The SpaceX Starship is currently humanity's best hope for setting foot on the planet Mars
in your lifetime. The feature that makes the starship so well suited for this
job is, of course, it's incredible power. There's no doubt that a
future starship will have more than enough muscle to send both crews and massive amounts
of supplies on their path towards Mars. Going up is one thing, but
what about coming back down on the Martian surface. We are talking about the
most complicated maneuver of the entire journey, the make or break moment, and
there's a lot more involved in figuring it out than you might think. This
is how the SpaceX Starship will land on Mars. Let's establish right now that
we are not all rocket scientists or physicists. I'm definitely neither of those things.
But luckily we do not need to be geniuses to understand the basic principles
behind interplanetary travel. So we're going to keep this all at a very accessible
level. Before we can talk about landing on Mars, we need to know
how the starship got there in the first place. The thing that we always
have to remember about space travel is that everything is always in motion, and
within the context of a solar system, everything is moving in an orbit around
the Sun. We are currently held in the gravity well of the Sun,
and the only thing that prevents us from falling down any deeper is the orbital
velocity of the Earth, which is approximately thirty kilometers per second. That's how
fast we are traveling right now in a big circle around a star that takes
three hundred and sixty five days to complete. Mars is further away from the
Sun than the Earth, meaning that it isn't as far down into the gravity
well as we are, and therefore Mars can travel at a slower orbital velocity
without falling in so Mars orbits the Sun at around twenty four kilometers per second.
Now, if we want to leave the Earth in a spaceship and explore
the planets, we will become yet another object spinning around in the gravity well
of the Sun. And just like the planet Earth, if we were to
slow down our orbital velocity, we would start to fall into that gravity well.
This will change our orbit in the direction of an inner planet like Venus,
and by the same mechanics, if our spaceship starts moving faster than the
planet Earth, we will rise up the gravity well, bringing our orbit towards
an outer planet like Mars. So traveling through the Solar System is all about
changing your velocity relative to your starting point. The technical term that we use
to describe this is delta V, where delta means change and V means velocity.
We typically measure delta V in kilometers per second. So if the Earth
is moving at thirty kilometers per second and you accelerate your spaceship to thirty one
kilometers per second, you have a delta V of one. By the same
measure, if you decelerate your spaceship relative to the Earth and travel at twenty
nine kilometers per second, you also have a delta V of one. And
yet, if you blast off from the surface of the Earth at one kilometer
per second, you are not going to begin rising up through the Solar System.
You aren't going to rise up above the Earth's surface because gravity and atmospheric
drag are holding you down. These natural forces will affect the amount of delta
V required to maneuver the spaceship. This is why it's so hard to get
from the surface of the Earth to outer space. The delta V required to
reach a typical low Earth orbit is going to be around nine point four kilometers
per second. That's a lot of acceleration, and that's why our starship requires
the massive power of the super heavy booster at launch. This is also why
the starship needs to stop for a refilling session in Earth orbit before it can
continue on to Mars, because we're going to need a lot more delta V
to complete this journey. In order to change velocity, we need propulsion,
and propulsion needs fuel. The advantage of filling up in orbit is that it
resets our starting point. From here, we only need another nine point five
kilometers per second of delta V to reach the surface of Mars, so basically
equal to the change required just to escape the Earth's atmosphere. But there is
going to be a big difference in the approach we take for the next leg
of the journey, because while escaping the Earth was all about speeding up,
landing on Mars is going to require a lot of slowing down and this can
be just as difficult to achieve. A fully fueled starship in low Earth orbit
is imagined to have enough thrust for somewhere between six and seven kilometers per second
of delta V. This obviously is a bit short of our nine point five
kilometers per second necessary to reach Mars. But that's okay, because the same
forces that made it so difficult to escape Earth's atmosphere, gravity and aerodynamic drag,
are going to work to our advantage when we come in for a landing,
effectively increasing the delta V potential of our starship. So here's how it's
going to go down. Okay, we are in orbit around the Earth,
but even a few hundred kilometers above the surface, we are still firmly caught
in the Earth's gravity. Well, the only thing keeping us up right now
is velocity. If the starship were to slow down at all, it would
start falling back towards the Earth. By that same reasoning, if we do
the opposite and speed up, then we will continue to rise up into space.
Because we are still so close to the Earth, we need a lot
of delta V to fight against gravity. The ship will have to accelerate by
two point four to four kilometers per second just to reach a height of geostationary
orbit. Another zero point sixty eight gets us through the height of the Moon.
Up Here, we are finally on the edge of the Earth's gravity.
Well, the force of gravity is infinite, but the power of attraction dissipates
relatively quickly as you move further away. Now, all we need is another
zero point nine kilometers per second of velocity to escape the Earth's influence completely.
From this point, floating in the vacuum of space far beyond the Moon,
we only require zero point three nine meters per second of delta V to achieve
our Earth to Mars transfer velocity. This second leg of the journey has used
up three point six kilometers per second of delta V, which is at least
half of the potential energy in our starship, if not more, and that
means that we do not have enough fuel left to successfully land on Mars with
engines alone. And here comes the problem that we need to solve. All
of the velocity that we acquired to escape Earth's atmosphere and gravity well has got
us traveling around the Sun at a significantly higher speed than the planet Earth,
which was already traveling at thirty kilometers per second to begin with. The planet
Mars, on the other hand, is orbiting at a speed of just twenty
four kilometers per second, so we are moving significantly faster than our target planet,
which means that we are going to overshoot the planet Mars and end up
stuck somewhere in the asteroid belt unless we start slowing down. After several months
of coasting through the vacuum of space, we need to execute our first deceleration
burn After flipping the starship around and getting the Raptor engines back up to speed,
we have to shave off zero point six to seven kilometers per second of
velocity in order to become captured in the gravity well of Mars. This is
the first step in what's about to become a very rough ride. If we
burn off another zero point three to four kilometers per second of velocity, then
we reach the height of the outer moon demos. Zero point four kilometers per
second of further delta V gets us down to the inner moons. Here's where
things get really tricky. By slowing down this much, we've already expended over
five kilometers per second of the potential delta V in our fuel tanks, and
that leaves us with somewhere between one and two remaining. But we need at
least another four and a half kilometers per second of delta V to safely reach
the surface. In theory, this is still possible as long as we are
very strategic about how we use our last bit of fuel, and it's important
to remember that everything from here on out is purely speculative. This is our
interpretation of the most logistically feasible Mars landing. If we want to conserve as
much fuel as possible for our landing burn, then we need to take advantage
of some external forces to slow our ship down to a reasonable velocity. Getting
down into a circular lo Mars orbit would use up most of our remaining fuel,
so we probably shouldn't do that. In this case, we might be
better served by inserting the ship into an elliptical orbit, so instead of flying
in a circle, we're moving in an oval pattern with a low spot or
peragy close to the planet and a high spot or apogey deeper out into space.
By using this maneuver, we can start to take advantage of both aerodynamic
drag and Mars gravity to help us slow down. The Mars atmosphere is still
very thin, but we'll take any help that we can get. We can
lower the peragy of our orbit down to the point where the ship actually dips
into the upper atmosphere of the planet. By doing this very carefully, we
can actually catch some atmospheric drag and lose a small amount of velocity before getting
flung back out to our apogee, where if we've done this properly, the
gravity of Mars will pull us back in to repeat the process over again.
Every time that we dip into the app hemisphere, we gain a little more
of that precious delta V, bringing us closer to the velocity we need for
a soft touchdown on the planet's surface. But we can't keep this maneuver up
indefinitely. Eventually we need to transition from a shallow dip to a full on
dive through the Martian atmosphere. It's actually pretty difficult to achieve a landing trajectory
from Mars because the planet is only around half the size of the Earth.
That means the angle of attack necessary to get down below the sky is pretty
steep. This means you need a lot of energy pushing the vehicle down in
order to prevent it from skipping off and shooting back up into space again.
We want to save our engines until the last possible moment, so that forced
to push the ship down deeper into the atmosphere needs to come from somewhere else.
This is why the original SpaceX, designed for an interplanetary transport system in
twenty sixteen, had an aerodynamic lifting body in the upper stage. Starship is
much smaller than its so it doesn't need as much aerodynamic force, but the
methodology is still pretty much the same. On its final approach, starship is
actually going to flip over and come into the atmosphere upside down, so that's
what the belly and tail pointed up and the nose pointed down. This way,
the lift generated by the body is going to push the vehicle towards the
surface on a steeper angle to achieve entry. We're also going to start losing
a lot of velocity thanks to aerodynamic drag. Once the angle of attack is
set, the starship is going to flip around into the more traditional belly flop
maneuver that we've seen on Earth. This is all about creating the maximum amount
of drag that is physically possible and getting the velocity down. But this force
can only accomplish so much. The maximum speed of a free fall is something
that we call terminal velocity. Imagine you jump into a bottomless hole. Your
body will accelerate as you fall up until a certain point when the drag and
bullyancy of your body equalizes with the force of gravity and your speed becomes constant.
One way that we cheat terminal velocity is by using a parachute. This
greatly increases drag and slows down our terminal velocity. Starship isn't going to use
parachutes, so there's going to come a point where the aerodynamic drag of the
vehicle has done all that it's going to do, and we reach terminal velocity.
Due to the thinner atmosphere, terminal velocity on Mars is around five times
faster than on Earth. In other words, that means you only get one
fifth the delta v accomplished by belly flopping through the air on Mars compared to
what we've already seen Starship do on Earth, which means that it's going to
require more engine power to land on Mars than it does on Earth. This
is why fuel is such a made your concern here. Assuming that everything up
until this point has gone correctly, the Starship's engines will fire up one last
time and flip the tail towards the surface at which point the fuel in the
rocket's header tanks will provide just enough delta V to bring our ship perfectly in
sync with the surface of Mars and we touch down softly. Now that's a
lot of stuff that has to go right, and there is zero margin for
error. You either score one hundred percent on the exam or you die.
So by knowing all of that, we can appreciate that landing on Mars is
going to be incredibly difficult in a massive vehicle like the Starship. It's much
easier for NASA to land smaller and lighter vehicles on Mars because the potential delta
V of your fuel is determined by the mass of the vehicle and the efficiency
of the engine. So one pound of fuel accomplishes more change in velocity for
a lighter ship than it does for a heavier ship, and there is a
limit on the amount of fuel that we can bring to Mars. Starship would
be much easier to land on Mars if it were lighter, but SpaceX needs
it to be so gigantic to accomplish the goal that Elon Musk has set out,
which is building a self sustaining city of one million people on Mars.
SpaceX is working hard on increasing the delta V of the starship. They want
to make starship be too longer with bigger fuel tanks, while also making it
lighter at the same time and adding three more Raptor vacuum engines. The third
version of the Raptor is currently in design and will probably offer higher efficiency and
therefore more delta V potential. Now there are other more long term solutions as
well. Remember Mars's outer moon Demos. The delta VI required to move from
low Earth orbit to the orbit of Demos is only around five point three kilometers
per second. That's a lot more manageable. And imagine if you could build
an outpost or a Mars gateway at the orbit of Damos. Now we have
the potential to refuel the ships so that it can make the hardest part of
the journey with more than enough delta vie to spare. This buys you a
margin of error that would increase the safety of a Mars landing by orders of
magnitude. So yes, landing a fully loaded starship on Mars is going to
be logistically insane. This is one of those situations where SpaceX won't know anything
for certain until they try. We've seen this twice now with just launching the
starship, and both times it exploded in mid air. Learning to land on
Mars is more than likely going to be a similar affair. They are much
more likely to fail before they succeed. They could fail multiple times. It's
going to require a spectacular amount of willpower to make this work, to not
give up, and probably more than a lot of people are genuinely prepared for.
And then eventually we try to do this with people on board, and
calling this ambitious seems like an incredible understatement, But over the history of humanity,
we've accomplished the impossible many times over, So what's one more