"Landing on a barge at sea level is a great demonstration, but landing at 12 miles above sea level will make space flight more like taking a passenger jet."

Spacex Barge
SpaceX CRS-6 mission attempting a landing aboard the "drone barge" on April 16, 2015. Image source: SpaceX.

With that one line, Thoth Technology CEO Caroline Roberts threw down the gauntlet in front of Elon Musk. Arguing that her Canadian company's plan to build a 12-mile-tall "space elevator tower" is more economical than SpaceX's reusable rockets strategy, Roberts has challenged Musk to up SpaceX's game.

That's a bold move. But could Roberts be right? Are space elevators the solution to cheaper satellite launches and economical space exploration?

Elon Musk: The first space-launch disruptor
Currently, it costs America's premier space launch company, United Launch Alliance (ULA -- a joint venture between Boeing (NYSE:BA) and Lockheed Martin (NYSE:LMT)) as much as $400 million to launch a satellite into space. Elon Musk is trying to bring that cost down through a combination of:

  • designing and building rockets in-house
  • testing a new reusable -- and landable and relaunchable -- rocketship
  • landing those rockets aboard remote-controlled "drone barges" at sea.

G
SpaceX drone Barge at sea. Image source: SpaceX.

Musk's drive to reduce the cost of space launches already poses an existential threat to Boeing's and Lockheed Martin's high-cost space launch franchise. But even so, it's apparently not cheap enough for Thoth and its CEO. They want to drive costs down further by permitting "single-stage" rocket launches to orbit. To do this, they want to go the next mile, and build an honest-to-goodness space elevator.

Actually, make that the next 12 miles. That's the height of the space elevator that Thoth has proposed building, and for which Thoth was just granted a patent by the U.S. Patent and Trademark Office (PTO).

I give up. What's a "space elevator"?
Traditionally, a space elevator means a structure in which a cable stretches between a fixed point on Earth and a geosynchronous point in space, and gravity works to hold the whole thing up. Powered cars climb up and down this cable, eliminating the need to use rockets to reach space.

There are a few problems, however, with building a space elevator of this sort: First, materials strong enough to build it haven't yet been invented. Second, to get gravity to hold the whole thing upright, so the space elevator doesn't come crashing down onto Earth, you need the cable between elevator "top" and "bottom" to be roughly 30,000 miles long.

Now obviously, building a space elevator out of 30,000 miles' worth of material that doesn't exist is problematic. So putting construction of an actual space elevator on the shelf for now, Thoth proposes to focus on what is feasible.

Thoth Tower Large Scale
Thoth's proposed space elevator tower, as depicted in a U.S. Patent and Trademark Office patent filing last month. Image source: Thoth Technology.

And that would be?
And that would be a really, really, tall, freestanding tower, containing a very large actual elevator. Rocket ships would be loaded at the bottom, "elevatored" up to the top, and blasted into orbit from a topside launch pad. This would permit using just a single stage to orbit (as opposed to the two or three rocket stages ordinarily needed to get a payload into orbit from Earth launch).

Returning rockets could land on the topside launchpad for refueling and relaunching, sending any payloads they bring back down to Earth by elevator.

Can we build it?
Thoth's patent (No. 9085897) describes its space elevator tower as 12 miles tall -- more than twice the height of Mount Everest, Earth's highest-altitude mountain. The walls of the tower would be constructed from a series of hollow, segmented "cells" made of polyethylene or Kevlar, each "pneumatically pressurized" to maintain rigidity or permit flexibility (to bend with the wind) as conditions require.

Construction of the tower would resemble the unfolding of a collapsible police baton -- where each lower segment of the tower contains a slightly smaller-diameter tower segment within it, and segments roll out in sequence as the tower rises. All the materials needed to build it have been invented, and Thoth has built a small-scale demo already. In theory, at least, this is a kind of "space elevator" we can already build, today.

Police Baton
Thoth's space elevator would expand into space like a collapsible police baton. Image source: Phoenix Outdoor via Amazon.com.

Can they afford it?
Well, almost today. Although the project is already eight years in the making, Thoth still needs a few years to get this thing built. In cooperation with partners, Thoth aims to build a demonstration tower, nearly one mile tall, as its next step. That will require three to five years. Expanding that tower to 12 miles high would take three more years. And the entire project, from start to finish, could cost as much as $10 billion.

Finding a partner willing to pony up that kind of cash could pose a challenge, perhaps an insurmountable one. And there's another problem: Thoth's argument for building a space elevator tower hinges on the fact that much of the energy -- and cost -- of a space launch is expended in the first few miles after launch, as a rocket fights its way out of a deep gravity well, and through dense atmosphere. According to Thoth Chief Technical Officer Dr. Brendan Quine, bypassing the first 10 miles of a launch by launching from the top of Thoth's space elevator tower will save 30% of fuel costs on every launch.

And yet, rocket fuel only costs about $200,000 per launch. A 30% savings therefore works out to about $60,000 per launch. So here's the thing: Amortizing those savings across the $10 billion cost of building Thoth's space tower, it would take approximately 166,667 space launches just to break even.

Now admittedly, if space launches become cheaper, there might be more of them, reducing the distance to breakeven. But at the current rate at which companies and nations send rockets into space (92 launches last year), Thoth's space elevator tower might not break even before the Year 3834 A.D. 

I'm all in favor of "long-term investing." But even for me, that seems like a long wait. You might even say that getting investors interested in Thoth's space elevator tower will be a "tall order."

Thoth Top
Top view of Thoth's proposed space elevator tower, complete with space shuttles on the runway. Image source: Thoth Technology.

Rich Smith does not own shares of, nor is he short, any company named above. You can find him on Motley Fool CAPS, publicly pontificating under the handle TMFDitty, where he's currently ranked No. 260 out of more than 75,000 rated members.

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