Is the future of deep-space exploration at risk?

Dave Mosher is a science reporter who has written for Scientific American, Popular Mechanics, National Geographic News and He joins Hari Sreenivasan to discuss how a dwindling supply of plutonium threatens deep space exploration.


Dave Mosher is a science and technology correspondent for Business Insider who's written for National Geographic News and

Throughout his career, he's watched humans and robots launch into space, flown over the North Pole to catch a total solar eclipse, and toured a cutting-edge nuclear reactor.

He joins us now to discuss how a dwindling supply of Plutonium threatens deep-space exploration.

Plutonium is the fuel that's powered some of these satellites that we've gotten amazing pictures from, but what is Plutonium-238?

Plutonium-238 is a by-product of Cold War weapons production.

So when you're trying to make Plutonium-239, which is the active ingredient in a nuclear bomb, you can do a little side project and make this Plutonium-238.

And it doesn't react, doesn't work like Plutonium-239.

All it does, it just sits there, and it gets hot.

So if you can convert that heat into energy through its basic radiation, which you could stop with a piece of paper, then you can make a battery, and you can put it up in a spacecraft and, you know, take pictures and send them all the way back to Earth, hundreds of millions or even billions of miles away.

How long have these batteries lasted?

That is a great question.

So Voyager, the Voyager twins, solar system, that battery is still going after its launch in 1977, when it was fueled.

So 40 years, and it's still going to keep kicking.

I mean, the half-life of Plutonium-238 is about 88 years, just about, so, you know, you lose half of it, half of the energy over 88 years.

So it should still power that craft long into the future, and we're using all sorts of fun tricks and antenna gadgets that pick up that incredibly weak signal from the satellite, but it can last decades.

So how much more is left to put into the next wave of satellites, or do we use a different fuel now?

So, there was a report that came out, I think, in 2010, 2012, something like that, looking at all of the options, and what they came back to was Plutonium-238 is the only option basically, given all these problems that the other fuel sources, you know, chemical fuel cells and solar.

Your panels get too big.

Plutonium-238 is still the best option.

How much of it's left?

There is about 35, 36 pounds of this stuff left, 16 and some kilograms.

That's all earmarked for future missions.

NASA doesn't really have anything beyond that.

However, they have an arrangement with the Department of Energy, which, after more than 2 decades, started to create Plutonium-238 again.

So the end of the Cold War ends production.

Now we're trying to start it back up.

We don't have the same facilities, we don't have the same personnel.

It's sort of kind of a mystery.

How do you make this stuff?

So they've been spending years doing this, and I visited some of the facilities where they're trying to do this work.

How hard is it to make, or how much time or energy or money does it cost to make a couple of pounds of this stuff that could power a satellite?

So per gram, Plutonium can cost you tens of thousands of dollars, and that was, again, a by-product of the Cold War.

So now we're talking about a whole different story where we have to earmark some nuclear reactor time, stick some stuff in there, irradiate it, wait a year, filter it out, six more in, wait.

So it takes a lot of time to make this stuff, and you can refresh your existing supply since it's always the king.

But it's a game, and it can get very expensive.

NASA, there's a big political battle over this, but NASA now is paying the Department of Energy.

The government is paying itself to make this stuff, and it's in the tens-of-millions- of-dollars-per-year range, probably.

They should be up to $100 million or so if they really want to hit the targets that they're talking about in terms of production.

Do we have a lot more satellites in the queue waiting to take off and that we're putting this fuel into?

So, the satellite question is a good one.

It's one that NASA likes to deflect on.

They say, 'Oh, well, we've got all of our things, our ducks in a row.

We're fine. We're mapped out.

We're planning fine.'

But I've spoken to scientists who had dreams of sending spacecraft into outer space, to do really unique missions, land on the lakes of Titan, a moon around Saturn, or go back to Pluto and orbit Pluto instead of just flying by it.

You can't do those missions unless you can count on Plutonium-238, and right now, they're years behind schedule in producing this stuff.

They need to speed it up.

They need to figure out how to get more funding.

Something has got to give for these missions that scientists are dreaming up and putting a lot of work into to make happen.

So while NASA's script is, 'Oh, we've got, you know, a couple more missions planned, and by that time, we'll have a production timeline ready,' there's a whole bunch of missions nobody is ever talking about that aren't happening and probably should happen because we just don't have this resource available to us in the quantities that we need it.

All right. Dave Mosher.

Thanks so much for joining us.

My pleasure.

Thanks for having me.