How could you get to svalbard?

Some cruises of the Norwegian coast go to Svalbard, however the safest and cheapest method is a flight from Tromso to the one public airport on the island which is in Longyearbyen, this flight goes about once a day, flights from Tromso to the Norwegian capital Oslo are far more regular.
There are a number of restrictions in Svalbard about where you are allowed to be, much of the island is reserve, not to mention dangerous, it is against the law to leave the town area of Longyearbyen without a method of defence against polar bears.