I have seen gravity storage systems that were used for electricity generation at the end of the nineteenth centaury but they were large with several hundred Kgs wound up tens of meters.
This is rather a "how long is a piece of string" question but as it takes very little force to move a hovercraft once it is air born I would go for about a 1KW fan.
These explosive percussion caps were not originally intended as toys but for use in pistols and rifles, when I was a boy you had to be over 16 to purchase them, I believe they are a mercury compound .
I think this fear of radiation was in a large part cold war propaganda to reduce the fear of a nuclear attack you weren't going to blown to bits or burnt to death as most of the victims at Hiroshima were but the main danger was RADIATION that could be stopped by some newspapers covering the windows.
Only the very largest of ships diesel engines achieve a thermal efficiency of 50% the conversion factor for a car engine is more like 25% at reduced throttle openings.
The DC transmission of power is much more appropriate for use with undersea cables such as the quite small system between England and France or the much larger schemes contemplated to bring geothermal power from Iceland to Scotland or Germany.
When AC is used with undersea cables there is...
When colour TV first started in the UK the available picture tubes had rather a poor life due to loss of emission from the cathodes.
As replacement tubes where expensive a cottage industry sprung up fitting new gun assemblies to the tubes and re pumping and re gettering them.
Eventually tubes...
With a short stroke a problem arises with clearance for the valves makers of high performance engines tend to favour an equal bore and stroke a so called square design
I find it quite incredible that a 7.3 Hz magnetic field of 1 picotesla can have any effect on the human body that is unharmed by the 2-3 Telsa field of a MRI machine