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Fast Flashing 2004-021B



 
 
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  #31  
Old July 6th 04, 03:44 PM
Paul Henney
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Default Fast Flashing 2004-021B

The slowing of the tumble is actually more to do with a conductor (the
rocket) rotating and moving in a magnetic field (the earths) and slowing
due to hysteresis effects..basically an induced current makes the rockets
tumble slow down over time.


pj



"William R. Thompson" wrote in message
...
PZeller66 wrote:

If the Zenit-2
upper stage has been strengthened since then, it might not happen
again; on the other hand, it gives me a reason to keep watching
04-021B


That's a really fascinating idea, Bill. Thanks, it gives me more

reason to
track it as well!


I looked at the sites Ed Cannon posted (thank you, Ed!) and compared
that against the debris lists on heavens-above. All of the Zenit-2s
seem to shed some debris: the covers over four solid separation
rockets. About a third of all Zenit-2s seem to have generated
more debris than this, so there's a fair chance that something may
happen.

If my calculations are correct, debris will be shed at a maximum of
25 m/sec (about 60 mi/hr). That doesn't lead to a major change
in orbit. Depending on the direction the junk flies off at,
the debris's new orbit will lower its perigee/raise its apogee by up
to 50 km, or change its inclination by about a fifth of a degree.

If there's a major bit of debris shed, I'd expect the booster's tumble
to slow as the debris carries off some momentum.

Okean O (1999-039B) (25861) was an eye-catcher soon after launch. I

was able
to see it just three weeks after it was launched in 1999, and it was

flashing
like a strobe light! I went out to observe it after reading about it on

H-A. I
sort of fell away from satellite observing for a while after that summer

and
didn't observe it again until the spring of 2001. I saw it shining with

a
steady brightness on that pass, and on eight or nine passes since then.

Can such a rapid tumble in an orbiting rocket stop after less than two

years?
Or was I just catching this object at the wrong orientation every time

and
missed any kind of flash period? I've always wondered this.


I don't know how long it takes the tumblers to slow down; I think
it depends on several factors--their size and mass, and the
intensity of the Earth's magnetic field. As I understand it, magnetism
is the major factor in slowing a satellite's tumble; the spin sets up
eddy currents in the object.

--Bill Thompson



  #32  
Old July 6th 04, 05:02 PM
William C. Keel
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Default Fast Flashing 2004-021B

Paul Henney wrote:
The slowing of the tumble is actually more to do with a conductor (the
rocket) rotating and moving in a magnetic field (the earths) and slowing
due to hysteresis effects..basically an induced current makes the rockets
tumble slow down over time.


Had an interesting run-in with one of these in the summr of 2000.
I'd been following the SL-16 stage of the month visually from
home for a while. Then I got data from a CCD mosaic imager at the
Kitt Peak 4-meter telescope. In a 3-night period looking at
a single field far to the north, we got not only that SL-16
but an older one transiting the 0.5-degree field. I have a really
good light curve for that first one...

The stacked images went into the background material for a Hubble/Chandra/
Kitt Peak/Gemini/VLA press release. The stacking of multiple exposures
didn't quite erase all traces of one of the booster trails; looking carefully
at the big KPNO mosaics linked from
http://www.astr.ua.edu/keel/c153/
(under Color Composite Images of Abell 2125) will show it in
the blue filter, where the
combining algorithm did not reject slightly high pixels.

Bill Keel
  #33  
Old July 6th 04, 05:02 PM
William C. Keel
external usenet poster
 
Posts: n/a
Default Fast Flashing 2004-021B

Paul Henney wrote:
The slowing of the tumble is actually more to do with a conductor (the
rocket) rotating and moving in a magnetic field (the earths) and slowing
due to hysteresis effects..basically an induced current makes the rockets
tumble slow down over time.


Had an interesting run-in with one of these in the summr of 2000.
I'd been following the SL-16 stage of the month visually from
home for a while. Then I got data from a CCD mosaic imager at the
Kitt Peak 4-meter telescope. In a 3-night period looking at
a single field far to the north, we got not only that SL-16
but an older one transiting the 0.5-degree field. I have a really
good light curve for that first one...

The stacked images went into the background material for a Hubble/Chandra/
Kitt Peak/Gemini/VLA press release. The stacking of multiple exposures
didn't quite erase all traces of one of the booster trails; looking carefully
at the big KPNO mosaics linked from
http://www.astr.ua.edu/keel/c153/
(under Color Composite Images of Abell 2125) will show it in
the blue filter, where the
combining algorithm did not reject slightly high pixels.

Bill Keel
  #34  
Old July 6th 04, 05:20 PM
Alexander Avtanski
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Posts: n/a
Default Fast Flashing 2004-021B


William R. Thompson wrote:
[ ... ]
I spotted it again less than an hour ago, in clear skies. The
flashing is still impressive.

--Bill Thompson


I saw it yesterday and could not detect any flashing. I'll
try again when I have a favorable pass a couple of days from
now.

- Alex

  #35  
Old July 6th 04, 05:20 PM
Alexander Avtanski
external usenet poster
 
Posts: n/a
Default Fast Flashing 2004-021B


William R. Thompson wrote:
[ ... ]
I spotted it again less than an hour ago, in clear skies. The
flashing is still impressive.

--Bill Thompson


I saw it yesterday and could not detect any flashing. I'll
try again when I have a favorable pass a couple of days from
now.

- Alex

  #36  
Old July 7th 04, 07:27 AM
William R. Thompson
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Posts: n/a
Default Fast Flashing 2004-021B

Alexander Avtanski wrote:

William R. Thompson wrote:
[ ... ]
I spotted it again less than an hour ago, in clear skies. The
flashing is still impressive.


I saw it yesterday and could not detect any flashing. I'll
try again when I have a favorable pass a couple of days from
now.


Lately it's started to make two nightly passes for my location.
The first is almost overhead; the flashing is hard to detect then,
until it's well past its apex.

The second pass is made about two hours before dawn, with the bird
fairly low in the west. Then the flashing is much easier to
observe. I think that 04021B is in a flat spin, so that when
it's overhead its apparent surface area doesn't change much, but
from an angle the geometry changes from end to side.

--Bill Thompson
  #37  
Old July 7th 04, 07:27 AM
William R. Thompson
external usenet poster
 
Posts: n/a
Default Fast Flashing 2004-021B

Alexander Avtanski wrote:

William R. Thompson wrote:
[ ... ]
I spotted it again less than an hour ago, in clear skies. The
flashing is still impressive.


I saw it yesterday and could not detect any flashing. I'll
try again when I have a favorable pass a couple of days from
now.


Lately it's started to make two nightly passes for my location.
The first is almost overhead; the flashing is hard to detect then,
until it's well past its apex.

The second pass is made about two hours before dawn, with the bird
fairly low in the west. Then the flashing is much easier to
observe. I think that 04021B is in a flat spin, so that when
it's overhead its apparent surface area doesn't change much, but
from an angle the geometry changes from end to side.

--Bill Thompson
  #38  
Old July 7th 04, 07:43 AM
William R. Thompson
external usenet poster
 
Posts: n/a
Default Fast Flashing 2004-021B

Paul Henney wrote:

The slowing of the tumble is actually more to do with a conductor (the
rocket) rotating and moving in a magnetic field (the earths) and slowing
due to hysteresis effects..basically an induced current makes the rocket's
tumble slow down over time.


That's pretty much what I was trying to say. The eddy currents
in the rocket's metal parts convert the physical energy into waste
heat. There are more details about this in various physics textbooks;
Halliday & Resnick describe it in their chapter about Faraday's
Law, but I'm not enough of a mathematician to figure out how to
apply their equations to a satellite.

There's a physics-class demonstration in which two metal disks
are rotated through the gap in a C-shaped magnet. The serrated
disk spins easily, while the solid disk is rapidly slowed by
the induced currents.

--Bill Thompson
  #39  
Old July 7th 04, 07:43 AM
William R. Thompson
external usenet poster
 
Posts: n/a
Default Fast Flashing 2004-021B

Paul Henney wrote:

The slowing of the tumble is actually more to do with a conductor (the
rocket) rotating and moving in a magnetic field (the earths) and slowing
due to hysteresis effects..basically an induced current makes the rocket's
tumble slow down over time.


That's pretty much what I was trying to say. The eddy currents
in the rocket's metal parts convert the physical energy into waste
heat. There are more details about this in various physics textbooks;
Halliday & Resnick describe it in their chapter about Faraday's
Law, but I'm not enough of a mathematician to figure out how to
apply their equations to a satellite.

There's a physics-class demonstration in which two metal disks
are rotated through the gap in a C-shaped magnet. The serrated
disk spins easily, while the solid disk is rapidly slowed by
the induced currents.

--Bill Thompson
 




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