Heaven help us if the thing falls, or parts ever break off though.
Secrets of flying saucers discovered!?
- Thread starter Carpe Occasio
- Start date
Heaven help us if the thing falls, or parts ever break off though.
The trouble with using a lighter than air spacecraft is that it's too heavy. That's right - too heavy. Note how big that tire company's blimps are, several dozen feet in diameter and well over a hundred feet long (I don't have the exact dimensions). All that to carry a little TV equipment and under a dozen people in a lightweight cabin the size of an ordinary passenger van.
Remember the Hindenburg? An eight hundred foot long 125 foot diameter vehicle to carry a compliment of only about 90 people (crew and passengers) in an inhabitable space made of cloth partitions and lightweight aluminum and cloth webbing furniture. That's with the more efficient but extremely flammable hydrogen lift gas. Compare that with the size of a winged airplane that can transport 90 people.
Just because a craft is lighter than air, that doesn't mean it's light. All those thousands of cubic feet of air are heavy too. The lower weight of the lifting gas (even if it's heated air) merely lowers the total mass (gas, airship, passengers and cargo) to the mass of the same volume of air. Note that at high altitudes there's less air per cubic foot and the volume of your airship has to be enlarged to keep get the airships density to that less dense average.
Also remember that any velocity you achieve deep enough within the atmosphere to float an airship results in an elliptical orbit with a perigee at the same altitude you started with. By the time you complete a full orbit you're back down into the atmosphere deep enough for drag to take back much of your speed. You're going to need some sort of propulsion that will work in a vacuum (like a rocket) to fire at apogee to raise your orbit's perigee out of the atmosphere.
Remember the Hindenburg? An eight hundred foot long 125 foot diameter vehicle to carry a compliment of only about 90 people (crew and passengers) in an inhabitable space made of cloth partitions and lightweight aluminum and cloth webbing furniture. That's with the more efficient but extremely flammable hydrogen lift gas. Compare that with the size of a winged airplane that can transport 90 people.
Just because a craft is lighter than air, that doesn't mean it's light. All those thousands of cubic feet of air are heavy too. The lower weight of the lifting gas (even if it's heated air) merely lowers the total mass (gas, airship, passengers and cargo) to the mass of the same volume of air. Note that at high altitudes there's less air per cubic foot and the volume of your airship has to be enlarged to keep get the airships density to that less dense average.
Also remember that any velocity you achieve deep enough within the atmosphere to float an airship results in an elliptical orbit with a perigee at the same altitude you started with. By the time you complete a full orbit you're back down into the atmosphere deep enough for drag to take back much of your speed. You're going to need some sort of propulsion that will work in a vacuum (like a rocket) to fire at apogee to raise your orbit's perigee out of the atmosphere.
Indeed. So the premise of the orbital airship is that giant size and weight is affordable because it's so low-tech - more affordable than a rocket a fraction the size and ten times the payload mass, because the airship is also reusable. And the problem with the decreasing density of atmosphere is to be handled by using multi-stage airships, the upper stages being even flimsier than the lower ones for greater performance.
The resulting system is very limiting, of course. But there's some growth potential that wouldn't exist if the same basic technique were modified for the air-ionizing propulsion system which doesn't exactly cater for multi-staging or the economics of size and simplicity.
Timo Saloniemi
The resulting system is very limiting, of course. But there's some growth potential that wouldn't exist if the same basic technique were modified for the air-ionizing propulsion system which doesn't exactly cater for multi-staging or the economics of size and simplicity.
Timo Saloniemi
