[FLvoter]

That makes sense that some regions of the belts are less intense and that they change, dissipate and reform over time. But its said Apollo 11 was planned so as to go around the these more intense areas. So why cant they do that know? (They literally say they can’t accomplish it now). Also, I don’t understand what the duration of today’s missions have to do with it since no mission would spend any longer time in the belts than necessary.

[chimera]

Maybe what they mean is that nobody has translunar capability any longer so we are stuck with Earth orbit missions. Those can either be below or above the Van Allen regions. If you need to go further out you can if you keep the time within the intense zones limited, which reduces total dose accumulated. If there is no reason to go way out there then you can do what you need to do in a low orbit, below the intense regions. Personnel on the ISS for example are planned to be there a long time and it would be unwise to have orbited the ISS within any of the stronger Van Allen zones.

If manned spaceflight beyond Earth orbit is ever resumed I'm sure the trajectories need to get them where they need to go will be planned to avoid the intense radiation regions, as was done for Apollo. That combined with the velocity required for Earth gravity escape (transit time through whatever radiation fields are present will be minimized by faster transit time) will keep exposures fairly low.