# Would nuclear fusion ever be practical for marine propulsion? **URL:** \ **Category:** Factual Questions\ **Created:** [June 27, 2026, 7:22pm UTC](https://boards.straightdope.com/t/would-nuclear-fusion-ever-be-practical-for-marine-propulsion/1031233 "2026-06-27T19:22:03Z")\ **Posts on this page:** 6\ **Page:** 2
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [June 30, 2026, 12:46pm UTC](https://boards.straightdope.com/t/would-nuclear-fusion-ever-be-practical-for-marine-propulsion/1031233/21 "2026-06-30T12:46:11Z")
Well, yes, that’s the point. Could you keep a star running for an indefinite future if you could keep pumping the accumulating helium out and fresh hydrogen in? My take is that separating the helium out would be the hard part. It’s formed in a vast region; it’s not like there’s a simple cloud of nearly pure helium [here], while over [there] is where the pure hydrogen sits. Yes, over a long time the helium slowly collects in greater concentration towards the center. Maybe just stick your pipe in there at dead center and pull out a helium-enriched mix of whatever all’s down there. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [June 30, 2026, 1:19pm UTC](https://boards.straightdope.com/t/would-nuclear-fusion-ever-be-practical-for-marine-propulsion/1031233/22 "2026-06-30T13:19:01Z")
No need for a Sun sized star. Just build a red dwarf. Say a third the mass of the sun. Those things will run forever. Long enough that the current age of the universe will be a mere infantile memory before they reach old age. Trillions, not billions of years. ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [June 30, 2026, 1:24pm UTC](https://boards.straightdope.com/t/would-nuclear-fusion-ever-be-practical-for-marine-propulsion/1031233/23 "2026-06-30T13:24:13Z")
> [@LSLGuy](#): > > Maybe just stick your pipe in there at dead center and pull out a helium-enriched mix of whatever all’s down there. Not in a red dwarf; they have convection currents such that they don’t run out of hydrogen until it’s virtually all fused. That’s part of why they live so long (the other part is that they burn dimmer). ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [June 30, 2026, 2:04pm UTC](https://boards.straightdope.com/t/would-nuclear-fusion-ever-be-practical-for-marine-propulsion/1031233/24 "2026-06-30T14:04:04Z")
> [@puzzlegal](#): > > Well, a friend in the Princeton physics department once said he believes the only practical way to contain nuclear fusion is with gravity. That reactor won’t fit on any ship. That’s when you build a [stellar engine](https://en.wikipedia.org/wiki/Stellar_engine) and take your whole star system with you. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [June 30, 2026, 2:40pm UTC](https://boards.straightdope.com/t/would-nuclear-fusion-ever-be-practical-for-marine-propulsion/1031233/25 "2026-06-30T14:40:18Z")
> [@Francis\_Vaughan](#): > > No need for a Sun sized star. Just build a red dwarf. … I think the word “just” is doing all the heavy lifting in there. Like about 1E30 kg’s worth. I got a chuckle. Well done! ---
**Author:** ![Marvin\_the\_Martian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/marvin_the_martian/32/2898_2.png) [@Marvin\_the\_Martian](https://boards.straightdope.com/u/Marvin_the_Martian)\ **Post date:** [June 30, 2026, 9:13pm UTC](https://boards.straightdope.com/t/would-nuclear-fusion-ever-be-practical-for-marine-propulsion/1031233/26 "2026-06-30T21:13:12Z")
> [@Ancient\_Nerd](#): > > > [@EdwardFound](#): > > > > clouds of hydrogen gas massive enough to sustain fusion by gravitational pressure > > That would be a star. So we build our own star. How do we access its energy? We could use something like photovoltaic panels to capture light from that star and convert it to electricity. Or we could let it heat up the atmosphere and cause wind, then build generators to convert that wind to electricity. Wait a minute… [Previous page](https://boards.straightdope.com/t/would-nuclear-fusion-ever-be-practical-for-marine-propulsion/1031233.md?page=1)