I hope NASA leaves the nuclear powered stuff back on Earth, though.

I could be mistaken, but I think it may be too far from the sun to use solar power. If so, then I think the only other viable choice is nuclear.

Solar Power is still practical at Jupiter, but requires very large solar arrays. Beyond Jupiter, solar radiation is so low that the weight of the solar arrays would be larger than the science packages, navigation, communication and propulsion systems combined. There are other considerations. On Mars, the Spirit and Opportunity rovers used solar, but they were small and didn't require more power than a relatively small solar array could provide. But a significant part the energy from the solar array needed to be stored in batteries to keep heaters active during the Martian nights and for communication tasks at night. We also learned that dust quickly accumulated on the arrays reducing their output significantly and that if the rover got stuck at a location and the array was tilted away from the sun, there might not be enough power to maneuver out of that situation. Curiosity, has much greater power demands than could have been met with solar arrays. Using solar arrays would have required long periods to charge batteries that would then discharge quickly, meaning the rover would spend most of it's time charging batteries rather than doing science.

Europa is tidally lock with Jupiter, meaning it keeps the same side facing Jupiter as it orbits (like the moon does with earth). Each orbit it makes around Jupiter is a little more than 3 1/2 days. This means that once a Europa mission probe landed it would spend 46 hours in darkness then 46 hour in daylight every orbit. Europa is much colder than Mars and it would be essential to keep the craft warm on those Europa nights(and probably days also). Given these and other considerations, solar could only be a supplemental power source at best. It is unlikely that this would be a single craft to Europa mission and would likely involve an orbiter and a lander. The orbiter would most likely orbit Jupiter and drop off a lander much the way Cassini dropped Huygens as it passed Titan. This keeps the transmission power requirements on the lander low because it can relay through the orbiter which is much closer. The lander therefore does not need a high power transmitter or a large antenna. The orbiter would likely be solar powered.

It's unlikely the first mission to Europa would involve a lander, much less trying to drill into the ice to the possible ocean below. A mapping mission orbiting Europa with ground penetrating radar and atmospheric sampling would proceed any landing mission.

Obviously you could power something with solar at that distance but, as you point out, it wouldn't be difficult to do the needed science with it.

Last edited Thu Jun 18, 2015, 10:35 PM - Edit history (2)

Electrical power is supplied by three MHW-RTG radioisotope thermoelectric generators (RTGs). They are powered by plutonium-238 (distinct from the Pu-239 isotope used in nuclear weapons) and provided approximately 470 W at 30 volts DC when the spacecraft was launched. Plutonium-238 decays with a half-life of 87.74 years,[22] so RTGs using Pu-238 will lose a factor of 1?0.5(1/87.74) = 0.79% of their power output per year.

In 2011, 34 years after launch, such an RTG would inherently produce 470 W × 2? 34/87.74) ? 359 W, about 76% of its initial power. Additionally, the thermocouples that convert heat into electricity also degrade, reducing available power below this calculated level.

By 7 October 2011 the power generated by Voyager 1 and Voyager 2 had dropped to 267.9 W and 269.2 W respectively, about 57% of the power at launch. The level of power output was better than pre-launch predictions based on a conservative thermocouple degradation model. As the electrical power decreases, spacecraft loads must be turned off, eliminating some capabilities.

They only push about 100 to 150w. Good for a trickle charge, but for propulsion, they may need something more. A method of cracking hydroxyls, would be good.

Like any mission to the outer solar system. Like Saturn, or Pluto, or a Mars rover (Curiosity) that needs more reliable power.

And your 100w claim is utter tosh. Sounds like you take the novel "The Martian" as current science (a very good read, BTW, but fiction). The Voyager RTGs have more than 100w even after decades in deep space.

And Curiosity is powered solely by an RTG. As is Cassini.

As is New Horizon, about which:

A cylindrical radioisotope thermoelectric generator (RTG) protrudes from one vertex in the plane of the triangle. The RTG will provide about 250 W, 30 V DC at launch, and is predicted to drop approximately 5% every 4 years, decaying to 200 W by the encounter with the Plutonian system in 2015. The RTG, model "GPHS-RTG," was originally a spare from the Cassini mission. The RTG contains 10.9 kg (24 lb) of plutonium-238 oxide pellets. Each pellet is clad in iridium, then encased in a graphite shell. It was developed by the U.S. Department of Energy at the Materials and Fuels Complex (formerly Argonne West), a part of the Idaho National Laboratory in Bingham County. Less than the original design goal was produced because of delays at the United States Department of Energy, including security activities, that delayed production. The mission parameters and observation sequence had to be modified for the reduced wattage; still, not all instruments can operate simultaneously. The Department of Energy transferred the space battery program from Ohio to Argonne in 2002 because of security concerns. There are no onboard batteries. RTG output is relatively predictable; load transients are handled by a capacitor bank and fast circuit breakers.

The amount of radioactive plutonium in the RTG is 10.9 kg (24 lb), about one-third the amount on board the Cassini–Huygens probe when it launched in 1997. That launch was protested by some people. The United States Department of Energy estimated the chances of a launch accident that would release radiation into the atmosphere at 1 in 350, and monitored the launch as it always does when RTGs are involved. It was estimated that a worst-case scenario of total dispersal of on-board plutonium would spread the equivalent radiation of 80% the average annual dosage in North America from background radiation over an area with a radius of 105 km (65 mi).

Bring it along, by all means, but we will be fighting actual fluid dynamics, under multiple atmospheres of pressure. 250w @ 30vdc is about (1) modern solar panel, which would put it at about 9A. That's good for a rover on 1/3 atmosphere, but is piss poor for fighting a current. You'd be weighed down by batteries in series/parallel to store and stack usable cranking power, and find yourself at the bottom of Europa's abyss before it transmits it's first data packet.

Including both fucking Voyager probes, running solely on PU-238 RTGs for nearly 40 years.

Drops microphone.

Sheesh!

This ain't space, or the surface of Mars. This is an ocean with currents. Think nuclear submarine.

"The mission parameters and observation sequence had to be modified for the reduced wattage; still, not all instruments can operate simultaneously."

I'm an electrical engineer and I can assure you that's enough power to move around, albeit at low speed.

And btw, my electric dragster just broke the world record in the quarter mile for it's class and division. One million watts, 9.60s quarter, 130mph. My driver earned his NHRA license on that run... Next we set records.

you can kiss that ROV goodbye. To get that you would need about 800w to cover propulsion and have anything left in the budget for science. Idealy, 20HP is what you want to explore at depth. And unless were using a tethered system, that 50w will be eaten by communications.

If we are doing this just to say we did it, fine. But if we're there to do science, we will need more power.

http://www.rov.org/rov_categories.cfm

I keep reading that they are fucking.

is Europa may offer the best chance (besides Earth) of finding life in our solar system. Saturn is a ball of gas and Mars is a lifeless desert. Europa is covered with water/ice and possibly a liquid ocean holding twice as much water as the Earth's oceans. I don't think a big 'ol chunk of plutonium is the best thing to send to a planetary body that may contain life, but maybe I'm just ignorant like you said.

And BTW, the Curiosity rover is powered by an RTG, and it is on Mars, which is another place there may be life. And also, RTGs are pretty damned safe. And I don't think Mars will mind a few kg of Pu238 left there. Likewise Europa, but again, this mission will not be landing. Like they are going to do with the Cassini probe, they'll fly it to crash into Saturn when the mission ends, mainly to prevent bacterial infection from Earth.

Maybe bacteria (which would really be cool) but everything I've read about Europa says it's the most likely body to have more advanced, maybe even sentient life. It'd be a shame if we screwed it up.

But yes, bacterial life on Mars would be awesome.

Re: Europa, consider this. I don't think that Europa is very geologically active. Other than tidal energy, I am not sure how advanced life could get. I would bet not very. But it would be cool to send a submarine through the ice and have it swallowed by some monster fish living under the ice. (At least as long as they got it on film.)

And any life on it is probably at the bottom of it's 100-km deep ocean, near thermal vents for warmth and sustenance.

A chunk of plutonium isn't going to harm it, or the life it may harbor.

Hell, a Hiroshima-sized nuclear bomb detonated on it's surface probably wouldn't even draw a second look from it's denizens.

and plutonium radiation are two different animals. The Sun is mostly electromagnetic radiation but plutonium is alpha radiation. Plutonium 239 in spent fuel rods is what's justifiably causing the freak out over the Fukushima disaster.

Anyway, just my opinion.

Cassini completed its initial four-year mission to explore the Saturn System in June 2008 and the first extended mission, called the Cassini Equinox Mission, in September 2010. Now, the healthy spacecraft is seeking to make exciting new discoveries in a second extended mission called the Cassini Solstice Mission.

The mission’s extension, which goes through September 2017, is named for the Saturnian summer solstice occurring in May 2017. The northern summer solstice marks the beginning of summer in the northern hemisphere and winter in the southern hemisphere. Since Cassini arrived at Saturn just after the planet's northern winter solstice, the extension will allow for the first study of a complete seasonal period.



Cassini launched in October 1997 with the European Space Agency's Huygens probe. The probe was equipped with six instruments to study Titan, Saturn's largest moon. It landed on Titan's surface on Jan. 14, 2005, and returned spectacular results.

Meanwhile, Cassini's 12 instruments have returned a daily stream of data from Saturn's system since arriving at Saturn in 2004.

http://saturn.jpl.nasa.gov/mission/introduction/

Non-nuclear energy on Earth comes from a nuclear energy source (the Sun).

Food, water, shelter - all that stuff won't be needed by our little metal buddies.

Go get em

to the Sun you'd be dead. And if you handle plutonium-238 you'll probably die. If Cassini had collided with Earth and scattered it's plutonium, NASA figured it would have caused up to 5000 additional cancer deaths.

I understand perfectly the advantages with a nuclear propulsion system-I just don't think it's a good idea for a landing or even a close fly by on a body that has the best possible chance at life outside of Earth.

And I may go Europa too.

then they will launch a racist screed about the Europians, which will be confused by the Europeans and a holy war will ensue.

because they can't spell.

they could still say (a) god did it (b) that it came from earth originally

There is always a loophole.

Europa is a moon of Jupiter. Titan and Enceledus are moons of Saturn.

I actually think that Titan and Enceledus are better bets.

you rock!

Like, 200 degrees warm?

Just above the freezing point at the crust/ocean boundary, with temps rising as you go down. That's just a guess on my part, though.

When our probe is atomized, it will confirm once and for all, that Clarke was not of this world.

"we're looking at a mission that would orbit Jupiter, make close flybys of Europa and then zip out of the high radiation region"

"On a typical flyby, we would turn on our remote sensing instruments. We would image the surface. We would interrogate the surface with spectroscopy and we would do the same thing on the way out.,

And we would essentially rinse and repeat and do this many, many, times"

http://www.jpl.nasa.gov/video/details.php?id=1383

Or the Star Child, or something.

Attempt no landings here.