One of the major obstacles to a major expansion into space is the current cost of launching payloads into orbit—an easy $10,000 per pound. Techniques and innovations to reduce costs are constantly being sought by space agencies and private interests alike.
One intriguing solution put forth in a recent article in the journal Acta Astronautica, by Brendan Quine, Raj Seth, and George Zhu at York University in Toronto, Canada, features a 9.3 mile high inflatable launch tower. Anchored to a mountaintop, the entire assembly would reach a total of 12.4 miles in height. The proposed tower would also be about 753 feet across and weigh approximately 800,000 tons, about the mass of two supertankers. It would be anchored to the ground by three elevator towers.
The structure would be composed of one hundred or more linked, separately-inflated modules filled with a lifting gas such as helium. For a 15 kilometer high tower, each module would be 150 meters tall and 230 meters across, in turn built from individual tubes 2 meters across made from Kevlar laminates. Each module would require its own active gyroscopes and active stabilization systems, coordinated with all the other modules in its stack.
The tower could cut launch costs by as much as 30% by accelerating a payload along its elevator towers the entire height of the structure. At the height of full launch of 12.4 miles up, it would already be past the vast bulk Earth’s atmosphere and would spend much less fuel fighting against it to get to orbit than a ground-launched rocket. Proponents say it could cut the need for an entire rocket stage altogether for most payloads, reducing three stage rockets to two, for example.
The tower could also be used to bolster wireless communication networks (at the top of the tower, equipment would have an unobstructed view of the ground 350+ miles in every direction), do upper-atmospheric research, and of course serve as a major tourist attraction.
One advantage of the inflatable launch tower over its conceptual cousin, the space elevator, would be that it could be made of much more readily-available materials, and could therefore could be built cheaper and more near-term.
A number of engineering challenges would still have to be addressed before construction could begin, such as how it would be able to handle high winds and inclement weather when cutting up through over nine miles of atmosphere. The weight of icing on such a large structure at high altitudes also cannot be discounted.
Also, whether enough helium could ever be made available for such a huge inflatable structure is also in question, or even if so whether it would be cost effective. Alternative gasses like hydrogen may need to be used instead, which would present additional safety problems.
Brendon Quine, one of the original authors of the article, postulates that the tower could be built up to orbital altitude over time. Others have suggested that the inflatable tower could also serve as the base for a space elevator that could come later.
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