Nuclear Propulsion in Space
Why Hacker News recommends it
HN people link it as an old-timey explainer for nuclear thermal propulsion, and as evidence these engines were already built and tested.
What it is
A 1968 NASA film from the US National Archives explaining why the US needed a nuclear rocket and how the engine works. It also shows combined nuclear and chemical stages for a manned Mars mission.
Recommended by 2 HN commenters across 2 different months, 2018 to 2020.
What Hacker News said
Recommends wizardforhire · 2018-06 · on “The Tyranny of the Rocket Equation (2012)”
aerospikes There’s a lot of reason why they haven’t been used yet, but I think most the compelling argument against them is that they won’t be used until fuel costs become the competitive factor in launch prices. [LINK] [LINK] Nuclear rockets are quite the concept but have their obvious limitations. This video is worth checking out if you haven’t seen it yet. [this video]
Recommends cwojno · 2020-10 · on “New nuclear engine concept could help realize 3-month trips to Mars”
This article didn't explain it at all, so you're right to ask. tl;dr: Gaseous propellant (I'm guessing hydrogen) is heated with fission then pointed in the opposite direction of intended travel. The uranium in this design is not a propellant, but a heat source. Aside: you can use photons/heat as a propellant, but it's thrust is very low [LINK] . Ideal propellants typically have a high exit velocity and low mass. That gives you the longest amount of "burn" time, and the greatest amount of control for the weight. [LINK] Back in the day when the US was building more of these nuclear rockets, the propellant of choice was typically hydrogen [LINK] . Old timey video explaining it [this video] . I'm ass
Cites inamberclad · 2019-09 · on “NASA Wants to Send Nuclear Rockets to the Moon and Mars”
It's much more likely to look like NERVA than Orion. [LINK] These types of engines have already been run: [this video]
Cites stqism · 2020-06 · on “The US military is getting serious about nuclear thermal propulsion”
I don’t know if any real rockets were built, but according to this old video we’d see a reduction of weight due to the absence of heavy chemical fuel. [this video]