SkyTrains: A Large Scale Airlift System

L. Van Warren
Warren Design Vision



SkyTrains consist of linked systems of SkyBoxCars. A SkyBoxCar is a helium supported airship of moderate size, utilizing recent advances in materials technology. Each SkyBoxCar is solar and conventionally powered and can fly independently. Arrays of SkyBoxCars fly in formation to form SkyTrains. Characterized as "trains without tracks", SkyTrains can be used to deliver large amounts of cargo to both remote and metropolitan locations. SkyBoxCars are autonomously piloted using the global positioning system (GPS) and weather system data to optimize routing and navigation.

In a meeting, held in Mike deGyurky's office on September 7, 1989 a mega airlift capability was first discussed by the JPL system engineering group in Pasadena. Our group was captivated with the concept of large scale airships traveling at relatively high speed as a method of long haul large scale cargo delivery. This suggested enormous airships, taking advantage of recent material advances, to loft payloads of various kinds.

The motivation was to design a vehicle that could service global disasters such as famines, nuclear catastrophes and the like. There was fulminating concern about the disastrous melt-down at the Chernobyl Nuclear Power Generating facility in the Ukraine. There was a serious interest in proposing functional ways to arrest the spreading of radioactive contamination in the atmosphere in nuclear accidents. Functionally the vehicle would have to reach remote areas to deliver water, food, coverage materials and flame retardents.

Dependability and functionality are increased by using a set of redundant delivery vehicles. An ensemble of airships, linked together so as to minimize drag, increase reliability and simplify delivery logistics seemed an appropriate solution.

On the day that the term SkyTrain was first coined, Steve Nadis, a reporter for OMNI magazine had come to JPL to interview the author for other reasons and had come to see for himself the freeform brainstorming sessions that often manifested themselves in the systems engineering section, a remote downtown Pasadena outpost of JPL. Gathered that September day in were Nadis, deGyurky, the author, Leo Blume, and Brian Beckman.

On that particular September day the notion of the mega-airlift problem was raised and the discussion proceeded with its usual creative abandon. Beckman transcribed the discussion additively in real time via a white board, while Warren articulated the combination of a deGyurky's mega-airlift capability with the concept of a train that would fly. Blume contributed key questions and proposed solutions. Adding to the discussion was what each person brought to the table, Nadis's curiosity about future technology, Blume and Beckman as scientists and visionaries and Warren's preoccupation with flight systems.

JPL was and is not in the business of building airships, but was directly connected to an institution that was; The California Institute of Technology (CalTech). CalTech had been involved in Zeppelin research during the early 1930's. Theodore von Karman, a professor of aerodynamics at CalTech and a person who had participated in airship research in Germany (including the construction of the Zeppelin "Los Angeles" as part of wartime reparations to the US.) had proposed high speed dirigibles in his autobiography . This connection was first noted by deGyurky.

There were a number of design questions that arose and a number of which remained unanswered at the time. Among them, how would the system be powered? Elements of the SkyTrain could be covered with new ultra light weight solar cells to the point of being completely solar powered. A conventionally fueled backup would be necessary for staging operations. The 1994 analysis showed that this would reduce the pure solar SkyTrain cruising speed to around 43 mph, suitable for agricultural point to point applications, scenic cruises, and limited air rescue.

•The 1994 Analysis

1994 analysis developed the concept in a simple minded comparative analysis of three prototypical airships, each autonomously powered and controlled, able to link and unlink to sibling cars at will.

The first SkyBoxCar analyzed was a small technology demonstrator. It was sized so that 50% of its buoyant capacity was used for lifting cargo. As a demonstrator, it would fly at relatively low altitudes and would be unable to take advantage of favorable clines in wind and solar irradiance. It would cruise at 31,000 feet at a speed of 30.7 miles per hour with a cargo capacity of 4000 pounds. It would be 125 feet long and would cost $2.5 million dollars.

The second SkyBoxCar analyzed corresponded to that of a Mack truck. It was sized to carry 45,000 pounds of payload. This increase in scale produced an efficiency increase to 74% compared to the 50% of its smaller sibling. It would cruise at 31,500 feet at a speed of approximately 43.4 mph. At 244 feet long it is four fifths the length of a football field. It would cost approximately $9,485,000.

In the interest of sheer immensity, a third SkyBoxCar was modeled with a cargo capacity 45,000 metric tons. This radical increase in size produces an efficiency increase to 98% compared to the 74% of its smaller sibling. Like its sibling however it would cruise at 33,500 feet at a speed of 43.4 mph. At 2900 feet long, it would be over half a mile in length and would cost a little over 1.3 billion dollars. A SkyBoxCar of this size violates the concept of bite-sized chunks, but is of academic interest because of its lifting efficiency and flight envelope.

In spite of the reduction of cruise speed to 43 mph, the almost completely pollution free operation would seem to make SkyTrains an important capability for the 21st century.