Celebratory Gunfire Brings Down a Satellite

[dogjones]

Not really. But I read in this article that NASA are perfectly happy to let 550kg of satellite fall randomly to the earth.

They calculate odds of hitting someone at 3200 to 1. This seems a little too probable to me.

For some reason it reminded me of the perils of celebratory gunfire.

What are the odds of a single shot fired into the air randomly from a random location in California hitting someone? At a total wild guess, 3200 to 1 kinda sounds right.

Are NASA being irresponsible here? Should they take a leaf out of the State of California's gun laws? Actually where would the 3200 to one figure have come from anyway?

Bad argumentation I know, but just musing.

 

[NoahFence]

They really should do a bit of math and get a better idea where it's going to land.....

"Only" 556KG should survive. That makes me feel much better!

 

[excaza]

To be fair, chances are it's not going to fall in a single 556kg chunk, but break into many chunks. It's still not very reassuring that they're just going to let it fall at random, but I'm guessing it's not the first time they've done this.

 

[Eric D]

What do they usually do? Is there any way to intercept the satellite and if there is, is it worth it? Just let it fall.

 

[excaza]

What do they usually do? Is there any way to intercept the satellite and if there is, is it worth it? Just let it fall.

What they usually do is exactly what they're doing now, put it in a (more) decaying orbit and let it burn up on re-entry. I'm just not familiar enough with it to know how bit the chunks usually are.

Deorbit of Mir, for example.

 

[bluesjnr]

Not really. But I read in this article that NASA are perfectly happy to let 550kg of satellite fall randomly to the earth.

They calculate odds of hitting someone at 3200 to 1. This seems a little too probable to me.

For some reason it reminded me of the perils of celebratory gunfire.

What are the odds of a single shot fired into the air randomly from a random location in California hitting someone? At a total wild guess, 3200 to 1 kinda sounds right.

Are NASA being irresponsible here? Should they take a leaf out of the State of California's gun laws? Actually where would the 3200 to one figure have come from anyway?

Bad argumentation I know, but just musing.

Dunno about a bad argument but for sure it's a bad conversion of tonnes to Kg. I think you'll find this lump weighs in at 5400kg. Watch out!

 

[NoahFence]

To be fair, chances are it's not going to fall in a single 556kg chunk, but break into many chunks. It's still not very reassuring that they're just going to let it fall at random, but I'm guessing it's not the first time they've done this.

If it's totally dead though - I'm not sure how they could control it. At the very least they should narrow down where it's going to hit.

 

[phunk]

Not really. But I read in this article that NASA are perfectly happy to let 550kg of satellite fall randomly to the earth.

They calculate odds of hitting someone at 3200 to 1. This seems a little too probable to me.

For some reason it reminded me of the perils of celebratory gunfire.

What are the odds of a single shot fired into the air randomly from a random location in California hitting someone? At a total wild guess, 3200 to 1 kinda sounds right.

Are NASA being irresponsible here? Should they take a leaf out of the State of California's gun laws? Actually where would the 3200 to one figure have come from anyway?

Bad argumentation I know, but just musing.

NASA already has stricter rules about this sort of thing. Unfortunately, this one was launched before they came up with those rules.

 

[ben m]

Dunno about a bad argument but for sure it's a bad conversion of tonnes to Kg. I think you'll find this lump weighs in at 5400kg. Watch out!

No, the units are right. It's a 5400kg satellite of which about 4900kg are expected to burn up, and 550kg of particularly-robust components are expected to hit the ground.

 

[excaza]

If it's totally dead though - I'm not sure how they could control it. At the very least they should narrow down where it's going to hit.

You don't need to control it. Even if it was completely dead, there is still enough aerodynamic drag to eventually deorbit anything you put up there.

 

[ben m]

What are the odds of a single shot fired into the air randomly from a random location in California hitting someone? At a total wild guess, 3200 to 1 kinda sounds right.

Area of california: 4 trillion square feet.
Number of people: 37 million.

At 2 square feet each, Californians take up 75 million square feet.

The odds of a random statewide bullet hitting a Californian, if everyone is outdoors at the time, is 60,000 to 1.

Same calculation for Los Angeles: if everyone were outdoors at the same time, the odds of a vertical bullet coming down in someone's 2-square-foot personal space is about 2000 to 1.

 

[dasmiller]

At the very least they should narrow down where it's going to hit.

That's not necessarily possible at this point. Bear in mind that the spacecraft currently circles the earth every 90 minutes or so, so predicting the impact within a few thousand km means predicting the impact time to within a few minutes, and that's simply not possible from here.

Low earth orbits generally decay due to atmospheric drag. Yes, the atmosphere is very thin at LEO (it can be considered a vacuum for most purposes), but it's there.

For a large, irregularly-shaped object like this thing, the orientation of the spacecraft can have a very large impact on the drag. The orientation will certainly vary over the next month or so, and it'll probably vary in a fairly chaotic manner, so orientation uncertainty alone would give a large uncertainty in the schedule. And even if they knew in advance what the orientation was going to be at each minute for the rest of the spacecraft's life, I doubt that they have accurate drag coefficients so they still wouldn't be able to predict the trajectory very well.

Also, the density of the upper atmosphere varies substantially in ways that aren't very predictable. IIRC, solar activity can cause the upper layers of the atmosphere to 'puff up,' causing a dramatic increase in the density at 50-100 km altitude. That, in turn, would cause a dramatic increase in the amount of drag that the spacecraft was experiencing, and since we can't predict that sort of thing very well, we can't predict the reentry date very well.

 

[dasmiller]

Same calculation for Los Angeles: if everyone were outdoors at the same time, the odds of a vertical bullet coming down in someone's 2-square-foot personal space is about 2000 to 1.

This is probably why the bad guys in movies set in LA usually shoot their guns horizontally rather than vertically.

ETA: This is also why I generally stay indoors.

 

[Sword_Of_Truth]

Are NASA being irresponsible here? Should they take a leaf out of the State of California's gun laws? Actually where would the 3200 to one figure have come from anyway?

They are being more responsible than the former Soviet Union.

In 1978 the soviets had a bad launch of Cosmos 954, a military surveillance satellite intended to track US submarines. The satellite failed to reach proper orbit and soon afterward came down over northern Alberta, Saskatchewan and the Northwest Territory in Canada.





Oh yeah... and it had an on board nuclear reactor. Not a radiothermal generator, but an actual reactor. Pieces of Cosmos 954 would have given unprotected personnel in close proximity a dose of 1.1 Sievert per hour (Japan is evacuating people from areas around Fukushima where they might recieve 20 thousandths of a Sievert per year). A joint US-Canadian expedition (wearing lead parkas) was sent to recover the satellite, but less than 1% of the reactors fuel mass was recovered.

 

[dogjones]

To be fair, chances are it's not going to fall in a single 556kg chunk, but break into many chunks. It's still not very reassuring that they're just going to let it fall at random, but I'm guessing it's not the first time they've done this.

Hmm, I would imagine any of those chunks would kill someone, so this would increase the chances of killing someone.

 

[dogjones]

Area of california: 4 trillion square feet.
Number of people: 37 million.

At 2 square feet each, Californians take up 75 million square feet.

The odds of a random statewide bullet hitting a Californian, if everyone is outdoors at the time, is 60,000 to 1.

Same calculation for Los Angeles: if everyone were outdoors at the same time, the odds of a vertical bullet coming down in someone's 2-square-foot personal space is about 2000 to 1.

Nice work!

Ergo, California is more risk-conscious than NASA. Way to go NASA.

 

[dogjones]

NASA already has stricter rules about this sort of thing. Unfortunately, this one was launched before they came up with those rules.

Gotchya.

 

[Complexity]

As long as it hits California...

 

[Molinaro]

It's expected to hit spread out over an area of 500 square miles. Two days before impact they will have better idea of where it will come down.

 

[I Ratant]

This is probably why the bad guys in movies set in LA usually shoot their guns horizontally rather than vertically.

ETA: This is also why I generally stay indoors.

.
It used to be dangerous to be outside on Christmas Eve, New Years, and Easter due to the enormous number of firearms being discharged.
Now, it's really quiet.
Education and some prosecutions have cut the noise to practically zero on those nights.
BTW, it's the just pointed up a bit bullets that fly for miles and injure/kill. The vertical shots go up, stop, and fall back down much slower than they went up.
Probably not fatal if struck.