Space travel without combustion or nuclear power. (Thought experiment/discussion.)

[Maria Sirona]

How about RTGs? They use no fusion or fission as far as i know

[Rakaydos]

Just now, Maria Sirona said:

How about RTGs? They use no fusion or fission as far as i know

RTGs are fission, technically. it takes a refined nuclear material and lets it just sit there, glowing, and turn "natural" radioactivity into heat, and then into power. But that's still fission.

[NFUN]

1 hour ago, Rakaydos said:

RTGs are fission, technically. it takes a refined nuclear material and lets it just sit there, glowing, and turn "natural" radioactivity into heat, and then into power. But that's still fission.

I wouldn't say radioactive decay is fission

[kerbiloid]

Just now, NFUN said:

I wouldn't say radioactive decay is fission

Why? The neutrons fly from it with such "fisssssss!!!"

***

But radioactive sail is one of known low-thrust engines.

[Rakaydos]

6 minutes ago, NFUN said:

I wouldn't say radioactive decay is fission

...it literally is.

[NFUN]

25 minutes ago, Rakaydos said:

...it literally is.

I don't know what the Official Definition is or where to get it, but every single definition I can find distinguishes alpha decay (the relevant decay for RTGs AFAIK) from nuclear fission, and beta and gamma decays are undeniably not fission events.

[tater]

Sort of semantic. If one of the daughter particles is a He nucleus (alpha), it doesn't usually get called fission, even though it is splitting into 2 daughter particles lowering the atomic number of the parent.

[kerbiloid]

fusion: 1+1=2

fission: 2=1+1

[Hyperspace Industries]

Rtg’s, in my opinion, should be allowed, while it wouldn’t be easy for someone to get permission to use one, it would be a bit less impossible than launching a nuclear reactor into the sky.  

Also, you could build an rtg thermal rocket.

[magnemoe]

12 hours ago, Hyperspace Industries said:

Rtg’s, in my opinion, should be allowed, while it wouldn’t be easy for someone to get permission to use one, it would be a bit less impossible than launching a nuclear reactor into the sky.  

Also, you could build an rtg thermal rocket.

Why not go for an solar powered ion drive for higher trust and ISP? 
Yes technically you could make an high ISP RTG thermal rocket using stuff with an so short half life it was glowing white. 
Who might be more insane than nuclear salt water engines who again make orion pulse nuclear look very reasonable. 
Fallout from this thing if it failed would make Chernobyl an joke. 

[Hyperspace Industries]

14 hours ago, magnemoe said:

Why not go for an solar powered ion drive for higher trust and ISP? 
Yes technically you could make an high ISP RTG thermal rocket using stuff with an so short half life it was glowing white. 
Who might be more insane than nuclear salt water engines who again make orion pulse nuclear look very reasonable. 
Fallout from this thing if it failed would make Chernobyl an joke. 

Alright, well, I’ve read around, and there are plans for gamma ray rtg rockets.  

Citation:

https://patents.google.com/patent/US3306045A/en?q=Radioisotope+rocket&oq=Radioisotope+rocket