The Greening of Orbital Debris (Nicholas Johnson)


Uploaded by NASAappel on 01.09.2011

Transcript:
It turns out that because of my activities I deal with engineers
 
probably more than any other type of discipline
 
not only within the Agency
 
but within the inter-agency the U.S. government
 
and internationally.
 
And someday if my granddaughter
 
decides to marry an engineer,
 
I"ll probably give her my blessing.
 
Um, this will automatically go.
 
Prior to Sputnik I
 
there was only one known object
 
in orbit about the earth
 
and that of course was the moon.
 
Since then,
 
we've gotten quite a bit of man-made debris.
 
It turns out that throughout the past 50 years
 
the percent of operational objects in earth orbit
 
is about five percent.
 
It's maintained that pretty regularly
 
up until the last few years.
 
One of the challenges I do not have
 
is when I show this series of slides at the end
 
everybody agrees
 
there is a space pollution problem.
 
It's not like climate change
 
where there's still debate, whether you...
 
you think there is a legitimate debate or not
 
there is an actual debate
 
and you have to convince people.
 
This pretty much convinces them
 
all by itself.
 
So these are all objects
 
which are larger than ten centimeters
 
which are being tracked on a regular basis
 
by the U.S. Space Surveillance Network.
 
I do have to make a caveat:
 
for obvious reasons
 
the dots are not to scale to the earth.
 
[audience laughter]
 
And when I first started putting these
 
charts together about 30 years ago,
 
I picked the size of the spot
 
to be a little bit bigger than the
 
classic little dot you get
 
on a bad Xerox in the old days.
 
But what this does, so,
 
it looks like it's more congested than it really is.
 
Space is a big place.
 
And even though there
 
are lots of particles out there
 
and millions spacial density,
 
the number of pieces per cubic kilometer,
 
it's still very very low.
 
I mean we don't lose
 
operational space craft very often
 
with the exception of this year
 
to space debris, which is a good thing.
 
But these kind of graphics
 
are useful in looking at
 
the areas of concentration, and the
 
the trends that we see.
 
This is one of my favorite cartoons on orbital debris.
 
You know you've made the big time if
 
Frank & Ernest talk about your discipline.
 
The other interesting aspect is
 
this cartoon actually is over 25 years old.
 
Space debris, orbital debris,
 
has been in the public consciousness
 
for a long time.
 
It's obviously not something they
 
worry about on a daily basis,
 
but when certain events happen
 
like the satellite collision in
 
February of this year,
 
then people pop up and say
 
"Oh yeah, I knew something about that."
 
So what is orbital debris?
 
It's a pretty simple definition
 
it's anything which is not useful
 
and in earth orbit.
 
So that means derelict space craft,
 
it means orbital stages for launch vehicles,
 
and it means lots of fragmentation debris
 
and things which we intentionally
 
threw off a space craft
 
be it during human space flight
 
or be it during
 
robotic operations.
 
Some of this debris, some of the stages
 
are up to eight metric tons--a piece.
 
Some of these debris of course
 
are, you know, less than a gram.
 
So, we have to worry about that.
 
This is a
 
history of the official catalog that the
 
U.S. maintains of objects in Space
 
So this is sort of a graphical synopsis of those
 
pictures you saw at the very beginning
 
and we've broken them out into
 
rocket bodies, pay-loads, mission-related debris
 
things we threw off intentionally
 
and fragmentation debris.
 
And fragmentation debris has always been
 
the largest share of the overall population
 
and...
 
we've had two major events since 2007:
 
The Chinese conducted an anti-satellite test
 
which instantaneously
 
contributed over 3,000 large objects
 
3,000 objects larger than ten centimeters
 
so a dramatic jump in the population
 
which we had been building over 50 years
 
and all of a sudden we have this great step function.
 
And then,
 
the accidental collision between an
 
Iridium spacecraft and a Cosmos spacecraft
 
in February of this year,
 
which instantaneously created about
 
2,000 large objects.
 
So just very briefly, um...
 
the conditions, the background for that collision:
 
It occurred in February of this year
 
and out to about 790 kilometers.
 
That was not an accident.
 
790 kilometers, 800 kilometers
 
is like the second highest concentration
 
of tracked objects, or...
 
objects in general in orbit about the earth.
 
So if you're looking for an accidental collision
 
you know statistically they're going to happen
 
where you have the most objects.
 
And it finally did happen.
 
We've actually had accidental collisions
 
prior to this, but never between
 
two large intact objects.
 
The accidental collisions we've had prior
 
were between a small object
 
and a large object,
 
and spacecraft or a rocket body
 
and very little debris was produced.
 
In this case, both of the spacecraft
 
were substantially destroyed
 
in terms of numbers of pieces.
 
And we're still counting.
 
I mean this chart says 1,700
 
it's getting close to 2,000
 
and those are just the big things.
 
The smallest debris, of course,
 
goes up exponentially.
 
We've already,
 
NASA has already had to do one
 
collision avoidance maneuver
 
with one of our robotic spacecraft
 
because of debris from this collision.
 
Actually just a couple of weeks ago,
 
we were preparing to maneuver the
 
International Space Station
 
away from debris from this collision
 
but the last few hours
 
before we executed that maneuver
 
we decided well it wasn't going to come quite so close
 
and did not meet our risk threshold
 
for actually conducting the maneuver
 
so we stood down.
 
Debris is dynamic
 
just like the environment itself
 
in that it doesn't stay in one place.
 
Initially what you have
 
when you have a collision anyway
 
you have two distinct clouds
 
it just turns out that
 
these two vehicles when they hit
 
were almost in perpendicular orbits
 
had a collision velocity of nearly
 
11 kilometers per second
 
which is why you have so much energy
 
and why you have so many pieces.
 
But the perturbations in orbit
 
spread that debris out
 
because of the not...
 
uniform nature of the gravitational field,
 
because they're in different orbits
 
different orbital periods, different energies,
 
and so they start to spread out and
 
this is just the depiction of what it's
 
going to look like in February of next year.
 
The Cosmos debris spreads out a little bit quicker
 
because it's in a
 
a lower inclination orbit
 
so the perturbations are greater
 
and the green debris is the Iridium satellite
 
and it takes just a little bit longer to spread out.
 
But what you see, basically, is a ball of twine
 
and so the debris is everywhere.
 
So it only remains concentrated
 
for a very short period of time.
 
Now how do we know what's up there?
 
Well as I said,
 
the U.S. Space Surveillance Network
 
tracks the large things.
 
We have a cooperative agreement with D.O.D.
 
they characterize the large debris...
 
Using Goldstone, we can see down
 
to about 2 to 3 millimeters.
 
Now we can't track them,
 
but we can detect them.
 
We can figure out how big they are,
 
we can figure out what inclination they're in,
 
we know what their altitude is
 
and that then allows us to prepare a
 
statistical assessment of what the population is
 
and by doing this every year
 
we get an idea of the trend,
 
how the population is evolving.
 
And then for things smaller than about a millimeter,
 
then we have to rely
 
on the examination of returned surfaces.
 
Whenever the shuttle comes back
 
we do an extensive survey
 
to see what kind of damage it has incurred
 
even though the shuttle
 
and the International Space Station fly at the
 
the very lowest parts of low-earth orbit
 
where the spacial density, where the debris is less.
 
I mean that's the pristine part of Space
 
where the Shuttle and the Station fly
 
It's much much worse at higher altitudes.
 
Here are some, uh, let me go back...
 
I also have superimposed here
 
you know, damage levels.
 
These things, collision velocities again
 
are on average about ten kilometers per second.
 
It can be a little bit more or a little bit less
 
so a lot of energy involved.
 
Small particles can inflict great damage.
 
We first figured out that we had a problem
 
on one of the early Shuttle missions
 
we came back and had a pit in the window.
 
And we analyzed that pit and found out
 
it got hit by a fleck of paint.
 
And you think about it, every space craft
 
and every launch vehicle upper stage
 
is typically painted for thermal reasons.
 
And you know what happens
 
to your house's paint after about ten years.
 
So there's a sea of paint particles up there.
 
Now fortunately, these are typically
 
you know, much less than a millimeter in size
 
and they don't pose a real serious threat
 
to virtually all vehicles.
 
The Shuttle, however, is very special.
 
We reuse the vehicle of course, and so
 
if there's an imperfection in the outer pane
 
of one of the [inaudible] windows
 
then we have to replace it before we fly again
 
because the launch stress is what might
 
propagate that imperfection.
 
But in general,
 
every spacecraft is vulnerable
 
particularly robotic spacecraft which is the
 
primary concern I think of most people in this room
 
are vulnerable to five millimeter particles.
 
We can only protect up to about
 
one centimeter size particles.
 
These are some cases of
 
impacts on the International Space Station.
 
Actually the upper-left is the
 
largest impact we've had on the Station.
 
Fortunately it hit on the area of a
 
Russian module that had substantial thermal blankets.
 
It penetrated the thermal blankets.
 
If it hit another part
 
it could have gone through a pressure wall.
 
But we have quite a bit of, um...
 
actual debris shields on the station
 
I'll show you about that in just a second.
 
This is one of the multi-purpose logistic modules
 
which fly to the Station only for about,
 
you know, ten days or up to two weeks,
 
during a Shuttle mission
 
and is brought back right away.
 
And during one of the flights,
 
one of the early flights actually,
 
we had a penetration.
 
But it's a double wall
 
so there was no problem in terms of the
 
safety of that particular module to the crew.
 
As I said we investigate the shuttle
 
after every flight.
 
This is one of those impacts on the window blown up.
 
This is a hole in the radiator.
 
You know the big, large, aluminum structures
 
inside the cargo bay doors.
 
Great witness plate for me
 
but it's a risk to the shuttle because
 
as you might imagine it's a radiator,
 
there are tubes underneath
 
those sheets of aluminum
 
and if you penetrate a tube
 
you have a substantial effect
 
on the thermal control capability of the vehicle.
 
Alright, NASA has pioneered
 
this whole area of orbital debris
 
and we started putting out specific
 
what originally were guidelines in 1995
 
they're now called requirements.
 
Actually today is the 30th anniversary of the
 
establishment of the NASA Orbital Debris Program Office.
 
Beginning of the fiscal year of 1980.
 
And...
 
we have a system set up
 
as a relatively formal system
 
that every single project and program
 
with NASA that's going to fly in Space
 
has to prepare what's called
 
an Orbital Debris Assessment Report.
 
And it's first submitted at P.D.R.
 
and then again at C.D.R.
 
it actually now is a living document
 
you have to maintain it.
 
And then I had the privilege
 
of reviewing every single one of them
 
to gauge whether or not it's compliant
 
with the requirements that we have.
 
There are also special risk assessments
 
performed for the Shuttle before every mission.
 
There are certain requirements
 
maximum risk which we allow
 
in terms of loss of crew and vehicle
 
in terms of maybe having to
 
terminate the mission early because
 
the radiator got penetrated
 
and whenever there's a fragmentation event
 
because as you saw from the earlier illustration
 
debris goes all altitudes.
 
And so there could be
 
an explosion at 600 kilometers
 
that can affect the International Space Station
 
down at 350 kilometers.
 
And I've gotten many calls
 
at two and thee o'clock in the morning
 
saying, from D.O.D., saying
 
"We've just noticed an explosion."
 
and then we have to go back and
 
quickly, real-time do an assessment,
 
to make sure that that particular event
 
does not pose an undue risk to
 
human Space life or even some of our
 
more valuable robotic spacecraft.
 
And then finally, the ISS I said it
 
we have substantial dedicated shields on Station.
 
If you remember there was a chart
 
yesterday that said
 
at mission complete
 
the mass of the International Space Station
 
will be 400 metric tons
 
and a little bit more than that.
 
Five percent of that is dedicated shielding.
 
And you think about
 
how much it costs to put a kilogram in Space
 
look at the cost then that we've had to incur
 
just for orbital debris
 
to be able to maintain the International Space Station.
 
Alright, we've got very good top-level support.
 
There have been two inter-agency
 
U.S. Government inter-agency documents
 
on orbital debris:
 
a 1989 and then a 1995.
 
The President's national Space policy
 
has mentioned orbital debris mitigation
 
since President Reagan in 1988.
 
The current national Space policy
 
came out in August of 2006
 
and if you get these charts later on you can read this
 
or you can download it from our website.
 
This is verbatim what it says.
 
Basically it says that
 
you know, orbital debris poses a risk
 
to operations in Space
 
and it poses a risk to people in Space
 
and on the ground.
 
And I'll talk about the ground part
 
here in just a minute.
 
And then we developed,
 
as a result of the 1995
 
direction from the White House,
 
D.O.D and NASA were tasked to go out
 
and develop what we would call the
 
United States Government Orbital Debris Standard Practices.
 
These are the things you should be doing
 
and the design and operation
 
and disposal of your vehicles,
 
including spacecraft and launch vehicles.
 
And then the last part
 
which is also important, it says
 
"The United States shall take a
 
leadership role in international fora,"
 
and we have been doing that.
 
We created under the auspices of the
 
Office of Science and Technology Policy and the White House
 
a multi-year strategy for handling orbital debris.
 
We did this in the late nineties
 
and we just signed off,
 
completed every part of it, in 2007.
 
And it said
 
"First, get our own act together."
 
There were differences between NASA and D.O.D.
 
and the other agencies weren't even really
 
thinking about orbital debris.
 
So first we came up with these standard practices.
 
We then took those standard practices to the
 
what's called the
 
Inter-Agency Space Debris Coordination Committee
 
which is an organization of the eleven major
 
space-faring agencies of the world.
 
You have to be an agency to be a member.
 
NASA is the U.S. representative.
 
I'm the head of the NASA delegation to I.A.D.C.
 
but my delegation includes D.O.D.,
 
it includes State, it includes the [inaudible],
 
because they're all players in Space operations.
 
We went to the I.A.D.C., convinced them
 
and developed the first international guidelines
 
on orbital debris mitigation.
 
And then,
 
the last step was to go to the United Nations
 
and we did that and were very successful.
 
So what are the debris mitigation guidelines?
 
They're very general and straight forward.
 
You don't want to create debris unnecessarily.
 
In the past we actually had been doing that.
 
Like, in many cases you create
 
pollution sometimes without thinking
 
about the consequences.
 
Minimize debris generated by accidents.
 
The vast majority of debris,
 
which is a hazard to Space operations,
 
comes from accidents.
 
Then we will worry about safe flight profiles
 
and how you design your vehicle,
 
what altitudes you fly at,
 
and then what do you do with it at the end?
 
It turns out that is probably the most
 
crucial element of this whole problem.
 
And then in 2002 we were able to get the I.A.D.C.
 
to put together these guidelines.
 
I said there are 11 members of the I.A.D.C.
 
it's a consensus organization.
 
which means every single member
 
has to agree to these guidelines
 
before they can be developed, and that's quite a bit.
 
But if you really want a challenge,
 
work in the United Nations.
 
I've been the U.S. technical expert
 
at the U.N. for 13 years
 
and you're sitting in a room with 70 plus members
 
and it's a consensus organization
 
and every single country
 
sitting in the room has to agree with it
 
and the, all the major official languages of the U.N.
 
and every single word
 
is up for debate and negotiation.
 
But, all that being said
 
in 2007 the United Nations did approve
 
the Space Debris Mitigation Guidelines.
 
And they're now out to everybody in the world.
 
You can see them from the NASA website.
 
And they're almost verbatim
 
from what we had before but,
 
you know, some of the words are a little bit different.
 
Alright so, Green Engineering and Orbital Debris.
 
Green Engineering is really not a term
 
we use in my discipline.
 
In fact, my first...
 
connection with Green Engineering was 40 years ago
 
when I was an avionics technician in the Air Force
 
and we had a motto there that, you know,
 
if it moved, you safety-wired it
 
so it wouldn't come out during flight
 
and if it didn't move
 
you painted it green so it wouldn't rust.
 
And so when I was on the flight line
 
I had a can of spray green paint to paint things
 
but this is sort of a different connotation now.
 
Initially, of course, in the sixties, you know,
 
we were just happy to get into orbit, you know.
 
That was the challenge.
 
So we would throw things off intentionally.
 
Springs, we have explosive bolts
 
we didn't care where the pieces
 
of explosive bolts went,
 
we had covers for sensors,
 
particularly cameras and [inaudible] control sensors
 
we'd just throw them away
 
and we didn't think too much of it
 
and gradually as you saw from the early graph
 
that slowly accumulates in terms of
 
number of objects still in orbit.
 
So now most missions are
 
debris free by design.
 
It's taken a long time to convince
 
the aerospace engineers
 
developing launch vehicle spacecraft
 
that this really is
 
in their own best interest
 
so that we can maintain space operations.
 
The term that is come into vogue
 
even in my area is
 
"sustainability of space operations."
 
It was actually a term
 
coined by the Chairman of the
 
Technical and Scientific Subcommittee
 
of [inaudible] in the U.N.
 
Gerard Boucher from France
 
when he was the chairman.
 
And it's the theme of the
 
International Astronautical Congress which
 
convenes about ten days from now in South Korea
 
This is very important to the
 
international aerospace community.
 
If we see...
 
events which produce debris
 
then we now tackle them immediately.
 
The Delta IV launch vehicle
 
is relatively new.
 
The Japanese developed
 
the H-2A several years ago.
 
When they first started to fly,
 
they were producing debris
 
which was not expected.
 
And so in both cases the U.S. and Japan
 
immediately tackled that and said
 
"What's going on? We need to stop this."
 
And the Japanese have been successful
 
and the U.S. is still working on Delta IV
 
but I think it's getting better.
 
Alright
 
Spacecraft and orbital stages
 
have to be passivated at
 
the end of the mission.
 
Passivation simply means
 
get rid of all the stored energy.
 
You know, we don't always know why
 
a spacecraft or a launch vehicle blows up
 
but there have been over
 
200 fragmentations reported since 1961,
 
the vast majority
 
were accidental explosions
 
over 140 from vehicles
 
which had successfully completed their missions.
 
They were spacecraft or they were launch vehicles
 
that did exactly what you asked them to do
 
and then you left them on their own
 
when you turned them off
 
and then spontaneously, a day later,
 
sometimes 25 years later, they blew up
 
into hundreds of large pieces
 
and many many more smaller pieces.
 
The reasons of course are varied
 
depending upon the design.
 
It's not always propellants
 
it could be pressurants, it could be batteries,
 
but, we finally decided, you know,
 
let's just get rid of all the energy
 
and this can't happen.
 
And we basically have been
 
100 percent successful.
 
Once you passivate a vehicle it just doesn't
 
have the possibility of blowing up.
 
And this has been one of the
 
great success stories, actually.
 
And when we go to designers
 
of launch vehicles and spacecraft
 
they say, "Well oh yeah that makes sense."
 
And in almost all cases it's very very easy
 
to fix the problem.
 
You vent the pressurant,
 
you turn the engine back on
 
and burn off all the propellants
 
or you vent the propellants,
 
it's really not that big of a deal.
 
And so we get actually very good compliance
 
on the launch vehicle side.
 
A little bit more of a challenge
 
on the spacecraft side.
 
Classic, you know, cultural phenomenon:
 
"We've been building spacecraft
 
"like this for decades,
 
you know, why should I change?"
 
Well, you know,
 
we have seat belts in cars now,
 
we have catalytic converters
 
which we never used to have
 
but there's a reason for them,
 
and eventually, we're getting there, you know?
 
One of the things when we first
 
started out we said look:
 
"You don't have to go back and
 
"retrofit series spacecraft.
 
"But if you have a de novo design
 
"here's your chance, you know
 
"start with a clean sheet of paper,
 
let's do it right,"
 
and we're making good progress.
 
Reduce the potential
 
for future accidental collisions
 
because they create debris.
 
So one of the ways to do it is
 
to get rid of these guys.
 
And so NASA came up with a metric
 
a criteria that says
 
when you're done with your launch vehicle
 
or your spacecraft in low-earth orbit
 
make sure that somehow
 
it's gone within 25 years.
 
Typically what you do, you know if you're
 
below 600 kilometers it'll happen naturally.
 
Mother nature will take care of you.
 
If you're above 600 kilometers
 
you need to probably bring your vehicle
 
back down to a lower altitude.
 
And then withing 25 years
 
mother nature, again, will take care of it.
 
This was a good thing...
 
and it does prevent the growth
 
of a lot of mass in orbit.
 
Because mass is the metric
 
that we're concerned about
 
because where there's mass,
 
because of collisions
 
there will be more debris.
 
The less mass,
 
the less future debris.
 
In geosynchronous orbit
 
obviously you can't come down
 
out of the environment
 
so you just want to get away from that
 
very valuable and unique resource
 
the [inaudible] orbit.
 
So we say, "Just go up like
 
200 kilometers and stay away."
 
You do have to worry about perturbations.
 
Make sure you don't automatically
 
wind up coming back after some period of time.
 
And it only takes like 10 kilograms
 
of propellant to do that at that altitude.
 
So this is not a real serious problem and
 
Spacecraft operators [inaudible] have been doing this
 
now since the seventies.
 
We have relatively good compliance internationally.
 
Not complete but, you know, we're
 
working on doing a better job.
 
[Inaudible] though we're encouraging operators
 
to get rid of their vehicles in 25 years.
 
Well, where are they going?
 
They're coming back to earth.
 
So what we're doing is
 
we're taking an on orbit risk
 
and we're transferring it
 
into an on the ground risk
 
because particularly, if you have a vehicle
 
that weighs more than a few hundred kilograms
 
almost always they'll be components
 
of those vehicles which survive reentry.
 
You know, this notion that everything
 
burns up on reentry, just is not true.
 
Practically any spacecraft or launch vehicle
 
will have components.
 
Some many components,
 
some very large components.
 
You saw a picture yesterday of a big tank
 
that came down in Georgetown, TX
 
just north of Austin
 
with a woman bending over it.
 
Well I took that picture [audience laughter].
 
That was a T.V. reporter.
 
What you didn't see,
 
because of the angle that I selected,
 
all you saw was a farmhouse in the far distance.
 
Well if I turned about 90 degrees
 
and took the picture,
 
you'd see a farmhouse was
 
about 100 meters away.
 
And this farmer's wife
 
went to bed that night
 
there was nothing in their front yard
 
and during the middle of the night
 
this thing comes crashing down.
 
So there is a risk
 
and we recognize that risk
 
and the bottom line here in the end is that
 
we have adopted in the U.S.
 
and is gradually taking international acceptance
 
a criterion that says:
 
"The reentry risk from any object
 
should be no greater than 1 in 10,000."
 
If it is, then you probably need
 
to do a controlled de-orbit.
 
Mentioned yesterday, logistical vehicles,
 
International Space Station are typically
 
dropped into the Pacific.
 
In fact, there was a
 
progress spacecraft just earlier this week
 
that was dropped into the Pacific Ocean.
 
When the time comes
 
the entire International Space Station
 
will be dropped into the Pacific Ocean.
 
Hopefully, you know, after 2020 and
 
however long we can maintain it.
 
But we, before we started bending metal
 
on the International Space Station
 
we were thinking about:
 
"Oh my God, how do we get rid of it?"
 
It's 400 metric tons.
 
You can't let that thing come back by itself.
 
You know you have to put it in the ocean
 
Just like the Russians did with Mir
 
and the previous space station.
 
How do you move 400 metric tons
 
and put it right where you want it?
 
Well this is a work in progress [audience laughter]
 
we don't really have all the answers
 
but we kind of know
 
how we might get away with it.
 
As you remember in May,
 
the Shuttle went up to
 
supposedly the last servicing mission
 
for the Hubble Space Telescope
 
and people would say
 
"Well that's the last time we're ever
 
going to visit the Hubble Space Telescope."
 
Not true.
 
NASA is committed to
 
doing a controlled de-orbit of Hubble
 
because it weighs so much, it has so much mass,
 
that its risk to people on the ground
 
is too great that we can't let it
 
come in uncontrolled anywhere in the world.
 
So, at some point,
 
probably in the end of the next decade,
 
we will go back and visit HST
 
either robotically, or with CEV or with something,
 
attach a de-orbit motor,
 
and drop it into the Pacific.
 
We, because of this...
 
we at NASA,and particularly at Goddard,
 
give them credit,
 
have a program called
 
"Design to Demise."
 
And it kind of...what it says.
 
What you like to do is
 
build your spacecraft out of materials
 
which don't survive re-entry.
 
Which means you don't want to use
 
high melting temperature materials
 
like titanium, beryllium, stainless steel,
 
materials that actually
 
we've been using in spacecraft
 
and launch vehicles for many many years.
 
And we chose them for convenience
 
and sometimes we chose them because
 
they had specific material properties
 
which we felt were essential,
 
particularly in the payloads.
 
Payloads sometimes are the hardest ones to retrofit
 
because...the unique properties,
 
you need coefficient of expansion and everything,
 
that you have to worry about.
 
But what we're trying to do is replace
 
those high melting temperature materials
 
with lower melting temperature materials
 
like aluminum.
 
I'm sure you remember
 
in January and February of last year,
 
the United States Department of Defense
 
had a spacecraft called U.S.A 193
 
which had malfunctioned
 
contained hundred of kilograms of hydrazine
 
and was about to reenter
 
in an uncontrolled manner
 
because they had lost control right after launch.
 
The problem we had was that
 
all that hydrazine was in a
 
very large titanium tank,
 
and titanium tanks typically
 
reenter very very well and in one piece [audience laughter]
 
We actually in my office,
 
we do reentry analysis for every NASA vehicle
 
but we always look at them
 
as if they were empty because
 
the earlier guideline says
 
you've got to passivate the vehicle so
 
you've already gotten rid of all the propellants.
 
We had actually never worried about
 
a failure scenario
 
in which we had a full hydrazine tank
 
and D.O.D. hadn't either.
 
And so I was the NASA representative
 
on an inter-agency group
 
that the President charged with
 
trying to neutralize this threat.
 
and as you well know
 
we were able to negate that threat
 
by blowing the thing up just before it reentered.
 
But that's not an action
 
that we normally want to take.
 
And as it turns out,
 
not very well known,
 
certainly not to the public,
 
a few months after that activity
 
to negate that particular threat
 
NASA launched the GLAST satelite
 
that contained several hundred
 
kilograms of hydrazine
 
in a titanium tank.
 
And if GLAST had or,
 
actually, if it were to fail today,
 
we would have a very similar problem.
 
We would have tank with frozen hydrazine
 
which would be eventually coming back to Earth
 
because it's at a relatively low altitude.
 
So we're now looking at ways to prevent that
 
and Goddard has already done this.
 
They've now designed a tank
 
for hydrazine which is not titanium.
 
And it will demise.
 
So the trick here is
 
to come up with better materials.
 
In this case better is lower melting temperature.
 
But it's a tremendous...um, again, culture change
 
for the aerospace industry
 
and you really have to work very hard
 
to convince them that this
 
is something that really is necessary.
 
It costs a little bit to design this
 
but now that you designed it,
 
you know, that cost is gone
 
and it's just as easy to build an aluminum tank
 
than it is a titanium tank.
 
Alright, what's the long term?
 
We have known for actually 30 years plus,
 
that the real long-term problems are
 
objects running into each other
 
just like we saw on February.
 
We knew that was going to happen.
 
Can't tell you when it was going to happen,
 
I'm not Gene Dickson, I can't foresee the future.
 
But, we knew that was--
 
I mean statistically it's inevitable.
 
And so a colleague and I had an article in Science
 
in January of 2006, that basically
 
we're just taking a new look at the problem.
 
We said: Beginning of 2006
 
nobody in the world ever launches
 
another object into Space.
 
All we have is what's up there.
 
What's going to happen to...debris population?
 
Well, you initially have decay of fragments,
 
decay of intact objects
 
but, you know, low-hanging fruit,
 
you know, it's exponential in terms of
 
longevity once you go to higher altitudes
 
so after you get rid of the
 
low altitude stuff below 600 kilometers
 
everything else is up there for many many decades
 
and hundreds of thousands of years
 
and so what happens is
 
you start having these random collisions
 
and within about 40 or 50 years
 
you actually start having
 
a net increase in population just because
 
you're creating debris quicker than it's
 
falling out of the environment.
 
Well, that was optimistic for many reasons
 
one is:
 
we assumed nobody was doing any launches,
 
nobody was doing anti-satellite tests,
 
there were no more accidents going on.
 
So here's a chart we put together
 
just actually a few weeks ago.
 
Brand new, off the press.
 
Hasn't been shown by--seen by anybody.
 
The biggest problem is
 
when we did the earlier study
 
we were down here
 
but already we have the problem that
 
we have a lot more debris up there
 
than we did three years ago
 
because of the Chinese test and the accident
 
in February of this year.
 
And then we go through a bunch of scenarios
 
that say "What if you did absolutely nothing at all?"
 
And of course that's the worse case
 
and that's the top line.
 
And then what if you kind of
 
ignore what you're doing today
 
but you make a commitment to start
 
pulling big things out of orbit?
 
How will that affect the environment?
 
And that's what these three curves are right here.
 
And then what we really want to do
 
is continue to be compliant
 
with the guidelines that are out there today,
 
both nationally and internationally.
 
And in addition to that,
 
that alone won't prevent
 
the growth of the Space debris environment.
 
So we have to start thinking about actively
 
removing large objects from earth orbit.
 
That is the long-term problem.
 
Now we do have an advantage that,
 
you know, the climate-
 
change community doesn't have.
 
You know there's a perception,
 
perhaps reality,
 
that climate change is something
 
which is coming very quickly in a relative sense.
 
This problem is much much longer.
 
I mean it's still exponential
 
like so many things are in nature
 
but it's got a long time constant.
 
This is a hundred year scenario.
 
And the worst case scenario if I did nothing;
 
worse case, you know, what
 
the environment doubles in a hundred years.
 
Well, this is not
 
what you typically read in the paper
 
or the science fiction magazines
 
where all of a sudden
 
you can no longer use earth orbit,
 
you can't fly a weather satellite
 
or a navigation satellite
 
or a human piloted satellite
 
because it's too dangerous.
 
That would happen...
 
but we're not talking eons down the road.
 
So we do have time to do this.
 
We don't have to worry about doing it
 
over the next five or ten or even fifteen years.
 
Now finally, I do have what I think
 
are some worthwhile lessons learned
 
and perhaps have application
 
in your individual areas
 
where you're more concerned about
 
terrestrial pollution.
 
Again, obviously in the long term we
 
we have to worry about
 
Green engineering in Space.
 
The United States and the international community
 
have already been very proactive.
 
This is one of those
 
relatively rare areas of pollution
 
where we recognized the issue
 
before it was a problem.
 
We knew this was going to eventually happen
 
and we're tackling it early. So...
 
actually the last 20 years
 
when we're going out and preaching the gospel
 
of Space debris mitigation,
 
we have not worried so much
 
about the longer term
 
we're trying to educate people
 
saying "There are some simple things
 
"you can do right now
 
"which will have a dramatic impact,
 
a positive impact on the future environment"
 
and that's what we've been pushing.
 
How we did that
 
and why we were successful
 
is NASA put in a lot of resources,
 
and Louis can attest to this,
 
to make sure we understood the problem.
 
And then we took that message out
 
to the technical community because
 
those are the people that have to respond to it.
 
And then we also had to develop
 
effective and acceptable policies and guidelines.
 
You know, if I say, you know,
 
you can't ever use titanium
 
again in a spacecraft, well,
 
you know, you just sort of turn me off.
 
You know, so we work with
 
the aerospace engineers
 
to find solutions.
 
You know, if I tell you you have to de-orbit
 
from geosynchronous orbit, you know,
 
that's a non-starter as well.
 
So you have to find things that work and
 
at least we've been fortunate in our community
 
there are some very helpful activities
 
and design processes that will do that.
 
The other thing we did
 
we also worked very closely with the
 
international community. This is not a...
 
U.S. only problem, you know?
 
We can't fix it
 
and we're not responsible for all of it.
 
Now, you know, we have our share of
 
responsibility in terms of debris up there
 
but the Russians and the Chinese
 
are about equal with us right now.
 
But it's an international issue
 
so what we want to do is make sure
 
that when we put in place these guidelines
 
they are accepted internationally
 
so that our industry is not
 
put at an economic disadvantage.
 
And so ESA certainly has been on board with this
 
from the very early days.
 
In fact, the very first organization
 
that NASA went to to discuss this
 
on a bilateral level was with ESA
 
and got a very very good reaction.
 
The long term remediation of the environment
 
is really what we need to do.
 
And that's a term that we
 
actually have not been using much
 
until the last several years.
 
Again, we don't think it's urgent
 
but clearly since the February event
 
a lot of people are talking about remediation.
 
The problem is...
 
we don't know how to do it.
 
It's either technically impossible,
 
depending upon your concept, your technique,
 
or we can't afford it.
 
And so you have to find something that will
 
meet both of those criteria
 
and I've been thinking about this
 
for a long, long, time
 
and still haven't found anything.
 
And since February
 
we've been getting a lot of unsolicited suggestions
 
of how to clean up the environment
 
and in December DARPA and NASA
 
are cosponsoring an international conference
 
in the Washington area
 
on orbital debris removal.
 
If we knew how to do it
 
we wouldn't have a conference
 
we wouldn't ask people to come in
 
and give us good ideas.
 
I've seen a lot of good ideas
 
from some smart people and
 
some lay public people.
 
But we're still struggling.
 
We can't find anything which is good
 
either for the small debris environment
 
or for the large debris environment.
 
but, you know, as time goes on
 
as technology improves,
 
if the economics of Space transportation
 
ever come down and improve,
 
you know some of these things may now
 
look a little bit more attractive
 
than they do before.
 
So if there are any other questions left,
 
we're back on schedule.
 
[audience applause]