Written Jan 12, 2023.
⚠️ Disclaimer: Contains light spoilers about the books’ universe. Probably do not read if you plan to read « The Dark Forest » soon. Oh and I have no scientific background, this is pure observations of interesting ideas.
I recently finished the book The Dark Forest by Liu Cixin. It’s now one my favorite sci-fi books.
An advanced alien civilization discovers Earth as an alternative to their dying world, prompting them to embark on a centuries-long interstellar voyage to our planet.
The sequel to the Three Body Problem goes on to describe what happens on Earth, including the technological development to anticipate the alien arrival.
I liked the technological concepts proposed by Liu Cixin, as many of them are not too far-fetched in light of our current scientific understanding.
Here are some interesting ones.
Space elevator for low-cost space access
It’s a crazy concept, but it’s being seriously studied.
While it could cost $10+ billion to build, it would reduce the cost of putting things into orbit from ~$7,000 per kg today to as little as ~$50 per kg.
Basically we’d have a satellite in geostationary orbit with a tether inside, like a tape measure. The tether would be extended up into space and down towards the Earth’s equator at the same time, keeping a balance between the two.
On Earth, the station could be made mobile (ship on the ocean) to work around hazards like lightning, wind, hurricanes, space debris, and meteorites.
One challenge is in the strength of the cable – scientists believe that carbon nanotube material could be the answer.
Preliminary work seem to be underway.
| Material | Tensile strength (MPa) | Density (kg/m3) | Specific strength (MPa)/(kg/m3) |
|---|---|---|---|
| Steel | 5,000 | 7,900 | 0.63 |
| Kevlar | 3,600 | 1,440 | 2.5 |
| Carbon nanotube | 130,000 | 1,300 | 100 |
One company in Japan, Obayashi Corporation, reportedly started working on one following a breakthrough with carbon nanotubes (CNTs).
Aneutronic fusion spacecraft propulsion
A spacecraft propulsion system that utilizes aneutronic products of nuclear fusion directly as the exhaust jet would bring us closer to deep space.
From what I gather, this seems to be about the best propulsion method we could achieve with our current theoretical physics framework.
I found this report written at NASA: Aneutronic Fusion Spacecraft Architecture.
Some extracts:
It can be easily argued that the most important factor in drastically changing the paradigm of space exploration is the development of a new, radically more effective in-space propulsion system. Every other technology development would appear merely incremental compared to that of a new propulsion paradigm that, for any given payload, could increase the ratio of mission distance to trip time by a factor of ten or more.
[…] A fusion reactor with net po
