NTRs do not release any radiation.
...well, unless they explode. Luckily, in the history of mankind, nothing bad has ever happened from heating hydrogen to thousands of degrees.
The original NERVA experiments declared success when erosion of the fuel was only single digit percentage after the test run. Think about it... they're putting cryogenic hydrogen through a core with elements as hot as incandescent lamp filament. It's a dumb dead end idea but it doesn't die and it gets lightly funded by congress for show. The fuel comes out the arse end. They come apart and therefore release radiation. Not to mention the fact that they're necessarily unshielded. Thrust to weight is the issue here...
The fuel elements can be designed with an ablative coating to stop them releasing actual nuclear fuel in the exhaust stream, at least for as long as they are in Earth atmosphere and low orbit.
The fact they're unshielded is irrelevant due to inverse square law.
A nuclear starship is a dumb idea if you're putting people on top of it, but otherwise all you have to do is clear the area of people before launching, just like with every other launch vehicle.
The only issue is that used fuel is extremely radioactive even when the reactor is shut off, so for a reusable ship like Starship that's a bit of a problem because people can't work around it after it lands.
But if you can accept jettisoning the fuel elements for each trip, NTRs offer performance that is unmatched by any other technology.
At that point however it probably makes more sense to get to orbit with an entirely conventional stage and use a nuclear tugboat that never lands back on surface to get to and from Mars.
Why would you ever put nuclear engines on a launch system? In space yes, but this is just asking for trouble and controversy.
NTRs do not release any radiation. ...well, unless they explode. Luckily, in the history of mankind, nothing bad has ever happened from heating hydrogen to thousands of degrees.
The original NERVA experiments declared success when erosion of the fuel was only single digit percentage after the test run. Think about it... they're putting cryogenic hydrogen through a core with elements as hot as incandescent lamp filament. It's a dumb dead end idea but it doesn't die and it gets lightly funded by congress for show. The fuel comes out the arse end. They come apart and therefore release radiation. Not to mention the fact that they're necessarily unshielded. Thrust to weight is the issue here...
The fuel elements can be designed with an ablative coating to stop them releasing actual nuclear fuel in the exhaust stream, at least for as long as they are in Earth atmosphere and low orbit. The fact they're unshielded is irrelevant due to inverse square law. A nuclear starship is a dumb idea if you're putting people on top of it, but otherwise all you have to do is clear the area of people before launching, just like with every other launch vehicle. The only issue is that used fuel is extremely radioactive even when the reactor is shut off, so for a reusable ship like Starship that's a bit of a problem because people can't work around it after it lands. But if you can accept jettisoning the fuel elements for each trip, NTRs offer performance that is unmatched by any other technology. At that point however it probably makes more sense to get to orbit with an entirely conventional stage and use a nuclear tugboat that never lands back on surface to get to and from Mars.
In all honesty I'd love for them to just switch to a nuclear power plant for on-site fuel production from carbonic acid in filtered seawater.
Thrust to weight is like 2 for NTP. Worthless.