UFO's

[Anomalocaris]

Uh, >>90% of the water in our solar system is not on earth.   If our understanding of the process of planetary formation is correct, then most planetary systems would contain many times more water than present on earth, many of these would have them concentrated on large outer planets and moons.

Apologies for being unclear, what I was stating in a rather vague roundabout way is, why does a starship need water?

Water may indeed be a valuable resource for an interstellar spaceship, growing petunias or whatever but as a reaction mass for a propulsion system then that is one piss poor starship drive they have.

Edit:

Other than water what does planet Earth have that they can't find in the millions of planets much closer to their home world?

Yes I see your point. My bad.

Water as reaction mass for a propulsion system may not seem nearly science fictiony enough for an future age we are told that would be populated by warp factors and Alcubierri drives,  but there seems to be no reason why such reaction propulsion systems can not form the basis of interstellar civilization.

Right conceited yokels we would seem if several hundred years in the future, we are still stuck on this planet pining away for faster than light technology, and scrappy adventurous aliens in chemical rockets a century or two behind our own technology curve come down and demand to see our leaders.

[Gawdzilla Sama]

And we can't be that interesting to a space-faring race. Maybe for battle royals, perhaps.

[Succubus]

[Anomalocaris]

And we can't be that interesting to a space-faring race. Maybe for battle royals, perhaps.

Who knows, may be we are interesting, and unbeknownst to us, we already live inside a terrarium for giant trans dimensional aliens,  and only yesterday a holographic sign invisible from the inside was posted on the outside of the terrarium saying “don’t tap on the force field!”

[Gawdzilla Sama]

And we can't be that interesting to a space-faring race. Maybe for battle royals, perhaps.

Who knows, may be we are interesting, and unbeknownst to us, we already live inside a terrarium for giant trans dimensional aliens,  and only yesterday a holographic sign invisible from the inside was posted on the outside of the terrarium saying “don’t tap on the force field!”

"The True Man Show".

[Anomalocaris]

[Succubus]

[Anomalocaris]

There is no real difference between using water as reaction mass or using some gas like helium as reaction mass.   You can build very efficient ion propulsion by vaporizing, dissociating water, and ionizing the oxygen and hydrogen and use them as reaction mass using electric propulsion...

I see no net gain in chucking ionised water (for want of a better term) out the engine nozzle as opposed to chucking out superheated steam.

You can only add so much energy to steam before they stop being steam and become ions anyway.   Also, it’s much more efficient to use a magnetic field to chuck stuff out at high energy and speed than to try to do it using heat.  To do so the stuff being chucked out needs to be charged.

[Succubus]

<Much snipped for focus> What happens if the first alien who comes to us are technologically more backwards and poorer then we are...

How would they get here?

[Anomalocaris]

<Much snipped for focus> What happens if the first alien who comes to us are technologically more backwards and poorer then we are...

How would they get here?

Solar sails?  Chemical rockets?   This is several centuries in the future,  they can have stuff we can’t imagine today, and still be a technological behind where we would be then.   The Chinese had far better ships and technology overall in the 1400s, but it was the Europeans who made much better use of inferior ships and discovered America, and reached China, instead of the other way round.w

Maybe they are more advanced than we are in one area, but we are more advanced in several others.   So the Europeans had better ships and better astronomy than the Indians in the early 1700s, but the Indians were still competitive or superior in many areas of farming and metallurgy, and arguably some aspects of military technology as well.    Yet queen victoria became the empress of India, while no india prince ever became emperor of British isles.