A while ago, I ran the numbers for Apollo 11's trajectory using Robert Braeunig's numbers ( www.braeunig.us...
) and an
areal density of 7~8 g/cm^2 for the Apollo spacecraft. I used Spenvis to calculate the expected dose, using a 2-body approximation of Apollo 11's
outbound trajectory over half the mission duration (lunar gravity not accounted for, so it just lingers out in cis-lunar space for the simulation,
with no shielding from the moon itself).
The result was less than a rad of expected radiation. Not dangerous at all, even if you double it for a full mission duration with a return leg (and
again, not accounting for any shielding the moon itself may provide while in lunar orbit). Here's a diagram showing a slice view of Apollo's
I compared this to the trajectory of Orion EFT-1's 3600 mile orbit. In the video you posted OP he says "we need to learn more about this region of
space before we send people through it." Well here is the expected dose if you were to send Apollo astronauts in an Apollo command module on the same
trajectory as Orion EFT-1's final orbit:
Nearly 30 rads of radiation, almost entirely from trapped proton radiation in the inner Van Allen Belt. It's not lethal, but at that dose you are
approaching the threshold at which you may start to exhibit mild symptoms of radiation poisoning according to the CDC:
"Mild symptoms may be observed with doses as low as 0.3 Gy or 30 rads."
Still won't kill you, but it might just make you sick if you fly Orion EFT-1's trajectory with the older Apollo capsule. Obviously that's not
desirable, and it's also not the same region of space covered by Apollo. Quite literally you can not safely pass through the region of space traversed
by Orion EFT-1 using the older Apollo capsules. Apollo took an inclined trajectory to the moon and did not pass directly through the most intense
region of the inner Van Allen belt. Orion basically did just that and deliberately passed through the most intense region.
In fact (almost certainly by design), Orion's trajectory placed it near the edge of the South Atlantic Anomaly, an area of higher radiation where the
Van Allen Belt dips lower than normal, as it crossed the 1000 km mark to enter the edge of the inner Van Allen belt. Here's a screenshot from Brent
Boshart's satellite tracker showing where Orion EFT-1 was as it crossed the 1000 km altitude mark:
. Given a peak altitude of 3600 miles or about 5800 km, it basically stayed within the inner
belt from that time until it came screaming back down towards re-entry in the Pacific. Wiki lists the inner Van Allen belt limits at 1000 km to 6000
). The wiki for EFT-1 also lists this period at 1000 km near the SAA as being the
first of two of the highest radiation periods during the mission (en.wikipedia.org...
In any case, manned Apollo flights obviously did not use this kind of "worst case scenario" trajectory which spends an entire orbit lingering in the
inner Van Allen Belt, and transiting into it near the SAA at the worst possible location. EFT-1 was partly to test the radiation resilience of the new
Orion capsule. Its computer systems are vulnerable to "bit flips" and memory upsets in ways that the core rope memory of the old Apollo Guidance
Computer would not have been.
edit on 23-8-2016 by ngchunter because: (no reason given)