> Spherical/cylindrical tankage is needed only to contain high pressure, but we don't need to contain pressure. You want the minimum surface area to volume, to

> Spherical/cylindrical tankage is needed only to contain high pressure, but we don't need to contain pressure. You want the minimum surface area to volume, to minimize heat losses (and minimize the surface area that has to be insulated when weight matters such as in an aircraft). Spherical being the optimum, but obviously unpractical. If you look at tanks in current aircraft, typically in wings, they have huge surface area vs volume. Lifting body might be better, I'm not sure. > Not so easy to know the net effect Luckily we have researchers who have dedicated years, if not decades, to studying this exact problem. Still, not an easy problem, surely. Some quick searching turns up this overview: https://www.carbonbrief.org/explainer-challenge-tackling-aviations-non-co2-emissions https://www.carbonbrief.org/explainer-challenge-tackling-avi... (and it seems I was wrong, it's not water vapor that is the major factor)