What does it feel like to handle?
Fly it
The project’s own 6-DOF solver at 100 Hz, with the full added-mass tensor. Slow to respond, slow to stop, and overdamped at cruise where it wallows at rest.
Fly it
This runs the project's own 6-DOF solver at 100 Hz, not a simplified version for the browser. The same step function the validation gates exercise is called here, so if the vehicle feels wrong there is no second implementation to blame. Expect it to be slow to respond and slow to stop: the displaced air nearly doubles the effective mass in sway and heave.
Hold a control above, or click the view and use the keyboard: W and S for thrust, arrow keys for elevator and rudder, Q and E to drop and take on ballast, R and F to tilt the propulsors. Everything responds slowly, because the vehicle does. Tilt them all the way up with thrust on and watch the pitch: every unit is aft of the centre of gravity, so vectored lift is also a nose-down moment and the ship settles bow low. That is the vehicle, not the simulation. Loading.
Two things it does that an aeroplane does not
It wallows when stopped and is dead-beat under way. The pitch pendulum has a period around thirty seconds and no aerodynamic damping at zero airspeed, because the fins have no dynamic pressure to work with. Above about 10 m/s the same mode is overdamped. Both are correct, the difference is large, and a control law tuned at one end will misbehave at the other.
The fins are enormous, and they have to be. Setting the fin restoring moment against the Munk moment, the dynamic pressure and the incidence both cancel, leaving a minimum area that is independent of speed and altitude. For this hull it is about 174 m². A first guess of 60 m² diverged just as surely as no fins at all: below the minimum there is no partial credit.
Putting it down, and picking it up again
A buoyant vehicle does not lift its weight on vectored thrust. It lifts its residual HEAVINESS, which is a couple of percent of the weight, so the thrust needed is two orders of magnitude below a helicopter of the same mass. Zeppelin NT is certified to 400 kg of static heaviness at take-off on an 8,050 kg vehicle, and lifts it on tilting propellers.
Diameter is the only variable that matters
Momentum theory gives static thrust proportional to (ρAP²)1/3, so at fixed power it goes as the four-thirds power of diameter. Doubling it is worth 2.5 times the thrust for the same kilowatt, and a duct is worth a further factor of two because the shroud carries a suction load of its own and stops the wake contracting.
| Diameter | Open | Ducted |
|---|---|---|
| 3 m | 449 kg | 530 kg |
| 4 m | 544 kg | 642 kg |
| 5 m | 632 kg | 745 kg |
| 6 m | 713 kg | 842 kg |
| 8 m | 864 kg | 1,020 kg |
Momentum theory alone would have promised 2.7 times these figures. The realisation factor against certified airship installations is 0.37: tip losses, non-uniform inflow, the download on the body under the wake, and a propulsor sized for cruise working at zero airspeed.
Losing one is not the helicopter case
A heavier-than-air VTOL that loses a rotor in the hover is descending immediately and the only question is how hard it lands. This one is still buoyant. It loses the ability to place itself and keeps the ability to stay up.
That is what sets the landing trim. Four propulsors lift 842 kg and three lift 207, so the vehicle is trimmed to 550 kg rather than to whatever keeps it still in a chop. A trim it can only leave with every propulsor running turns one failure into a vehicle that cannot take off again.
On the ground it holds itself bow-on in 17 m/s, above the 6.3 m/s the US Navy would dock a ZPG-3W in with a mobile mast, two mechanical mules and eighteen trained people. It does not help broadside, where it manages 2.7, and no plausible installation would: the broadside force is an order of magnitude larger and thrust scales with power. What it removes is the crew, not the need to weathervane.
Move a parameter and watch what breaks
Every figure here is recomputed by the same solvers the tests and the reports use. Infeasible regions are shown as infeasible rather than as a small number: a hull that cannot lift its own structure says so, and a wind the vehicle cannot hold against turns the verdict red.
Every figure recomputed by the same solvers the tests and the reports use. A hull length change costs about 300 ms because the solar year is integrated again from scratch, so the panel dims while a result is stale rather than showing a number that is no longer current.