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As the saying goes - space is hard. Rockets are a collection of extremes in temperature, pressure, and energy packed as closely as possible and driven to their limits. Even in 2016 they still occasionally fail catastrophically. For example in todays Los Angeles Times business section:

Bill Ostrove, an aerospace and defense analyst at Forecast International, said SpaceX's reliability with the Falcon 9 is 93%, which is "right in the ballpark" of the industry average of 95%.

While most transportation has a per-trip reliability of four, five, or even six nines (i.ie 99.9999%) putting things into orbit doesn't quite have even two nines yet.

But I couldn't help wanting to at least consider if this event could have some non-rocket-related explanation. So I thought I would hypothetically ask out of morbid curiosity, could this event have been caused by some malicious human intent. How vulnerable are space launch vehicles to wackos?

The Mythbusters showed that you can't just shoot a car's gasoline tank and make a Hollywood-friendly event:

Explanation: In Hollywood, it seems like all you need to blow a car to smithereens is a gun and a gas tank. A garage-full of flicks depict people destroying automobiles by shooting straight into to the tank, triggering a massive explosion.

But when MythBuster Jamie Hyneman bored into a Cadillac's full gas tank with a barrage of bullets, no such detonation went down. His six slugs simply ripped right through the tank and out the other side of the otherwise intact sedan.

With no flames to be found, Jamie's gas tank target practice busted the cinematic motor myth.

Citing an entertainment TV show like Mythbusters for a source of factual engineering information is a little painful in itself, however in this case it looks like fairly reliable results.

edit 1: A rocket filled with fuel and oxidizer and various other pressurized gasses is not identical to a car (hat tip to @PeterCordes for pointing that out for us) and cars can not be extrapolated to rockets. So I have asked:

Could a few high-velocity rounds have released enough RP-1 and LOX to have initiated the chain of events seen in today's fast fire (not actually an explosion)? I am not looking for speculation, or opinions of the likelihood. From an engineering perspective, could a few shots from a high power rifle have punctured the spacecraft and tanks and lead to the series of events seen today?

I think the issue of the likelihood that this could actually happen would make a good parallel question, as I am sure there are several precautions in place.


edit 2: Tweet from ElonMusk - there are continuing developments and discussions, don't take this tweet out of context:

Particularly trying to understand the quieter bang sound a few seconds before the fireball goes off. May come from rocket or something else.

edit 3: and there's this stuff.

edit 4: Snippet from the Washington Post - please read the full article there.

...As part of the investigation, SpaceX officials had come across something suspicious they wanted to check out, according to three industry officials with knowledge of the episode. SpaceX had still images from video that appeared to show an odd shadow, then a white spot on the roof of a nearby building leased by ULA, a joint venture between Lockheed Martin and Boeing.

The SpaceX representative explained to the ULA officials on site that it was trying to run down all possible leads in what was a cordial, not accusatory, encounter, according to the industry sources, who spoke on the condition of anonymity because of the ongoing investigation.

The building, which had been used to refurbish rocket motors known as the SMARF, is just more than a mile away from the launchpad and has a clear line of sight to it...

They quote Musk as saying:

“We’ve eliminated all of the obvious possibilities for what occurred there,” he said. “So what remains are the less probable answers.”

Which almost sounds like the engineer's version of "...when you have eliminated the impossible, whatever remains, however improbable, must be the truth...".

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    $\begingroup$ I trust the Mythbusters to more or less accurately depict what they actually did, but not always to extrapolate a conclusion from it, and whether what they actually did was a good proxy for whatever they're trying to test. In this case, it's fairly conclusive that the combo of consumer car gas tanks, gasoline, and normal ammunition won't lead to an explosion or even fire. It's very hard to extrapolate from that to a rocket. Maybe a bullet can generate some steel fragments from the rocket body that hit other steel and make a spark. And rocket fuel isn't gasoline. $\endgroup$ – Peter Cordes Sep 2 '16 at 9:27
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    $\begingroup$ @PeterCordes I didn't say it was! I set up some background/reference point assuming that an answer would draw a contrast between something familliar and something not. The key here is that there is liquid oxygen which - once exposed to the atmosphere - would produce a local, highly oxygenated atmosphere where combustion could happen far faster than gasoline in air, and as pointed out in Hobbes's answer there are other things such as pressurized helium which could potentially serve to disperse a large volume fuel into tiny droplets very quickly (i.e. the "fast fire" tweet). $\endgroup$ – uhoh Sep 2 '16 at 9:44
  • $\begingroup$ @PeterCordes I'd never ever encourage someone to extrapolate anything from a TV show! But you are right, that may not have been obvious to everyone. These comments should clear that up. Thanks! $\endgroup$ – uhoh Sep 2 '16 at 9:47
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    $\begingroup$ I didn't say you were encouraging extrapolation. But it sounded like you were casting doubt even on their experimental data. If you did have an engineering problem that really did match what the Mythbusters had tested, one of their tests might well be a useful data point (if it wasn't one of their many cases where the methodology had a serious flaw...) $\endgroup$ – Peter Cordes Sep 2 '16 at 10:20
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    $\begingroup$ Make enough holes in it and it will Leak too much to go to space ;) no explosions needed $\endgroup$ – Antzi Sep 2 '16 at 18:22
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You'd have to get very lucky. Bullets would punch small holes in the RP-1 and LOX tanks and you'd have small streams of both flowing out.

If the bullet were to hit one of the high-pressure tanks, however (like the helium tank inside one of the first stage propellant tanks), the tank could rupture and release its entire contents at once.

If there was a rifle shot, I expect it would have been clearly audible in the video of the explosion. Apparently there was a sound just before the explosion (which I didn't hear on a casual review of the video), but it's not been definitively identified.

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  • $\begingroup$ I'm pretty sure that a stream of LOX pouring out a hole from the upper stage is a catastrophe waiting to happen when they ignite the engines. $\endgroup$ – Joshua Feb 21 '18 at 21:39
  • $\begingroup$ Only in the sense that the stage would run out of LOX early. The LOX may join the exhaust stream and then some of it will react with unburned propellant, but by then, it's in the middle of a great big fire anyway so no problem. $\endgroup$ – Hobbes Feb 22 '18 at 6:50
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Max effective range of a .50 caliber rifle is on the order of 2000 yards (~1.8 km). I'm trying to find a reliable number for the minimum safe distance from the F9 in the event of a kaboom, but I'm pretty sure that's well short of it (I want to say it's on the order of 3 km, but again, trying to find a source). The shooter would risk severe injury or death.

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    $\begingroup$ en.wikipedia.org/wiki/Longest_recorded_sniper_kills - .50 caliber shots clearly can go farther (approaching 2.5 km for confirmed kills), it just gets increasingly hard to hit your target. Rockets being much larger than people you don't need quite such a precise shot, so I'd guess you could push the range out a bit further. $\endgroup$ – 1337joe Sep 2 '16 at 15:38
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    $\begingroup$ @1337joe: yeah, that's probably true. So, maybe. I just really strongly doubt it. Rockets do occasionally blow themselves up with no outside help. $\endgroup$ – John Bode Sep 2 '16 at 15:42
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    $\begingroup$ It's also worth considering that someone may not even think things through far enough to even consider a kaboom radius, having only watched launches and skate board stunts on YouTube for example. $\endgroup$ – uhoh Sep 2 '16 at 15:50
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    $\begingroup$ The camera footage of the explosion was taken from a bit over 2 km away (going by the audio delay). The camera shook a bit when the shockwave hit, but you're probably okay at that distance, provided you don't get hit by debris. Some debris was found more than 2 km away, but at that distance you have a pretty big volume and a small amount of debris so the probability of a hit is low. $\endgroup$ – Hobbes Sep 2 '16 at 15:52
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    $\begingroup$ Also, gaining access to the site is non trivial. At a minimum people badged for CCAFS will have passed a background check and would have to have a work related reason (theoretically) to be on site. Vehicles entering the gates are also subject to random (or "for cause") searches. And the gates are a loooong way from the pads. Of course an employee could go rogue (it happened at JSC in 2007) but historically it does not happen often. $\endgroup$ – Organic Marble Sep 2 '16 at 17:40
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Apparently the vulnerability is thought to be at least not demonstrably zero. The Washington Post tells us that After 2016 rocket explosion, Elon Musk’s SpaceX looked seriously at sabotage.

The SpaceX employee who showed up at ULA’s facility had an odd request: Could he have access to the roof?

The reason, the employee explained, was that SpaceX had still images from a video that appeared to show a shadow, then a bright white spot, coming from the roof. ULA’s building was about a mile away from the launchpad and had a clear line of sight to it.

ULA was incredulous, and refused to let the SpaceX employee into the building. Instead, it called Air Force investigators, who inspected the roof and found nothing amiss.

Had the vulnerability been clearly zero, this wouldn't have been done.

Had still images shown a macaque with a sling shot, it would not have been pursued as a cause. It might have been pursued as an animal control anomaly in and of itself, but not as a cause of the catastrophic "fast fire".

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    $\begingroup$ For what it's worth, the Foreign Legion provides security for ESA launches in French Guiana, patrolling the jungle around the launch site. They must think there's a danger from snipers or something. $\endgroup$ – Greg Apr 16 at 19:49

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