Cassini-Huygens Saturn Orbit Insertion Imminent

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."

Comments

Re:450 watts?

[Fouquet]

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 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:Victory of SCIENCE over ECOIDIOLOGY

[joehoya]

Lots of people are saying that Cassini uses a nuclear reactor... this is not the case as Cassini actually uses 3 Radioisotope Thermoelectric Generators (RTG). RTGs are different from reactors in that they are much simpler devices which produce electricity directly from the decay of radioactive material, in this case PU-238. Reactors on the other hand produce power from heat generated by a controlled nuclear chain-reaction.

Re:Ah, but did it generate the 450?

[Rei]

I'll do it for gasoline. :)

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? :)