoor,accustomed to his ethereal sky mirrors and perceptual sleight of hand,have blinked at what appears to be a roller-coaster after a bit of a mishap.But Florence Lam,who led the Arup team in lighting it,has rather come round to it.
"While somewhat controversial,the Orbit is set to be a focal point of the Games and far beyond,"she says."But so far everything has been presented during the day,and I've been telling people to go and see it at night.The night-time experience is very different and I'm quite sure it will change people's view."
Until autumn last year there wasn't much danger of making any kind of impact in lighting terms,as the budget was minimal,Lam reveals."Our original low-budget scheme,submitted for the first stage of planning back in 2010,was based on the metaphor of an orbit.We planned to have static red LEDs with a few powerful projectors accentuating the four looping'turns',symbolising the accelerated speed of an electron cloud."
With the building of the main structure underway,London mayor Boris Johnson suddenly twigged that no one was going to notice the Olympic landmark after dark and rustled up additional funds."He realised that it had to be a little more exciting,"says Lam.
The new budget may have been more generous"more than 10 times the original"but the timing stayed tight.Arup Lighting was only signed up for the bigger-budget feature lighting in September 2011 for a May 2012 handover.With Philips as a potential sponsor,the London Legacy Development Corporation asked Arup if that would be difficult in terms of making the scheme work and whether it would be a problem relying solely on its product range.The sponsorship deal was eventually signed in January after the scheme had got full approval."It actually saved time not going through a tender process and we were also familiar with the luminaires,"says Lam.
Articulating the sculpture without imposing on it either literally or conceptually was central to the lighting.As was not treating it like a roller coaster.The scheme had to make a dramatic after-dark impact without cheap effects.It was also important that the luminaires didna??t compromise the appearance of the structure and were carefully positioned and concealed."The light is not the sculpture,"says Lam.'Everything has to be around it but not overpowering it."
Compliance with park strategy
The feature lighting is entirely LED and designed to give a uniform,low level of luminance(average<20cd/sq m)to various parts of the structure's surface
Light spill to adjacent waterways does not exceed 0.45 lux
Average light intensity around the sculpture is 15 lux
Both the feature and functional lighting are switched off at midnight unless there is a special event,in which case it will be switched off up to an hour after the event has finished
Environmental requirements
On top of the artistic and logistical issues,the lighting had to meet the strenuous requirements for Olympic site structures laid down by the Olympic Delivery Authority.
Across the whole site light levels had to be a minimum of 15 lux on the ground and 30 lux average.Biodiversity requirements also meant that light spillage was a consideration,especially as the Orbit is close to a waterway,home to wildlife.No more than a half lux was allowed on water,and a spillage diagram was created to demonstrate the impact of light on the surroundings.Bats in the area were another consideration,imposing a limit on UV light content.Here aesthetic and environmental criteria coincided.Saturated red light was chosen to accentuate and dramatise the bespoke red of the sculpture"RAL 3003 Carmine Red"which consumed less energy than white light.Red light,of course,has hardly any UV content.
The idea of relying on projected light from luminaires positioned outside the structure was dismissed early on-it would have flattened out the intricate looping lattice,caused light spill onto the non-sculptural elements such as the spiral staircase and additional mounting poles would have created clutter in the surrounding landscape.While some luminaires,the smaller version of Philips'ColorBurst,are mounted on the roofs of the adjacent pavilion and plant building to punch light on to the lower parts of the lattice,most of the luminaires are mounted on the structure's central core,primarily on the expanded stainless steel mesh enclosure on top of the spiral staircase.Here,access hatches to the fittings can easily be reached from the flat landings.Using ColorBlast fixtures,each hatch allows four lighting positions.
To ensure the Orbit stays visible at a distance of more than 30km across London,the top loop is lit by a combination of the more powerful ColorReach fittings projecting from the observation roof,and clusters of ColorBlast located above the tuned mass damper,grazing from within the lattice.
The observation deck is a hollow circle,like a doughnut,with vertical glazing that allows visitors to look down through the hole.ColorGraze fixtures are positioned around the edge of the hole on the underside of the deck,turning it into a large red reflector that illuminates the sculpture below.This allows visitors to see down into the structure without glare to the eyes of people on the ground looking up.
Smaller ColorBurst fittings with amber/warm white LEDs are used on the lowest lattice ring around the 2.5m-high canopy.The amber versions graze up the outer skin of the canopy at the base of the structure to bring out its rusty colour,while the warm white fittings are aimed downwards,slightly angled,to graze light across the plaza,graduating into darkness.
Two concrete plinths at the base also house many ColorBurst fixtures,fitted between the steel members.These light the lower part of the lattice's"intestines",creating a soft,pulsating,flickering effect as part of the dynamic display."The more sensitive treatment is important because this is the part people can get close to,"says Lam.
The original spec of fluorescent luminaires to provide functional lighting on the staircase was changed to the Pacific LED range.This meant the luminaires could be programmed and become part of the dynamic feature lighting during the light show.'Or,potentially,you can switch off the white lighting on non-event days so it transforms back to the pure sculpture idea,"says Lam.
The scheme was about very precise aiming and very tight beams,with a mix of lenses from medium to narrow.
"We carried out detailed computer modelling to show environmental compliance for the planning consent on the lighting,"says Lam."The photometrically correct'skin of lighta'was then unwrapped from the computer study and passed to our guy who looked after the visualisation for the entire site to dress on to the actual Orbit 3D model.That way we could go back to the mayor to show him exactly what it would look like."
There are 276 Philips luminaires installed for the feature lighting(bottom)
Added dynamism
As well as meeting the extra cost of details such as customising everything from the bracketry to the housings(painted to the bespoke red colour of the sculpture where necessary),the additional budget gave the lighting project a crucial fillip by allowing the lighting to be made more dynamic.
"Even from day one,when we hardly had any budget,the lighting concept was about movement,"says Lam."We only highlight the points where you have the swing.In an elliptical movement such as that described by the Orbit's steel members,it's at the vertex points where it's turning that you get the highest kinetic energy,so those are the points that are lit,with the rest of the sculpture graduating into darkness."
The light show begins with the scene in total darkness,and then the staircase starts to glow from the ground up"like life starting to grow,"says Lam.When it reaches the top,the observation platform is lit up like a sun.The pulsating light then moves back down again,followed by the canopy lighting up"like the heart of a living organism,which starts pumping".The orbit of light starts slowly with one band of light swooping round.That speeds up and grows,with a chasing effect mimicking the orbital behaviour of an electron cloud.
"At night-time the lighting helps to unravel the sculpture's form and make its complex geometry a lot more understandable,peeling it from the functional bit,"says Lam."The lighting really added a new dimension.It really comes alive."
Orbit facts
Standing 114.5m tall,the ArcelorMittal orbit is the UK's tallest sculpture
Two observation decks,at 75.75m and 80.50m,provide views of up to 32km distances
There are 276 luminaires installed for the feature lighting,totalling a maximum of 15kW installed load.The original 106 fluorescent luminaires were replaced with LED luminaires to allow the"functional"staircase lighting to be programmed and form part of the dynamic light show sequence
This is the first Anish Kapoor sculpture to be lit
TECHNICAL SPECIFICATION
COLORREACH POWERCORE OBSERVATION DECK ROOFTOP
COLORBLAST OBSERVATION DECK ROOFTOP(TUNED MASS DAMPER,FENCE),TOP OF STAIRCASE
COLORGRAZE OBSERVATION DECK(UNDERSIDE)
COLORBURST PLANT/PAVILION ROOFS,LOWER LATTICE RING,PLINTHS
PACIFIC LED INTERNAL STAIRCASE
ALL FIXTURES SPONSOR PHILIPS LIGHTING
