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PaulCsouls wrote:
Rover, balloon or whatever, they should do it quick. The real key to any Titan mission is a plutonium powered schoolbus in the neighborhood to relay the data home. Once Cassini is gone, the project increases a whole order of magnitude. And with a seven year travel time, they don't have a whole lot of time to decide. When is the next launch window for a direct-ascent Jupiter-assist mission to Saturn? The Voyagers made it to Saturn in 18 months after launch from Earth, using that method; granted, the function of spacecraft size and launch vehicle size made that possible. If they go soon enough to utilize Cassini as the orbiter, that would reduce the size of the spacecraft needed, perhaps making the direct-ascent mission possible. -- Scott M. Kozel Highway and Transportation History Websites Virginia/Maryland/Washington, D.C. http://www.roadstothefuture.com Philadelphia and Delaware Valley http://www.pennways.com |
#12
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On Mon, 24 Jan 2005 21:25:03 GMT, "David Nakamoto"
wrote: Comparing Mars to Titan is like comparing Bermuda during the summer with Antarctica during its winter. It might be possible to design a balloon to use solar heating to inflate and deflate itself on Mars, but Titan it a lot farther away, the atmosphere is thicker and therefore acts like a thermal blanket, and the temperatures a lot colder. As an electronics and systems engineer, I don't see the problems of a balloon to be any less in number, or any less daunting, than a rover. We simply don't know, and cannot really test for, the properties of a balloon in a Titan environment. I also see the same problems with a rover, but at least with a rover you can see, stop, and consider your next move at a leisurely pace, where a balloon is going to keep going right into that hillside. So at this time, I don't see that a balloon is any better from an engineering development standpoint and uncertainties as to whether it will work standpoint over a rover. But at least the rover won't be moving uncontrollably as you try and figure out how to avoid that hill in front of you. Hmmm, how about a compromise. :-) Like maybe a tumbleweed rover? http://robotics.jpl.nasa.gov/~behar/southpoletw.htm Would certainly be useful to get across Titan rivers or seas (as long as it doesn't stick to the hydrocarbon/methane sludge). I don't see a typical MER rover being able to do that. If we land a typical rover in the wrong place, it could quickly find itself corraled by river channels or ponds. Even worse, what if there's an upwelling of liquid methane or slushy water from a cryovolcanic vent near where the rover is? Not as safe a place as Mars, but a tumbleweed may prove more durable. Of course the tumbleweek could get lodged in a crevice. Hmmm. I almost laugh just trying to picture this big 20 foot ball bouncing across the orange Titan landscape. Mind you, I had the same impressions of Pathfinder's Mars landing but three successful 'bounce' landings later I'm convinced. |
#13
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How about this fat wheeled rover. http://www.space.com/scienceastronom...an_001020.html On Tue, 25 Jan 2005 06:21:08 GMT, Drew wrote: On Mon, 24 Jan 2005 21:25:03 GMT, "David Nakamoto" wrote: Comparing Mars to Titan is like comparing Bermuda during the summer with Antarctica during its winter. It might be possible to design a balloon to use solar heating to inflate and deflate itself on Mars, but Titan it a lot farther away, the atmosphere is thicker and therefore acts like a thermal blanket, and the temperatures a lot colder. As an electronics and systems engineer, I don't see the problems of a balloon to be any less in number, or any less daunting, than a rover. We simply don't know, and cannot really test for, the properties of a balloon in a Titan environment. I also see the same problems with a rover, but at least with a rover you can see, stop, and consider your next move at a leisurely pace, where a balloon is going to keep going right into that hillside. So at this time, I don't see that a balloon is any better from an engineering development standpoint and uncertainties as to whether it will work standpoint over a rover. But at least the rover won't be moving uncontrollably as you try and figure out how to avoid that hill in front of you. Hmmm, how about a compromise. :-) Like maybe a tumbleweed rover? http://robotics.jpl.nasa.gov/~behar/southpoletw.htm Would certainly be useful to get across Titan rivers or seas (as long as it doesn't stick to the hydrocarbon/methane sludge). I don't see a typical MER rover being able to do that. If we land a typical rover in the wrong place, it could quickly find itself corraled by river channels or ponds. Even worse, what if there's an upwelling of liquid methane or slushy water from a cryovolcanic vent near where the rover is? Not as safe a place as Mars, but a tumbleweed may prove more durable. Of course the tumbleweek could get lodged in a crevice. Hmmm. I almost laugh just trying to picture this big 20 foot ball bouncing across the orange Titan landscape. Mind you, I had the same impressions of Pathfinder's Mars landing but three successful 'bounce' landings later I'm convinced. |
#14
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According to this thread, a jupiter assist saturn launch window occurs once every twenty years. The next is 2020. http://uplink.space.com/showflat.php...=&fpart=1&vc=1 On Mon, 24 Jan 2005 23:04:53 -0500, "Scott M. Kozel" wrote: PaulCsouls wrote: Rover, balloon or whatever, they should do it quick. The real key to any Titan mission is a plutonium powered schoolbus in the neighborhood to relay the data home. Once Cassini is gone, the project increases a whole order of magnitude. And with a seven year travel time, they don't have a whole lot of time to decide. When is the next launch window for a direct-ascent Jupiter-assist mission to Saturn? The Voyagers made it to Saturn in 18 months after launch from Earth, using that method; granted, the function of spacecraft size and launch vehicle size made that possible. If they go soon enough to utilize Cassini as the orbiter, that would reduce the size of the spacecraft needed, perhaps making the direct-ascent mission possible. |
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I always liked this idea, partially because it precludes the need to figure out
how to make four to six wheels to work robotically, and partially because appeals to my aesthetic sensibilities. I think the solution to the crevice thing is to make sure you don't get near one. Sometimes the engineering solution . . . isn't, but a procedural or operational one instead. The major problem is for the instruments, especially imaging or remote sensing ones that have to look past the ball. And I do agree that the major funding generator for space missions is the promise of images being received back. Making the covering transparent isn't going to work on Mars or Titan, because something is going to cover the exterior with time, and interfere with the view. And don't say you can just maneuver to get a clear view. Imagine photographic out of a car with windows only five-inches wide, and only six such windows places evenly around the car - one in front and back, two on each side, and you have to precisely aim one window at an object in order to photograph it. And you're over rocky terrain. The idea, in it's current state, is a good one for non-imaging instruments, but I don't think it could be made to work for imaging instruments, where a clear view is necessary for most of the science you would want to do. Actually, I was thinking of a squirrel-cage like ball, with an instrument package inside, like (oh! I K N O W I'm going to get laughs now. sigh) those hamster balls that allows the animal to rove the house without actually making contact with any of it, except that the ball not solid, but built like a squirrel cage. OK, now that the laughter has died down . . . At least this design can allow some chance to use imaging instruments, although how you're going to maneuver to pick a clear spot to image through, and how you control such a device (gyros for orientation and stability?) are issues. Movable covers over the instruments will protect the optics until they're ready to be used. -- Sincerely, --- Dave ---------------------------------------------------------------------- It don't mean a thing unless it has that certain "je ne sais quoi" Duke Ellington ---------------------------------------------------------------------- "Drew" wrote in message ... On Mon, 24 Jan 2005 21:25:03 GMT, "David Nakamoto" wrote: Hmmm, how about a compromise. :-) Like maybe a tumbleweed rover? http://robotics.jpl.nasa.gov/~behar/southpoletw.htm Would certainly be useful to get across Titan rivers or seas (as long as it doesn't stick to the hydrocarbon/methane sludge). I don't see a typical MER rover being able to do that. If we land a typical rover in the wrong place, it could quickly find itself corraled by river channels or ponds. Even worse, what if there's an upwelling of liquid methane or slushy water from a cryovolcanic vent near where the rover is? Not as safe a place as Mars, but a tumbleweed may prove more durable. Of course the tumbleweek could get lodged in a crevice. Hmmm. I almost laugh just trying to picture this big 20 foot ball bouncing across the orange Titan landscape. Mind you, I had the same impressions of Pathfinder's Mars landing but three successful 'bounce' landings later I'm convinced. |
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"Scott M. Kozel" wrote:
PaulCsouls wrote: Rover, balloon or whatever, they should do it quick. The real key to any Titan mission is a plutonium powered schoolbus in the neighborhood to relay the data home. Once Cassini is gone, the project increases a whole order of magnitude. And with a seven year travel time, they don't have a whole lot of time to decide. When is the next launch window for a direct-ascent Jupiter-assist mission to Saturn? The Voyagers made it to Saturn in 18 months after launch from Earth, using that method; granted, the function of spacecraft size and launch vehicle size made that possible. If they go soon enough to utilize Cassini as the orbiter, that would reduce the size of the spacecraft needed, perhaps making the direct-ascent mission possible. Correction: My statement about the 18-month Voyager trip is the time from Earth to Jupiter on Voyager 1. Voyager 1 --------- Launched - September 5, 1977 Jupiter - March 5, 1979 Saturn - November 12, 1980 Voyager 2 -------- Launched - August 20, 1977 Jupiter - August 7, 1979 Saturn - August 26, 1981 Uranus - January 24, 1986 Neptune - August 8, 1989 The closest approach dates are listed for each planet. Earth to Jupiter travel time was 18 months for Voyager 1, and was 24 months for Voyager 2. Earth to Saturn travel time was 38 months for Voyager 1, and was 48 months for Voyager 2. That is still a heck of a lot faster than the "loop-de-loop" trajectories for Galileo, 6 years and 2 months to get to Jupiter, and for Cassini, 6 years and 9 months to get to Saturn. -- Scott M. Kozel Highway and Transportation History Websites Virginia/Maryland/Washington, D.C. http://www.roadstothefuture.com Philadelphia and Delaware Valley http://www.pennways.com |
#17
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"Scott M. Kozel" wrote in message
... "Scott M. Kozel" wrote: PaulCsouls wrote: Rover, balloon or whatever, they should do it quick. The real key to any Titan mission is a plutonium powered schoolbus in the neighborhood to relay the data home. Once Cassini is gone, the project increases a whole order of magnitude. And with a seven year travel time, they don't have a whole lot of time to decide. When is the next launch window for a direct-ascent Jupiter-assist mission to Saturn? The Voyagers made it to Saturn in 18 months after launch from Earth, using that method; granted, the function of spacecraft size and launch vehicle size made that possible. If they go soon enough to utilize Cassini as the orbiter, that would reduce the size of the spacecraft needed, perhaps making the direct-ascent mission possible. Correction: My statement about the 18-month Voyager trip is the time from Earth to Jupiter on Voyager 1. Voyager 1 --------- Launched - September 5, 1977 Jupiter - March 5, 1979 Saturn - November 12, 1980 Voyager 2 -------- Launched - August 20, 1977 Jupiter - August 7, 1979 Saturn - August 26, 1981 Uranus - January 24, 1986 Neptune - August 8, 1989 The closest approach dates are listed for each planet. Earth to Jupiter travel time was 18 months for Voyager 1, and was 24 months for Voyager 2. Earth to Saturn travel time was 38 months for Voyager 1, and was 48 months for Voyager 2. That is still a heck of a lot faster than the "loop-de-loop" trajectories for Galileo, 6 years and 2 months to get to Jupiter, and for Cassini, 6 years and 9 months to get to Saturn. You're forgetting one important thing, the trajectory. For both Voyagers, they took what amounted to the most direct route to Jupiter. For Galileo and Cassini, they took the least direct route, ping-ponging around the inner Solar System for a while before heading out to Jupiter. This added to the travel time. -- Sincerely, --- Dave ---------------------------------------------------------------------- It don't mean a thing unless it has that certain "je ne sais quoi" Duke Ellington ---------------------------------------------------------------------- |
#18
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"David Nakamoto" wrote:
"Scott M. Kozel" wrote: Earth to Jupiter travel time was 18 months for Voyager 1, and was 24 months for Voyager 2. Earth to Saturn travel time was 38 months for Voyager 1, and was 48 months for Voyager 2. That is still a heck of a lot faster than the "loop-de-loop" trajectories for Galileo, 6 years and 2 months to get to Jupiter, and for Cassini, 6 years and 9 months to get to Saturn. You're forgetting one important thing, the trajectory. For both Voyagers, they took what amounted to the most direct route to Jupiter. I realized that - a direct trajectory from Earth to Jupiter. For Galileo and Cassini, they took the least direct route, ping-ponging around the inner Solar System for a while before heading out to Jupiter. This added to the travel time. That is what I meant about my comment about the "loop-de-loop" trajectories for Galileo and Cassini; the way that they had several flybys of Earth and Venus to get the velocity to head to Jupiter. The spacecraft were too heavy to make the direct ascent from Earth to Jupiter. |
#19
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"Scott M. Kozel" wrote in message
... "David Nakamoto" wrote: For Galileo and Cassini, they took the least direct route, ping-ponging around the inner Solar System for a while before heading out to Jupiter. This added to the travel time. That is what I meant about my comment about the "loop-de-loop" trajectories for Galileo and Cassini; the way that they had several flybys of Earth and Venus to get the velocity to head to Jupiter. The spacecraft were too heavy to make the direct ascent from Earth to Jupiter. Too heavy given the current crop of boosters. If you had a powerful enough booster, actually a third or fourth stage, the one that actually gets them out of Earth orbit and into a transfer orbit to Jupiter, you could have flown either Galileo or Cassini on a direct trajectory. -- Sincerely, --- Dave ---------------------------------------------------------------------- It don't mean a thing unless it has that certain "je ne sais quoi" Duke Ellington ---------------------------------------------------------------------- |
#20
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Chemical rockets and gravity assists are so history... Any serious
mission to Jupiter and beyond (including Titan) will have to rely on nuclear power. In fact, huygens would have never landed on Titan if Cassini wasn't powered by the Radioisotope Thermoelectric Generator... Hopefully we'll have Nuclear Thermal Rocket in our disposal when the time comes for the next big Titan mission. Another alternative is to use Nucleat Electric Propulsion (that is to feed ion engine from nuclear reactor or a powerful RTG), just like the one they are planning to use for the JIMO mission in 2009. Speaking of rovers, baloons, etc. -- these will also HAVE to use RTG for any lasting mission. It's very encouraging that the upcoming Mars Science Laboratory will rely on such power source either. If it will be airplane (I think it's unlikely), rather than baloon or a rover, then, again, it would probably need nuclear-powered jet engines... People, really, just forget arout oxygen or other stuff like that :-) I don't think Titan rovers are coming any time soon, we'll possibly get to Triton sooner. Just another fascinating world with it's hudge ice volcanoes which are just as fascinating as rivers of methane... Will it be Titan or Triton -- the main idea remains the same. |
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