Can Plutonium 238 Power our Space Exploration of the Future?

Solar energy is most likely as a base power source....and ion propulsion...

http://nmp.jpl.nasa.gov/ds1/tech/ionpropfaq.html

http://blogs.rsc.org/ee/2011/06/

We only have that pesky inverse square law to deal with.

Big, directable, focussable, orbiting mirrors?

Solar is good for 'close in' space projects, and projects where we can devote a good portion of launch mass to the solar cells. The ISS is the perfect case for solar, because we are keeping it close enough to keep working on it, and we can send more solar panels up at any time⁽¹⁾ to install for more power or to replace an aging or damaged unit.

Outer System missions, or interstellar/deep space probes, like V'ger⁽²⁾, will not have the launch mass available for the size of solar cells needed to run the vehicle out in The Black⁽³⁾, so nuclear batteries are the power source of choice for them.

Now for large manned vessels assembled in orbit⁽⁴⁾ and send out into the dark corners of space, there can be multiple options; Nuclear batteries to handle critical systems during the travel in the dark, solar cells to provide power for sensors and instruments when at the Object of Interest that caused the crew to be sent out.

Bottom line, there is no 'one size fits all' power source. They can all coexist⁽⁵⁾.

Notes:

1. Favorable launch window permitting, of course.
2. Sorry, VOYAGER, I grew up with Star Trek.
3. And picked up some lingo from Serenity/Firefly as well.
4. Earth or Lunar, they're both decent spots to build in.
5. Although anyone who suggests a coal- or oil-powered spaceship is just a lapdog for their Corporate Master. Those fuels, while TECHNICALLY possible, are completely non-feasible, consuming more resources and generating more pollution than they need to for the energy they could produce.
   

I have yet to see Montana, Idaho, Wyoming and most of new England.

Space missions aren't even on my radar.

Put 238 has many attractive attributes, but it is not readily available nor cheap to procure. The price is several thousand dollars per gram. Etimates vary since there is no active supply to create a market currently, but somewhere in the neighborhood of $4k to $8k per gram seems to be the general consensus.

At 1/2 watt thermal power per gram initially, that's $8M to $16M for a 1 KW heat source.

I guess it depends on your definition of 'economical'.

Well, if you pro-rate it out to 88 years, it costs about $24 per Kilowatt Hour.

I think you misplaced a couple zeroes. Also remember at 88 years it is only at 1/ 2 initial power.

I get $0.07 to $0.14 / kWhr. Which actually looks much more reasonable assuming it was actually used for 88 years....but also keeping in mind that is just the heat source.

I figure 88 years as 771408 hours. Mean power assuming an exponential decay to 0.5 KW is 0.72135 KW for a total KWh of 556455.161. So at $8M to $16M cost, I figure $14 to $28 per KWh.

Great! So that means with the current Ontario energy prices and retarded Green electricity pricing, it's a viable alternative for us here (but still too expensive for space).

It's being studied with high hopes!

It's being studied, with high hopes!

The calculation error was indeed mine....having solved for kWhr/$. Ooops

Pu238 has a price? I'll just nip down to Boots ànd buy a packet. Do they do lozenges or does it come as a powder in sachets?

Yes, even things that are not traded on an open market can have a realistic price.

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Now, please tell me more about the commerce occurring in footware. We also lack sachets in this neck of the woods.

So it would take 2000 grams to generate 1KW. At a density of about 20 g/cc, that's a volume of only 100 cc or a 4.7 cm cube.That would make a pretty tidy 1KW heat source, and the radiation is primarily alpha which is fairly easy to block.

An application which comes to mind: put some inside a Sterling motor. It would keep running for a lifetime! A neat desk toy for rich folks.

It depends, are we talking about manned or unmanned? There is a large power difference and Plutonium-238 powered Radioisotope thermoelectric generators of a few 100 watts are not going to be of much use to a manned mission.

Plutonium 238 and its decay products are all radioactive. Fine if you are just putting instruments into space but as soon as you put people into the picture you will need radiation shielding. That means extra weight. Given the amount of shielding required to make the astronauts safe, there would be too much weight to overcome gravity unless the ship was the size of the Starship Enterprise. So why would you not use warp drive?

Pu-238 decays almost exclusively by alpha emission. The shielding requirements are minimal.

Well obviously that's why the Enterprise is as big as it is, the warp drive is powered by 238 and the only person daft enough to approach it would be a Scotsman!

Turns out peat-smoke whiskey is a natural antidote.

No, how do you propel a thing in space by mere heat and radiation? Navigation on a vacuum needs impulse and momentum, while heat, can not. Radiation is more of heat energy than mass discharge emission.

Part of the derivation of force from momentum is d(mv)/dt = vdm/dt+mdv/dt.

The vdm/dt force is what you need to propel something in space.

Answers have been right on propulsion shortcomings.

Chiefly an alpha emitter so shielding not a big deal. Has even been considered for in-vitro use (pacemakers?). Not sure if any thing came of that.

This will do better in space, certainly.

Well there are betavoltaic devices out there...pretty expensive just now, but who knows in the future maybe cheap as li-ion batteries now...

http://www.gizmag.com/city-labs-nanotritium-betavoltaic-battery/23720/

https://engineering.purdue.edu/NE/Academics/Seminars/betavoltaic-technology

http://www.betavoltaic.co.uk/