Starship Flight 7

Looks like second stage broke up over Caribbean, videos of the debris (as seen from ground):

https://x.com/deankolson87/status/1880026759133032662?t=HdHF...

https://x.com/realcamtem/status/1880026604472266800

https://x.com/adavenport354/status/1880026262254809115

Moment of the breakup:

https://www.instagram.com/reel/DE52_hVSeQz/

> (as seen from ground)

As seen from a plane in the air with the break up right in front of it:

https://old.reddit.com/r/aviation/comments/1i34dki/starship_...

While the video post does mention "Right in front of us", and it may have appeared that way to the pilots, it wasn't. Gauging relative distance and altitude between aircraft in flight can be notoriously deceptive even to experts, especially in the case of intensely bright, massive, unfamiliar objects at very high speed and great distance.

The RUD was in orbit over 146 kilometers up and >13,000 mph. I'm sure using the FlightAware tracking data someone will work out the actual distance and altitude delta between that plane and the Starship 7 orbital debris. I suspect it was many dozens of miles away and probably still nearly orbital in altitude (~100km).

Spectacular light show though...

It's in front of them enough.

Sure. In a similar way as when the moon is low on the horizon and I stand in my back yard facing it. There's the moon. It's right in front of me... :-)

in a way that if they kept their heading there was a higher than acceptable risk of impact and they had to divert, yes.

As I said, the debris was likely closer to around ~100km in altitude. Commercial airliners fly around ~10km in altitude. Appearing to be at a similar altitude as the plane and "in front" of it was an optical illusion because the debris was intensely bright, very far away, very high and moving several times faster than a bullet. While we don't have exact data yet, I believe it is highly likely there was zero chance of that plane ever hitting that debris given their relative positions. It couldn't even if the pilots weren't mistaken about how close the debris was and they had intentionally tried to hit it. The debris was too far, too high and moving at hypersonic speeds (hence the metal being white hot from atmospheric friction).

Starship's flight paths are carefully calculated by SpaceX and the FAA to achieve this exact outcome. In the event of a RUD near orbit, little to no debris will survive reentry. Any that does survive won't reach the surface (or aircraft in flight) until it is far out into the Atlantic Ocean away from land, people, flight paths and shipping lanes. For Starship launches the FAA temporarily closes a large amount of space in the Gulf of Mexico to air and ship traffic because that's where Starship is low and slow enough for debris to be a threat to aircraft. These planes were flying in the Caribbean, where there was no FAA NOTAM closing their airspace because by the time Starship is over the Caribbean, it's in orbit. If there's a RUD over the Caribbean it's already too high and going too fast for debris to be a threat to aircraft or people anywhere near the Carribean. The only "threat" in the Caribbean today was from anyone being distracted by the pretty light show in orbit far above them (that looked deceptively close from some angles).

> the debris was likely closer to around ~100km in altitude. Commercial airliners fly around ~10km in altitude

(Not wishing to ask the obvious, and depending on the size of the pieces) debris at 100km altitude pretty much always ends up being debris falling through 10km ... right?

At the incredible speeds Starship was moving (>13,000 mph) by the time it was over the Caribbean, debris from a Starship is expected to burn up by the time it reaches the surface. But you said "depending on the size", so let's imagine it's a different spacecraft carrying something that won't entirely burn up, like the Mir space station from several years back.

In that scenario, debris from 100km will survive to pass through 10km. The point is: if the mass becomes debris >143km high traveling at >13,000 mph over the Caribbean - it doesn't pass through 10km anywhere near the Caribbean. Even though the friction causing tempered metal to glow white hot is slowing it, the trajectory is ballistic so by the time it slows enough to get that low (10km) it's hundreds or thousands of miles East from where the explosion happened (and where that airplane was).

It's weird because given these orbital velocities and altitudes, our intuitions about up and down aren't very useful. Starship exploded in orbit over the Caribbean, so planes in the Caribbean were safe from falling debris. If it was Mir instead of Starship, planes hundreds or thousands miles to the East of the Caribbean would be at elevated risk. My high school astronomy teacher once said something like "Rockets don't go up to reach orbit. They go sideways. And they keep going sideways faster and faster until they're going so fast, up and down don't matter anymore." While that's hardly a scientific summary, it does give a sense of the dynamics. You'll recall that Mir was intentionally de-orbited so it would land in a desolate part of the Indian Ocean. So, did they blow it up right over the Indian Ocean? Nope. To crash it in the Indian Ocean, given the altitude and speed, they "blew it up" on the other side of Earth, like maybe over Chicago (I actually don't recall where the de-orbit began, but had to be very far away).

> so by the time it slows enough to get that low (10km) it's hundreds or thousands of miles East from where the explosion was seen

Appreciate that, the question would be, do we know that there won't be any aircraft at the right (wrong) altitude in that area(?!)

With aircraft regularly travelling thousands of miles, would be interesting to know whether route choices are made to avoid being "under"* the track of a rocket's launch?

There's apparently another video of the debris, this one appears to show very clearly that the debris is "going sideways"* rather than coming vertically down https://x.com/kristinafitzsi/status/1880032746032230515?s=61

* apologies for the poor phrasing :)

There are people on HN far better qualified than I to discuss both orbital mechanics and spacecraft safety assessments but I'll give it a layman's stab based purely on the high-level concepts (which is all I know).

They know there's little to no risk to aircraft or people hundreds or thousands of miles to the East of a Starship RUD in orbit because they know exactly what's inside Starship and how it's built. They model how it will break up when traveling at these insane speeds and how the metal masses will melt and burn up during re-entry. They actually test this stuff in blast furnaces. It's a statistical model so it's theoretically possible a few small bits could make it to the ground on rare occasion, so we can't say debris will never happen - but there's been a lot of history and testing and the experts are confident it's extremely safe.

The case of the MIR space station was very different than a Starship. MIR was built a long time ago by the Soviet Union and they used a big, heavily shielded power plant. That lead shielding was really the part that had a significant risk of not burning up fully on re-entry. Starship, Starlink satellites and other modern spacecraft are now usually designed to burn up on reentry. However, there are still some things in orbit and things we'll need to put in orbit in the future that won't entirely burn up on reentry. There will always be a very small risk of an accidental uncontrolled reentry causing a threat. However, these risks are vanishingly small both because we design these spacecraft with redundant systems and fail-safes and because Earth is mostly uninhabited oceans, much of our landmasses are unpopulated or sparely populated, even in the unlikely event one of the few spacecraft with a large mass that won't entirely burn up has failed and is de-orbiting out of control, we can still blow it up - and timing that at the right moment will still put it down in a safe place (like it did with MIR). There's no such thing as absolute 100% perfect safety. But you're far, far more likely to die from a great white shark attack than be injured by satellite debris.

More to the point, a huge number of meteorites hit Earth every year and it's estimated over 17,000 survive to hit the surface. There are a bunch listed right now on eBay. Do you know anyone injured by any of the 17,000 space rocks that crashed into our planet this year or any airliners hit by one?

That description of heavy lead shielding of a power plant on Mir surprises me since photos show it as having solar arrays. Wikipedia also gives the power source as solar with no mention of lead components. Can you add further details of this?