It does not take “Hopeium” + Unobtainium” All that it takes is Lithium + Sulfur and sulfur is practically a “throw-away” material. The best lithium ion batteries gets somewhere around 260 kWhr to maybe around 300 kWhr and the solid state batteries will get around 400 kWhr but the Lithium + Sulfur batteries will get around 800+ kWhr with current technology. This enough to consider designing short to medium haul regional 100+ passenger aircraft. If we did not people willing to take risks, we would still be riding horses and shoveling you know what. I expect that there will be more than a few failures along the way but nothing risked, nothing gained. See Lyten for more info.