Mission to Neptune

[Tormod]

Originally Posted by BlameTheEx

In the end it all comes down to budget. Do we want to go all out for regular missions to the outer planets, or are the occasional opportunities where planets are in position for gravity assisted boosts sufficient? More important, will the funding be available?

There is a deeper meaning in this question which is very important. Good call.

[BlameTheEx]

Originally Posted by Tormod

SMART-1 uses xenon gas and solar electricity. Will ion drives for outer planet research require nuclear power?

Not necessarily. Most of the boost can be applied while the craft is still within the orbit of the inner planets - where solar power is the better option. The remainder can be a mixture of gravity assisted boosts, and a little conventional rocket power - the same as always. Then again, the solar power assembly used for the initial boost can still be used once it gets Jupiter. It will just provide far less power. Perhaps still enough for manoeuvring with a lower velocity ion drive, and powering instruments.

Originally Posted by Tormod

Why is there a question about this - is it a matter of funding? Safety?

Yes, and yes, but also I see problems in development.

You are not comparing like with like. Casini used radioisotope thermoelectric generators. These were a good choice for powering the instruments - given that solar power was not a viable alternative at the time. The demand was for 600-700 watts. While RTG's are viable for powering instruments it is not suggested that they are valid for powering ion drives. The power requirement for the JIMO is pencilled in at about 100,000 watts. Current RTG's would be far too heavy for such a task. If nuclear power is to be used for ion drives, it will be a totally new technology. The plans are for a fission powered generator.

There is a real difference. Cassini used 3 RTG's, and if more power had been needed more RTG's could have been added. If a RTG had failed, it would be no great problem - there is redundancy. For the JIMO project there will be and can only be one fusion power source. One huge source of heat that must be dissipated. It is heat dissipation that will be the problem. Presumably there will be a large array of delicate cooling fins connected by heat pipes. I would like you to consider the development and deployment of this array. Can it be launched as a unit? If not, can it be assembled in space? How can it be made reliable? Leaks due to meteorite damage, mechanical stress during launch, thermal stress during operation, or radiation damage are all possible. So are blockages.

There is plenty of information on ion drive development, and it's all going well. There is plenty of information on lightweight fission generators for space, and again it seems no great problem. Plenty of studies have been made. But for cooling - Where are the contracts for research and development? Where are the estimates of the cooling assembly's weight? All I have seen is an artists impression of what the cooling fins will look like.

Originally Posted by Stargazer

I think most national space programmes are underfunded, whether NASA, ESA or Russia. I think we as a species are using our time and resources on lots of useless and wasteful things. Exploring space is not one of them :-)

But do you think that this underfunding will end in the near future? If so, and you are proved right, I will look right foolish, but frankly pigs would fly. NASA must learn to live with the funding politicians supply, not the funding that they promise. As for funding outside the USA - who is even promising such budgets?

[Stargazer]

Originally Posted by BlameTheEx

But do you think that this underfunding will end in the near future? If so, and you are proved right, I will look right foolish, but frankly pigs would fly. NASA must learn to live with the funding politicians supply, not the funding that they promise. As for funding outside the USA - who is even promising such budgets?

No, I suspect that it wont end anytime soon. I have no idea what it will take to have the people in charge realise how important it is. Maybe we should start relying on the private sector for space colonisation.

[BlameTheEx]

Originally Posted by Stargazer

No, I suspect that it wont end anytime soon. I have no idea what it will take to have the people in charge realise how important it is. Maybe we should start relying on the private sector for space colonisation.

What can I do but agree? But is the private sector going to be interested in fusion? Right now there is lots of private sector involvement in space, but it is 100% solar powered. There are no private concerns planing missions to the outer planets for commercial gain in the near future. Not at least private concerns that have that sort of money. Could you offer a business plan that would attract investors? If NASA is to rely on developments from the private sector it can only go for solar power - because that is what private industry IS developing.

[Tormod]

Blame, I think your posts here are very good. Thanks.

[Stargazer]

Originally Posted by BlameTheEx

What can I do but agree? But is the private sector going to be interested in fusion? Right now there is lots of private sector involvement in space, but it is 100% solar powered. There are no private concerns planing missions to the outer planets for commercial gain in the near future. Not at least private concerns that have that sort of money. Could you offer a business plan that would attract investors? If NASA is to rely on developments from the private sector it can only go for solar power - because that is what private industry IS developing.

I didn't meant to say that NASA would wait for the private sector to develop things, I meant that the space colonisation could very well be done by the private sector. I think they will have to take small steps out in space. Virgin Galactic and Bigelow Aerospace are great examples of this, where they will achieve suborbit and LEO for tourists and probably companies and research institutions to rent modules in Bigelow's space station for example. Then pretty soon I predict the time is ready for spaceships that can go around the moon for a short cruise, and then after a while there will be bases on the surface of the moon. All this time they will move around in the inner solar system, where nuclear fission is not necessary for most purposes. And regarding the Prometheus project, NASA is working together with private companies to develop the reactor, as they have with the other projects.

[BlameTheEx]

Originally Posted by Stargazer

And regarding the Prometheus project, NASA is working together with private companies to develop the reactor, as they have with the other projects.

What exactly do you mean here?

It would be no new thing for NASA to pay private companies for research. Nor will it surprise me that private industry has made useful developments that can be applied to space. Always we take what we already know and then using it as a base for development. Are you suggesting that private industry IS directly funding development of fusion power specifically for space? I doubt it. NASA will have to pay the vast bulk of any project to adapt our knowledge of earth bound reactors for application in space.

[Stargazer]

Originally Posted by BlameTheEx

What exactly do you mean here?

It would be no new thing for NASA to pay private companies for research. Nor will it surprise me that private industry has made useful developments that can be applied to space. Always we take what we already know and then using it as a base for development. Are you suggesting that private industry IS directly funding development of fusion power specifically for space? I doubt it. NASA will have to pay the vast bulk of any project to adapt our knowledge of earth bound reactors for application in space.

No, you did say "If NASA is to rely on developments from the private sector it can only go for solar power - because that is what private industry IS developing." so I thought I'd point out that the private industry will develop this reactor for NASA, not that the private sector necessarily develops a reactor on their own, that NASA could use as they're sitting around waiting for someone to develop it.