Thoth Technology’s patented space elevator design sparks global interest
By Treena HeinFluid Power General Materials Aerospace
Sky high ThothX Tower design side-steps typical structural challenges of ultra tall structures.
Once an idea has come, engineering is everything. It’s the bridge between ideas and reality, and in the ambitious case of Thoth Technology, it’s a bridge to the stars. More specifically, it’s a space elevator, a transportation system tethered to the ground at one end and rising into, or at least close to, low earth orbit at the other. As an alternative to expensive rocket launches, such a structure would usher in a new era of relatively cheap space exploration.
The original idea for a space elevator belongs to Russian Konstantin Tsiolkovsky, who thought of it back in 1895. The concept was revisited by another Russian named Yuri Artsutanov (who investigated potential materials) and American Jerome Pearson (who did calculations on tensile strength) in the 1960’s.
About 15 years ago, physicist Bradley Edwards looked at the feasibility of using carbon nanotubes to support such a slender and long structure. But it turns out that even the nanotubes available today don’t provide sufficient tensile strength and low enough density for a taught cable that could both support itself and the payloads that would be travelling up it.
Enter Thoth Technology. On a regular day, the Pembroke, Ontario aerospace and defense OEM develops miniaturized payloads for space and UAV platforms. However, the firm took the space elevator world by storm this past summer when it was granted a U.S. patent for its space elevator concept, the ThothX Tower.
Unlike previous ideas, Thoth’s design sidesteps ‘the cable problem.’ Instead, picture a series of washers stacked onto the shaft of a bolt. The 20-km shaft/core is hollow, and the washers are ‘cells’ 300 meters in diameter, made of polyethylene and Kevlar and filled with helium or hydrogen. The tower would be built one cell at a time, and the structure would stand upright as it grows – and withstand external forces such as wind currents – through control of the pressure in various cells. In addition, heavy gyroscopic flywheels at the base would be used to increase the angular momentum of the elevator’s core structure.
“It’s an actively-guided tower with a harmonics control strategy,” says Thoth President and CEO Caroline Roberts. “Software will differentially adjust the pneumatics and actively guide the centre of gravity to face light winds, or even a hurricane.”
Most of the 300 cells would be pressurized to 100 atmospheres, and those undergoing repair would be depressurized. The modular nature of the cells also means that if one cell gets damaged and loses pressure (through a micro-meteor hit for example), the tower wouldn’t suffer a catastrophic collapse.
“The seam in each cell will be closed using well-known technologies used in rockets and sailing vessels,” explains Brendan Quine, Thoth’s co-founder, CTO and the elevator’s inventor. “A weave is applied over the two surfaces of the seam like a blanket, and then that will be heat-cured to bind it, similar to how a fibreglass yacht is manufactured.”
While fantastical sounding and certainly ambitious, the ThothX Tower’s creators say their concept has sparked global interest and tempered enthusiasm in the scientific community.
“The Thoth concept is innovative,” says Ishwar Puri, dean of engineering at McMaster University in Hamilton, Ontario. “By employing an inflatable tower within which the elevator climbs, the design overcomes the material constraints placed by the more conventional approach that tethers a cable to an orbiting satellite, from where it is suspended towards Earth’s surface with a counterweight.”
Still, Thoth’s patent filing has also sparked many questions, chief among them how the space elevator will ferry sizable payloads 20 km up in air without using conventional mechanical means. According to Quine, the tower’s elevator will be powered through electrical charge and frictional contact.
“Tracks or cable are too heavy, but electricity is very efficient,” explains the York University engineering professor. “The elevator cars will attach to the tower through electrical attraction and be guided along a corkscrew path using a frictional wheel which will grip the tower.” With each pass of a car downward, the tower will be re-charged, he adds, and possible energy transfer may also occur between two cars passing each other.
Once operational, the ThothX Tower would be able to lift up to 10 tonnes of parts for space plane and rocket construction. Spacecraft would then launch from its platform in a single stage and return to the top of the tower for refueling. This allows for great energy savings over conventional rocketry blasting off from the Earth’s surface. The tower would also be a hot tourism destination, Roberts says, with tickets to the top expected to be offered for about $1,000 CAD.
But Thoth’s design is not just about accessing space for missions or for fun. In addition to being an optimal platform for wind turbines and communications equipment, flying from one ThothX Tower to another at Mach 4 or 5 would cut travel time around the world by half. “Japan and Australia are among those very interested in this application,” says Roberts. “Even with an hour up, your flight, and an hour down, it will be a much shorter and more exiting trip.”
Currently, the company is planning to build a proof-of-concept demonstration tower approximately 1.5 km tall, which Quine predicts will cost US$1 billion and take three to five years. Thoth hopes for the first 20 km tower to be finished for a cost between US$5 and $10 billion in another three to five years after that.
Puri believes that, despite all the questions that he and others have, “the of out-of-the-box thinking that the Thoth design uses is a brilliant example of the engineering creativity that is required to move science fiction into the realm of everyday reality.”