Space Debris (featuring Dr. Jonathan McDowell)

Daniel and Kelly talk to Dr. Jonathan McDowell about the kinds of junk you find in space, the problems it causes, and what we can do about it. 

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Episode Transcript

Speaker 1 (00:05):
In nineteen sixty two, the United States detonated a one
point four megaton hydrogen bomb four hundred kilometers above the
surface of the Earth. This was part of a project
called Operation fish Bowl. Not Surprisingly, it created a huge
explosion which lit up the sky and disrupted radio transmissions.
It also knocked out street lights in Hawaii, which may

(00:27):
have worried partygoers who, according to Smithsonian magazine, were gathering
on hotel rooftops for h bomb explosion viewing parties. It
also messed up six different satellites, whour belonged to Americans,
one was Russian, and it also messed up the very
first British satellite. The Soviet Union was conducting similar tests

(00:47):
of nuclear weapons in space at the same time. This
didn't bode well for the future of satellites in space.
This amazing new technology of satellites held a lot of promise,
but who would want to invest in it? If the
United States and the Soviet Union kept making satellites inoperable
with nuclear weapons tests in space, well lucky for all
of us. In nineteen sixty three, both nations agreed to

(01:10):
stop screwing up space for the rest of us and
signed the Partial Nuclear Test Ban Treaty, which banned the
test of nuclear weapons in some places, including space. In
this year, you also get a UN resolution saying weapons
of mass destruction can't be orbited in space. And you
get a United Nations Outer Space Treaty which comes into
force in nineteen sixty seven, which reiterated all of these

(01:32):
points for other nations as well.

Speaker 2 (01:34):
New Now satellites are safe, right, well, probably well, space
is really vast. We've put a lot of stuff in
orbit around Earth, and the pace at which we're sending
stuff up is ever increasing as the cost of sending
that stuff up drops.

Speaker 1 (01:51):
Could it get too crowded up there? Could some of
the space litter we've left behind smash into the stuff
we're still trying to use. I'd be really bummed out
if I couldn't watch cat videos using my Starlink satellite
provided internet. To answer some of these questions about the
risks of stuff bumping into each other in space, we're
interviewing doctor Jonathan McDowell, who has been tracking objects sent

(02:13):
to space since nineteen sixty one, when the Soviet Union
sent up Sputnick, the first ever satellite in space. Welcome
to Daniel and Kelly's Extraordinary Universe.

Speaker 3 (02:37):
Hi, I'm Daniel. I'm a particle physicist, and I feel
like my house is constantly filling up with junk.

Speaker 1 (02:43):
I'm Kelly Winer Smith. I'm a parasitologist and I have
felt that way since I married Zach. And the rate
at which the junk has been increasing has exponentiated since
we had children. So we might have a Kessler syndrome
situation happening in our house in the near future.

Speaker 3 (03:00):
That's only if your children collide with each other and
make more children or something.

Speaker 1 (03:05):
The biologist in me is not okay with that metaphor.

Speaker 3 (03:09):
No, that was bad. So which of you is the
cleaner upper or are you both contributing to the junk?

Speaker 1 (03:14):
I am the cleaner upper. I am also the less
bringer stuffer into the houser. I don't like to buy
a lot of new stuff, but that's not my husband's
attitude about stuff. What about in your family.

Speaker 3 (03:27):
I'm the thrower away. I'm the person constantly carding out
bags of junk in the house, whereas my wife and
daughter like going thrift store shopping and so they're bringing
stuff in, and then I'm like taking trips to the
thrift store. When I take a trip to the thrift store,
for example, it's a negative impact on our house, and
they have the opposite effects. So we have like a

(03:49):
thrift circuit going.

Speaker 4 (03:50):
Man.

Speaker 1 (03:51):
So I've gotten myself in trouble for being the person
who throws stuff out in the house because my daughter
will not let go of things, and Zach doesn't want
to let go of things either, and I got in
trouble once. I was like, well, if I just throw
it out, they won't notice. But then they notice, And
so for a while I moved everything to a storage unit.
You might be noticing it's a whole thing, Yes, the
whole thing.

Speaker 3 (04:10):
I see. See, you've moved to the multi stage throwout techniques.
I'm gonna put it over here, and then when nobody notices,
I'll move it over there, and then eventually I get
to throw it away.

Speaker 1 (04:18):
And that's why I have a whole farm. I've got
lots of spots to squirrel their junk away. Oh and
I just remembered that Zach has been listening to the podcast,
which is so nice of him. Don't check the tenant house.

Speaker 3 (04:33):
Well. The danger of moving on to a farm in
a big house is the more space you have, the
more junk you get. I feel like we have a
constant density of junk, and if we lived in a
smaller space, we would have less stuff.

Speaker 1 (04:44):
The belief has been that because we have all of
this space, we can get more stuff. But I don't
want the junk outside. I don't want more stuff. I
don't want more stuff.

Speaker 3 (04:53):
Yeah. Space is more valuable than almost any stuff. Whenever
we throw something away, I'm like, Ah, look at all
that empty space. It's wonderful.

Speaker 2 (05:00):
Yes, right, isn't it nice?

Speaker 1 (05:01):
So when when you come home with like a bag
in your hand and to just be able to like
put it on the counter because there's clear space on
the counter and not like have to elbow cups out
of the way.

Speaker 3 (05:10):
Ah, agree with you? All right?

Speaker 1 (05:15):
All right, team clean over here.

Speaker 3 (05:17):
And if we were in charge of the atmosphere around Earth,
maybe you and I we keep it pretty clean.

Speaker 1 (05:21):
Yeah, But the people that we keep interacting with would
be like, well, there's a lot of space, so we're
just gonna move it somewhere else, you know, And then
the graveyard orbit would get all crowded. And I don't know,
I'm a pessimist, Daniel.

Speaker 3 (05:32):
Yeah, Zach and Katrina would fill the universe with junk.

Speaker 1 (05:38):
There's there's room. Don't worry. Buy more books, buy more books. Well,
we don't have to keep them. We're not going to
read them again. No, I can't let go of a book.
Books gotta stay forever.

Speaker 3 (05:47):
Zach, you can keep all your books in orbit near Pluto.
M I love you, And today on the podcast, we're
going to be talking about junk and space junk with
somebody who has spent their whole career thinking and tracking
bits of garbage in space.

Speaker 1 (06:02):
I have loved interacting with Jonathan McDowell on Twitter. When
we were writing A City on Mars. He was my
go to person where I was like the needles from
Project west Ford, are they still in space? Jonathan, the
glove that got lost during the EVA number five hundred
and forty three, is that still in space? He knows
the answer to all of these questions. He is the guy.
We're excited to have him on the show today, So

(06:23):
let's jump right in. On today's show, we have doctor
Jonathan McDowell. He's an astrophysicist at the Harvard Smithsonian Center
for Astrophysics in Cambridge, Massachusetts. He's also the editor of
Jonathan's Space Report, a free internet newsletter founded in nineteen

(06:44):
eighty nine which provides technical details of satellite launches. His
website provides the most comprehensive historical list of satellite launch information,
starting with Sputnik. And he's a fellow of the Royal
Astronomical Society, an American Astronomical Society fellow, and he has
an astro named after him forty five eighty nine McDowell.
So he's now officially the second person on the show

(07:05):
who has an asteroid named after him. Martin Elvis beat
you by a few months there.

Speaker 4 (07:09):
My old boss. Yes, he was your old boss. He's
the one who conned me into crossing the pond and
coming to work at Harvard instead of staying in England,
which I'm now sort of regretting. Yes, no, Martin, I
go back away.

Speaker 1 (07:25):
Ah, wonderful. Well, he's absolutely lovely. And he talked to
us about asteroids. We're talking to you about stuff that's
floating around in space. So we had a listener who
asked a question, and we're going to play the question
a little bit later. But that got us interested in
space debris. So I think for starters let's just talk
about what kind of stuff we have up there, debris
or otherwise that's orbiting the Earth right now.

Speaker 4 (07:45):
So there are about twenty five thousand objects that the
Space Force radars are tracking every day.

Speaker 1 (07:52):
It's a lot.

Speaker 3 (07:53):
Twenty five thousand. Wow, that's an incredible number.

Speaker 4 (07:57):
That's just the ones big enough to see. Right. They
go from the four hundred and fifty ton International Space
Station down to little shards of debris that are only
about five or ten centimeters across to aally bit about
where they come from. But below that, between like say
one centimeter and ten centimeters, we think there might be

(08:18):
as many as a million pieces of debris that we
don't even know about because they're too small for the
radars to see. So now space is big, but everything
in space, because of Kepler's laws, is traveling like seventeen
thousand miles an hour. And so you know, it's pretty
crazy up there. And we have now ten thousand working satellites.

(08:40):
Just five years ago it was only one thousand. Now
it's gone up to ten thousand. Is that all starlink,
well about half of them a starlin Ghia. And so
there's Internet relay, there's Internet of things relay, there's ship
and the airplane tracking. There's weather satellites, there's SPIC satellites,
resource monitoring satellites, those intelligence which is like intercepting communications

(09:03):
and radio signals for the military, and of course a
few science satellites. People often think that space is like, oh,
that's science, but science is a pretty small fraction of
what's going on and what can happen is every time
you launch a satellite, you use a rocket to do it,
and to put it in orbit. The upper rocket stage
has to get into orbit along with the satellite. So

(09:25):
now you've launched your satellite, but you've also made a
piece of space junk the rocket stage. And nowadays, if
you're like prudent, you have a restartable engine. You can
bring the rocket stage down in the ocean afterwards. But
we didn't used to even bother to do that. So
if you look in the catalog of there's now over
sixty thousand objects in the Space Object catalog, including all

(09:46):
the re entered ones. The second entry in the catalog
is Sputnik, Russia's first satellite, but the first entry satellite
number one is actually the rocket stage that puts Putnik
in orbit and so the very first entry in the
catalog is a piece of space jump.

Speaker 1 (10:04):
Oh that's interesting and depressing.

Speaker 4 (10:07):
Yeah, what's worse if you leave a little extra fuel
in the tank of your rocket stage, which you can
tend to do because you don't want to arrive at
your destination running on empty rocket stages? Have you know
fuel and oxidizer that combine to burn to make the flame,
but they're in separate tanks, separated by often like a
rubber gasket or something like that, which over years can erode.

(10:30):
The two can get together and depending on your mix
of propellant, ten years after you abandon your rocket stage
in Earth orbit, the fuel and oxidizer can have a
party and suddenly you don't have a rocket stage. You
have three hundred pieces of space to breathe.

Speaker 1 (10:43):
Oh my god. So you're saying they explode?

Speaker 4 (10:45):
That will be the technical term, yes, whereas the space
guys like to say an RUD a rapid unplanned disassembly.
We have all kinds of euphemisms right for the bad
things that can go wrong in sp It's another one
of my favorites. Say is you know ICIBM into continent
balistic missile, But do you know IOBM, which is in

(11:07):
ocean by mistake.

Speaker 3 (11:08):
Oh no, So what's the sort of natural context, Like
we are creating these little bits of space junk, But
was the near Earth atmosphere sort of empty before that?
Or are there are like a lot of natural things
floating out there.

Speaker 4 (11:23):
So within the orbit of the Moon, we do have
like meteors coming in on escape trajectories. Right, they're not
orbiting the Earth. They have escape colostoy respect to the Earth.
They're going much much faster than satellites, and so they
come in, they burn up, they're gone. They don't hang
out in Earth orbit. The only piece of natural space
junk we have orbiting the Earth is the Moon.

Speaker 3 (11:47):
You can't call the moon junk.

Speaker 4 (11:49):
Come on, you know, it's a big love huston. You know.
We added to that with Spootnak and we've added ever since.
Again not just rocket stages blowing up, but also satellite's
hitting each other. So in two thousand and nine and
an Iridium communication satellite hit an old Soviet dead communication

(12:10):
satellite at about twenty thousand miles an hour in orbit.
And to give you an idea of the kinetic energy
involved in that, right, I mean it's like some number
of gigajuls. And now you don't have a feel for that.
So I calculated in terms of my unit of how
hard something hurts is. Imagine being hit by a one
ton truck. You can kind of sense how much that

(12:33):
would hurt. The energy involved in one of these orbital
collisions is about fifty thousand times that.

Speaker 1 (12:41):
Wow, wow, oh my gosh.

Speaker 4 (12:43):
And so what happens is a hypersonic shockwave goes through
both spacecraft, reducing them to shrapnel. The clouds of shrapnel
passed through each other largely unchanged, and you end up
with them in the original orbit, but many many little
pieces instead of one big one. So we don't like that.
That's bad. It can cause it. Ultimately, if you have
enough of those, you can get a chain reaction called

(13:04):
the Kestler syndrome that could make space unusable. And then,
you know, some people think it's fun to fire a
missile at one of their own satellites and blow it
up just to show how powerful they are anti satellite weapons,
and that causes yet there's more debris due to that.
There's been a move in recent years to go, you know, guys,

(13:25):
that's probably not a good idea.

Speaker 1 (13:27):
Yeah, let's stick into that a little bit more so.
I know that the Soviet Union, the United States, India, China, right,
they've all blown their own satellites up in space, is
that right?

Speaker 4 (13:37):
That is correct? Fortunately, so far they've only been tests
on their own satellites and not attacking somebody else's.

Speaker 1 (13:43):
So for our audience who's maybe not familiar with this,
why are countries blowing up their own satellites.

Speaker 4 (13:48):
Right, it's to prove that they could blow up your
satellites if they want it. And so the idea, you know,
what people may not appreciate is so much of our
lives today actually invisibly depends in space technology. I mean
the most obvious case, of course is GPS. I actually
know how to read a map, but the younger generation
are going to be really hosed if GPS ever goes down.

(14:10):
They're not going to be able to get home. And
that was originally a military system to target CRUISMUSS and
so that's in a war, taking out the GPS satellites
would be something that an attacker might want to do. Similarly,
military allund space communications. There are missile warning satellites that
spot when a missile is launched, and that's you know,

(14:31):
how you get that warning. And there are these sort
of very spic satellites, right, and so the military, even
more than normal people, are so very invested in space.
Their systems are integrated with space systems, and so in
a war, those space systems are obvious targets. And so
the idea of anti satellite weapons has been around for

(14:52):
a long time. The first attempt that I'm aware of
was in nineteen fifty nine when they fired a test
missile against the Explorer six satellite and missed it. But
it's not a new idea, that's what I'm saying. So
all of these things, you know, very early. The fifties
were a crazy time, man, They tried all kinds of
stuff very early.

Speaker 3 (15:12):
And so every time we blow up a satellite, you
go from one object in space to like a million
objects in space. Do we then track all of those
individual components?

Speaker 4 (15:22):
Yeah, well, the ones above ten centimeters we track. And
so sometimes people talk about shooting down a satellite, but
I hate that phrase because you don't actually shoot it down.
You add energy, you especially in the pieces, but those
pieces still have orbital velocity and they stay in limit.
And so if you have a satellite that's say in
a five hundred kilometer circular orbit. The pieces are in

(15:42):
elliptical orbits that are one end is five hundred and
then the other end might be lower, or it might
be higher, as much as one thousand kilometers or two
thousand kilometers coming down to the ones that go down
where you know we'll re enter quickly. The ones that
go up will stay up for a long time. And
so the worst one was a China Ease anti satellite
test in two thousand and seven, and that created three

(16:04):
thousand pieces of tracked debris. And so in my catalog
that I have on my website is each one of
those three thousand pieces has a catalog number from the
Space Force, It has orbital parameters that are updated every day.
It's quite a tusk keeping track of these things.

Speaker 3 (16:20):
So there's some random chunk of a satellite that has
like a name and a place in your database, and
you're tracking and it's just like a hunk of metal
floating through.

Speaker 4 (16:27):
Space that's exactly right. And you know, every now and again,
for example, the International Space Station has to dodge one
of these things. So the Space Force tressing goes, oh hey, guys,
about twenty four hours from now, this chunk of metal
is going to go within a few hundred meters of
the space station.

Speaker 3 (16:45):
Wait before we get to the ISS, how do we
track all these things? Like who is tracking this random
chunk of Chinese satellite? How do we monitor these things?

Speaker 4 (16:52):
So mostly it's the US Space Force route. For low
orbit satellites, they use radars, so you bounce radar radio
energy off the satellite and the echo gives you its
position and velocity. But it's a problem because if you
have like say one hundred new pieces that you're tracking,
so you see them come over, Okay, you get measurements
of one hundred pieces. An hour and a half later,

(17:15):
they've orbited the Earth. You look again, you've got another
one hundred pieces. But matching up which one goes with
which one is very non trivial. Yeah, and so it
takes a long time to catalog the debris, and that's
a period you're not getting warnings from those new objects.
So that's why new debris is very bad. Radars are
great up to about one thousand kilometers. A few thousand kilometers,

(17:38):
they're a one over art of the fourth law. If
the thing is ten times further away, it's ten thousand
times weaker reflected single. So for high orbit satellites, radars
really aren't the way to go, and we've been using
regular optical telescopes to observe the objects. And now we're
actually starting to deploy satellites in high orbit whose job

(17:59):
is to catalog all the other satellites and keep track
of them.

Speaker 3 (18:03):
Why is it one over out of the fourth? Is
it because you get one of our r squared from
your signal and then one of o are squared from
the bounce.

Speaker 4 (18:09):
Exactly right, it's one of our squared each way.

Speaker 3 (18:12):
Wow, I see. So that's difficult. It seems to be
like a really hard problem, even if you know where
everything is, even if there's nothing new, because radar is
just giving you locations, right, it doesn't measure velocities.

Speaker 4 (18:22):
Yes, there's a dopplers, but it's only one component. Oh right, okay, right,
you have arrange an arrange rate, and then you only
have a very approximate angular position on the sky because
the radar is very sharp, and so you need multiple
observations to kind of resolve that and do it. So again,
this is something they've been doing since the nineteen fifties,

(18:42):
and it was kind of manageable back then, and there
weren't that many satellites, and now it's getting a really
tough problem and you can see them struggling. There was
a recent Chinese satellite launch. Eighteen satellites went up about
a month ago, and it was only yesterday that Space
Farce started issuing orbital for them because it took them
that long to sort it out. It's a fascinating problem

(19:04):
and really technically challenging, and in the circumstances they do
a pretty good job, but it's not really good enough
for what we need today.

Speaker 3 (19:12):
Yeah, it seems like a lot of compute is required.
You have to know all these trajectories, predict where they are,
get the new data, update the trajectories if they are
dev from your prediction. I'm wondering about the security here,
Like there must be things in space that are like
secret spy satellites. Are those parts of your database? Is
the NSA watching you to see if you're tracking that stuff.

Speaker 4 (19:31):
If they're not, they're not doing their job.

Speaker 1 (19:35):
You've really acclimated to life in the United States Johnson, Yeah.

Speaker 4 (19:39):
Right, exactly. The secret satellites are tracked by the Space Force.
The US secret satellites, they don't release the orbital data
for that publicly. The Russian and Chinese secret satellites they do.
The Israeli and French ones they sometimes do sometimes that
so our friends they keep the cle one secret. But
for people we don't like, we just publish them. Very recently,

(20:01):
there was maybe one hundred or so secret US and
Allied satellites, and most of them were pretty big. Some
of the old big Bird Spy satellites are like ten
tons right in low orbit, and so they're as bright
as the brightest stars in the sky. And so in
order to get their orbits, all you really need are
binoculars in the Stopwatch, sometimes not even binoculars.

Speaker 3 (20:24):
So it's in this category of like officially secret but
totally obvious exactly.

Speaker 4 (20:29):
So, you know, we figure that a bunch of amateurs
whose hobby is to fill in the holes and let
the orbits of the satellites that aren't meant to be public,
and we feel fine about that because we figure that
if a bunch of amateur astronomers with binoculars can figure
out these orbits, the North Koreans can too, you know.
And so I think for a long time, the space

(20:51):
force were a bit of denial. The air forces was
there were a bit of denial that they would ask us,
what sensors are you using to detect our satellites up? Oh,
we look up, it's come on overhead. There it is.
And so I think now there's more of a realization
that actually pretty fruitless trying to keep these orbits secret.

(21:12):
And I think in the long run for safety of
space operations so that other people know not to bump
into them, the era of making the orbit data secret
has got to end, I think, and that's an active discussion.

Speaker 3 (21:24):
Have we ever had a secret satellite blow up or
turn into secret space debris?

Speaker 4 (21:29):
Absolutely, absolutely secret space junk.

Speaker 3 (21:32):
I never heard of that before.

Speaker 4 (21:33):
I think the most common case is the upper stage
from one of these satellites blew up and created a
lot of debris. And so for a long time those
orbital data were secret classified. But they kind of wised
up eventually and released that. So that's good. There's been
some improvements lately in the transparency of the system, which
I'm pleased to see that slowly. Know, there was a
lot of like Cold War mentality, and now it's sort

(21:55):
of even though we may be going to another Cold
War or whatever. But see, one of the big things
that's changed in the past ten years. As it used
to be I would give talks, I would say space
is about one third civilian government, one third military, and
one third commercial. Those days are gone. Now space is

(22:15):
overwhelming the commercial and that means that the incentives at
the government level right are to support the commercial industry,
and that means more transparency in terms of not having
to worry about being hit by secret satellite. There's other
transparency issues because companies want to keep their plans secret
and things like that for commercial reasons. So that's a

(22:37):
whole other issue. So times have really changed the last
five to ten years. It's been a dramatic shift towards
this new era of commercial space.

Speaker 3 (22:45):
And what's your interest in it? I mean, you're an astrophysicist.
Are you curious about this because you're just curious about
anything in space? Or is this like political advocacy where
you feel like, hey, space is for everyone and we
should all know what's up there.

Speaker 4 (22:57):
You know, it's changed recently. So yeah, I've had this
separate life since I was a kid of wanting to
know what was going on in space. And you know,
I found this list of the year's satellite launches when
I was about twelve, and I very quickly realized after
copying it down that it wasn't really that grain of list.
They could do better. And so fifty years later I

(23:18):
have the best list because I'm obsessive like that, and
so that was sort of my original impetus. And I've
got more and more dragged into the policy side. And
then as space has started to become so busy that
we humans are starting to have an impact on the
space environment, and part of that is an impact on astronomy.

(23:42):
My two lives of astronomer and space pundit have kind
of merged and very much now are becoming advocacy and
becoming the Cassandra saying, hey, guys, we've got a problem
here with the overwhelming effect that we are now having
the space environment in a lot of different ways, and
the need for new regulation to adapt to the new

(24:07):
environment that we're in.

Speaker 1 (24:08):
Well, let's take a quick break and when we get back,
we'll talk about policy and impacts. And we're back. So

(24:30):
there's all this junk floating around in space, and I'm
under the impression that part of why it's hard to
remove the junk from space is because there's policies that
make it difficult to take someone else's junk out of
space without like getting their permission first. Is that correct?
And what's holding us back from removing all of that
junk from space?

Speaker 4 (24:49):
Right? That is hard of it? And so yes, the
Outer Space Treaty says that unlike say, stuff abandoned in
the ocean, stuff in space you can't abandon it. It's
still your problem. And the outer space you didn't have
an idea of companies or anything like that. And so
if you want to put something in space your like SpaceX,
for example, you've got to get a license from your

(25:10):
government in this case of the US, and part of
that license is then the US as a country takes
on the duty of jurisdiction and the control of that satellite.
And so that means if there's an old Russian rocket
stage orbiting that's been abandoned for thirty years, I can't
go up and take it without getting Russian permission because

(25:33):
it's still theirs. And so that is seen by the
space lawyers, particularly in the US, as a big, big
problem that they don't want to they kind of run
and hide whenever you bring it up. I do feel
this is a solvable problem that no one wants the
space junk. One thing I'm encouraged by. So there's a

(25:53):
company called Astroscale which is based in Tokyo and in
the UK, and they've been recently through satellite around a
big old Japanese rocket stage, observing it as sort of
a preparatory mission to having the technology to remove it
from orbit. And I think companies like that that are
sort of have an international basis. If you can do
sort of bilateral thing where say a European mission takes

(26:18):
out a Japanese piece of space junk with both countries agreement,
you can sort of set a tone that you can
then grow later to go okay, so we've done this,
you see, we're not doing anything that fair. Yes, we're
cleaning out the orbit. Hey, Russian guys, can you join
us and help us get rid of your junk too?
And I think that's the way forward. But you know, obviously,

(26:40):
in the world political situation as it is, it's not trivial.

Speaker 1 (26:43):
And I was talking to someone the other day who
was saying that one of the problems with these technologies
for clearing out space junk. Is that you can say like, oh,
I'm going out there for space junk, and that's why
I've got the laser, and that's why I've got this
arm so that I can grab your space junk and
throw it down so it'll burn up in the atmosphere.
But that's all dual use. That laser can be us
to destroy someone else's satellite. That grappling arm you can
throw someone else. And that is that actually holding anything back?

(27:06):
Or are people just willing to accept that when you
develop the technology to remove stuff from space, maybe you're
also developing some dual use stuff to get used down
the road.

Speaker 4 (27:14):
I think it's an issue that people bring up. I
mean personally, I think that's good. I hate the term
dual use. It's like everything is dual used. You know,
I can stab you with my pen, yeah, I mean yes,
of course, any satellite that's maneuverable can be maneuvered to
kind of you know, smash into your satellite, right, yeah,
and principle, And so I think that's just an excuse

(27:36):
for not doing anything, okay, or just an expression of mistrust.
You know, that is gettable over in my opinion, but
it's going to take a while, so I think, you know,
the last ten years, we've seen a bunch of experiments.
The British in particular did a fun set of experiments
where they sent a harpoon at a target to try
and catch it. They threw a net around the satellite

(27:58):
to reel it in and catch it. So people are
trying crazy stuff, and we're sort of starting to settle
on Okay, what are the approaches that will actually work,
And I think then the next step is to go
and actually do it for real and starting. The first
people to do this were actually, surprisingly the Chinese. The
Chinese a couple of years ago, they had this navigation

(28:20):
satellite in geostationary orbit that had died and was just
drifting in the traffic lane, you know, And so they
sent up another satellite that went and locked onto it,
probably with a robot arm or something, and brought it
up three hundred kilometers into what we call the graveyard,
a sort of a space junk yard, and released it
there and then went back down to go look for

(28:43):
other target. And that was the first time that anyone
had actually done kind of garbage truck space debris removal
for real with a real piece of space debris, and
so you know the fact that the US hasn't done
that yet is frankly a little bit of better.

Speaker 1 (29:00):
Yeah, it would be nice for leading the cleanup.

Speaker 3 (29:02):
I have a sort of naive question as a physicist,
like if the natural environment is just the Moon, that
suggests that there's some process of clearing the near Earth
orbit of bits like that if you had rocks coming in,
they would naturally gravitate together or something. What is the
sort of timescale for nature to take care of this itself,
for it to like form a ring or to pull

(29:24):
together into a new moon made of space junk.

Speaker 4 (29:26):
If you just leave the satellite population as it is, yeah,
what happens? And yeah, let's say if the Earth were
a perfectly round, you know, point source, and the Moon
and the Sun didn't exist, then things were just orbit
forever without changing their orbital prepence. The Earth has an atmosphere,
and so below about one thousand kilometers there's just enough

(29:47):
atmosphere to have a headwind at all glo velocities that
will eventually bring stuff back down into the atmosphere, and
that timescale is every eleven years. We have the famous
solar cycle, the solar maximum that makes the atmosphere more dense,
and that basically clears out everything below five hundred kilometers
in one or two cycles. So if you blow five

(30:08):
or six hundred kilometers, you're going to re enter the
Earth's atmosphere within twenty something years. But if you're between
like six hundred kilometers and ten thousand kilometers, you're going
to stay orbiting for centuries to millennia. There really isn't
that much affecting you. The Moon's far enough out that
it's not really bothering you. Once you get beyond like

(30:30):
one hundred thousand kilometers, now you have to start worrying
about the gravity of the Moon and the Sun, and
that will squeeze and turn your orbit and it's fun. Actually,
there are weird things like the Kosi effect that exoplanet
astronomers are really into, but also apply in Earth satellite stuff.
There's a lot of parallels in the math.

Speaker 1 (30:50):
The bail just wants to know what's the Cose effect.

Speaker 4 (30:52):
So what it is is if you have an elliptical
orbit and there's another body like the Moon, tugging on you,
what it does is it's wheezes and stretches the orbit,
so it becomes more and less elliptrical in a periodic way,
and at the same time tilts the orbit relative to
the equator. So the satellite I work on, Shander is
in an orbit like that, and over a decade or so,

(31:15):
it goes from almost equatorial to almost polar and back again.
And the low point of the orbit started off with
ten thousand kilometers, it goes up to like fifteen thousand,
comes down to five thousand, back up again. And if
you get the Sun and Moon aligne you could even
have the low point go negative, which would be the
end of the mission because then you try to orbit
through the surface of the Earth. Doesn't work very well.

(31:37):
And so that's just one example of all the funky
stuff that can happen. The flattening of the Earth can
be important.

Speaker 3 (31:44):
What about the gravitation between the objects? Like I understood
that if you have some huge set of debris in
orbit around a planet, if it's close below the roach limit,
the tidal forces will keep it from coalescing. For listeners
who aren't familiar, the Roche limit is how close you
can get to a planet before its tidal forces will
pull you apart. We have tidal forces from planets because

(32:05):
the planet's gravity pulls on the closer bit harder than
on the further bit. But if you're far enough away
from the planet, your internal structure can still hold you together.
But if a moon, for example, gets too close to
a planet, those tidal forces will pull it apart, shred it,
and turn it into a ring. But if it's far
enough away, the self gravity will eventually pull it together
into a new moon. Could that happen eventually with all

(32:27):
of our space junk?

Speaker 4 (32:28):
I haven't done that math. I doubt it. I think
the total mass isn't enough to get self gravitating. We've
launched maybe twenty tons of stuff.

Speaker 3 (32:39):
That sounds like a lot, but I guess it's not
compared to an astronomical object yet.

Speaker 4 (32:42):
Yeah, not compared to even a fairly small moon. My
guess is that that would not happen.

Speaker 3 (32:49):
Maybe we should use a moon as a unit of
measuring how much space junk we put into this otter,
because it makes us feel better about it.

Speaker 4 (32:56):
The International standard Moon. Yeah, okay, I'll take that out
a consideration. Daniels.

Speaker 1 (33:02):
All right, so when you were describing Chandra's orbit, it's
becoming even more clear to me how hard it must
be to track all of these objects because they're all
doing their own sort of things while they're out there.
So we've got all of this junk that's sort of
hard to track, do you It sort of touched on
the Kessler syndrome. Let's dive into that a little bit more.

Speaker 4 (33:17):
So.

Speaker 1 (33:17):
Space is huge. How big of a risk is it
that we're going to start getting these feedbacks where everything
runs into each other. Let's talk about that.

Speaker 4 (33:24):
So space is huge, but lower orbit isn't that huge, right,
So if we focus on the busiest part of space
right now from the human point of view, which is
all the satellites between the bottom of the US atmosphere
and about two thousand kilometers, there's a lot of stuff there.
The average distance between any two objects it's about one

(33:46):
hundred kilometers, but you're going at twenty five thousand kilometers
an hour. So the analogy I always use is, you know,
if you're driving on the highway, we're always reminded the
faster you go, the further you have to the distance
from the car in front of you. Right, So when
you're traveling at twenty five thousand kilometers an hour. You

(34:07):
don't have a lot of dotch time in one hundred kilometers, right,
And so we do get collisions, and we're seeing them.
We're seeing small collisions that are maybe not destroying a
satellite entirely, but kind of breaking stuff off it. And
the trouble is that the collision rate goes as the
square of the number of satellites. So if you have
ten times as many satellites, you have one hundred times

(34:28):
as many collisions. So right now, the collision rate is
not that bad. Even so if you stop launching everything today,
the collision rate is high enough that eventually, on timescales
of a century, you would start to get this runaway
chain reaction.

Speaker 3 (34:44):
What's the collision rate like now, how many collisions do
we see per day or per year?

Speaker 4 (34:48):
I think we see two or three small ones per year, Okay,
maybe one big one a decade of order. And so
that is amplified by what we call breakup events. There's
not one satellite dumping another, but when the rocket stage
blows up, for example, and things like that, and we
have several of those a year, adding hundreds of objects

(35:11):
to the catalog each year from that kind of source
the number of debriogis is increasing. It's not like in
the movie Gravity, right, where everything goes to hell in
about half an hour. Right, this is something that plays
out as with most environmental things. Right, you slowly drown
in your own waste. Right, every year, it's a little

(35:32):
bit worse and a little worse.

Speaker 3 (35:35):
But it accelerates.

Speaker 4 (35:36):
Right.

Speaker 3 (35:36):
You were saying that the collision rate depends on the
number of objects squared. So every time you have an
object that breaks into two, you've increased the number, which
you know increases the rate of collisions. And that's the
feedback loop.

Speaker 1 (35:46):
Right, That's exactly correct, yes, And is this all going
to be exacerbated even more by additional constellations of satellite?
So SpaceX has their Starlink, but I think China is
planning something similar.

Speaker 4 (36:00):
I has made the first two launches of its Kianfan
thousand sales satellites. And you know, people have seen the
success of Starlink in providing communications in Ukraine, and so
all the militaries in all the countries want their own.
We must have control over it ourselves, Starling constellation. And

(36:21):
so I think in addition to the commercial interests, there's
military interests, and so yeah, we're going to see more
and more of these constellations come along. Amazon have started
deploying theirs. There's a company called e Space that wants
to launch hundreds of thousands of satellites. So this is
really happening. You know. What SpaceX will tell you is
they have this Wizzo algorithm that will fix it in software.

(36:45):
Basically that the satellites have these argone electric thrusters. They
accelerate argon atoms with electric potential from solar panels to
provide low thrust but very many miles per gallon rocket
engine that can do slow dodges, not fast dodges. And
so they're always calculating. You know, they're doing thousands and

(37:08):
thousands of small maneuvers to avoid each other and other
people's satellites, and they're like, we got this, you know,
we know how to do this. I think their math
works out if you assume that the you know, errors
are always Bell curve and you know, but that's not reality.

(37:30):
The reality is that, as we say in the trade,
errors are non Gaussian. They're not like random that someone
screws up and something goes very wrong and it only
takes two people and two different constellations to screw up
in the right way, as it were, for your algorithms
to just totally fail and you have a collision. And

(37:50):
so we've been lucky so far. But I think if
you up the number of satellites by another factor of
ten or so, the chances are that we're going to
start seeing collisions. Space has been quite careful. They're actually
retiring now about three hundred of their satellites that have
components that they feel a dodgy and might cause a failure,

(38:11):
and so they're bringing them down under control while they're
still working and incinerating them in the atmosphere, which is
a whole other environmental problem that's just emerging because you know,
messing with the chemistry the upper atmosphere, what could possibly
go wrong?

Speaker 1 (38:23):
That's worth trying for us so far.

Speaker 4 (38:25):
Yeah, right, But putting that aside for a second, you know,
they're trying to be what they feel is responsible bringing
these satellites down, but not all companies maybe are going
to do that. And for example, of the first batch
of can Fan satellites, seventeen of the eighteen have started
raising the orbits. One of them looks like it may
have failed in SIH and Tolmerle, which will leave it

(38:47):
up there for a century. If you're launching ten thousand
satellites and you have a one percent failure rate, say
that's one hundred failed satellites added to the mix. And
you know, so it doesn't take too any of those
to kind of exacerbate the problems.

Speaker 3 (39:03):
But these companies must be incentivized to solve this problem,
right They don't want to invest billions in their network
and then have them all be destroyed. They must be
clear out about it.

Speaker 4 (39:11):
If anything will save us, that's it. It's the bottom line,
and it's the used environment story that they will do
not enough about the problem until it starts getting bad
enough that they actually see economic losses due to the problem,
and then they will scramble to self regulate and do
something that will improve it.

Speaker 1 (39:32):
And on that positive note, let's take a break and
when we come back, we'll talk about implications for astronomy. Okay,

(39:54):
so you mentioned a little bit earlier in the show
that all of the starlink satellites, for example, are making
astronomy difficult. What is the magnitude of this problem right
right now?

Speaker 4 (40:05):
It's an annoying nuisance. But again, up things by another
factor of ten, and it becomes really difficult to do
certain kinds of science. And so the problem is this,
there are two problems. They're different for lower bit satellites
and high orbit satellites. For low orbit satellites they're so
low that in the middle of the night they can't
see the sun. They shine by your affected light, and
so they're dark, and so they're not really a problem

(40:27):
for astronomers in the middle of the night. They are. However,
if you have enough of them. For example, if this
espace company I mentioned really launches like one hundred thousand satellites,
you could get to a situation where there are more
visible satellites in the sky than visible stars.

Speaker 3 (40:43):
Oh my god.

Speaker 4 (40:44):
Especially like just at the limit of visibility, the sky
instead of being nice and dark, will be kind of
seething in this nauseous way. And then the brighter ones
will make it very hard to kind of recognize the
constellations because it's going to be so much traffic. It's
going to be like in the flight plat hat a know,
logan airport or whatever.

Speaker 3 (41:02):
But why these things bright? I mean, they don't have
lights on them, right, are they just reflecting the sun.

Speaker 4 (41:06):
They reflect sunlight, and they're big. They're big and low
and they reflect sunlight. The current Starlink satellites are thirty
meter span Oh my god, panels. They're not small. These
are not tiny CubeSats. They're one ton ish satellites. So
it's it's really a change in the environment for everyone
in the world, right, even if you're not a space

(41:27):
faring country, but you're like looking up at the sky,
you maybe have cultural connections to the sky, and now
suddenly you're seeing the sky changing. And one of my
colleagues was just out hiking in the wilds of Canada said,
you know, they saw like so many satellites now that
they would never have seen it a few years ago.

Speaker 3 (41:43):
Can they do something on the satellites to reduce the reflectivity,
like have an anti reflective coating or a sunshade.

Speaker 4 (41:49):
To SpaceX's credit, they are doing a number of things
that have reduced the brightness of the satellite. But then
they came up with this new model of satellite where
they had these fancy new mitigations, but they were also
twice as big, so it kind of canceled out. To
their credit, they've done a lot of work, but there's
still more that needs to be done. So then the
second problem is the high orbit satellites. They are too

(42:11):
faint because they're high up, they're too faint to be
seen by the average person looking at in the evening
of the constellations, but they leave trails on astronomical images,
and they're way way brighter than the distant galaxies that
we're looking at. And so you take this picture of
some you know, distant galaxy and you've got a big
streak going across the image, and you know, we're not

(42:32):
just trying to take pretty pictures. We're trying to measure
brightnesses of stars to like one or two percent accuracy,
and so just photoshopping out the trail doesn't entirely solve
the problem. And even if that works, if you have
one trail every five images, you do what we call
medium filtering. Basically you throw away the bad ones and
you just have to observe for longer than you otherwise

(42:53):
would have. So it's attacks, but it's workable. But then
you know, if you up the number right so that
it's like streaks on every image going crisscrossing, going every way,
that becomes pretty impossible to analyze in an automated way.
If you have, like you know, ten thousand images of
galaxies and you're trying to analyze them remote with an algorithm,

(43:14):
and trying to distinguish between the crisscrossing satellite streaks and
actual astronomical phenomena is going to get pretty impossible. You know,
there are some science that's going to be affected worse
than others. The Magellanic clouds our nearest galaxies are visible
high in the southern sky in southern Midsummer. Southern midsummer

(43:34):
is the worst for this because that's when the sun
isn't that far below the horizon. The satellites get illuminated
all night long, and in plausible scenarios five or ten
years from now, there are several thousand illuminated satellites all
the time in the sky throughout the night in midsummer.
We may be able to work around it with new

(43:56):
kinds of cameras that can turn their shutters off for
brief modes of time while the satellite is passing, triggered
maybe by a finer camera that spots the satellite coming over.
It's not trivial. That's money, right, that's money that we
don't have to re equip the observer trees.

Speaker 3 (44:13):
So Musk said, quote, I am confident that we will
not cause any impact whatsoever in astronomical discoveries zero. How
confident are you that that's the case.

Speaker 4 (44:24):
I am one hundred percent confident that he is wrong
about that. Okay, there are subtleties, right, and so for example,
there was a report of a flare in a red
shift eleven galaxy that was super scientifically exciting until it
turned out to be actually a satellite passing through the
field of view the telescope at the time. If you've
just got like an optical fiber on the sky that

(44:46):
you're taking a spectrum, right, you don't have an image
of the sky, it's hard to figure out that that
was a satellite. So there's all kinds of ways in
which this is like a new kind of contamination factor
that ranges from mild annoying to oh, we accidentally published
a wrong exciting result because there was no way to

(45:08):
tell that it was caused by satellite contamination.

Speaker 3 (45:10):
So if you were a dictator of the Earth and
you were in charge of this and everybody had to
follow your instructions, what would you do to allow us
to have this amazing space technology and worldwide network and
also do astronomy.

Speaker 4 (45:23):
Yeah, that's the challenge. I think we just need a
cat on the number of active satellites of a given
brightness at a given altitude. You know, we have caps already,
Like in geostationary orbit, there's orbital slots that get assigned
by the International Telecommunications Union. You can't just launch as
many geostationary satellites as you like. I think we're going

(45:44):
to have to go to that. In lower th orbit,
We're going to have to have some kind of orbital
slot thing, and that will then change the design trade
so that instead of launching ten thousand small satellites, maybe
you launched one thousand bigger satellites and that helps with
not bumping into each other as well. So I think
it's a matter of finding regulation that will yes, absolutely

(46:08):
let the space technology develop, but not in a complete
free for all way, and manage the resources that we
have in a sustainable way and in a way that
doesn't impact the environment and astronomy more than a certain amount.
And where I mean absolutely it's going to be worse
for us than it used to be. But I do

(46:30):
believe there's a happy medium where the astronomers could just
about kind of survive and the satellites can still make
bunches of money.

Speaker 1 (46:37):
So let's wrap up the show by asking the two
questions that we got from a listener. So Josh sent
us two questions.

Speaker 5 (46:44):
Here we go, Besides the stuff that just orbits the Earth,
what happens to all the other stuff? Does it just
go off into space, run into planets, moons and stars?
And parenthetically thinking that if they do hit planets and moons,
they just sit there forever, and if they hit stars,

(47:06):
I'm assuming they melt away.

Speaker 4 (47:08):
Right Well, even if they hit a planet, you know,
the typical planet hitting speed is going to be more
than enough to pulbarize you. We have, in addition to
the twenty five something thousand objects currently in orbit, the
sixty thousand objects that have been in orbit since Futnik,
there's about one to two thousand objects that we have
sent beyond Earth orbit, either to the Moon or into

(47:32):
orbit around the Sun. And they're poorly documented. I've been
trying to make a catalog of them, figure out where
they all are. Most of them will just orbit the
Sun forever, I say, forever. After a million years, there
are various effects that will cause them, probably the spiral
into the Sun or to hit a planet. But you
know we're talking million year timescales. These things are going
to be out there for a while, unless you know,

(47:53):
the Smithsonian goes and clangs them or something.

Speaker 1 (47:56):
With their gigantic budget.

Speaker 4 (47:58):
Yeah. Well, you know, a thousand years from hopefully it
will have ejective or one hundred thousand years from now.
We do have stuff in orbit around Mars. We have
stuff in orbit around Jupiter, and we have stuff on
the surface of the planets.

Speaker 3 (48:11):
Stuff you mean on purpose or space junk or both.

Speaker 4 (48:13):
Well, both, right, So we try not to have the
space junk hit Mars because and so what we do
is when we send stuff out in the direction of Mars,
we actually sterilize the probe, sort of bake it so
that there's hopefully no bacteria on it, so that we
won't contaminate the search for Martian life with bugs from Florida.

(48:35):
And then when we launch it, we actually deliberately aim
it away from Mars a little bit. We deliberately miss
a bit separate from the rocket stage. So now the
rocket stage is in an orbit that doesn't go close
to Mars, and then we make a course correction to
put the probe on course from Mars, and so that
way we avoid having the big sort of space junk

(48:56):
pieces that we launch an orbit around the Sun hit
Mars at least on the first time round. You can't
sort of predict far enough in advance to guarantee it'll
never hit, but hopefully the buzz will be done by then.
So that is, you know, this whole issue of you know,
protecting the environment of the other planets is certainly something
that people give a lot of thought to, but there is, Yeah,
there's a bunch of junk orbiting the Sun. One of

(49:18):
the things that I've been involved in is movement to
try and regulate this better and at least get people
to say what orbit they put their junk in so
that we can find it later. Occasionally we've accidentally catalog
space junk. Is, oh, we discovered an asteroid, and then well,
never mind that asteroid is on an asteroid, it's a
rocket stage. We would like you please, if you launch

(49:40):
something in the orbit around the Sun, give us the
orbital elements so that we can you know, disambiguate it
from asteroids. There's an asteroid mining company that's explicitly said
it wants to launch this survey probe next year and
they're not going to tell us which asteroid is going
to because that's proprietary information. Right. I think that's just
not okay. If you're flying a light plane in the US,

(50:02):
you have to file a flight plan. You should have
a file a flight plan. If you go to the asteroids,
that's public interest information. And so the American Astronomical Society
has issued a statement saying that we think that interplanetary
orbits like we're like those solar systems are area and
if you're going to be in it, we think you
should publish your orbital data and not keep it secret.

(50:22):
So we'll see if we can make that stick. But
that's going to be an area of discussion in the
years to come as more and more activity. You know,
it used to be that the deep space arena was
just NASA, JPL and the Soviets, right, and now it's
all kinds of developing countries. The UAE has a Mars orbiter,

(50:44):
India has a Moon Landers and private companies like SpaceX
are launching stuff to the Moon and Mars and so
we really need to do a better job of keeping
track of what's out there.

Speaker 1 (50:57):
Yeah, And speaking of keeping track of what's out there,
Josh is the second question is right on point there.

Speaker 5 (51:02):
This is probably more speculative and harder to answer. But
in the event of the existence of advanced extraterrestrial beings,
what might they into it about us? If or when
they do find the random fastener or rocket booster or
humanoid poop? Would they be curious? Would they be bored?

(51:25):
Would they be disappointed? We were so wasteful with the
stuff we ejected into the space trash can.

Speaker 4 (51:33):
Yeah, I think they're out of you is going to
be well, what those guys went extinct?

Speaker 1 (51:43):
Well, I'm hoping our clean up methods really get much
better in the coming decades.

Speaker 4 (51:47):
Yep, you and me both.

Speaker 1 (51:48):
Yeah, fingers crossed.

Speaker 3 (51:50):
Have we had elements of space junk that we think
have gone interstellar, that have left the Solar System? You know,
basically the inverse version of Abilobe's omuamua.

Speaker 4 (51:59):
Yep. Absolutely. There are a couple of pieces of the
New Horizons probe, one of the rocket stages, and a
couple of there are things called d spin weights that
are like you have a spinning rocket stage, you want
to slow it down, you unspool two weights on a wire,
kind of like a yo yo kind of thing, and

(52:20):
then they float off and take the angle the momentum
with them. And so that's like another class of space jungle.
That's like little pieces of space chapment. Just okay, they're
on their way out the Solar system, all right.

Speaker 1 (52:30):
So to wrap up, are you feeling optimistic about the future?
Are we going to get those caps on satellites? What
do you think.

Speaker 3 (52:36):
Before we go extinct?

Speaker 1 (52:38):
Yeah?

Speaker 4 (52:38):
I don't know, Kelly. I think that there is you know,
even in the companies, right, I don't want to paint
them as unfeeling corporate. You know, money is a little thing.
They do care about space, and so I think there
is interest in being responsible space citizens, and that, you know,
gets balanced against all the pressures that are pushing them
to be careless. And so I think it could go

(53:00):
either way. It's the usual environmental thing. It will get
bad enough that something will have to be done, and
then there'll be a scramble to try and fix in.

Speaker 1 (53:09):
I think that's a very realistic take on things, all right.
Thank you so much for being here. Today, Jonathan, we
had a lot.

Speaker 4 (53:14):
Of fun hide Vice. Thank you for having me, good
luck tracking everything.

Speaker 3 (53:17):
Thank you and listeners. If your planning to launch anything
in order to please please let Jonathan know.

Speaker 1 (53:31):
Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio. We
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