Oh and I forgot, those airships could be used for seeding/creating cirrus clouds to increase the planets albedo to force cooling to offset warming mechanisms.
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Oh and I forgot, those airships could be used for seeding/creating cirrus clouds to increase the planets albedo to force cooling to offset warming mechanisms.
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I thought weather manipulation was debunked, for the most part?Originally Posted by Ara Pacis
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The airship scheme is just one approach to the OP's curiosity about aviation without fossil fuels or certainly very few or much less fossil fuel. Once you are floating, (as Groucho Marx might say.....) " Now that we're safe up here!" .
' A Night in Casablanca ' .
An airship does not absolutely depend on forward velocity to maintain flight, but control is always in question, so control and forward velocity are good work for the primary propulsion system .... steam? Electric? Solar electric?
Who can say? Grasshopper
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How so?
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Looking up on it, I probably was confused. My mistake. My apologies.
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"Grasshopper". There, it was easy.
I don't see the relevance of airships. They're just another form of aircraft that has always been fossil fuel powered. They've been filled either with fossil helium or hydrogen made from fossil methane, to boot. You could power their engine with hydrogen from electrolysis, biofuel or synthetic hydrocarbons, but so what? The same is true of just about every other aircraft design.
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The lower gravitational drag allows less fuel to be used, which makes certain green fuels use plausible, including the possibility of beamed power, and the size allows for bulky powerplants such as nuclear reactors.
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That's a new concept for me. The aerodynamic drag which I'm more familiar with is greater for an airship.
I doubt it. I think an airship as fast as a plane would use more fuel.
Beamed from where? An airship wouldn't be able to go far before it was out of line of sight.
I'll let that one go through to the keeper.
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This same trade off exists today with things like the Jumbo and the A380. They COULD fill it with economy class seats. They don't. It's more profitable to fence off a chunk of it for middle/upper/business class areas. They add bars, beds, etc etc - because it improves revenue.
D
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Instead of speculating on the various effects on planes and blimps, how about some actual numbers.
The Metlife blimp (I was going to use Goodyear, but we have the added weight of the display board)...
Gets 5 MPG and holds 5 people.
That's 25 MPG per person.
The 767 uses 45 gallons/passenger from NY to London. or 77 MPG per person. (3465m/45g)
Clearly blimps are losers.
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Hi Whimsy, May I point out that an airship consumes no fuel in the action of lift. And it has many options for propulsion.
If we did not have the luxury of other fuels, the airship would be one of the possibilities for long range transoceanic travel. And mile for mile, an airship would enjoy good economy in propulsion.
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Hi Neo, The much larger and longer airship is more efficient. It has to do with "waterline length" . It's ultimate hull speed is faster for the same amount of energy. And remember the OP: Without fossil fuels. Without the energy density of petroleum (JP-5) what is a 767 going to run on?
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Hull speed only applies to vehicles operating on interfaces between two fluid layers, like surface ships. In other words, it does not apply to any kind of aircraft. Supersonic aircraft have wave drag, but it's mechanism is basically different from the mechanism for wave drag in surface ships. As for what that 767 can run on? Well, there are non-fossil fuels, like sustainably generated hydrogen or plant-sourced hydrocarbons. Gas turbines are not fussy -- they will quite cheerfully run on salad oil. My former employer had an engine in Scotland that was running on peat. Even seventy years ago, LTA were economically marginal, in that they weren't enough faster than ships (iirc, the zeppelins took about 80 hours for an Atlantic crossing; a Blue Riband liner could probably do Hamburg-New York in less than 120 hr). They were also starting to compete with aircraft -- which won on crossing time.
I don't think LTA is going to be the way.
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Care to quantify that? There are multiple assumptions, some of which are different or absent for airships versus airplanes. All things being equal, the faster speeds of airplanes will generate more drag in that manner. Aerodynamic lift will create drag that an LTA method of lift would not produce.
Care to quantify it? What size? Also, why would it be as fast as a plane?I doubt it. I think an airship as fast as a plane would use more fuel.
Have you heard of cell phones or GPS satellites? They also work on LOS.Beamed from where? An airship wouldn't be able to go far before it was out of line of sight.
Eh?I'll let that one go through to the keeper.
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Wouldn't that be 1MPG/person over a unit time?
You're not using comparables. The Metlife blimp is neither optimized for carrying passengers nor optimized for speed. I know what you're trying to get at, but air operations isn't really well suited to measuring by linear distance, but we can try. I don't know distance of the route taken by the Hindenburg, but here's the stats I got or derived from www.airships.net:The 767 uses 45 gallons/passenger from NY to London. or 77 MPG per person. (3465m/45g)
Clearly blimps are losers.
Passengers: up to 72 berths (after refit to B deck, not including 42 crewmembers)
Cruising speed: 76 mph
cruising fuel use per hour (diesel): 130kg/hr = 40.08 gal/hr = ~2 mpg
Assuming the Hindenburg took the same route as current airliners of 3458 miles @76mph (assuming no wind), then the airship would have traversed that distance in 45.5 hours, using up 1823.64 gal or about 25.33 gallons per passenger for the trip. (It's not clear if the fuel use is for the entire craft or per engine, so that estimate may quadruple.)
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Hi ARA Pacis, Many thanks for the link for airships.net. Very nice site.
Best regards,
Dan
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I appreciate the input, but I like some level of quantification. (see below)
That's what were trying to resolve, isn't it? My only comments were about the blimp comparison.
No. The "group" travelled 5 miles with one gallon. Thus 5 people have each travelled 5 miles on one gallon. 5*5
And I used the unit MPG because "distance" and "fuel used" is the goal. Not how long we stay up there.
Yes; I understand that. It's a ballpark shot to try to apply some numbers to it. Something that I haven't seen yet in the thread. And I am open to quantifiable revisions.
Such as:
Yes; that's a much more relevant example.And, the numbers are pretty close to my example.
Take away the pianos, berths, and structure for the luxury of space, I wouldn't be surprised if you could get that up to the same efficiency as the 767.
ETA: the problem is, that you probably still need the additional amenities because of the time that would be involved.
Last edited by NEOWatcher; 2012-May-25 at 12:36 PM.
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On second thought. The Hindenburg is a good example if we are proposing hydrogen lifted airships.
The capacity would be greatly diminished with helium. I don't have any numbers, but it can only be worse for the airship.
And I caught a problem with my interpretation of your example. Somehow I read the 25.33 as MPG not as GPP (gal/passenger).
116 people * 3458m / 1823.64 gal = 220MPG/passenger.I stand vastly and humbly corrected.
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The real problem is the assumption of no wind which is plainly ludicrous.
With a head wind of X mph, apparent travel distance (and subsequently also total fuel consumption) for a craft cruising at Y grows by (Y/(Y-X)).
For NY to London, a head wind of 10mph would cause a delay of 10 hours on a 76mph craft and only 6 minutes on a 560mph craft (eg. 777-800).
And will cause the slow one to use 15% more fuel while only 1.8% for the fast one.
They're basically far too dependent on weather because they're too slow.
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I agree, hence my concern for the usage of MPG as a metric. When I last took a flying lesson in a trike, the airspeed was maybe 70 knots, but because of a weather front 50 miles away and high winds at 2000 ft above ground level, we were crawling compared to the terrain. It may be less important for dense, streamlined aerodynes, but for a light aircraft or a lighter-than-air craft, it can be significant. This is why I'd like to see new airship designs that can fly faster and higher and use aerodynamic lift as well.
Last edited by Ara Pacis; 2012-May-25 at 05:42 PM.
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as you may know, the Hindenburg was designed to use He and used H when the US wouldn't sell them He. I actually think that H can be used well with the appropriate safety measures, and it's cheaper than He. According to Wikipedia: "It held 7,062,000 cubic feet (200,000 m³) of gas in 16 bags or cells with a useful lift of approximately 232,000 kilograms (510,000 lb). This provided a margin above the 215,000 kilograms (470,000 lb) average gross weight of the ship with fuel, equipment, 10,000 kilograms (22,000 lb) of mail and cargo, about 90 passengers and crew and their luggage." So, if we reduce the mass of the structure, we might dramatically increase the useful payload. Heck, just getting rid of the cargo and mail and going with people and luggage (estimating 125kg per) might add another 80 pax. Of course, you'd have to add mass for additional structure, but perhaps some of the structure could be reduced by going with a coach style seating instead of berths. It's used on train trips that last for the same duration.
I admit I'm still a little confused by your calculation above. Maybe the industry standard is to multiply, but division makes more sense to me from an operations standpoint since it helps when estimating loads and flights. And I'm still trying to wrap my head around the calculation above.And I caught a problem with my interpretation of your example. Somehow I read the 25.33 as MPG not as GPP (gal/passenger).
116 people * 3458m / 1823.64 gal = 220MPG/passenger.
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I remember the part about not being able to get the He, but I don't remember the part about the ships being designed for both. Thanks.
Probably. In fact with the scarcity of He, it might turn out to be a necessity. The GY Blimp uses 10,000 cu ft / month. I just can't visualize what a commercial fleet would do to the numbers.
We probably could make H safe, but there's still the public perception of H.
I'm not sure if "standard to" and "multiply"/"divide" really make sense in this context, at least not in what airlines do. Because the fuel usage is tied so closely to load because of the lifting resistance.
Let's say each person had to bring thier own share of the fuel on the trip.
The total fuel use would be 1823gal for the 3458 mile.
So; each person would need to bring 1823/116 gallons (~16 gallons each person).
For that 16 gallons, they get to travel the 3458 miles. 3458 miles / 16gal = ~216.
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As I recall, a study concluded that it was the painted aluminized skin on LZ-129 which may have been the culprit
which ignited the hydrogen. A better choice in Mylar perhaps?
Dan
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One among many "conclusions".
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Passenger miles/gallon and ton miles/gallon are measures of efficiency, and higher is better. An alternative would be to use something like payload/drag or speed times payload/drag (like L/D and VL/D).
Where do LTA vehicles fall vs the Gabrielli-von Karman Line?
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You'll never beat bicycles with that metric. Passenger miles per hour per gallon might be a more appropriate metric. (I interpret "gallon" as a unit of energy: not everything runs on gallons)
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You probably won't do it on coal either.
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Mythbusters demonstrated that the paint combination used (one paint with iron oxide and one with powdered aluminum) would sustain a thermite reaction if lit.
They ended up concluding that it's most likely that the paint was the reason for the visible flames, but it was still the hydrogen that was responsible for the majority of the energy of the fire.
They didn't have any conclusions on what ignited the thing in the first place.
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Being ignorant is not so much a shame, as being unwilling to learn. Benjamin Franklin
Chase after the truth like all hell and you'll free yourself, even though you never touch its coat tails. Clarence Darrow
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I didn't want to bring that into the discussion, but that demonstration was great. It was eerie how much it looked like the real disaster.
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