# Aerial Ships - How heavy should an Aerial ship weight and what design to resist wind speed of 100-180 nautical miles per hour?

Ok, so we have an aerial ship that is propelled by thrustless levitation and propulsion. Considering it how much weight do they need and design to able to resist wind speed of 100-180 nautical miles per hour?

assuming winds can come from headwind and tail wind of the ship

size dimensions are from 60 meters to 800 meters

• The term X knots actually means X nautical miles per hour. If you write "100 knots per hour", what you're saying is 100 miles per hour per hour, which is actually a (fairly obscure) way of measuring acceleration. Probably not what you want. So how fast are those winds? en.wikipedia.org/wiki/Knot_(unit) – fgysin Mar 29 '16 at 6:43
• @fgysin ah i see, i'll rephrase that should i with 100 miles per hour? – mico villena Mar 29 '16 at 6:44
• 100 (nautical) miles per hour = 100 knots – fgysin Mar 29 '16 at 6:45
• This depends entirely on the capabilities of your "a wizard did it" drive system. You're way outside zeppelin capabilities so there's nothing to really compare to for non-aerodynamic flight. – Separatrix Mar 29 '16 at 10:10

With that kind of wind, streamlining is going to be extremely important. I'd expect the shapes to be pretty restricted; cigar shapes (like a submarine), or teardrop, or perhaps a flattened disc (flying saucer?). With no need for wings for lift, they might still have strong, stubby fins for stability... again perhaps like a submarine.

How heavy? Well, that depends on size. Scale up the size and the weight automatically increases, due to the cube-square law. But if it were me, I'd go with armor plating like a destroyer, or perhaps even like a battleship for larger ships, to withstand hits from any debris thrown around by more-than-hurricane force winds. Hopefully the energy requirement of the "thrustless" (I think you mean reactionless; the ship will still need both vertical and horizontal thrust) engines can support very heavy ships.

At any rate, you're talking about airships that need to be built as sturdily as ocean-going ships, not lightly built like airplanes.

OK. There are a few things to consider here:

1: What do you mean by 'resist' 2: How good are your engines? 3: How is your ship shaped? 4: What is your ship made of?

The first question seems trivial, but it isn't. If your ship is being hit by a wind (of any kind) then 'resist' can mean one of two things:

A: The ship only accelerates due to the wind at a rate that is lower than some arbitrary threshold. If this is what you mean by 'resist' then you need to remember F=MA, decide what the highest acceleration you're happy with is and work out how much force the wind is applying to your ship. There is a pretty good article on calculating force due to wind loading here, but please bear in mind that your ship design will hugely affect this.

B: The ship can 'station-keep' and stay where it is, even in high winds. In this case the mass of your ship is actually not an issue. The power and responsiveness of your engines is. If your engines can't push the ship along with an equal amount of force to the wind then your ship will move. If your engines can't ramp their thrust up/down fast enough to deal with changing wind conditions then your ship will move. Fengines >= Fwind.

Which brings us to your engines.

How these engines work is important. We know they provide at least 9.8 times the mass of the ship in force (assuming 1g gravity), or it wouldn't float. How much power over that they can provide affects the maximum windspeed your ship can fly into. We know that they can be turned on and off, or you would have no control. How much more force they have and how quickly they can go from 'on' to 'off' affects how heavy your ship needs to be in order to 'resist' gusts of wind to a level you're happy with.

Greater mass helps as you will need more powerful engines (in order to stay afloat) and the ship will be harder for sudden gusts to move, but if your engines are responsive and well controlled enough you could have an arbitrarily light ship. Again: F=MA comes into play, but now you need to look at your engines, how powerful they are and how well they can change the amount of force they provide.

All of the above depends on how much force the wind is delivering to your ship. This in turn is affected by the wind pressure (which scales with V2) and the projected area of your ship. The projected area is lower for aerodynamic ships, and higher for wall like ships. Either way: You need a ship that's aerodynamically shaped. If your winds are coming from the front or back but not the sides then a shape like two cones glued end to end will be a good bet.

And finally: The skin of your ship has to be tough (which affects the mass) and smooth (which doesn't). Constant exposure to hurricane force winds will expose any flaws or weakpoints and literally peel the hull from your ship: So don't give it the option. As Lensman noted in his answer there may also be other debris to worry about, so armour plating is a good idea. The other thing to consider is that the internal structure of your ship has to be able to stand up to 2x the force being delivered by the wind: It's being pushed by the wind on one side and your engines (assuming they can stand up to the wind) on the other. That's some epic stress. If you know where the wind is coming from consider bracing down the length of the ship with something that has a high compressive strength, or using multiple smaller engines rather than one big one (also helps with redundancy).

Hopefully some of this helps, but really the answer to this question depends on how good your engines are.