Feasibility study of a mission to Sedna – Nuclear propulsion and solar sailing

This direct fusion drive is a really interesting concept. Maybe something like this could be used for interstellar travel in a century (or five), it is very encouraging that there is active research on it. ~5kg of thrust is not a lot, but over time...

This sounds significantly more feasible than nuclear pulse propulsion ("project orion" style) which I used to think was the only feasible approach to get to another star.

One thing that was unclear from the paper to me: How does the fusion drive "pick" D/He3 fusion over D/D? Can this be "forced" by just cranking the plasma temperature way up? Or do you still just have to deal with a bunch of neutrons from undesired D/D fusion?

> This sounds significantly more feasible than nuclear pulse propulsion ("project orion" style) which I used to think was the only feasible approach to get to another star.

I still carry a torch for project Orion, it's impossible to not love.

* Feasible 50 years ago, not 50 years from now.

* No ultra lightweight fancy space age materials, steel and lots of it.

* Seriously, lots of it, let's launch a battleship to to Mars,

* or Jupiter,

* or Alpha Centauri.

* Gives everyone something way better to do with all those nuclear bombs they have laying around.

I once spoke to Freeman Dyson at a book signing and asked him if Orion would work. He said he thought it would. And I asked him if it should be launched. He said probably not (IIRC due to the amount of radiation that would be put into the atmosphere).

It is almost the epitome of steampunk romance. Launch an entire mid-20th century city and economy into space! And it might even work!

But, yeah, you probably don't want to be launching these routinely. People generally badly underestimate the number of nuclear explosions that have been set off on Earth and overestimate the badness of nuclear explosions. Putting one or two of these into orbit might be justifiable. It's certainly not a bad emergency plan to have in your pocket in case of emergencies. But you still certainly wouldn't want an entire industry routinely lighting these things off.

Still... the romance of it all...!

While the Orion drive indeed works perfectly fine in atmosphere - or actually even better than in vacuum - no one says you need to launch them from the ground.

While it would be preferable due to the immense weight, you can either lift it by conventional means or possibly build it from local resources in the long run.

Once in space Orion is much less problematic & might be even easier to dock and maintain than normal nuclear thermal rockets, where the unshielded reactor will just put out insane amounts or radiation in all directions outside of its shadow shield.

Correctly engineered pusher plate should be much easier to deal with.

Having to lift them via some other means first eats away almost all their advantage.

However I believe your point holds more generally for nuclear-based space propulsion. That we fear "NUKULAR!" by about two to three orders of magnitude more than is justified has kept us from having halfway decent space travel for at least a good two decades, most likely. There are a number of nuclear propulsion mechanisms that would make things like going to Mars halfway feasible instead of flights of fancy, or doing science missions in months instead of years or even decades, but people hear that you're thinking of lifting nuclear material into space and all rationality goes flying out the launch window. Nuclear is so bad that it basically reaches out through outright magic and guarantees explosions and there's no conceivable amount of preparation that could be done in people's minds to prevent the evil radiation!!!!1! from escaping and eating people's puppies.

The funny thing is that even so quite a bit of nuclear material has been lifted into space, but hearing that doesn't make people go "oh, well, maybe it's less dangerous than I thought".

I mean, I know this isn't the safest stuff in the world but I sure hope all that anti-nuclear propaganda in the 20th century actually did help prevent nuclear war because it has certainly had massively negative impacts in energy generation, environmental damage, space exploration, and who knows what else.