S5C8: Ports & Airports

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a) Checking and entering

In some places, one may board a boat without questions asked. Just walk over the ramp and step in, show your ticket and take whichever seat is available. At the extreme end, one can take an hour just to check-in at a counter and make it to the boarding gate in a gigantic airport and some modern freight ports have an infrastructure covering many square kilometres with countless cranes standing guard. Somewhere in between would be a small, human-sized airport with a more relaxed atmosphere and much faster overall process from the moment you reach all the way to the time you enter the plane. In this chapter, we’ll try to understand why ports and airports are laid out and organized the way they are and, in the first place, the purpose they serve.

When you take a flight or a boat ride, what you are effectively doing is temporarily following a transport route, often part of a large network and this journey may require stopping on the way, at a node in the network, for transhipment and following a second route. Ports and airports are the gateways and nodes in these maritime or air transport networks, they manage the entrance of passengers or cargo, their potential trans-shipment along the way and, eventually, their exit from the network. Such a network can be domestic only, or have a mix of domestic and international segments.

The international aspect immediately adds a requirement for an immigration processing channel that each passenger has to go through and, under normal circumstances, there isn’t the option to go back the other way. For safety considerations, the same channelling and check is carried to ensure carry-on luggage and passengers do not carry explosives, firearms or other types of weapons on them. When immigration clearance is required, these two checks are carried out back-to-back and mark the entrance of passengers into the security clearance area or security restricted area (SRA), also called airside in an airport. This process relies on either face recognition, iris recognition or fingerprint scanning and is increasingly automated – you may want to read more about these technologies in S4 Section 9.e on biometric identification. On the other hand, the exiting passengers are not required to go through security but may still require immigration clearance, if their last trip leg was international, before they enter the landside part which also includes the check-in area.

The purpose of the check-in area is twofold: ensure that passengers and their potential luggage are provided with a ticket or tag so they can board the correct plane and an identification to ensure the ticket is being handed over to the person named on the booking. This booking aspect is important since, where no booking is needed, the ID check would be unnecessary but it only works well where regular services ply the same route, as with public buses where a first-in-line first-inside rule applies.

The size of the node where you are entering or exiting the network also has a dramatic impact on the required infrastructure. This size is a function of the flight density and depends on the number of total routes operated per day through this port or airport. This explains why airports called hubs where some of the largest companies are based can be extremely large; indeed, every single transferring passenger is effectively using the airport twice, once to land and once to take off. This hub and trans-shipment mechanism applies less to maritime transport of passengers but it is quite prevalent for freight, as we will see in the next section.

We have so far looked at the terminal layout and passenger flow and not yet at the area where the boats and plane are operated. This is called the apron and in a port it is essentially the wharf or pier used for embarking passengers or loading cargo (and of course, disembarking and unloading), whereas in an airport it would span the runway, the various lanes for the movement of vehicles as well as the maintenance hangars, the refuelling area and the boarding or deplaning bays.

Whether it is ports or airports, all this infrastructure and operations need to be paid for. For airports, this is achieved through a mix of fees levied on a per passenger basis and imposed on each aircraft as it lands, parks and uses an aerobridge. In addition, those are supplemented by non-aeronautical revenues including the commercial rental of shops and restaurants, car parking on the landside, and potentially the mark up of jet fuel sales to airlines.

b) Maritime freight handling

Handling passengers and cargoes are not just two different businesses, they require different management, operations and equipment. There are also marked differences between various types of cargo so they tend to be segregated into specialized terminals. For ports, there might be a cruise terminal with high passenger throughput and deep draft and for roll-on roll-off ferries there needs to be a road access and ramp for vehicles to board. When it comes to cargo, ports are also much more likely to have specialized layout and infrastructure for the simple reason that the sheer volume and weight of the payloads is generally multiple times that of aircraft.

For example, dry bulk terminals would use bulk-handling cranes fitted with a shell grab or bucket and accommodate mid-sized ships or even barges. For container ships, the size of piers needs to be dramatically increased and so does the height of the handling cranes; forklifts are not going to cut it. If you have not seen one of them before, you may want to look for pictures of container cranes lined up along a container ship, it is quite a sight to behold and such equipment very quickly illustrates the massive productivity gains as compared to the days of back-breaking human labour. These huge cranes are mounted on rails and, in a perfectly synchronized scenario, they could tranship containers in one go, though in practice the containers would first be picked up from the ship, stored in a yard or warehouse and then either lifted on a truck for delivery by a reach stacker or picked up again and placed onto another ship for further transport. If you have not already read it, you may want to refer to S5 Section 4.a on the containerization of freight to learn more about the reasons behind this trend and the ships involved.

Fluid cargo coming in by tanker also requires specific infrastructure but in many ways is much more efficient to transfer: pipe the ammonia or hydrocarbons in or out. I am of course somewhat simplifying here and there is cleaning to be done and some very specific materials, insulation and procedures may need to be used, such as with LNG cooled to -162° C. This explains why refineries are often located in close proximity to existing port infrastructure: the unrefined and refined products can be piped directly between the storage tanks and the ships.

Storage is not merely for liquids and warehouses are an integral part of a port’s operations, they are the equivalent of the waiting area in passenger terminals, waiting till the scheduled craft shows up to the gate to board. In order to avoid having to unnecessarily clear custom, especially in the case of trans-shipment, those warehouses can be bonded, meaning import duties are not yet paid and the goods can be reexported without being taxed. Like a layover on a multi-leg plane journey.

At the time of this writing, the largest port in the world is Shanghai with Singapore heading the league table for trans-shipment and containers while Rotterdam is the largest port in the world outside of Asia.

c) Traffic control and radar

In harbour and port areas, the approach and entrance of ships as well as their exit is generally overseen and guided by a vessel traffic service. In its absence, there would be frequent collisions with significant damages, including potentially loss of human life. This aspect is arguably even more crucial when it comes to airborne craft, therefore liaison with air traffic control (ATC) is absolutely indispensable.

Air traffic controllers are typically located in a control tower providing a clear view of the apron area and runway in particular, and each airport’s ATC directs aircraft within a certain controlled area, allocating landing slots depending on schedule, availability and, potentially, emergency situations. As for the operations within the airport, these are normally the preserve of the sibling ground control movement team.

The core principle ATC seeks to maintain is spatial separation of aircraft; if there are several runways this can entail different lanes of approach and take-off but otherwise all vectors will be lined up so separation in space implies separation in time, hence the allocation of different landing and take-off slots depending on existing traffic within the controlled airspace. On the pilot side, a set of rules does apply, just like for driving vehicles on a road, and these are based either on visual cues or data provided by instruments in the cockpit. The former is called visual flight rules (VFR) and requires good weather conditions, especially visibility, while the latter is called instrument flight rules (IFR).

For the ATC to be in a position to take its decisions, which in theory could be replaced by algorithms (and this in no way diminishes the complexity of the job and the skillset required), there needs to be data available. The two primary means of obtaining such data are through verbal communication with the cockpit crew of aircraft, machine to machine communication between ATC computers and those onboard the aircraft, and radar.

The word radar started as an acronym for “radio detection and ranging” and its successful implementation during WW2 gave the British Royal Air Force a much-needed edge over the German Luftwaffe. Radar helps to detect the presence of an object in the air, its distance (this is the ranging aspect) and its velocity, a term capturing both the speed and the direction of motion of the object. This information is provided by first emitting radio waves in various directions and then receiving and analysing the reflected waves. Let’s break this down.

Radio waves are used in lieu of other electromagnetic radiations with shorter wavelength because they suffer less attenuation when travelling through the atmosphere. This is important for detecting objects at a significant distance. When those waves reach a surface, some of them are absorbed and some are scattered or reflected; I include a link to the Wikipedia entry for reflection if you wish to better understand the physics of this phenomenon that we already came across when discussing radio broadcasting (S4 Section 5.a) while the part on RFID (S4 Section 5.e) had a mention of backscattering. The same section on radio broadcasting also explained the principle of antenna as transceivers, meaning they both emit and receive electromagnetic waves.

When the signal has travelled a long distance, forth then back, it needs to be amplified before being analysed. When this has been done, distance can be established through timing – being the time it takes for the wave to hit the obstacle and return, which can be made easier to measure by overlaying frequency modulation. Imagine a function on a graph following a regular slope (here it would be an increase in frequency for example), if you have the frequency value on the y axis, you can reverse engineer the value of x on the time axis and dividing this last value by two gives you the one-way time of flight, from where the distance can be deduced based on the speed of light in the atmosphere. As for directionality, it can be inferred by scanning in specific directions or from the quality of the signal received by the antenna, knowing that the signal will be strongest when coming in from a direction perpendicular to the rod. Lastly, the presence of doppler shift will provide information regarding the velocity at which an object is approaching or moving away from the transceiver.

With all that written, we have also heard about stealth aircraft and submarines. If a radar can provide such detailed information, how can it be avoided? Well, avoided might not be the correct word, the objective is not to leave a meaningful signature or to create one that cannot be interpreted properly. The first trick is to use some radio-wave-absorbing material; the most effective material juxtaposes pyramid-shaped surfaces and actually does three things: absorb, attenuates and scatter. Let’s expand on this a little:

Lossy material absorbs incident electromagnetic waves;
Surfaces can be shaped so they reflect the waves onto each other, attenuating the strength with each bounce; and
The waves can be scattered away from the receiver or in a manner ensuring they become out of phase and partially offset each other out.

In addition, because thermal emissions can also be detected, a craft operating in stealth mode should reduce the thermal infrared footprint of its engine and exhaust as much as possible. Also, to close out this section, I would be remiss if I didn’t mention the smuggler’s action movies’ favourite technique: flying under the radar. In the jargon, the term used for this type of evasive low-altitude flight is “nap-of-the-earth” and it consists in flying in pockets the waves cannot reach, which is made easier by hills and other irregularities in the topography creating a radar shadow. So flying low is a stunt that may not be sufficient with a radar located at a meaningful altitude and the expression should rightfully be “flying under the radar horizon”.

d) Building ports and airports

An airport is much more than a runway, as we have clearly seen by now, it is a comprehensive package with many dependencies such as permitting and regulation, slot allocation to airlines, staffing and training, and of course the transport linkage to one or several cities and other networks. Even expansions are costly affairs and easily run into the hundreds of millions of dollars, if not more when a new terminal with large capacity is on the cards.

Building a brand-new airport can take anywhere between 15 and 30 years, including the planning and permitting phase. This would entail evaluating the environmental impact as well as the ramifications on surrounding communities, with traffic and noise being the main factors to consider. On the flip side of those problematic aspects are the local and regional economic benefits of such a large employment provider, directly and indirectly through the chain of sub-contractors and suppliers. So, the politicians want an airport, and the residents also but not in their backyard. The usual.

There are a lot of elements to build in an airport, and none of them are inexpensive. That said, some call for larger capital expenditures than others, including the levelling of land and potentially some reclaiming as was the case in Singapore or the Hong Kong airport based on the island of Chek Lap Kok. A long heavy-duty runway also requires a lot of manpower and material, so does the construction of a new terminal, in particular when an architectural statement is being made, and the luggage handling system comes with a hefty price tag and can delay the start of operations when not operating as intended. Lastly, the cost of building new transport links, including high-speed rail, can by itself be equally or even more expensive than the asset being connected. Hong Kong and the Shanghai Maglev to Pudong come to mind.

In the case of ports, many of the same regulatory, political and environmental issues arise, nonetheless the noise aspect is much less problematic as ships do not traverse residential areas, are not as noisy above ground and the cargo-handling ports tend to be surrounded by industrial areas. Those freight-centric assets drive the local manufacturing or mining businesses rather than tourism, while cruise-terminals are proving increasingly problematic with a seasonal daily surge in tourism leading to overcrowding and no spreading out of the associated benefits one would expect with visitors staying several nights with respect to accommodation, restauration and non-bucket list activities and sights. The large ticket items for ports are the dredging of deep-water berths, which can be very costly in shallow waters where the piers may need to extend a long way offshore, the building of breakwaters potentially, and the purchase of cranes for loading and unloading ships. No express transport link is required in general but connectivity remains important and a new port calls for additional roads and often new freight railway lines.

e) Future vertiports

From the very real to the more speculative future where both eVTOLs and airships become a common sight with proper infrastructure and increasingly integrated with other modes of transport and networks. For reference, if you have not already done so, I would recommend you read S5 Section 6.c on electric VTOLs (vertical take-off and landing aircraft) and S5 Section 6.e on airships or lighter-than-air crafts.

Based on the pros and cons of each mode of transport, the infrastructure costs associated to them as well as their respective operating expenditures on a passenger-kilometre basis, the way I could see inter-modality work is as follows:

Inner-city transport remains primarily the domain of mass rapid transit and autonomous buses. These are complemented by premium eVTOLs and shared taxi service in autonomous cars or vans with on-demand pick-up and drop-off algorithmically optimized to be competitive versus fully private point-to-point transport.
Connection to airports is done by train in locations where land acquisition and topography are not too much of a challenge and this can be replaced or supplemented by larger eVTOLs plying the trade from five to ten vertiports in a very large city.
Vertiports are attached to traditional airports for large passenger planes that cater to routes beyond the 500km range with the optimal range being determined based on several factors such as carbon footprint.
Beside airport runways for traditional planes, airports have shorter runways, or perhaps can even use vertiports infrastructure, for airships catering to the sub-500km range as well as to routes without sufficient load to justify an entire plane and that are not well served by the rail network.

I think this would work.

Vertiport was mentioned, yet we have not evaluated what these assets would look like. One reason for this is, of course, that they are still essentially at the conceptual stage. However, this doesn’t mean no progress is being made and, in fact, there are already guidelines by several civil aviation authorities regarding the safety aspects. Interestingly, the diagram they provide and the benchmark they are using is heliports, which makes total sense given the vertical approach motion. This has the clear benefit of reducing the footprint area of a vertiport versus an airport though there is still a need for a terminal with check-in, security and boarding infrastructure. Nevertheless, if the passenger capacity varies from as low as a handful to perhaps a couple of dozen passengers per aircraft, we could imagine a process and terminal size closer to a well-organized central bus station than to a full-fledged airport. No aerobridge required, fewer gates, mostly no immigration given the routes would likely not be international, and no or limited luggage handling.

As the technology matures and the aircraft manoeuvrability improves to the point of uber-reliability, then it would become possible to have several landing and take-off spots in relatively close proximity, possibly circling around the passenger terminal, or on top of it. Vertical stacking would be quite space efficient indeed.

f) Trivia – Aircraft carriers

The importance of air supremacy in naval warfare has been established early on. Planes can attack enemy ships and aircraft as well as help defend their own navy in the process. Ideally therefore, armed forces would want a co-moving airbase alongside their navy. The solution is obvious: aircraft carriers. But the realization is more complex and very expensive. Those countries who can afford it find it is unarguably worth it as it not only strengthens their naval forces but also helps project air power to large parts of the globe. Even though the dynamic is different, there is a clear analogy with submarines carrying nuclear warheads in terms of threat and geopolitical impact.

The primary differentiating factor between a standard military ship and an aircraft carrier is not the firepower, it is the presence of a flight deck from where aircraft can take off, and in most instances can also land. Runway length being a constraint, there are three options available for take-off: full gas, assisted take-off and vertical take-off. The assisted option relies on the presence of a catapult system imparting kinetic energy which helps the aircraft to achieve lift off speed. I include a link to the relevant Wikipedia entry at the end of the chapter if you are interested to read more about such technologies. Regarding landing, which is equally tricky over short distances, the easiest option is vertical landing and for more traditional fighter jets, braking would be assisted by steel wires spread across the landing area that would be caught by a hook located in the tail of the aircraft and the aircraft kinetic energy can thus be partially transferred to a hydraulic system.

Accordingly, aircraft carriers are divided across four categories: #1 short take-off barrier-arrested recovery, #2 catapult-assisted take-off barrier-arrested recovery (CATOBAR), #3 helicopter carrier, and #4 short take-off vertical-landing.

Since lift off is a function of relative or apparent wind speed, going fast and against the wind both help. In this respect, an aircraft carrier able to sail at high speed is helpful and can increase the payload an aircraft is able to carry. It also helps getting somewhere fast, or evading enemy forces.

To achieve the feat of moving such a massive object at speed and over long distances, the best alternative is undoubtedly nuclear propulsion. It can be used both to run a turbine and therefore the propeller via a gearbox mechanism, and to provide electricity vital to the running of the ship’s various functions. If you wish to know more about nuclear marine propulsion, I have included a link to the Wikipedia entry in the next section.