Hacker News Reader

Comment by aresant | Hacker News Reader

Two fascinating theories from the comment section @ Wapo ->

"A large stationary target like a rocket is a simple shot for a sniper with a 50 cal rifle from a mile away. . . It was something discussed 30+ years ago: to have Special Forces snipers punch holes in the missiles on mobile launchers that would not be discovered until preparing for launch. Instead of destroying the system the enemy would have wasted time and effort moving to a launch location only to find out that they were incapable of launching."

and

"What the article doesn't mention is that ULA buys its engines from Russia and is a vital part of the Russian rocket program. As a part of ULA's activities, there are Russian engineers with military training in the country legally right now. "

View on HN

Something like a .50 BMG round has a large report and the flight time is just under 2 seconds at a mile, so anything recording audio in the neighborhood would pick up the distinct crack of a rifle prior to the pad explosion. Some of the noise can be suppressed with a big enough suppression device but the sonic boom is unavoidable. Subsonic ammo is simply not workable at these ranges; that's called 'artillery' and it doesn't have sufficient precision to ensure hitting the rocket.

You can listen to the explosion here https://www.youtube.com/watch?v=I6isMuPfxcI

I hear birds chirping. No rifles.

update: yes, I know Elon mentioned the 'quieter bang' sound and it could well be related, but it doesn't sound anything like the crack of a rifle round.

You're right of course; except for one minor nit, the crack you hear is the sound of the bullet. The sound you hear from the rifle is a thump sound. Indeed most infantry soldiers are trained to estimate distance to a shooter by the delay between the crack sound above your head and the thump that follows; 3 seconds is approximately 1km or 1100 yards.

Elon heard something: https://twitter.com/elonmusk/status/774153847371501569

Although I also think sabotage such a weak theory.

Yes, that sound is clearly audible in this better version with synchronized audio https://youtu.be/maRTEzlSBLk?t=1m8s

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

Suppressed 50. Cal sniper rifles is available I believe.

That doesn't do anything about the crack of the hypersonic bullet though unless you use subsonic rounds instead.

Which, due to the drag over several miles, would be an impossible shot.

I've not heard of subsonic rounds being used at distances over five hundred yards, and even that is a very difficult shot for that low velocity.

Try this synchronized sound version, which shifted the entire audio stream. (The one you linked to appeared to only start sync'd audio at the exact explosion moment.)

https://youtu.be/maRTEzlSBLk?t=1m8s

You can hear a distinct and odd metallic noise just before the explosion.

> You can hear a distinct and odd metallic noise just before the explosion.

Which would be very consistent with a bursting tank within the rocket.

I don't know anything about fluid dynamics but I know something about shooting and being shot at. I agree with your comment. I would only add that rifle fire sound can be somewhat directional and depending on the temp, density, humidity, height above ground, and reflectivity of the ground much of the impulse can be dissipated or distorted.

Surely sensors would have picked up the impact a .50 makes. Although I don't know why one would need a .50. It's a heavy round with lots of drop and it's not like the rocket is armored. From what I've read of the relative fragility of rockets you could get by with a very small round in just the right spot.

But you will need accuracy to hit "just the right spot", and to get accuracy at long distance, you need a heavier bullet (https://en.m.wikipedia.org/wiki/Sniper_rifle#Maximum_effecti...: "The recent trend in specialized military sniper rifles is towards larger calibers that offer relatively favorable hit probabilities at greater range"), don't you?

True, but "heavier bullet" does not always mean "larger caliber". Also there's no telling at what distance a sniper team would have to be. Maybe they could be inside of 1km?

Also "just the right spot" could be huge on a rocket. The thing is as wide as a barn.

> I hear birds chirping. No rifles.

There's a very audible boom-like sound at 0:06.

.50 BMG is supersonic but drops in velocity rather quickly, like any other small caliber round. Depending on the position of the shooter (especially if opposite to the recording equipment relative to the LV, for example), chances are that the cameras with mikes recording the LV might have problems hearing it. I'm not sure at what distance it drops into subsonic region but the size of the target should allow for some pretty large distance. Powder load could also be tweaked. One has to assume a shooter with significant resources if a deliberate action against a multiple-$100M target is the premise.

On Netflix there is a documentary on the engines it's quite interesting.

The engines were built just as the USSR was collapsing. The engines use a better grade materials and it uses a more efficient combined pumping system 20% better.

The engines were supposed to be scrapped but one of the guys in management diverted them to a warehouse.

Do you recall the name of the documentary?

"Cosmodrome"

The substance of the doc is good but it gets very repetitive and almost propaganda-esque toward the end

what was the second one you mentioned?

The same documentary with a different name ;) Never have twins, your brain is useless for quite some time afterwards...

Congratulations on your little ones!

We have one baby (she is almost 7 months old now) and my brain feels completely useless. I can't even imagine twins.

Those were the NK-33's used on Antares, until one of them failed and caused the loss in 2014...

The RD-180 in question, by contrast, is newly manufactured specifically for the Atlas rockets.

RD-180 was not manufactured specifically for Atlas. The US got involved in the development and testing once they'd picked the RD-180 but the engine predates the program, and is a direct descendant of the RD-170 to boot.

Good to know.

Thanks.

ULA Atlas V uses newly built RD-180, not stored RD-33 from the 1960s. Both engines use the Russian oxygen rich staged combustion which makes them more fuel efficient than kerolox engines developed in the US.

Oddly, the 'enemy' in that scenario was NATO. Mobile missiles like Pershing and GLCM were primary targets for the Soviet Spetsnaz and they has an array of specialist weapons for the task.

Being a Pershing crewman was actually quite high-risk.

When in doubt blame Putin

Just eyeballing it, it's about 600-700 ft from the center of the pad to the tree line, so perfectly doable -- would cameras have been watching the tree line? If someone had shot from the top of a roof or something, I'd think cameras would have caught him leaving/hiding. It would be very, very obvious they shouldn't be there.

Leaving before anyone could notice you would be a bit more of a problem.

In my experience security is often not as good as people think it is in general, especially when large orgs are involved. Look into all the cases of anti nuke activists sneaking into nuke plants for example, or the endless cyber security compromises of large companies and governments.

A place like the Cape is tough because you have many, many contractors and commercial users along with multiple civilian and military fed personnel and even academics. It's likely full of people trying to get their work done, not playing "if you see something say something."

How secure is the Cape? Anyone got any experience?

When I was there I was taken into the VAB with a group. The SRBs for the next Shuttle launch were there. Nobody else was in there. "Security" consisted of a guy asking if I had any lighters or matches.

>>Leaving before anyone could notice you would be a bit more of a problem.

So you sit. Hope they don't have dogs, wait for dark, then exfiltrate. Hell, there are even ways to counteract dogs.

How many former snipers do you think there are in civilian life? How many smart rednecks who can shoot well enough to hit a rocket-sized target at 300 yards? (hell, I'm in that category...)

Somewhere in the union of those two sets, there may exist somebody with sufficient motivation to pull something like this, and enough spare time to prepare well enough to succeed.

I'm not saying that this is what happened, but I am saying that it's far from impossible.

It takes about 4-5 seconds from the noise to the explosion. Wouldn't that be a pretty slow bullet? I wonder how much evidence of such a thing would be left after an explosion, too.

The bullet may have caused a failure that lead to an explosion a few seconds later.

In which case, hopefully someone has run the video through a Eulerian magnification process ( http://people.csail.mit.edu/mrub/vidmag/ ).

A bullet hitting the rocket would cause ripples in the sheet metal that ought to be visible.

The second comment makes very little sense, RD-180 is already being used as a political football (Russia made noise towards forbidding military payload uplifted with RD-180s, and Congress temporarily banned their use over Crimea in 2015) and USAF and ULA have started investigating replacement engines.

It seems like hitting it directly is feasible, about would this not cause both entry & exit holes? I don't know how detailed the telemetry is/how damaged the tank is, but it seems like it would result in a slightly different failure than a single puncture.

I want to say there wouldn't be an exit hole if it met a bunch of liquid after entering. I think it would just disintegrate but there's not a lot of videos of guys shooting rounds into LOX/RP-1.

> there's not a lot of videos of guys shooting rounds into LOX/RP-1

What a job that would be--Elon tells you to get a slo-mo camera and start target shooting LOX at sniper distances "for research".

Many "non flammable" things burn in LOX. A recently-deformed bullet is hot. I expect it would burn fiercely.

Raufoss in Norway produce specialist explosive anti-materiel 12.7mm rounds that would be suitable, but they don't sell to civilians or even police forces.

Steel-core 7.62x54 would probably do it well enough. And you can buy that by the case, cheap.

All you would really have to do is get fuel dripping out along the surface to a point where it would ignite from heat from the engine exhaust.

Not even. LOX is explosive when it contacts organic matter like wiring harnesses, plus Dewars are very fragile, and breaking the vacuum would result in a lot of boil off.

I did not know this. So it's even easier than I thought to sabotage a rocket launch.

Thanks for replying--I would have gone to my grave not even considering the fact that rocket fuel has oxidizers mixed in, but the search you just sent me on set me straight.

It's not mixed-in, it's in a separate tank. But since the tank is an aluminum alloy (often with copper or lithium mixed in) these days, I wonder about its behavior in the presence of an ignition source (some magnesium in the bullet or perhaps even just friction?).

There's no Dewar vessel on the LV as far as I'm aware of. The surface of the stage is the propellant tank, made of simple Al-Li alloy, several millimeters thick. It works fine because of the large mass of the LOX and the comparatively short time of the stage's operation. You just can't transfer enough heat into the stage naturally in the short twenty or thirty minutes between fueling and launch to cause any trouble.

Before they started supercooling the LOX, it was even easier because heat transfer into LOX tanks is conventionally managed by boil-off (in launchers without supercooled propellants, latent heat keeps the liquid at a stable temperature and a trickle refills the tank continuously until a minute or two before launch).

The biggest problem with the lone-gunman theory is this: what if the rocket was hit in an area that didn't cause an immediate, violent explosion?

If you hit the rocket at all, something will fail, very possibly in a manner that will either be noticed before launch or discovered by a subsequent investigation. A .50 caliber bullet hole with its edges facing inward will not be missed by investigators, if there's anything left to investigate at all.

So, no. Nobody shot the rocket with a sniper rifle, because that would be stupid. They would be very likely to get caught, or to cause detectable damage that would obviously not be SpaceX's fault.

There's an interesting, if a bit overdone documentary on Netflix called "Cosmodrome" concerning those Russian engines.

I hope next time SpaceX put some bullet detectors around the rocket. Although sniper could hit the rocket mid flight, where nothing much you can do I guess.

Do bullet detectors exist? For this big of area?

Also black ops would never do the same trick twice :)

Shotspotter.com

I think it's fair to point out that shotspotter specifically has been criticized for being highly inaccurate in practice.

They're basically just microphones you set up around an area to triangulate the source of any gunshots by sound.

Reply on news.ycombinator.com