Comment Re:Diesel Engine for Power. Where's the oxygen? (Score 1) 176
That's the least of their problems! Come on, the air is thin to be sure, but it's hardly vacuum. About one seventh or so sea level density, compressing that is not a problem. It costs something but not a whole lot. The temperature of the compressed air would be 170 Fahrenheit or so.
The thinness of the air reduces the strength of a given wind too. Divide whatever speed you are looking at 20 kilometers up by 2.7 or so to get a sea level speed of equivalent strength. That's how they can seriously propose to keep station in normal stratospheric winds. As for jet streams--obviously they have to dodge them. Fortunately jet streams are relatively thin , maybe a hundred miles across at most--that's why they are called "streams" and not sheets or just winds. Unfortunately they move around--but only within a typical range. A "geosynchronous" station outside that range should be feasible. Having the thing weave and dodge and circle around in the winds would not be geosynchronous but it might work all right for service delivery over windiier areas--like Canada.
The article is ambiguous which craft is supposed to stay up a month without refueling; I guess the 40-meter one which is the next one on the drawing board. Obviously if it is going to keep station even a week, the diesel engine is for initial positioning and it supplements the solar/stored power after that, not the other way around.
You shouldn't underestimate the endurance of an airship though. The US Navy operated blimps in the 1950's (manned) that operated for days without refueling; during Operation Whole Gale one stayed on station 90 hours during the worst storms of a record winter, off shore of New England. Because they keep such modest airspeeds, even with the mediocre streamlining of a plain sphere the power requirements are much much lower than an airplane.
What has been throwing a lot of people who really are into lighter-than-air aviation is the claim Sanswire has been making, that the hull of these ships are (or are going to be?) made of Kevlar. Kevlar is hard to fashion into a lifting-gas fabric, and when Sanswire claims in such an offhanded way to be doing it already it sounds like a scam to them-or at best completely irresponisible extrapolation.
The thinness of the air reduces the strength of a given wind too. Divide whatever speed you are looking at 20 kilometers up by 2.7 or so to get a sea level speed of equivalent strength. That's how they can seriously propose to keep station in normal stratospheric winds. As for jet streams--obviously they have to dodge them. Fortunately jet streams are relatively thin , maybe a hundred miles across at most--that's why they are called "streams" and not sheets or just winds. Unfortunately they move around--but only within a typical range. A "geosynchronous" station outside that range should be feasible. Having the thing weave and dodge and circle around in the winds would not be geosynchronous but it might work all right for service delivery over windiier areas--like Canada.
The article is ambiguous which craft is supposed to stay up a month without refueling; I guess the 40-meter one which is the next one on the drawing board. Obviously if it is going to keep station even a week, the diesel engine is for initial positioning and it supplements the solar/stored power after that, not the other way around.
You shouldn't underestimate the endurance of an airship though. The US Navy operated blimps in the 1950's (manned) that operated for days without refueling; during Operation Whole Gale one stayed on station 90 hours during the worst storms of a record winter, off shore of New England. Because they keep such modest airspeeds, even with the mediocre streamlining of a plain sphere the power requirements are much much lower than an airplane.
What has been throwing a lot of people who really are into lighter-than-air aviation is the claim Sanswire has been making, that the hull of these ships are (or are going to be?) made of Kevlar. Kevlar is hard to fashion into a lifting-gas fabric, and when Sanswire claims in such an offhanded way to be doing it already it sounds like a scam to them-or at best completely irresponisible extrapolation.
