India Mulls Using Nuclear Power For Its Chandrayaan-2 Mission To the Moon

MarkWhittington writes: India is preparing its second mission to the moon, the Chandrayaan-2, as Space Insider noted. The mission will consist or an orbiter, a lander, and a rover. It will be launched on an Indian-built Geosynchronous Satellite Launch Vehicle (GSLV) in late 2017 or early 2018. Defense Daily reported that officials at the Indian Space Research Organization are mulling making the lunar mission nuclear powered, presumably with plutonium-fueled radioisotope thermoelectric generators (RTGs). RTGs use the heat of the decaying fuel to create electricity. Both the American and the Soviet space programs have used RTGs in their various spacecraft, the most recent one being the New Horizons space probe that recently flew past Pluto.

Comments

238Pu?

[Rei]

Does India actually have a stockpile of 238Pu? If not then where are they supposed to get it in two years? It's not like the world is awash in the stuff, and it takes time to set up a program and make it.

Honestly, Chandrayaan-2 is only a near-Earth mission, and not a super-long one - they don't need a long half-life element like 238Pu. Dirt-cheap 90Sr probably makes more sense, it's a widely available waste product. Or if India really wanted to impress the world, they'd make an actual nuclear reactor for space missions, not just an RTG, and offer to make them for sale to other countries. Russia made a few of them near the end of the Cold War (TOPAZ), but it's anything but off-the-shelf technology today. Another option to do something actually noteworthy would be to make a stirling RTG and leave on the moon, racking up operational hours in a space environment to demonstrate its reliability. A flight-tested stirling RTG would also be something that the west doesn't have.

Re:238Pu?

[Sique]

RTGs have been mass produced in the former Soviet Union since the 1960ies, and they were often used as power source in beacons in uninhabited regions - now often in a detoriated state, partly plundered and dismantled. There are estimates of about 1000 devices being deployed, and many of them in undocumented places.

Re:238Pu?

[Rei]

Yes, 90Sr RTGs. Which is why I said it's much more suitable. It's cheap (by nuclear standards) and abundant - it's a waste product, not a manufactured product like 238Pu.

Re:238Pu?

[Rei]

That is, of course, not how 238Pu is made. Neutron bombardment of uranium yields far too much 240Pu mixed in with the 238Pu**, and it's too much cost and difficulty to separate them. Instead, it's made by first taking nuclear waste and isolating the 237Np from it, which makes up only a very small fraction, so you have to process a lot. You then expose the relatively pure 237Np to a heavy neutron flux (which is expensive, as neutron flux is valuable), very slowly converting it to 238Pu via 238Np. You then regularly have to extract out either the 238Np, 238Pu, or both. It's an expensive process. 238Pu is a manufactured product, not a waste product.

** Uranium is mainly 233U, 235U, and 238U. We'll ignore 233U because it's so far away from 238Pu for now, and we'll ignore fissions, which are very unlikely to lead to Pu. 238U captures to 239U, which quickly decays to 239Np. This captures up to 240Np, which decays to 240Pu. 235U captures to 236U, which has too long of a half-live to be relevant. It captures to 237U. This can then either capture up to 238U (leading most likely to more 240Pu), or decay to 237Np. This then gives us the above route to 238Pu. But the longer series of bombardment chains needed, the comparative rarity of 235U to 238U in most reactors, and the cross sections involved, usually mean that under 2% of plutonium in nuclear waste is 238Pu.

Moon orbit - why?

[spiritplumber]

We're still at 1AU or thereabouts, isn't it better to use solar panels and save the non-renewable Pu for past-Mars-orbit missions where solar panels won't work?

Re:Moon orbit - why?

[nojayuk]

The Sun isn't visible on any given point on the Lunar surface for two weeks every month and it gets cold at "night". An RTG-powered lander and rover can stay operational in such circumstances and the excess heat from the RTG can stop the electronics, motors, batteries etc. from freezing up and failing. The solar-only solution would require lots and lots of PV panels plus enough battery storage to, at the minimum, warm the lander/rover and prevent damage to the instruments and systems. That's a lot of extra mass to carry compared to a small RTG that can provide power and heat.

erg

[sociocapitalist]

And the fallout from one of these exploding in the air would be...?

Re:Congratulations, dev. nations. West.. not so mu

[Coren22]

I can't think of a reason to use RTGs for moon exploration. The weight of solar panels and batteries for a probe would be less than an RTG at this distance from the sun. There is a reason the ISS uses solar for power, and it isn't irrational fear. There is a reason New Horizons used an RTG, it was the better option at that distance from the sun.