Have you ever looked up at the Sun and wondered if
you could go there? If you had a very powerful rocket
ship, how would you get there? How could you avoid
being burned up by the intense heat on the way? What
would you want to study when you got there? Scientists
working for NASA have been asking these same
questions. They are now working on a NASA mission
called the Solar Probe Project. The Solar Probe will be
a unique spaceship, designed to fly quite close to the
Sun (within 1.5 Sun diameters). The Solar Probe will
actually fly through the Sun’s outer layer, the corona.
Scientists hope that data sent back from instruments
carried on the Solar Probe will give them a better
understanding of the Sun and especially its solar wind
which can affect the Earth. NASA scientists had to
think about a number of problems in designing the
Solar Probe mission.
Getting Away from Earth
The first problem to be solved is getting away from Earth. The Earth's
gravity makes it difficult to leave the Earth's surface. For example, the Space Shuttle must
achieve a speed of 17,000 miles (27,358 kilometers) per
hour to go into orbit around the Earth. This requires a
tremendous amount of power. For example, the Space
Shuttle's two solid rocket motors are more powerful than
35 jumbo jets at takeoff. The energy released by the three
Space Shuttle main engines is equivalent to the output of
23 Hoover Dams. Together, the Space Shuttle's three
main engines and two solid rocket boosters generate
some 7.3 million pounds (3.3 million kilograms) of thrust
at liftoff. The speed of the gases exiting the nozzle is
more than 6,000 miles (9,656 kilometers) per hour, about
five times the speed of sound or three times the speed of a
high-powered rifle bullet.
Even when you are in orbit around the Earth it is still
very hard to break free of the Earth's gravity. To get to the
Sun you must escape the Earth's gravity and first go into
orbit around the Sun. The pilot of the rocket ship headed
to the Sun would have to fire the ship's rockets until the
ship has escaped the Earth's gravity. At this point the
rocket ship is like a "planet" in orbit around the Sun and is too far from the Earth to feel a significant pull from
the Earth's gravity. Then the pilot would have to fire
retro-rockets to slow the ship down in its motion
around the Sun. The Sun's gravity is always pulling on
the space ship. However, the motion of the ship around
the Sun keeps the ship from falling into the Sun. The
retro-rockets reduce the ship's speed around the Sun
and allow the Sun's gravity to pull the ship towards the
Sun.
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