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.
New aircraft rises 'like a balloon'
31–40 of 75 posts
Re: New aircraft rises 'like a balloon'
#32Most 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.
Re: New aircraft rises 'like a balloon'
#33Earlier 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.
> 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 fairly great record with airships, and it was used extensively for ballooning as well without many incidents.
Hydrogen by itself isn't flammable - you need another particular gas involved for that to be an issue. You also need a source of ignition.
Re: New aircraft rises 'like a balloon'
#34Most 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.
Go higher. If you search for "high altitude wind" you'll get info from 20,000 feet, which is not at all the same as 20,000 meters. Past a point, the thinning atmosphere actually means less coupling and wind speed decreases. You'll note that tiny quote halfway through about it being difficult to get up to the required altitude of 20km. That's because the average wind speed bottoms out around 5 meters per second at an altitude between 20km and 25km [1]. Add in the thinning air reducing drag and, yeah, a solar-powered balloon can absolutely stationkeep at that altitude. Here's a wiki page with more links: https://en.wikipedia.org/wiki/Geostationary_balloon_satellit...
[1] https://www.researchgate.net/figure/Average-wind-speed-in-th...
Re: New aircraft rises 'like a balloon'
#35Earlier 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?
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Re: New aircraft rises 'like a balloon'
#36I'd love a fleet of small lighter than air balloons for city coasting
Re: New aircraft rises 'like a balloon'
#37What 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.
I might be misunderstanding things but it sounds like the "breathing" (compressing atmospheric air) gives it variable density? I guess it makes it a sometimes-an-airship.
Re: New aircraft rises 'like a balloon'
#38Most 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.
Solar impulse 2 used 269.5 m2 of solar panels to produce 66 kW peak and do 75 knots.
That’s only ~1/2 the current max efficiency of solar panels. Suggesting many other improvements are at least possible and 130 knots are within reach if that’s what was being optimized for vs say cost.
Re: New aircraft rises 'like a balloon'
#39With 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.
That is an interesting idea, and I don’t know why this has been downvoted.
Re: New aircraft rises 'like a balloon'
#40Earlier 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.
I don't think the possibility can be entirely discounted. Consider composite materials, a honeycomb. Much more difficult to analyze than a sphere of steel