- #1
joe_gunn
- 7
- 0
Dear Friends,
I have a problem that has been driving me nuts for months now, and I am hoping you guys can help. I need to understand whether:
1. The Force with which a hollow, buoyant Steel Sphere is propelled upwards from under water at significant depth changes as the sphere ascends to higher elevations closer to the water surface? It seems counter-intuitive to me that the force exerted on the sphere 3 meters below the water surface, is identical to the force a 1000 meters below surface? My intuition tells me that due to higher pressures at the bottom, the force and therefore the rate of ascension should be greater at the bottom? If not, why not?
2. If I build a second hollow sphere of identical surface volume (yet different skin thickness – internal volume), but ensure that its internal gas pressure is say hundreds or thousands of times greater, will it ascend faster with greater force than the first sphere? After all, that extra pressure is not “visible” outside the skin of the sphere?
I understand that spheres must have a lower mass to volume ratio than water to be buoyant, however, to know the internal pressure exactly will demand a sensor, machining of a new opening, seals/gaskets (thus compromising further the integrity of the sphere and $$$). On the other hand, if I over-pressurize (for sufficient buoyancy) by filling it with say, dry ice, by the time all the ice sublimates to gas, the sphere will be at the bottom ready to surface; once manually triggered to do so. If my intuition is wrong, and if both spheres ascend at the same rate regardless of internal pressure, then all I need to do is machine the sphere to ensure minimal buoyancy, allow air to enter before closure and ignore the dry ice and pressure sensors.
Please disregard underwater temperature gradients, water densities, currents, and salinity issues.
Many thanks for your help.
I have a problem that has been driving me nuts for months now, and I am hoping you guys can help. I need to understand whether:
1. The Force with which a hollow, buoyant Steel Sphere is propelled upwards from under water at significant depth changes as the sphere ascends to higher elevations closer to the water surface? It seems counter-intuitive to me that the force exerted on the sphere 3 meters below the water surface, is identical to the force a 1000 meters below surface? My intuition tells me that due to higher pressures at the bottom, the force and therefore the rate of ascension should be greater at the bottom? If not, why not?
2. If I build a second hollow sphere of identical surface volume (yet different skin thickness – internal volume), but ensure that its internal gas pressure is say hundreds or thousands of times greater, will it ascend faster with greater force than the first sphere? After all, that extra pressure is not “visible” outside the skin of the sphere?
I understand that spheres must have a lower mass to volume ratio than water to be buoyant, however, to know the internal pressure exactly will demand a sensor, machining of a new opening, seals/gaskets (thus compromising further the integrity of the sphere and $$$). On the other hand, if I over-pressurize (for sufficient buoyancy) by filling it with say, dry ice, by the time all the ice sublimates to gas, the sphere will be at the bottom ready to surface; once manually triggered to do so. If my intuition is wrong, and if both spheres ascend at the same rate regardless of internal pressure, then all I need to do is machine the sphere to ensure minimal buoyancy, allow air to enter before closure and ignore the dry ice and pressure sensors.
Please disregard underwater temperature gradients, water densities, currents, and salinity issues.
Many thanks for your help.