NASA successfully tests portable nuclear reactor for crewed missions to Mars

[mbrowne5061]

Yeah I got the image of like old school water wheels, like from the back of boats, tons of surface area to catch as much material as possible. Nuclear or sometime type of oxygen burner system ( pulling oxygen down from the atmosphere) to create energy would be the best solution.

There is literally more oxygen in the ground on Mars than there is in the atmosphere. Even then - ignoring that Oxygen is just the catalyst to an energy releasing reaction, and not a fuel source itself - why 'burn' your rocket fuel and air supply in order to power your base, generate more air, and generate more rocket fuel (also ignoring the obvious compounding inefficiencies in that)?

For reference, this XKCD strip does actually drive the point home about energy densities:
https://xkcd.com/1162/
The other fuels he compares Uranium to all depend on a reaction with oxygen to release their energy. Uranium does not. In this light, Uranium becomes the obvious power choice for large scale or long-duration space flight and planetary missions.

Out of curiosity, if this was on a rockets payload and the rocket goes boom on the launchpad, or part way up to orbit (As so happens every now and then), would this not possibly send pieces of uranium over a large area?

The Uranium does get spread over a large area, but its only a kilo or two in space craft design - not the several hundred in a concentrated area in commercial design. Still not ideal or desirable, but not as bad. For this reason, payloads requiring a nuclear component are heavily reviewed through all stages from concept to launch by the DOE, DOD, EPA, and even some UN organizations for the 'extra special' payloads.

We have launched nuclear reactors before, both the voyagers were powered by a nuclear reactors that ran off plutonium 238. There is always going to be a risk, but these are relatively small reactors, not a lot of uranium and the uranium may not actually separate in the explosion (dense stuff) so nothing really spreads.

Don't forget Curiosity and New Horizons. They have nukes too, don't know what isotopes off the top of my head though.

 

[wiyosaya]

Yeah I got the image of like old school water wheels, like from the back of boats, tons of surface area to catch as much material as possible. Nuclear or sometime type of oxygen burner system ( pulling oxygen down from the atmosphere) to create energy would be the best solution.

I would be more concerned about erosion from the dust storms.

 

[m3tavision]

And to boot Thorium reactors are cooler operating temperatures, longer lasting and we have an abundance of it at the Paducah KY plant. Sounds like the same old political game playing that got us into uranium reactors decades ago. Besides, 10 years isn't so long on another planet .... how on earth will they refuel it and what to do with the waste? Start another Superfund project on another planet! Sheeeezzzzeeeeee

The article says that it uses solid sodium heat pipes to cool the core and transfer the energy to sterling engines. This is far from a Fukushima, Chernobyl, or Three Mile Island type plant.

Higher temperatures mean higher thermal efficiency by the Carnot equation:

1 - (Tout/Tin)

I would put odds on the fact that the people who designed this are among the best and most knowledgeable nuclear engineers in the world and know full well the hazards of U235 based reactors. The article says that the heat then drives a highly efficient Sterling Engine. From Wikipedia:

A Stirling engine is a heat engine that operates by cyclic compression and expansion of air or other gas (the working fluid) at different temperatures, such that there is a net conversion of heat energy to mechanical work. More specifically, the Stirling engine is a closed-cycle regenerative heat engine with a permanently gaseous working fluid. Closed-cycle, in this context, means a thermodynamic system in which the working fluid is permanently contained within the system, and regenerative describes the use of a specific type of internal heat exchanger and thermal store, known as the regenerator. Strictly speaking, the inclusion of the regenerator is what differentiates a Stirling engine from other closed cycle hot air engines.

https://en.wikipedia.org/wiki/Stirling_engine

My bet is that they considered the possibility of using Thorium, however, U235 was better due to the requirements with respect to the environments where it might be used. The article also says that the team threw everything they could at it and it withstood the tests. That is not to say that they could not have missed something, but it sounds like they did everything they thought of to make it fail and it refused to do so.

The problem with U235 reactors so far is that they are subject to loss of coolant - in most cases - liquid water. With a solid sodium heat pipe coolant system, loss of coolant sounds like it is far less likely to occur.

If the coolant were water, I would also be saying WTF, but this sounds, to me anyway, like it might be as far beyond liquid cooled U235 reactors as ion propulsion is beyond chemical rocket engines.

Deep space is near absolute zero... the pipes are throttled/exposed to deep space if a certain thermal threshold is reach/maintained. No need for liquid if they leave them in orbit and beam down the energy. Safer too.

 

[IAMTHESTIG]

This is seriously a fascinating discussion... but I think we have to ask ourselves the most important question of all. Will it blend?

 

[Kibaruk]

How about we drop NASA and based on all the expertise in energy and reactors there are in this forum we put some astronauts on mars by next year?

 

[DelJo63]

IMO, the science in ANY mars mission has more to do with getting grant money and saving jobs than any proposition or personal theory's on anything to be found or the benefits to those on Earth.

Consider this radical though:

without a mission to fly, WHY would we need NASA?

 

[Abraka]

Next generation Tesla cars will use this reactor instead of a battery!

 

[Knot Schure]

And to boot Thorium reactors are cooler operating temperatures, longer lasting and we have an abundance of it at the Paducah KY plant. Sounds like the same old political game playing that got us into uranium reactors decades ago. Besides, 10 years isn't so long on another planet .... how on earth will they refuel it and what to do with the waste? Start another Superfund project on another planet! Sheeeezzzzeeeeee

I hope you don't take offense, but I think I'd trust NASA to make the best choice for their project, than you.

Unless you are going to tell me you are both a nuclear scientist, and with an extensive background on this topic, and in which case I'd ask you to explain your opposition to their plan in more detail.

 

[mbrowne5061]

Deep space is near absolute zero... the pipes are throttled/exposed to deep space if a certain thermal threshold is reach/maintained. No need for liquid if they leave them in orbit and beam down the energy. Safer too.

Space is also a near vacuum, making it about as ideal of an insulator as can exist in nature. Anything facing an energy source will heat up, and anything facing 'the black' will cool down, based purely on what it can receive or transmit on a radiative-basis.

Energy 'beaming' via microwaves (presumably) presents it's own issues with massive inefficiencies, and without any really added safety or reliability benefits in this case.

IMO, the science in ANY mars mission has more to do with getting grant money and saving jobs than any proposition or personal theory's on anything to be found or the benefits to those on Earth.

Consider this radical though:

The original space race put a massive number of people to work. Saying "what has space ever done for me", is like taking issue with an airplane because only the pilot gets to fly it. Never mind all the passengers, just remember all the work it took to design and build it, plus all the work it takes to operate and maintain it. A regular commercial spaceflight industry would put hundreds of thousands of people to work across all skill sets and levels.