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Message no. 1
From: Stainless Steel Rat <ratinox@***.NEU.EDU>
Subject: Hypervelocity (was Re: Lone Star Sourcebook)
Date: Fri, 10 Jun 1994 13:18:43 -0400
>>>>> "Gian-Paolo" == Gian-Paolo Musumeci
<musumeci@***.LIS.UIUC.EDU>
>>>>> writes:

Gian-Paolo> What exactly _is_ the difference between hypersonic and
Gian-Paolo> supersonic rounds?

Supersonic is faster than sound. Hypersonic is faster still.

As I explained earlier, as velocity increases, the dynamics of air change,
acting more and more like a liquid as velocity increases. At Mach 1 (the
actual speed varies based on atmospheric conditions and altitude) air acts
like a liquid, not a gas, and the dynamics of the system rapidly change.
P-51D pilots discovered this when, while trying to pull out of power dives
they'd pull back on the stick, only to find that their aircraft would push
/deeper/ into the dive; pushing forward on the stick would pull them out.

Hypersonic is conveniently defined as Mach 5, 5 times the speed of sound at
current altitude and conditions. That's a point where air starts acting like
a solid. The actual speed can vary significantly depending on atmospheric
conditions.

--
Rat <ratinox@***.neu.edu> | "Carpe Joltem! (Seize the Caffeine)"
--Me
http://www.ccs.neu.edu/home/ratinox |
Message no. 2
From: Ivy Ryan <ivyryan@***.ORG>
Subject: Re: Hypervelocity (was Re: Lone Star Sourcebook)
Date: Fri, 10 Jun 1994 17:59:25 -0700
On Fri, 10 Jun 1994, Stainless Steel Rat wrote:

> >>>>> "Gian-Paolo" == Gian-Paolo Musumeci
<musumeci@***.LIS.UIUC.EDU>
> >>>>> writes:
>
> Gian-Paolo> What exactly _is_ the difference between hypersonic and
> Gian-Paolo> supersonic rounds?
>
> Supersonic is faster than sound. Hypersonic is faster still.
>
> As I explained earlier, as velocity increases, the dynamics of air change,
> acting more and more like a liquid as velocity increases. At Mach 1 (the
> actual speed varies based on atmospheric conditions and altitude) air acts
> like a liquid, not a gas, and the dynamics of the system rapidly change.
> P-51D pilots discovered this when, while trying to pull out of power dives
> they'd pull back on the stick, only to find that their aircraft would push
> /deeper/ into the dive; pushing forward on the stick would pull them out.
>
> Hypersonic is conveniently defined as Mach 5, 5 times the speed of sound at
> current altitude and conditions. That's a point where air starts acting like
> a solid. The actual speed can vary significantly depending on atmospheric
> conditions.

Hmmm, that would put "hypervelocity" rounds into the 5650 fps range. I
don't think anything's that fast. At least, nothing I've ever heard of.

>
> --
> Rat <ratinox@***.neu.edu> | "Carpe Joltem! (Seize the
Caffeine)" --Me
> http://www.ccs.neu.edu/home/ratinox |
>
Ivy
Message no. 3
From: Stainless Steel Rat <ratinox@***.NEU.EDU>
Subject: Re: Hypervelocity (was Re: Lone Star Sourcebook)
Date: Sun, 12 Jun 1994 20:10:28 -0400
>>>>> "Ivy" == Ivy Ryan <ivyryan@***.ORG> writes:

>> Hypersonic is conveniently defined as Mach 5, 5 times the speed of sound
>> at current altitude and conditions. That's a point where air starts
>> acting like a solid. The actual speed can vary significantly depending
>> on atmospheric conditions.

Ivy> Hmmm, that would put "hypervelocity" rounds into the 5650 fps range.
Ivy> I don't think anything's that fast. At least, nothing I've ever heard
Ivy> of.

Space shuttles and railgun slugs. There are a few AIMs out there that are
that fast, too.

:)

--
Rat <ratinox@***.neu.edu> | "I have no idea what that meant."
http://www.ccs.neu.edu/home/ratinox | --Dot Warner
Message no. 4
From: Ivy Ryan <ivyryan@***.ORG>
Subject: Re: Hypervelocity (was Re: Lone Star Sourcebook)
Date: Sun, 12 Jun 1994 20:54:18 -0700
On Sun, 12 Jun 1994, Stainless Steel Rat wrote:

> >>>>> "Ivy" == Ivy Ryan <ivyryan@***.ORG> writes:
>
> >> Hypersonic is conveniently defined as Mach 5, 5 times the speed of sound
> >> at current altitude and conditions. That's a point where air starts
> >> acting like a solid. The actual speed can vary significantly depending
> >> on atmospheric conditions.
>
> Ivy> Hmmm, that would put "hypervelocity" rounds into the 5650 fps
range.
> Ivy> I don't think anything's that fast. At least, nothing I've ever heard
> Ivy> of.
>
> Space shuttles and railgun slugs. There are a few AIMs out there that are
> that fast, too.
>
> :)

Wow!?! Uh, Rat, What'za AIM (Other than the American Indian Movement)?
Anti-Intruder Missile?

> --
> Rat <ratinox@***.neu.edu> | "I have no idea what that
meant."
> http://www.ccs.neu.edu/home/ratinox | --Dot Warner
>
Ivy
Message no. 5
From: Stainless Steel Rat <ratinox@***.NEU.EDU>
Subject: Re: Hypervelocity (was Re: Lone Star Sourcebook)
Date: Mon, 13 Jun 1994 11:01:07 -0400
>>>>> "Ivy" == Ivy Ryan <ivyryan@***.ORG> writes:

>> Space shuttles and railgun slugs. There are a few AIMs out there that are
>> that fast, too.

Ivy> Wow!?! Uh, Rat, What'za AIM (Other than the American Indian Movement)?
Ivy> Anti-Intruder Missile?

Close. AIM is Air-to-Air Missile, AGM is Air-to-Ground Missile.

--
Rat <ratinox@***.neu.edu> | "It is a proud and lonely thing to be a
http://www.ccs.neu.edu/home/ratinox | Stainless Steel Rat."
this space intentionally left blank | --"Slippery" Jim DiGriz
Message no. 6
From: Chris Yang <cyang@*****.UBC.CA>
Subject: Re: Hypervelocity (was Re: Lone Star Sourcebook)
Date: Mon, 13 Jun 1994 14:30:26 -0400
> >>>>> "Ivy" == Ivy Ryan <ivyryan@***.ORG> writes:
>
> >> Hypersonic is conveniently defined as Mach 5, 5 times the speed of sound
> >> at current altitude and conditions. That's a point where air starts
> >> acting like a solid. The actual speed can vary significantly depending
> >> on atmospheric conditions.
>
> Ivy> Hmmm, that would put "hypervelocity" rounds into the 5650 fps
range.
> Ivy> I don't think anything's that fast. At least, nothing I've ever heard
> Ivy> of.
>
Actually, I did see an article a couple of years ago, mostly speculating
on weapons of the future. Two of the weapons included were the HK G11,
which had a muzzle velocity of about 3000 fps (if memory serves correctly)
and the Steyr ACR prototype which fired what looked like a finned nail
at velocities of around 5000 fps.
The size of the cartridge was quite large, since it had to accomodate the
fins on the "nail".

A prototype gun, I haven't heard anything about it since.

Chris

----------------------------------------------------------------------
Chris Yang cyang@*****.ubc.ca
University of British Columbia cyang@******.ubc.ca
Dept of Botany
Message no. 7
From: Adam Getchell <acgetche@****.UCDAVIS.EDU>
Subject: Re: Hypervelocity (was Re: Lone Star Sourcebook)
Date: Mon, 13 Jun 1994 12:54:17 -0700
On Fri, 10 Jun 1994, Stainless Steel Rat wrote:

> Supersonic is faster than sound. Hypersonic is faster still.
>
> As I explained earlier, as velocity increases, the dynamics of air change,
> acting more and more like a liquid as velocity increases. At Mach 1 (the
> actual speed varies based on atmospheric conditions and altitude) air acts
> like a liquid, not a gas, and the dynamics of the system rapidly change.

The Mach number is the ratio of speed to the speed of sound
through the medium, and is a function of pressure, temperature, and density.
Mach number is also the ratio of viscous stress to shear
stress. But in any case, there is no fundamental difference between the
behavior of a "liquid" versus the behaviour of a "gas" from the
viewpoint
of Fluid Mechanics.
A "Fluid" is anything which cannot sustain a shear stress, which
includes gasses, liquids, and plasmas. The only differences among the
three are viscosity, density, and in the case of a plasma there are a few
other properties. But there is no speed regime where fluids behave as
solids.
The story Rat was relating about P-51s occurs because of the
information transfer due to a sonic shock wave. A disturbance in a sonic
flow can travel upstream to "communicate" the information; a supersonic
shock cannot. Therefore, one gets the counterintuitive case where a
nozzle of decreasing area will accelerate a sonic flow, but *decelerate*
a supersonic flow.
As a side note, no propeller-driven aircraft can break the sound
barrier. No such thing as a Mach 1+ Helo, Osprey, or P-51.

> Hypersonic is conveniently defined as Mach 5, 5 times the speed of sound at

Hypersonic and transonic are nearly synonymous, characterized by
extreme turbulence and very thin boundary layers. At these flight
levels, the smallest disturbance creates radical effects on aerodynamics.
It has been theorized that a hypersonic bullet striking a human
body will generate a sufficiently strong pressure wave to stop the
heart. This wave is present in lower velocity rounds, but the elasticity
of the bodily tissues dampens the effect.
Also note the top speed in the atmosphere is something like 6800
meters per second, because anything faster than that will burn up due to
atmospheric friction. Hypersonic planes fly in the reaches of the upper
atmosphere (~.01 sea level density and pressure), and are made of
advanced materials capable of withstanding the heat stresses.

> --
> Rat <ratinox@***.neu.edu> | "Carpe Joltem! (Seize the
Caffeine)" --Me
> http://www.ccs.neu.edu/home/ratinox |
>

+-------------+---------------------------------------------------------------+
|Adam Getchell|acgetche@****.engr.ucdavis.edu | ez000270@*******.ucdavis.edu |
| acgetchell |"Invincibility is in oneself, vulnerability is in the opponent"|
+-------------+---------------------------------------------------------------+
Message no. 8
From: Gian-Paolo Musumeci <musumeci@***.LIS.UIUC.EDU>
Subject: Re: Hypervelocity (was Re: Lone Star Sourcebook)
Date: Mon, 13 Jun 1994 17:28:53 -0500
ex000260/Adam Getchell:
> and are made of advanced materials capable of withstanding the heat stresses.

...titanium alloys. Except that Ti crumples at high temperatures like a
potato chip: the SR-71, which is a titanium composite aircraft, has prestressed
wrinkles so that the wings won't deform in flight.
_____________________________________________________
G. Musumeci
Message no. 9
From: Adam Getchell <acgetche@****.UCDAVIS.EDU>
Subject: Re: Hypervelocity (was Re: Lone Star Sourcebook)
Date: Mon, 13 Jun 1994 16:13:13 -0700
On Mon, 13 Jun 1994, Gian-Paolo Musumeci wrote:

> ...titanium alloys. Except that Ti crumples at high temperatures like a
> potato chip: the SR-71, which is a titanium composite aircraft, has prestressed
> wrinkles so that the wings won't deform in flight.

So far the best stuff seems to be Carbon-Carbon (phenolic-epoxy),
which we were considering for our rocket nozzle design. Our design wall
temps are 3000 F, although it can take up to 5000. The elevated
temperature stress level is highly dependent upon the orientation of the
fibers, though.
The exact composition of the Carbon-Carbon seems to be
Aerojet-proprietary, however. Guess I don't blame them.
We eliminated metals right off. Too much weight penalty, not
enough heat capacity. Plus I think carbon-carbon's cheaper than
machining titanium.

> G. Musumeci

+-------------+---------------------------------------------------------------+
|Adam Getchell|acgetche@****.engr.ucdavis.edu | ez000270@*******.ucdavis.edu |
| acgetchell |"Invincibility is in oneself, vulnerability is in the opponent"|
+-------------+---------------------------------------------------------------+
Message no. 10
From: Ivy Ryan <ivyryan@***.ORG>
Subject: Re: Hypervelocity (was Re: Lone Star Sourcebook)
Date: Mon, 13 Jun 1994 11:51:52 -0700
Hi, Rat,

Hmmm, and here I always thought that Air-to-Air Missiles were acronymed
as AAMs. Live and (occasionally) learn.

Thanks,

Ivy (They're changin' them faster than I can remember them!)
Message no. 11
From: Stainless Steel Rat <ratinox@***.NEU.EDU>
Subject: Re: Hypervelocity (was Re: Lone Star Sourcebook)
Date: Tue, 14 Jun 1994 10:01:30 -0400
>>>>> "Ivy" == Ivy Ryan <ivyryan@***.ORG> writes:

Ivy> Hi, Rat,
Ivy> Hmmm, and here I always thought that Air-to-Air Missiles were
Ivy> acronymed as AAMs. Live and (occasionally) learn.

AIM and AGM are the prefixes used in missile designations, like AIM-54
Phoenix. I think they use AIM instead of AAM to avoid confusion with AAA
(anti-aircraft artillery).

--
Rat <ratinox@***.neu.edu> | "Character is what you are in the
dark."
http://www.ccs.neu.edu/home/ratinox | --Lord John Whorfin
Message no. 12
From: Marc A Renouf <jormung@*****.UMICH.EDU>
Subject: Re: Hypervelocity (was Re: Lone Star Sourcebook)
Date: Wed, 15 Jun 1994 09:05:55 -0400
But how come medium-range air-to-air missiles like the sparrow are
designated AMRAAM, with the last three letters denoting "air-to-air-missile"?

On Tue, 14 Jun 1994, Stainless Steel Rat wrote:

> >>>>> "Ivy" == Ivy Ryan <ivyryan@***.ORG> writes:
>
> Ivy> Hi, Rat,
> Ivy> Hmmm, and here I always thought that Air-to-Air Missiles were
> Ivy> acronymed as AAMs. Live and (occasionally) learn.
>
> AIM and AGM are the prefixes used in missile designations, like AIM-54
> Phoenix. I think they use AIM instead of AAM to avoid confusion with AAA
> (anti-aircraft artillery).
>
> --
> Rat <ratinox@***.neu.edu> | "Character is what you are in the
dark."
> http://www.ccs.neu.edu/home/ratinox | --Lord John Whorfin
>
Message no. 13
From: Chris Ryan <chrisr@****.QUT.EDU.AU>
Subject: Re: Hypervelocity (was Re: Lone Star Sourcebook)
Date: Thu, 16 Jun 1994 09:21:30 +1000
> On Tue, 14 Jun 1994, Stainless Steel Rat wrote:
>
> > >>>>> "Ivy" == Ivy Ryan <ivyryan@***.ORG> writes:
> >
> > Ivy> Hi, Rat,
> > Ivy> Hmmm, and here I always thought that Air-to-Air Missiles were
> > Ivy> acronymed as AAMs. Live and (occasionally) learn.
> >
> > AIM and AGM are the prefixes used in missile designations, like AIM-54
> > Phoenix. I think they use AIM instead of AAM to avoid confusion with AAA
> > (anti-aircraft artillery).

I think AIM really means: Air Intercept Missile...

Chris

Further Reading

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