Answers to questions relating to the core technology and operation of SkyLifters.
What is HTA and LTA?
As illustrated below, aircraft can be grouped into two categories, HTA (heavier-than-air) and LTA (lighter-than-air). Generally, HTA aircraft use aerodynamic lift and/or thrust to fly, whereas LTA aircraft use aerostatic lift for flying and only use thrust for moving through the air. SkyLifters are 100% LTA.
Why are SkyLifters not the usual cigar shape of airships and blimps?
We created the design to do a specific job, well. It is easy to start a design with a pre-conceived idea of what it should look like, but we started with a list of things the aircraft needed to do. Top of the list is the ability to pick up and put down payloads safely. Second, is the ability to do that in variable wind and weather conditions. Third, is the need for the aircraft to be practical to build and to operate; and so the list goes on… In summary, you start to realise that the usual cigar/torpedo shape is not the ideal shape for our tasks, and in fact, those shapes cause you more problems that then need to be solved with yet more engineering.
How do SkyLifters fly (float)?
SkyLifters use aerostatic lift to remain airborne and propellers are used to direct their flight. There is no need for aerodynamic lift, but the aerostat is shaped to minimise drag. Indeed, there is no need for wings, fins or control surfaces. The aerostat’s envelope (a balloon) contains Lighter-Than-Air (LTA) gas that enables buoyancy, derived from the surrounding air according to Archimedes’ principle.
Archimedes’ principle states “a body floating or submerged in a liquid is buoyed up by a force equal to the weight of the liquid displaced.” In this respect the atmosphere (air) behaves like the liquid.
Is LTA better than HTA?
As illustrated above, LTA technology enables three unique capabilities. For some payloads, LTA is the only solution:
- Flight duration greater than 24 hours (with a useful payload).
- Ability to remain airborne without power (enabling endless, sustainable flight with no additional energy expended).
- Vertical pick-up and flight of payloads well over 20,000 kg (which is the maximum payload limit for the largest helicopters).
100% aerostatic lift is essential for vertical lifting and being able to hover in un-moving air. During flight it may be useful to create some aerodynamic lift, but this usually requires additional items on the aircraft that add weight and maintenance and control issues, all of which need engineering solutions, certification and maintenance.
Below, are two simple graphics to illustrate the unique economic advantages of LTA over HTA.
Do SkyLifters have pilots?
SkyLifter aircraft will have two pilot positions, but we are designing them to be operable by a single pilot or even remotely if needed. Clearances for flight are similar to those of helicopter operations, because SkyLifters can also move slowly and hover. The flight deck is the circular room seen under the main pod systems module. This position gives the crew a 360-degree view of the surrounding airspace and ground operations.
What materials are used to make SkyLifters?
A SkyLifter’s aerostat is an inflated envelope made from strong, laminated ‘gas-tight’ fabric. The chambers inside are made of similar materials, but are of lighter weight. The pod below – the underslung module – is mostly metallic, a typical aluminium airframe, and incorporates composite mouldings. The suspension lines, which are strong synthetic-fibre ropes, are similar to ships’ mooring lines.
How will SkyLifters be built?
The hangars in which SkyLifters are assembled will be large air-pressure stabilised domes, as seen in a video on the Technology page. These temporary buildings are ideal, as they are low-cost and mobile. Additionally, while designs of the past have required large static hangars for maintenance work, the SkyLifter aerostat acts as its own shelter when moored and fitted with a ground skirt.
How do SkyLifters move forwards and backwards?
The propellers will thrust in any direction desired. The aircraft remains upright when moving forwards, backwards, sideways, up, down or rotating around its vertical axis. Due to the aerostat’s lenticular profile it has no apparent front, side or back. Therefore, SkyLifters are omni-directional.
This omni-directional characteristic has benefits (over the common cigar-shape airship) because it makes geo-stationary positioning (and the ability to pickup or deliver payloads) much easier. Without a front or back, the aircraft is always facing into wind. Vectored thrust from the cycloidal propellers ensures changes to wind direction are easily countered without any need to turn, and with much less chance of being blown off station. It is ideal for applications at any altitude.
Changes to compass heading, acceleration and slowing all happen very gradually and gently, so G-forces are small.
How do SkyLifters move up and down?
Ballast is adjusted so the SkyLifter weighs (including any payload) a little more than the buoyancy created by the aerostat. Then, the propellers provide some vertical thrust to ascend or assist with descending. The effect of the SkyLifter’s aerostat-shape limits descent rate, even when overall weight is substantially greater than buoyancy. This means it will descend safely without power if desired.
What is used for fuel and power?
We design to minimise carbon emissions and so SkyLifters are designed to use solar collectors to generate electricity, which powers the propellers and aircraft systems. The aerostat design is ideal for large arrays of solar collectors because a large portion of the upper surface faces the sun at any one time (more so than cigar-shaped aerostats, which can be hampered by the need to face the direction of flight). As a safety backup, a small engine and generator may be used.
How will SkyLifters land?
Being an LTA gas-filled airship, a SkyLifter never truly lands, remaining airborne throughout its life, buoyed up by the atmosphere. However, it can be grounded when it is restrained by mooring lines to the ground. Otherwise, similar to a helicopter, SkyLifters are designed to hold a stationary position in the air over a landing site and descend vertically.
No runway is required. During payload pickup and delivery SkyLifters will not be grounded; they will float (like a hover situation) close to the ground. Seen under the pod are ‘fenders’ to cushion and protect the pod when SkyLifters eventually land.
How is the mooring of a SkyLifter different to a conventional airship? (Parking a SkyLifter)
SkyLifters can be moored in a fixed circular arrangement with lines at positions around the edge of the aerostat to anchor points on the ground. The fixed arrangement facilitates ease of maintenance compared with conventional airships, which swing and bounce at a mooring mast.
Should I have concerns about large payload aircraft flying over my house?
Yes, but it should be no more concerning than a winged flying over your home. Safety is paramount with SkyLifters. The aircraft will incorporate safety factors and fail-safe methods, and will be certified to similar standards as all other aircraft. If a SkyLifter’s propulsion system stops, it will simply continue floating with the wind (like a common gas balloon). If the aerostat gets a hole, the aircraft will eventually quietly descend to the ground with its descent rate controlled by the release of ballast and vectored thrust.
I am looking for information regarding the following…
- operational cost models
- finance and insurance arrangements
- certification and compliance requirements
- weather and environment tolerance
- flight characteristics
- aerodynamic and stress models
- propulsion & fuel statistics
- load exchange procedures
We understand there is a keen and active community of aviation enthusiasts who would like to examine the technical data but the information is commercially sensitive so will not be published at this stage of development. If you are a potential customer or operator, please feel free to contact us for this information.