StyroCupMan writes "NASA has announced that it will launch a satellite to map our solar system's boundary. It will also study the particles and radiation that pose a health and safety hazard to humans. Time to invest in that shiny new spacesuit."
Re:Historically speaking...
by
StyroCupMan
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· Score: 2, Informative
That is a very good question. There a couple reasons I can think of as to why exploration is primarily in the same plane as the planets.
First, you can get there faster by using the gravity of intervening planets.
Second, you can do some interesting science (take pictures, etc) on the planets and other objects you pass by.
-- If I may say so, life is a game, and there's so much to do and so few turns. -Reiner Knizia
Re:Historically speaking...
by
CrimsonAvenger
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· Score: 4, Informative
Any scientifically sound reason why this is a bad idea?
DeltaV required to head out perpendicular to the plane of the ecliptic is quite a bit higher than to go out along the ecliptic.
Achieving Solar escape speed from LEO in the plane of the ecliptic is ~9Km/s.
Perpendicular to the ecliptic, deltaV required is ~26Km/s.
And it's tough to use planetary slingshots when you're going out perpendicular to the ecliptic.
--
"I do not agree with what you say, but I will defend to the death your right to say it"
Re:Historically speaking...
by
escher
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· Score: 2, Informative
i never understood this. why do you have to go 9km/s to escape the Earth's gravity?
if you can move upwards at an inch a day, eventually you would leave gravitational pull, woudln't you? why is the 9km/s significant?
The 9km/s is significant if you only have the launch velocity to work with (like throwing a rock).
The inch per day example only works if you're constantly accellerating (say, via a rocket).
Re:Long-term science
by
jnik
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· Score: 4, Informative
Nobody said the probe is actually crossing the termination shock. It's observing ENA's generated at the termination shock.
Uber-brief introduction to energetic neutral atoms: Ions (charged particles) are susceptible to magnetic and electric forces. As a result, they can be boosted to very high energies in certain situations, but also usually can't travel very far before being modified in some way by electromagnetic forces. If, however, an ion interacts with a neutral (charge exchange), it can "steal" one or more electrons from the neutral without substantially changing the energies of either, leaving a nonenergetic ion and an energetic neutral, which then leaves the vicinity as it is no longer subject to EM forces. We can observe these ENA's and infer properties of the acceleration region.
Re:Why?
by
Anonymous Coward
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· Score: 2, Informative
If you read the article this is part of the Small Explorer Mission so this probe has a very limited set of instruments and a narrow focus of inquiry, so it is relatively inexpensive. Note the estimated price, $124 million, a few orders of magnitude cheaper than the Gaileo probe, and you would want a probe with that range of capabilities to go to Pluto.
I do agree that a mission to Pluto would be great, especially before it progresses to the part of its orbit where its atmosphere freezes. However, this is like complaining you can't afford to buy a car because your significant other bought a skateboard.
9 km/s is the static speed you must be moving if you stop applying thrust. In other words, when you stop applying thrust, you'd better be going 9 km/s or faster or the Earth will eventually pull you back.
Your example of moving up 1 inch per day (do you work for NASA, mixing measurement systems like that, now really!) implies that you continue to accellerate enough to maintain your position (i.e. you do not allow yourself to fall back that one inch) until you move up further.
-- The NSA: The only part of the US government that actually listens.
Re:Historically speaking...
by
mopomi
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· Score: 4, Informative
Basically, an object needs a specific amount of energy to escape the gravitational well of some other object. Remember that kinetic energy is KE = 1/2 mv^2,
where m is mass and v is velocity.
Gravitational binding energy is the energy required to escape a gravity well (basically):
GE = GmM/R,
where G is the gravitational constant, m is the mass of the escaping object, M is the mass of the planet, and R is the planet's radius.
Setting KE=GE and solving for velocity gives you the escape velocity (the very minimum INITIAL velocity required to escape with NO ADDITIONAL ACCELERATION). Notice that the object's mass cancels, so you're left with a constant value for the planet's escape velocity (of course, you need more energy to accelerate a more massive object to the same velocity). Earth's escape velocity is actually 11.1 km/s. Not sure where that 9 km/s comes from.
Re:Leaving the ecliptical plane
by
CrimsonAvenger
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· Score: 2, Informative
Arhtur C CLarke was a great man, he really was.
But he was wrong here. If you're in a polar orbit to start with, you'll need a bit more deltaV than I described, since I assumed the ideal departure orbit (one where the burn was entirely in the direction of travel).
The big difficulty with going into a Solar polar orbit is that you have to cancel Earth's orbital speed as part of the orbital insertion burn. And Earth's orbital speed is ~30Km/s, more in northern-hemisphere winter, less in northern-hemisphere summer.
That ion drive that was tested this past year could, conceivably, be used to come up with the deltaV required for a Solar-polar orbit that was also a Solar-escape orbit. But no chemical rocket we can make can pull it off.
--
"I do not agree with what you say, but I will defend to the death your right to say it"
Re:Historically speaking...
by
Anonymous Coward
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· Score: 2, Informative
Two reasons why these probes have been sent out along the orbital plane (at least initially):
1) Much of the speed is generated by the slingshot effect from a planet. The Voyagers used this effect at each planet to gain the necessary speed to reach the next- they did not attain enough speed to escape the solar system until after the third or fourth planet.
2) These probes are EXPENSIVE. If we want to launch one out of the solar system, why not along the direction where we can make planetary observations along the way? The Pioneer and Voyager probes were primarily meant as planetary probes; observations of the edge of the solar system were only a secondary intent.
BUT.... There is no reason why the last planetary slingshot can't be used to throw the probes off into a non-solar system plane- this is exactly what they have done. The Voyager probes are no longer in the plane of the planetary orbit; I believe both of them are now travelling in a direction more than 30 degrees from this plane.
Re:Long-term science
by
Anonymous Coward
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· Score: 1, Informative
It doesn't say anything about an elliptical orbit around the SUN. The exact wording is "IBEX will make these observations from a highly elliptical orbit that takes it beyond the interference of the Earth's magnetosphere." I'd take that to mean an orbit around the Earth in such a away as to avoid the Earth's magnetosphere. It will image the termination shock, not go there. You can also infer this from the statement "The Small Explorer program (SMEX) consists of rapid, small, and focused science exploration missions." that for it to be a rapid mission, it won't be going to Pluto which would put a minimum of 10 years on its journey.
Re:Historically speaking...
by
Graymalkin
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· Score: 2, Informative
I don't think you really understand the need for gravitational assists. Without such assists a probe using current launch technology would not be able to make it anywhere close to the edge of the solar system. We can't just fire these things off in a roughly straight line. They're launched in what are essentially variations of a Hohmanntransfer orbit. Instead of moving from one circular orbit to another though, you're transfering from a circular orbit to a hyperbolic one. The same concept applies, energy needs to be added to increase the altitude of the orbit which is where the gravity assist comes in.
Shooting a probe off perpendicular to the mean plane of the solar system would be shooting yourself in the foot. You'd be entirely missing out on the enormous gravitation boost Jupiter and/or Saturn offer. You would need überamounts of extraordinarily energetic fuel to make the trip without using the gas giants. Even then the rocket (as mentioned) would need to be about 98% fuel. We can at best build ones that are 90% fuel.
There's also a shitload of vaccuum in the planetary plane just as there is perpendicular to the plane. There would really be little use in avoiding the planetary plane as you suggest. Besides the boost the probe would get from the gas giant(s) it could be put on a course where some secondary science could be conducted on the way to the edge of the solar system. You wouldn't need extra equipment to study doppler shifts as the probe entered say Jupiter's gravity well during an assist or watch it's radio signal as it was occulted by the planet for frequency varations to infer magnetic fields or ionized particles in the atmosphere.
-- I'm a loner Dottie, a Rebel.
Wait a minite guys..
by
adeyadey
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· Score: 2, Informative
IBEX will make these observations from a highly elliptical orbit that takes it beyond the interference of the Earth's magnetosphere.
Guys, I know the article says very little, but from what I can see this probe orbits the EARTH, not the sun, in an elliptical orbit, with sensors to examine (amongst other things) particles from the heliopause. Makes sense - $134 million would not be nearly enough money for a deep-space mission - the Plutonium nuclear batteries (RTG) alone would cost most of that. Deep space needs expensive support from Deep Space Network, and advanced/expensive comms. To get to Earth-escape you need an expensive big rocket too, unless you use ion. This probe will probably run off solar.
To get an idea of what even a "cheap" mission to Pluto & Heliopause is going to cost see the New Horzons page http://pluto.jhuapl.edu/ - this will be around $600 million. Apparantly they are in a real race against time to make the Jan 2006 launch window - there was a hitch at Los Alamos where they make the RTGs - Plutonium 238 is currently very hard to get hold of & they might not have enough by launch date. Shame they are not funding a "cheap" copycat 2007-8 NH-2 mission which could swing by Jupiter,Uranus & a few more KBOs including a nice double system..
By the way I do think it could be done cheaper still - when are we going to have a true deep space ion craft? (solar+RTG)
Slashdot Mirror
That is a very good question. There a couple reasons I can think of as to why exploration is primarily in the same plane as the planets.
First, you can get there faster by using the gravity of intervening planets.
Second, you can do some interesting science (take pictures, etc) on the planets and other objects you pass by.
If I may say so, life is a game, and there's so much to do and so few turns.
-Reiner Knizia
DeltaV required to head out perpendicular to the plane of the ecliptic is quite a bit higher than to go out along the ecliptic.
Achieving Solar escape speed from LEO in the plane of the ecliptic is ~9Km/s.
Perpendicular to the ecliptic, deltaV required is ~26Km/s.
And it's tough to use planetary slingshots when you're going out perpendicular to the ecliptic.
"I do not agree with what you say, but I will defend to the death your right to say it"
i never understood this. why do you have to go 9km/s to escape the Earth's gravity?
if you can move upwards at an inch a day, eventually you would leave gravitational pull, woudln't you? why is the 9km/s significant?
The 9km/s is significant if you only have the launch velocity to work with (like throwing a rock).
The inch per day example only works if you're constantly accellerating (say, via a rocket).
Uber-brief introduction to energetic neutral atoms: Ions (charged particles) are susceptible to magnetic and electric forces. As a result, they can be boosted to very high energies in certain situations, but also usually can't travel very far before being modified in some way by electromagnetic forces. If, however, an ion interacts with a neutral (charge exchange), it can "steal" one or more electrons from the neutral without substantially changing the energies of either, leaving a nonenergetic ion and an energetic neutral, which then leaves the vicinity as it is no longer subject to EM forces. We can observe these ENA's and infer properties of the acceleration region.
If you read the article this is part of the Small Explorer Mission so this probe has a very limited set of instruments and a narrow focus of inquiry, so it is relatively inexpensive. Note the estimated price, $124 million, a few orders of magnitude cheaper than the Gaileo probe, and you would want a probe with that range of capabilities to go to Pluto.
I do agree that a mission to Pluto would be great, especially before it progresses to the part of its orbit where its atmosphere freezes. However, this is like complaining you can't afford to buy a car because your significant other bought a skateboard.
Your example of moving up 1 inch per day (do you work for NASA, mixing measurement systems like that, now really!) implies that you continue to accellerate enough to maintain your position (i.e. you do not allow yourself to fall back that one inch) until you move up further.
The NSA: The only part of the US government that actually listens.
Basically, an object needs a specific amount of energy to escape the gravitational well of some other object. Remember that kinetic energy is
KE = 1/2 mv^2,
where m is mass and v is velocity.
Gravitational binding energy is the energy required to escape a gravity well (basically):
GE = GmM/R,
where G is the gravitational constant, m is the mass of the escaping object, M is the mass of the planet, and R is the planet's radius.
Setting KE=GE and solving for velocity gives you the escape velocity (the very minimum INITIAL velocity required to escape with NO ADDITIONAL ACCELERATION). Notice that the object's mass cancels, so you're left with a constant value for the planet's escape velocity (of course, you need more energy to accelerate a more massive object to the same velocity). Earth's escape velocity is actually 11.1 km/s. Not sure where that 9 km/s comes from.
But he was wrong here. If you're in a polar orbit to start with, you'll need a bit more deltaV than I described, since I assumed the ideal departure orbit (one where the burn was entirely in the direction of travel).
The big difficulty with going into a Solar polar orbit is that you have to cancel Earth's orbital speed as part of the orbital insertion burn. And Earth's orbital speed is ~30Km/s, more in northern-hemisphere winter, less in northern-hemisphere summer.
That ion drive that was tested this past year could, conceivably, be used to come up with the deltaV required for a Solar-polar orbit that was also a Solar-escape orbit. But no chemical rocket we can make can pull it off.
"I do not agree with what you say, but I will defend to the death your right to say it"
Two reasons why these probes have been sent out along the orbital plane (at least initially):
1) Much of the speed is generated by the slingshot effect from a planet. The Voyagers used this effect at each planet to gain the necessary speed to reach the next- they did not attain enough speed to escape the solar system until after the third or fourth planet.
2) These probes are EXPENSIVE. If we want to launch one out of the solar system, why not along the direction where we can make planetary observations along the way? The Pioneer and Voyager probes were primarily meant as planetary probes; observations of the edge of the solar system were only a secondary intent.
BUT....
There is no reason why the last planetary slingshot can't be used to throw the probes off into a non-solar system plane- this is exactly what they have done. The Voyager probes are no longer in the plane of the planetary orbit; I believe both of them are now travelling in a direction more than 30 degrees from this plane.
It doesn't say anything about an elliptical orbit around the SUN. The exact wording is "IBEX will make these observations from a highly elliptical orbit that takes it beyond the interference of the Earth's magnetosphere." I'd take that to mean an orbit around the Earth in such a away as to avoid the Earth's magnetosphere. It will image the termination shock, not go there. You can also infer this from the statement "The Small Explorer program (SMEX) consists of rapid, small, and focused science exploration missions." that for it to be a rapid mission, it won't be going to Pluto which would put a minimum of 10 years on its journey.
Startrek.com summary
I don't think you really understand the need for gravitational assists. Without such assists a probe using current launch technology would not be able to make it anywhere close to the edge of the solar system. We can't just fire these things off in a roughly straight line. They're launched in what are essentially variations of a Hohmann transfer orbit. Instead of moving from one circular orbit to another though, you're transfering from a circular orbit to a hyperbolic one. The same concept applies, energy needs to be added to increase the altitude of the orbit which is where the gravity assist comes in.
Shooting a probe off perpendicular to the mean plane of the solar system would be shooting yourself in the foot. You'd be entirely missing out on the enormous gravitation boost Jupiter and/or Saturn offer. You would need überamounts of extraordinarily energetic fuel to make the trip without using the gas giants. Even then the rocket (as mentioned) would need to be about 98% fuel. We can at best build ones that are 90% fuel.
There's also a shitload of vaccuum in the planetary plane just as there is perpendicular to the plane. There would really be little use in avoiding the planetary plane as you suggest. Besides the boost the probe would get from the gas giant(s) it could be put on a course where some secondary science could be conducted on the way to the edge of the solar system. You wouldn't need extra equipment to study doppler shifts as the probe entered say Jupiter's gravity well during an assist or watch it's radio signal as it was occulted by the planet for frequency varations to infer magnetic fields or ionized particles in the atmosphere.
I'm a loner Dottie, a Rebel.
IBEX will make these observations from a highly elliptical orbit that takes it beyond the interference of the Earth's magnetosphere.
Guys, I know the article says very little, but from what I can see this probe orbits the EARTH, not the sun, in an elliptical orbit, with sensors to examine (amongst other things) particles from the heliopause. Makes sense - $134 million would not be nearly enough money for a deep-space mission - the Plutonium nuclear batteries (RTG) alone would cost most of that. Deep space needs expensive support from Deep Space Network, and advanced/expensive comms. To get to Earth-escape you need an expensive big rocket too, unless you use ion. This probe will probably run off solar.
To get an idea of what even a "cheap" mission to Pluto & Heliopause is going to cost see the New Horzons page
http://pluto.jhuapl.edu/ - this will be around $600 million. Apparantly they are in a real race against time to make the Jan 2006 launch window - there was a hitch at Los Alamos where they make the RTGs - Plutonium 238 is currently very hard to get hold of & they might not have enough by launch date. Shame they are not funding a "cheap" copycat 2007-8 NH-2 mission which could swing by Jupiter,Uranus & a few more KBOs including a nice double system..
By the way I do think it could be done cheaper still - when are we going to have a true deep space ion craft? (solar+RTG)
"You lied to me! There is a Swansea!"