Isn't physics fun?

Subject: Isn't physics fun?
Author: Techno-Dann
Posted on: 2013-12-03 05:22:00 UTC

Unfortunately, there is one problem with traveling very quickly underwater: cavitation. Water can only re-fill spaces after something has passed through it at a given rate. Once you exceed that rate, the trailing edge of any object (usually propellers) collects little tiny vacuum bubbles. When these collapse (as would be expected from bubbles of pure nothingness underwater), they do so very violently, sending jets of hyper-velocity water and focused ultrasound into whatever happens to be collecting them.

Cavitation is nasty stuff - it eats propellers, impellers, and other high-velocity parts like an unholy combination of sandblaster and water-jet cutter.

On the plus side, if you can get the squid traveling fast enough, you can leave cavitation behind entirely and enter the wild world of supercavitation.

In supercavitation, the shockwave from the leading end of the object (usually with a flat nose and then sharp edges) opens a bubble which, through the application of large amounts of gas and velocity, remains open for the entire length of the object and finally collapses behind it. The object doesn't even get wet - it is flying in a bubble of air underwater.

The Russians played with supercavitating torpedoes - it is theorized that they could hit 300 knots, or roughly half the launch velocity a hypothetical flying kraken would need.

Obviously, establishing and maintaining a supercavitation bubble around a giant squid is a challenge for magic, as it's hard to mount a forward-firing rocket on the nose of a squid. Keeping the squid supplied with water will also be a challenge. The whole process will be anything but subtle - the squid will produce a huge wake as shock waves and then gas bubbles reach the surface.

On the plus side, though, you now have a squid capable of traveling at significant fractions of the speed of sound while utterly immune to lightning, fire, or other mage-friendly weapons. It only needs to travel near a ship to destroy it utterly, and with one good blast, the squid can jump tactically significant distances inland to deliver a cargo of kraken-knights.

You might even have to measure its effective range in kill-o-meters.

-Dann

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Just a few more hours left... by AW on 2013-12-01 00:44:00 UTC Reply

...until NaNoWriMo is finished. How did everyone who was participating fare?

I will admit that it wasn't one of my best ventures, though the experiment (have nothing planned out except for who's the protagonist and the setting) was an eye opener; at least have a rough idea of what I want to write. I hit a plot wall about 30k in and the plot that was there was very slow moving. I had to start another story that wasn't fleshed out very much either.

But I did manage to reach the 50,000 today. Much earlier than I usually verify. I'm usually just a couple of hours away from the deadline.

So, how was everyone's NaNo go?

~AW~

IntelligentAirhead and I started a week late, by Lily Winterwood on 2013-12-03 03:49:00 UTC Reply

but we got to about 50,409 words on December 1 in our super long Star Trek Writer!AU. :'D

Then again, the main plot got held hostage in favour of a roadtrip to Scotland to find the Jim Kirk Prime of this AU, so that contributed significantly to our word count. :'D
51,163! by Huinesoron on 2013-12-01 18:53:00 UTC Reply

On the 29th, even!

It was heaps of fun writing The Kraken-Knights of Wintertide, and not just because I got to keep referencing that title. It was one of those novels where I occasionally sat down and calculated something (such as the instantaneous velocity required for a jet-propelled giant squid to fly in an arc and touch down a couple of miles away), only to discover that I didn't like the answer - and so, being NaNo, I just ignored it and did it anyway. (Magic! Totally magic)

I also managed to keep track of almost all of my plot-hooks, and resolve them by the end - without even using too many deii ex machina. Fun, fun stuff.

hS

Great going! Will you be making an aim at publication? (nm) by Ekyl on 2013-12-01 19:49:00 UTC Reply
Er... by SeaTurtle on 2013-12-01 19:38:00 UTC Reply

...what did you need the jet-propelled giant squid for?

~~Please don't say it was a dynamic entry vehicle~~

All giant squid are jet-propelled. by Huinesoron on 2013-12-01 20:54:00 UTC Reply

And what else would a kraken-knight ride on?

hS

Point taken. by SeaTurtle on 2013-12-01 21:15:00 UTC Reply

Incidentally, what was the velocity needed for your squid to fly whatever distance it needed to cover?

Considering cephalopods aren't the most aerodynamic creatures on the planet and that the mass of a giant squid is something on the order of 150-250kg according to Wikipedia, that ride would have needed a titanic force to get it off the ground.

...and with titanic force goes titanic acceleration. I hope the kraken-knight was wearing their seatbelt.

Am I seriously discussing squid ballistics? Wheeee!

Exactly. by Huinesoron on 2013-12-01 21:36:00 UTC Reply

Even neglecting air resistance - which of course removes both mass and streamlining from the equations - I was getting answers of multiple thousands of kilometers per second. Even if I managed to make a mistake - entirely possible, this was NaNoMaths - it was still way higher than a human (or kraken) body could withstand - or than a giant squid could produce.

So I ignored it. Maybe the gravity's weaker there, or maybe the squid jet for longer than just while they're in the water, or maybe magic. ;)

hS

(And yes, seat-belts were worn. Or at least, buckles and harnesses)

Thousands of km/sec seems a bit high... by Techno-Dann on 2013-12-01 22:58:00 UTC Reply

According to long-ago lessons in model rocketry, the worst-case for rocket misbehavior is if the rocket launches at about a 45-degree angle. In such a case, it'll only achieve half its expected altitude, but it will cover four times that distance downrange.

To give us nice easy round numbers, let's say that our giant squid is wanting to fly about four kilometers downrange. This gives a maximum squid altitude of one kilometer, enough to clear even the tallest man-made structures on earth. Presumably, this will be plenty of height to clear whatever anti-squid defenses exist to resist the transient cephalopod.

From a kilometer of altitude, disregarding air resistance, an object will take 14.1 seconds to free-fall to the surface, at which it will arrive at an impressive 141 m/s. If the squid happens to have 141 m/s of lateral velocity when it starts its flight, it will also cover two kilometers downrange over that time.

This whole process works backwards too - if the squid can achieve a launch velocity of 200 m/s, at a 45-degree angle, it will cover four kilometers before arriving at its destination. (Assuming launch site and destination are at the same altitude.)

That's a launch velocity of roughly 450 MPH - nontrivial, certainly, but still subsonic. If we assume that a kraken can inhale 25% of its body weight in water, it only needs to eject that at 1 km/sec to achieve the aforementioned launch velocity. A bit beyond the ordinary, certainly, but it's reasonably achievable - the exhaust velocity from the space shuttle's main engines is more than four times that.

I think... by Huinesoron on 2013-12-02 09:11:00 UTC Reply

... I was probably calculating a 4-mile-or-so flight. I suspect that gave me a speed around about 1000 kph - which, yes, is a lot less than that many kps. ;) It's still, like you say, pretty impressive.

I'm intrigued by your closing statement - the one that makes the whole thing at least moderately plausible (assuming our krakens are biomagically augmented, which they probably are). Assuming you can cover some of the distance underwater - which, with the right plumbing, could provide infinite quantities of water through in a constant stream - I think it's definitely plausible.

Good thing I never drew a map, though. It's a lot easier to fudge if you don't have any actual distances.

Thank you!

hS

Isn't physics fun? by Techno-Dann on 2013-12-03 05:22:00 UTC Reply

Unfortunately, there is one problem with traveling very quickly underwater: cavitation. Water can only re-fill spaces after something has passed through it at a given rate. Once you exceed that rate, the trailing edge of any object (usually propellers) collects little tiny vacuum bubbles. When these collapse (as would be expected from bubbles of pure nothingness underwater), they do so very violently, sending jets of hyper-velocity water and focused ultrasound into whatever happens to be collecting them.

Cavitation is nasty stuff - it eats propellers, impellers, and other high-velocity parts like an unholy combination of sandblaster and water-jet cutter.

On the plus side, if you can get the squid traveling fast enough, you can leave cavitation behind entirely and enter the wild world of supercavitation.

In supercavitation, the shockwave from the leading end of the object (usually with a flat nose and then sharp edges) opens a bubble which, through the application of large amounts of gas and velocity, remains open for the entire length of the object and finally collapses behind it. The object doesn't even get wet - it is flying in a bubble of air underwater.

The Russians played with supercavitating torpedoes - it is theorized that they could hit 300 knots, or roughly half the launch velocity a hypothetical flying kraken would need.

Obviously, establishing and maintaining a supercavitation bubble around a giant squid is a challenge for magic, as it's hard to mount a forward-firing rocket on the nose of a squid. Keeping the squid supplied with water will also be a challenge. The whole process will be anything but subtle - the squid will produce a huge wake as shock waves and then gas bubbles reach the surface.

On the plus side, though, you now have a squid capable of traveling at significant fractions of the speed of sound while utterly immune to lightning, fire, or other mage-friendly weapons. It only needs to travel near a ship to destroy it utterly, and with one good blast, the squid can jump tactically significant distances inland to deliver a cargo of kraken-knights.

You might even have to measure its effective range in kill-o-meters.

-Dann

Wouldn't any anti-squid defences take that into account? by Ekyl on 2013-12-02 00:05:00 UTC Reply

Re: One kilometre altitude. I'd think they'd make sure their anti-squid stuff actually has the range to hit the squids they're anti-ing. :P

Thesis Month by Sevenswans on 2013-12-01 17:01:00 UTC Reply

Is finished.

I finished my 31 k thesis yesterday. Tonight, I intend to game until I pass out. :D

(31 k of research is arguably harder to write than 50 k of novel: every sentence or so has to be researched and cited. So it totally counts, even though some of the writing was done in October. :D )

Next year, I can do NaNo properly!

Number Count by AW on 2013-12-01 21:48:00 UTC Reply

Then you should have done a 19k short story!

Word count is word count. You totally could have used your Paper, me thinks.

Ah well. To next year! (Or Summer Camp NaNo)

Badly, very badly. by Storme Hawk on 2013-12-01 04:07:00 UTC Reply

Besides a ton of problems IRL I kept hitting walls and writers block almost from the off. Managed to squeeze out 29k, which I suppose isn't too bad for a first attempt. But still...
50k! by Techno-Dann on 2013-12-01 00:51:00 UTC Reply

I hit 50k... a week ago. I managed to hold pretty close to 2k a day, plus a few bonus thousands on weekends.

Of course, my protagonist died at 47k and then pulled a Gandalf for the last 3k, but that's beside the point.

Well, that was unexpected by Sevenswans on 2013-12-01 17:02:00 UTC Reply

Congratulations, sir! Tonight, we drink bleepolate milk in your honor!
Kill your darlings! by AW on 2013-12-01 01:19:00 UTC Reply

I can't say I've ever killed off my protagonist either. That's pretty awesome.

I was hoping to try and do a 2k/day goal, but I was hit by a strange exhaustion this year so there were some days that I didn't write at all. That ruined that plan.