Closing Off Rapture

* See also Rapture_Timeline
* See also Secrecy_For_Rapture
* See also Rapture_Economy
* See also Crash
* See also Industry_In_Rapture
* See also The_Smuggling_Operation
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Ryan shut-down/cut-off/closed most communication/interactions/travel with The Surface to improve the Secrecy which was a big part of Rapture's Security, and to increase efforts to achieve long-term self-sufficiency ( a critical thing if the Surface world was Destroyed ).
I Would expect the date for this to be around 1952, after Rapture's Primary Construction had ceased, and most/all of Rapture's immigrants had arrived.
This also meant The Surface largely ceased being the source of goods consumed in Rapture.
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The MMORPG Would Elaborate :
The BioShock games were Vague about many details of Rapture's Society and the way it operated. ( They were Shooter Games and NOT Documentaries. ) They show and only hint at many situational aspects which would ( at various points -- definitely EARLY ) require alot of connections existing to The Surface World. Storywise, you cannot have Being Close Off be 'a big thing' unless there previously was a lot of Surface World interactions.
The Immigration Period in particular had a great deal of 'interfacing' between the places people came from and Rapture. The Construction likewise had.
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Even before Rapture was 'Closed Off' :
http://www.game-archivist.com/rapture/img/museum/signs/fullsize/Contraband_All_Imports.jpg
SO, Import Inspections were done and various 'Contraband' prohibited/prevented/intercepted.
* Looking for diseases that would affect people, animals and plants.
* Inexpensive products that might interfere with Rapture's own goal to be Self-Sufficient.  List of such items would have expanded as immigrants set up their production in Rapture.   Likely tariffs would have to be paid to achieve price parity of similar items, and tariffs would pay for the inspection process.   The external overhead costs to get many ordinary products into Rapture may already effectively do this.
* Propaganda from sources contrary to Rapture's Philosophy would be blocked.   Items that would make citizens nostalgic for the Surface World likewise.
* Dangerous items ( and/or ones not being handled properly ) -- ie- Radio-Isotopes that could poison huge areas of Rapture accidentally.
* Communications with outsiders that might endanger Rapture's Security & Secrecy.
Even allowed items not covered (above) would need to go thru controlled channels to protect Rapture's Secrecy.
* Useful Technical Information and Tools from The Surface would probably face No Prohibition ( would still have to be checked thru ).
* Resources which Rapture could never produce would be being Stockpiled ( the "Hundred Year Stockpile" ).
* Luxury Goods might have some premium levied on their import which would help pay for the General External Security Measures ( every item that comes into Rapture has some security risk potential ).
* Items brought WITH new Immigrants are handled separately. They add to Rapture's net wealth ( and prosperity when they are business/production/manufacturing related ).   There may have been virtually no volume limit on what came, as long as the immigrant paid for the transport overhead -- Again via standard security-controlled channels.
* Exports also.  Something has to be used to pay for any imports.  Excessive outflow of 'things of value' to pay for the imports.   Anything that might hint at Rapture's existence was 'at issue'.  Money which was slowly liquidated from the inhabitants past 'Surface' lives would (for a long time) be available (and facilitated) for this purpose.
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