Refuelling and the Environment

[tancred]

A couple of weeks ago, the players in my TravellerHero game hit me with a good question. I had to simply answer that I really didn't know, but thought it wouldn't be a problem.
But now I'm wondering, so here's the question:

The players have decided to make their base in a system with no gas giants and a main world with size 4 (6,400 km diameter roughly) and a hydrographic percentage of 3.

Without a gas giant in the system, the main world is the only source of fuel (other than ice asteroids, comets, or the Oort Cloud. I haven't found any guidance on any of those as to how much fuel they might or might not provide).

Given that situation, how many tons of fuel can that small a world sell before the loss of water in the (rather dry) hydrosphere begins to affect the environment?

 

[Piper]

My guess would be lots.

Even using insanely conservative guesses at average depth, you're still looking at hundreds of millions of tons of water. Assuming that losing 1% of that would begin to effect the environment, you'd still have a large fuel source.

That being said, it's still a finite resource so ice asteroids/comets etc. would make an attractive alternative.

 

[Vladika]

My guess would be lots.

Even using insanely conservative guesses at average depth, you're still looking at hundreds of millions of tons of water. Assuming that losing 1% of that would begin to effect the environment, you'd still have a large fuel source.

That being said, it's still a finite resource so ice asteroids/comets etc. would make an attractive alternative.

Plenty of Ice out there!

http://www.space.com/1526-largest-asteroid-fresh-water-earth.html

 

[esampson]

Some quick 'back of the envelope' calculations. A planet with a diameter of 6,400 km would have approximately 1.3 x 10⁸ km² of surface. If 3% of that is water that would be about 4 x 10⁶ km² of water. Given how little water there is I'm guessing those bodies of water probably wouldn't be very deep, but just to simplify things lets assume an average depth of only 1m for the moment. That gives us 4 x 10¹² m³ of water, or 5 x 10¹³ metric tons of water. This works out to about 6 x 10¹² tons of hydrogen.

So the real issues become how deep is the water and how much can the planet loose? We can multiply our 6 x 10¹² by the average depth in meters, since we assumed an average depth of 1m in the beginning, and then take whatever fraction we think is 'safe'. If we assume an average depth of 3m and a 'safety limit' of 1% that gives us 200,000,000,000 tons of hydrogen. Probably way more than your players will ever come close to using. The planet could probably even do a fairly brisk spaceport trade. Assuming a dozen 10k dton ships a week that fuel up for Jump-2 that's 24,000 tons of fuel a week or enough fuel for about 160,000 years.

 

[esampson]

Incidentally, while I'm not an ecologist, I'm pretty sure that using 1% of the planet's available water would have a fairly negligible impact on its climate. While I do not want to sound like I am downplaying the significance of climate change I did a quick Google search and found that since the mid 20th century it looks like the change of CO₂ in the atmosphere is around 30% and while that is quite probably having an effect (please note, this isn't an invitation to start up a political discussion concerning climate change) I would speculate that the rate of change appears to be slow enough that we can assume a change in the amount of water on a planet that is an order of magnitude lower (and almost certainly spread over thousands of years) probably would not produce very pronounced effects.

 

[shaunhilburn]

Given that situation, how many tons of fuel can that small a world sell before the loss of water in the (rather dry) hydrosphere begins to affect the environment?

Let's do the math.


4,000 mi diameter = 2,000 mi radius = 3,218,688 m radius

4*pi*3218688^2 = 1.30187E+14 sq meters surface area

30% coverage = 3.90561E+13 sq meters ocean surface

Uniform depth 200 meters (shallow oceans) = 7.81122E+15 cubic meters (tons) of seawater
So, the total seawater inventory is thousands of trillions of metric tons.

Separating H2 from O gives 11% hydrogen fuel by mass = 8.59234E+14 tons of fuel total.

The answer is: several trillions of refuellings (200 tons each) to deplete all the water, and several tens of billions of refuelings to produce noticeable impact (enrichment of the atmospheric oxygen as the hydrogen is taken away from the seas).

 

[esampson]

Oh. It's a Hydrographics of 3 and not 3% of the planet? Yeah, that takes my numbers (which already said you had way more than enough fuel) and blasts them out the window. You've got to increase all figures by at last one order of magnitude and probably more (since the bodies of water will be significantly deeper).

 

[MCEvans]

Clarification

To OP

UPP hydro 3 (30-39%) or 3% (UPP hydro 0 (0-9%))?

Given the previous posters and the type of ships that PC run around in either way not a factor.
If the question has to do with other factors; starport, population astrographic location or campaign plot line. Please let us know :devil:

 

[Timerover51]

A couple of weeks ago, the players in my TravellerHero game hit me with a good question. I had to simply answer that I really didn't know, but thought it wouldn't be a problem.
But now I'm wondering, so here's the question:

The players have decided to make their base in a system with no gas giants and a main world with size 4 (6,400 km diameter roughly) and a hydrographic percentage of 3.

Without a gas giant in the system, the main world is the only source of fuel (other than ice asteroids, comets, or the Oort Cloud. I haven't found any guidance on any of those as to how much fuel they might or might not provide).

Given that situation, how many tons of fuel can that small a world sell before the loss of water in the (rather dry) hydrosphere begins to affect the environment?

I have a similar system involved in a novel that I am working on, where the planet has an "A" class starport, size 5, atmosphere of 9 (dense, tainted: planet is cool for the dense atmosphere with a taint of dust, mask only), and hydrographic factor of 38% (large ice caps), with no gas giant. The cost of fuel there is higher than normal, as while it would take a while to really affect the hydrographic percentage, for political reasons, loss of water for space ships is a problem. Food for space ships is taxed for water loss, unless the ship delivers an equal quantity of water upon landing.

A couple of members of the Roving Jester are bringing in filtered water from another planet they have exclusive rights to trade with, and selling it to the starport restaurants as high-grade bottled water. Their profit is One Imperial credit per 5 liters, and they normally bring in between 1 and 2 cubit meters or 1000 to 2000 liters a trip.

 

[tancred]

The UPP number is 3, so total water is 30% to 39% of the planet's surface.

This confirms my original suspicion, that even though the value SOUNDS like there's not that much water, in reality refueling is not going to impact the environment in any reasonable amount of time.

Thanks to all for the comments.

Edit: McEvans, the original question came up because my players have adopted Talos / District 268 / Spinward Marches as their home base (for plot/story/sentimental reasons that have nothing to do with the suitability of the planet).

T5 Second Survey data increased the size of the planet to 4, but the hydrographic UPP rating has always been 3 as far as I can tell.
The planet has a population of around 800,000, so I don't see that being enough to deplete that much water quickly.

But, the players have invested a ton of money and effort to upgrade the starport from class E to class C, and the fact that a C does provide fuel prompted the original question.

(Although I could see the population becoming a factor down the road, if the players keep working to upgrade the planet and bring in a LOT more population).

On the other hand, this thread tells me there's a LONG way to go before the planet runs out of water.
And since I worked the entire system up through Book 6, there are a number of ice-capped worlds and moons in the system that could be tapped too.
Not to mention potential strikes in the planetoid belt.