[meteorite-list] Fireball dynamics questions:

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Thu, 19 Feb 2009 20:50:47 -0600
Message-ID: <044301c99306$0925f860$6151e146_at_ATARIENGINE>

Eman (Comic Book Hero, sounds like..), and List,


Beaten to the punch, but I got numbers...


> What is the approximate maximum distance a
> ground observer can see fireballs over the horizon?

The curvature of the Earth is roughly 61cm per
kilometer of curvature. If your eyes were 183cm
high and standing on a perfectly spherical Earth,
the horizon would 3 kilometers away. Conversely,
if you can see an object three kilometers away,
it has to be at least 183cm off the ground at its
location.

If a fireball lights up at 80 km elevation, it's above
the horizon for locations up to 135 km (in ground
track) away in all directions. And of course, the
Earth isn't a perfect sphere; standing on a mountain
looking out over plains adds to your distance, and
so forth. And a faster object would light up higher
than 80 kilometers. 80 to 100 kilometers is the usual
"light-up" altitude.


> Speed of sound at sea level?

343 meters per second (1,125 ft/s), or 1,235 kilometers
per hour (767 mph) at GROUND LEVEL. In the Earth's
atmosphere, the most important factor affecting the speed
of sound is the temperature. Temperature and thus the
speed of sound normally decrease with increasing altitude.


> maximum altitude where the atmosphere dense enough
> to support the formation of sonic boom?

At very high speeds and altitudes the Mach cone does not
intersect the ground and so, no boom is heard. Booms are
a lower altitude phenomenon. Got no precise figures for
you, though...


Sterling K. Webb
-------------------------------------------------------------------------
----- Original Message -----
From: "Mr EMan" <mstreman53 at yahoo.com>
To: "metlist" <meteorite-list at meteoritecentral.com>
Sent: Thursday, February 19, 2009 5:28 PM
Subject: [meteorite-list] Fireball dynamics questions:



I am still trying to assemble a trajectory and terminus for the Kentucky
fireball of 13 Feb. Lots of sightings but nearly all are missing critical
data like azimuth.. duh. I need some facts/values and can't seem to find
them in the archives or my notes. My memory is not specific enough to use.
(Metric or English is fine, I can convert when I rewrite my tables)

1. What is the approximate maximum altitude where the atmosphere dense
enough to support the formation of sonic boom? Somewhere my mind says
32miles.

1a. Speed of sound at sea level? 1500 meters per second?

2. What is the approximate maximum distance a ground observer can see
fireballs over the horizon as limited by the curvature of the earth? my
memory also says 250 miles

3. What are the approximate maximum and minimum altitudes where a meteoroid
can incandesce? 130 down to 5 miles asl?

4. What is free fall maximum velocity assuming 0 cosmic energy remaining?
120 or 400mph?

5. To plot and publish results on google maps do I need to be a paying
member?

Bonus Points: anyone have a contact/office name in the FAA to access air
traffic Control radar tapes for a specific time and date? Anyone know the
name of the Canadian Academic that was getting downgraded USAF fireball
data?

Thanks,
Elton
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Received on Thu 19 Feb 2009 09:50:47 PM PST