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Comment by dangus | Hacker News Reader

This article is missing a ton of new information about this issue.

https://www.cntraveler.com/story/new-tsa-approved-3-d-scanne...

The whole reason for the rule is that X-Ray machinery uses object density to help figure out what materials are inside your luggage.

(This is a gross simplification of a different article I read on this subject, don't trust me to be 100% accurate in my terminology)

Some airports have more advanced X-Ray machinery where it can be extremely accurate to the point where it can distinguish water and other liquids from explosives.

But in many/most airports, they just have to ban liquids because the machinery can't tell the difference between water and explosives.

It's a pretty simple and logical explanation, and I think the rules make some level of sense given the fact that there was an actual attempted security breach involved with making the rule in the first place.

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It's theater. There are much better and easier ways to commit mass murder than trying to take down a plane. And yet, we don't see waves of airport bombings, train/train station bombings, shopping mall bombings, stadium bombings, theater bombings, etc. Why are planes so special that we have to endure inconveniences and privacy violations in order to secure them, when we seem not to care about all these other things?

The fact that someone tried (and yet failed!) to detonate a liquid explosive on a plane is not an excuse to ban water. Water! A basic requirement for life! It's absurd.

Recurring inconvenience is a good basic test for compliance.

> Why are planes so special

Psychology. A flight passenger's life is in the hands of others for a span of hours at a time. The victims of a hypothetical attack are hopelessly trapped, whereas one can at least imagine theoretically fleeing the scene in most other cases. These things make the threat seem far more salient.

Also, humans are generally bad at understanding small probabilities.

I dunno, 9/11 proved that a plane is efficient enough at destruction to take down an entire supertall office building. Can someone do that in a theater, train station, or stadium?

And in the decades before 9/11, hijackings were actually a somewhat regular occurrence and real threat.

Yes, there is security theater involved, but I think airplanes are very obviously a special case. When they used to get hijacked it was a difficult situation because authorities were trying to deal with a fast moving plane with civilian lives on it (so they can’t just shoot it down), and that person could cross borders and do all kinds of things that you can’t do any other way.

They can be flown anywhere quickly, they can’t be evacuated when they flying, and they can quickly cross borders and barriers.

Water isn’t banned, either. There’s plenty of free water past security. Bring an empty water bottle.

Or just bring ice: https://www.tsa.gov/travel/security-screening/whatcanibring/...

This kind of scanning is a waste of time. It does an ineffective job of reducing a very small risk. If the machines can't tell the difference between water and explosives, and we're not willing to do fallback testing, then the solution is to not use the machines. Not to ban water.

Octane 0.703 g/cm^2

Acetone 0.7845

Water 0.99834

Hydrogen peroxide 1.1 (30%) - 1.450 (pure)

There is basically no way to synthesize PETN or TATP in-flight on a plane. It's only the cargo culting security theater of "liquids bad" because dumb, failed terrorists tried to use liquids in their explosives incorrectly in ways that don't make sense from a chemistry perspective. There are few liquids that would be a problem. I'd be worried most about mercury and aluminum alloy fuselages and binary explosives in improvised pressure vessels.

I’ve always been a little curious about how well the TSA detects tannerite (a binary explosive typically used for target shooting at ranges where you can’t see holes in paper).

I don’t think it’s particularly potent, but a pound of it will blow a hole in the dirt and a bucket of it will demolish a car (thanks for that tidbit, Moonshiners and FPSRussia).

No idea how much it takes to be problematic on a plane, and I don’t intend to Google it lol.

I was curious because it’s pedestrian as far as explosives go. Bass Pro Shops and Cabellas both sell it, and are happy to sell it in fairly large quantities. I think I bought 10 pounds last time I was there (20 explosive targets iirc) and no one batted an eye.

Tannerite's oxidizer, containing AN and AP, are both easily identified in airports because they contain ammonium which contains nitrogen.

Alkanes like butane, propane, gasoline, and other naptha-like products would also be pretty bad on an airplane too because they could incapacitate people and create a catastrophic explosion if quickly dispersed at a high enough concentration and ignited. It would take probably a kilo or more and lots of energy to vaporize it bring down a plane from a vapor explosion.

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