The Option for Low-Speed Airborne Transportation

At this time on year, an airborne freight carrier vehicle powered by renewable energy comes into service and can actually provide a basis to consider low-energy airborne freight transportation for year-round commercial service. Lockheed Martin is developing a large, helium filled 21st century airship that has a variety of potential applications that includes west-to-east freight transportation, using renewable energy.

Introduction

The history of low-speed, low-altitude airborne transportation over short distances dates back to the era of lifting kites. A rope connecting between a large lifting-kite, flying at high elevation could lift substantial load off the ground and move the load over short distances, such as to the other side of a mountain gorge or a river where no bridge existed. Hot air balloons with an onboard small fire and secured to the ground using a tether, could also lift substantial load over comparable short distances. The hot air balloon gave rise to the hydrogen and helium airships.

In recent years, these airborne technologies have undergone new development and advancement. While early kite designs used frames made of bamboo to maintain their aerodynamic profile, some modern kites dispense with the frame and use wind-driven dynamic pressure to maintain that profile. Modern technology allows frame-free operation for balloons and airships that use heated air for buoyancy. 

Aircraft builders such as Boeing and Lockheed Martin have designed and built modern prototype versions of airships that offer future application in heavy lift operation, with potential to greatly reduce the heavy fuel consumption of helicopters.

Heated Air Technology

When a hot air balloon or airship is secured at ground level, modern technology allows for low-cost heating of the air inside the envelope. One option is to use modern heat pump technology to transfer low-grade heat into the envelope, using one unit of electrical energy to transfer up to five units of heat. If the vehicle is located near a thermal power station, heat pumps could transfer massive amounts of exhaust reject heat into the envelope. If the balloon or airship is tethered to a stationary location or a ship, an electric power cable could sustain onboard heat pump operation.

To maintain temperature inside the envelope, a flameless, non-tethered airborne hot air vehicle would use any of several technologies. An onboard electric battery technology could sustain operation of an onboard heat pump. Heat-of-fusion thermal storage technology such as a molten mixture of lithium fluoride and lithium hydroxide could maintain envelope air temperature for between several hours to several days. A micro nuclear reactor using thorium would sustain envelope air temperature for several months. Exhaust and reject heat from combustion thermal engines could also sustain sufficiently high temperature inside the envelope to assure long-distance airborne transportation.

Kite Propulsion

Suppliers to the maritime sector offer frameless kite-sails that assist with pulling large vessels that sail parallel to the trade winds, thereby reducing fuel consumption and carbon emissions. A low-speed airborne vehicle traveling at 5,000 feet elevation and parallel to the high altitude wind known as the Jet Stream could deploy an onboard kite sail restrained with an extended length of tether, to capture propulsive energy from the fast higher altitude wind, when travelling from west to east. In some regions, the southeast and northeast trade winds would allow the kite-pulled airship to travel from east to west.

The absence of water hull drag would allow a wind-pulled airship to travel at much greater speed than a ship on water, with higher elevation kite propulsion allowing an airship to travel over low-lying areas of land, such as south across regions of the Sahara Desert. During the northern summer and north of the Tropic of Cancer, North Atlantic winds blow in a clockwise direction. Propelled by this wind, a kite-pulled airship could sail north from Florida off the American east coast, then across to northwestern Spain and return to Florida along a more southerly route.

Market Niches

The market niches for heavy lift airships include replacing heavy lift helicopters as a means to reduce fuel consumption in applications where the helicopters would be required to carry extreme payload over extended distances. In some regions, a large cruise ship may actually tow an airship carrying a gondola in which special guests who travel at premium rates would gain a more spectacular view of coastal scenery such as encountered along an Alaska cruise, or to be assured of freedom from wave induced pitch and roll of a ship on water.

A kite-pulled airship could provide service carrying tourists in many regions of the world, with either towing by ship or engine power providing propulsion along short segments of the journey. An airship designed to carry shipping containers and using kite propulsion would travel at higher speed than ships at sea, with much lower fuel consumption than air freight. Such a service would occupy a market niche between ship-at-sea and air freight. Using engine driven propellers, an airship traveling with wind direction could likely achieve three to four times the speed of a ship, to offer faster delivery at competitive rates.

Remote Service Applications

Lockheed Martin Corp is believed to have secured an order from an oil and gas exploration company that is interested in leasing the unique design of LMH-1 helium airship with 20-ton carrying capability, in an Arctic region that is without roads. There is interest in France to use airship technology in the forestry sector, to carry logs from a region that has access difficulties. The same technology would have transportation application in mountainous regions of Western Canada, United States as well as the Andes Mountains of South America and across Mongolia.

Conclusions

The new generation of 21st century airships has a variety of applications. It is presently unknown as to the ultimate maximum physical size to which the technology will be developed. There is potential along several routes to combine airship technology with kite-sail propulsion, to provide long-distance travel using minimal fuel. While there is potential to use heated air to maintain airship buoyancy, further research will determine the long-term practicality of such a concept.