Why is streamlining necessary?

[Shadow Bear]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Uncle Bob:
Lessee, standard volume is about 14m3/ton, so if you land in water only about 7% of the ship gets wet.<HR></BLOCKQUOTE>

Assuming of course a flat stable keel for the vessel. If the vessel is not designed to float it could capsize. If the vessel is not streamlined it could have all sorts of problems. Think ariels or probes snaging the bottom. And then again it would bob like a cork.

 

[Uncle Bob]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Shadow Bear:
Assuming of course a flat stable keel for the vessel. If the vessel is not designed to float it could capsize. If the vessel is not streamlined it could have all sorts of problems. Think ariels or probes snaging the bottom. And then again it would bob like a cork.<HR></BLOCKQUOTE>

What's streamling got to do with it? A wedge would be fairly stable on the water, but a needle has the same problems as a cylinder. A close structure could be good or bad, and a sphere would roll like a pig but the engines in the bottom of the ship will make it difficult to caspsize. As for protrusions from the bottom, you can extend the landing gear to protect them.

Ouch I just did the math. A sphere will have only 15% of its hull diameter "wetted", somewhat less for any other shape. And that sphere can be capsized, being self righting is small consolation. They will all roll like pigs and skitter before even a light breeze

At least you won't have to worry about the arials and probes as long as you have a couple of meters to float in

[This message has been edited by Uncle Bob (edited 19 August 2001).]

 

[DrSkull]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Uncle Bob:
Lessee, standard volume is about 14m3/ton, so if you land in water only about 7% of the ship gets wet.<HR></BLOCKQUOTE>


But that "ton" you mention isn't weight, it is "displacement tons of liquid hydrogen"--a measure of volume. CT tells you nothing about the actual weight of Starships.

If you look at MT, you'll see a 200 "ton" vessel actuall weighs 1533 metric tons (unloaded) and 2604 metric tons loaded. (Solomani and Aslan supplement p 95, Aslan Seeker ship). Since 2800m3 is its volume, that equals 2800 tons of water, a loaded vessel still floats, but most of it's underwater.


------------------
Dave "Dr. Skull" Nelson

 

[Uncle Bob]

Thanks for reminding me why I disliked MT

 

[GypsyComet]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Uncle Bob:
Thanks for reminding me why I disliked MT

<HR></BLOCKQUOTE>

Gee, and everything else other than High Guard, too...

Weight is just a detail. You only need to design with weight in mind if you want a ship to float.
Oddly enough, only Striker ever made a real issue of weight for vehicles, since it actually had rules for ground pressure. I actually found it worth knowling for RP purposes, since it adds color to some vehicles. Knowing you can't turn off that gravcar's AG unless sitting on concrete is one of those things that can bring a smile to a ref's face and great deals of swearing forth from players...

 

[DrSkull]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Uncle Bob:
Thanks for reminding me why I disliked MT

<HR></BLOCKQUOTE>

But dude, "tons" weren't a weight measure in CT ships either, weight was compeletly ignored. The only time a "ton" on a CT spaceship weighed a "ton" (1000kg) is when it was the fuel tank.



------------------
Dave "Dr. Skull" Nelson

 

[Shadow Bear]

<BLOCKQUOTE>quote:</font><HR>Originally posted by DrSkull:

But that "ton" you mention isn't weight, it is "displacement tons of liquid hydrogen"--a measure of volume. CT tells you nothing about the actual weight of Starships.

If you look at MT, you'll see a 200 "ton" vessel actuall weighs 1533 metric tons (unloaded) and 2604 metric tons loaded. (Solomani and Aslan supplement p 95, Aslan Seeker ship). Since 2800m3 is its volume, that equals 2800 tons of water, a loaded vessel still floats, but most of it's underwater.

<HR></BLOCKQUOTE>

A vessels ability to float would depend on how densly it was constructed and how full the cargo and fuel spaces are at the time you try to float it. It the same for solid surfaces only the question becomes how much ground pressure can the surface hold without damage. Think about setting a large ship on a freeway or runway using just a few small landing legs. Remember those signs on some roads limiting weight for trucks.

 

[shadowdragon]

Seems to me the weight of a ship would be determined more by the materials it is made from. For example, if you place an iron skillet in the bathtub, and fill the tub with water, regardless of the skillets displacement, it will not float. Another skillet, made of aluminum, of the same size, displacing the same amount, floats quite readily. Anyone seen any rules additions to take this odd feature into account? It seems to me that a TL-14 2-G maneouver drive should be more compact, weigh less and be more efficient than a TL-9 drive. Even an early TL-9 should be bulkier and less efficient than a later model. Help?

 

[parmasson]

Capsizing and rolling in water should not be an issue with artificial gravity. Weeeeeeeee

Citizen Shadowdragon,

When it comes to drive compactness and all of those other details.
[clears throat]
So let it be written, so let it be built, so let it be played.

If I can accept the existence of Jump drives and thruster plates that violate gobs of physical laws then I can bring myself to accept the drive size/technology level issue.

From Gikur's comments on the Little Black Books Vol.4, Chapter 9 pg 1,285 and Vol 6 pg 356. (1107 revised edition 3rd printing)

 

[parmasson]

Where are my manners,


First off welcome to you citizen shadowdragon. Around here there is always room for one more Traveller.

Enjoy the ride……

 

[Black Globe Generator]

Originally posted by shadowdragon:
It seems to me that a TL-14 2-G maneouver drive should be more compact, weigh less and be more efficient than a TL-9 drive. Even an early TL-9 should be bulkier and less efficient than a later model. Help?

My particular explanation for this phenomenon is (hands wave furiously).

I put my mind at ease on the component size question by assuming the technology is such that it can only be made so small, period - there is a hard physical limit to how much miniaturization can be achieved for reactionless maneuver drives, fusion power plants, and jump drives. Any breakthroughs in this technology will come at higher TLs than are currently available IMTU (and therefore may appear in the form of experimental ships or Ancient artifacts!).

It's certainly not a perfect explanation, but it suspends disbelief sufficiently for my purposes.

 

[Fritz_Brown]

Welcome, shadowdragon!

The floatability of a mass is determined by its overall density v the medium in which it is set. That iron skillet will float if it has high enough sides (well, it really wouldn't be a skillet anymore, but I digress), because it will displace water that weighs more than it does - all that air in the middle makes the difference. If your ship has a sufficient quantity of atmosphere inside it, it will float - even made of bonded superdense. Of course, if your cargo door leaks and you start taking on water....

 

[shadowdragon]

Right-o! My point about the skillets lies in the fact that 100 "displacement" tons does not necessarily add up to 135 tons weight as stated on pg 254 of t20. If the hull is aircraft aluminum, and the interior of the ship uses up 80 tons or so of space- dedicated to living spaces (mostly air), cargo spaces (also mostly air), fuel tankage (if full weighing in at approx. 100 tons per 14 m^3, but if empty, mostly air). That leaves 20 displacement tons of actual hull mass. 20 displacement tons of aluminum is lighter than say 20 displacement tons of concrete. (I think I have that right. Volume and mass seem to overlap at odd points to me but I'm just a goob) Ship components are all listed as displacement tonnage to reduce the volume available for construction.

Going back to what type of ships can enter an atmosphere, regardless of displacement, weight, or streamlining, as far as the physics go, as long as the entire structure is supported against gravity any shape or structure can enter or leave the atmosphere as long as:
1. Re-entry speeds are low enough to prevent heating the hull to failure. The failure temperature will vary due to hull material, thickness and density.
2. Wind and re-entry speeds are low enough not to damage or destroy exposed hull components. Pesky little things like aerials and dishes are rather unstreamlined items. Dropping into a class 5 hurricane is less than happy making as well.

Landing that ship is another matter entirely. Any vessel not designed to support its own weight against the pull of gravity can not remain entirely intact if required to do so. IMHO one point of not allowing certain hull types to enter an atmosphere is simply anyone doing so will prolly attempt to land that thing, and get really upset when they find out the ship is essentially destroyed. But I see no reason not to allow atmspheric entry provided the hull is designed to be self supported against gravity in the particular vector it lies, the ship can hover, and enter so slowly that the ship can't sustain heat or wind damage.

At least that is my inexpert understanding of the relevant physics. I could be wildly bonkers for all I know.

Btw the GM screen I have for MT shows a scout/courier floating in an ocean to refuel, and about 85-90% is submerged.

 

[jasper]

HMMM time for chart
Jamming Jasper Pilot Mishap chart or How to spill coffee in the Captain's lap while taking his jib for a spin.
01. Air turlance. Minor 50% of liquids being spilled out open mugs.
02 Air turbulance. Medium 75%
03 Air Turbolance major any liquid not covered is now covering the ceiling.
04 Water landing. Minor. Mud and debris can be clean with 3 man house of hosing off ship
05 Water landing. Minor. Bottom third of landing jacks in water.
06 Water landing medium. Good news the ship is floating. Bad news water line is a few inches above bottom of air lock door.
07 Water landing major. Who put the fish screen saver on all the windows.
09 water landing bad. Say Captain what is crush depth of the ship.
10 Land bad. Bounce on landing. 1 day to repair landing jacks 10% cargo damage. Any one not seated 20% of minor injury.
11. Landing bad. Bounce on landing. 7 days to repair jacks. 20% cargo shifted.
12 Landing very bad. Jacks are now art deco junk lying on tarmac
13 Landing major. Jacks are gone. Air lock door floor 1 meter below ground level.
?????

 

[Commander Drax]

Hmmm

I wondered about this too, so I made the rule that all vessels could enter atmosphere, though performance was hindered by lack of streamlining as per MT

USL 0-300 kph max
SL 1000 Kph Max
AF as per drive maximum performance.


Also it did say in the MT starship operators manual that most 1G rated ships equipped with M-drives left higher grav ity worlds by overdriving their engines/ All M-drives could be overdriven by up to 40% for up to a few days without risking catastrophic burnout or up to 400% for a few minutes such as when conducting a VTOL landing at a starport. Hence a 1G rated ship could leave a 1.5G gravity well by overdriving the ship's thrusters to 2G, resulting in an ascent acceleration of 0.5G, which is effective if a little slow.

Likewise, atmospheric entry to USL ships not exceeding 300 Kph, was more dangerous simply because of the increased length of time descending through the atmosphere, which could result in an increased chance of a mishap, such as being caught in turbulence or between two converging airstreams or bad weather patterns. Hence it was easier for these craft to stay in orbit and let a more atmosphere friendly subcraft do all of the work, or rely on local shuttle services.