If you're hoping to be one of those first
human interplanetary explorers, you might
want to know: how long does it take to get
to Mars?
The journey from Earth to Mars takes about
300 days.
Every two years Mars is at its closest point,
only 55 million km from Earth, and it's the
ideal time to send a spacecraft.
Travel time depends on the positions of the
planets and how much fuel you're willing to
burn.
When you're trying to get to Mars, just like
in a car, spending more fuel means a shorter
travel time.
The first spacecraft to make this journey
was NASA's Mariner 4, launched on November
28, 1964 and arrived 228 days later.
This was a flyby mission, where the spacecraft
took only 21 grainy photographs of the Martian
surface.
Since that first flyby, there have been a
total of 21 successful missions sent to the
red planet.
This doesn't include a few partial successes
and many many failures.
So, why does it take so long?
If Mars is only 55 million km away and if
a spacecraft can travel at 20,000 km/hour,
you would expect the journey to take only
115 days, but it actually takes much longer.
You can't just point your spacecraft at Mars
and start firing your rockets.
Because by the time you got there, Mars would
have moved.
Instead, spacecraft need to be pointed at
where Mars is going to be.
Then you would follow a trajectory which gets
you to your destination using the least amount
of fuel possible.
This is trajectory is called a Hohmann Orbit,
and was first proposed by Walter Hohmann in
1925.
Here's how it works.
You boost the orbit of your spacecraft so
that it's following a larger orbit around
the Sun than the Earth.
Eventually that orbit will intersect the orbit
of Mars - the exact moment Mars is there too.
If you've got less fuel, you just take longer
to raise your orbit, which the increases your
travel time.
Are you impatient to get to Mars and want
to decrease your flight time?
Here are some drawing board proposals to shorten
the travel times:
We could use Nuclear rockets.
These work by heating up a propellent to incredible
temperatures and then blasting it out a rocket
nozzle at high velocity to create thrust.
This gives you higher thrust velocity with
less fuel and could decrease travel time down
to 7 months.
Or a there's a Variable Specific Impulse Magnetoplasma
Rocket (or VASIMR) which uses radio waves
to ionize a propellant which would then be
accelerated out the back of the spacecraft
using a powerful magnetic field.
A VASIMR engine could decrease Mars travel
time down to 5 months.
The most exotic solution is antimatter.
When atoms of matter meet antimatter, they
transform into pure energy.
Just milligrams of antimatter would provide
enough fuel to propel a human mission to Mars
in only 45 days.
But there are so many unknowns for creating
and storing that much antimatter, that it'll
be decades before it's ready for a real mission.
There are plenty more missions planned, and
engineers will be testing out these new technologies,
and coming up with even more ideas.
So maybe one day, getting to Mars will be
as quick and easy as going on a cruise, or
taking a road trip.
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