Cassini-Huygens Saturn Orbit Insertion Imminent 205
Anonymous Explorer writes "Fresh
off of its fly-by with the Saturnian satellite Phoebe, the
Cassini-Huygens
craft is set for Saturn
Orbit Insertion on June 30, 2004.
Cassini-Huygens has a planned four year mission ahead for Saturn
and its many moons. With 450 watts of power for the electronics, this
mission has plenty enough horses to run the stretch with plenty-o-pep
to spare. Thanks to all that power, and the plethora of electronics on Cassini
and the Huygens
probe, we
can now hear sounds from Saturn. Pretty cool stuff! Festivities are
scheduled to begin on June 29th with a broadcast of Cassini Saturn
Orbit Insertion Press Conference on Nasa TV. SOI [PDF link] will occur after Cassini
fires its main engine for 96 minutes, in order
to slow down and be grabbed by the pull of Saturn. As always we extend
an invitation to everyone to join
#cassini on irc.freenode.net and
help us celebrate this historic mission."
450 watts? (Score:5, Funny)
Re:450 watts? (Score:2)
Of course, if you had a team of people working to make your computer as efficient as a Saturn probe...
Re:450 watts? (Score:2)
Re:450 watts? (Score:4, Funny)
Re:450 watts? (Score:4, Informative)
Considering the computer power needed to go to the moon, it's not likely that this thing needs an 3.2Ghz processor and GeForce
My Epia-M is plugged in taking about less than 30W of power (including HDD and DVD-ROM)... so really the equivilent of an efficient 1Ghz processor wouldn't need anything near your desktop machine's draw.
Re:450 watts? (Score:5, Interesting)
Re:450 watts? (Score:2)
Re:450 watts? (Score:2)
Besides, part of the power of a PC is the flexibility (it can be a calculator, gaming rig, media box, etc etc). With a specialized piece of hardware such as a satellite, I'm sure that having there are mor
Re:450 watts? (Score:5, Funny)
Like watt?
Re:450 watts? (Score:2)
Re:450 watts? (Score:5, Informative)
That's a bit low, but not too far off. Cassini uses 3 RTG power sources to generate the ~700-800 W necessary for the science instruments. Solar cells are not practical at that distance.
This PDF file [nasa.gov] details the power supply situation on the spacecraft.
It's pretty remarkable how little power spacecraft like this consume (and I'm pretty sure that Cassini is the most power hungry of the 'outer-solarsystem' probes NASA has launched).
Re:450 watts? (Score:5, Informative)
Re:450 watts? (Score:2)
Ah, but did it generate the 450? (Score:5, Insightful)
Your little computer is a lot bigger if you include the size of the Power Station it is attached to through a long peice of wire.
Someone should calculate how the amount of coal or oil that would be needed to provide power for Cassini if it weren't nuclear. Or the size of solar cells needed at that distance from the sun (and their wieight).
Re:Ah, but did it generate the 450? (Score:5, Informative)
I googled around and found some stats from the power industry as "energy density of fossil fuel"
Energy density of Fuel Oil: 42.5 MJ/Kg
Energy density of Anthracite Coal: 31.4 MJ/Kg
MJ/Kg is Mega (million) joules per Kilogram. Our power unit provides 450 watts, thus uses 0.00045 MJ/s. A day's worth of power is 0.00045 MJ/s 3600 s/hour * 24 hours/day = 38.9 MJ. (Remember your signifigant digits!)
To convert that back to weight:
38.9 MJ/Kg / 42.5 MJ = 0.915 Kg/day of Oil
38.9 MJ/Kg / 31.4 MJ = 1.23 Kg/day of Coal
We are in the 7th year of the flight, so:
0.915 Kg/day * 365.26 days/year * 7 years = 2340 Kg of Oil
1.23 Kg/day * 365.26 * 7 = 3150 Kg of Coal.
Plus or minus.
Re:Ah, but did it generate the 450? (Score:5, Informative)
So
2340 Kg / 0.40 = 5850 Kj of oil
3150 Kg / 0.40 = 7880 Kj of coal
Re:Ah, but did it generate the 450? (Score:2, Insightful)
Re:Ah, but did it generate the 450? (Score:2)
Re:Ah, but did it generate the 450? (Score:3, Interesting)
Are you sure? That's pretty close to true on earth, where the cold side of a Carnot cycle is going to be at around 300 K. Space, however, is mostly a nice, big, cold blackbody at around 3 kelvin or so (cosmic microwave background.) That should help quite a bit.
On the other hand, other posters have noted that the mass calculation neglects the o
Re:Ah, but did it generate the 450? (Score:2)
Re:Ah, but did it generate the 450? (Score:2)
Re:Ah, but did it generate the 450? (Score:5, Informative)
Let's assume that Cassini averages needing 700 watts over the course of its lifetime, and lets assume a lifetime of 18 years. That's about 80 MWh of power. Assuming a 40% efficiency diesel engine burning gasoline and oxygen (have to take the O2 with you!)...
Gasoline has an energy density of 45.8 MJ/kg. Since 2 molecule of gasoline requires about 25 molecules oxygen (O2) to react, you have a molar ratio of 1 mole gasoline to 12.5 moles oxygen. 1 mole of gasoline mass about 114 grams; 12.5 moles of o2 mass about 400 grams. So, your overall energy density is about 10.2 MJ/kg.
Since we're burning at 40% efficiency, that's about 4.1MJ of energy per kg fuel/oxidizer. 1 joule = 0.0002778 Wh. 4.1MJ/kg = 1.1kWh/kg. 80MWh / 1.1kWh/kg = ~73 metric tons.
33 kilograms of plutonium suddenly sounds quite appealing, ne?
Re:450 watts? (Score:2)
Not even 0.5kilowatts.. (Score:4, Interesting)
Re:Not even 0.5kilowatts.. (Score:2, Informative)
Re:Not even 0.5kilowatts.. (Score:2, Funny)
Re:Not even 0.5kilowatts.. (Score:5, Informative)
Re:Not even 0.5kilowatts.. (Score:2)
Damn. That is bigger than I thought it would be. One question though. Where's the headphone jack to listen for pulsating alien transmissions?
Re:Not even 0.5kilowatts.. (Score:5, Funny)
What, like 75 meters?
Re:Not even 0.5kilowatts.. (Score:5, Informative)
I'm sure I'm not using the correct terminology (in case HAM radio experts are reading this) but that is the gist of it.
Re:Not even 0.5kilowatts.. (Score:2, Informative)
Some, but it is considered very bad form to use more power than necessary. Transmitting across the ground is very different than transmitting through the space. Line of sight drastically reduces the ammount of power you need, as well as using directional antenas.
Re:Not even 0.5kilowatts.. (Score:2, Informative)
Only 20 Watts... (Score:4, Interesting)
Actually, many Hams get by fine just a few watts (Score:4, Interesting)
"some HAMs are using 10 kilowatts upwards just for transmitting earth-to-earth!"
Actually, ignoring the 1.5KW max Ham radio ops are legally bound to, most Ham operators operate in the 100 watt range (in the HF freqs == "shortwave"), and there's a dedicated core of low-power enthusiasts who communicate around the world on 5 watts, 1 watt or even a few hundred milliwatts. (The microwatt crew even come out during favorable solar conditions).
Check out these guys [qrparci.org] for a starting point.
It varies by spectrum of course (VHF/HF/etc.) but I've personally worked every continent with less than 5 watts using just a homemade wire antenna, no fancy NSA-like array of metal high in the air.
Antarctica was the most fun - Russian op down there at their research station. Darn neatstuff!
Victory of SCIENCE over ECOIDIOLOGY (Score:3, Interesting)
Lucky the officials at NASA and ESA weren't that stupid and fought off this attack.
The tremendous success of this mission illustrates how these 21th century idiologists are could stiffle science and cause harm for the whole world.
It makes me wonder if we could get this done today or in year with the eco rising to power in Europe and perhaps US after the elections, too.
Re:Victory of SCIENCE over ECOIDIOLOGY (Score:5, Insightful)
Yes, the greenies were making a mountain out of a molehill. Nuclear powered satellites have been launched for years, and the reactors are specifically designed to survive the destruction of the spacecraft.
The problem is that we live in a world that is only willing to offer 30 seconds of attention about any subject at a time.
Re:Victory of SCIENCE over ECOIDIOLOGY (Score:5, Funny)
What are you talking about? It's not like the entire World has ADD or some... Hey, what's that shiny thing over there?
Re:Victory of SCIENCE over ECOIDIOLOGY (Score:2)
Re:Victory of SCIENCE over ECOIDIOLOGY (Score:2)
Re:Victory of SCIENCE over ECOIDIOLOGY (Score:2)
Re:Victory of SCIENCE over ECOIDIOLOGY (Score:2)
Where do we have to go now to enjoy a nice clean refreshing vacuum?
Re:Victory of SCIENCE over ECOIDIOLOGY (Score:4, Funny)
I dunno, the appliance section of [insert retail store]?
Re:Victory of SCIENCE over ECOIDIOLOGY (Score:5, Informative)
Re:Victory of SCIENCE over ECOIDIOLOGY (Score:2)
If it ticks like a clock, and keeps time like a clock, it's a clock. If it harnesses energy from the decay of nuclear elements, and it does so by converting heat to electricity, it's a Nuclear reactor.
Re:Victory of SCIENCE over ECOIDIOLOGY (Score:4, Informative)
There are some very significant differences. A Nuclear reactor involves an induced chain reaction. This is just harnessing energy from passive decay. RTG's last a lot longer, but produce less power.
Re:Victory of SCIENCE over ECOIDIOLOGY (Score:2)
Just because you get lucky doesn't mean risk doesn't exist.
Re:Victory of SCIENCE over ECOIDIOLOGY (Score:4, Insightful)
Take your pick.
Re:Victory of SCIENCE over ECOIDIOLOGY (Score:2)
Take your pick.
I pick neither.
Horses? (Score:2, Funny)
Lets hope none of them are named Smarty Jones...
Slashdot NASA Early (Score:3, Funny)
I Wonder... (Score:5, Funny)
Re:I Wonder... (Score:3, Funny)
After this insertion... (Score:5, Funny)
Here, I'll help you out.
-1, Troll.
sounds? (Score:2, Funny)
Sorry. Had to do it.
Re:sounds? (Score:2)
Insertion Imminent (Score:5, Funny)
Re:Insertion Imminent (Score:2)
Re:Insertion Imminent (Score:2)
=Smidge=
Re:Insertion Imminent (Score:2, Funny)
what did they name it?
Urectum!</farnsworth>
Sounds from Saturn? (Score:5, Funny)
I hope it takes photos (Score:3, Interesting)
BTW, how thick are the rings at the point where the probe is passing through them? How long will it take to clear that space?
This is from NASA's page (Score:3, Informative)
Re:I hope it takes photos (Score:4, Informative)
Re:I hope it takes photos (Score:2)
Re:I hope it takes photos (Score:3, Informative)
It is flying through a visible gap, and it's an area that seems to be clear of debris according to all the analysis done so far. But it could just be that the debris is so sparse that it's not visible.
The entry point is actually well outside the visible rings, but there is another very faint ring (G ring) even farther out.
NASA realized this during the design phase, which is why they are rota
Re:I hope it takes photos (Score:2)
Cassini's Real Interaction with the Rings (Score:4, Interesting)
Saturn right now is tilted, so that the south/"bottom" side of its rings is facing towards the Sun and Earth. Hence, Cassini is approaching Saturn from "underneath" as we see it from Earth. The orbit insertion requires Cassini to pass through the equatorial/ring plane south-to-north as it approaches the planet. It will fire its rocket while on the north side of the rings, and then coast back to the south side on its way back out.
Now, how is Cassini doing that safely? It's doing so by going through the ring plane where there are no rings. It could be thought of as a "gap", but Cassini really isn't anywhere near the rings when it crosses them. The crossing points are far outside the main mass of the ring system.
A rough analogy is this. Suppose you lived in Alaska, and had a sailboat named Cassini. Now suppose you had to sail from Alaska to Mexico without bumping into anything. Naturally, you'd pass between Hawaii and the continental US. That's a rough analogue to what's going on at Saturn - the main mass of the rings is like the continental US landmass (and there's a few small intra-ring gaps like the Mississippi River), while there's a few small outside rings sort of like the Hawaiian islands.
Would it be possible that your sailboat bumped into a rock or debris or something that we didn't know was there? Yes. Is that possibility remote enough that it makes for the safest course to your destination? Also yes.
ObSpock (Score:2)
Re:ObSpock (Score:5, Informative)
And then there's the other things that could possibly cause sound - some of these futurisitic engines are supposed to be powerful ion drives or plasma thrusters, which means that there are very powerful magnetic fields being used and streams of high-velocity charged particles, both of which could possibly have an impact on certain parts of your spacecraft when you get close and make noise. If a beam weapon starts cutting at your ship's hull, your hull is definitely going to make some noise, especially when mechanical components are damaged or gasses start to leak. Etc. There would be lots of sound in a space battle.
You forgot... (Score:2)
Re:ObSpock (Score:3, Insightful)
But from outside, you wouldn't hear anything, unless electrical interference from the ship's system or natural sources was being picked up by your space suit radio. What is interesting, is that astronouts can communicate without radios if
Sound in space? (Score:2, Interesting)
Re:Sound in space? (Score:3, Informative)
Re:Sound in space? (Score:3, Informative)
Pheobe as a source of ice (Score:4, Interesting)
Re:Pheobe as a source of ice (Score:3, Insightful)
absolutely (Score:2)
Re:Pheobe as a source of ice (Score:5, Informative)
Re:Pheobe as a source of ice (Score:2)
Re:Pheobe as a source of ice (Score:2)
Re:Pheobe as a source of ice (Score:2)
Granted, it's a much slower and cooler process than you would find at a commercial nuclear plant, or in the belly of a ship, but it is the same process.
Re:Pheobe as a source of ice (Score:3, Insightful)
Fission reactors typically control a chain reaction and use the heat to create steam that turns a generator. That generator produces the electricity.
Yes, at an atomic level the processes are similar (or even the same) but it is important to note the differences. The word nuclear is often maligned due to lack of understanding.
Re:Pheobe as a source of ice (Score:2)
Re:Pheobe as a source of ice (Score:3, Informative)
Solar-powered ion drives don't require a lot of power; they use low thrust over long periods of time. Check out this link [nasa.gov] for an example. Note that the name of the craft is "Deep Space 1." It went to the asteroid belt, but even if it went out as far as the orbit of Saturn, it would just have to operate at lower thrust.
That why Cassini needed a nuclear reactor.
Cassini doesn't have a nuclear reactor, it has a radioactive source that provides ener
Re:Pheobe as a source of ice (Score:2)
In which case, an RTG is indeed a reactor, although nowhere near as energetic as the ones run by Exelon, for example. Naturally decaying radioactive material can cause a chain reaction, although it's almost never long-lived since the material density is almost never great enough to sustain it.
Ask the poor fool
Re:Pheobe as a source of ice (Score:4, Informative)
A variant of this idea was explored by Isaac Asimov way back in the novella, The Martian Way (Galaxy Science Fiction, November 1952; subsequently republished in several collections).
The characters in the novel propose capturing chunks of ice from Saturn's ring system. We don't need to grab a whole moon--there are cubic-mile-sized chunks of ice in the rings. They might be a bit more manageable to manoeuvre. There are lots to choose from, too.
Re:Pheobe as a source of ice (Score:2)
Na, just go down to your local grocery store. They should have some.
Re:Pheobe as a source of ice (Score:2)
"Phoebe! Can you bring me some ice please?"
"Get it yourself!"
See?
Sound? What sound? (Score:5, Informative)
Re:Sound? What sound? (Score:2)
The Song of Saturn At Last! (Score:3, Funny)
"Thanks to all that power, and the plethora of electronics on Cassini and the Huygens probe, we can now hear sounds from Saturn."
Not to mention that giant space phonograph needle they included at the last minute. Now we just have to have it doesn't skip on the Cassini Division.
(Append witty RIAA reference here.)
Nah, they did it two days early (Score:4, Funny)
Choice: Saturn or Spacewalk (Score:4, Informative)
On Wednesday there will be an EVA on the ISS right around the time the Cassini stuff will be happening. Thus, NASA TV had to choose, for the first time, which thing happening in space was more exciting.
How cool is that? There's actually enough going on up there that one TV channel is not enough!
Whadya know, the revolution IS televised.
Let the orbital insertion begin... (Score:4, Funny)
The real reason for the mission (Score:2, Funny)
Re:The real reason for the mission (Score:2)
Shorter Slashdot... (Score:3, Insightful)
7 off-topic "troll" posts.
30 posts regarding the nuclear decay powering the craft or simply clarifying the fact that it is not a nuclear reactor.
96 comments making jokes about the use of the word "insertion" with more than 80 of those comments also mentioning Uranus.
I was an intern at JPL... (Score:5, Interesting)
Back then, the project was called "CRAF/Cassini" where CRAF was "Comet Rendezvous/Asteroid Flyby." CRAF was supposed to be the sister ship to Cassini, but it was cut for budgetary reasons. Too bad... with all the design work done how much could it have cost to just build another ship?
See, we were building this neat computer that would be reused on the next generation of probes, instead of having custom computer hardware for each... but of course it didn't work out that way.
I was lucky enough to see Cassini (and Galileo) in the Vehicle Assembly Facility. There was an observation deck where you could watch the guys in the clean room building the spacecraft. It was very cool to look down and realize, "that is going to Saturn." Or wherever.
Cassini is the last of the old school probe designs... a gigantic and expensive. She'll give us a heck of a show.
Re:Sounds of Martian Life?!! (Score:5, Funny)
Re:Sounds of Martian Life?!! (Score:3, Informative)