Comments on: Even SpaceX looks like small potatoes next to an industry like global logistics

By: T. Beholder

T. Beholder — Fri, 01 Nov 2024 04:01:09 +0000

John Smith says, “both of those methods are horribly impractical and the first one negates any reason for an airship.”

It does not. WIG plane must briefly use a liftoff engine group (much like VTOL), but when cruising is more fuel-efficient than a basic cargo plane.

Likewise, a lighter-than-air craft sometimes using one more engine is still much more economical than a helicopter. And if those are merely for maneuvering, rather than keeping the whole thing in the air, they are going to be much weaker than needed for helicopter style lift. This usually allows greater fuel efficiency or other perks.

Besides, vertical thrust can be converted or redirected to propulsion, then it’s not a waste of mass while cruising. Could be done via Osprey style turning pods or turbofans with several exhaust ports.

As to the lifting gas, it’s more fitting for slower long-term buoyancy adjustments.

What matters is the total balloon volume, usually tweaked via pressure. If you pump it into a cistern (or even into stronger inner cells) or heat/cool it, this will change pressure in the balloon without losing any gas. Though losing (and producing) gas is a viable option, sin ce cargo and other applications of “load at point A, unload at point B” sort require only modest endurance. Exotic extra-long missions would require a very specialized vehicle either way.

By: Jim

Jim — Thu, 31 Oct 2024 17:14:29 +0000

Incidentally, airliners fly so high—thirty to forty thousand feet—because the air is so much thinner, reducing parasitic drag very considerably and greatly reducing turbojet specific fuel consumption. Since airships travel so slowly by comparison, aerodynamic drag is hardly a consideration, so there is rarely any compelling reason to go more than a few thousand feet in the air.

By: Jim

Jim — Thu, 31 Oct 2024 17:07:28 +0000

Like submarines, airships shoot for neutral buoyancy. Then thrust is generated with propellers or, conceivably, turbines, and directed opposite the desired direction of travel, whereupon the airship trundles lazily forth.

By: John Smith

John Smith — Thu, 31 Oct 2024 04:01:33 +0000

Could someone please explain to me how a heavy lift airship goes up and down without either

1. using helicopter type lift mechanisms
or
2. releasing precious lift gas

because both of those methods are horribly impractical and the first one negates any reason for an airship.

By: Phileas Frogg

Phileas Frogg — Thu, 24 Oct 2024 13:13:27 +0000

THAT is interesting. So instead of, “airship-ifying,” the plane, they, “plane-ify,” the airship.

By: Isegoria

Isegoria — Wed, 23 Oct 2024 17:17:39 +0000

A hybrid has been proposed:

Fully buoyant airships, as they slow down to land, behave more and more like soap bubbles, at the mercy of the wind. One way to side-step this problem is to make the ship heavier. A "hybrid" airship obtains just 80 percent of its lift from helium and the remainder from dynamic lift, like an airplane

By: Phileas Frogg

Phileas Frogg — Wed, 23 Oct 2024 15:22:41 +0000

So my takeaway is that Planes simply have a different operating principle that makes any sort of hybridization between Airships and Planes, with regard to their mechanism to achieve lift, redundant at best or inhibitive at worst.

I appreciate the responses gentlemen.

By: Gaikokumaniakku

Gaikokumaniakku — Wed, 23 Oct 2024 05:42:55 +0000

In a world with very cheap resources, we could start by building 500-meter-long dirigibles and then getting them airborne with vast quantities of helium, after which we might decide that the aerodynamics still sucked. But without huge budgets, one could not even start to make painful mistakes. Airships are so alluring in part because the high barriers to entry give impractical dreamers an excuse to never get started.

By: Isegoria

Isegoria — Wed, 23 Oct 2024 01:35:27 +0000

An airplane does not have much volume for its weight, and the trick to making an airship work, as the article suggests, is to increase that ratio by going big, because doubling the size of an airship might quadruple its surface area, and thus its weight, while multiplying its volume by a factor of eight. Small containers of helium might weigh more than the lift provided.

And a bulbous aircraft with more volume would have more drag.

A cubic meter of helium can lift about a kilogram. So, a 10 m x 10 m x 10 m cube of helium could lift one ton. A 747 weighs 400 tons.

By: Jim

Jim — Tue, 22 Oct 2024 18:13:10 +0000

Phileas: “Could you theoretically flood closed off interior components of airplanes with lighter than air gases to get better lift/fuel efficiency?”

There isn’t much unfilled interior space in an airplane. That’s why airships hang below gigantic balloons. And even then, how would you contain the gases?