We might not currently have any technology that would make a space elevator viable on Earth. But that doesn’t mean they wouldn’t work on other bodies around the solar system. One of the most interesting places that one could work is around Ceres, the Queen of the Asteroid Belt, and potentially one of the biggest sources of resources for humanity’s expansion into space. A new paper from researchers at the University of Colorado, Colorado Springs and Industrial CNT, a manufacturer of Carbon Nanotube (one potential material for the space elevator), details just how useful such an elevator could be.
One of the most interesting facts about Ceres is that, according to data collected by the Dawn spacecraft, it is made up of around 25% water. Water is useful not only for the fact that it is required for life as we know it, but also because it can be used as a fuel for propulsion systems. Some test satellites use water itself as their sole propulsion whereas others use the components recovered when water is split via hydrolysis - oxygen and hydrogen.
But to get access to this wealth of this particularly valuable material, engineers would first have to get it out of Ceres’ (admittedly tiny) gravity well. That is where a space elevator comes in. A space elevator can serve two purposes - get the materials off of the surface and use leverage to fling them on a trajectory much faster than launching from the surface itself would be. The design discussed in the paper utilizes both of those features.
Fraser discusses what a space elevator is and why it's so useful.It describes a 30,000km long space elevator (SE) that reaches out into the solar system more than 30 times farther than the diameter of Ceres itself. That SE, if made of currently manufacturable carbon nanotubes, can carry payloads of approximately 6,534 kg up to the station at the top of the elevator. From there, they can be flung into space using the space granted by the station which rotates in line with Cere’s rotation of once every nine hours. At that speed, it would decrease the amount of energy needed to get a payload back to Earth by approximately 60%, and a fuel savings of 15%.
Some of that fuel could come from Ceres itself. The paper also details a decision matrix of several water-based propulsion solutions, and found that Microwave Electrothermal Thrusters (METs) provide the most value, with a specific impulse of almost 800 seconds. Another contender was water electrolysis propulsion, which separates water’s constituents and then combines them in a combustion chamber.
To do that chemical splitting, though, the system would need power, and that is one of the major potential obstacles of this infrastructure build. Ceres is in the asteroid belt, and the amount of sunlight that would need to be collected to power this sort of endeavor would be significant. Potential solutions include Sterling engines or radioisotope thermal generators, but plenty of them would be needed to match the scale of the project.
Isaac Arthur dicusses how we could potentially colonize the "Queen of the Asteroid Belt"Credit - Isaac Arthur YouTube Channel
Another potential hiccup would be the communications delay. Since the asteroid belt is past Mars, there’s an average 25 minute communications delay in each direction, making manual control from Earth and its surrounding environs exceedingly tedious. Therefore, any large scale construction project on Ceres, like a space elevator, would require significant improvement in automation before becoming operational.
Those improvements would be useful in other areas, too, and are undoubtedly on the way. Space development experts are giddy about the potential use cases of the resources available somewhere like Ceres. As such it will undoubtedly eventually be mined - and if and when it does, future mission planners will be taking a hard look at this paper and others like it to understand whether or not humanity should tackle one of the biggest engineering challenges it's ever undertaken, and whether it's worth the cost.
L George et al - SE Integration on Ceres: A Technical Framework for Scalable Resource Extraction and Transport
UT - Using A Space Elevator To Get Resources Off the Queen of the Asteroid Belt
UT - A Habitat at Ceres Could be the Gateway to the Outer Solar System
