Gray Lensman
SOC-13
I had thought I saw a conversation here about what is the
largest ship that can land on a planet but my search has availed
me not.
largest ship that can land on a planet but my search has availed
me not.
Ship Sizes
- Thread starter Gray Lensman
- Start date
Gray Lensman
SOC-13
Thinking more along the lines of there being a maximum length ect.
More of a physical size limit than anything.
"My God, would you look at that monster"
Would you really be able to land a kilometer long ship?
More of a physical size limit than anything.
"My God, would you look at that monster"
Would you really be able to land a kilometer long ship?
First: It depends on the planet. Low grav, no atmosphere ... sure.
Second: Why not? Think of what we can do today that was not thought possible just a few years ago.
-Swiftbrook
Theophilus
SOC-13
My guess would be 1/4 planetary diameter. Obviously something like an Imperial Super Stardestroyer, At 19,000,000 meters (19,000 km or over Ten Thousand Miles, is that right? 1.6 to one, 10k is six miles, 10,000k is 6000 miles, is 19,000k is almost 12,000 miles) Boarding at the bow in Los Angeles and the stern at London, with central boarding at New York. Of course this assumes the bow and stern are in atmosphere. So I guess obviously there is an upper limit to size!
Gray Lensman
SOC-13
That's exactly the kind of thing I was thinking of 
Icosahedron
SOC-14 1K
Obviously, the curvature of the planet would form a limit, but a more practical limit would be ground pressure.
747s can't land just anywhere, not only because of runway length, but also because their weight would carve up runways that were not designed to take it. Runways have to be strengthened (read 'rebuilt') if they are likely to expect larger planes in the future.
I can see something the size of the QE2 being able to land on a specially constructed cradle (after all, it was built on one) but I can't see a ship ten miles long landing safely (Star Wars is pure space opera). Its ground pressure would be so large that the whole cradle would sink into the earth after a couple of landings. You would reach a stage where the landing platform would have to be rebuilt after every landing, and the cost would be prohibitive.
I could see ships maybe twice the size of today's biggest ocean ships being able to land in special cradles (if the pilot's good enough), say 500k metric tons (35k dT, say 50k), but I doubt if you could go much bigger than that.
Of course, if you're trying to land it on a Starport X, a few hundred dT would probably be your limit.
[IMTU] I limit it to LBB2 ships (5k dT). Anything bigger than that needs a different Pilot licence anyway.[/IMTU]
The above is IMHO, with no calculations made, of course.
747s can't land just anywhere, not only because of runway length, but also because their weight would carve up runways that were not designed to take it. Runways have to be strengthened (read 'rebuilt') if they are likely to expect larger planes in the future.
I can see something the size of the QE2 being able to land on a specially constructed cradle (after all, it was built on one) but I can't see a ship ten miles long landing safely (Star Wars is pure space opera). Its ground pressure would be so large that the whole cradle would sink into the earth after a couple of landings. You would reach a stage where the landing platform would have to be rebuilt after every landing, and the cost would be prohibitive.
I could see ships maybe twice the size of today's biggest ocean ships being able to land in special cradles (if the pilot's good enough), say 500k metric tons (35k dT, say 50k), but I doubt if you could go much bigger than that.
Of course, if you're trying to land it on a Starport X, a few hundred dT would probably be your limit.
[IMTU] I limit it to LBB2 ships (5k dT). Anything bigger than that needs a different Pilot licence anyway.[/IMTU]
The above is IMHO, with no calculations made, of course.
What if the starport was simply a dock out into a large deep lake? There are many example of Traveller starships landing in and floating on a sea. Water is an incredible "cradle" for a ship.
The Super Star Destroyer was never 19000 kilometers long. 19000 meters, maybe, but not kilo meters.
E.D.Quibell
SOC-13
Yes it is. However there is only so much water you can displace without causing problems on the shores of the lake, and/or the run off down the river.
Regards,
Ewan
While this is true for small lakes and rivers, the volume of even a moderately large lake, say Lake Champlain on the VT/NY border is immense.
Lake Champlain has a volume of 25,800,000,000 cubic meters. Given 14 Cubic meters per ton, a 1 million ton capital ship would be only 0.00054% of the total volume of the lake.
I don't really think we have to worry about a water landing. In fact if a large ship were to land, I would think a water landing would be the way to go. There would be no need for landing struts and an interal structure to support them.
My 0.02 CR
R
far-trader
SOC-14 10K
Water landings may be ok, as long as you don't sink to the bottom. And most ships sans CG will sink iirc. So don't shut down the power or the CG... but then you could just hover any old where right.
(math teacher hat) calculator => 0.00054 = 0.054%
Far-Trader said:
I'm not sure about that. I think it has more to do with shape. A lead rock would sink were as a large lead bowl would float. If a ship is streamline then it should be able to float if you want it to. Jumbo jets float, it's only when they fill with water do they sink.
(babbling mode ... sorry)
-Swiftbrook
far-trader
SOC-14 10K
It depends on a lot of factors. Chiefly displacement vs mass. Which involves local gravity, load state of the ship, density of the local "water" the landing is made in and probably some other factors I'm forgetting.
Depending on the rule set in use iirc displacement vs mass varies from 1 to 1 (might float if empty) in CT for cargo ships, to something like 1 to 15 (sinks like a rock) in MT? TNE? varying by armor and load.
Then there's issues of suitability of the hull for water landings in the first place. I'd agree that Streamlined would be, to a reasonable degree, not so for Partially or Unstreamlined imo.
No need to apologize, allowed me to babble a bit too
Yep I forgot to shift the decimal by two spaces when I made the calculation. Thanks for the catch. My point is still the same, it is a very small percentage of the total volume. of the lake.
I do not know what streaming has to do with flotation. I half filled water jug is not streamlined yet it floats. Flotation is all about density. Water has a density if 1000 KG per Meter cubed. Considering every ship afloat, including supertankers and ever increasingly large cruise ships, is under that mark, it is not too much to assume a Traveller spaceship would be below that as well. Although it would have to be streamlined to reach the water in the first place.
Also a spaceship would be sealed for the vacuum of space. To prevent air leaking out. If a water landing were part of the design spec, I am fairly certain it would not be too difficult to design the ship to ensure water could not leak in, given that the pressure is working in the opposite direction.
R
far-trader
SOC-14 10K
As you note, one bit is the ability to actually enter an atmosphere that would have liquid water*.
Others include systems to keep said water* and critters living in it from adversely affecting the ship. Hatches that seal off drive exhausts. Electrical charges to keep critters from attaching. Special alloys to prevent corrosion. I dunno, stuff
Just because a space ship can keep air in under a vacuum does not equate to keeping water* out under pressure.
It's all extra expenses and since streamlined hulls generally cost more that seems a fair rational.
* or whatever liquid the world has
Super tankers are double hulled iirc, partly to contain spills but iiuc mostly for displacement to float with a full load.
A Traveller ship with empty jump fuel tanks would provide enough positive displacement, probably, to float the ship. It depends. The quickest simplest rule of thumb is civilian ships can float if streamlined even fully fueled. Higher if unloaded. Military ships sink when fully fueled and must still be streamlined to engage the environment.
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As you note, one bit is the ability to actually enter an atmosphere that would have liquid water*.
Others include systems to keep said water* and critters living in it from adversely affecting the ship. Hatches that seal off drive exhausts. Electrical charges to keep critters from attaching. Special alloys to prevent corrosion. I dunno, stuff
Just because a space ship can keep air in under a vacuum does not equate to keeping water* out under pressure.
It's all extra expenses and since streamlined hulls generally cost more that seems a fair rational.
* or whatever liquid the world has
Super tankers are double hulled iirc, partly to contain spills but iiuc mostly for displacement to float with a full load.
A Traveller ship with empty jump fuel tanks would provide enough positive displacement, probably, to float the ship. It depends. The quickest simplest rule of thumb is civilian ships can float if streamlined even fully fueled. Higher if unloaded. Military ships sink when fully fueled and must still be streamlined to engage the environment.
I did cover that water leaking in issue in my previous post.
As for empty or full fuel tanks I am not sure it matters so much, liquid hydrogen has a density of 67.8 KG/M cubed where as water is 1000Kg per M cubed at 4 C and 1 atmo. I am not so sure that would tip the balance. Traveller ships, like modern day ships have lots of empty space inside.
R
Averge mass of FF&S civilian designs is around 6Mg/14kL... 6 metric tons per displacement ton... when empty.
Small-ship combattants work out to 10-12Mg/14kL...
Since both of these reduce to below 0.98Mg/kL, which can itself reduce to 0.98kg/L, one can readily see most ships will float without CG. HEPlaR, however, will do NASTY things to water... :smirk:
Small-ship combattants work out to 10-12Mg/14kL...
Since both of these reduce to below 0.98Mg/kL, which can itself reduce to 0.98kg/L, one can readily see most ships will float without CG. HEPlaR, however, will do NASTY things to water... :smirk:
