ARCA have demonstrated their concept of a clean, reusable booster powered by electricity and water instead of all those dangerous rocket propellants. Sounds to good to be true right?

ARCA are largely based in Romania, but also developed aerospike propulsion test hardware in the US for a time.
http://www.arcaspace.com

All the ARCA footage comes from their Youtube Channel which shows their ongoing work with various projects.
   / arcachannel  

Water Tank rocket footage is from Mythbusters:
https://www.discovery.com