So, do I win a cookie for saying it was maneuverable?
Perhaps somewhat but I remember watching one of the mini-blimps they use at football games struggle against the wind trying to fly eastward to it’s next assignment. It spent about fifteen minutes more or less over the house going more up and down than forward as it bucked a gusty headwind.
I can’t imagine solar-powered motors doing much more than a suggestion of where it wants to go.
Up in the seriously high altitude regime, say 60K feet and above, winds above about 10 knots are rather rare. So blimp-like performance might be quite valuable.
Though I’m still baffled about the idea of propulsion and a nearly-spherical shape. Those are two things that go together so badly that I have a hard time imagining it would not be better to reshape the balloon before adding propulsion.
At vessel speeds under ~20 knots air resistance is negligible, so shape doesn’t matter much.
At 60000+ feet, the air is so thin that propeller propulsion would be negligible.
From when the western allies were launching 1000s of surveillance balloons over the Soviet Union and other parties. Russian aircraft and weapon development; fascinating and just a small part of the Cold War.
One of the US balloon projects with links to others: [General Mills manufactured surveillance balloons???]
Quite. The propellers and rudder might only be there to orient the solar panels, like the tail on a windmill.
Waste not, want not, eh?
a cookie - no, … a meat-patty - yes
bear in mind that the air is way thinner up there, and hence air-resistance and drag are way lower, too…
of course the same principle applies to the propeller, which does propell in very thin air - maybe a special (thin air optimized?) design of a propeller, - one that would be too “aggressive” for sea-level air, but works (relatively) better in the 50k-100k altitude??
This is wildly off topic, but I have a breadbox, cleverly designed to hold a recipe book as well
I read that they took the debris to the FBI in Quantico. Why not a military base? Surely that would be closer?
For security, maybe yeah. But I’m skeptical the average military base has a modern forensics laboratory where the material can be examined and tested.
If they seriously think it’s a “spy balloon,” then I would expect it would go to NASIC.
(Which, BTW, is on the same base where my lab is located, and I collaborate with their lab on occasion. And that’s probably all I’m allowed to say about it. 
)
Yeesh, it seems like every day I learn there’s another federal agency. Not discounting their work, just that I’m always amazed at the size of the government.
Also, we don’t want to confuse where they took the debris first and got it inside the cocoon of US Gov’t secrecy, from where the debris ends up being analyzed in detail.
Where the electronic hardware ends up, where the balloon material ends up, and where any data captured ends up are probably 3 different labs belonging to 3 different major government agencies.
This. Plus I’ve seen a high res photo and there was no evidence of rudders or propellers. I’m leaning towards an error in reporting or being BS’ed by whomever they interviewed.
Is a sphere less area than a blimp shape for the same volume?
The only pictures I’ve seen are shredded fabric and parts of a truss.
Not to take the thread off topic but I really don’t understand why there couldn’t be a big CIA that encompasses all the different agencies - NSA, DIA, NRO, etc. all folded into one.
I also wonder if, a U-2 plane, at the right altitude, could have used a drag-net to capture the balloon, but this might have sent the plane into a stall, to put it mildly.
For a high-altitude balloon launched from ground, the pressure differential at altitude is likely to be more than the differential at ground level. There appear to be two kinds of high-altitude balloon designs:
- One uses an elastic gas envelope. At ground level, it’s approximately round (see pictures in this article), and the material (latex rubber or something with similar mechanical properties) is under approximately uniform tension all around it.
*Another uses whisper-thin plastic material, with a mesh of cables or straps across the top of it carrying the load of the cargo below (pictures in this article). At ground level, it’s a tear-drop shape: the main bulk of the helium is at the top of the envelope, and since the material is not designed to stretch elastically, there’s extra space left inside the envelope for the helium to expand as the balloon rises.
For the elastic gas envelope, when ambient pressure drop as the balloon rises, the envelope increases in size, stretching the elastic material. With greater tension in the material, the difference between interior and exterior pressure will be greater than it was at ground level.
For the whisper-thin plastic gas envelope, the shape changes from a tear drop (at ground level) to something more spherical at high altitude as the helium expands and fills the envelope more completely. As the width of the envelope increases, the straps connecting the cargo to the envelope all change their angle, resulting in greater tension in those straps and more lateral squeezing force being exerted on the envelope. This will result in greater tension on the envelope material than is seen at ground level (and so a greater pressure differential than at ground level) - but since the material is so thin, it surely can’t take on much tension.
I suspect that when you pierce an elastic gas envelope at a single point, you’re likely to create a tear that propagates across the entire envelope, same as what you get when you pop a latex party balloon. For the whisper-thin plastic gas envelope, a catastrophic tear propagating from a single point seems less likely, since there’s less tension.
In the case of the Chinese spy balloon, whatever it was made of, the shock wave and shrapnel from the missile’s continuous-rod warhead appear to have shredded the envelope rather nicely.