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New aircraft rises 'like a balloon'

bbc.com

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Re: New aircraft rises 'like a balloon'

#51

Post by ajross »

NikkiA wrote: post #31

What decides if it's an airship or not is not whether it has wings, but whether it's lighter than air. This thing is lighter than air, thus it is an airship. Yet more terrible writing by the BBC.

Uh, cite for that? Sorry, that's ridiculous pedantry. It's very reasonable to call the thing an airship, or an aeroplane (something done in the article only once, and in the context of a sourced quote justifying the distinction no less). I'm aware of no dictionaries or professional categorizations this article violates. It's a device that spans the boundary, and the article is literally about that, as the technology is (well, sorta) interesting.

Why is lack of adherence to your personal aeronautical jargon preferences a criterion for "terrible writing"? And why is this the top comment in the topic? Come on folks.

Re: New aircraft rises 'like a balloon'

#52

Post by evgen »

cr0sh wrote: post #33
gnode wrote: post #23

Earlier quoted context omitted.

> 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.

I'd argue that hydrogen is actually among the best, with helium of course being second. Helium wins out on the inertness, but has far lower lifting capacity, and of course has a supply issue. Hydrogen wins on lifting capacity, supply is not an issue at all - but it has a weird image problem, thanks to one singular accident - which was arguably not caused by the lifting gas! Prior to that accident, hydrogen had a fair…

The other problem with hydrogen is that it is hard to contain. Leakage and permeability of the envelope would probably end up being a bigger engineering concern than would flammability.

Re: New aircraft rises 'like a balloon'

#53

Post by evgen »

sarbaz wrote: post #46

This is exactly how submarines work

Submarines use a prop for forward motion and are almost never 'gliding' using their planes. The purpose of the wings on this craft are similar to the variable-buoancy underwater drones that are out there, when the craft is rising the wings are trimmed to cause forward motion and then when it is descending they are trimmed in the other direction to continue forward motion.

Re: New aircraft rises 'like a balloon'

#54

Post by i_am_proteus »

lordnacho wrote: post #47
NikkiA wrote: post #31

What decides if it's an airship or not is not whether it has wings, but whether it's lighter than air. This thing is lighter than air, thus it is an airship. Yet more terrible writing by the BBC.

Sounds like it's an air submarine. The description of the variable buoyancy sounds pretty much like what a submarine does.

This is not really accurate. Submarines maintain roughly neutral buoyancy and use a motor for propulsion. They can use lifting surfaces for buoyancy control, but they need the motor to move forward. Airships operate on essentially the same principle--- airships are closer to "air submarines" than "air ships."

This device is an air-equivalent of an underwater glider.[0]* It establishes positive buoyancy to rise through the fluid (air, in this case, rather than water) and then establishes negative buoyancy to enter a dive, after which it glides just like any other glider.

The difference between this thing and a 'normal' glider is that it uses buoyancy to rise in altitude rather than needing to be towed by a conventional airplane.

[0]https://en.wikipedia.org/wiki/Underwater_glider * An underwater glider being the water equivalent of a... glider.

Re: New aircraft rises 'like a balloon'

#55

Post by PhasmaFelis »

PeterisP wrote: post #48
MagicPropmaker wrote: post #45

Earlier quoted context omitted.

It's both heavier and lighter! There's a compressor that can bring air in from the outside and make it heavier than air, and then this air can be released making it lighter again. This is explained in the article. It really is something new.

Like a hot air balloon which becomes heavier than air or lighter than air by regulating temperature in order to ascend or descend? That's fancy tech as of year 1800.

As long as we're nitpicking terminology, hot air balloons aren't airships either, they're aerostats. And they certainly don't use their variable bouyancy to propel themselves in directed flight. Saying this thing is just a hot air balloon is like saying an airplane is just a glider.

Re: New aircraft rises 'like a balloon'

#56

Post by therein »

ZeroGravitas wrote: post #22
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

Just out of curiosity, do you have any relation to the Remarkable Tablet?

Re: New aircraft rises 'like a balloon'

#57

Post by logfromblammo »

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.

Make a vacuum onion.

1d-compressium, 1d-tensilium, and 2d-tensilium are all allotropes of obtainium, being the materials with the highest uniaxial compressive strength to mass ratio, the highest uniaxial tensile strength to mass ratio, and the highest biaxial tensile/shear strength to mass ratio. Currently, those are probably diamond struts, buckytube fiber cables, and graphene sheets.

Throw 2d-tensilium envelope around a tensegrity frame with 1d-compressium struts and 1d-tensilium cables. Pump out the interior gas until it breaches or collapses.

Start over. This time, put another frame and envelope around the first, and anchor them to each other with more 1d-tensilium cables. Pump out the interior gas of both pockets until the outer shell breaches or collapses.

Repeat, until the pressure differential on every envelope and shell is insufficient to breach the envelope or buckle the frame. Now you have a gradient from vacuum to atmospheric pressure instead of a perfect vacuum in the whole volume, but you don't have to find any unobtainium to build it.

As a bonus, you can put the envelope on the inside of the shells, and follow a similar process of breaking each one with air, to make an inflatable spacecraft hull that can hold 1 atm of breathing gas on the inside without rupturing in vacuum, using minimal mass.

Re: New aircraft rises 'like a balloon'

#58

Post by lnanek2 »

logfromblammo wrote: post #57
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.

Make a vacuum onion. 1d-compressium, 1d-tensilium, and 2d-tensilium are all allotropes of obtainium, being the materials with the highest uniaxial compressive strength to mass ratio, the highest uniaxial tensile strength to mass ratio, and the highest biaxial tensile/shear strength to mass ratio. Currently, those are probably diamond struts, buckytube fiber cables, and graphene sheets. Throw 2d-tensilium envelope aro…

Wouldn't all that inner material be too heavy to float after that?

Re: New aircraft rises 'like a balloon'

#59

Post by TimTheTinker »

jacobush wrote: post #7
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…

If helium gets really expensive, they could switch to hydrogen. Maybe even switch inflight, by replenishing lost helium with hydrogen. Maybe by hydrolysis. For a plane operating in remote areas at altitude, the explosion risk is not an issue.

You could switch in-flight, but you would actually increase the gas costs since you’d need 100% helium for the trip up as well as the trip down. Also, the risks would dramatically increase in exigent circumstances. What if the gas container fails, causing it to make an unexpected descent? Even for a planned descent, there has to be a way to switch back to helium.

So now you have to have at least 2 times the helium needed to attain buoyancy, plus mechanisms to generate hydrogen and vent/replace gas. And systems/procedures to handle edge cases.

It sounds like a lot of complexity and cost added. However, it might be worth it if extremely high altitude is needed. The altitude ceiling could be increased significantly (not sure how much, but <2x) for a given configuration and payload.

Re: New aircraft rises 'like a balloon'

#60

Post by Schweigi »

TheLoneAdmin wrote: post #32
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.

Apparently the craft is powered entirely by solar power, plus batteries, to work at night. A solar powered craft cannot maintain 130 knots.

The cool thing about this craft is that it’s a glider and doesn’t use solar power for direct propulsion. Instead it uses the solar power to make the ballon lighter than air. Once it reaches altitude it will start gliding by making the ballon heavier than air. While gliding it can reach very fast speeds. The question is though how many times it needs to refill the ballon during the night and if the stored power is enough.
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