12.0 The Jupiter Mission |
Jupiter is the largest (discovered) planet in the solar
system. Although more than five times as distant from the sun as
is the Earth, it is visible to the unaided eye on a clear night
due to its tremendous size. Jupiter is more than 1300 times as
large as the earth and masses about 318 times as much as earth.
Around it orbit at least 16 satellites, the four largest of which
were discovered by Galileo Galilei in 1610. Contrary to the
teaching this author received when a child, Jupiter does indeed
have rings, although they are not nearly as spectacular as those
of Saturn.
Jupiter - the giant planet
Datum Value units Source
Mass 1.900e+27 kg [3, p.289]
Equatorial radius 7.1492e+4 km "
Equatorial inclination 3.12 deg "
Equ. surface gravity 22.88 m/sec/sec "
Equ. escape velocity 59.6 km/sec "
Mean density 1.33 g/cu.cm. "
Sidereal rotation period 9.841 hours "
Mean distance from Sun 7.7833e+8 km "
Mean orbital velocity 13.06 km/sec "
Sidereal period 4332.71 Earth days "
Inclination to ecliptic 1.308 degrees "
Orbital eccentricity 0.0483 "
The US has sent five spacecraft to investigate Jupiter. They
were Pioneer 10 and 11, Voyager 1 and 2, and, finally, the current
mission, Galileo. For an outstanding report on the Jupiter
missions, the reader is referred to "Voyage to Jupiter", NASA
publication number SP-439 [96].
Table 12.0-1 Spacecraft Visits to Jupiter
Spacecraft Launch Date Arrival Date
Pioneer 10 March 3,1972 December 4,1973
Pioneer 11 April 6,1973 December 3,1974
Voyager 2 August 20,1977 July 9,1979
Voyager 1 September 5,1977 March 5,1979
Galileo October 18,1989 December 7,1995
Source: [96] "Voyage to Jupiter", p.31.
The Galileo mission is in deep trouble due to the failure of
its main antenna to open properly. But, true to form, NASA is
unwilling to ask for help. They would rather lose the whole
mission than turn to the Russians for help. The Russians have
informally offered to send a communications satellite to Jupiter
to relay data back to earth from the crippled Galileo spacecraft.
12.1 The Galilean satellites The four major satellites of Jupiter are: Io, Europa,
Ganymede, and Callisto. These are the four satellites which were
discovered by Galileo Galilei and which are now referred to as the
Galilean satellites. The Voyager spacecraft provided us with the
wonderful closeup pictures of these satellites. Analysis of the
photos and instrument measurements greatly improved our knowledge
of the Galilean satellites. Active volcanoes were discovered on Io
with fountains of "lava" rising not just kilometers but hundreds
of kilometers above the surface. The cover photo, courtesy of
NASA, is a picture of Io, perhaps the most exciting body in the
solar system (except for Earth of course).
According to William Hartmann, et al, in "Out of the Cradle",
the wide range of colors on Io are due to various forms of sulfur
and sulfur oxide which is white and falls like snow from the
plumes of the volcanoes. The colors give us a thermal map of Io.
Table 12.1-1 Sulfur Color vs Temperature
Temperature(C) Color
> 600 Black
300 Brown
125 Orange
20 Yellow
- 200 White
Source: [38] "Out of the Cradle", p.149,152.
The following data on the Galilean satellites has been
assembled from various sources as shown.
Io - innermost Galilean satellite
Datum Value units Source
Mass 8.94e+22 kg [3, p.290]
Equatorial radius 1.815e+3 km "
Orbital inclination 0.04 deg "
Equ. surface gravity (.185g) 1.81 m/sec/sec author
Equ. escape velocity 2.56 km/sec author
Mean density 3.57 g/cu.cm. [3, p.290]
Sidereal rotation period 1.7698605 Earth days [19, p.370]
Mean distance from Jupiter 4.216e+5 km [3, p.290]
Mean orbital velocity 17.3 km/sec author
Sidereal period 1.7698605 Earth days [19, p.370]
Inclination to ecliptic 1.308 degrees [3, p.289]
Orbital eccentricity 0.0 [3, p.290]
Europa
Datum Value units Source
Mass 4.80e+22 kg [3, p.290]
Equatorial radius 1.569e+3 km "
Orbital inclination 0.47 deg "
Equ. surface gravity (.133g) 1.30 m/sec/sec author
Equ. escape velocity 2.02 km/sec author
Mean density 2.97 g/cu.cm. [3, p.290]
Sidereal rotation period 3.5540942 Earth days [19, p.370]
Mean distance from Jupiter 6.709e+5 km [3, p.290]
Mean orbital velocity 13.7 km/sec author
Sidereal period 3.5540942 Earth days [19, p.370]
Inclination to ecliptic 1.308 degrees [3, p.289]
Orbital eccentricity 0.01 [3, p.290]
Ganymede
Datum Value units Source
Mass 1.48e+23 kg [3, p.290]
Equatorial radius 2.631e+3 km "
Orbital inclination 0.19 deg "
Equ. surface gravity (.146g) 1.43 m/sec/sec author
Equ. escape velocity 2.74 km/sec author
Mean density 1.94 g/cu.cm. [3, p.290]
Sidereal rotation period 7.1663872 Earth days [19, p.370]
Mean distance from Jupiter 1.070e+6 km [3, p.290]
Mean orbital velocity 10.9 km/sec author
Sidereal period 7.1663872 Earth days [19, p.370]
Inclination to ecliptic 1.308 degrees [3, p.289]
Orbital eccentricity 0.0 [3, p.290]
Callisto - outermost Galilean satellite
Datum Value units Source
Mass 1.08e+23 kg [3, p.290]
Equatorial radius 2.400e+3 km "
Orbital inclination 0.28 deg "
Equ. surface gravity (.127g) 1.25 m/sec/sec author
Equ. escape velocity 2.45 km/sec author
Mean density 1.86 g/cu.cm. [3, p.290]
Sidereal rotation period 16.753552 Earth days [19, p.370]
Mean distance from Jupiter 1.883e+6 km [3, p.290]
Mean orbital velocity 8.2 km/sec author
Sidereal period 16.753552 Earth days [19, p.370]
Inclination to ecliptic 1.308 degrees [3, p.289]
Orbital eccentricity 0.01 [3, p.290]
One of the most significant investigations made by the US
spacecraft was the characterization of the Jovian magnetosphere.
This magnetosphere is a plasma whose origin is primarily the
volcanic activity of Io which is, in turn, due to the gravita-
tional stresses on Io from Jupiter. Each Pioneer spacecraft was
subjected to in excess of 400,000 rads of radiation during their
transit of the Jovian system [3, p.37]. This is 1000 times the
dose fatal to humans. The intensity of this field drops off
rapidly with the distance from Jupiter. The field intensity is
about 20% of the peak at the orbit of Io and about 2% of peak at
the orbit of Europa. Thus, the astronauts in "2001: A Space
Odyssey", "2010", and, especially, the miners in "Outland" would
all receive fatal doses of radiation. By the orbit of Ganymede
(about 15 Jovian radii), it has dropped another two orders of
magnitude. Perhaps by the orbit of Callisto (about 26 Jovian
radii), astronauts can explore the surface without fear of fatal
exposure.
Since the vast majority of the particles which constitute this
field are charged, it is possible to use magnetic shields to
protect our astronauts from it. This concept has been addressed by
various authors over the last thirty years. One of the most recent
papers entitled "Magnetic Radiation Shielding: An Idea Whose Time
has Returned", written by Geoffrey Landis, describes a "magnetic/
electrostatic plasma shield in which an electrostatic field
shields the crew from positively charged particles while a
magnetic field confines electrons from the space plasma to provide
charge neutrality" [SM 47, p.383]. Such a shield might allow us to
visit even Io.
The remaining 12 or so satellites of Jupiter are very likely
all captured asteroids. They are all very small and most orbit at
great distances from Jupiter.
12.2 Selecting a home in the Jovian system
Large amounts of ice are believed to be present on Ganymede
and Callisto. They both have densities which are less than 2 grams
per cubic centimeter and both are estimated to consist of more
than 60% water-ice by John Lewis and Mark Lupo [3, p.172].
Pictures of Callisto show how recent impacts have exposed the
underlying ice. Evidently, the surface is covered by as little as
a few centimeters of dark dust and debris and below that lie many
kilometers of ice.
We suggest the north pole of Callisto as the tentative site
for the first Jovian base. This site would allow continuous
observation of the Jovian system from a site of comparative
safety. It would also have direct access to the ice from which LOX
and LH2 propellants would be made.
From Callisto, the planet Jupiter would appear about 4.35
degrees wide as compared to about 0.5 degrees for the moon as
viewed from earth. The amount of sunlight received at Callisto (or
Jupiter) is only about 3.7% of what we get on earth. All life
support systems must be prepared for temperatures of about -173
degrees Celsius [41, p.122].
12.3 Outline of an unmanned mission to Callisto Once again, we would send an unmanned mission to Jupiter
before sending a manned mission. This mission would be similar to
the previously described mission to Phobos; however, in this case
the spaceship would maneuver into an equatorial orbit around
Callisto instead of landing on it. From this orbit, it will be
possible to launch projectiles back toward earth to slow down the
incoming manned spaceship. If the projectiles are carefully
launched, their effect on the orbit of the spaceship will be
minimal and can be compensated for, as required, using propellant
from Callisto. If we launched projectiles every 5 minutes from an
equatorial orbit, we would expect orbital perturbations on
opposite sides of Callisto to nearly cancel each other out. Some
projectiles would be wasted because they would crash into
callisto, but so what?
The mission outline might be something like the following:
1. Maneuver into Callisto's orbit upon arrival at the Jovian
system. Callisto is moving at about 8.2 kilometers per second
around Jupiter.
2. Close on Callisto.
3. Maneuver into an equatorial orbit around Callisto.
4. Despin the spaceship.
5. Detach all landing modules. This would include propellant
production facilities, empty tanks, nuclear power units, androids,
science experiments, observation equipment, communications equip-
ment, rocket engines, spare parts, and so on.
6. Land the equipment at the north pole using propellant from
the spaceship. This operation could possibly be done in steps if
the first unit landed was the propellant production facility. Then
propellant from Callisto could be used to bring down the rest.
7. Propellant will be lifted to the spaceship to be used for
pointing the EMPL during the slowing-down of the manned spaceship.
Due to the problems of storing cryogenic propellants, it may be
necessary to lift water or ice and only convert it to LOX and LH2
at the last moment, using on board electrolysis facilities.
8. The spaceship will be spun up again before the manned ship
arrives.
12.4 Recovering helium-3 from Jupiter One of the discoveries made by Voyager 1 was that about 11% by
volume of the atmosphere of Jupiter is helium [96, p.87]. This
closely matches the percent of helium found on the sun, indicating
that Jupiter is a good sample of the primordial nebula from which
the solar system formed.
Between 1973 and 1978 some members of the British Inter-
planetary Society worked on a project called Daedalus. It was an
interstellar spacecraft which was intended to run on deuterium and
helium-3 [66, p.68]. Their intention was to "mine" the helium-3
from the atmosphere of Jupiter.
Even assuming a low concentration of helium-3, it is easily
calculated that there is more helium-3 on Jupiter than there is
water in all oceans of earth (roughly 100 times more). Although
some recent papers such as "Helium-3 Mining of Uranus" by Dani
Eder which appeared in volume 8 of "Space Manufacturing", prefer
Uranus to Jupiter, we prefer Jupiter. After all, it is much closer
and far more interesting than Uranus.
12.5 The manned spaceship to Jupiter The manned spaceship which we send to Jupiter will be the same
ship that went to Mars. This will save much construction time and
thus money as well. No doubt there will be significant refurbish-
ment of the ship before its departure for Jupiter. The most
significant modification will be the quadrupling of the nuclear
power supplies. The purpose will be to enable the EMPL to throw
projectiles twice as fast as the original EMPL - which will permit
the ship to travel twice as fast. Other changes will be made to
include the latest "low" technology available.
Recruitment of another crew may be considerably more difficult
because of the much longer anticipated travel times (6 months each
way) and the lower interest in Jupiter. Surprisingly, the total
expedition time will be less than the Mars expedition (580 days
vs. 824 days). This writer will certainly go if at all possible.
12.6 Timeline If the Mars expedition leaves in the 22nd year of the project,
then it will return in the 24th year. Modifications to the ship
will probably take a year to complete. Therefore, we might be
ready to leave for Jupiter in the 26th year. We must also wait
until the Callisto ship has successfully accomplished its mission.
By quadrupling the power of the primary EMPL and the ship's
EMPL, we can double the speed of the spaceship and thus halve the
travel time to Jupiter. The ship's speed will be boosted to nearly
40 kilometers per second - the upgraded capability of the primary
EMPL. The travel time to Jupiter will be reduced to about 6
months.
Launch windows to Jupiter occur about every 399 days. Thus,
when we arrive at Jupiter there will only be (399 - 180 =) 219
days until the return launch window. Counting the return travel
time, the total trip time will be about (399 + 180 =) 579 days.
Notice that this is 245 days LESS than the Mars trip.
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