Sunday, November 2, 2014

Airships and Barbarians

There was a brief pleasant time when I could throw a question out on the interwebzz and get answers and research delivered to me. that seems to have stopped because I've rattled on about things enough for people to realize I can do the heavy lifting research myself.


Anyway, the Sperans, my space barbarians had a low tech equivalent to an air raft. Keep in mind when I say barbarians they still are TL 5 (early WW 2 in Earth terms). Since the prevalent interstellar culture in this setting is TL 9 I guess a barbarian is anyone 4 tech levels or more below you and TL 12 cultures will probably laugh their asses off at our 3D printers before they add water to their dehydrated air cars and fly off.

When Earth and the Fringe Worlds reestablished contact with Peraspera the locals had lost the infrastructure and tools to manufacture gravitics. Nonetheless Scouts making contact were amazed to see flying ships. Besides blimps and dirigibles the colonists had a number of open-topped trimaran craft that just ... floated without props or thrusters. The secret lay in the planet's exotic atmosphere. The first few hundred meters of Peraspera's atmosphere was half sulphur hexafluoride. This inert was not toxic, though it could still suffocate you much like CO2. Unlike CO2 'sulfex' was sic times as dense as air. A cubic meter of sulfex weighed a little over 6 kilograms. The lower atmosphere had a density of 3.5 kilos per cubic meter. The dense gas had a sharply bounded layer with a breathable atmosphere at standard pressure above. Placing a container of air of light construction atop the lower layer was quite easily done, as long as it was air tight.

Since the breathable upper atmosphere had a density of 1 kilo per cubic meter it had a net lift of 2.5 kilos per cubic meter, nearly double that of hydrogen in a standard atmosphere. Moreover the airship could be open topped resembling an old style water craft. Since rolling too far would let sulphur dioxide in and it's very hard to bail out an invisible gas the airship should be very stable with a trimaran style hull.

I worked up a TL5 airship from JTAS #2. It has three 'envelopes' each with a diameter of 8.5 meters and a length of 70 meters. The airship masses 40 tons and it's 'gas bags' have a volume of 50,000 cubic meters. The ship generates a lift on Peraspera of 100 tons, allowing it to carry 60 tons of cargo. The TL 7 airship had fuel cell driven motors but that's a little advanced for TL 5. Old style diesel motors will suffice but I'd reduce the operating time of the airship to two weeks. The airship can cruise at 35 kph. Unlike Terran dirigibles the craft can have an open top to save weight. It just needs high sides to make sure no sulfex gets inside. Even so air quality has to be monitored closely and some crew will always be wearing oxygen masks. Unlike Terran airships our craft can't really change its altitude much making it more like a boat than a balloon convertible.

I'd ride in it. Why should the barbarians have all the fun?