Author Topic: A rebuttal to Jarrah's latest masterpiece  (Read 68191 times)

Offline ka9q

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Re: A rebuttal to Jarrah's latest masterpiece
« Reply #180 on: October 23, 2014, 06:37:18 AM »
Bob B. discusses that in his excellent article. The departure and return velocities were different but not by much; the bigger effect had to do with the different geomagnetic inclinations of the two trajectories. For Apollo 11, the return had a higher inclination so the dose was considerably less.

Offline Bryanpoprobson

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Re: A rebuttal to Jarrah's latest masterpiece
« Reply #181 on: October 23, 2014, 06:51:18 AM »
I had wondered about the angle, as the angle of the TLI was a combination of the tilt of the Earth and that the moon has a 5.1o of eccentricity with regard the plane of the ecliptic. So that angle must change over the course of the mission, especially for those of longer duration.
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Offline Bob B.

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Re: A rebuttal to Jarrah's latest masterpiece
« Reply #182 on: October 23, 2014, 01:26:35 PM »
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 31.383o and 39.925o 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 42o and 51o.  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).

« Last Edit: October 23, 2014, 01:40:50 PM by Bob B. »

Offline Bryanpoprobson

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Re: A rebuttal to Jarrah's latest masterpiece
« Reply #183 on: October 23, 2014, 01:55:24 PM »
Thank you Bob, a clear and concise answer. :)
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Offline smartcooky

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Re: A rebuttal to Jarrah's latest masterpiece
« Reply #184 on: October 23, 2014, 02:29:31 PM »
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).

Gee, that seems very late. Not a lot of time to do something about it if, for some reason, the separation didn't work as expected.
« Last Edit: October 23, 2014, 02:57:05 PM by smartcooky »
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Offline Bob B.

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Re: A rebuttal to Jarrah's latest masterpiece
« Reply #185 on: October 23, 2014, 03:22:37 PM »
I had wondered about the angle, as the angle of the TLI was a combination of the tilt of the Earth and that the moon has a 5.1o of eccentricity with regard the plane of the ecliptic. So that angle must change over the course of the mission, especially for those of longer duration.

The nodal precession of the Moon has a period of 18.6 years, so it's change is insignificant for a short duration mission.  During this 18.6-year period the Moon's inclination with respect to Earth's equator varies between 18.3o and 28.6o.  It was at its maximum around 1968-69.

Offline Allan F

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Re: A rebuttal to Jarrah's latest masterpiece
« Reply #186 on: October 23, 2014, 04:40:34 PM »
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).

Gee, that seems very late. Not a lot of time to do something about it if, for some reason, the separation didn't work as expected.

They had limited consumables in the CM - battery power and oxygen. And if the separation failed, I don't know what they would have been able to accomplish even if they had several hours on hand. Going EVA with their equipment would be a very last-ditch effort, since they only would have the two OPS at hand which could sustain two astronauts for 30 minutes. And all the connectors would be hidden between the CM and SM, not really reachable from outside.
Well, it is like this: The truth doesn't need insults. Insults are the refuge of a darkened mind, a mind that refuses to open and see. Foul language can't outcompete knowledge. And knowledge is the result of education. Education is the result of the wish to know more, not less.

Offline gwiz

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Re: A rebuttal to Jarrah's latest masterpiece
« Reply #187 on: October 25, 2014, 08:37:10 AM »
The first lunar radio ham payload is about to be launched...
The mission is now in progress and the radiation levels are reported to be as expected.
Multiple exclamation marks are a sure sign of a diseased mind - Terry Pratchett
...the ascent module ... took off like a rocket - Moon Man

Offline Bryanpoprobson

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Re: A rebuttal to Jarrah's latest masterpiece
« Reply #188 on: October 25, 2014, 04:37:06 PM »
I commented on the NVIDIA thread on youtube, basically to follow the thread using Google+. Is there a way, if you see a thread you want to follow on youtube, to follow the tread, without the need to comment? It's an effective method, but sometimes I feel like I'm just butting in to someone else's argument.
"Wise men speak because they have something to say!" "Fools speak, because they have to say something!" (Plato)