Some might argue that the journey is just
as important as the destination. When youâre travelling at high speed through
interstellar space, this takes on an entirely new dimension. We recently discussed the concept of a Generation
Ship, a type of interstellar vessel designed to cross the vast expanse of deep space and
keep its crew alive, or at least their descendants, as such voyages can take many decades or even
centuries to reach the nearest stars. During that episode we also discussed some
alternative approaches such as freezing people or using robots, cyborgs, or artificial intelligence
to do the job, concepts and technologies which have emerged in recent times, and which, even
if they donât replace the generation ship, are likely to be incorporated into it to address
some of the problems which emerge as we learn more about space travel. And weâll be exploring those new problems
and potential solutions as we follow up on that first episode. Today we will be looking mostly at the ships
themselves, the engineering concerns associated with getting such ships up to speed, keeping
them powered during flight, and slowing them back down when they arrive. Next time weâll look more at the problems
of transporting whole ecologies on such ships and transplanting them to alien worlds in
âExporting Earthâ, and weâll follow that with a deeper look into the psychological
and sociological difficulties in âArk of a Million Yearsâ. But for today, our focus is on that core ship. How do you get it moving, how do you keep
it powered, repair it, maneuver it around obstacles, and finally, slow it down on arrival? Big problems, and part of the solution to
those big problems is with big ships. They can carry more shielding, proportionally,
than smaller ones. They can carry more people of course, allowing
not just more hands to work on a problem, but a wider range of specialization and expertise. They can also carry more backups. But no matter how much we prototype these
ships, thereâs always a risk of catastrophic failure from something deemed acceptably improbable
or simply something we didnât even know was a danger. So in this regard, itâs not just about a
ship carrying more backups and redundant components, but having backup ships. Not just a colony ship, but a colonial fleet. Yet our title, Exodus Fleet, does not simply
refer to one such colonial fleet migrating out from our solar system. Weâve discussed first colonial ventures
before, today weâre a bit more interested in when interstellar colonization has entered
its pinnacle phase. Not one or two early experiments to the nearest
systems but a massive operation hundreds of years later. In the Outward Bound series weâve looked
a lot at the colonization of our solar system, and indeed even colonizing the Oort Cloud,
and our first trip to Alpha Centauri. In those videos, weâve usually taken a few
minutes to reference how this or that interplanetary colony could serve as a foundation for interstellar
travel. We will not repeat all of that today, but
what we saw was a budding solar empire gearing up to levels of industrial might that dwarf
anything we have nowadays, decades after the Industrial Age. They have room, and resources, for trillions
or even quadrillions of people to live with a degree of prosperity that would awe kings. These are also civilizations that probably
do not regard our solar system as having 8 planets. For all the discussion of Pluto and other
dwarf planets, itâs easy to forget that originally we had two classifications, minor
and major planets. Dwarf planets were added in between later,
and arguments about that topic have tended to eclipse that there are nearly a million
identified planets in our solar system. These may be minor planets but each one can
be home to new civilizations and nations, and those living on them are likely to view
the solar system as quite a cluttered place, consisting of much more than a Sun, 8 planets,
and some other stuff. Similarly they will probably better realize
what we tend to overlook in discussions of colonization. That we will want to colonize every star system,
directly from this solar system, within at least a few hundred light years of us, and
that those number in the hundreds of thousands. We will not be building a handful of colony
ships, we will be building millions of them over the course of a few centuries. Launching dozens or even hundreds of them
every single day, ships carrying tens of thousands of people and measuring kilometers in length,
probably each taking years to build and outfit, so that at any given time the drydocks of
the solar system may have a million or more vessels under construction. Such a task seems daunting, and yet only a
civilization creeping up on full solar colonization, what we call a Kardashev-2 civilization, has
any motive to send out more than a few colony ships. Until mankind has settled most of those million
minor planets, until we number ourselves in the hundreds of trillions if not quadrillions,
there are only a few reasons to settle another solar system. Even just a few colonies outside our solar
system gets some of our eggs out of the Sol basket, plus the voyage gives you a lot of
data and experience for doing it in the future, and the work of colonizing a system on the
other end does too. Simulations, even incredibly realistic ones,
can never match the real thing since the simulators canât program in what they donât know. Unmanned probes can tell us a lot, but manned
trial voyages make sense to acquire real data to overcome and adapt to any unforeseen issues
in future missions. But beyond that, you have no real reason to
colonize more until it is practical and desirable, but once you do, it makes sense to do it big. You have the resources to do it big too, if
you can do it at all, because all the devices and tech that let you miniaturize such missions
also make it easy to go about it in a grand fashion. A self-replicating von Neumann probe sent
to colonize and terraform the galaxy can stop at its first destination and get to work replicating
copies of itself, then terraform that system while some of the copies journey to new ones,
or it can just stop at the nearest asteroid in our own solar system and replicate there
first. Or it can just build tons of giant spaceships
humans could man too. Itâs hard to guess how humanity will roll
out to the stars, but just as two examples, on the extremes, we might grow our population
locally on the slow side, just 1-2% population growth a year as we have in the last century,
and sometime around the year 3000, as weâre filling up most of the easy targets in our
solar system and number around a quadrillion people, decide we need to build several million
ships and send them all off crewed with tens of thousand of people each. Such an endeavor would use up not even a single
percent of our economy to build by that point, even if we were doing it with modern production
rates, and use such a small percent of our population that most of us may know only a
single colonist who was a casual acquaintance at most. On the flip-side, someone might get a clanking
self-replicator going in the next few decades. Indeed Iâd actually be surprised if that
didnât happen, and such things are not, in and of themselves, dangerous in the way
popular culture imagines Skynet or any sort of grey goo. Nothing very sophisticated need necessarily
be involved, and itâs certainly possible, since nature and humans produce stuff all
the time, the difference being that natureâs modern complexity is the byproduct of billions
of years of trial and error corrections, and humans are smarter than our factories, and
can function in a versatile fashion when incorporated into one, saving a lot of trickier steps in
automation. Were that to occur, we could start building
giant ships in space a few years later, and if we could talk 100 Million people, about
1% of our population, into getting on board these, say 100,000 people to a ship or small
fleet of ships, we could launch 1,000 expeditions a year later and settle most of the star systems
within a hundred light years of us. Thereâs no ifs on that, no other missing
technologies. All you need is a self-replicating machine,
be it a tiny nanorobot or a factory complex, that before breaking down is able to make
two complete copies of itself and do at least some other work while itâs at it, like refining
metal and making simple hull plates for a ship. All the other tech we discuss here can help
with that, make it easier and better, but nothing else is actually needed. Itâs making all these interstellar ships
small enough we can build them, and yet still large enough able to survive the journey with
its crew and equipment intact thatâs hard and high-tech. Here on SFIA, we tend to like to incorporate
fusion into spaceships, tech we donât have yet, but if we got it that gives us interstellar
travel, as it would be capable of providing the necessary speed, the power to live through
the journey, and the ability to slow down on arrival. That last one is the trickiest part. Since we have discussed fusion a lot for spaceships,
today we are going to look at an alternative. Thereâs quite a few, but we settled on the
lowest tech and fastest one we could come up with. This will incorporate the Stellaser we looked
at in Colonizing the Sun, a stupidly powerful and long range laser that requires little
more than large mirrors orbiting close to the Sun. We will also use fission or radioactive decay
power plants for the journeyâs power source, explosives for any fast maneuvering, and weâll
review a few options for slowing down. Fusion is still nicer, even if you are using
the Stellaser to get up to speed, since itâs all self-contained, but it isnât actually
necessary. Ship size is also highly variable, as is overall
design, and is ultimately very dependent on available technology. The higher your tech, the smaller your ship
can be and safely bring along everything you need. But this is mostly a matter of scale. Hypothetically, while a generation ship could
cross the cosmos at 1% of light speed or lower, this should never be necessary. We should have no problem at all keeping a
laser on a big target like several square kilometers of reflective sail till way out
past Pluto, and if the ship and crew can handle a 1 gee acceleration, the equivalent of normal
gravity, theyâd be out past Pluto in just two weeks and cruising off at 4% of light
speed, arriving at Alpha Centauri in a century and any of those 1000 or so nearest solar
system in under 2500 years. This is, incidentally, slow enough to brake
from using some of our existing fission based designs. This is important, since you have to be able
to slow down on arrival, but weâll come back to that in a bit. The longer you can keep that laser on the
ship, the faster it can go, and speeds far in excess of 4%, or even 40%, of light speed
are on the table. We talked about that more in Interstellar
Highways, but to do this you need to either make the sail bigger or the laser more focused,
and eventually that becomes impractical unless you have stations along the way helping out
to re-focus the beam or emit one themselves. Those stations need power and your ship needs
power once itâs off from the laser, and keep in mind once youâre light-days away
from the source, they need days to even be aware that thereâs a problem if the beam
goes off target. Also it doesnât have to be a light beam. Microwaves are handy, as we discussed in power
satellites, so is a particle stream. For that matter you could do what we decided
to call a Pacman ship, one that catches up on supply or fuel pods launched ahead of it
and eats them, or where the pods are launched afterward, but faster, and catch up to the
ship. The big constraint on acceleration with a
manned ship is what the crew and cargo can handle, so a pod whose structure and contents
can handle 100 gees instead of one, can accelerate to a final speed ten times higher than the
manned ship could on the same track length, for however far your laser can stay on target. Trying to coordinate all those pods to reach
the ship, or be caught up to by the ship, at the right time and place and at a speed
it can intercept safely, is a bit tricky, but you can afford to lose some of those. Moreover, it means the ship needs some way
to maneuver a little bit. We want that anyway though, so that it can
change directions to a new system if something turns out to be wrong with their destination
as they approach. The most logical one, for this setup, would
be an ion drive. They are slow to accelerate, but provide a
great acceleration to fuel mass ratio, so long as youâre patient. They can let you make some course corrections
and grab some supplies, and firing them up occasionally to do that also helps makes sure
theyâre still working as they should. Weâll get to whatâs powering them in a
moment, but those pods represent our first example of what we mean by a colonial fleet. They can be strung out behind and in front
of you, gathering information, acting as relays from back home if signals are getting weak
or youâre off your original course, giving you advance notice about any dangers in front
of you, mapping out the destination system and alternate systems ahead of you, and so
on. Now if you do see something dangerous in front
of you, youâve a number of ways to deal with that, and the sooner you see it the better. We talked about that more in the Interstellar
Travel Challenges episode, but if you havenât got much time to dodge something ahead, you
either need to vaporize it, which takes power or explosives, or dodge it quick, which an
ion drive canât do. Ironically shaped explosive charges on your
outer hull are probably best. They can sit there for long times and still
be detonated as fast as thought, or even your navigation computerâs thought. So long as youâre not getting excessive,
it can give you a quick shove to the side without damaging the ship or killing everyone
inside from too fast of an acceleration. You donât want to be standing on the ground
of a rotating section of a ship when it suddenly bucks at 5 gees for a second and you find
yourself twenty-five meters off the ground and falling back down. Needless to say everything in there just experienced
that too, so as you plummet, youâre doing that alongside all those nice ponds and forest
critters you landscaped in there. So the ship wants to do the minimum shove,
and you do want that automated, so it can react as fast as possible and with the smallest
shove needed to dodge some unseen rock it canât vaporize in time. The case we just mentioned was extreme, and
potentially very lethal to many inside, but less so than getting hit by a few kilograms
of relativistic space debris, and having a computer figuring out what the options are
and picking the least horrible action is ideal. This is another reason you want a fleet, not
a ship. The bigger your ship is, the harder it is
to dodge, and ultimately you have to worry about any lone ship getting destroyed by an
improbable event. However a pack of ships moving together, but
say 100 kilometers apart from each other, gives a lot of redundancy. They donât need to actually leave or arrive
at the same time either, they can use a little slow thrust to get into formation for the
long voyage, and at 100 kilometers apart, nothing they could encounter would cause a
chain-reaction threat to each other, even a ship with an antimatter drive isnât carrying
so much energy that if it exploded it would destroy it siblings at that range. Itâs still close enough for shuttling back
and forth too. These ships may all be plowing through space
at a decent percentage of light speed but they are not moving relative to each other,
and thereâs no air to cause drag between them, so a shuttle can just pop back and forth
between such ships. That wouldnât take much fuel but it doesnât
actually have to take any. Truth be told those ships donât really need
to be that far apart, but this is space and they can just launch tethers between each
other for a pod to ride around on. Indeed if theyâve got enough tethers and
those are strong enough, they can actually use those as winches to move each other around. Itâs weird to think of them this way, but
in many ways, for these long voyages through emptiness, these are not ships, theyâre
space stations, and they could assemble all sorts of stuff between each other during the
mission. Indeed, they might all sit at the outer corners
of a very large thin mirror being used to keep a beam on them longer than otherwise
possible. Once they are at cruising speed, everything
is relatively stationary, they can drop a telescope off to a side, extend pods out serve
as temporary extra space, and so on. All of these ships are likely to have a lot
manufacturing capability of their own and considering the voyage duration, a temporary
structure behind the ship made for some extra elbow room that has to be brought in and recycled
eventually isnât likely to be a concern, as âtemporaryâ is decades or centuries. Your big concern in that regard is that, depending
on your speed, you have a rather large radiation wind coming in from plowing through the interstellar
medium. The faster you go, the worse this is, the
faster your exterior add-ons will break, and the shorter youâll get to use them. So thereâs presumably a velocity at which
these shanty towns around your armada get pointless. Though you can also carry such things behind
you, shielded from that by your ship. The other handy part about those multiple
ships is that when the time comes they can all split up for multiple destinations, rather
than just one planet in a solar system. You wouldnât be likely to head straight
for a planet you want to terraform, it makes more sense to set up your space infrastructure
first when you arrive, rather than landing and having to rebuild all that launch ability
when you need it, which is probably right away, since a planet needing water for terraforming
is best bombarded with icy comets before you start building homes on it. But what is powering everything? Initially that Stellaser beam of course, and
they can turn that on low and just let it send a decent trickle of diffuse power for
quite some time after youâd be out of main pushing range. Potentially, this works for the whole trip,
but I personally wouldnât trust that on its own. After that, of course, if youâve got fusion,
that would be nice, but if not, we have both fission and passive decay, radioisotope thermoelectric
generators. Fission is handy on such ships, pound for
pound of fuel, itâs almost as energy dense as fusion, and if radiation and waste is a
concern, you can tow it behind you and kick your trash out the side, where it will sail
off into the void never to trouble humanity again, unless a big wad of fission products
slams into some alien civilizationâs home world at relativistic speed of course, which
might cause a diplomatic incident. But an RTG holds some interest for us too. These produce a nice, long, stable, albeit
inefficient power supply, and so long as you pick an isotope with a half-life similar to
your voyage time, you have an object supplying energy, and heat, which ships need in the
interstellar void, that is so dumb-simple and durable that it is foolproof. Many of them would ironically make excellent
radiation shielding too, and decay into byproducts that are quite safe and handy. If youâre worried about skills and abilities
being lost during a voyage of many centuries, or even millennia, a bunch of RTGs running
some very sturdy LED lighting might keep a habitat lit that whole time and livable. I wouldnât want to bet my colony on it though,
since you have a lot of time for things to break, hence why you need onboard manufacturing
ability and the expertise to use it, but thereâs not many things as sturdy or reliable as an
RTG. Okay, now the big challenge, slowing down. Reaching your destination as fast as possible
is nice, but the faster you go, the harder it is to slow down, and we would like to do
it with no fuel. At all, not one drop. This is easy on Earth, if you want to slow
down, just wait, friction and drag will get the job done. But in space we have neither. Except we actually do. There is no vacuum, just relative degrees
of emptiness, and the faster you are going the more you are slowed when you hit any random
speck of space dust. As on Earth, we can slow down faster by extending
a parachute, so we hit more space dust. This wonât be viable to slow you all the
way down probably, but every bit of speed you can lose this way saves you fuel. A lot too, under the classic rocket equation,
a ship that massed a megaton, half fuel, half payload, changes speed 69% of whatever the
exhaust velocity of that propellant is. To do double that, it would need to be 750
kilotons fuel, and 250 kilotons payload, and to quadruple that it would need to be just
60 kilotons of payload, and 940 of fuel. So even though your parachute might cost a
lot of mass itself, if it can let you slow down from 40% of light speed to just 10%,
that is an immense savings in fuel. Another option is the Bussard ramjet, which
originally looked promising as a way to propel a ship by having it magnetically suck in passing
hydrogen gas and slam it down a nozzle to collide and fuse and produce thrust. Only on examination it turned out that it
would actually lose more energy than it would take in, causing the ship to slow down. Not good for propulsion but just fine for
braking. And so too, a magnetic field dragging on a
huge volume of charged particles in the interstellar void, is also a good giant parachute. Somewhat energy demanding though, similarly
that physical parachute, even if itâs just a couple molecules thick, has to be rather
massive, though you could probably use it for forward shielding or make it during the
voyage, stick it out to slow you down, drag it back in and recycle it once youâve slowed
and itâs taken damage. Ideally weâd like to use a laser to slow
us down, but there isnât one on the other end yet. This is one case where extra ships are handy
as you can all transfer a lot of fuel to one ship in your fleet, have it pick up some extra
speed while slowing its sister ships down a bit, so it arrives sooner, and then build
a stellaser at their destination to slow them down. Robotic probes could do this, or even a satellite
which simply includes the mirrors needed for the stellaser. Of course the point of such a pushing laser
is to focus light. As you approach a star, you will be getting
more and more anyway. Even a probe with a rather large solar sail
wonât slow down too much before ramming into a star this way, but if it is concentrating
that light to shoot behind it or power a laser beam, it could push on another probe behind
it, which can slow more and thus have even longer to decelerate from light from that
new Sun. As can the one behind it. Indeed they can do some sun-diving and use
that mirror braking on the Sunâs atmosphere before colliding or disintegrating to slow
even more, giving them more time to push on their siblings. Each one of these can be taking more and more
detailed photos of the system as they go in, and as this chain proceeds you eventually
get one slow enough to finish braking in the Sunâs upper atmosphere without being destroyed,
and now you have a big mirror near a Sun, and then another, and now you have a Stellaser
that can push on your incoming fleet. Smart self replicating probes might be nicer,
but this is a comfortably low-tech approach that works, and involves no dangerous AI either,
though at least AI used here are just a few months or years ahead of your Armada, not
roving hundreds of light years ahead and mutating outside your scrutiny. You could also use these probes to skim past
the star, do a course correction, and keep bouncing light to their siblings on their
way out to the next star. Itâs a little debatable if we can say this
doesnât use fuel, since you are still using mass for those probes, but overall itâs
a nicer approach than most others on the table with our current tech, and of those, the most
obvious one is probably to slow down by launching hydrogen bombs in front of you. Of course that works for these too, since
they are essentially just a giant sail, and they could detonate a bomb quite a long way
ahead and slow down on that themselves, which gets around the problems of detonating a nuke
right in front of your manned ship. The other nice thing is you only need that
last probe, or last two probes, to carry a full-sized pair of mirrors for a stellaser,
and the number of ships and mass of those ships doesnât matter too much toward that,
especially since you could send in another bigger pair of mirrors for that first stellaser
to slow down, your whole fleet can now slow down as can any subsequent vessels following
behind you, who can follow even faster now that the infrastructure is in place. Once down to more modest planetary speeds
you can use the usual array of methods to finish slowing if you need to. Not all of those require fuel either, for
instance gravity-assist, so often used for speedings ships up, can also be used to slow
them down. Weâll look more at how big these ships need
to be in the next installment of the series, Exporting Earth, in order to contain all the
ecology weâd need, but for today weâve established that even just with current technology,
weâve got what we need to reach other solar systems far faster than the original generation
ship concept envisioned. So we were talking about how to get out beyond
our solar system today and how weâd be able to use the Sun to power those efforts. While the basic principle is sound, thereâs
still so much we need to understand about our own sun before we can visit other ones. Thereâs a lot of other reasons to go study
the Sun up close and our friends over at Cheddar have just released a video discussing those
reasons and what NASA is doing to find out more. Iâll link it in the video description. Theyâve been sponsoring science videos like
this one and recently started their own channel covering topics like this and many more, and
Iâd suggest checking it out and donât forget to subscribe while youâre there. Hey guys I'm Patrick Jones from Cheddar and
I'm here today because we made a video that I tihnk you're really gonna like. It's all about two upcoming missions from
NASA and the European Space Agency to study our Sun. So if you like Isaac's channel, like we do,
we think you'll like our video and our channel. So come on by! Next week we have a two-parter, as we team
up again with Joe Scott of Answers with Joe. Weâll examine 5 ways the world might end,
then what we could do to prevent those happening. The week after that weâll be discussing
what sort of careers folks might pursue in an increasingly automated workforce, in Jobs
of the Future. For alerts when those and other episodes come
out, make sure to subscribe to the channel, and if you enjoyed this episode, hit the like
button and share it with others. Also as a quick note I did an interview with
Matt Ward of FringeFM a little while back, and Iâll leave a link to that in the video
description too. Until next time, thanks for watching, and
have a great week!
I loved the "all you eggs in one Sol system" pun.
The suicidal satellite breaking is something I had never thought of.
This stronfly reminded me of that Kim Stanley Robinson novel, Arora.
This episode seemed to me like a recap of previously mentioned ideas, nothing new for SFIA fans. But probably good one for newcomers.
Issac mentioned 1G of acceleration of a light sail stellaser combo. is that feasible is that. how much incoming light would be needed and would it damage the sail.
even if you start with a perfectly reflective sail it wont stay that way, its going to get hit by dust and have dust settle on it. the light can be absorbed by this material causing heating damaging more of the material, this will not end well.
you need to keep the incoming light level low enough that it wont heat imperfections hot enough to damage the reflective properties of the rest of the sail. can you do that and expect a massive ship to hit 1G.
Can anyone tell me how big of an impact a single atom has at relativistic speeds? Could it damage steel, or if not that, maybe some solar panels?