Originally Posted by
rickair7777
4. Lastly, there's some scientific concern that dumping a lot of water vapor into the upper atmosphere would have it's own greenhouse effect... and burning H2 has only one combustion product.
Don’t know that THAT would be a realistic concern. If anything it might increase the albedo a little, reflecting solar energy back up and decreasing global warming. But in any event, it’s difficult to see where a combustion product of water would be worse than a combustion product of water, CO2, oxides of Sulfur, Oxides of Nitrogen, unburned fuel, and soot, which are the products of combustion of Jet A.