Sonic Booms?

[cbullard]

The Flash.  Superman.  Iron Man.  A Quinjet.  The Batplane.

 

All of these and many more can travel at speeds considerably faster than Mach 1, which means they're creating a sonic boom.

 

What is a sonic boom?  According to physlink.com:

 

"...[when a plane] is going at subsonic speeds (lower than that of sound), the sound of the plane is radiated in all directions. However, the individual sound wavelets are compressed at the front of the plane and further spread at the back of the plane because of the forward speed of the plane. This effect is known as the Doppler effect and accounts for the change of the 'pitch' of the plane's sound as it passes us. When the plane is approaching us it's sound has a higher pitch than if it is going away from us. 

 

Now, if the plane is traveling at the supersonic speeds, it is going faster than the speed of its sound. As a result, a pressure (sound is variation in pressure) wave is produced in the shape of the cone whose vertex is at the nose of the plane, and whose base is behind the plane. The angle opening of the cone depends on the actual speed the plane is traveling at. All of the sound pressure is contained in this cone. " (http://www.physlink.com/education/askexperts/ae53.cfm)

 

Note that this is a continuing effect trailing behind the character/vehicle causing it, not just a single-instant thing.

 

So if a character wanted to avoid angering the local populace every time you ran/flew through the area, how (in game terms) could you avoid creating a sonic boom (aside from the incredibly obvious, "slow down," of course)?

 

As a side note, supersonic flight by civilian vehicles over US land.  So a military Quinjet would be clear, but any of the others could be up for prosecution, if the authorities could find a way to press the charges and were inclined to do so.  In an "Age of Ultron"-type of political climate, I could see them being willing...

 

[mrinku]

The Flash avoids the problem by vibrating between molecules. You will note he's the only one without flight.

 

High altitude flight would greatly lessen the effect (as it does for aircraft), both because of thinner air and distance, and would be what the flyers in examples given would use to avoid problems. Superman being Superman, he'd certainly be careful to keep within the speed limit unless it was safe to do so. He also has the option of flying into space at subsonic speed (taking about 40 seconds - space is only about 12km away vertically) and then really opening up the noncombat flight multiple

 

 

The Batplane would not routinely be travelling that fast around Gotham... stealth is Bat's main objective.

 

You left out the various vehicles used by the Fantastic Four (which include a crewed ICBM), but I feel confident that Reed Richards would have thought of that and designed a gadget that nullified the sonic boom. After all, he has neighbours and tenants to consider.

[Lord Liaden]

Speedster heroes make sonic booms when they need to, like for an attack. When they don't want to, they don't. Superstrong heroes can lift cars, trains, even buildings, without breaking them. The edge of Captain America's shield cuts targets or acts like a blunt bludgeon, when he chooses.

 

How do the heroes do these things? They're Just That Good.

[mrinku]

Damn straight.

[Crusher Bob]

It's possible to (greatly) reduce sonic boom noise with aerodynamics. A long (and specifically shaped) needle like nose, careful air intake design, and engine location all seem to matter. Of course, an aircraft designed for this sort of thing means all sorts of compromises in things like performance as a fighter aircraft. It would also interfere with the aerodynamic modifications you need for reduced radar cross section (i.e. 'stealth'). If you still need reduced RCS, there are (even more expensive and not well developed) ways to do that, such as plasma stealth. But even if you were Mr. Fantastic enough to design such an aircraft, I'm not sure if anyone would even be able to build it for you.

 

I guess if you have a completely shape changing aircraft, or do stuff like generate your aerodynamic shape with force fields, then it's much simpler.

 

Example:

[Heroic Halfwit]

I'm no physicist, but seems to me I remember that sound needed a medium through which to travel?  So, why not create a localized vacuum to prevent the sound wave from traveling?  Or maybe I'm mistaking the old adage, "They can't hear you scream in outer space."

[cbullard]

Thank you.  You all have raised some excellent points, and I will definitely be giving them more thought.

 

Unfortunately, my original question remains mostly unanswered:  How, IN GAME TERMS, could you avoid creating a sonic boom aside from slowing down?

 

Mrinku's comment about Flash "vibrating between molecules" might be considered a form of desolidification, which I agree ought to mean no sonic boom.  And yes, Flash can canonically desolidify and pass through solid objects.  But logic would seem to dictate that either he is desolidified/passes through objects/doesn't create a sonic boom, or that he can interact with the physical world/causes a sonic boom, or that anything he wants to do while running that fast has to have the "affects physical world" advantage.

 

Are there any other ways, IN GAME TERMS, that you can you think of that would accomplish this objective?

 

Thanks again!

[cbullard]

How do the heroes do these things? They're Just That Good.

 

 

LOL Amen!

 

Unfortunately, my GMs don't seem to recognize the "Just That Good" power!  ;-)

[cbullard]

Or maybe I'm mistaking the old adage, "They can't hear you scream in outer space."

 

Ah, yes.  I still love that movie!

 

And the send-up comment I heard about it:  Considering that, "In space, no one can hear you scream," they sure made a heck of a racket!  ;-)

[Beast]

in game terms
there is no need to unless you plan on doing an attack
if you really want to push it you could say the need for stealth you apply invisible power effect vs hearing

maybe sight if friction comes up then add sight group

Thank you.  You all have raised some excellent points, and I will definitely be giving them more thought.

 

Unfortunately, my original question remains mostly unanswered:  How, IN GAME TERMS, could you avoid creating a sonic boom aside from slowing down?

 

Mrinku's comment about Flash "vibrating between molecules" might be considered a form of desolidification, which I agree ought to mean no sonic boom.  And yes, Flash can canonically desolidify and pass through solid objects.  But logic would seem to dictate that either he is desolidified/passes through objects/doesn't create a sonic boom, or that he can interact with the physical world/causes a sonic boom, or that anything he wants to do while running that fast has to have the "affects physical world" advantage.

 

Are there any other ways, IN GAME TERMS, that you can you think of that would accomplish this objective?

 

Thanks again!

[massey]

Thank you.  You all have raised some excellent points, and I will definitely be giving them more thought.

 

Unfortunately, my original question remains mostly unanswered:  How, IN GAME TERMS, could you avoid creating a sonic boom aside from slowing down?

 

Mrinku's comment about Flash "vibrating between molecules" might be considered a form of desolidification, which I agree ought to mean no sonic boom.  And yes, Flash can canonically desolidify and pass through solid objects.  But logic would seem to dictate that either he is desolidified/passes through objects/doesn't create a sonic boom, or that he can interact with the physical world/causes a sonic boom, or that anything he wants to do while running that fast has to have the "affects physical world" advantage.

 

Are there any other ways, IN GAME TERMS, that you can you think of that would accomplish this objective?

 

Thanks again!

 

In game terms, there's no such thing as a sonic boom.  Go look through the book and find a page number for me.  It's not there.  In game terms, absolutely nothing happens when you exceed the speed of sound.  So, in game terms, there's nothing to worry about.

[Lord Liaden]

massey makes an good point. As far as game-mechanics go, something that isn't built and costed on a character's sheet does not have to have an impact on play. cbullard, I'm not sure if when you say, "game terms," you aren't actually intending, "game-world terms." I.e. in the reality in which these characters exist, how would you explain these phenomena happening or not happening? That's a different situation, falling under the general heading of what Hero System calls "special effects." It's going to vary from world to world, depending on the ground rules of reality for that setting.

 

In comic books, superheroes violate the laws of physics all the time. However, they mostly do so consistently, so that something that works in an unrealistic way in the past, continues to work that same way. (Unless the writer wants to violate that for the story he wants to tell.)   As one example, in the current official Champions Universe the convention is that the presence of "ambient magic" in the world has "loosened" the laws of physics, so that things like super-powers which would be impossible in the real world become possible.

[massey]

To give a little more explanation, it's like I mentioned in another thread, where someone asked why you don't fall through the Earth when you go Desolid.

 

Powers give you extra abilities.  They don't come with drawbacks unless you put a limitation on it.  This means that you can fly faster than the speed of sound, and you don't cause a sonic boom.  You can cover yourself with a fiery damage shield, and you don't burn (even if you are no more resistant to fire than a normal person).  You can jump really far and you don't splatter when you land.  The default assumption is that your powers don't come with extra cool freebies (even if it would make sense -- your lightning bolt doesn't deafen people with the crack of thunder unless you buy it that way), but neither do they come with penalties unless you buy it that way.

 

The GM, of course, is free to make the game world "more realistic" and add or subtract things.  But that's going to be heavily genre-dependent, and it isn't covered by the basic rules.

[cbullard]

In game terms, there's no such thing as a sonic boom.  Go look through the book and find a page number for me.  It's not there.  In game terms, absolutely nothing happens when you exceed the speed of sound.  So, in game terms, there's nothing to worry about.

 

You wouldn't consider it to be under the heading of "Side Effects" like the various "Dangerous Exhaust" listings on p. 30 of "Ultimate Vehicle"?

[Lord Liaden]

Never forget the "rule of cool" -- if it looks cool, and it fits the genre and style of game, then of course it works. The main point is to have fun playing a style of game you enjoy. Anything that gets in the way of the fun is a detriment. Now, if adding extra explanatory details for how something works would add to your particular brand of fun, then you should go for it. But doing it solely for the sake of "realism" just bogs things down.

[cbullard]

cbullard, I'm not sure if when you say, "game terms," you aren't actually intending, "game-world terms." I.e. in the reality in which these characters exist, how would you explain these phenomena happening or not happening? That's a different situation, falling under the general heading of what Hero System calls "special effects." It's going to vary from world to world, depending on the ground rules of reality for that setting.

 

 

My apologies, I don't always have the precise lingo yet.  That is on me, and I beg the group's patience as I build my vocabulary.

 

What I mean is, assuming there is nothing in the game world that would change this law of physics, what would be some ways in which a character could specify powers/skills/etc that would allow him to travel within an Earth-normal atmosphere at speeds greater than Mach 1 but not to create a sonic boom?

[mrinku]

If you REALLY want a game mechanical solution, IPE (Sound group) on the flight power should cover it.

[mrinku]

Here's a useful link:

 

https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-016-DFRC.html

 

The actual booms really aren't a dramatic as most people think.

 

As far as special effects go, any superpower which operates to avoid building up a leading shockwave in the first place would also avoid sonic booms. The Flash vibrating between molecules has already been mentioned, but many forms of Desolidification would count, as would becoming frictionless or moving by decreasing the air pressure in front of you and increasing it behind you.

 

Or magic.

 

It's also worth pointing out that we are talking a velocity of over 340 metres a second. That's a move rating of 680m for the average Speed 6 character, or a Speed 2 move of 2040m. It REALLY does not come up in combat almost ever and is normally only possible in HERO using noncombat movement, at which point you may as well follow Superman's example and fly high subsonically before letting loose at commercial airline altitudes (or space, if capable).

[cbullard]

Here's a useful link:

 

https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-016-DFRC.html

 

The actual booms really aren't a dramatic as most people think.

 

Yeah, most people seem to think that sonic booms are constantly shattering windows, etc.

 

It's more of an annoyance.  For a commercial supersonic transport plane (SST), it can be as loud as 136 decibels.  By comparison, a loud rock concert is around 120 decibels.  Pain levels for most folks would be in the 120-140 decibel range, which is why they outlawed supersonic flight over US territory.

[sinanju]

Extra-Dimensional Movement for when you're running a supersonic speed.

 

In the "Wearing the Cape" series of novels, speedsters have two speeds. First they're just Really Fast--they can/must interact with the world around them. They're almost impossible to hit, can attack a bunch of goons at once, can grab people and evacuate a fight zone, etc. Their second speed is Sonic Boom Territory. Or as they call it, going "over the wall" and literally vanishing from The World As We Know It into a weird, time-frozen version of the world in which they are the only thing moving. They travel through this weird space, then pop back out at their destination.

 

Which sounds like extra-dimensional movement to me. Just specify that when you would have hit Mach 1 (and created a sonic boom) you flip over into Bullet Time (or whatever you want to call it) until you get where you're going.

[sinanju]

Here's a useful link:

 

https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-016-DFRC.html

 

The actual booms really aren't a dramatic as most people think.

 

As far as special effects go, any superpower which operates to avoid building up a leading shockwave in the first place would also avoid sonic booms. The Flash vibrating between molecules has already been mentioned, but many forms of Desolidification would count, as would becoming frictionless or moving by decreasing the air pressure in front of you and increasing it behind you.

 

Or magic.

 

It's also worth pointing out that we are talking a velocity of over 340 metres a second. That's a move rating of 680m for the average Speed 6 character, or a Speed 2 move of 2040m. It REALLY does not come up in combat almost ever and is normally only possible in HERO using noncombat movement, at which point you may as well follow Superman's example and fly high subsonically before letting loose at commercial airline altitudes (or space, if capable).

 

Iron Maiden, who I'm playing in a face-to-face game right now, has three levels of flight speed. Combat Speed (30 m/phase), Cross-Town speed (just a few inches with lots and lots of NCM multiples), and Cross-Country, which is Megascaled and has her flying about 5,000 mph. I always make a point of having her fly far up into the sky above the city before she switches into that last mode. It's great for getting around the country (or the world) in a hurry, but it never comes up in combat.

 

As I recall from one of Elliott S! Maggin's Superman novels, the FAA maintains a restricted airspace over/around the Daily Planet building specifically for Superman, so he can do what you mentioned--fly high above the city before he goes supersonic.

[dmjalund]

Ah, yes.  I still love that movie!

 

And the send-up comment I heard about it:  Considering that, "In space, no one can hear you scream," they sure made a heck of a racket!  ;-)

but they can year you cough from light years away

[cbullard]

Extra-Dimensional Movement for when you're running a supersonic speed.

 

 

An interesting idea -- thanks!