If planes, with active propellers or jet engines, are only audible for a diameter of 20-50km around the vehicle, how could a falling unpowered ring of metal be audible from 200km away as per TFA?
I'm nearly certain it's irrelevant but it does make me wonder where parts of the rockets used to launch the ballistic missiles that were recently put into hostile action would have landed.
Somewhere in between the launcher and the target. Ballistic missiles fly a near-parabolic sub-orbital trajectory. That also means that everything on the missile reenters and crashes (or reaches the target) within minutes of the launch. This is a matter or energy management. If your payload (the warhead) is going to land somewhere on Earth, why waste energy in flinging it on a high-velocity (possibly orbital) trajectory when that energy could be used to loft more of the payload (a heavier warhead) directly at the target?
There are a few cases where this concept of lowest-energy trajectory is not followed. One of them is a lofted-trajectory launch. The missile flies a higher ballistic trajectory than what's necessary to reach the target. This is sometimes used for missile tests or for target ranges less than the missile's maximum range. However, this is also a sub-orbital trajectory and behaves more or less the same as before.
Another case is the Fractional Orbital Bombardment System (FOBS) where the warhead enters a low orbit and then deorbits towards the target. Space debris situations like in this story (where the rocket body lands well away from the target, long after the launch) can possibly occur in FOBS launches. However, this isn't very energy efficient. It's main advantage is that it's harder to detect and intercept, since its orbital trajectory is much lower than a pure ballistic trajectory. Even then, some countries can knock them out in orbit using ASAT (anti-sat) detectors and interceptors. It's not that commonly used, except in combination with other technologies like hypersonic gliding and waveriding.
It's fairly niche here, but I would like to note that lofting can be more efficient than either a purely direct or ballistic trajectory -- one only needs consider the case of going higher in the atmosphere so as to have less air drag at extremely high velocities.
Can mean a higher speed, acceleration, and a longer range for the same payload.
In a sense, this is actually done with high velocity rocketry in general. Often most launch profiles involve a steep ascent before smoothing it out into a softer turn.
The charts showing the growth of the number of objects in orbit in recent years are wild. I have to expect this will be a lot more common going forward.
How many people will have to be fatally injured before international laws put seriously painful financial fines on companies dropping crap from space? Or will my fantasy come true that all roads, infrastructure, homes and businesses move underground?
Jonathan is very knowledgeable and is usually right. But in this specific instance, everything points out that this is indeed a component of a rocket.
The eyewitnesses describe that the object fell with a high velocity, with a loud noise, and was hot when it landed.
The better angles in the video [1] show molten metal on the outside, and a typical aerospace bolt pattern with carefully machined pockets around the bolts.
This kind of construction is typical in rockets, for example at the top and the bottom flanges of some stages of the Indian PSLV rocket [2]
There are lots of videos of similar Thai fireworks, but I think is the largest one I've seen. Also, based on my amateur rocketry experience, this is completely feasible, if rather dangerous. 99% sure it is a real video.
I'm not sure why it makes the 'chuffing' noise though. Anyone know?
I agree with Jonathan. It seems to be a very low-tech, solid steel ring gear assembled and riveted together from 4 distinct parts. Not very aero-spacey at all...
Approximately 8' diameter (other commenters pointed out a more reasonable size) solid steel ring gear (riveted together from 4 parts). Doesn't look anything like a "separation ring", and certainly isn't large enough. Plus it is solid steel. I am kinda doubting the whole story at this point. No way it is from a rocket (too heavy, too low-tech, no ring gears in rocketry), and doubtful from any commercial aircraft (again, too low-tech and too heavy).
I design and build all sorts of hardware relating to air-breathing (jet) propulsion, including gears. I agree with mkl. Those are not gear teeth. They have flat flanks, and no involute profile. No one makes gears with a gigantic U shaped root. They appear to me to most likely be clearance slots, to go around protruding bolt heads on a mating part. I have designed similar counterbore features myself.
What makes you claim that this part is steel? The article does not say that. Is that a fact, or are you guessing?
The appearance of rust on the surface of the article's main photo suggests steel. I guess heat from reentry may lead to that appearance on other materials?
Inconel looks just like that after exposure to heat, and is much more likely to have been used to build an aerospace vehicle than carbon steel. Most jet aircraft exhaust systems are made of Inconel and oxidize to a dull brown at 1200F or so. Like on this 737NG:
The exhausts that turn iridescent purple for a while due to heat are titanium, for example this 787. So I would suspect the debris is not titanium based on lack of heat marking.
So if I were to guess what kind of metal it was solely based on coloration and suspected use case, I’d say Inconel.
But I wouldn’t make a guess at all, because it’s naive to assume that you can identify a type of metal based on a grainy freeze-frame of a cell phone video that has been re-encoded an unknown number of times before publication.
An earlier article [1] linked in this one says about 1.2m radius, so ~2.4m or ~8ft diameter. At 48 seconds in the video there's a man standing next to the propped up side and it comes up to his chest, so that seems believable (the other side is down a slope).
It seems surprising it weighs 500kg though, as it's held up by a thin iron/steel pipe/bar. If it's solid mild steel at 7850kg/m^3, with an outer radius of 1.2m and inner radius of 1.05m, and a thickness of 4cm, that would be (π*1.2^2 - π*1.05^2)*.04*7850 ≈ 333kg. If the inner radius is 1.0m and thickness is 5cm, that would be ~543kg, so maybe it is that heavy.
Edit: The tooth profile looks strange for a gear. There's a clear but potato-resolution view at 36s in the video. The teeth have flat tops with sharp corners, the sides are pretty vertical, and the gaps have very rounded bottoms.
Lots of rocket components look like gears. The outside skin of the rocket often had internal vertical stringers and so components need cutouts that end up looking a bit like gears
The rust does stand out as kind odd, not many aerospace materials rust???
How fast would you have to spin a gear ring to say, launch it on a ballistic trajectory and have it go supersonic? Maybe a factory somewhere had a _really_ catastrophic accident?
There have been a bunch of very powerful non-nuclear explosions. Perhaps a part of an exploding ship such as in the halifax explosion or the Princess Irene?
Cowlings are generally thin aluminum or composite materials, never steel. Cowlings are considered "fairings", generally to smooth the air-stream in and around the engine.
Haha, had it been a cement mixer ring bearing, then there would have been another explanation for the reports that it fell red hot from the sky — that they were as fanciful as the reports of mysterious drones infesting New Jersey (which seem to have actually been real planes). For instance, a broken cement mixer part got dumped there and somebody made up a colorful story.
Proper scientific inquiry demands both an open mind and skepticism. That's why I didn't claim "it's definitely a cement mixer ring bearing" with the usual certainty of people arguing on the internet, but attempted to convey the unreliability of my source.
