where you can travel in space depends on how much propellant you've got onboard
your rocket and how efficiently you can use it but there's a source of free
propellant right here in the solar system the Sun which is streaming out
photons in all directions you just need to catch them and right now the
Planetary Society's new light sail 2 spacecraft is testing out just how well
it'll work solar sails are an ingenious idea that were first thought of by
johannes kepler back in the 1600s as he imagined that sails and ships could be
adapted to space travel of course he didn't fully understand the physics
involved yet but with major discoveries in particle physics and quantum
mechanics in the early 20th century scientists realized that light itself
could act like a wind that blows a sail in space although photons have no mass
they can impart momentum when they bounce off a highly reflective surface
this is a light sail it's not very much but in the vacuum of space there's no
air resistance to slow down the sail with enough photons and enough time a
light sail can accelerate to incredibly high speeds using a chemical rocket you
could convert the entire mass of the observable universe into rocket fuel and
you couldn't get a small spacecraft going faster than 0.2% the speed of
light but a light sail can theoretically take you up to relativistic velocities
traveling from star to star in human lifetime since unlimited free propellant
comes from the Sun and huge velocities are possible why are there solar sails
everywhere good question it's a question that the Planetary Society has been
obsessing about for years and they've launched a solar sail to try to figure
out how well they actually work back in 2005 they tried to launch the world's
first solar sail cosmos one but rocket failure destroyed it then they went back
to work developing light sail one which was launched in 2015
and successfully tested their solar sail deployment in space and finally in 2019
the Planetary Society was ready to actually try sailing in space on June
25th 2019 a SpaceX Falcon Heavy blasted off from Florida's Cape Canaveral
carrying 24 spacecraft for the US Air Force's step2 mission this was the third
time the Falcon Heavy had been launched and we were all hoping it would
successfully land it's middle stage not so much that's still on the to-do list
but that's how what this video is about anyway in addition to the mysterious Air
Force satellites Falcon Heavy was carrying the planetary society's light
sail to onboard its procs one carrier spacecraft which are released at an
altitude of 720 kilometres then on July 23rd 2019 the spacecraft deployed its
solar sail it opened its hinged solar arrays and then unreeled for tape
measure like sail booms reeling out its four triangular sails deploying 32
square meters of sail area it's important to note that this spacecraft
is tiny with a weight of just 5 kilograms or 11 pounds about the size of
a loaf of bread as it orbits around the earth the spacecraft swings it sails
into and out of the sunlight with each period raising its orbit by a few
hundred meters a day that sounds great unfortunately light sail too doesn't
have the control systems on board to control its angle carefully enough to
remain in orbit indefinitely while it's raising its orbit on one side of the
earth by several hundred meters a day it can't tilt the sails precisely enough to
prevent lowering its orbit on the other side of the planet eventually it'll dip
into the Earth's atmosphere and burn up but hopefully engineers at the Planetary
Society will have finally learned how practical a solar sail can be for space
exploration it's still in orbit at the time I'm recording this video and
sending back awesome pictures of our home planet and I'll put links in the
show notes where you can download them and turn them into your new phone
wallpaper thanks to the Planetary Society we've got their test of a solar
sail arthur c clarke would be pleased but there are some other interesting
ideas for solar sails of the future and i'll get to that in a second but first
I'd like to thank Denis Dattilo Ron Stowe Brian gray the giant nothing and
the rest of our 796 patrons for their generous support they contribute so that
you can see these videos and we can make them freely available to anyone who
wants to learn about space join our community at patreon.com - universe
today and get in on the action with the Planetary society's light-sealed -
sending home data teaching mission controllers to sail in space these will
be valuable lessons for future missions that might use this technology as an
actual method of propulsion one mission in the works is NASA's near-earth
asteroid scout or Nia scout this CubeSat mission could fly as a secondary payload
with the first test of NASA's Space Launch System the uncrewed em1 mission
which could launch as early as June 2020 after deploying from the Orion capsule
neoscope would unfurl its solar sails twice the size of Lights Hill - and then
spend two years traveling to a near-earth asteroid to study it up close
we don't know the target yet but a potential destination might be the
near-earth object 1991 VG which was discovered in 1991 shortly before it
passed about the distance from the earth to the moon away from us and they came
back in August 2017 we'll want to keep an eye on this rock as a potential
threat but also as a treasure trove of metals and minerals that could help
support future exploration of the solar system another mission that could use a
solar sail as Japan's oversized kite craft for exploration and Astronautics
in the outer solar system or Okeanos this would be a mission to the Trojan
asteroids which are located at the l4 and l5 Sun Jupiter Lagrange points these
are an ideal place to study asteroids because Jupiter and the Sun's gravity
have trapped a large number in one spot and a mission can easily sample many
different asteroids Okeanos would have a hybrid solar sail covered in solar
panels which all to use to provide electricity for
its instruments and ion engine Japan was one of the first countries to ever test
a solar sail with their ocurro's mission which was deployed in 2010 and
eventually gained hundreds of meters a second of velocity using a solar sail
Okeanos might even come with a lander thanks to their experience with Hayabusa
- and asteroid ryugu JAXA has learned a tremendous amount about landing and
collecting samples from tiny asteroids if all goes well okay uh notes we'll
launch in the mid-2020s onboard an h2 a launch vehicle using several gravity
assists to make the journey out to Jupiter and if the mission is really
successful it might even bring a sample of a Trojan asteroid home NASA is even
considering adding a solar sail to the deep-space lunar gateway at a special
planning event for the deep-space gateway in 2017 members from the
Canadian Space Agency presented the concept of a solar sail that could be
added to the station the ongoing light from the Sun would provide a constant
thrust that the station could use to maintain its orbit without propulsion
held out on a Canadian robotic arm what else a 50 square meter solar sail could
save the station nine kilograms of hydrazine a year which is expensive to
carry up from the earth to the moon one mission that you're probably familiar
with is the breakthrough starshot concept instead of using light from the
Sun as propulsion breakthrough starshot hopes to use powerful lasers which will
accelerate tiny satellites to interstellar velocities these could be
the first spacecraft that ever sent home images from another star system and
we've done a whole episode on this and another heavier laser sail mission
called Project dragonfly and I'll put links to these episodes in the show
notes unfortunately it's taken longer for
space agencies to incorporate solar sails into their missions than I would
have hoped it's understandable they're complicated and fragile and require
precise orientation it makes sense that mission planners would use
tried-and-true chemical rockets or efficient ion engines to propel their
spacecraft across the solar system but as more and more solar sails are
launched and tested engineers will become more
confident at the best ways to use them as part of a mission
I can imagine future when almost every mission has a backup solar sail onboard
just in case something goes wrong with the main engine I've always been
fascinated by the possibility of solar sailing and I've watched each discovery
and step forward with excitement I'm really glad the Planetary Society
has made it this far with their tests they did the entire mission for 7
million dollars funded by Planetary Society members
private citizens and a Kickstarter campaign so if you want to support this
in future missions to help explore the solar system go to Planetary org and
find out more what do you think limitary thoughts in the comments once a week I
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