Liquid nitrogen is actually very easy to make and very easy to melt. You can buy a generator that can make 67 liters a minute of eBay.

The water would be hot though I’m open for debate on another source to rapidly warm the liquid nitrogen.

I wish I had the time or the money and engineering ability to prove it out. Hopefully some other inventor and build on this concept. It will work, my biggest concern would be destroying the atmosphere, but I would predict we would need a lot of nitrogen exhaust to displace enough oxegen.

Thanks for the feedback!