Just a question:- HB's always talk about going out through the belts and how the Apollo Astronauts would get fried. I have yet to see any of them mention the fact that the Astronauts had to return too. I may just of missed it though.
Jarrah mentions this in his video and doubles his one-way computation to account for it. Of course he just assumes the return trajectory was a mirror image, he doesn't do anything to verify that.
Does anyone know the comparisons in escape velocity speed and return speed and time spent in the belts? The return speed would no doubt been at a greater velocity.
Ka9q has already answered this but I'd like to add to it. The numbers I'm about to give are for Apollo 11. I have not done the computations for other missions, though they are surely similar. The amount of time spent in the belts was much less on the return trip, but this was only slightly due to a higher velocity. For instance, if we compare the velocities at an altitude of 1000 km, the outbound and return trips were 10,333 m/s and 10,355 m/s respectively. The big difference was in the inclinations. The orbital inclinations of the outbound and return trips were 31.383
o and 39.925
o respectively. These angles are in respect to the geographic equator. In 1969 the difference between the geographic and geomagnetic equators was a little over 11 degrees. Apollo 11 flew in a direction that took full advantage of this difference, obtaining near maximum separation between the spacecraft and the geomagnetic equator. The inclinations with respect to the geomagnetic equator were about 42
o and 51
o. Since the return trip was farther away from the geomagnetic equator, the fluxes were significantly lower. Furthermore, the radiation belts do not extend outward as far at that latitude, so Apollo 11 could traverse them in less time. The total time spent in the belts was about 219 minutes on the outbound trip and 147 minutes on the return trip (this is to the far outer edge where the flux drops to zero). Taking into account the lower flux and the shorter duration, the dose that an unprotect astronaut would receive was about 5 times greater on the outbound trip vs. the return trip.
Most of the outer belt radiation comes from electrons, and these were completely blocked by the spacecraft hull. The only real concern was protons with energies above about 100 MeV, as these were the only particles with enough energy to actually penetrate the hull. The only time these high-energy protons were encountered was when Apollo skimmed by the inner proton belt. Apollo was in this danger zone for only a matter of minutes; about 8 minutes on the outbound trip and about 4 minutes on the return trip.
Also, where, in relation to the VAB's did the CM SM separate?
On Apollo 11 the SM separated at GET 194:49:12.7. This was at an altitude of about 3300 km and about 14 minutes prior to atmospheric entry. Obviously most of the VAB had already been traversed by the time of separation. However, separation did occur prior to the 4-minute period when Apollo 11 was exposed to the greatest threat from high-energy protons (which was about 10 to 6 minutes prior to entry).
