Exploring Alternatives: Harnessing Jupiter's Radiation for Probe Power"

In summary, there was a public outcry when the Cassini probe was launched with a nuclear power supply, but no alternatives were offered. The idea of using a planet's radiation as a power source for a probe was brought up, but it was deemed unfeasible due to unpredictable particle impacts and potential damage to electronics. The use of tethers or solar sails as alternative means of propulsion was also discussed, but the most viable option for powering a probe in orbit around Jupiter or Saturn is still nuclear power. The exact power requirements for a probe in orbit are not clear, but it is estimated that the Cassini probe required 875 watts at launch and 700 watts at the end of its mission. The use of gravitational slingshots and
  • #1
LURCH
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As most of you will recall, there was considerable public outcry when the Cassini probe was launched with its nuclear power supply. However, no alternatives to nuclear decay were offered as a power source. The main thinking seemed to be that the probe should just go without the power it provides.

This got me to wondering about a power source which seems rather obvious to me. I know that when we send a probe to Jupiter, we have to shield it pretty heavily against the fierce radiation around that planet (not sure if the same is true for Saturn). It seems to me that shielding a probe against radiation, and then supplying it with an internal source of radiation to power its electrical systems is ironic, to say the least. Doesn't it seem like there ought to be some way to use the copious amounts of raditation coming from the planet for a power source?
 
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  • #2
How is that? Power generated by nuclear decay uses the heat off of that decay and is converted into electricity by thermocouples. For planets past the asteroid belt, there isn't enough light from the sun to power probes with just solar panels. The panels would have to be enormous! There isn't enough energy in the radiation coming off of Jupiter or Saturn to power a probe that small. Remember that detectors need to convert the impacts into an electrical signal, but that signal is extremely small and even with millions of impacts, doesn't add up to much in the way of voltage for a power hungry probe. And don't forget the trip out there. What is going to power the probe on it's way out to the outer planets? Those solar panels will only take it so far. So in retrospect, nuclear power seems like a highly viable choice.
 
  • #3
There isn't enough energy in the radiation coming off of Jupiter or Saturn to power a probe that small.

Can we explore this further? What are the power requirements of a probe once it's in orbit around Jupiter/Saturn? How much energy can we draw from a planet's radiation? Are there other options such as using a lengthy tether to draw energy from the planet's magnetic field as the probe whips through it?

Granted, getting there is another matter. How much energy is required for maneuvering en route? The Galileo and Cassini probes used gravitational slingshots to increase their velocity. Ion propulsion, solar sails, etc. are alternatives, albeit still new techs, for getting there. Offhand, I'm not sure how useful those are for maneuvering.
 
  • #4
Originally posted by Phobos
Can we explore this further? What are the power requirements of a probe once it's in orbit around Jupiter/Saturn?

From this saturn.jpl.nasa.gov/cassini/msnstatus/quickfacts2000.shtml[/URL] It says that it provided 875 watts at launch and 700 watts at mission end. Unfortunately, the page isn't coming up for me, so I got the information by googling for "Available Power Cassini Orbiter RTG", and looking at the cache.

[quote]
How much energy can we draw from a planet's radiation? Are there other options such as using a lengthy tether to draw energy from the planet's magnetic field as the probe whips through it?
[/quote]

Drawing energy from radiation is unfeasable AFAIK, because you can't predict where the particles will hit. Even if you could draw power from it, it would do more damage than the electronics could survive. The tethers are an option, but they are really big, and really heavy. Also, after sitting in the cold for a few years, things have a tendency to break. If a tether is your only option for power production, you can't build in any redundancy without really upping the weight of the vehicle. They also aren't technologically mature enough to risk sending on an exploration mission IMO. We've only tried using them once, and they melted their attachment to the test base.

[quote]
Granted, getting there is another matter. How much energy is required for maneuvering en route?
[/quote]

This [PLAIN]http://en2.wikipedia.org/wiki/Gravitational_slingshot [Broken] says that the Cassini needed 2km/sec of delta V. It's a decent amount, but certainly attainable. With an Isp of 350, the mass of fuel needs to be about 80% of the mass of the probe for that magnitude burn.

The Galileo and Cassini probes used gravitational slingshots to increase their velocity. Ion propulsion, solar sails, etc. are alternatives, albeit still new techs, for getting there. Offhand, I'm not sure how useful those are for maneuvering. [/B]

Solar sails are not enough. You need to slow down once you get there to go into orbit, and sails only accelerate one direction. Ion propulsion would decrease the fuel required, but you'd still want to use the "free" energy provided by slingshotting. The previous site said Cassini would have needed in excess of 15km/sec delta V to go there directly. That works out to 78 times the mass of the ship in fuel for a bi-propellant or around 4 for an ion engine.
 
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  • #5
Wasn't thinking about propulsion, that's a whole different kind fo power. I'm just talking about power for the instruments and other electrical systems. What I don't get is the idea that the planet emits enough radiation to fry the electronics, but not enough to power them? As for the mechanism, I wasn't thinking of sails or tethers, but rather the shielding used to protect the probe. It is specifically designed and placed to absorb radiation from the planet. Can't that energy be converted to electrical power? Or perhaps the method of conversion would be heavier than the power source currently used.
 
  • #6
Originally posted by Phobos
Can we explore this further? What are the power requirements of a probe once it's in orbit around Jupiter/Saturn? How much energy can we draw from a planet's radiation? Are there other options such as using a lengthy tether to draw energy from the planet's magnetic field as the probe whips through it?

Well sure there are ways around it. I guess I misunderstood and thought he was talking about Galileo and Cassini probes specifically. But I'd think you'd have to have a pretty large "detector" setup to absorb enough radiation (emr, neutrons, nuclei) coming off of Jupiter or Saturn. The tether idea is a good idea, but it would have to be a pretty long and tough tether.
 
  • #7
Originally posted by LURCH
Wasn't thinking about propulsion, that's a whole different kind fo power. I'm just talking about power for the instruments and other electrical systems. What I don't get is the idea that the planet emits enough radiation to fry the electronics, but not enough to power them? As for the mechanism, I wasn't thinking of sails or tethers, but rather the shielding used to protect the probe. It is specifically designed and placed to absorb radiation from the planet. Can't that energy be converted to electrical power? Or perhaps the method of conversion would be heavier than the power source currently used.

The radiation is random and sporatic at best. It's not is a full bath of radiation. And the way that it fries electronics, at least for nuclei and neutrons, is that it pits electonics as it passes through them. It happens regardless of shielding (unless you have enough shielding), and probes seem ok around the planets showing to me at least that a catastrophic hit to the electronics is rare and that the highest energetic particles couldn't provide computers and instrumentation with 875 to 700 Watts of power. Even at lower power, I just don't feel that the interactions would be enough.
 

1. How is the power source for Jupiter probes chosen?

The power source for Jupiter probes is chosen based on several factors, including the length of the mission, the power requirements of the instruments on board, and the distance from the Sun. Solar panels are typically used for shorter missions close to the Sun, while radioisotope thermoelectric generators (RTGs) are used for longer missions and in areas with less sunlight, such as Jupiter.

2. What is an RTG and how does it work?

An RTG is a type of power source that uses the heat generated by the radioactive decay of plutonium-238 to produce electricity. The heat is converted into electricity by thermocouples, which are made of two different types of metal that produce an electric current when exposed to a temperature difference.

3. How long can an RTG power a Jupiter probe?

The lifespan of an RTG depends on the amount of plutonium-238 used and the power requirements of the probe. Typically, an RTG can power a Jupiter probe for 8-10 years, but some have lasted much longer. For example, the Voyager 1 and 2 missions, which launched in 1977, are still powered by their original RTGs and are expected to continue functioning until at least 2025.

4. Are there any alternative power sources for Jupiter probes?

Yes, in addition to solar panels and RTGs, some Jupiter probes have used batteries as a backup power source. However, batteries have a limited lifespan and are not a sustainable power source for long-term missions. Some future missions to Jupiter may also explore the use of nuclear fusion as a power source, but this technology is still in development.

5. How is the power from Jupiter probes managed and distributed?

The power generated by Jupiter probes is managed and distributed by a power management and distribution system (PMAD). This system controls the flow of electricity from the power source to the various instruments and systems on board the probe. It also regulates the temperature of the power source to ensure it stays within the optimal range for efficient power production.

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