Technological development has reduced the barrier cost of entry of maritime sea control, resulting in a cluttered maritime environment and numerous challenges to the existing fleet. A low- to mid-altitude airship utilizing low-quality/low pressure steam as a lifting gas and off the shelf solar energy solutions may be used to ensure the fleet has the mobility, persistence, detectability, and survivability to ensure continued threat prevention.
Predict Game-Changing Technologies
The U.S. Navy long has been a global force for good. Its presence has been paramount in the long peace between the global powers since the end of World War II. Under its vigil, maritime commerce has never been higher and the sea lanes have never been busier; yet in that time, maritime violence has been at historic lows. However, that watch is now under challenge.
In centuries past, the barrier to entry into naval power projection was high. A country needed to field line-of-battle ships or aircraft carriers to control the oceans. Now, technology has lowered the bar and nations across the world can field drone swarms, missile attack boats, air independent propulsion (AIP) submarines, and rapidly weaponized container ships to quickly challenge any blue water navy.
Drone swarms have recently been used in field conditions, as Russian air defenses in Syria in 2018. Their simplicity and sheer numbers ensure they can overwhelm most air defenses by being cheaper and more numerous than the interception technologies can mitigate.
Missile attack boats range from one-man speed boats to frigate-class warships, and as experience in the Strait of Hormuz from 2005 to 2017 shows, they can close to lethal range of most naval ships at will. With sufficient numbers, in a crowded environment they can overwhelm a fleet specializing in blue water combat.
Many countries field small diesel-powered submarines with advanced air independent secondary propulsions systems such as Stirling engines or fuel cell technology. With the rise of alternative fuel technology, these submarines have become cheaper and quieter. Recent exercises with NATO allies have shown that these vessels can close with aircraft carrier battlegroups without detection.
Finally, many private defense contractors have begun to develop containerized weapon systems. These weapons can be antiship missiles, enclosed automatic cannons, or air defense systems. With them, any 100,000-ton container ship can be turned into a floating arsenal in days.
The U.S. Navy already has identified many of these challenges and has either developed weapon systems or entire ship classes to combat them. It is growing the number of combat ships to ensure continued maritime control. Yet, the need to meet these challenges leads to conflicting requirements. A vessel must be fast enough to reach station, persistent enough to remain, instrumented enough to survey all possible threats, survivable enough to engage, yet affordable enough to produce. The need to develop such an adaptable ship, such as the littoral combat ship program or new frigate competition has led to heartaches and headaches in the procurement community. Augmenting existing ships also has been problematic since there is only so much a finite number of ships can do.
Fortunately, the Navy has the ideal vessel to meet all these challenges, and it is finally feasibly to implement with application of recently developed technology. This vessel is a lighter-than-air ship, and the technology is a strange blend of steam power and advanced solar and battery power and modern materials.
Historic Background
From the 1910s through the 1930s, the world’s military powers experimented with rigid, lighter-than-air technology. As a land based weapon system, it was a failure. The airship was hopelessly outclassed by aircraft, easily detected by ground based systems, and dropped bombs were inaccurate. The cost and logistic tail of fielding such giants ensured they were perpetually vulnerable and underutilized. As a vehicle, it fails in almost every category when compared to a combat airplane. It would be a mistake, however, to compare air displacement vessels to aerodynamic lift-generating weapons. As the U.S. Navy of 1920–1930 showed it is more akin to a light “scout” cruiser and it excelled in such a role. Within the limits of the technology of the day, the Navy showed its many advantages.
The vessels were faster than any ship afloat and could range further and faster than an entire fleet. Since they could control their altitude, their sight horizon could be varied and the vessel could either scan or hide at will. They were not limited by coastlines and could ferry critical supplies to vessels in need. When paired with aircraft, they could lock down entire areas of oceans and also could act independently. For a time, the future of airships looked bright, but the technology of their time led to their downfall. All of the Navy’s purpose-built rigid air vessels, The USS Akron, the USS. Macon, and the USS Shenandoah were lost due to inclement weather. Much of theses loss could be attributed to the inexperience of the crews and failures in meteorological understanding, but mostly from complications due to the need to conserve helium.
The navy would continue to use lighter-than-air vessels operationally through the 1940s and 1950s. These smaller vessels proved their use in persistent surveillance, but the needs of helium proved more costly than their operational capability warranted. Even with the recent resurgent of interest in lighter-than-air technology, such as the Luftschiffbau Zeppelin GmbH company, Lockheed Martin’s heavy lifter, and the Navy’s recent experiments and experience with the MZ-3 blimp have been hampered by this limitation.
Past Limitations
Helium is the lightest of the noble gases, is completely inert, and is much lighter than atmospheric air at any pressure. It is an almost ideal lifting gas. It is however difficult to procure, and there may even be worldwide shortage in the coming decades. In addition, it is costly to use. As a noble gas, it will not bond to any substance, and will leak through most envelopes and storage systems. To prevent this, airship technology has spent enormous effort in containing it. Blimp fabric is an interwoven and pricey blend of synthetic fibers, and complex buoyancy management systems are used to ensure no helium is lost during altitude change and holding procedures. Airships commonly are sheltered in large purpose built hangars to prevent the need to transfer gases and to protect the sensitive envelopes from exposure. All this drives the cost of operations of such vessels to beyond the scope of feasibility.
Yet, helium is not the sole lifting gas. There are two additional methods to generate aerostatic lift; thermal lift and hydrogen. Thermal lift, or heated air, is the oldest method of achieving flight, and the simplest. Heated air displaces cold air and generates lift. Yet it is limited since the difference varies with temperature and altitude and never exceeds 15 pounds per cubic foot, severely limiting aircraft structure. In flight, energy must be continuously added to the envelope limiting range and endurance. Although thermal airships exist, they are too frail, slow, and unwieldly for anything other than novelty and niche applications.
In many ways, hydrogen was proven to be a more effective substitute. It was easy to generate from water supplies. Since it was easily procured, it could be vented as needed to control lift and the containing fabrics could be any substance that would hold shape. As such, construction and operating costs were heavily mitigated and hundreds of such vessels once were built. Yet, it has a tendency to disastrously react with atmospheric oxygen resulting in the tragic loss of those vessels, their crew, and their payload. Of note though, its chemical reaction product, steam, is very buoyant.
Technological Proposal
Steam instead of helium, hot air, or hydrogen can be used to provide lift for a future aerial-scout-cruiser-type vessel to augment the fleet. At low- to mid-altitude, steam provides a significant fraction of the lift capability as inert helium and does not have the violent combustion potential of hydrogen. When combined with several inherent properties of an airship, it can produce a synergy of complementary advantages that can be used to augment the fleet against future possible threats. By combining the inherent properties of an airship, the intrinsic properties of steam, the advantages of alternate energy technologies, an effective and affordable vessel may result.
An airship is the only known method of transportation whose effective solar area exceeds its power required for mobility. In other words, an airship has more surface area exposed to sunlight and more solar energy absorbed than is needed for mobility. To this day, most airships attempt to reflect this excess to prevent loss of lifting gas due to thermal expansion. If this solar energy was not reflected but absorbed both passively or actively and stored, an airship would have more on-board power than could be used by all but its payload systems.
Steam is self-insulating and requires substantial energy expended to condense onto a surface. Once the steam is generated, it requires a token amount of external energy to maintain its phase. Its condensation point varies with external pressure, dropping with pressure; this is convenient since atmospheric pressure drops with altitude as well. This means an airship would require less energy at altitude than it would at sea level. This advantage could be used until the external temperature increases the thermal flux to the point beyond the system’s ability to add heat. In addition its ease of generation ensures that it does not need to be critically maintained. In place of relatively heavy and expensive envelope fabrics, simple thermal airship fabric may be used. Two lightweight envelopes spaced apart would provide adequate containment and thermal insulation to ensure the lifting envelope is sufficient for the airship’s needs. The craft’s ease of use also increases, since the steam could be generated or vented on demand, the vessel could be trimmed for increment weather, or more buoyancy added to rise above it.
Lastly, lightweight solar cells, advanced batteries, electric motors, and modern structural optimization may be used to ensure the lifting gas is thermally maintained through day/night cycles, to ensure propulsion is adequate for mission needs, and may be used for payload function. The recent advances in environmentally friendly energies can be leveraged to provide energy storage and propulsion for the craft from off the shelf technology. If this is further augmented with aerodynamic fairings utilizing tensegrity and geodetic construction, a truly efficient and functional design can be reached.
When all of these factors are combined, it results not only on an increase in project feasibility but in a drastic reduction in the logistic tail of the project. Since the lifting gas is from one of the most common substances on Earth, it can be vented or generated as needed. Since the envelope material is not an advanced helium resistant mesh, it need not be as protected. This means such a vehicle would not require complex storage tanks or a large element protecting shed, and it could be collapsed and stowed when not in use. The vessel could be deployed quickly or remain in waiting wherever its mission requires, this allows it to execute a myriad of operations.
Concept of Operation
A system’s capability would vary with its size. Airship systems benefit from the square cube law. Its lifting potential rises with its internal volume, but its weight and surface drag only rise with its external wetted area. As such, a small model may only be suitable for lightweight camera work, while a truly leviathan model could replace aircraft carriers. For discussion, a medium scaled optional manned system is envisioned.
The system would be developed using a fixed utility, variable mission, and open architecture development. This would separate the physical utility of the craft from its mission payload and ensure that both are developed independently, affordably and quickly. The airship portion would be developed to meet a fixed size, lift, speed, range, endurance, and power generation requirement, and its payload could be developed to meet a specific mission within a weight, volume and power available. Since the airship system would be developed from low-cost material, readily available or relatively low technology and from off-the-shelf components, its production time would be comparatively low. It may even be constructed at any available open lot. The payload would be developed by whichever specialist best meets the warfighter’s needs. System improvements could be done incrementally as the vessels return from deployments for depot level maintenance.
Once operational, the system could either be transported to a conflict zone, or can arrive under its own power. Its time to reach destination could not compete with an aircraft system, but unlike an aircraft it could spend days or weeks in the operating zone. Once on site, it could use its payload to operate continuously.
Since low-pressure steam is inert, the airship system is inherently survivable and could be used in non-peer on peer confrontations. With its greater-than-speedboat velocity, and if equipped with an Intelligence, surveillance, and reconnaissance (ISR) and with remote weapon stations, it could be used to deter small-boat attacks.
With its variable altitude and station keeping capability, it could be used as a mobile air and missile defense radar post, and if equipped with a RAM missile launcher, a AN/SEQ-3 laser, or a CWIS system it may be used to defeat a drone swarm attack.
If loaded with an antisubmarine warfare (ASW) suite, it could ensure hundreds of square miles of area are scanned and surveyed for days at a time, mitigating the threat of AIP submarines.
It may also be used to patrol, intercept, and inspect for converted merchant ships with a mobile team of specialist. It also could use a similar load out for other than war operations and could really excel at humanitarian operations.
Lastly, in a true peer-on-peer confrontation, it could be unmanned and used a mobile and expendable tactical airborne early warning aircraft for a nearby battlegroup.
The system proposed would have greater speed than any surface vessel, better endurance than any Navy aircraft, and better affordability than any craft of its size and capability. While it most certainly lacks some of the capacity of air or sea system, it would be able to augment in the Navy ways that neither family of systems could do alone. It can range far from a group, survey vast areas and act as an independent cruiser when the mission requires. In the conflicted and cluttered environment of the 21st-century sea ways, maybe a touched up concept from yesterday is what tomorrow needs.
