Airships – Challenges to Overcome

It is abundantly clear that airships have great potential, despite being slower than airplanes. Airships are relatively fast, capable of crossing oceans and able to hover. They are fuel efficient, with huge cargo bays, and require less infrastructure than competing modes of transport. Despite these clear benefits, implementation has been difficult. Four challenges confront the industry: the lifting gas; dealing with wind; controlling buoyancy; and most importantly, managing the innovation process in the absence of downward scalability. Challenge 1. Choosing a Lifting Gas The Hindenburg accident in 1937 did not singlehandedly end the golden age of giant airships, but it was an important factor. Efforts by the Allies to vilify the Nazis’ use of hydrogen gas, left a deep impression in the public consciousness that hydrogen-filled airships are irredeemably dangerous: a Hindenburg phobia. The American government, which possessed the only source of helium at that time, had been convinced by its suppliers to ban hydrogen as early as 1922, so they could obtain a market for helium gas. This was a political decision based on neither any scientific nor any engineering basis. Following WW2, when the US FAA became the predominant air certification regulator, the ban on hydrogen was “rubber stamped” into the air regulations around the world. This leaves helium as the only legal option for an airship to be built today. Helium gas is the perfect antidote to Hindenburg phobia because it is chemically inert, and therefore completely non-flammable. It has even been used in fire extinguishers. But helium is a rare, expensive and non-renewable resource with high value uses in the manufacture of computer chips and fibre optic cable, along with operation of MRIs and airbags. It would get even more expensive if it were extensively used in airships. Some estimates of helium deposits in the earth’s crust suggest that large amounts exist. This may be true, but it is expensive to refine and only a few places have concentrations of helium that are economic to extract, even at the current high price. It also contributes less lift because it is slightly heavier than hydrogen. While helium airships are an interim possibility, the world urgently needs to reconsider the case for hydrogen airships. As one of the elements in water, hydrogen is abundant and relatively easy to refine. It would be uneconomic for a helium-filled airship to release helium for buoyancy control, but an airship using hydrogen for fuel and lift could conveniently vent gas for control. Refueling stations could conduct electrolysis anywhere there is water and generate hydrogen to replenish the airship’s supply. Hydrogen is much less dangerous than most people think. Hydrogen is not flammable unless mixed with air in ratios between 4% and 75%. By comparison, gasoline fumes will ignite in the air at a 1% concentration. In a rigid airship, the lifting gas is not pressurized, so even if there is a leak, it will be very slow and quickly dissipate. As for the upper level of danger, no airship could fly with less than 95% to 99% pure hydrogen. This explains why in the 40 years that hydrogen-filled airships flew worldwide, only one accident of the Hindenburg kind occurred. Moreover, it is now well-established that hydrogen did not cause the Hindenburg fire. Rather, static electricity ignited the flammable paint that had been used to coat the exterior envelope, a tragic and avoidable mistake. As climate change concerns have increased, more hydrogen gas is being used in fuel cells to power fork-lifts, cars, buses and even a train in Germany. A hydrogen-electric airship could become a practical long distance, heavy lift form of air transport with zero carbon emissions, a feat hard to achieve any other way. The difference between a hydrogen fuel tank and a hydrogen gas cell in an airship is only the pressure and materials. Today, we have the technology to do both safely. More generally, modern technological civilization routinely involves harnessing natural phenomena that ought to be dangerous. Our cities are criss-crossed and woven through with webs of wires that touch every house and carry enough voltage to kill anyone who touches them. We live surrounded by lethal perils which have been tamed for human use through technological ingenuity. A hydrogen-filled airship is less inherently dangerous than an airplane. If an airplane’s engines fail, or its computer software crashes, it can result in the complete loss of life for all on board. Because airships do not rely upon engine power to stay aloft, engine failure represents a far less catastrophic risk. A leak in an airship would be handled similarly to bulkheads in a large ocean vessel, any leaking area would be locked out and buoyancy control re-established through remaining gas cells. Challenge 2. Dealing with Wind Suppose you are camping, when suddenly a strong wind starts up. The picnic table is safe enough, along with you cooler, even the campfire skillet. Your tent however, unless it is well staked to the ground, is likely to blow away. This is because the tent is more like a sail than a house – it lacks inertia to resist the drag. Airships are similar in that their large profile acts like a sail and will swing at a mast to point the nose into the wind. Of course, their engines should have top speeds faster than any but the strongest winds, enabling them to fly in the face of strong winds, albeit with slower progress. The opposite is true in a tailwind that can add to the speed obtained from the propellers. A biography of the great Zeppelin commander Hugo Eckener describes him as playing “stratospheric chess” with the elements. These days computer programs, coupled with weather forecasting, can plot the optimal course and take advantage of the winds, as Eckener became skilled at doing. Dealing with winds during ground-handling, mooring and entering/exiting hangars can prove problematic. GPS and modern avionics should be able to direct multiple propellers to hold the airship steady and control its movements without any ground crews holding ropes. Equipping giant airships with an ability to retain adequate control and avoid accidents on the ground in high winds remains a challenge for airship designers. The hybrid airship Airlander 10 was damaged in 2017 when it broke free from its moorings in a high wind. Challenge 3. Buoyancy Control The “ship” portion of airship is where we see more parallels to ocean dwelling vessels, they both share a need for buoyancy control. Aerostatic flight depends on being lighter than air, so appropriate ballast is critical. In order to manage its altitude or land, an airship needs to be able to manage its weight relative to the surrounding air. The options for doing so can include: adjusting ballast, compressing air or the lifting gas, changing the temperature of the lifting gas or simply releasing it into the atmosphere. In addition to changing buoyancy, an airship can use its propellers to force the airship up or down, especially during landing and take-off. A great many ideas have been put forward, and many of these are coupled with the structural design and ground-handling systems that are being proposed. This topic will be discussed in more depth in a future article. Challenge 4. Scalability and the Innovation Process Prototypes and proofs of concept are heavily relied on in the usual development process for new technologies. This is often referred to as the Minimal Viable Product (MVP). It is often more economic to attempt a new design on a smaller scale, before investing in a commercial size. Silicon Valley venture capitalists realize this principle through a complex ecology of founders and incubators and accelerators. Investment runs from seed capital and venture capital Round A and Round B to late stage venture capital investors to bring forth new products. In this versatile and multifaceted way, ideas can be tried, and their value discerned. Typically, it takes a few million dollars to make the MVP, or put it on the shelf. It works well for the software industry, but does not work at all for airships.