I'm not a physicist, but I know at least one who reads this blog, so hopefully he will pass comment. There is a new project starting up, and if you can get past the horrendously naff 1990s style
website it's proposal is for a gravity powered plane. The plane is the brainchild of a theoretical physicist called Robert Hunt. According to the site,
The new hybrid “gravity-powered aircraft” is formed by merging the capabilities of the following devices into a single new aircraft apparatus: (1) an aircraft capable of aerostatic (lighter-than-air) lift to gain altitude; and, (2) a glider aircraft capable of aerodynamic lift, having a high glide ratio to accomplish long range gliding; and, (3) an innovative new extremely low drag vertical axis wind turbine that is capable of harnessing the force of the wind to generate power as the aircraft glides upward via positive buoyancy and glides downward via gravity acceleration.
Whether it will actually work is something I wouldn't even dare to say, but it's certainly an interesting idea if it can work. After all, it would produce genuinely low-cost air travel and have the added bonus of keeping the ever growing environmental lobby happy.
I'm not a physicist, but I know at least one who reads this blog, so hopefully he will pass comment. There is a new project starting up, and if you can get past the horrendously naff 1990s style website it's proposal is for a gravity powered plane. The plane is the brainchild of a theoretical physicist called Robert Hunt. According to the site, 
7 comments:
Sounds like a winner ... though perhaps not in and of itself ... but excellent technology transfer potential.
Sounds a lot like a Perpetual motion machine to me, so I'm sceptical about this idea.
It is not a perpetual motion machine, as it is using solar power. However, something in my vague recollection of thermodynamics makes me think the bit about the energy cycle will not work: 'Heat energy is taken from ambient temperature air at a lower altitude to power the GravityPlane and heat is rejected to colder air at high altitude to complete the power cycle.' Pressure drops as altitude increases, which means the boiling point of the 'special liquid' will drop. I suspect there is a strong probability that the gas never recondenses, so the aircraft will not glide down as planned.
A temperature gradient can be used to do mechanical work (taking energy from the hot source to a cold sink with some of that energy extracted as work), so the basic principle isn't breaking thermodynamical laws.
To get buoyancy, however, you need to change the density of the plane and that requires some increase in volume for the same mass (as it appears to be a sealed system). Didn't see how he plans to do that (some sort of balloon type dealy?).
Dizzy as i have studied physics it looks vaguely plausible.
You could certainly lift a glider to a great hight and let it go to glide a long way. If it can find a thermal it can climb in that and go much further.
That said I wonder how practical it would be.
What about strapping a piece of buttered bread (buttered side up) to the back of a cat. Then drop said cat and watch as it spins in perpetual motion, never touching the ground.
This uses the two known theory's that;
a. A cat always lands on its feet.
b. Buttered bread will always land face down.
Beat that.
yes but according to Shroedinger, the cat can be in 2 places at the same time; so it's on its feet and up in the air aswell.
Since I'm writing, I like the idea of 'forecasting' global temperatures a hundred years for now, when we struggle with tomorrow. They say it's averages. Do they mean, as in, on average it's Wednesday?
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