Starship crush depth;
- Thread starter Blue Ghost
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Drakon
SOC-14 1K
Antenna, pitot tubes and sensors will all have to be hardened against, well lets call it "Sea Pressure" (as opposed to "Air Pressure" for atmospheric flight in less than a few bars of pressure) The connections will be weak links and the limiting factor for your hull's pressure limit.
It seems to me that you can use induction mechanisms to power and retrieve data from electronic sensors outside the main hull. Pitot tubes are really pressure inlets to instruments inside the airframe. So there is an engineering challenge in hardening that piece of gear.
As for tubes and barrels, just because a ship can survive to 3,000 atmospheres, deeper in a gas giant than almost any other kind of ship, does not necessarily mean they can use their missile tubes.
BraselC5048
SOC-8
Personally using my design data IMTU, and the structural strengths of the hull I calculated a while ago, I got a crush depth in water in 1 G of 20 meters.
The ship is 18 meters tall.
Moral of the story - IMTU, don't put your starship underwater.
PS - water pressure goes up fast with depth.
The ship is 18 meters tall.
Moral of the story - IMTU, don't put your starship underwater.
PS - water pressure goes up fast with depth.
Pressure Damage
Example: A typical TL10 Beowulf has pressure protection = 100. Boring details here in the code block:
Every 10 meters of depth is 1D hits per minute against armor (or persons).
If Armor is penetrated, hull is no longer sealed, and our ship starts leaking. Not necessarily the same as crush depth, but compromised hulls are still bad.
According to T5, p.293 and p.336.
Thus,
100 meters depth = 10D hits. The Beowulf is safe.
300 meters depth = 30D hits. If this Beowulf has the "Submersible" option, then it's safe, otherwise it will be leaking badly.
1000 meters depth = 100D hits. The Beowulf will take damage to multiple locations every minute -- a very bad situation, perhaps comparable to a 'crush' event.
Example: A typical TL10 Beowulf has pressure protection = 100. Boring details here in the code block:
Code:
TL = 10
Hull Structure = plate, so AV (Armor Value) = TL = 10
(nb: this Beowulf lacks actual armor, so final AV is 10).
Since structure is non-organic, pressure protection = AV x 10 = 100.
(nb: If hull also had the "submersible" option,
pressure protection would be doubled again).Every 10 meters of depth is 1D hits per minute against armor (or persons).
If Armor is penetrated, hull is no longer sealed, and our ship starts leaking. Not necessarily the same as crush depth, but compromised hulls are still bad.
According to T5, p.293 and p.336.
Thus,
100 meters depth = 10D hits. The Beowulf is safe.
300 meters depth = 30D hits. If this Beowulf has the "Submersible" option, then it's safe, otherwise it will be leaking badly.
1000 meters depth = 100D hits. The Beowulf will take damage to multiple locations every minute -- a very bad situation, perhaps comparable to a 'crush' event.
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Thanks for that, robject. I'll probably get my copy this coming week.
Your starships are made of tissue paper then. TL 7 thin steel hulled subs go at least 500 meters... If 20 meters is all it can stand, don't let anyone lean too hard on it while its parked on the tarmac.
Yes, I have a piece of that foil in storage plus a printed circuit board made with gold wire. (neither flew aboard a mission)
Well, the thing that gets me is that traditional air frames are designed to hold pressure in against thin atmosphere outside. Ergo you'll note that when you board a plane the lip of the door is on the inside so that the inner pressure presses against the door to help form the seal against the outside. If you look at a submarine the lip of the door is on the outside so that the pressure of the seawater presses against the door to help form the seal.
I'm kind of curious how a Traveller starship manages pressure in both directions.
I'm kind of curious how a Traveller starship manages pressure in both directions.
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Simple. As a sub does. Why? Because it only has to deal with an overage difference from the inside of ~ 1 Atm. It might have to deal with higher than 1 Atm on the outside.
But it spends most of its time in a vacuum. Air would be prone to leaking through a seal that isn't pressed against a hull, or so I would think.
I'm sure there's a simple engineering solution, but I wonder what it is.
I'm sure there's a simple engineering solution, but I wonder what it is.
Who said it wouldn't be against the hull? We are only talking about 1 atmos. pressure difference. I can handle that with a screw on mayonnaise jar lid.
Who said it wouldn't be against the hull? We are only talking about 1 atmos. pressure difference. I can handle that with a screw on mayonnaise jar lid.
Your average soda bottle holds 3 atm in with compression fitting alone. (they're good to betwee 0.5 and 1.5 atm vs crush, due to lack of frame.)
3 atm? Wow, didn't know that.
Who said it wouldn't be against the hull? We are only talking about 1 atmos. pressure difference. I can handle that with a screw on mayonnaise jar lid.
But you're missing the principle behind how doors are designed for aircraft verse how hatches are designed for submarines. For subs you have stuff pressing in on the shell of the vessel. For aircraft you have stuff pressing outwards on the hull. It's the pressure that helps for the seal for the two craft, but the pressure vector is reversed.
I guess that's why Marc Miller came up with the iris valve scheme of things. But I also seem to recall that the exterior hatches were akin to the doors on the in the interior of a naval vessel ... my memory's a little hazy.
You don't get it. See soda bottle example below. Trust us, mechanically it is NOT a problem.
What example is that?
The way a coke bottle works is that the cap is squeezed evenly around the glass lip of the bottle's opening. That doesn't strike me as being the engineering behind starship airlocks.
Commercial Airplanes maintain internal pressurization...
Some rough numbers
0' AGL 14.7PSI
10,000' AGL 10.1 PSI
20,000' AGL 6.75 PSI
30,000' AGL 4.36 PSI
40,000' AGL 2.71 PSI
A typical 747 cabin pressure is around 12.4 PSI, and typical cruising altitudes for 747's are 30-40k feet AGL... for 8 to 10 PSI above ambient - 0.57 to 0.71 Atm above ambient. The doors are heavy not so much because the hull is terribly thick, but because the doors lock into structure for crash resistance, include escape equipment, and sound and thermal insulation. They also contain gear to prevent their opening.
Now, 10 PSI on a 2.5x6' door... 30x72x10= 21600 pounds of force. The door latches are big to handle it on a smaller number of latches. But, I've seen what happens when one tries to force it inward, as well - not bloody much. The latch mechanism handles the forces, and water hitting at 50+ PSI (7+ atm) doesn't cause a leak through the seals. (That's a level of force deliverable from a backpack deicer or a pressure wand on a normal hose for washing down the plane.)
Some rough numbers
0' AGL 14.7PSI
10,000' AGL 10.1 PSI
20,000' AGL 6.75 PSI
30,000' AGL 4.36 PSI
40,000' AGL 2.71 PSI
A typical 747 cabin pressure is around 12.4 PSI, and typical cruising altitudes for 747's are 30-40k feet AGL... for 8 to 10 PSI above ambient - 0.57 to 0.71 Atm above ambient. The doors are heavy not so much because the hull is terribly thick, but because the doors lock into structure for crash resistance, include escape equipment, and sound and thermal insulation. They also contain gear to prevent their opening.
Now, 10 PSI on a 2.5x6' door... 30x72x10= 21600 pounds of force. The door latches are big to handle it on a smaller number of latches. But, I've seen what happens when one tries to force it inward, as well - not bloody much. The latch mechanism handles the forces, and water hitting at 50+ PSI (7+ atm) doesn't cause a leak through the seals. (That's a level of force deliverable from a backpack deicer or a pressure wand on a normal hose for washing down the plane.)
That's because you have never seen a watertight ship hatch dogged... REALLY, there is nothing to this. Unless you just refuse to really examine it.
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