Floating cranes: SkyLifter’s plans for the construction industry

Deep Dive

Airships and balloons were around long before anyone saw a plane flying.

The French Army flew an airship named La France in 1884, and the first hot air balloon flew in 1783. But a series of high profile crashes like the Hindenburg and R101, and the considerably faster evolution of aircraft saw airships fall out of favour (except for a subsection of the marketing industry).

Hot air balloons aren’t known for their ease of navigation or speed, and airships, whilst easier to control and faster, are still too slow to have a meaningful impact on the markets they have been targeting up to now.

All that being said, UK-based startup SkyLifter thinks it has a found a new use case. Deciding there was no aerospace use case that could be improved versus what is currently available today for passengers, cargo and earth observation, the firm identified a niche in the construction industry it thinks can only be exploited by the capabilities of airship technology.

The startup is building a “commercial hook-in-the-sky system” made up of a gas-filled omni-directional lenticular-shaped aerostat (aka lighter-than-air aircraft) with an underslung pod housing the propulsion system, winch and hook. The pod, which also serves to aid the craft’s stability by increasing the vertical distance between the centre of buoyancy and the centre of gravity, houses the main aircraft systems for power, control and communication.

SkyLifter’s omni-directional propellers enable thrust in all directions and allow it to achieve an airspeed of about 45 knots (51mph). There is also the option to float “endlessly” without power, according to founder and CEO Jeremy Fitton, “at least in theory”. 

“We are using this system specifically for the heavy lifting of oversize external payloads. Target customers have also expressed a desire to move their payloads some distance so there is also a concept-of-operations for that requirement. But essentially it is a lifting device. We’re putting a hook in the sky that breaks through the payload limits of rotorcraft.” 

The benefits of using lighter-than-air (LTA) technology boil down to three things, explains Fitton. The first is the ability to lift more than the 20t practical limit of helicopters. The second is the neutral buoyancy of the airship, meaning it doesn’t take sustained energy consumption to sustain altitude (think Archimedes theory of displacement). In SkyLifter’s case the aim is to avoid aerodynamic lift and focus on aerostatic lift. Third is, because of the long flight duration capability, the platform is well suited to earth-observation, data-gathering use cases – similar to the role many satellites perform except with more sensor resolution for less cost (and easier to maintain and upgrade).

“Historically when you move things around using an aircraft, the aircraft is the most expensive piece of your supply chain and therefore everything revolves around that. Whereas in the SkyLifter case because the aircraft is floating around in the sky it can loiter until it is required. Thus the economics of the construction supply chain can be fundamentally changed for the benefit of the customer.” 

The company has not yet revealed what materials it is using to construct the aerostat, but Fitton confirms they are all historically proven and available in the airship world. It has also not disclosed which gas the balloon will be filled with. “We have been researching for many years looking at what has not worked historically. In recent decades there have been many projects and not many are flying today, predominantly because their operational capability is limited by their design and outperformed by alternative technologies. 

“We went for a spherical balloon as this is the shape the gas inside naturally wants to form, and it is easiest to build. An inflated torus (like a bicycle inner tube) helps form the ellipsoid. That gives the balloon that disk shape that you can see today in our illustrations.” 

Fitton decided on the underslung pod because it gives the aircraft stability. He saus early tests show pitch and yaw is minimised. “The aircraft is designed to fly in an upright attitude, with the propulsion creating heave and tow. These are maritime terms because the air system is floating in the sky and not using aerodynamics to remain airborne.” 

So if almost all of the components that go into building the aircraft are already available, what intellectual property (IP) does SkyLifter have to boast? The answer is in the concept of operations. Fitton says it is in the buoyancy management when loading and unloading, and the software that controls and coordinates the air systems and the hook. Most airships are designed to be landed in order to take on their payloads, mainly to minimise the movement of the hook in relation to the ground (think changing wind direction or turbulence). “Landing is a costly process, requiring quite a lot of infrastructure on the ground.” To mitigate this, Fitton pivoted the concept of operations: SkyLifter remains flying during payload transition ops. That in itself is not new, but the detail of how this is achieved is being patented by SkyLifter. The firm is also developing IP around the management software of its flight-control system.

“Effectively you have a balloon system with a fuselage underneath – which is the heavy part of the aircraft – then you’ve got a hook below that. So if you’re familiar with helicopter long-line operations you will know that payload can swing as a pendulum which creates a challenge for pilots to land it.” As a hook in the sky, the hook stability is the most important aspect of the design. “It is what the customer is paying for at the end of the day. So we have put a lot of time into designing a concept that will keep that hook at least as stable and steady as current land crane hooks.” The firm says it will be able to reveal more about the mechanics later down the line.

Already in conversations with the UK CAA, EASA and several other regulators, SkyLifter will follow the existing European airship certification plan (CS-30, CS-31HA) with a few modifications. “We’re building this air system within the aerospace framework that already exists,” says Fitton.

Anyone living in the UK knows we are no strangers to bad weather, the same can be said for a lot of the world. Airships and hot air balloons are filled with lighter than air gas in order to float, so what happens when it gets windy? Fitton says SkyLifter will be subject to the same limitations as conventional aircraft. “Generally speaking it can be likened to sailing a yacht, you use the wind to your advantage as much as you can,” he says. “As wind speeds escalate, land crane operations must exercise caution or cease entirely. SkyLifter, on the other hand, is capable of operating in higher wind speeds than traditional land cranes.”

According to a Readers Digest article from 2021, there were about 25 airships still in existence in the whole of the US. The number of construction developments at any one time in large cities such as New York and London far exceeds 25. So if SkyLifter secures its niche in the construction sector, airships might become a more familiar sight than ever before.

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