Science Forums 2

[CraigD]

Originally Posted by Turtle

Here is where my proposal fits, and is perhaps yet not understood. By having the living space & mechanics attached rigidly but gymbaled, power is applied at the axes to cause the FBS to rotate and using the Magnus effect we achieve propulsion. Changing the axis of rotation steers the FBS.

There’s a major problem with this scheme.

The Magnus effect produces a force proportional to the square of the velocity of the airspeed of the rotating sphere or cylinder. Balloons and other unpowered lighter-than-air craft, however, move with the wind, and thus have effectively zero airspeed. So, no matter how much power is used to rotate the envelope/hull of the big airship, and how great its angular velocity, the resulting right angle force will be effectively zero.

When moving from between volumes of air with differing wind velocities, there is duration of time before a LTA craft matches the wind’s ground velocity, but it’s brief.

If you want to be able to move a LTA craft against the wind, you need either a thrusts-producing system, such as jets or propellers, a ground/water anchor, or some more exotic but still propulsive system. Due to a big LTA craft’s large frontal area, even if very aerodynamically efficient, it will have a high drag, so moving it at even a low airspeed will require a lot of power.

If the LTA craft can quickly, reliably and accurately change its altitude, and has good data about wind velocities at different altitudes (eg: via detailed doppler radar), it can potentially navigate effectively by selecting an air mass going the desired direction. This is how modern recreational hot air balloons navigate. Even without good wind velocity measuring systems, a good balloonist can, under suitable wind conditions, make round-trips accurately enough to land in the same field he/she takes off from.