Flying with the wind
By Kim Krogtoft, Head of Operations.
Imagine gliding through the air – low, slow, and not a sound other than the nature around you and your own breathing. Looking out of the panoramic windows of a giant airship – the ocean, the ice, and wildlife such as whales and polar bears, as well as breathtaking views.
It sounds like a dream, but it will soon be a reality for experienced travellers who enjoy flying with the wind! In this article, we’ll explore what it’s like to fly with the wind into the deep wilderness and travel with a smaller footprint on board a large-scale airship.
This archipelago, located in the Arctic Ocean, is 60% covered by glaciers and consists of several islands, only three of which are inhabited. Its capital, Longyearbyen, is home to about 2,000 people from some 50 countries and it is the northernmost city in the world. On Svalbard, it is said that there are three seasons throughout the year: “Polar summer, Northern Lights winter and Sunny winter”. The inhabitants of these islands live with four months of darkness per year and four months of light 24 hours a day. The climate is very extreme with temperatures ranging from -14 degrees Celsius in winter to 6 degrees Celsius in summer.
The global wind system
The global wind system is a never-ending source of renewable energy that can be harnessed to power everything from small electronic devices to entire cities. It is also beneficial for airships. The key to harnessing this power is understanding how the global wind system works.
The global wind system is made up of three main layers: the surface layer, the middle layer, and the upper layer. We will operate in the “surface layer” with airships at from 0 to 10,000 feet/3,000 m. These winds are caused by the uneven heating of the Earth’s surface by the sun. The warm air rises and the cool air sinks, creating high and low-pressure areas.
The difference in pressure creates a force that moves air masses. When we are on the ground, we experience moving air masses as wind in a different way than when we fly. Close to the ground, the wind is affected by trees, hills, buildings, etc., which causes changes in the direction of the wind and creates turbulence.
The change of direction is due to the “Coriolis effect”. It is the effect that gives the atmosphere’s path an apparent deflection which derives from the spinning of the Earth – clockwise in the northern hemisphere and counter-clockwise in the southern hemisphere. Close to the Earth’s surface, the Coriolis effect is diminished by the friction with the ground, thus twisting the direction of the wind. This effect diminishes the further away we get from the ground. Wind direction differs approximately 30-40 degrees between ground level and 2,000 feet.
When we move away from the ground e.g. in a hot air balloon, we find ourselves inside an airmass. The reference to ground disappears and we drift with the airmass, not experiencing it as wind, but rather as a drift relative to the ground. Since the balloon has no means of propulsion itself, it depends on the direction of the wind as a means of control.
Since the direction of the wind changes with height, and due to the ground’s friction and the Coriolis effect, the skipper of the balloon can make use of his knowledge and change the height of the balloon in order to change the direction he wants to fly relative to the ground. An airship can use the same knowledge and techniques as hot air balloons, and can thus increase the tailwind, or at least decrease, the headwind.
Airships and the wind
An airship’s gondola is not pressurized, as on a passenger plane. Therefore, airships and non-pressurized aircraft fly up to a maximum altitude of 10,000 feet, corresponding to approximately 3,000 m. The wind here, in these low altitudes, will be changeable compared to higher altitudes. We use that when we navigate the airship.
Knowing the weather and wind at the different altitudes is very important and one of the major tasks in order to operate an airship as safely and efficiently as possible. Flying faster with a tailwind and more slowly with a headwind sounds logical, but the exciting and challenging part is finding and calculating the right altitudes.
With the knowledge we have from the airship era and with modern aids serving us with global and accurate weather prediction, together with the pilots’ many years of experience in modern aviation, we take advantage of every opportunity to navigate and fly safely, while optimizing the economy and footprint of each of our operations helping modern large-scale airships to become even more efficient in our time.
Graf Zeppelin used pressure pattern navigation when approaching storms and other weather systems. When the airship was heading east, the crew would bypass the storm on one side and hug the western edge of it to gain a tailwind. When heading west, they would keep their distance from the storm by going around its southern edge to gain an advantage in the form of a headwind.
The shortest distance between two points on the Earth’s surface is a great circle (or part of it). When we operate airships, we use the same as when crossing the oceans with sailboats, and with this knowledge, we look for and prefer tailwinds, avoiding headwinds. This means that we may have to fly a longer distance, but in return, we arrive faster, thus saving energy.
For example, on a sailboat regatta race from Cork in Ireland to the Bahamas, the shortest distance is 3380NM – a great circle. When looking at the wind direction for the routing, you see it consists mostly of head -, cross,- or 0-wind, and with an average of 5 knots, it will take 28 days.
But if you study the wind maps, and change the route so that you achieve a more optimal wind direction, the sailed distance is increased by 620 NM (approx. 1150 km), but on the other hand, it takes approximately 17 days, saving in time of 11 days. This is an example of how to use the wind when crossing the great oceans. Airships can also take advantage of the changing wind speed and direction similar to the way sailboats do. They can also use lateral navigation planning to optimize for beneficial wind as well as vertical navigation. Airships can therefore optimize wind patterns even more efficiently than sailboats through navigation in a 3-dimensional space.
Aviation must be sustainable. Our goal is to provide a new concept of flying, disrupting fossil fuel consumption. We believe lighter-than-air technology is the way forward to achieve this.
OceanSky Cruises, Head of Operations
Captain Kim Krogtoft has been a Commercial Pilot for 44 years in operational, start-up and management roles, and still flying Boeing 737. He is an entrepreneurial, adventurous aviator and former Maersk Air Captain, where he served as a member of the Board for 12 years and Chairman for the fixed wing and helicopter pilots in the North Sea.