Could They Ever Return?

[Nelson]

Since airships have a huge surface area why not cover the outer surface with solar panels and use the power to drive the props?

I wonder...

His Majesty's Canadian Airship CR.3 "Alexander Mackenzie" was designed to provide transportation of large cargoes to communities north of the Arctic Circle. Roughly the same size as HMA R505 Flying Cloud, her solar panels take advantage of the "midnight sun" in the arctic summers, and avoid difficulties with diesel fuel in low temperatures. Her design is simplified into three simple shapes to simplify my math. Er, I mean, to simplify construction! yeah. This gives her a somewhat more bulbous appearance than her counterpart, but slightly more surface area for solar panels, and more volume for lift.

Length/Diameter: 560 ft / 105 ft

Profile:
hemisphere 52.5 ft rad, 2D profile of 4330 sq.ft
cylinder 317.5 ft long, 2D profile 33337 sq.ft
cone 190 ft long, 2D profile 9975 sq.ft
(let's ignore putting solar panels on the fins for now)
TOTAL 2D PROFILE: 47642 sq.ft

Commercial solar panels are producing around 12 watts per square foot, that gives us about 572 kW of power, equivalent to around 767 horsepower. Really good panels will crank out 15 W/sq.ft, for 715 kW = 958 HP. That's roughly equivalent to ONE of the Flying Cloud's three engines.

The HMCA Mackenzie, underpowered, was wrecked during a landing attempt in fierce northern winds at Yellowknife in June, 1929...

[Nelson]

Crud. I had a really good post going about doing the math again on a real airship, the R.80, but it timed out.

So here we go again! Cover the R.80 in solar panels. The envelope is covered top to bottom (so you get as much power if the sun is abeam as if it was overhead), the vertical fins both sides, the horizontal fins on the top. I modeled a ship 535 ft long, 70 ft in diameter, and just over 1.2 million cu.ft volume, so it's pretty darn close in shape to the R.80. The original was powered by four 230 HP engines, had a disposable lift of 14.8 short tons, and could do 70 mph (61 kts).

With heavy modern bolt-to-the-roof-of-your-house solar panels 15 W/sq.ft, I get 367 kW of electricity. Tokai University made an electric motor last year with 96% efficiency, let's pretend we've got big versions of that. 352 kW from the motor = 472 HP, or 51% of the original ship's power. Drag increases with the square of the speed, they say, so I'm guessing 51% of the power means 71% of the speed, or 50 mph (44 kts). That would be pretty useful, actually, except it'd be way too heavy.

But more realistic: I found one brand of flexible solar panel that provides 3 W/sq.ft. That gives me 73 kW of electricity, 70 kW = 94 HP at the prop, 10.2% of the original ship's power, 32% the speed, for 22 mph (19 kts). That's just not enough to keep up with any kind of wind. These light and flexible panels still weigh so much (3.3 oz/sq.ft) that the solar powered R.80 has enough disposable lift for a crew of 14 men, a 1973 VW Beetle, and a light lunch for everybody aboard. And no batteries, so a cloud means adrift.

I tried to make it work, I really did! But I don't think it does.

[RbSned]

So the numbers dont add up, pity.

Perhaps the answer lies with hybrid type craft like this thing DARPA was considering a couple of years ago
http://www.youtube.com/watch?v=S-M97AJtems
Seems to me that it might have had commercial applications as well as military.

[Kona]

I’ve speculated for some time that, absent the spectacular Hindenburg accident, airships might have continued to develop alongside fixed-wing aircraft, improving in safety as well as speed, range and payload, making for a much different air traffic population than we now have. Wikipedia seems to agree: “The accident served to shatter public confidence in the giant, passenger-carrying rigid airship, and marked the end of the airship era.”

As it is, a new generation of airships would have to play catchup to nearly a century of heavier-than-air craft development.

[RbSned]

You often see comments like that all over the place concerning the Hindenburg and airships in general but its only partly true.
Firstly, the Hindenburg was not the last of the big airships, the Germans built one more, the LZ-130 Graf Zeppelein II though she never went in to passenger service.
The nazi`s used her as a flying advert for the party then later she was used as a sort of early EW survailance platform to probe for radar developments in other countries.
Both her, and her original namesake were broken up early in WWII on the orders of Hermann Goring.
Secondly, airship development didn`t stop there, small airships continued to be developed and buit, finding roles as anti submarine aircraft during WWII then as EW platforms and for airbourne advertising in the post war period.
So airship development continued, and is still continuing with the new Zeppelein NT series.

[Nelson]

Also, why are you assuming a modern airship would be restricted to a ceiling of 6000 ft?

If there's a modern gas-tight fabric that can stand the pressure without weighing any more, then I guess you could go up until the air thinned out so much it doesn't weigh much more than your lift gas at sea level (or 6000 ft, or whatever you build it to).

Or maybe when climbing above a certain altitude, you could keep the lift gas at ambient pressure, and compress the extra lift gas back into tanks to use again when you descend. Come to think of it, a system like that would also mean you wouldn't have to vent gas or drop ballast for gentle planned maneuvers, just for quick actions during takeoff, landing and emergencies. How fast did an airship vent gas? How heavy would a pump capable of compressing gas that quickly, and suitable storage tanks, weigh?

Staying below 6,000 ft would help keep airships separated from the high-flyers and the turbulence they create (there may need to be special lighter-than-air corridors in busy airspace. You do not want an airship crossing through air disturbed by a 757 just minutes earlier, and the 757 absolutely can not slow down to stay behind the airship). The airplane's advantage at high altitudes is less drag in the thinner air, and reducing drag would be even better for airships, but the airship will have trouble dealing with the winds up there. OTOH, in the summer time, 5,000 ft can behave like 9,000...

[RbSned]

Or how about going ABOVE existing air traffic, with this sort of technology under development it might just be possible, giving access to a whole region of the atmosphere that can currently only be reached by high altitude balloons or passed through briefly by spacecraft.
http://www.lockheedmartin.com/products/HighAltitudeAirship/index.html
They have a nice promotional video as well,
http://www.youtube.com/watch?v=_DgCvfxLCoY

[Nelson]

Above existing air traffic could get pretty scary, pretty quick. As an example, here's what you'd deal with climbing out of Vancouver, BC (YVR/CYVR) this hour:

• Surface: 170 at 13 kts, temp +8C
• 3,000: 220 at 27 kts
• 6,000: 230 at 33 kts, -1C
• 9,000: 240 at 40 kts, -5C
• 9,700: ---- Cloud ceiling ----
• 12,000: 240 at 46 kts, -10C
• 13,500: PIREP - at 1920z, a Beech Super King Air, 30 N of YVR, reported moderate mixed icing from 12,500 to 13,500.
• 18,000: 230 at 72 kts, -22C
• FL240: 230 at 110 kts, -30C
• FL300: 220 at 103 kts, -47C
• FL340: 230 at 132 kts, -58C
• FL370: URGENT PIREP - at 1942z, a 747-400, 5 E of YVR, reported moderate to severe turbulence.
• FL390: 230 at 91 kts, -60C
• FL450: 240 at 56 kts, -52C
• FL530: 260 at 33 kts, -54C

It's not like that every day (the jetstream is zig-zagging across southern BC today), but days like this happen all over the place.

[PaulGazis]

Or maybe when climbing above a certain altitude, you could keep the lift gas at ambient pressure, and compress the extra lift gas back into tanks to use again when you descend. Come to think of it, a system like that would also mean you wouldn't have to vent gas or drop ballast for gentle planned maneuvers, just for quick actions during takeoff, landing and emergencies.

The problem with such a system, or with having pressurized cells, is that the gas is still aboard the ship, so it still adds weight. After one runs through all the thermodynamics equations (P=nkT), one ends up with exactly the same altitude limitations one would have if one just vented the gas away. Of course, a pressurized system would allow one to conserve ballast -- an important operational consideration, as everyone has noted! From a materials and engineering standpoint, Everett's world doesn't have the necessary technology in 1926. In our world, with kevlar, carbon fiber, and advanced composites... I wonder...

I most certainly agree with you about air traffic getting bizarre at times. I've had some interesting experiences flying hang gliders. Such as climbing through 17,500' while watching a B-1 on approach to Castle AFB fly underneath me, a mile or so below. I was still going up at 1000 FPM, but we didn't have a wave window, so I left the thermal to make sure I stayed below the flight levels. Oddly enough, it was quite warm that day. I was only wearing two sweatshirts, since I didn't expect to get much above 10,000', but that extra 1.4 miles of altitude (!!!) didn't seem to make much difference. Fleming would have loved it!

[RobertPlamondon]

As mentioned before, the "flying cruise ship" model is the most palatable. The HINDENBURG often flew with the observation windows open, and it flew low enough (around 1,000 feet) that you could hear the sounds of the countryside. Also, its propellers and engines were so far from the gondola that the engines could not be heard in flight at all.

I think people would be delighted to shell out big bucks for a leisurely air tour of, for example, Europe's castles, followed the next day by a tour of Egypt's monuments, including passing between the Great Pyramids at low altitude!

And not having to go through customs at every border (because you don't land) could be a big plus. Tour 15 countries without having your luggage rummaged once!

A "tin blimp" design would be simpler and lower-maintenance than a conventional airship. Crew requirements are probably much lower as well, with modern technology.

As for the weather, there is no comparison between today's weather forecasting and that which allowed the AKRON and SHENANDOAH to fly all unknowing to their doom.

Robert