Being a fan of the Mortal Engines books, I like the idea of slightly up armoured and sturdy airships (the movie was pretty but deviated a lot from the books). Some of the movies concept art is awesome though and very evocative. This one is particularly inspiring.
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| Mortal Engines concept art by Ian McQue |
The new vehicle below is intended to be a template I can work off to create various custom fits for air encounters. In also experimenting with a new vehicle stat block.
The Hornet Twin Envelope Airship
This twin rigid envelope design aerostat is built for the rough and tumble life of a trader. While drawing on less advanced materials compared to visitor vessel its reinforced hull makes it sturdy, though unable to haul the comparable loads. The design incorporates powered fan systems into the 20-foot-long airframe allowing for rapid speed and manoeuvrability. The main cabin is small and cramped with a bunk and head towards the back that is enough to provide comfort for one, but discomfort for its crew of four.
The lift is achieved through airbags utilising pure air sourced from alchemists through their arcane practices. This ingenious element making the design more compact than mere heated air that more common balloons can provide. Pure air cost 12gp per stone and contains six parts of the concoction. When exposed to the envelope gasses the vehicle can fly and consumes 9 parts per day of operation. Overall, the envelopes can hold 30 stone (180 parts) of pure air giving it a 20 day operation period.
In combat the pilot focuses on steering the vessel and the passengers can operate the three arbalest turrets placed around the vehicle. These turrets mount massive steel bolt ammunition that is effective even against the toughest alien vessels.
The design itself is common enough that parts, fuel and used vehicles can be found in many major towns. When purchased used they often come with custom modifications and a shrewd merchant can snap up a deal. They can be built by a 5th level machinist at a +6 build penalty taking 39 days at a base cost of 32,375 gp.
Hornet Twin Envelope Airship (Huge Machine)
The lift is achieved through airbags utilising pure air sourced from alchemists through their arcane practices. This ingenious element making the design more compact than mere heated air that more common balloons can provide. Pure air cost 12gp per stone and contains six parts of the concoction. When exposed to the envelope gasses the vehicle can fly and consumes 9 parts per day of operation. Overall, the envelopes can hold 30 stone (180 parts) of pure air giving it a 20 day operation period.
In combat the pilot focuses on steering the vessel and the passengers can operate the three arbalest turrets placed around the vehicle. These turrets mount massive steel bolt ammunition that is effective even against the toughest alien vessels.
The design itself is common enough that parts, fuel and used vehicles can be found in many major towns. When purchased used they often come with custom modifications and a shrewd merchant can snap up a deal. They can be built by a 5th level machinist at a +6 build penalty taking 39 days at a base cost of 32,375 gp.
Hornet Twin Envelope Airship (Huge Machine)
Build Notes
The mechanist build for this vehicle is as follows:
Utility Airship
Utility Airship
Hit dice: 9 (36 VHP, save F5, structural vehicle)
Armor class: 7
Move: fly 240’ (80’)
Weight: 810 st. (5.7 tons)
Carry: 405 st. (3 seated passengers plus one passenger cabin for 260 st.; 30 st. fuel, 90 bolts for 15 st., 100 st. cargo)
Attacks: 3 Stabilised steel rod heavy arbalests (1d8 VHP damage, +1 to hit, range 120’)
Positive abilities (total): Automaton immunities *, increased AC +2 ##, Increased move (flight +180’) * ####, Movement mode (flight, full hover, replaces ground) ###, passengers (4) ###, protected compartment ####, Ranged attack (15' multiplier) ###, reinforce structure *. (***** ###)
Negative abilities (total): Requires operator (mechanist or learned) *, Requires ammunition (Steel arbalest bolts, 4 gp each, 6 per stone) ####, Other negative ability (Requires pure air to operate, 12 gp per day) ####, Restricted movement (uncontrollable in strong winds) ####. (** ####)
Cost (net abilities): 32,375 (** #### ###)
Design elements
I restricted the weight and carry capacity but was shooting for a reasonable amount of hit dice. It needed this to be able to go toe-to-toe with a visitor scout. 9HD gives me a good weight allowance with solid health.
I added a full passenger to this design at 200 stone to represent a small cabin. This would be shared by two people at a time leading to a lack of comfort. With a crew of four doing two shifts this vehicle can operate for a full day while two of the crew sleeps on the bunk.
Finally, it needs an operating cost. The flying saucers and other visitor vehicles are powered off crystals, so I want to enforce a cost to operate. Using the cost of a quarter charged crystal as 5gp you can operate a scout at 10 crystals a day giving a cost of 50gp. I think Terran vehicles will have a lower cost, maybe half that, so a much reduced cost of 20% seems appropriate (higher tech will still be much better). I wanted to use a fantastic source, not a mundane fuel. Like gunpowder not being officially called gunpowder in my setting. In the end I came up with Pure Air, sourced from the elemental planes and distilled in the laboratories of alchemists.
Edit: for reinforced vehicles I assume 6HP per HD.
