-
2168 - SUN
- Parker Solar Probe. The mission's objectives include tracing
the flow of energy that heats and accelerates the sun's corona and solar wind,
determining the structure and dynamics of the plasma and magnetic fields at the
sources of the solar wind and explore mechanisms that accelerate and transport
energetic particles.
-
-
-
-------------------------------- 2168 - SUN
- Parker Solar Probe
-
- The Parker
Solar Probe was launched August 12, 2018. It is scheduled to reach the sun's outer
atmosphere in December. Although the
probe itself is about the size of a car, a powerful rocket is needed to escape
Earth's orbit, change direction in space and slow down as it reaches the sun.
-.
- The launch
window was chosen because the probe will rely on Venus to help it achieve an
orbit around the sun. Six weeks after
launch, the probe will encounter Venus' gravity for the first time. It will be
used to help slow the probe, like pulling on a handbrake, and orient the probe
so it's on a path to the sun.
-
- The launch
energy to reach the Sun is 55 times that required to get to Mars, and two times
that needed to get to Pluto
-
- The Earth is 93
million miles from the sun and the probe will reach to within 3.85 million
miles of the surface.
-
- The probe
will have to withstand heat and radiation never previously experienced by any
spacecraft, but the mission will also address questions that couldn't be
answered before. Understanding the sun in greater detail can also shed light on
Earth and its place in the solar system.
-
- The Parker
Solar Probe will take seven flybys of Venus that will essentially give a
gravity assist, shrinking its orbit over the course of nearly seven years. The probe will orbit within 3.9 million miles
of the sun's surface in 2024, closer to the star than Mercury. Although that
sounds far, researchers equate this to the probe sitting on the 4-yard line of
a football field and the sun being the end zone.
-
- When closest
to the sun, the 4½-inch-thick carbon-composite solar shields will have to
withstand temperatures close to 2,500 degrees Fahrenheit. However, the inside
of the spacecraft and its instruments will remain at a comfortable room
temperature. ( See Note 1)
-
- The heat
shield is 2.5 meters wide. It is made of
foam sandwiched between carbon sheets.
The whole shield is only 11.5 centimeters thick. White ceramic coating on the face is used to reflect sunlight. The hot side will reach 370 C. The cool side only 30 C.
-
- When the
Probe flies by Venus the temperature will be -260C. Twisted niobium wire is used to hold the
hundreds of screws in place during these temperature extreme changes.
-
- Dust will be
hitting the telescope lens at 380,000 miles per hour. But calculations have the lens being only 0.6%
pitted after its 7 year mission. (See
Note 2)
-
- The probe
will reach a speed of 430,000 miles per hour around the sun, setting a record
for the fastest manmade object. On Earth, this speed would enable someone to
get from Philadelphia to Washington in one second.
-
- The mission's
objectives include tracing the flow of energy that heats and accelerates the
sun's corona and solar wind, determining the structure and dynamics of the
plasma and magnetic fields at the sources of the solar wind and explore
mechanisms that accelerate and transport energetic particles.
-
- The corona is
a mystery as to how it can reach temperatures in millions of degrees , 300 times
hotter than the surface of the sun? It is
also responsible for the solar winds. The
winds are a outflow of particles accelerated by extreme temperatures to a million
miles per hour.
-
- On Earth these
solar winds can create aurora that cause electrical blackouts and disrupt satellite
communications.
-
- Four suites
of instruments will gather the data needed to answer key questions about the
sun. FIELDS will measure electric and magnetic waves around the probe, WISPR
will take images, SWEAP will count charged particles and measure their
properties, and ISOIS will measure the particles across a wide spectrum.
-
- The Alfvén
point is the distance from the Sun beyond which the charged particles that make
up the solar wind are no longer in contact with the surface of the sun. If the Parker Solar Probe can reach below
the Alfvén point, then we can say the spacecraft has entered the solar atmosphere
and touched the Sun.
-
- The mission
is scheduled to end in June 2025. The first data download from the Parker Solar
Probe is expected next month, December,
2018, after the probe reaches its first close approach of the sun in November. It is scheduled to loop around the sun 20 times
in 7 years getting as close as 3,900,000 miles.
-
- The Parker Solar
Probe will solve some of our star's biggest mysteries. Stay tuned, there is much more to learn.
-
- Other Reviews
available:
-
- 2165 - Why
is the sun so hot?
-
- 1832 - How
does the sun get its energy? How does it
compare to other stars? How long will it
live? This Review list 6 other reviews
about the sun.
-
- Note 1: How much heat must the heat shield dissipate
to keep the instruments cool? When
Parker enters space the sun's radiation is 1378 watts/ merer^2. The shield's reflectivity is 60%.
-
--------------------
1378 watts/ meter^2 = 2 * 5.67 *10^-8 * ( 1 - 0.60 )
* Temperature^4
-
----------------------
Temperature^4 = 3.1 * 10^10
-
----------------------
Temperature = 420 Kelvin
-
- When Parker
is closest to the sun the radiation temperature will be 250 times greater.
-
----------------------
1378 * 250 = 2 * 5.67 *10^-8 * ( 1 - 0.60 )
* Temperature^4
-
----------------------
Temperature^4 = 37.6 * 10^12
-
----------------------
Temperature = 1,700
Kelvin
-
- When closest
to the sun how much heat energy must Parker be radiating away?
-
----------------------- Heat energy =
1378 * 250 = 344,500 watts
/ meter^2
-
----------------------- The area of the heat shield is 7.8 meters^2
-
----------------------- Power
= = 344,500 watts
/ meter^2 * 7.8
meters^2 = 2,700,000 watts
-
- Note 2: The
space craft is travelling 380,000 miles per hour. It will be encountering dust
grains 1 micron in diameter. The density
of the dust grains when nearest t the sun is 0.005 grains / meter^2. the telescope lens is 140 centimeters^
2. In the 10 days spent nearest to the
sun , at perihelion, how many impacts will hit the lens?
-
----------------------- .005 grains / meter^2 *
0.014 meters^2 = 0.00007
impacts per second
-
----------------------
1 / 0.00007
seconds per impact = 14,286 seconds / 3600
=
3.97 hours
-.
----------------------- 10 days
* 24 hours / day / 4
hours per impact = 60 impacts
-
- November 22, 2018. An Index of recent Reviews is available.
----------------------------------------------------------------------------------------
----- Comments appreciated and Pass it on to
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--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email feedback, corrections, request for
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--- to:
------
jamesdetrick@comcast.net
------ “Jim Detrick” -----------
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--------------------- Thursday, November 22, 2018 -------------------------
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