Spacechains are fully decentralized blockchains that are tied to Bitcoin and serve solely to expand the Bitcoin ecosystem, without creating yet another competing altcoin, thanks to Blind Merged Mining and the Perpetual One-Way Peg. It can be thought of as a way to create opt-in block space for any use case that doesn't directly require the BTC asset, such as colored coins, decentralized DNS, DAOs, DeFi, DEXes, etc.

Slides: http://tiny.cc/spacechains

Blind Merged Mining: https://gist.github.com/RubenSomsen/5e4be6d18e5fa526b17d8b34906b16a5

The Perpetual One-Way Peg: https://medium.com/@RubenSomsen/21-million-bitcoins-to-rule-all-sidechains-the-perpetual-one-way-peg-96cb2f8ac302

(From Youtube)