SpaceShipOne in outer space video

I am having difficulty with this statement to be honest.

I do not have a book in front of me to challenge you but I do know from running many computer programs on reentry vehicles that mach speed varies with altitude (pressure).

Either the models are wrong or you are wrong.

Rather than claim one, I invite the reader to find out should it be important to their profession or project.

Jerry

It is a function of temperature, not entirely dependent on temperature. It is also a function of pressure.

Jerry

ie pressure or density.

Indeed.

Well, I don't know about the models, but I know I'm right. So either the models are wrong or you misinterpreted them.

Specific heat.

Would that be muggy, smuggy, or sultry?

Steven is correct as far as his assumption that air obeys the ideal gas law goes. The NASA site that calculates the speed of sound as a function of altitude is based on a complex relationship of temperature and altitude. Air is not a perfect ideal gas, but it is close enough for anything I do at typcial pressures and temperatures. Ideal gases do not liquify at cold temperatures or high pressures or combinations thereof. So if you want enough accuracy to satisfy NIST, there are other variables, but for the rest of us temperature works just fine.

So you're saying that regardless of what's dissolved or suspended in the gas (atmosphere), or what the composition of the gas is, the speed of sound remains dependant only on it's temperature.

The mere fact you are standing by your convictions and are citing links and math indicates I need to rethink my position. Thanks for being the first in years on rmr to make me think that.

Jerry

"Truth exists. Only lies are invented."

- Georges Braque

"One person's sacred cow is another's hamburger."

- Celeste Dolan Mookherjee

"People want change, but they don't want it once they get it. :("

- Jeff Vincent

You're welcome.

no only on its density.

temperature is indirect only.

Chris Taylor

because it has a different DENSITY down here than it does up there.

in the SAME material pressure and temperature do not effect speed of sound. it effects DENSITY which then effect speed of sound.

at least that is what I was taught :-)

"Steven P. McNicoll" wrote in news:Mcsrc.17507$ snipped-for-privacy@newsread2.news.atl.earthlink.net:

Steven,

Outstanding information, thank you!

Chuck Mies KLOUDBusters, Inc.

Prove it.

No, you have it backwards. At the same temperature, the speed of sound will be the same (in a given medium such as air) at widely different densities. For example, consider the following values from standard atmosphere data:

Altitude Density Temp SofS (meters) (g/m^3) deg. C m/sec

-------- ------ ------ ---- 5000 736 -17.5 320

The density is many times lower at 41500 meters, but the speed of sound is about the same as at 5000 meters, because the temperature is the same. At an intermediate value of density at 15000 meters, the speed of sound and the temperature are both noticeably lower than at the higher or the lower altitude. (Source of the data was the Standard Atmosphere Computations web page at

-dave w

Awww, cut it out. Yer makin' me blush!

NOPE! It's only EXACTLY the same in an ideal gas. Air has a small deviation from ideality.

Any physics book will give the result for an ideal gas. Air has a very small veviation from ideal gas behavior, so small it's normally ignored.

The math is straight forward, but it's still hard to conceptualize. The atmosphere has many components and each component can vary. So regardless of the percentages of gasses in the atmosphere, like CO, CO2, O2, O3, and regardless of the dissolved water, the speed of sound remains constant. These constituents change the density, but do not change the speed of sound.

Likewise, the speed of sound is the same at the north pole at sea level at -60F, as it is on top of mount Everest at -60F. Although the air is much denser at the north pole, the math says that the speed of sound is the same.

Right?

At Smoke Creek we used to fly mach rockets over our heads so we could "feel the boom". Perhaps that strategy could be used to get more proximate reading of shock velocities.

Jerry

Safety is purely optional.