How Fast Can I Go?

[SAW]

This for all the physics gurus out there.

 

I have a character with 10" of Flight, MegaScaled to 1" = 100KM, Usable Underwater.

 

The question has arisen "how fast can I go underwater before bad things start to happen to the environment (tsunamis, super-heating & flash-boiling millions of gallons of water, etc.)

 

In our campaign the laws of real world physics aren't written in stone but they are written down here... somwhere. Now where did I put those? So you can play a little fast and loose if you so desire.

 

Thanks in advance to all those more schooled than me.

 

SAW

[Bloodstone]

Re: How Fast Can I Go?

 

What's your charactrers SPD?

 

'Cause right now your looking at a speed of 186,420 MPH * SPD. So with a SPD of 1, that about 245 times the speed of sound.

[Phil]

Re: How Fast Can I Go?

 

I'd have to say it's totally dependent on the SFX of the power, and the other powers possessed. In any case, I do wonder whether at that speed he might well be travelling too fast to have any significant impact on the environment.

 

And if you're thinking about real life effects like heat, pressure and so forth, do you also require the PC to have appropriate defences?

 

Phil

[Trebuchet]

Re: How Fast Can I Go?

 

IIRC water at sea level is 16 times denser than air, so at the very least your character should lose 15/16 of that velocity.

 

In reality, nobody has ever made anything go even 1/10 of that speed underwater, so we're treading on new ground here, so to speak. I believe the fastest any object has ever travelled underwater is about 300 knots (Russian "supertorpedoes"), so even at 1/16 of your aerial flight speed your character will be extremely fast (Without knowing his SPD, it's impossible to calculate exactly how fast). If you assume for the sake of playability he's travelling at only 500 knots he's still moving almost 8 times faster than even a cigarette racing boat. Fast enough for you?

 

A human-sized character is far too small to cause a tsunami, but he'll kill thousands of fish from collisions or superheated water. And of course swimming at hundreds (thousands?) of knots risks the character killing himself by colliding with a submarine or underwater object. For our team's starship (which also has Flight Useable Underwater) I limited the submerged speed to about 350 knots; a far cry from its 20,000 KPH in the atmosphere.

[Zed-F]

Re: How Fast Can I Go?

 

This is a superhero game, yes? People can fly through the air without any protection at speeds multiple times the speed of sound, and never have to worry about abrasion, mid-air collisions with foreign object debris, sonic booms, or anything else, right? People can lift freight trains over their heads without worrying about such mundane concepts as leverage, right?

 

I'd just use rubber comic book physics to say there's no impact at all, unless you want there to be one. Say his forcefield makes water slip off so easily there's no friction at all, and the water is barely disturbed in his passing. It doesn't have to make sense if it's a comic book!

[Blade]

Re: How Fast Can I Go?

 

First, *Supergeek hat On!!"

 

Several Points:

 

First, sorry to dissagree with Trebuchet, but water at sea level is about 800x more dense than air at sea level (1000 kg/m^3 vs. 1.2 kg/m^3), so by this logic the character should lose about 99.88% of his/her speed underwater.

 

Second, staying in the water at this speed is a "real" concern. If the character has a speed of 5, they are travelling at 417 km/second, or about 50x orbital speed, so they will rise into outerspace quite rapidly unless they conciously decide to stay in the water or atmosphere (speed overcomes gravity..., see every spacelaunch).

 

Third, again sorry to disagree with Trebuchet, but this character, moving at this speed is a 100 kg comet, expending terawatts of power into the water, much of which would be reflected in a rise in the water (roostertail) above them. I think they would cause significant waves, probably up to tsunami standard. Even a jet-ski has a significant wake, and it moves at 20-30 kph.

 

All that being said, it is a comic book game, but a character with that kind of speed should probably only be able to use it in outer space. After all, even with going into space they could fly around the world in under 2 minutes, so why not travel in space to where you need to go, then fly in the atmosphere/water at non-Megascaled speeds.

[Pogo]

Re: How Fast Can I Go?

 

Some of this depends on the SFX of your movement, but assuming the character actually displaces the water he's moving through, lots of spectacular things happen. Nearby sea life seriously messed up from the pressure waves. Sperm whales stun other creatures with their sonar clicks. Your pressure wave far exceeds their sounds. "Nearby" is relative. If I had to hazard a guess, I'd say 1 km easy.

 

You may also leave a bright path through the water. Ship propellors can produce sonoluminescence -- basically converting sound into light inside bubbles. You're churning up the water a lot more than a ship's prop.

 

If you're moving through the water headfirst, then the surface area is around 0.3 m^2 (very rough estimate, much larger values if Liefield draws you). 10^6 meters/phase means you displace around 3e5 m^3 of water each time you move. A 50 m high, 20 m thick triangular wave would be 600 meters long. That makes for a tsubstantial tsunami in one phase. Just think what you can do with a few held actions

 

How fast do you go before you start vaporizing water? Not as fast as you might think. Remember, you're leaving a vacuum behind until the water rushes in to fill it. Water boils very quickly in a vacuum.

[TaxiMan]

Re: How Fast Can I Go?

 

So how much damage do you take doing a Mach 1,000 move-through of miles of ocean water? Does your head get eroded in nanoseconds?

[SAW]

Re: How Fast Can I Go?

 

OK, time to answer some of those questions.

 

SPD is 7

 

SFX is Magnetic Induction(I think that's what it's called), he locks onto a magnetic field amplifies it's affect on him and decreases the affect of all other magnetic fields on himself thus causing him to move. It's a theory on how UFOs might fly.

 

His Flight is bought Usable As Swimming therefore there is no velocity dropoff in the water. His inches in Flight are considered Swimming.

 

He does have all the defenses and Life Support needed to survive at that speed through the water.

 

Moving at non-Megascaled Flight is not really an option. Well.... it is an option but probably not the best one. He is trying to get to Atlantis as fast as he can. Some Atlanteans(sp?) kidnapped his wife so he is hoping they will not realize that they have a visitor until he is on his way out with her (yes, he can provide her with the ability to survive the trip out).

 

Hope that will help with calculations and math stuff.

 

SAW

[Pogo]

Re: How Fast Can I Go?

 

OK, time to answer some of those questions.

 

SPD is 7

 

[deleted by Pogo for brevity]

 

Moving at non-Megascaled Flight is not really an option. Well.... it is an option but probably not the best one. He is trying to get to Atlantis as fast as he can. Some Atlanteans(sp?) kidnapped his wife so he is hoping they will not realize that they have a visitor until he is on his way out with her (yes, he can provide her with the ability to survive the trip out).

 

Hope that will help with calculations and math stuff.

 

SAW

 

Your character can move at ~583 km/s (7 phases at 1000 km/s). The Marianas trench is 11 km deep. Assuming Atlantis is at the bottom of that trench, you can do 45 laps from surface to Atlantis in one phase. Mark Spitz will be envious. Of course, since you are displacing all that water, see my previous post for the effects on local property values. You will make big waves and boil away some small fraction of the ocean. Actually, from what I've gleaned about shock waves in incompressible fluids, you're boiling lots of water, since the local temperature scales as the Mach number squared, and you're at Mach 388 on the average (Mach 666 if you just look at one phase).

 

So, you want to get in and out as quickly as possible. The speed of sound in water is rather complicated (see http://www.npl.co.uk/acoustics/techguides/soundseawater/content.html#UNESCO for example), and this is a game, so we use the simplified value, 1.5 km/s. As long as you travel faster than that, they won't get any warning from sonar -- you'll outrace the returning pulse. Fortunately, you won't be exceeding the local speed of light, so Cherenkov radiation won't give you away. If we assume no visual contact or magic, the first warning they'll have is when the pressure wave hits. Hard. Very hard. It will be localized, since it falls off as 1/r^2, but I would not want to be in Atlantis when you arrived. Do you have a CvK? Is your wife in an armored cell? Can she breathe water if it breaks? What are her feelings about parboiling? At 1.6 km/s these questions are somewhat important. At 100 km/s, they're critical. Do not go in at full speed.

 

OK, you've got your wife back. Now for the getaway. If you move 1" with your megascale, that puts you on the surface. Now would be a good time to contemplate decompression and the bends You'll be fine if you held your breath, but if your spouse has been breathing pressurized air, she's dead unless you get her into a pressure chamber. You might be better off swimming at constant depth to a different ocean, then calmly ascending.

[ParitySoul]

Re: How Fast Can I Go?

 

Not the mention the electromagnetic side effects of that kinda movement power.

[Duke Bushido]

Re: How Fast Can I Go?

 

Interesting topic, but for your purposes, I think you'd be better off asking your GM about the physics in his world between session. It's fair, since these would be things that the character would know, and base your actions on how 'your world' actually works.

 

For example, you never see Superman stopping to wipe bug smears off his face after a long flight, but realistically--- well, I've got some racing goggles that would indicate what _should_ happen, were Superman in the 'real' world.

[Bloodstone]

Re: How Fast Can I Go?

 

Clearly your racing goggles are inferior to Superman's protective Kryptonian bio-aura!

 

 

And while I will agree that it's best to check with your GM just to see how rubber the physics of the world are, I think it's entierly plauible that the character does NOT know the full reprocussions of his actions. All depends on if he has tried to use his powers at this level ever before. Doesn't sound like it's happened in game, otherwise this question would not really be necessary as anything more then an academic exercise...

[Pogo]

Re: How Fast Can I Go?

 

How did it go? How did it go? Did you go fast? Did you go slow? Seriously, have you rescued your wife yet, and if so what happened?

[Ura-Maru]

Re: How Fast Can I Go?

 

Ah, the joys of Megascale.

 

Since he has 1†= 100 KM, the most precision he can ‘aim for’ is ‘some point within 100 km of his target.†There’s not anywhere on earth where the ocean is 100 km deep. (That’s about the distance from sea level out of the atmosphere completely)

 

So using this power anywhere within earth’s atmosphere has, at minimum, a 50% of having the PC make a very, very big Move Through against the Earth. Which might actually be big enough to kill it, in fact.

 

Kill the Earth, that is, not the character.

 

---

It’s not a good area for experimentation.

[Phil]

Re: How Fast Can I Go?

 

So using this power anywhere within earth’s atmosphere has, at minimum, a 50% of having the PC make a very, very big Move Through against the Earth. Which might actually be big enough to kill it, in fact.

 

Kill the Earth, that is, not the character.

 

Surely the rules applying to Knockback also apply to Move Through. Namely, the point at which an object is destroyed is the limit of the BOD inflicted. Unless the PC has insane rPD and/or BOD, I think the Earth might just win...