# Space debris from SpaceX Dragon capsule crashed in the North Carolina mountains. I had to go see it (video)

#### skynr13

The chances of this hitting anyone may be 1 in a trillion, But Mr. Musk should still address the problem as with every flight there is a possibility of someone getting hurt.

#### Unclear Engineer

Checking on that "one in a trillion" probability:

That piece of junk is about 1 square meter.

Earth's surface area is 5.1 x10^8 Km^2 = 5.1 x 10^14 m^2

There are about 8 x 10^9 people on Earth.

So, the probability that some person will be in a particular square meter is (8 x 10^9) / (5.1 x 10^14) = 1.6 x 10^-5. So, about 1 in one hundred thousand. That is per launch of a dragon capsule.

So, the probability that somebody will get hit is not nearly as low as "one in a trillion".

The probability stated in the article is more like the probability that a specific person will get hit, which is more like 1 m^2 / (5.1 x 10^14 m^2 ) = 2.0 x 10^15. So, that is still "two in a trillion", and again, that is per launch of a dragon capsule.

What we really need to do is add up all of the launches that cause some junk to eventually hit the earth's surface, and take into account that the Chinese are having some much larger pieces land from their Long March rockets, to get a probability per year that somebody is going to get hit by a piece of junk falling out of orbit.

We also need to take into account that most of the orbits that are dropping space junk are not polar, so the junk will land in latitudes pretty far removed from the poles, in the latitudes where most people live, so the more accurate probabilities will be higher than the averages I calculated assuming even distributions of falling junk and people across the surface of the Earth.

Yes, we have other risks which are higher. But, if somebody is negligent about putting others at risk, and that causes a death, that is "negligent homicide", which is a felony. It is unavoidable risk that is considered an accident.

.

Ken Fabian

#### skynr13

Checking on that "one in a trillion" probability:

That piece of junk is about 1 square meter.

Earth's surface area is 5.1 x10^8 Km^2 = 5.1 x 10^14 m^2

There are about 8 x 10^9 people on Earth.

So, the probability that some person will be in a particular square meter is (8 x 10^9) / (5.1 x 10^14) = 1.6 x 10^-5. So, about 1 in one hundred thousand. That is per launch of a dragon capsule.

So, the probability that somebody will get hit is not nearly as low as "one in a trillion".

The probability stated in the article is more like the probability that a specific person will get hit, which is more like 1 m^2 / (5.1 x 10^14 m^2 ) = 2.0 x 10^15. So, that is still "two in a trillion", and again, that is per launch of a dragon capsule.

What we really need to do is add up all of the launches that cause some junk to eventually hit the earth's surface, and take into account that the Chinese are having some much larger pieces land from their Long March rockets, to get a probability per year that somebody is going to get hit by a piece of junk falling out of orbit.

We also need to take into account that most of the orbits that are dropping space junk are not polar, so the junk will land in latitudes pretty far removed from the poles, in the latitudes where most people live, so the more accurate probabilities will be higher than the averages I calculated assuming even distributions of falling junk and people across the surface of the Earth.

Yes, we have other risks which are higher. But, if somebody is negligent about putting others at risk, and that causes a death, that is "negligent homicide", which is a felony. It is unavoidable risk that is considered an accident.

.
And that piece of the battery pallet that was eject from the ISS and hit the home in Florida and just missed the guy's son is that one in a trillion now pretty much used up. So maybe we now go on to your calculation of 2 in a trillion?

#### Unclear Engineer

That's not the way probability works. And it is nothing like the implication of what I posted.

To sum it up, again:

"What we really need to do is add up all of the launches that cause some junk to eventually hit the earth's surface, . . . "

and

". . . if somebody is negligent about putting others at risk, and that causes a death, that is 'negligent homicide', which is a felony."

The calculations that I presented show where the "one in a trillion" number comes from and also that it is not the relevant number for the probability that falling space junk will hit somebody, which is 8 billion times higher, and applies to only one dragon capsule launch. not the sum of all risk from the hundreds of launches per year we are now doing.

Unless preventative actions are taken, commercialization of space will lead to much higher risk per year, and somebody is very likely to get hit with something. It would not take a trillion years for that to happen,

Ken Fabian

#### skynr13

That's not the way probability works. And it is nothing like the implication of what I posted.

To sum it up, again:

"What we really need to do is add up all of the launches that cause some junk to eventually hit the earth's surface, . . . "

and

". . . if somebody is negligent about putting others at risk, and that causes a death, that is 'negligent homicide', which is a felony."

The calculations that I presented show where the "one in a trillion" number comes from and also that it is not the relevant number for the probability that falling space junk will hit somebody, which is 8 billion times higher, and applies to only one dragon capsule launch. not the sum of all risk from the hundreds of launches per year we are now doing.

Unless preventative actions are taken, commercialization of space will lead to much higher risk per year, and somebody is very likely to get hit with something. It would not take a trillion years for that to happen,
I totally agree, and considering the guy in Florida was almost hit by space junk from the ISS, it seems that much more probable by at least one.

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