the distances between stars are so vast
it's hard to wrap your mind around it
even our far-flung voyagers have barely
reached interstellar space and would
take tens of thousands of years to even
get to the nearest star but scientists
and engineers are considering what it
would actually take to send a spacecraft
to another star
it's called project dragonfly and would
use existing or near future technologies
to send a serious spacecraft to Alpha
Centauri within a hundred years we're in
the golden age of exoplanet discovery
with thousands and thousands of new
planets already discovered and the pace
is just picking up but the sad reality
is that we'll never know more about
these planets than radial velocity
measurements or the dimming of light
from the parent star we can know the
mass or the rotation rates but for the
foreseeable future we won't get much
more than a couple of blurry pixels we
want a closer look we want to send a
probe from here to there within our
lifetimes if possible to see what those
other worlds look like up close we want
to send a Tercel a spacecraft now
several groups are considering this kind
of mission and they're investigating
laser sails as a method of propulsion
using the momentum of photons to
accelerate a spacecraft
now the most famous right now is
breakthrough starshot which wants to
send lots and lots of tiny spacecraft
accelerated by lasers but each one won't
be able to send much of a payload to
another star but could we send a larger
probe across these vast distances let's
talk about project dragonfly now before
I go into this clocking about project
dragonfly the interstellar spacecraft
and not project dragonfly the Google
initiative to make a search engine for
China and I'm definitely not talking
about the secret airforce project to
replace fighter planes with genetically
modified super dragonflies but I've
already said too much
in 2014 the initiative for interstellar
studies announced a student competition
called project dragonfly where various
teams would propose interstellar mission
designs using light sail laser
propulsion systems for finalist teams
were chosen and a winning team from the
Technical University of Munich was
chosen their proposal is different from
the breakthrough starshot program that
I'm sure you're familiar with which
would send a vast Armada of tiny probes
at relativistic velocities instead this
design would include a much more massive
probe capable of being accelerated up to
five percent the speed of light but also
deploy a magnetic sail to slow itself
down at its destination and do a more
comprehensive survey of the place for
acceleration the spacecraft would use
laser beaming photons at a solar sail
traveling at high velocity requires an
enormous amount of fuel but solar sails
don't need to carry any fuel instead the
momentum from photons bouncing off a
reflective film imparts the velocity the
speed you can reach depends on the size
of the sail and the power of the laser
you're using to accelerate it they
calculated that a 100 Giga watt laser
could provide enough of a kick to
accelerate a 2,000 kilogram probe
attached to a 750 kilograms sail at 5%
the speed of light just to give you some
comparisons NASA's new Horizons
spacecraft has a mass of about 500
kilograms while Cassini has a dry mass
of about 2,500 kilograms so
imagine a spacecraft somewhere in
between the researchers proposed
building a satellite that would orbit at
the Earth Sun l1 Lagrangian which is a
relatively balanced spot in between the
earth and the Sun the satellite would be
equipped with a huge solar array that
would gather up the radiation from the
Sun and use that to fire a 100 Giga watt
laser now the most powerful laser ever
built is that the laser for fast
ignition experiments at Osaka University
Japan in 2015 it fired for a fraction of
a second blazing with two petawatts
that's 2,000 trillion watts which if you
do the math is 20,000 times more
powerful than the 100 Giga watt laser
that project dragonfly calls for
super-powerful lasers are in the works
to across the world such as the National
Ignition facility in California the
Quarles laser in South Korea and the
Vulcan laser in the UK and a laser with
10 times more power is being built at
the extreme light infrastructure
European consortium creating a laser
that fires at 100 gigawatts is feasible
with the technology that we have today
of course building it in space would be
a whole other challenge when it's time
to set off for Alpha Centauri satellite
would deploy the interstellar probe
which would unfurl its solar sail
measuring 30 kilometers across and made
of a graphene monolayer for the
beginning of a journey the probe would
use the light pressure from the Sun for
acceleration then it would make
planetary flybys using the gravity of
the planets to put it into the right
flight direction towards Alpha Centauri
once it was going in the right direction
and more than two astronomical units
from Earth the laser would fire at the
probe for 3.9 years accelerating on its
journey
over the course of the acceleration
phase it would reach five thousand nine
hundred and nine astronomical units from
the Sun or about point one of a
Lightyear it's colossal distance from a
human engineering point of view but
still a tiny part of the total trip over
this time the laser would continue to
adjust its focus of the beam continues
to fall on the sail and pointing the
laser will become a greater and greater
challenge even more challenging than
pointing space telescopes like James
Webb or Hubble and this is made even
more complicated by the time it takes
light to get to the probe the laser will
take more than a month to reach the
probe and any targeting adjustments will
need to be communicated back to earth
and take another month so imagine
waiting a month to hear a little to the
left and I'm sure you can imagine how
dangerous a laser like this might be if
pointed at Earth so one idea would be to
put the laser at the LaGrant on the far
side of the Sun where it couldn't be
used as a weapon against earth now
traveling at five percent the speed of
light the probe ejects its solar sail
and there would be decades and decades
of waiting as the spacecraft cruises for
81.5 years the engineers who built and
launched the probe would probably die
generations would come and go in between
and finally a new team ready to watch
over the next phase arrival of Alpha
Centauri and we'll get to that in a
second but first I'd like to thank
Brodie McLeod de Havilland Mosquito
baelish Suha de sac erick fluke Jim
O'Leary
Gertrude Braden Jeremy Kerwin and the
rest of her 808 patrons for their
generous support if you love what we're
doing gonna get on the action head over
to patreon.com/scishow stood a as I said
earlier a key distinction between
project dragonfly and other mission
concepts to Alpha Centauri is the mass
this is a seriously big spacecraft and
the ability to decelerate once it
reaches its destination and it'll do
this with a magnetic sail stars like the
Sun are
constantly blasting out charged
particles as stellar winds in fact the
interstellar medium the vast gulfs
between stars is made up of all the
particles fired out by all the stars in
the galaxy a magnetic sail works by
creating drag against this interstellar
environment so think of a parachute but
for space itself the spacecraft would
deploy a huge loop of superconducting
wire 30 5368 meters in diameter this is
one of the most challenging engineering
elements right now to make a
superconducting wire that would only
weigh a thousand kilograms would be the
very limits of our current capability
over the next 20 years this loop would
drag against the interstellar medium
slowing down the spacecraft's velocity
as it gets slower and slower the sail
provides less drag but everything will
have been timed so that it arrives
within the solar wind bubble of Alpha
Centauri at exactly the right time as it
gets closer and closer to the star the
stellar winds provide the most
deceleration when it reaches the inner
planets who will have decelerated enough
that it can now just maneuver itself to
any place it wants within the system
humanity would now have a fully
operational interstellar probe ready to
explore another star system sending back
the same kinds of photographs in
scientific data that we've been spoiled
with here in solar system Alpha Centauri
is a big place with twin stars like our
Sun and the smaller red dwarf Proxima
Centauri so many places to visit in fact
so many scientific mysteries that
choosing the spacecraft instruments
would be almost impossible instead of
sending a single spacecraft it might be
best to send multiple probes with all
the different instruments you would need
to fully analyze whatever mysteries are
encountered once the laser system had
accelerated its first probe it could be
used to send out a second third and so
on every 3.7 years another interstellar
probe would be on its way to a new
destination beyond the solar system I
really want humanity to explore other
stars and even if it doesn't happen in
my lifetime it would be an incredible
accomplishment it would make the vast
endless universe
seem a little smaller I hope we do it I
really enjoyed reading the project
dragonfly paper and I think you'll get a
lot out of it I'll put a link to it in
the show notes so what do you think let
me know your thoughts in the comments
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