Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

New aircraft rises 'like a balloon'

bbc.com

Post reply on HN
Print view View original

21–30 of 75 posts

Re: New aircraft rises 'like a balloon'

#21

Post by astazangasta »

lawlessone wrote: post #16
davnicwil wrote: post #11

Earlier quoted context omitted.

Excuse the silly question if it is one, but would one option be not a full vacuum but only marginally lower density of air inside the balloon, supplemented by solar-powered propellers? Could there be a material strong enough to handle a minimal density difference to provide enough lift for it to work?

To add to your Idea, could a "null ship" be carried to a greater height and then where the air is thinner have it's gas removed to take everything a little higher? Like rocket stages but for airships.

At a greater height you need a larger airship to provide the same lift. As you move towards the vacuum of space and the differential becomes less the lift per unit volume is less.

Re: New aircraft rises 'like a balloon'

#22

Post by ZeroGravitas »

neom wrote: post #4

For those curious, University of the Highlands and Islands is in Inverness, Scotland. Quite a bit north of Edinburgh and Glasgow.

That's the main campus but part of the concept is for it to be distributed over most of the Northern part of the country, including, as the name suggests, the islands:

https://www.uhi.ac.uk/en/#campuses

Re: New aircraft rises 'like a balloon'

#23

Post by gnode »

astazangasta wrote: post #6
hirundo wrote: post #5

With the soaring price of helium, I wonder what it costs to fill up that gas bag and how quickly it leaks out. And at what point filling it up costs more than the "almost expendable" aircraft. In the novel/film Contact the character S.R. Hadden lives in an airliner that rarely lands. With a larger Phoenix that lifestyle could become available to somewhat less wealthy billionaires. Maybe it could eventually become an…

There are no really great lifting gases. Steam is ok but must be kept hot. H2 is dangerously explosive. Vacuum is the best (a so-called "null ship") but no known material can maintain the hull pressure under vacuum.

> H2 is dangerously explosive.

Does it matter for an unmanned vehicle? Such a thing could be inflated at a safe distance. In some cases, being able to self destruct is a safety benefit (to prevent crashes when control is lost) and a security benefit (to prevent analysis of captured aircraft). Particularly UAVs are popular in military / spying operations.

Re: New aircraft rises 'like a balloon'

#24

Post by jeffreyrogers »

davnicwil wrote: post #11
astazangasta wrote: post #6

Earlier quoted context omitted.

There are no really great lifting gases. Steam is ok but must be kept hot. H2 is dangerously explosive. Vacuum is the best (a so-called "null ship") but no known material can maintain the hull pressure under vacuum.

Excuse the silly question if it is one, but would one option be not a full vacuum but only marginally lower density of air inside the balloon, supplemented by solar-powered propellers? Could there be a material strong enough to handle a minimal density difference to provide enough lift for it to work?

Any structure strong enough to withstand the pressure from outside the vacuum weighs too much to be lifted. At least that's what I read in some aerodynamics book. Maybe some materials scientist will come along and prove that wrong.

Re: New aircraft rises 'like a balloon'

#25

Post by Rerarom »

astazangasta wrote: post #6
hirundo wrote: post #5

With the soaring price of helium, I wonder what it costs to fill up that gas bag and how quickly it leaks out. And at what point filling it up costs more than the "almost expendable" aircraft. In the novel/film Contact the character S.R. Hadden lives in an airliner that rarely lands. With a larger Phoenix that lifestyle could become available to somewhat less wealthy billionaires. Maybe it could eventually become an…

There are no really great lifting gases. Steam is ok but must be kept hot. H2 is dangerously explosive. Vacuum is the best (a so-called "null ship") but no known material can maintain the hull pressure under vacuum.

What about helium?

Re: New aircraft rises 'like a balloon'

#26

Post by beamatronic »

jeffreyrogers wrote: post #24
davnicwil wrote: post #11

Earlier quoted context omitted.

Excuse the silly question if it is one, but would one option be not a full vacuum but only marginally lower density of air inside the balloon, supplemented by solar-powered propellers? Could there be a material strong enough to handle a minimal density difference to provide enough lift for it to work?

Any structure strong enough to withstand the pressure from outside the vacuum weighs too much to be lifted. At least that's what I read in some aerodynamics book. Maybe some materials scientist will come along and prove that wrong.

Can we make many small ones instead of one big one?

Re: New aircraft rises 'like a balloon'

#27

Post by shkkmo »

beamatronic wrote: post #26
jeffreyrogers wrote: post #24

Earlier quoted context omitted.

Any structure strong enough to withstand the pressure from outside the vacuum weighs too much to be lifted. At least that's what I read in some aerodynamics book. Maybe some materials scientist will come along and prove that wrong.

Can we make many small ones instead of one big one?

As volumes decrease in size, the ratio of surface to volume increases, make weight a bigger issue with smaller envelopes (given that surface thickness would not be able to decrease proportionally).

Re: New aircraft rises 'like a balloon'

#28

Post by hirundo »

kevinmchugh wrote: post #19
hirundo wrote: post #5

With the soaring price of helium, I wonder what it costs to fill up that gas bag and how quickly it leaks out. And at what point filling it up costs more than the "almost expendable" aircraft. In the novel/film Contact the character S.R. Hadden lives in an airliner that rarely lands. With a larger Phoenix that lifestyle could become available to somewhat less wealthy billionaires. Maybe it could eventually become an…

I believe Hadden lives on a space station in both movie and book.

First a plane, then he moves up to Mir: https://scifi.stackexchange.com/questions/124894/in-movie-co...

Re: New aircraft rises 'like a balloon'

#29

Post by ChuckMcM »

sandworm101 wrote: post #17

Most of the mentioned use cases involve high altitudes. Higher altitudes = higher winds. The air is smooth up there but it does move. For instance, the upper level winds above my head right now are pushing 130knots. This thing will have to do more than glide gently up and down if it wants to maintain station at 10km+, airliner altitude.

Yup, that has been the Achille's heel of these types of vehicles. One work around is to have a bunch of vehicles and have them move to altitude, stay over the area of interest as long as possible and then change to a lower altitude without the winds to move back to the head of the line.

Re: New aircraft rises 'like a balloon'

#30

Post by gnode »

Rerarom wrote: post #25
astazangasta wrote: post #6

Earlier quoted context omitted.

There are no really great lifting gases. Steam is ok but must be kept hot. H2 is dangerously explosive. Vacuum is the best (a so-called "null ship") but no known material can maintain the hull pressure under vacuum.

What about helium?

Helium is expensive and practically non-renewable on Earth. It forms slowly by beta decay, with most of it escaping into space (because it's molecular mass is so low, its velocity commonly exceeds Earth's escape velocity). A small amount gets trapped in deposits which we can extract.
Post reply on HN