Navigating on Mir
Michael Foale's keynote address at the 10th Anniversary Mathematica
Friday, June 19, 1998
first came across Mathematica back in about 1990, and I used it to
examine what would happen to an astronaut falling off a space station and
drifting away untethered, slowly. How would you solve the problem of chasing
after that person using orbital mechanics, to be efficient in your fuel use, and
to bring that person back?
That was my first encounter with Mathematica. I didn't know that
actually I would end up having to use it in space to solve my own operational
Once you have an idea of what the Mir looks like and you can understand some
of the Russian words, I'm going to jump into a Mathematica notebook and
show you the specific operational problem we had with my Russian crew after the
collision, when the Mir was thrown into a tumble and also depressurized.
I've flown on four space shuttle missions, the last of which took me to the
Mir. As an astronaut, you don't really solve problems like you do as a
physicist. You have to do them rather quickly and work on the fly.
I was launched there in 1997 on May 15. I hardly knew the crew because I had
spent the year-and-a-half previous to the launch with my family in Russia,
studying Russian and learning about the Russian spacecraft systems. Because this
was my fourth launch, I was already familiar with the space shuttle. I had
already done a spacewalk on a shuttle, I had flown in three different seats, in
three different roles, as part of the crew on the space shuttle -- so this
particular launch for me was not any big deal.
We took one day to get into space, to go to the Mir space station. The Mir
space station is a Russian station that's been flying for about twelve years. It
has made an enormous number of great accomplishments. It has conducted many
experiments, and many, many different nations have taken part.
The station consists of a number of modules, and the main piece -- the first
piece that was ever launched -- is called the base block. It was launched on a
large rocket back in, I think, 1986. And then this (second) piece was stuck on,
and (this module) has these large solar arrays that produce electrical power for
the station. The base also has solar arrays. There's a module on top and then a
science module, which is called Priroda (which means "nature" in
Russian) and we have a module called Kristall, which means crystal; and the
Spektr module, designed to do investigations of the atmosphere.
Each of these modules has about eighty cubic meters of living volume, or air
space. However, most of it is filled with equipment. The docking module was
launched in 1984 specifically to allow the shuttle to dock to Space Station Mir.
The crew I launched with was typically international, and (the poofy-haired
man on the screen) is me. I've aged since then. Mostly because of what I went
through. The shuttle crew included Charlie Precourt, an Air Force test pilot on
his third flight, the commander of the shuttle; Vasily Tsibilev, commander of
the Mir station at the time; and Jerry Linenger, whom I was replacing. He had
been on board for about four and a half months and he was like a mountain man
with long hair and a long beard. It was Ed Lu's first flight; he's a physicist.
Eileen Collins was the first female pilot on the shuttle and she was prepared to
command a mission in January 1999. There were Jean-Francois Clervoy, an ESA
astronaut from the European Space Agency, and Elena Kondakova, a Russian
cosmonaut flying for the second time. Until Shannon Lucid was in space,
Kondakova held the duration record for being in space. She was in space on the
Mir in 1995 for six months. I had actually seen her before from the space
shuttle on my previous flight, where we had rendezvoused, but not actually
docked, with the Mir station: she was in the window waving at me. I never at
that time imagined that I would be flying with Elena! And there was Carlos
Noriega, a Marine and a helicopter pilot. Finally, the Russian engineer for the
Mir station, Sasha Lazutkin, who works for the large factory that builds the
Soyuz rockets. This represents the cross-section of people you have on the
After I was settled in on the Mir, we quickly exchange handover briefs
between myself and Jerry Linenger. For a period of five days I basically was
drinking from a fire hose trying to figure about all of the things you do just
to live on the Mir. I knew the theory -- I knew all the procedures, all the
training -- but that's not the real thing in space. The real thing is where
they've actually put something, how this thing really works, where you plug the
shaver in, where you get water, how you get your food ready. I'd had classes in
that, but the way you actually do it in space is always rather different from
the training. And after five days -- and this was a particularly difficult
moment for me -- I saw the shuttle leaving.
However, I rapidly got into the task at hand on the Mir. Over the next three
or four weeks I started to get deeply involved in the experiments. My favorite
experiment was a greenhouse. Specifically, I planted a form of broccoli seed in
long cloth wicks that stayed wet from water pumped underneath. The seeds grew 50
percent up, 50 percent down -- there's no gravity in space, so they didn't know
which way to go. The light at the top would help pull them up by phototropism.
The goal of this experiment was to grow flowers from these plants. I would
"beestick" -- like bees on sticks -- by taking a matchstick along and
I'd do the buzz-buzz-buzz all the way along the row of flowers and pollinate
them along these rows. After another two weeks, lo and behold, seed pods
appeared. I harvested the seeds and got to replant them, producing the very
first broccoli, or anything else, grown in space. It was a first. But I'm a
physicist, you know, so what do I care? I just wanted to eat something.
One of the things you don't think about in space is that lights don't have
convection to keep them cool at the top. We have fans everywhere in a
spacecraft. You need to move the air to keep the CO2 moving
past the crewmen, to scrub the CO2, clean it,
and also add oxygen to it from the revitalization system. You also need to move
air past the electronics boxes to keep them cool. The bright lights would
overheat and burn out. Over many years, they've experimented to improve this,
and now they have a lot of fans. When I was harvesting the plants, I started
with the lights on. When the lights are on, the fan's on. What happens? All the
seeds go whssht! straight up through the fan and disappear somewhere into the
space station. So there were some losses.
There was an experiment proposed that Vasily Tsibilev (the commander) had
already participated in before I arrived. Jerry Linenger had told me,
"Mike, there's this experiment they've been doing, trying to dock a
Progress convoy vehicle to the station." The reason they want to do it is
that this antenna (which is like a radar guidance system) is being made in the
Ukraine and costs far too much money for the Russians to be able to buy it right
now. This financial pressure had forced the Russians to come up with a plan in
which they would attempt to dock manually.
A standard backup procedure is manual docking in the last few hundred meters
before the station. Antennae are used from about two or three kilometers away.
When the Progress is coming in rather fast -- at about ten meters per second --
it weighs seven tons. And all the guidance and control from those antennae are
used specifically to brake the Progress. Well, the experiment was set up so that
Vasily would undock this Progress, and it would back away from the station, fly
around for two days, going out for three kilometers -- before Vasily would bring
it back in manually. He'd been in space three months. He had trained on this
only twice, in the last week before his blast-off from Baikonur in Kazakhstan.
And this had not ever been worked out by any of the other cosmopilots either, in
terms of what was the best geometry, orientation, and methodology for the
A simple TV image was used to measure the rate at which we were closing in.
That's "black ground rush" to a parachutist. As you come in closer,
the image gets bigger, and you can try to use that to calculate what the speed
is while at the same time deriving a closing rate. Then you figure out the
docking, using a little joystick to fire the thrusters.
As you know from the media, this was a terrible mistake. It left the station
not mortally, but severely, wounded. The Progress basically impacted, we think
now, on this part of the solar array on the Spektr module, and then it bounced
and slowly floated away along the base block.
The Progress weighs seven tons. We think it collided at about three meters a
second. I was in the base block; I didn't see it at all. Sasha Lazutkin saw it;
he told me, in all haste, to go straight to the Soyuz escape craft, and as I was
passing into the node region of the Mir, I heard a big thump. Because I wasn't
touching the Mir, I didn't feel any shock. I was just lightly floating through
the node with my fingers on it, about ten seconds after the warning. And there
was this big kind of ker-thump. And I assumed the Progress had hit back on the
docking port, where it was meant to have stuck.
But it hadn't. It had hit the Spektr module. If we'd been strapped in, we'd
have all been shaken around. This is just the opposite of being on Earth, where
you're in a car and you're always supposed to strap in. Bash the space station,
and nothing happens to you because you're not in contact with the station -- an
interesting backwards twist.
The station was hit very hard by the Progress. The guidance control system
that uses momentum wheels -- gyrodynes, as they're called -- to spin and then,
in reaction, control the orientation of the station, lost control. They couldn't
handle that kind of knock. The whole guidance control system failed in the
station, at which point the station started to tumble in an arbitrary way, about
one degree a second. These solar arrays are always supposed to be pointing to
the sun. And of course they can't slowly rotate about their axis to track the
sun. We rapidly -- after the collision, in about three hours -- started to lose
So the station was totally quiet at night, and only woke up sometimes during
the day, when by chance some light would fall on this solar array. And my task
was to help Vasily and Sasha, who didn't know what to do in this particular
case, figure out what the orientation of the station was by looking out through
a window, to somehow stop the rotation of the Soyuz. And then, knowing where the
sun would be next orbit, try to reorient the station so that the arrays were in
an orientation perpendicular to the sun. The next problem was to maintain the
orientation by putting a spin on the station -- again firing thrusters out of
But this was with a station that had no power on it and with a Soyuz that's
not designed for moving stations around. If we had tried to rotate the station,
we'd have used up almost all of the return fuel on the Soyuz, and we would have
been unable to abandon the station if we were unsuccessful in doing this.
That was the jam we were in. This evolved over about thirty hours, with us
running from one window to the next, trying to figure out what the orientation
of the station was, and then looking at the stars -- you'd put your thumb up
against the window, watching the star move behind your thumb. I know my thumb
basically obscures -- at least my thumb, anyway -- about three moon-widths;
that's about one and a half degrees, outstretched. And so I could very roughly
and quickly, in a dark, totally powered-down station, figure out what the
angular rotation rates of the station were. Then I told Vasily what I thought he
should do in the Soyuz.
But here comes the trick: to get from the part of the station where I was
doing the measurements to the Soyuz, you have to go through a node. The node is
basically a six-faced cube, just like a die, and it has portholes in each
direction. The trouble is, as you go through, you have to go past these hatches,
and you twist; and the Soyuz was not actually lined up with the station, there
are 45 degrees. So we spent almost a whole orbit trying to work out what the
orientation of the Soyuz was in relation to the station -- and we had no
communication with the ground to help us, because we had no power.
We were successful; we stabilized the station, at which point Sasha Lazutkin
and I tied it up to the central node area, so that we could receive one of these
docking adapter caps and put it in place of the cap that we had put on the hole
of the Spektr module to keep the air from rushing out.
When we had the collision, we had a depressurization. The air rushed out.
Sasha and I, in about five minutes, had had to disconnect cables. Some were
powered and they sparked as we were cutting them; we quit cutting and
disconnected them manually. These were plugs about the size of your hand. We got
that cap in place in about ten minutes, it turned out. We had about 20 minutes
before we had to leave the station because the air was too thin for us to
After that event, a new crew came up to replace Sasha and Vasily. By that
time, the ground and the Russians thought that the crew I was with, the Mir-23
crew, were jinxed. A number of things had gone wrong in between this slide and
the last one; Sasha had gotten too tired one time and pulled a cable while
trying to reconfigure the inside of that node, and again caused a total
power-down of the station. But it was with some regret and sadness that I saw
that crew leave in the Soyuz spacecraft.
There's a suit inside the Soyuz called the Orion. It's different from the
U.S. spacesuit in that it has a door at the back, and it opens up, and you can
step into it and then close it up behind you. You can actually put the suit on
all by itself; it's rather a neat design. The next crew that came up -- Anatoly
Solovyev and Pavel Vinogradov -- had the task of entering into the Spektr module
in vacuum -- in spacesuits -- and reestablishing power from that module -- and
from the broken solar arrays -- to the rest of the station. While they were
doing this EVA into the Spektr module, I was inside the Soyuz spacecraft -- just
in case those guys had a problem and couldn't repressurize the node and get back
into the station.
If that had been the case, I would have had to either try to get them back
into the spacecraft -- putting air into the volume here where they might enter
-- or leave them basically dead on the station. That EVA went on for about six
hours, and Pavel managed to make up most of the power from the Spektr module
back to the rest of the station, which provided lifeblood for the station to
recover. That repair work is what this station is living on today.
I'd been in space about three and a half months by this time. This was my
rescue, and there was -- after the number of times that we had lost power --
that we started to have computer problems on the Mir. The computers -- which are
a 60s and 70s technology, NPN, PNP, cans, transistors -- were all overheating,
because the station was overloaded with this equipment behind the panels where
the air flow is supposed to keep the computers cool.
So it was only when the shuttle was fully docked and the crew had come on
board that I knew I was going home. Up to this point I was expecting only the
worst -- maybe another five months on the station, until my current Russian crew
would just quickly be ready to go home. But I was very relieved. David Wolf,
from Indiana, succeeded me.
Twice a day, we exercised. But in the last three weeks I was very seriously
running on a treadmill and then putting rubber bungees around my neck. This
pulls at about fifty pounds. And doing knee bends and squats, to try build up
the strength in my muscles and to keep the calcium from leaving my bones so I
wouldn't be too easily injured with fractures when I came back to Earth.
And leaving was kind of sad, but as I left the station, I thought,
"David, I don't really envy you, but you've got it now." And I left
him with Anatoly Solovyev and Pavel. And they did a great job; they basically
put the station back to rights since I left.
People could say I was the cause of it all.
THE MATHEMATICA NOTEBOOK
I'm going to show the Mathematica notebook now. The task was this:
when you lose attitude control on the station, what happens? The station,
low-powered, starts to tumble; then the solar arrays are no longer pointed
toward the sun; and then slowly the batteries of the station start to deplete,
because the solar arrays aren't charging the batteries. And then in about two or
three hours you have no power on the station.
Gyrodynes, the momentum wheels, are always acting, spinning at different
rates to change the orientation of the station very slightly. Once the station's
lost all its power, or the guidance and control system has failed, the gyrodynes
start to spin down, and that momentum gets transferred back into the station. It
spins in the opposite direction to the gyrodynes.
Lo and behold, because you have twelve gyrodynes all spinning and working
really well to do a nice job at holding the station in attitude, as the space
station loses control of those gyrodynes and the gyrodynes spin down, then the
space station picks up all of the angular momentum that was in the gyrodynes and
starts to spin in the opposite way -- and in an unpredictable way.
So my whole task was to basically try to figure out what the rotation was,
null it, establish an orientation, and then spin. But the problem with the
station is that it has unequal moments of inertia.
I remembered from my days in Cambridge that there were these things called
Euler's equations, which you use to describe a rigid body that has unequal
moments of inertia. So if you think of the Mir having an a-axis, a b-axis,
and a c-axis, there are unequal moments of inertia about those. When you
put a spin on the station, generally the spinners are not going to stay about
one of these axes, unless it's the eigenvector of the inertia tensor.
The problem is sufficiently complicated, at least for my intellect, and I
tried to solve this problem using Mathematica in orbit.
I started off basically with these matrices. I said, "What are the
rotation matrices about the three axes?" I use those because that's the
convention that's used by Euler. I must say -- this is no ping on Mathematica
-- but Mathematica does not implement Euler angles the way I was taught
them at Cambridge. Taking those matrices allows you to transfer from the
rotating body back to space. In Euler's equations -- if you look at the
definition of an inertia tensor -- the angular momentum J is just the sum of the
moment times the momentum of each particle.
The point here is that it's a tensor, and it combines with the angular
momentum vector in the rotating body frame to make the total angular momentum.
And only when it's the eigenaxis -- so you have lambda here -- do you actually
have a rotation that doesn't change to another axis. That, for me, as an
astronaut on the Mir, meant that if I could only find the eigenaxis of the
inertia tensor, and get us spinning about it, we'd stay stable and the arrays
would still point. That was my goal. But there is another trick in this, and
that is, if you have an irregular body with three unequal moments of inertia,
the middle axis of inertia is unstable. And it's not unstable in a precise
sense, but there's a momentum exchange between the other axes. You have to be
right on it -- infinitesimally close -- for it to remain there.
The Euler equations are solved (with) the highlighted equation in the body
frame, and then using those Euler matrices to transform it back to the space
frame. I knew these equations were what I needed to solve this problem. But
every time I set this up in Mathematica, we would lose power again. I
remember a time when I was setting these equations up, and the whole station
powered down, the laptop went dead, and I lost what I had done; and we were once
again, for thirty hours, charging around trying to get the station back into
shape again. I ended up resorting to what I had in space, which was zero
gravity, and making a model and spinning it.
I had built a model; you can take this notebook and produce a Mir model from
it using the Shapes package. This defines my axis system -- a-axis is the
base block axis; a cone is the Soyuz, as I'm sitting in it; and the
thrusters fire either up and down the c-axis, or they can fire
horizontally along the b-axis, but you can't do roll; and you can see
we'd be operating about the center of mass, which is where the node is on the
All the spins I put in the animation are as if the sun were at the top of the
page. We were always trying to spin about the horizontal, about the c-axis;
that was the whole goal. I was hoping the solar arrays would maintain a
perpendicular orientation as we rotated with the face towards the sun.
It turned out that the c-axis was the middle moment of inertia, which
is unstable; and so we did this flip-flop that actually reduced the power we had
and made it much more difficult for us. If -- and this was not the case -- we'd
been able to rotate in roll, about the a-axis towards the sun, and then
those solar arrays -- as long as they weren't totally shadowed by each other --
would have been able to generate power stably in that configuration. And the a-axis
is actually the smallest one of them. The a-axis I called about 1; the c-axis
is about 1.1, 1.2 in the package; and the b-axis is about 1.3. They're
pretty close to each other.
These moments of inertia are not well known by the ground control, because
the payload on board is being moved around. When Progresses come up and trash
leaves, things are being moved around, and they lose track of exactly where all
the stuff is on the station. With water moving around on board the station as
well -- the condensation on the walls, maybe seven tons of water moving about on
the walls -- it was very hard to know exactly what these moments were. But I did
figure out, from a number of attempts to do this, that the c-axis is,
indeed, the most unstable axis to use -- and each rotation is roughly twenty
minutes. But the arrays lost track of the sun, and we ended up upside-down in
relation to the sun. And then the cycle would continue. And this whole flip to
upright again, where the solar arrays are once again able to track perpendicular
to the sun, became the way we set it up. This cycle would last about eight or
You can see that this is not the ideal way to spin a station. There was just
enough energy -- in spite of this transition that was going on, where it flipped
upside down -- there was enough energy obtained by those arrays to let us do the
repairs over a thirty-hour period, reestablish the computers on the base block,
turn the engines on, stop the station dead, and then slowly rebuild the attitude
control and navigation platform.
MORE OF LIFE ON MIR
I'd like to show you more of what it's like to live on the station.
A video taken over a four-and-a-half-month period starts off with me arriving
in the U.S. from Russia, when I had just come from snow in Star City, about
thirty miles outside of Moscow in April -- still snow on the ground in April! --
to sunny Houston. And it was wonderful to come to Houston.
That was the whole point; I arrived in Houston for the terminal countdown
test, got myself fitted in the seat, got to know my crew a little bit better --
I happened to know them all personally, just in different situations, but now I
got to train with them. The first exercise I did with them was to train in a
tank. This is the tank we use to run away from a shuttle should it start to
become rather dangerous on the launch pad. The interesting thing about going out
to the launch pad is everyone else is leaving the launch pad.
After two hours sitting on your back, the shuttle lifts off. This is a very
violent moment -- the boosters are firing unevenly, and the vibration is
side-to-side -- and it's a very rough ride; it's knocking you back and forth --
I mean left and right -- about an inch or so in displacement. However, after two
minutes it gets quiet, and the main engines carry on for another six minutes;
the G's go up to about three G's, and you are finally free in
After a day, we saw the Mir coming up. We did a number of careful orbital
maneuvers to get to the Mir. Charlie Precourt, the commander, was flying it at
this time. He had a target on the docking adapter, on the right, to a TV camera,
which happened to go blurry at the moment we were docking, but he managed to
handle it nonetheless.
After we'd equalized the pressure between the vehicles, we could open up the
hatch, and we had a crew welcoming ceremony. I'm sure you've seen some of this
on CNN. I met with Jerry Linenger there, who, as I say, was very long-haired and
bearded. And this for me was a rather poignant moment; I'd said goodbye to my
family and my children -- a three-year-old and a six-year-old -- I wasn't going
to see (them) again for five months, and I was handing off to Jerry here.
A fire had taken place while Jerry had been on board the station. The oxygen
generator -- the candle, as it's called, that just burns up perchlorate -- had
really burned and produced a two-foot-long flame that threatened to melt the
hull of the ship. Jerry told me a lot of stories. In this picture, he's pointing
out the oxygen mask that he had to use during that fire. It uses a chemical that
produces oxygen while you breathe; it takes water -- the water acts as a
catalyst to produce oxygen and sucks up the CO2.
This picture is of a vibration isolation facility called Mim; it's basically
an active control system that floats your experiment and isolates it from any
bumps or knocks that the rest of the station might be imparting. I'm pointing to
a greenhouse glove box there; I could handle formaldehyde and other toxic
chemicals using that glove box.
This is a view inside the airlock of the station; it's now inaccessible
because of the leaking hatch, but... Oh, this is the potty; this is always of
great interest to some children. Jerry always gets shy using it. But here is a
gyrodyne, one of those spinning momentum wheels; and it's in a vacuum, with a
big gold disc inside it, and it's spinning. And it hums away, and it's very
loud. And as you go to the potty here, you get to sit there while the gyrodyne
is going "rrrrrrr" next to you. The worst thing is when you have a
power-down, and that potty doesn't work anymore.
We have exercise devices -- this is in the Spektr module. This is the module
where I started off sleeping. There's my sleeping bag, rolled up; I was a pretty
tidy fellow at that time. This is a little airlock which we used to put
experiments out into space. In the old days, the Russians used to jettison space
debris that way.
This is the view we had -- the last view I had -- of the station complex from
the shuttle, before we then -- the night before they were going to undock,
separate it, and close the hatches so that we could evacuate the space between
the shuttle and the Mir. The vestibule is what we call it. And you can see the
look of my face here, in the background; I'm pretty serious -- I'm contemplating
what's happening to me; I'm being left behind. And there's something about the
psychology of the American crew member that the Russian doesn't have to deal
with. The Russian always has his or her return vehicle docked; and at any time,
if things get bad, you can go home. But the Americans can't; they have to wait
for another shuttle to get launched.
Once Vasily had closed the hatch, he turned to me and said, "Michael,
now we're going to beat you." And this kind of brought to the fore all the
fears I had! But they didn't force me to get a haircut; I actually asked for it.
Vasily was a really good barber and cut my hair for me. I did a number of things
before the collision that I enjoyed: I relaxed, read the one Russian magazine we
had on board. This is Vasily sleeping; this is me drinking what I would say is
juice. And it has fascinating properties, and with good music in the background,
and good crewmates, you can really enjoy the physical properties of juice.
Something we did every day, as I mentioned, twice a day, was exercise. The
temperature there is about 86 to 90 degrees. We were incredibly hot. It's
because the batteries from the solar arrays are all near this area, the galley
area and the exercise area. I did a number of things, repairing equipment...
Working in space is always tricky because you have to do things serially -- you
have to put things down, organize yourself so that the screws don't float away,
the screwdriver doesn't float away, and you don't move away.
Something I saw in space that was very interesting was these very high-level
clouds -- way high up at the hundred-kilometer level -- that had never been
recorded before. These are the lenticular clouds up here. And they're layered
clouds -- I don't know what the source of the water is; no one does. I have
heard that there are theories that comets keep falling onto the Earth -- small,
tiny little comets, every day -- maybe that's the source of the water. And
they're in the polar regions. Anyway, (if) anyone here has an idea on that, I'd
be happy to hear.
Here's that greenhouse experiment I did where I would crush the seeds -- the
dried seed pods -- and then pick out the seeds with tweezers, and then place
them into the greenhouse. And here you see me placing them very carefully --
again on sticky tape -- and then transferring it to these wet wicks. See how
that seed was floating there? It's terribly fiddly -- it was very frustrating to
do -- but nonetheless I was called "Farmer Foale," because I did
produce some plants.
Surprisingly enough, this experiment was the one thing that did keep working,
even when we had power-downs for thirty days.
The film just cuts to the next crew coming aboard about a month and a half
later. In that in-between time, we had tried to do this internal EVA; but, as I
mentioned, we had a problem with another power-down, and so the ground decided
to have Anatoly -- who's a five-times-flown cosmo, the best cosmo they had --
come up and take over. They did bring up some vegetables, which were very
welcome. Food is definitely a major thing in your life, if it's different from
the usual daily fare.
The first thing they had to get ready for was that EVA inside. They put me up
through the hatch to the top of the little re-entry capsule into an area where
there's one window. And they had me taking this movie. And it was an incredible
privilege for me to do this, because I knew Pavel wanted to do it a lot. After
twenty minutes I was just on my own in the top of the Soyuz, photographing --
both with the Hasselblad and the video -- these shots. And there you see the
broken solar array. And this fly-around lasted about twenty minutes, and this
was about two or three days after the previous crew had left.
It was right after we docked, back to that docking port, that a computer
failed, and once again we went out of control and lost all power. And it was
then that I had my first discussion with Anatoly. I said, "Well, Anatoly, I
think I know what we should do here." And he said, "No. We will wait
for an order from Moscow." And I said, "Well, if we lose all power, we
may not be able to get the order from Moscow." But he said, "No, we
will wait until we speak to Moscow." Well, we did have enough power to call
Moscow, so he was right. And he did a superb job bringing the Progress that had
been undocked back to the station.
The next spacewalk was my turn. This walk was to go outside and carry this 300
pounds of what I call Tinkertoys or Lincoln Logs. It's a scaffolding to carry to
the Spektr module along this space crane -- which I was going to control
subsequently -- and place it on the Spektr module so that we could do repairs to
the solar array and try to finally seal it. The whole point of this spacewalk
was to set up a structure from which we could conduct the repair of the Spektr
At this point there were hopes -- on the Russian side -- that Spektr could be
repressurized and reused. When you have three hundred pounds of mass in your
equipment -- and it's just tethered lightly -- if it bumps into a solar array or
something it could damage it, so you move very slowly. Here Anatoly is at the
end of this crane -- it's sixty feet long -- and I'm controlling the bottom of
it from the base of the base block with my hand. It's just like a tank, if
you've ever -- well, maybe you haven't moved tank guns around, but... you've
seen it in the movies like I have. You crank it with the one hand to do pitch,
and you use the other hand to do azimuth. Now Anatoly is going to start digging
with a razor knife. Americans have a different approach to some of the things
that we do on spacewalks, in terms of safety, in that we are not given a razor
knife with our rubber spacesuit. But the point is that this was a very desperate
The insulation here is a form of cloth that thermally stabilizes the module
when it's normally running. Anatoly's task is to go in here and start cutting
this insulation with this razor knife. And you'll see it kind of floating about.
And I was watching it very carefully, because here I am sidling along with this
ring that I use to move up and down the crane. See all the loose material coming
out the side of the image here? He's basically deep in that hole he's cut,
trying to find the hull underneath to see if it's actually perforated.
The thing in his hand is not the knife, it's a camera. I'll show you some
views from that camera, which are extraordinary. That's the razor knife here,
and that's just a pure razor edge there (floating next to Anatoly's spacesuit).
I said, "Well, I don't want to take (a knife)." Anatoly said,
"You will take one. I have one, you have one."
So I had one on my arm, but I didn't take it out.... But in space you move
gently, and there's not much force; so, yes, you can touch things without
cutting them, I guess. The views now are coming from that camera that Anatoly
was using to look underneath the insulation, looking at the hull, to see what
was broken. The foil is shaking. I don't know why it's shaking; there's no air
of course, no wind.
A spacewalk is an extraordinarily beautiful thing to do. It's the reason why
I am still an astronaut, and want to fly again in space, and want to do more
space flights. I love this view. This is a fantastic view. At night the galaxy
is extraordinary to see. There are far more stars in the sky than even on a high
mountain in Colorado on a clear night. So I had a real treat, even though we
were again solving some pretty severe problems.
It happened to be the 850th anniversary of the foundation of Moscow, and
Anatoly and Pavel, the night before the EVA, had spent the whole night producing
that flag to show the ground controllers.
After all the excitement of the EVA and that activity, I started to wind
down, and my mood did change. With a lot of relief I saw the shuttle launched
and actually come up and successfully dock. It was only delayed about ten days.
Generally the shuttle crews that come up to Mir have been about six or seven
people, and they transferred about two to three tons of equipment each time. A
large amount of it has been water, specifically because at the moment the Mir
cannot recycle water very effectively. The water's not only used for drinking,
it's also used for oxygen production by electrolysis. One thing the shuttle does
before it leaves is to pump up the station with all the air and oxygen it's got
in its tanks. So the pressure was quite a lot higher than atmospheric pressure
by the time we closed the hatch on the Mir and left. I didn't know how I was
going to feel saying goodbye to Anatoly and Pavel here. I was sad to say goodbye
to them, but I was glad to go.
And in the final moment, with David Wolf on the other side of the hatch and
myself on the shuttle side, I felt I was back on American territory; I was
coming home. I had a big smile on my face, and I didn't mind the exercise I had
had to do to get ready for the landing.
The last vestiges of my Mir clothing were fleece-lined boots that I had used
for the whole five months. I used the same flight suit too for the whole five
months. We changed the underwear, though, every two days. And then I got those
boots; they keep the tops of your feet from getting worn. In your jersey you use
your feet to hold onto rails, with the top -- with feet going into the rail, and
you get blisters on the tops of your feet, not on the bottoms, and so those
boots helped protect my feet.
My previous landings -- three of them -- I'd been sitting up; I was an active
member of the shuttle crew. On this landing, I was a passive member of the
shuttle crew; I was on my back. And at one-third G -- the G's
build up progressively over about ten minutes from about nothing, of course, to
about two G's; and then they drop down to about one G, and then
again up to one-and-a-half as you come round in a circle that takes you into
landing. At the third-G mark -- I mention that, because that's what
Martian G is -- and I tried to sit up at one-third G for as long
as it lasted, to see what it would be like to go to Mars after a six-month
The biggest moment I had was about two hours after landing. I'd gotten rid of
most of my lunch, I think, and had all the tests done on me and was able to meet
I've tried to show you two things. One is what it's like to be a Mir
astronaut and go to the Mir station and live there and come back. But also, the
approach one can have as a physicist to solving some real life-threatening
problems. And in this case it was quite a treat for me to apply all of that
education, that I had been so lovingly given by my parents, in this situation.
ANSWERING QUESTIONS FROM THE AUDIENCE
Basically I went through this situation of us losing attitude control for one
reason or another -- computer failure, collision, whatever -- six times. The
first time it happened was the collision, and I didn't know the moment of
inertia at all then. But it was apparent in the evolution of the procedure with
the commander and telling him, "Okay, try firing a jet for three seconds to
the left, and we'll see what happens, and I will go to a window and watch what
happens," and I would watch that rotation develop. I mean, we were in a
dilemma. We just had to do something. And I said, "Something is better than
nothing." And we tried a general rotation, and we saw the effect of that.
And it turned out to be basically what we wanted -- having the solar array
directed toward the sun -- for a while. Well, it was in that first attempt that,
after three hours, having seen it stable -- it suddenly started to get -- the
coning -- it started to cone and do this [indicating coning motion with finger];
and I could see it was going to flip. And so I then knew -- well, just by
spinning books and things -- that that was the middle moment of inertia, and I
saw the effects I remembered from earlier days. That brought my attention to the
problem. So then I was thinking to myself, "What can you do to somehow
influence that flip so it doesn't happen again?" I was hoping that we could
fire a jet in the transition that would keep us pointed stably. I didn't solve
that problem. But, in an attempt to do that, I then found an old Mir model, that
had been sent up -- oh, maybe three years prior -- and it was in an old cupboard
type area of the Mir. Made of metal, very nicely made. It didn't have the right
modules on it, and two of the modules had been broken off and lost. And the
model was about this size. And so what I did was I took flashlights, and stuck
them on with duct tape onto the node -- there were all these things sticking out
-- and then I would spin the model. And of course in zero gravity you can do
that, right above the table.
I would blow on the Mir model to see what the effects of these torques would
do. In the end I just went for one initial setup, one initial rotation rate, and
then just took the flip as we've got it.
Now I'm going to tell you the painful Mathematica story. Forgive me,
Stephen. I had Mathematica with me; I owned it personally. It wasn't even
a copy that NASA had bought for me. And I had intended to work on tensor
calculus in all that free time that I was going to have. And I had it along with
my music CDs in my CD pack that NASA nicely made for me, in the Spektr module. I
also had it on the hard drive, installed on a laptop in the Spektr module.
When the collision happened, we rushed in there, disconnected the cables,
shut it off, and if I'd been smart enough, I'd have gone in there and gotten my Mathematica
CD before the air rushed out... but I didn't. I was more worried about the air
rushing out. We disconnected the cables, put the cap on, and then I thought,
"Oh... all my stuff's in there."
By that time, with the cap on, of course, the pressure dropped very fast in
that module and went to vacuum pretty quickly, within an hour. So then I was Mathematica-less,
which was a terrible condition to be in. I had to learn these things about
moments of inertia at that point. And so I was just working on the basis of what
I remembered. It was after recovery -- and recovery from the collision took
about thirty hours, and the most important thing to me at that time was getting
the module D -- the Kvant-2 -- to work, because that's where the toilet was. And
all we were focusing on was trying to get power onto the module that had the
Grim stuff, it really is. But after we regained our composure, had a hot
meal, and, week went by, I said to Vasily and Sasha, "You know, I think
that maybe we could do this better if this happened again." And they said,
"Oh, it will never happen again."
And I said, "I wish I could calculate, you know, exactly what kind of
impulse we can give during the flip to prevent that occurring. And it was that
point that I made a call to the ground for a Mathematica disk to be sent
to me. And, in fact when Wolfram received the call, a whole hard drive was sent
to me that would fit one of the laptops that we had remaining in the base block
for me to use. While that was going on, we were preparing for this internal EVA
back at the Spektr, so I was thinking, "Oh, maybe we'll get it back from
I received the Wolfram replacement copy on a Progress within about three
weeks of the collision.
And it was then that I was having trouble again with the password, because it
was not on a CD; they sent it to me on a hard drive. And I had to put it into a
different laptop from the one it had been installed on. What happens?
"What's your password?" Now -- and this gets very painful -- this is
nothing to a modern communications age. But my communication with the Earth was
no more than about two minutes a day with my team in Moscow, in English. All the
rest of the communication period, we only had about a total of an hour a day,
because of the state of the Mir, to work on all of the problems we had to solve.
And so I got very low priority.
In the end I think I used the RadioHam network, and I used the RadioHam radio
to call down to Houston, because we were flying overhead over a six-minute path.
A good friend of mine was there. I said, "Can you get into my house? Do you
know how to get -- " And he said, "Yes, I can get there," because
my wife was on vacation at the time in Kentucky. I said, "Go to my house,
get the key, go to my computer..." And I told him where my password was.
They couldn't find it.
Anyway, I know a lot about the Mathematica system of password
protection now, and I got around that in the end. In the end I got the version I
had working, which was the one sent up on the Progress vehicle. But then Pavel
and Anatoly were getting ready to go into Spektr. And, lo and behold, during the
EVA, Pavel -- I was in the Soyuz module, cramped up -- Pavel said, "Mike! I
found it! I found it!" "Great!" And he brought back -- I thought
he found the CD pack. But he hadn't; he found the laptop. And he just brought
the whole thing -- he'd ripped it out, and he ripped the wires out of the wall,
and just brought the laptop back. And in the laptop was the original hard drive
I had. Lo and behold, I turned on the laptop, with a new mouse and all the rest,
because they'd been torn off -- and the laptop didn't power up at all. I should
tell you it was an IBM ThinkPad.
They don't have a warranty out for vacuum use. That laptop also had all my
mail, all my correspondence with my family on it. So then I took the hard drive
out, moved it to another ThinkPad, and it powered up.
And the most interesting of all here -- this is an aside -- they also brought
out my notebook -- I mean, a real notebook -- with a Ziploc bag that I kept my
floppy in. And that Ziploc bag had totally evaporated. There was just kind of a
sticky residue on the back of the notebook. The rest of the pages were all
perfectly preserved; my photographs were preserved, the ones that I had up of my
family on the wall in Spektr; and Pavel had brought those back. But it was just
the Ziploc bag material that had evaporated in the cold conditions and in the
Presumably there's something like that in the IBM ThinkPad that just
deteriorated in its time in the vacuum. So I then finally got our hard drive
back and was up and running. And then, as I got to set up the problem, the next
power failure happened.
That wasn't particularly amusing.
There's a whole different approach to controlling the orientation of
spacecraft today, using today's technology, than was used when they built the
Mir systems. The Mir systems relied basically on what's called a strap-down
attitude control system; that is, they have rate sensors, rate gyroscopes, and
they then integrate from that rate to find out what the orientation is. Errors
build up, of course, very quickly in a rate integration system, and so they use
sensors -- infrared sensors -- for these.
As the Mir goes around the Earth in an inertial attitude, the earth
intersects, as an infrared body, these sensors. And so, from those once-an-orbit
intersections, the Mir can always eliminate the error that builds up in the rate
integration. That's how the Mir system works. So you basically have to be in
good shape, in a stable position, and have engine control, and then start doing
an active rotation of the station to know what your orientation is.
In the Russian control sensors, they say, "We're going to construct our
orientation control matrix," and they really do it with maneuvers of the
spacecraft, of either the Soyuz or the Mir. Nowadays, we use ring laser gyros;
the shuttle uses, actually, a gyroscopic inertial navigation platform. Then
nowadays you use the GPS differential antenna. So there are a number of ways to
skin that cat, but the way it was done on the Mir was a fairly old-fashioned
Q. Why is the middle axis of rotation the most unstable one, and what made
the axis that just happened to be the unstable one on the Mir, unstable?
It's a property of the middle moment of inertia of the inertia tensor.
Q. Was there any vodka on board?
I can answer that quickly and say no. Vodka has been tried on there -- not
when I was there -- apparently a long time ago by cosmonauts, and they said it
reacts too quickly. There's something you should know about liquids; the surface
tension -- that juice I was drinking there was particularly tasty because, when
you drink it through a straw, it spreads out through capillary action all around
your throat and mouth and down the throat. So if you imagine a vodka or
something like that... But United States spacecraft do not have liquor on board.
What I did in that notebook was really pretty rough. I knew what the property
was, and I knew it was the middle moment of inertia property. I knew that the
moments of inertia were close, and that they were different.
Thanks very much for your very long attention.
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© The Mathematica Journal