The study of Uranus and Neptune is one of the priorities of the planetary research in the XXI century. while the recent report of the Decadal Survey has placed a probe to Uranus in the third set of candidates for a future Flagship mission type, ahead of targets as attractive as Venus and Saturn.
Uranus seen by the Keck telescope (Keck).
Why is so interesting to study these planets? For two reasons. First, because we do not know in detail its internal structure. Second, because we now know that such planets could be very abundant in our galaxy. And is that Uranus and Neptune are a completely different kind of planet to the gas giants Jupiter and Saturn, which is why they are often called "ice giants."
Gas giants are mainly composed hydrogen (more than 90% by mass) and helium, plus a "small"-the size of the Earth-core rock and ice. That is, have a composition very similar to a brown dwarf or a star. It is true that gas giants are not exactly "gas." The tremendous pressures and temperatures inside the hydrogen is made in liquid and metallic. Rather, they should be called "liquid giant".
interior structure of planets in the Solar System (NASA).
In contrast, only 20% of the mass of the ice giants hydrogen. The remainder consists of oxygen, carbon, nitrogen or sulfur, forming compounds such as water, ammonia or methane. The smaller size of these planets prevent hydrogen from reaching inside the metallic phase. Instead of metallic hydrogen in the ice giants is believed that there is a mixture of supercritical fluids, especially water. Therefore, "ice giants" is not an expression fortunate. In any event, semantics aside, the structure and evolution of Uranus and Neptune are a mystery.
internal structure of Uranus and Neptune (NASA).
Classification planets according to their properties. Uranus and Neptune formed a separate group (NASA).
To study in depth, a mission to these planets should not be limited to flying as he did at the time of Voyager 2. Ideally orbit, analyze its atmosphere with an atmospheric probe similar to that used by the Galileo mission to Jupiter. Since Neptune is incredibly isolated, Uranus is a much more attractive. Mission to Neptune with Jupiter gravity assist needed and aerocapture if we want the mass of the spacecraft and the flight time is below a reasonable limit.
Uranus seen by Voyager 2 (left) and Keck (NASA).
addition, Uranus has a number of features that make it unique in the Solar System. The most important is the low internal heat up to ten times lower than that of Neptune. The unusual tilt of its axis of rotation (98 °) makes this unique planet in the turning world "lying." The axis of its magnetic field is deflected 60 ° to the rotation, allowing first-hand study of the interactions between the magnetic field and atmosphere of a giant planet. This magnetic field is also a mystery in itself same, the generated outside the planetary core. Secondary objectives would, of course, its satellite system and 13 rings.
internal heat of the planets of the Solar System (NASA).
tilt of the axis of rotation and magnetic fields of Uranus and Neptune (NASA).
The Uranian satellite system (NASA).
Atlas V 531 rocket would be unable to place the probe in a direct path. To minimize the flight time to Uranus Ship- tentatively called UOP (Uranus Orbiter and Probe) should conduct a flyby of Earth to increase its speed, and a stage use ion propulsion (SEP). Despite these measures, UOP would take 13 years (!) To reach Uranus. The SEP would be powered by solar panels, so that its effectiveness would decrease dramatically from 750 million kilometers (5 AU) from the Sun The SEP would have three NEXT ion engines based on xenon, two main and one reserve.
UOP Probe (NASA).
Stage SEP ion propulsion (NASA).
The SEP stage probe (NASA).
Features probe (NASA).
Path of the mission (NASA).
atmospheric probe of 127 kg and 76 cm in diameter would be separated 29 days before the arrival of the probe to Uranus. Would enter the atmosphere at the incredible speed of 22 km / s at an angle than -68 ยบ. Depending on the budget, the probe will resist to a depth corresponding to 1 or 5 bar pressure. The decline would last an hour. For its part, the orbiter would be located in a polar orbit around Uranus.
Atmospheric Probe (NASA).
Path entry (NASA).
Overflight of different satellites (NASA).
Once in orbit, UOP overflown twice satellites important system (Miranda, Umbriel, Ariel, Titania and Oberon) as part of its primary mission of 431 days. UOP would have a mass of 906 kg dry, employ three Stirling radioisotope generator (ASRG) and would have a high gain antenna 2.5 meters in diameter (the antenna on the Cassini is 4 meters). Her main propulsion system would use hypergolic fuels, with a budget of Delta-V of 2.5 km / s.
If UOP was passed in the coming years, something nearly impossible, would be launched in 2020 and would not arrive until 2033 (!!!). Uranus It is increasingly clear that the second wave of exploration Solar System is going to bed more than expected. More.
References:
Uranus seen by the Keck telescope (Keck).
Why is so interesting to study these planets? For two reasons. First, because we do not know in detail its internal structure. Second, because we now know that such planets could be very abundant in our galaxy. And is that Uranus and Neptune are a completely different kind of planet to the gas giants Jupiter and Saturn, which is why they are often called "ice giants."
Gas giants are mainly composed hydrogen (more than 90% by mass) and helium, plus a "small"-the size of the Earth-core rock and ice. That is, have a composition very similar to a brown dwarf or a star. It is true that gas giants are not exactly "gas." The tremendous pressures and temperatures inside the hydrogen is made in liquid and metallic. Rather, they should be called "liquid giant".
interior structure of planets in the Solar System (NASA).
In contrast, only 20% of the mass of the ice giants hydrogen. The remainder consists of oxygen, carbon, nitrogen or sulfur, forming compounds such as water, ammonia or methane. The smaller size of these planets prevent hydrogen from reaching inside the metallic phase. Instead of metallic hydrogen in the ice giants is believed that there is a mixture of supercritical fluids, especially water. Therefore, "ice giants" is not an expression fortunate. In any event, semantics aside, the structure and evolution of Uranus and Neptune are a mystery.
internal structure of Uranus and Neptune (NASA).
Classification planets according to their properties. Uranus and Neptune formed a separate group (NASA).
To study in depth, a mission to these planets should not be limited to flying as he did at the time of Voyager 2. Ideally orbit, analyze its atmosphere with an atmospheric probe similar to that used by the Galileo mission to Jupiter. Since Neptune is incredibly isolated, Uranus is a much more attractive. Mission to Neptune with Jupiter gravity assist needed and aerocapture if we want the mass of the spacecraft and the flight time is below a reasonable limit.
Uranus seen by Voyager 2 (left) and Keck (NASA).
addition, Uranus has a number of features that make it unique in the Solar System. The most important is the low internal heat up to ten times lower than that of Neptune. The unusual tilt of its axis of rotation (98 °) makes this unique planet in the turning world "lying." The axis of its magnetic field is deflected 60 ° to the rotation, allowing first-hand study of the interactions between the magnetic field and atmosphere of a giant planet. This magnetic field is also a mystery in itself same, the generated outside the planetary core. Secondary objectives would, of course, its satellite system and 13 rings.
internal heat of the planets of the Solar System (NASA).
tilt of the axis of rotation and magnetic fields of Uranus and Neptune (NASA).
The Uranian satellite system (NASA).
Atlas V 531 rocket would be unable to place the probe in a direct path. To minimize the flight time to Uranus Ship- tentatively called UOP (Uranus Orbiter and Probe) should conduct a flyby of Earth to increase its speed, and a stage use ion propulsion (SEP). Despite these measures, UOP would take 13 years (!) To reach Uranus. The SEP would be powered by solar panels, so that its effectiveness would decrease dramatically from 750 million kilometers (5 AU) from the Sun The SEP would have three NEXT ion engines based on xenon, two main and one reserve.
UOP Probe (NASA).
Stage SEP ion propulsion (NASA).
The SEP stage probe (NASA).
Features probe (NASA).
Path of the mission (NASA).
atmospheric probe of 127 kg and 76 cm in diameter would be separated 29 days before the arrival of the probe to Uranus. Would enter the atmosphere at the incredible speed of 22 km / s at an angle than -68 ยบ. Depending on the budget, the probe will resist to a depth corresponding to 1 or 5 bar pressure. The decline would last an hour. For its part, the orbiter would be located in a polar orbit around Uranus.
Atmospheric Probe (NASA).
Path entry (NASA).
Overflight of different satellites (NASA).
Once in orbit, UOP overflown twice satellites important system (Miranda, Umbriel, Ariel, Titania and Oberon) as part of its primary mission of 431 days. UOP would have a mass of 906 kg dry, employ three Stirling radioisotope generator (ASRG) and would have a high gain antenna 2.5 meters in diameter (the antenna on the Cassini is 4 meters). Her main propulsion system would use hypergolic fuels, with a budget of Delta-V of 2.5 km / s.
If UOP was passed in the coming years, something nearly impossible, would be launched in 2020 and would not arrive until 2033 (!!!). Uranus It is increasingly clear that the second wave of exploration Solar System is going to bed more than expected. More.
References:
- Decadal Study Ice Giants, William B. Hubbard (NASA).
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