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ZL2TZE > SAREX 11.12.00 10:48l 186 Lines 7004 Bytes #999 (0) @ WW
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Subj: [sarex] MIR
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To : SAREX@WW
Mir's Deorbit Will Rain Down Wreckage;
But Where?
By Leonard David
Senior Science Writer, SPACE.com
WASHINGTON -- Russia is on track to crash its history-making Mir
space station into a huge, desolate zone
of South Pacific waters in late February. The deliberate ditching
of the Russian outpost will produce a sizeable
shower of hardware that will reach Earth's surface.
Yuri Koptev, head of the Russian Aviation and Space Agency
(Rosaviacosmos), stated last month that Mir's
deorbit would take place in the February 26-28 time period.
Mir has been a long time fixture in space. The central core of the
Russian station was hurled into orbit on
February 20, 1986.
But now, just a little more than 15 years to the day, it will be
lights out for the complex of large docked
modules, sets of solar panels, antennas and various pieces of
attached equipment.
If all goes as planned, over 130 tons (118,182 kilograms) of space
hardware will be carefully nudged out of
orbit and sent screaming through Earth's atmosphere.
Space debris experts project that as much as 50 tons (45,455
kilograms) of Mir leftovers are likely to smack
into the ocean after surviving the fiery fall from grace.
Goodbye salute
For NASA's chief, Daniel Goldin, it's goodbye to Mir, hello
safety.
"As far as we are concerned, we salute the decision that the
Russian government made. It's a very reasonable
decision," Goldin told SPACE.com.
Goldin said that at NASA, safety is of the utmost priority.
Protecting the general public first, then the astronauts,
followed by workers on the ground and, finally, the assets.
"They are going right to the priorities we set. Protect the
general public. That is more important than anything
else -- I salute their decision," Goldin said.
Abandon in place
Congressman James Sensenbrenner (R-Wisconsin), chairman of the
science committee in the House of
Representatives, believes it's high time to lower the boom on
keeping Mir alive.
"I had hoped the Mir would have been brought down a couple of
years ago. That's when it was obviously used
up. The Russian's actually abandoned it and its modules were
slowly depressurizing. Then it became a political
issue in Russia, and an issue of national pride," Sensenbrenner
told SPACE.com.
The U.S. lawmaker said one of the things hurrying the demise of
Mir is the fact that two other technological
marvels -- Russia's submarine, the Kursk, and the giant television
tower in Moscow -- ended up having
accidents within a few weeks of each other last summer.
"I think that if something like that happened to Mir, and a bunch
of people were killed, that would be another
blow to Russia's national pride, one that the Russian government
and their president would not want to have to
explain," Sensenbrenner said.
Real rocket science
Russia's disposal of Mir early next year will get an electronic
helping hand courtesy of the U.S. military's global
space surveillance tracking network. In addition, aircraft and
mariner alert notices are to be issued via both
U.S. and Russian channels.
But in some government circles, there is concern about too much
American involvement. In the event that Mir's
reentry goes awry, perhaps careening into a populated area, would
the United States be held partly accountable for a botched job?
"Mir's health is pretty good. So I don't see any reason why they
can't do it successfully," said Joseph Loftus,
assistant director for engineering in space and life sciences at
NASA's Johnson Space Center in Houston, Texas.
"Clearly, this is a Russian responsibility. They've acknowledged
that it is their responsibility," Loftus said. "Keep
in mind, these guys are good. They have been doing reentry
exercises for years. This is not some arcane art. It
is rocket science, but it's understandable," he said.
Loftus said that a formal and final government declaration to dump
the Mir is forthcoming. "They treat these
kinds of things like we treat base closings. So there's a
commission and going through their protocol," he said.
The fact that the Mir space base is being downed -- with its core
segment having been in orbit around 15 years
-- is of special meaning to Russian engineers, Loftus said. Those
segment's longevity is the criteria by which
engineers measure hardware for use on the International Space
Station, he said.
Slam dunk
Tracking data shows that Mir can remain in orbit until at least
the beginning of March.
The Russian plan as it is now sketched out is to loft in late
January a Progress M1 craft, brimming with
propellant. It will join a Progress 243 vehicle already docked to
Mir.
Over several days, "phasing burns" of Progress engines will
position the Mir for the final last blast.
On deorbit day, starting somewhere over Africa, Progress rocket
motors are to ignite and burn for some 800
seconds. Mir ground controllers will be tracking the doomed
station as it flies over Russia one last time.
As the critical firing ends off the east coast of Russia, Mir will
be on a descending trajectory that will lob it well
clear of Australia, New Zealand, the Marquesas Islands and other
populated oceanic terra firma.
The splashdown zone for Mir is huge -- about 3,726 miles (6,000
kilometers) long and 124 miles (200 kilometers) wide.
"By the time things start hitting the ocean, they'll be
essentially south of everything. It's as good a place as you
are going to find. There are no islands, no air or ship traffic,"
NASA's Loftus said.
Russian roulette
Odds are good that things will go smoothly for Mir's swan dive.
On the other hand, it might not be all smooth sailing. "I think
the major uncertainty is how Mir itself is going to
respond. It's an old system and [has] been up there a long time,"
said William Ailor, director of The Aerospace
Corporation's Center for Orbital and Reentry Debris Studies in El
Segundo, California.
Given the complicated structure of Mir, there is no telling how
the orbiting lab might respond during its breakup,
Ailor said.
Another uncertainty, Ailor said, is just how turbulent Earth's
atmosphere might be on deorbiting day. Solar
activity could mean larger aerodynamic forces acting on Mir,
causing the station to become unstable.
If so, then Mir takes on a fate that mirrors the old adage: "What
does a 500-pound gorilla do? Anything it wants to."
"If Mir goes unstable, then it's a random process after that. It
will come down where ever it wants to," Ailor said.
But not too worry. No need to run out and buy anti-space debris
hard hats.
"Even if the Russians can't control Mir, there's a lot of water
down below. Three-quarters of the Earth is
covered by water. So chances are it'll hit in the water, and
[there's] one-chance-in-four Mir will hit land," Ailor said.
"There's plenty of open space," Ailor said. "That's why we've not
had anybody actually get hurt, even though
we have about 100 reentries a year of major items," he said.
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