 | | Expedition
7 Commander Yuri Malenchenko prepares a meal aboard the International
Space Station. |
No. 21
From:
Chris Thompson, Ridgewood, N.J., Age: 12
Question:
When I was watching the fireworks on the Fourth of July, I wondered
if the ISS crew could watch them from the Station. Can you? Thank
You.
Lu:
We were hoping to be able to, but as it turned out, our orbit was
such that we were passing over the United States on July 4th during
the daytime in the United States. And at nighttime our orbit had
shifted so that when we were around that longitude, we were over
South America, and we could say that we did not see any fireworks
over South America on July 4th.
No. 22
From:
Chris Paget, London , England, Age: 24
Question:
I've just been reading Ed's latest journal entry about orbits and
how the ISS orbit is tilted by 51.6 degrees. I understand why it
has to be tilted by at least the latitude of Baikonur, but why 51.6
degrees? According to my GPS receiver, I'm currently at 51.3664
degrees north, so I don't often get the chance to see the ISS come
overhead. Does your orbit ever change other than the minor tweaks
that you correct for?
Lu:
The inclination doesn't change much, and our altitude does vary
a little bit, and that's because ... orbital drag starts to bring
it down, and we occasionally boost it back up. It does shift, just
because of the natural recession of the orbit -- that's an effect
just due to the fact that the Earth isn't quite a perfect sphere.
So its orbit does shift slightly westward by about 20 minutes or
so a day. Those are the effects that we have here. We don't actually
ever adjust our inclination.
No. 23
From:
Emily Van Ark, Cambridge, Mass., Age: 26
Question:
Hi guys! I've enjoyed reading the "Greetings, Earthlings!" essays.
I'm a grad student studying marine geophysics, and I find myself
thinking that being up there on the ISS must be a bit like going
out to sea for a month to do research. I'm curious about what kind
of shifts you work -- 12 hours on and 12 off, 4 on and 8 off --
and what tasks you're supposed to accomplish when you're on duty.
I assume there's basic monitoring of the Station's status? What
else are you doing?
Lu:
What we do, is we have ... basically, we get up around 7 in the
morning, start actually official tasks usually around 8 -- sometimes
a little bit earlier -- and we run until about 7 at night. And we
do that five days a week, and on weekends we set sort of a half-day.
But the basic tasks that we do vary from day to day. There's always
sort of monitoring of the station status, and every day we have
things ranging from maintenance to experiments to interviews to
you-name-it. Like for instance, this week we also have robotic arm
operations and some work with troubleshooting a problem we had with
one of our spacesuits.
No. 24
From:
Jacob Thurman, Macomb., Ill., Age: 22
Question:
Ed Lu, I just read your letter from ISS about learning to "fly"
in a zero-gravity environment. You wrote about pushing off of walls.
Newton said that for every action there is an equal and opposite
reaction, which means that just as you push away from the wall,
the wall pushes away from you. Does this principle have any effect
on the Station? Could launching off of and crashing into walls cause
the Station to actually change course or attitude? If so, how do
you correct it?
Lu:
Yes, it does, but the Station weighs about 200 tons. It doesn't
move a whole lot. There is some effect, and we have accelerometers
onboard that can actually sense the fact that you've pushed off
of a wall. They're sensitive enough to feel that. But remember that
it doesn't actually move the Station around, because when you push
off of a wall you're pushing the Station in one direction while
you're flying in the other direction. But when you stop yourself
on the far wall, you stop yourself with the same amount of momentum,
so it actually ... takes out whatever you gave the Station at the
other end, so you can't really self-propel yourself here.
No. 25
From:
Ted Lee, Mountain View, Calif., Age: 35
Question:
Hi, Ed. I followed in your footsteps under Vahe Petrosian at Stanford
-- remember me? Do you get warnings about solar activity, and what
procedures do you take to remain safe from dangerous radiation and
particles?
Lu:
Truth is, we don't have a whole lot that we do differently and that's
because at our altitude that we orbit at, the radiation levels are
not really that high. But we do have some flight rules to minimize
the radiation if you're taking a spacewalk. We will shift the spacewalk
in time either forwards or backwards a little bit to avoid having
the orbit during the spacewalk going through an area called the
South Atlantic Anomaly, which is where the magnetic field of the
Earth dips a little bit, and so there's a little bit higher radiation
levels in that area.
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