Stealth is about staying undetected until your mission is accomplished. Many animals, for example, are stealth hunters. The polar bear, for example, walks to within 90 m of a seal and then crouches. If the seal doesn’t notice, it then creeps to within 9 to 12m of the seal and then uses a short burst of speed to attack.

Stealth adaptions and tactics mean an animal uses less energy on energy-intensive activities such as speed and endurance. Nature is energy efficient and clever like that. This tradeoff between stealth and speed isn’t unusual in the animal world. Even a speedy-looking animal like the cheetah can only chase its prey at 100kmph/(60mph) for about 650m/700 yards.

The pronghorn antelope has a top speed of 55 mph and can run 30 mph for over 20 miles! Its top speed is not much but if a pronghorn antelope has only a second’s notice to get that 700 yards’ distance, it can probably outrun a cheetah. This is why a cheetah has to use stealth to hunt them. In our minds, the pronghorn antelope doesn’t represent speediness in the same way the cheetah does might but it has better – and “life-enhancing” – muscle performance as their muscles don’t produce lactic acid at as fast a rate as a cheetah’s.  

This tradeoff between stealth and performance translates directly to the world of fighter aircraft where less money needs to be spent pursuing qualities such as speed, agility and other aspects of performance that matter more in direct combat engagement. A stealth bomber makes more sense than a stealth fighter. Here’s a B-2 doing what bombers do. Invisibility is compromised when the bomb bays are open. A moot point.

Stealth has many dimensions. As we shall see. 

1. Hiding

Oswald Boelcke, a German fighter ace during World War I, was the first to publish the basic rules for aerial combat manoeuvring in 1916, known as the Dicta Boelcke.

His tactic No. 1 was “Try to secure the upper hand before attacking.” Without all-seeing devices like radar, a pilot could approach his foe stealthily, using clouds, haze or even using the enemy aircraft’s own wings or tail to conceal his approach. Much like the cheetah above. Much like drones.

2. Camouflage

THE FUR OF POLAR BEARS IS NOT WHITE. The hairs are hollow and transparent and look white because the air inside in refracts light of all visible spectrum colours so that the fur appears white. Much like what happens with snow. White works for polar bears.

Many military aircraft [are] painted to match the sky when viewed from below, and to either match the ground or break up the aircraft’s outline when viewed from above. This is known as countershading.

The undersides of night bombers were often painted black.

All aircraft camouflage paint is matte in order to reflect less light but the increased roughness adds parasitic drag which reduces aircraft speed and range. A de Havilland Mosquito’s top speed was reduced more than 20 mph (32 km/h) when using special night finish. This is a clear trade-off between stealth performance and speed performance. And it’s okay because stealth performance reduces the need for speed performance. Like with the polar bears, stealth makes speed less necessary.

Here’s an example of recent developments in camouflage – the invisibility fabric by the Hyperstealth company. [Passing Q: What would happen to the concept of architecture if buildings could do this?] Note how the lady has, possibly hedging her bets, also made an excellent choice of camo daks.

Details of the invisibility fabric are no doubt classified, but it is likely to involve multiple refractions in much the same way as described here.

Here’s a chair in front of a trashcan.

These are relatively crude methods of giving an object the pattern of what’s behind it, effectively making it invisible. There’s been some success with research for how to do this at the quantum level but don’t get too excited.

3. Disruption

Dazzle camouflage was designed so an enemy couldn’t instantly perceive the outline of the aircraft (or ship) and so anticipate its direction and speed of travel in order to fire where the target is going to be. A reduced ability to strike fast is a reduced ability to strike first.

Combining the tactics of hiding and disorientation, Boelcke advised pilots to attack from the direction of the sun. Here’s a gratuitous but nice image of an SU-something.

Flying at night is a form of stealth by disorientation since in darkness there’s no light and hence no colour to deduce an outline and thus direction of travel – or, for that matter, anything else visual.

The above examples all had to do with THE APPEARANCE IN THE VISIBLE SPECTRUM of aggressive animals, aircraft and building development. However, stealth involves other attributes and other senses that can’t be ignored.

4. Radar invisibility

This, obviously applies to the military world and not the natural one. (Bats do sonar, remember.) The B-2 is always a good example of radar stealth.

Other interesting facts about the B-2:

• The B-2s carbon-graphite composite material is stronger than steel and lighter than aluminium and absorbs a significant amount of radar energy. The B-2 reportedly has a radar signature of about 0.1 m2.
• The B-2’s engines are buried within its wing to conceal the engines’ fans and minimize the thermal visibility of the exhaust.
• The B-2’s clean low-drag flying wing configuration also helps to reduce the radar profile.
• The B-2 is manufactured to extremely high tolerances to minimise fuel leaks that could increase its radar signature.
• In order to protect the operational integrity of its sophisticated radar absorbent material and coatings, each B-2 is kept inside a climate-controlled hangar large enough to accommodate its 172-foot (52 m) wingspan.

This last point is interesting. Just like the tradeoff between non-reflective paint increased drag and fuel-consumption on earlier aircraft, the use of radar-invisible coatings also has its own operational cost. Best not fly too close to the sun!

4. Quietness

It’s a standard tactic of any kind of hunting to not make any noise. If you’re the hunter, you’ll try to not tread on twigs and stuff. You’ll also be careful not to scare any animals you aren’t interested in since they might panic and alert the ones you are.

Keeping quiet is especially important for submarines as water transmits sound more readily than air. The problem with submarines is engine noise and development for ‘fifth generation’ submarines is leading towards nuclear power plants powering an electric drive that replaces the direct mechanical connection between the nuclear-powered steam turbines and the propellers. Noise is a non-issue with aircraft travelling faster than the speed of sound. Buildings themselves don’t make any noise but their construction and mechanical services certainly do and the activities they contain might. We might say “I think we’re getting close to the stadium” or “the club must be somewhere around here” but humans don’t generally notice buildings by their sound.

5. Smell

For any predator whether lion, bear or smelly human, it’s standard procedure to stalk the target from the downwind direction.

6: Infra-red footprint: 

Again, the B-2 has its engines top-mounted to reduce their thermal visibility.  Here’s the latest thing in cloaking – a tank giving off the same infra-red signature as a car. Wot a crazy ol’ world eh?

• • • 

Stealth involves selecting the best combination of strategies. The route of attack that’s least visible, best camouflaged, most disorienting or that provides the best sound cover might not be the one for which the direction of the wind is favourable. This is an important aspect of stealth. Stealth requires a comprehensive evaluation of which methods or combination of methods is best for any situation. 

• • • 

So what’s this got to do with buildings then? Buildings don’t generally move, they’re not hunters by nature, and they don’t generally attack first. However, if they are to gain municipal approval and thus exist, it’s often advantageous if they appear to show a more benign face to the world and try not to appear as the buildings they really are. This is STEALTH in that it enables development by stealth. This is no mere wordplay – development IS aggressive. Once developments of a certain type or scale are permitted, they become precedents for less benign developments. It is then that, in effortless metaphor, developers show their true colours. 

Here’s an example of colour being used in order to be looked upon more favourably. Looking at this, we’re not fooled at all but we might just think “Well at least they tried.”

We’re all used to mirror glass buildings by now but it was once believed that mirror glass reduced the visual impact of a building. Here’s a classic example.

If you want to build a private house in a national park, then having it bury itself in the land and mimic the shape of that land and the pattern of the sky will probably work to your advantage.

Position and alignment can also be contrived to make development less aggressive. This is Paktau Architects‘ winning proposal for some visitor cottages near the hallowed ground of Fallingwater.

These last two examples are examples of development that ‘keeps its head down’ and doesn’t call attention to itself by being larger than anything else around. Development in the vicinity of protected buildings often has to do this and more lest it be deemed aggressive and overpowering.

CONCLUSION: We should not trust building developments that make a big noise about minimising their visual impact. They’re probably up to no good. Far better to see them for what they are before it’s too late.