Hydrogen surfing

[vegascat]

What would be the hull pressure on a ship that is deep enough in a Gas Giants hydrogen atmosphere to reach neutral bouancy like a zepplin?
What depth in water would that equate to?
What state would the hydrogen be in, gas, liquid or solid?
What kind of armor factor would be needeed to resist the pressure?

I am thinking that the pressure might be survivable to a armored SDB at a depth where the boat could float on the boundary where the hydrogen compacts into liquid. This would allow the SDB to remain powered down waiting for a victim to come by.

 

[Hecateus]

um...no

and anyway, any sane space traveller looking to refuel from Gas Giants would use robotic DroneCraft to do the job...IMTU

 

[Richard Saunders]

Hello.
This will be poorly put but.
Work out the volumn of the ship (this will change depending on the shape) then divide the volumn by the all up weight of the ship this will tell you what each Cubic Foot,Meter or inch (this will depend on what measurments your using) weighs, this tells you how much liquid or gas you have to displace to float.

If the ship is 100cubic meters in volumn and weights 100tons, EACH cubic meter weights 1ton, so you need to sink until you displace 1ton for every meter space (this would depend on gravity and temperature).

What you realy want is a submarine with maneuver drives.
Remember armor will add to the overall weight, and SDB's dont last long in battles (if they carry serious weapons (spinal mount or bays) they are probably to big to be called a boat and should be called a ship).
Sorry not a lot of help, i dont know the weight of a cubic meter of hydrogen at 250deg absol under 5g press. Yes i know pressure isnt messured in g's but you know what i mean.
BYE.

 

[Richard Saunders]

Originally posted by Hecateus:
um...no

and anyway, any sane space traveller looking to refuel from Gas Giants would use robotic DroneCraft to do the job...IMTU

Hello.
And dont drones make nice targets.
What do you use for refueling after the drone is destroyed.
Bye.

 

[EvilDrGanymede]

Originally posted by Lionel Deffries:
And dont drones make nice targets.
What do you use for refueling after the drone is destroyed.
[/QB]

A) Your actual ship would probably make an even nicer target.

B) If your drone is destroyed, you're just inconvenienced. If your ship is destroyed, you're screwed

Maybe drones are easy targets, maybe they're not (I doubt they're any easier to target than a ship) - but either way, you're not risking yourself in a dangerous maneuver by using drones.

 

[Drakon]

I think vegasct has a good idea. But the others are not wrong. If they can spot you, you are in trouble. But if they don't and they are low on fuel, and you can "surface" and shoot first....

One of the problems is weather on your gas giant. Unlike a submarine, there is no clear water/atmosphere interface. And storms on a Jovian can go rather deep, which will screw up your attitude/altitude, as well as make your crew sea sick.

In some versions of Traveller (GURPS and I think FFS) you compute the mass of the ship along with the volumn. You know your density right there. All you need to figure out is the density of gas in your giant, as it relates to pressure (which will be a function of mass(gravity) of the planet.

 

[Hecateus]

On Jupiter, there are lightning bolts with the thickness of Ireland. The Radiation belts around it are extremely nasty. It is also very warm in it's atmosphere, staying cool will be a problem. Corrosive gas clouds like those found on Venus may eat away at your ship. Or perhaps some giant gas cloud monster will try to mate with your ship.

Use the drones.

 

[TKalbfus]

In traveller, the starships are assumed to have an average density of liquid hydrogen. When the ship descends to a point where the density of the atmosphere is denser than liquid hydrogen, then it will float. Actually the gas giant probably has an ocean of liquid hydrogen that you can set the ship down in. You would then just open your valves and fillup your hydrogen tanks. I doubt most refueling at gas giants would be done this way.

 

[salamander]

Originally posted by Tom Kalbfus:
In traveller, the starships are assumed to have an average density of liquid hydrogen.

Where do you get that from?

 

[EvilDrGanymede]

Originally posted by salamander:
</font><blockquote>quote:</font><hr />Originally posted by Tom Kalbfus:
In traveller, the starships are assumed to have an average density of liquid hydrogen.

Where do you get that from? </font>[/QUOTE]They don't - their volume is measured in units of dtons of liquid hydrogen, is all.

Besides, it's rather hard to be buoyant in an atmosphere made of the lightest element. The only way to stay aloft in the upper atmosphere would be to use balloons of heated (and therefore less dense) hydrogen, and even then the actual lift that you'd get would be rather low, since the density contrast isn't that great.

You'd have to go very deep in the atmosphere for a spacecraft with a metal hull to be neutrally buoyant, if it would ever reach that stage at all.

 

[TKalbfus]

They don't - their volume is measured in units of dtons of liquid hydrogen, is all.

From the starship construction system. Manuever drives are rated for acceleration in pushing a given volume of hull at a ceratin acceleration. The assumption implied is that a 100 dton hull weighs 100 metric tons as the starship with all its empty spaces plus its hydrogen tanks averages the same density as liquid hydrogen. This is an approximation. Each tank of liquid hydrogen weighs in metric tons its displacement in liquid hydrogen. A starship without a jump drive would have to be mostly fuel tanks if it is to reach a useful fraction of the speed of light, so this approximation is not far off in a realistic starship.

Besides, it's rather hard to be buoyant in an atmosphere made of the lightest element. The only way to stay aloft in the upper atmosphere would be to use balloons of heated (and therefore less dense) hydrogen, and even then the actual lift that you'd get would be rather low, since the density contrast isn't that great.

I agree. I was being a little silly. I have no realistic expectation that a starship won't be crushed before the atmosphere becomes dense enough to float it. Though having a large force field that excludes all gases would make the ship less dense that gaseous hydrogen if it's volume was great enough.

You'd have to go very deep in the atmosphere for a spacecraft with a metal hull to be neutrally buoyant, if it would ever reach that stage at all.

 

[vegascat]

Does anyone have an idea of what the pressure would be for a ship 1000 DTon, 13500 M3 vol, Mass, 1000 Tons mass, sitting at a depth where it would float in hydrogen?

 

[Richard Saunders]

Hello.
Sorry my missunderstanding i thought the original question had a SDB in it and not many SDB's in my universe shoot at inocent freighters, so i assummed (silly me) that it was assumed that the ship was an enemy.
If you shoot the drone down they have to enter the gas giant to refuel knowing there is a hostile ship there or go somewhere else, if the drone is the only refueling they can do then they are in big trouble, again im assuming warship.
What would be worse knowing theres one in there or thinking there could be more (why only one).
With a bit of stealth tech anything in a gas giants atmosphere would be very hard to detect because of the electromagnetic radiation, Gravametric wouldn't work that close to a gas giant and MAD (magnetic anomaly detectors) could be defeated by running a trickle charge through a degausing coil (just like the ships in the 2nd world war) cant figure out why submarines dont do this now.
Bye.

 

[far-trader]

I came across an old draft of a work in progress for a vehicle design system. Modified from FF&S (presumably v1) to adapt to T4 and incorporating elements of T4 SSDS. I can only imagine from the printout that it was from the TML but can't be sure. There is no author or date printed on it. It's about 20 pages in small print and incomplete though close to done with a couple examples.

Anyway it has any closed hull allowing safe use in vacuum or to a depth of 10m (at standard pressure I imagine). Each multiple of 10 atmospheres of depth (equals 100m depth according to the rules) requires 3 points of armor (i.e. armor 0 is good for 10m depth at standard earth atmospheres, armor 3 for 100m, armor 6 for 1,000m, armor 9 for 10,000m). The cost of armor (hull) for pressure is 10 times base cost for pressure seals, thick ports, propulsion seals, sensors, etc. The armor tables themselves look a lot like the T4 vehicle design tables iirc (my book is not here).

That is all for now, more later as I find data or the time to type in the tables for the armor if that would help anybody. Below is a short sample so maybe someone can compare it to FF&S2 or T4 vehicle design and see if it matches.

TL6 Fiber Laminate

toughness of 1cm = 1
mass per square meter = 0.01t
price per cubic meter = Mcr0.003
minimum thickness/mass per square meter = 0.7cm/0.007t

Every time you halve or double the thickness the armor rating is changed by -/+ 2

eg.

0.7cm is armor -1
1.0cm is armor 0
4.0cm is armor +4

eg.

A vehicle with 10 square meters of hull and 0.7cm of Fiber Laminate has armor 0 (10m2 x 0.01t x 0.7cm = 0.07t of armor with a volume of 0.07 cubic meters. Multiply by 5 for each 1G acceleration rated for the vehicle.

 

[kaladorn]

Dan,

Did you make a boo boo?

0.7 cm of armour is 1,
1.0 is ??? zero ????,
and 4.0 is another positive number?

Unless this is some form of 'alternating sequence', I think something is fishy here.

 

[far-trader]

Originally posted by kaladorn:
Dan,

Did you make a boo boo?

0.7 cm of armour is 1,
1.0 is ??? zero ????,
and 4.0 is another positive number?

Unless this is some form of 'alternating sequence', I think something is fishy here.

D'oh, er I mean, hey you squirrely little minus sign get back up where you belong, git, shoo



There, that should be better now, gotta watch those lazy good for nothing operands, always sneaking off to play when you turn your back on them.

 

[Drakon]

1 dton = 1 metric ton of liquid hydrogen or 13.5 m^3. At standard temperature and pressure, air has a mass of 1.19 grams per Liter. So, 1 dton of air at STP =13,500 Liters or 16.065 kilograms. Far less than the 1000 kilograms of liquid hydrogen.

So floating on a jovian may not be that hard after all. The density of air is less than that of liquid hydrogen anyway. Add components, drives and the such, and figure out how to avoid and/or survive the storms and the lightning the size of Ireland, (assuming survival is even possible), it might work. And also there is a layer of metallic hydrogen to worry about, which as I understand it, is pretty solid, or icy, and highly conductive electrically.

One other problem is that Jupiter's gravity is about 2.53 times that of earth (at the 1 bar level) Will a 2 G manuvering drive be able to get out?

 

[Hecateus]

Ship Travellers should ba able to find some reasonable measure of boyancy in a gas giants' outer layers. But the Metallic Hydrogen 'mantle/core' is so far deep into the beast, that it is not a practical place to hide.

I always assume that the G1-6 ratings are just the optimal cruise level. A lead foot pilot could push 2-3 times that if they are willing to burn xtra fuel, deal with the heat, and risk wearing-out/destroying the drives. [edit:} besides, it is the AntiGrav, not maneuver drives, which are important in a gas giant.

But gravity deck plating must be used to prevent broken bones...this would I think be a problem for those hiding. A good sensortech could pick up the resulting neutrino, gravitic, and magnetic anomolies.

 

[Drakon]

The metallic hydrogen core, if I am not mistaken, is pretty solid. So hiding is not a problem. Crashing into it is however. Losing bouyancy, breaching the hull, that could be bad. Its also hot too and the pressure is not good for continuing physical existence.

I can't imagine it would be fun, but if you can pull it off, it would be a great ambush.

Broken bones, not sure that is going to be much of a problem with only not quite 3 times the gravity. You'll feel sluggish, and might want to pad things a bit more, but even if the grav decking fails, you should be pretty okay.

 

[EvilDrGanymede]

Originally posted by Drakon:
[QB] The metallic hydrogen core, if I am not mistaken, is pretty solid. So hiding is not a problem. Crashing into it is however. Losing bouyancy, breaching the hull, that could be bad. Its also hot too and the pressure is not good for continuing physical existence.

I can't imagine it would be fun, but if you can pull it off, it would be a great ambush.

Don't. Even. Think. About. It. .

The core (if it exists as a separate entity) is most likely rocky, about 10 times the mass of the earth, under a few million atmospheres pressure and temperatures of a few tens of thousands of kelvin). The metallic hydrogen layer above it is well, not much less pressurised and not much cooler.

A TL15 ship could probably go quite deep, since it's hydrogen we're talking about here, so the pressure gradient is pretty gradual despite the higher gravity... but it'll probably be destroyed by crosswinds and weather conditions and rising temperatures before it gets too far in.