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kryton
2007-Apr-02, 03:44 PM
The Apollo landings all occured during the first quarter phases of the moon.




Apollo 11 landing July 20, 1969 - first quarter
Apollo 12 landing Nov 19 1969 - first quarter
Apollo 14 landing Feb 5 1971 - first quarter
Apollo 15 landing July 30 1971 - first quarter
Apollo 16 landing April 20 1972 - first quarter
Apollo 17 landing Dec 11 1972 - first quarter


Recent studies from the NOAA confirm that killer electrons approaching the speed of light (capable of disabling spacecrafts) travel the magnetosphere which extends past the moon. Did Apollo purposely travel to the moon during the first quarter phases to limit or avoid the magnetotail? Did they purposely pick this phase because the earth is perpendicular to the moon and sun at this phase to reduce the tractive forces? Since the gravitational forces of the moon and sun would be greater at other phases. Or was it for moon temperature reasons? For future space travel to the moon will they most likely follow this same formula?

captain swoop
2007-Apr-02, 03:48 PM
they went for temperature reasons.

killer electrons?

Jason Thompson
2007-Apr-02, 04:33 PM
Apollo 12 and 14 landed quite a bit past first quarter pahse, and Apollo 11 and 17 landed when the Moon was a waxing crescent.

Landing times were selected so that the landing sites were just past sunrise at the time of the landing.

Paul Beardsley
2007-Apr-02, 04:54 PM
killer electrons?
Didn't one of those leave a dent in Jim Lovell's helmet? :D

jrkeller
2007-Apr-02, 06:02 PM
Or was it for moon temperature reasons? For future space travel to the moon will they most likely follow this same formula?

I suspect that future lunar bases will land at lunar dawn so that they have as much daylight to assemble everything before the 14 days of night commence.

Swift
2007-Apr-02, 06:09 PM
I suspect that future lunar bases will land at lunar dawn so that they have as much daylight to assemble everything before the 14 days of night commence.
And you never can trust the night shift to assemble anything correctly. :D

Laguna
2007-Apr-02, 06:27 PM
Didn't one of those leave a dent in Jim Lovell's helmet? :D
Yep!
Boy, I hate those killer electrons emitted by my CRT at 0.3c.
Last time one of those electrons left a crack in it.

BertL
2007-Apr-02, 07:32 PM
NASA actually uses killer electrons on HBs that find out a bit too much. Killer electrons were used to make Jarrah White's computer crash, too.

JayUtah
2007-Apr-02, 07:48 PM
What do you feed a killer electron? Killer neutrinos?

Tog
2007-Apr-02, 08:15 PM
Peeps (http://www.justborn.com/products/peeps.html), oddly enough.

Hey, somethin's gotta eat 'em.

Swift
2007-Apr-02, 09:53 PM
Wouldn't Killer Electrons be a great name for a band?

Gillianren
2007-Apr-02, 10:21 PM
Wouldn't Killer Electrons be a great name for a band?

My Gods, you're right!

I blame Dave Barry for how often I have just that sort of thought.

kryton
2007-Apr-02, 10:24 PM
This was from Goddard News - NASA. Any intelligent responses?

Jason Thompson
2007-Apr-02, 10:32 PM
Yes, the first two, which explained that a) the phase of the Moon was selected for temperature and illumination reasons, and b) the Moon was not in first quarter phase for at least four of the landings, contrary to your assertion in the first post. Care to respond to that?

kryton
2007-Apr-02, 11:29 PM
First Quarters July 22 1969 - 9:44 P.M.
Nov. 16 1969 - 10:45 A.M.
Feb. 2 1971 - 9:30 A.M.
July 30 1971 - 7:07 A.M.
April 20 1972 - 7:45 A.M.
Dec 13 1972 - 1:36 P.M.

All first quarter. Location Miami, Florida. Darn close, I would say.

Jason Thompson
2007-Apr-02, 11:47 PM
Not really. Certainly not close enough to suggest any significance. In one day the terminator moves about 13 degrees, which corresponds to the Moon itself moving about 13 degrees along its orbit. That's a significant deviation from 'perpendicular'.

kryton
2007-Apr-03, 12:04 AM
By perpendicular, I meant to convey as the moon being 90 degrees from the Sun/Earth axis. In this first quarter phase scenario, the gravitational forces would be less than at other phases.
The affects of these killer electrons in the magnetotail would be lessoned also while landing during or around this first quarter phase.

JayUtah
2007-Apr-03, 12:54 AM
By perpendicular, I meant to convey as the moon being 90 degrees from the Sun/Earth axis.

I think we all understand what you mean by that. Unfortunately the moon still moves 13 degrees each day along its orbit. In a 10- to 12-day Apollo mission, the moon will have moved 130-160 degrees, or about one-third to one-half revolution, along its orbit. Which precise instant in the mission do you claim is significant for your perpendicularity claim and why?

The affects of these killer electrons in the magnetotail would be lessoned also while landing during or around this first quarter phase.

What makes you think so-called killer electrons were a concern for the Apollo missions?

kryton
2007-Apr-03, 01:36 AM
During the landings. Was minimizing the gravitational forces (during first quarter phase) even a concern during the landings? The Goddard News article stated they were a concern for spacecrafts. That's why they coined them killer electrons. And because the sun has always been here.

JustAFriend
2007-Apr-03, 02:05 AM
Simple explanations are always the best:

The landing were timed so that the pilots could have the best view and contrast of the surface they were coming up on!

A high overhead sun would wash out the surface making eyeball altitude estimations useless. ('ya gotta have eyeball-backups in case the radar glitches)

JayUtah
2007-Apr-03, 02:11 AM
During the landings.

Again, even if you confine the period to the lunar surface sojourn in each case, the moon travels a significant distance along its orbit. How close to perpendicular is "close enough" and why?

Was minimizing the gravitational forces (during first quarter phase) even a concern during the landings?

There were orbital mechanics concerns that involved gravity, but they did not have anything to do with avoiding killer electrons. Mission timing was dictated primarily by desired insolation at the landing site.

The Goddard News article stated they were a concern for spacecrafts.

All spacecraft? Of every kind? Sent on every kind of mission? How is an Apollo spacecraft different from, for example, a GPS satellite?

That's why they coined them killer electrons.

How many spacecraft have been deployed since 1959? Do you have a number? How many spacecraft are currently in some kind of orbit? Do you have a number? Of either of these, how many have been adversely affected by killer electrons? Do you have a number?

Jason Thompson
2007-Apr-03, 09:23 AM
By perpendicular, I meant to convey as the moon being 90 degrees from the Sun/Earth axis.

Thank you, we all know what perpendicular means.


In this first quarter phase senerio, the gravitational forces would be less than at other phases.

But, as has already been pointed out, the Moon was not at first quarter for any of the landings, and wasn't even close to it for four of them. Apollo 14 landed three days after first quarter. That means that during the landing the Moon was almost 40 degrees from perpendicular!

The reason for the landings being timed as they were is well documented and very simple: they wanted the Sun to be just above the horizon as seen from the site in order to provide illumination with long shadows, to maximise the ability of the astronauts to see the surface features, and to have the lunar surface temperatures reasonably low.

Irishman
2007-Apr-03, 09:47 PM
Recent studies from NOAA? Got a cite?

How much variation in gravity are you expecting there to be, and why do you think it relevante? Consider, does Earth's gravity fluctuate to any measurable degree depending upon the phase of the Moon? Why would it be different on the Moon?

From Goddard News, NASA? Got a cite?

JayUtah
2007-Apr-03, 10:17 PM
http://www.gsfc.nasa.gov/goddardnews/20030912/solarwind.html

kryton
2007-Apr-03, 10:18 PM
www.gsfc.nasa.gov/topstory/2003/0904magwaves.html

I guess it is a few years old about killer electrons but expected most of you had already been privy to this info. Being around the moon during the first phases as the Apollo landings were, I was also wondering if this was to avoid the magnetotail and the possible encounter of these killer electrons within.

The gravitational forces during other phases are measurable as they result in tides. So at this first quarter phase of these Apollo landings the gravitational forces would be weaker than some other phases of the moon. Being that there were so many unknowns I was wondering if this was a consideration as being the safest time of the lunar cycle.

JayUtah
2007-Apr-03, 10:27 PM
I guess it is a few years old about killer electrons but expected most of you had already been privy to this info.

Privy, no. Aware of it, yes. It was published in the relevant scientific journals and discussed in the industry. Additional shielding was installed on the ISS to attenuate high-energy electrons, but generally there has been no additional concern for spacefarers. Many conspiracists try to make this discovery sound like an Earth-shattering revelation that space radiation is far more dangerous than we've known about. It simply isn't.

I was also wondering if this was to avoid the magnetotail and the possible encounter of these killer electrons within.

No, it wasn't. Are you satisfied with the explanations given for Apollo mission synchronization to the lunar cycle?

Donnie B.
2007-Apr-03, 10:53 PM
The gravitational forces during other phases are measurable as they result in tides. So at this first quarter phase of these Apollo landings the gravitational forces would be weaker than some other phases of the moon. I'm not following you. What gravitational forces do you think would be weaker at first quarter?

If you're referring to the fact that tides on Earth are lower at first and last quarter than at full or new moon, that would have an insignificant effect on a spacecraft in lunar orbit or making a landing or ascent. Tides on the Moon are theoretically somewhat stronger than on Earth, but because the Moon is solid it exhibits little deformation in response to tides. In no way would tides even need to be taken into account during the lunar landings, any more than they would affect splashdown on Earth at the end of the mission.

Far more significant to the Apollo missions were the Moon's mascons (mass concentrations) that made the spacecraft orbits less stable than they would have been if the Moon were a homogenous sphere. Mascons are in fixed locations, however, so their effect is not related to the phase of the Moon.

That's why I ask you what gravitational forces you're talking about. Can you please explain more clearly?

kryton
2007-Apr-03, 10:56 PM
Did Apollo have this additional shielding or was this just an oversite in building the ISS? The magnetotail extends past the moon.

Van Rijn
2007-Apr-03, 10:59 PM
Did Apollo have this additional shielding or was this just an oversite in building the ISS? The magnetotail extends past the moon.

The primary issue with ISS is exposure time. Apollo astronauts spent little time in space, so required minimal shielding. ISS astronauts are in space long term, so require additional shielding to reduce total exposure.

kryton
2007-Apr-03, 11:02 PM
Thanks Donnie B. It may sound silly but that was my question. Thank you

JayUtah
2007-Apr-03, 11:15 PM
Did Apollo have this additional shielding...

No. It was not needed for Apollo because Apollo traversed the Van Allen belts instead of orbiting inside them. Apollo was also a short-duration mission.

...or was this just an oversite in building the ISS?

Not an oversight. The ISS was modified to account for a phenomenon that was not known when it was designed. So-called killer electrons are a recent discovery.

The magnetotail extends past the moon.

But killer electrons do not.

kryton
2007-Apr-03, 11:20 PM
In an Apollo mission of 10-12 days means the Apollo spacecrafts were in space for 70-86 days though not traveling at high speeds all the time. If these killer electrons travel close to the speed of light shielding would still be needed.

JayUtah
2007-Apr-03, 11:28 PM
In an Apollo mission of 10-12 days means they were in space Apollo spacecrafts were in space for 70-86 days...

Over a three-year period. No matter how you stack or slice it, Apollo astronauts were not in space long enough for many of the comparatively rare cosmic events to be a credible hazard.

If these killer electrons travel close to the speed of light shielding would still be needed.

Killer electrons occur in low Earth orbit. Apollo spacecraft spent only a few hours of each mission in that zone. The ISS spends all its time there and is thus more susceptible to high-energy electrons. In terms of Van Allen belt radiation, Earth orbit is a far more dangerous place than cislunar space.

What are you trying to say? You asked first if Apollo mission profiles were adjusted to minimize the effect of killer electrons. Now you're suggesting that Apollo spacecraft were insufficiently shielded. What exactly is your question or assertion?

Maksutov
2007-Apr-04, 01:40 AM
they went for temperature reasons.

killer electrons?The FDA recently approved the use of killer electrons to irradiate killer tomatoes.

Former Vice President Dan Quayle was the guest-of-honor at the opening of the first plant to use this new technology for food preservation, and was presented with the first tomatoe to be irradiated with the innovative process.

kryton
2007-Apr-04, 03:47 AM
The killer electrons enter in the magnetotail at the point called the magnetic reconnection. This reconnection point was confirmed to be close to the moon by Wind as it past around the moon. At this point these electrons were traveling at 100s KM/s.

cjl
2007-Apr-04, 04:02 AM
And an electron at 100's of km/s has about as much kinetic energy as a typical BB traveling at a rate of 6 inches per year

JayUtah
2007-Apr-04, 04:20 AM
At this point these electrons were traveling at 100s KM/s.

And how many electron volts does that equate to? Since killer electrons are those with energies in the millions or tens of millions of electron volts, do such electrons still qualify as killer?

What is the flux of killer electrons in the magnetic reconnection zone of the magnetotail?

And I repeat my request that you state your question or proposition directly.

Van Rijn
2007-Apr-04, 08:59 AM
In an Apollo mission of 10-12 days means they were in space Apollo spacecrafts were in space for 70-86 days though not traveling at high speeds all the time. If these killer electrons travel close to the speed of light shielding would still be needed.

You mean 70-86 days for all missions together? That's not relevant to individual radiation exposure. A mission of 12 days means that astronauts on that flight were in space for 12 days. An astronaut on ISS can be in space for more than 180 days. All other things being equal (same shielding, same radiation environment), cumulative exposure would be 15 times greater for the longer mission time. There are some differences in radiation issues for ISS and Apollo, but longer exposure time always requires more shielding to keep doses at reasonable levels.

Van Rijn
2007-Apr-04, 09:04 AM
And I repeat my request that you state your question or proposition directly.

I agree. kryton, are you proposing a moon hoax or other space related conspiracy theory with these issues? If you just have space related questions, you could ask them in the Q&A section.

Jason Thompson
2007-Apr-04, 09:45 AM
In an Apollo mission of 10-12 days means they were in space Apollo spacecrafts were in space for 70-86 days though not traveling at high speeds all the time.

No, that means that one spacecraft with one crew was in space for 10-12 days, so radiation exposure refwers only to that spacecraft and crew. Cumulative exposure only applies to individuals, not a whole group in which a few individuals expose themselves at different times.

Jim
2007-Apr-04, 01:03 PM
Maybe - maybe - kryton is looking at this in terms of the "single bullet" theory. That is, all it takes is one hit to be fatal.

If so, then over all Apollo flights you have 70-86 days of exposure. Well times 3 to get a total man-days exposure time.

Kryton, can you confirm this? Also, as JayUtah and Van Rijn have previously asked, can you please explain why you brought this up?

(I hate that "killer" electron tag. But, "tomatoe"? Priceless.)

Jason Thompson
2007-Apr-04, 01:17 PM
Maybe - maybe - kryton is looking at this in terms of the "single bullet" theory. That is, all it takes is one hit to be fatal.

Which is a flawed theory because it is only fatal if you get hit in the right place. I can take one bullet through my brain and die, or twenty bullets in my legs and arms and survive.


If so, then over all Apollo flights you have 70-86 days of exposure. Well times 3 to get a total man-days exposure time.

I'm still not convinced that's valid. Every 10-12 days you have a new spacecraft and a new crew. Each mission is independent. The cumulative time in space idea seems to me to be similar to those poor misguided fools who pick the same lottery numbers every time on the grounds that their numbers 'must' come up sooner or later: their odds of winning are the same every week because one draw does not affect the outcome of the next. Same with Apollo: one flight does not affect the risks of the next. Apollo 17 is no more risky because it came at the end of the 86 hours in space for Apollo.

JayUtah
2007-Apr-04, 02:31 PM
I can take one bullet through my brain and die, or twenty bullets in my legs and arms and survive.

We call this the Bruce Willis Effect.

Same with Apollo: one flight does not affect the risks of the next. Apollo 17 is no more risky because it came at the end of the 86 hours in space for Apollo.

That is true. But if the probability of some event is p, the probability of N trials without the event occuring is (1-p)N. So the more missions you fly, the more likely you are to have an event on some mission. That's how mission planners have to think about it. Your N can refer to hours or days in a single mission too, so if the probability of some event occuring is p in a single day, then the equation above gives the probability of going N days without it happening.

But if you're an astronaut trying to select which mission to apply for, it doesn't matter for those uncontrollable events which mission you select. If each mission is independently and equally likely to undergo some event, choosing a later one versus an earlier one won't make a difference.

A single killer electron doesn't do anything. You wouldn't even say ow. The danger, as with all radiation, is in how much you accumulate.

Jim
2007-Apr-04, 03:22 PM
Please note, I am not advocating the Single Bullet Theory, just asking kryton if that is his thinking.

Jason Thompson
2007-Apr-04, 03:29 PM
But if the probability of some event is p, the probability of N trials without the event occuring is (1-p)N. So the more missions you fly, the more likely you are to have an event on some mission.

Good point well made.

Irishman
2007-Apr-04, 04:22 PM
Thanks for the links. Helps me know what is being discussed.

It appears to me that "killer" is a misleading appellation. It suggests to you that the electrons are dangerous to the crew members, perhaps at the individual level (i.e. one electron can do in an astronaut). This is an erroneous understanding.

"Killer" as used in this article applies to what happens to satellites that get hit by a stream of these electrons. Electronics don't like high energy electron strikes.


When electrons become this energetic, they can penetrate to the interior of spacecraft. Once inside electronic parts, they build up static electricity that can short circuit a critical part or put the spacecraft into a bad operating mode.

Not quite the same thing as baking an astronaut.

Also, it doesn't appear that the waves or the high-speed electrons are the discovery. Rather, it is the cause of the waves being linked to the Sun. So the "danger" isn't new, just a better understanding of where it comes from.

Now, how does all this relate to Apollo?

And if you wonder about astronaut exposures, what about Gemini? Or Shuttle? Shuttle missions ran 14 to 16 days long, in low Earth orbit. That means passing through the lower reaches of the Van Allen belts every orbit. Why does the Moon seem worse to you? Apollo missions went through the main belts fairly quickly, and only orbited Earth for short durations (a few hours).


kryton said:
The gravitational forces during other phases are measurable as they result in tides. So at this first quarter phase of these Apollo landings the gravitational forces would be weaker than some other phases of the moon. Being that there were so many unknowns I was wondering if this was a consideration as being the safest time of the lunar cycle.

Okay, I wondered if you were thinking of tides. We're talking about two different kinds of effects. The gravitational force is typically understood to be the magnitude of the pull due to gravity. While there is a fluctuation because the Moon varies in distance, that is tiny and insignificant, and dwarfed by the variation in Earth's gravity due to elevation and the effect of centrifugal force from Earth's rotation.

Tides are what is called a second order term. Tidal stress is due to differential pulling on one side of an object with respect to the other side of the object. We simplify gravity calculations as a pull on center of mass, but in reality gravity is distributed across the whole mass. The distribution of pull means the surface of Earth closest to the moon is pulled more (because it's significantly closer) than the surface farther away. Tides only are significant for large items, like planets and moons and asteroids. Things as small as mountains and buildings have tidal stresses that are practically immeasurable. If a mountain is unaffected between peak and base by tides, the effects on something tiny like people is even less significant.

Furthermore, while the tides on Earth are affected by the phase of the Moon, the tides on the Moon are not. This is because the Moon is in synchronous rotation - the same face of the Moon faces Earth at all times (with a minor wobble). So while the Earth tidally stresses the Moon, that tide does not flow around the surface of the Moon the way tides do on Earth. There's almost no fluctuation in tide on the Moon. There would be no reasonable way to conceive of lunar phase affecting lunar landing from gravity or tidal concerns.

So, have your questions been answered satisfactorily?

JayUtah
2007-Apr-04, 06:21 PM
It appears to me that "killer" is a misleading appellation. It suggests to you that the electrons are dangerous to the crew members, perhaps at the individual level (i.e. one electron can do in an astronaut). This is an erroneous understanding.

Agreed, but high-energy electrons still have a biological effect. One so-called killer electron will not harm an astronaut in the least. It is only by accumulating the effects of many, many such collisions that an astronaut begins to suffer biologically. HDPE shielding was installed in the ISS sleeping quarters to mitigate the biological effects of electrons.

Electronics don't like high energy electron strikes.

Correct. High-energy electrons are called killer because they "kill" spacecraft electronics, not people.

Also, it doesn't appear that the waves or the high-speed electrons are the discovery.

They are not the discovery most recently reported by NASA/Goddard. The existence of high-energy electrons in LEO was discovered almost ten years ago, whereupon ISS modifications were undertaken. Only comparatively recently has the cause behind them been identified.

We engineers don't strictly need to know the cause. A short-term solution simply requires knowing the nature of the particle and the flux-energy profile. From that we can estimate the whole-body biological effect on organisms and the electrostatic or ionization effects on equipment and propose an effective shielding or safing regimen.

Gillianren
2007-Apr-04, 08:58 PM
Please note, I am not advocating the Single Bullet Theory, just asking kryton if that is his thinking.

I would, but I'm not allowed here. I'm certainly more likely to believe it than in an electron that leaves a dent in someone's helmet.

kryton
2007-Apr-04, 11:18 PM
Yes, I was trying to be as clear as possible. I was referring to killer electrons in the magnetotail which extends past the moon and their affects on spacecrafts alone. As an article I was reading referred to a number of 100 spacecrafts have been lost ( I assume only satellites) due to killer electrons. I was thinking it would have been less risky to travel to and land on the moon during and around the first quarter phase and be clear of the magnetotail and if this is how they would do it in the future.

JayUtah
2007-Apr-04, 11:36 PM
The magnetotail extends to beyond the moon, but killer electrons do not. The electrons in the far reaches of the magnetotail are of insignificant energy.

Count Zero
2007-Apr-05, 01:30 AM
The cumulative time in space idea seems to me to be similar to those poor misguided fools who pick the same lottery numbers every time on the grounds that their numbers 'must' come up sooner or later: their odds of winning are the same every week because one draw does not affect the outcome of the next. Same with Apollo: one flight does not affect the risks of the next.

Here's an example:
When you flip a coin, you have a 50% chance of getting "heads". You can therefore calculate that the odds of getting "head" twice in two flips is 25%, and getting it in three out of three flips is 12.5%.

You flip the coin and get "heads". What are the odds of getting heads on your next flip? From the above calculations, you might say 25%, but you would be wrong. Nothing has changed about the coin to make the odds of coming up heads any less than 50%.

You flip it again and it comes up "heads". On your third flip, the odds are still 50%, not 12.5%. The coin doesn't care what the last flip was.

Jason Thompson
2007-Apr-05, 08:33 AM
I was thinking it would have been less risky to travel to and land on the moon during and around the first quarter phase and be clear of the magnetotail and if this is how they would do it in the future.

How many more times do we have to point out that the landing times had nothing to do with radiation or gravity? They quite possibly will do that in future for landings, but not for those reasons.

The Apollo landing times were determined by the following criteria:

- The site had to be sunlit.

- The solar elevation at the landing site had to be low to maximise the casting of shadows by the surface features.

- The site had to remain in sunlight for the duration of the lunar stay.

- The site would preferably be some time away from attaining the peak lunar surface temperature.

Those criteria give shortly after sunrise at the landing site as the best time to land. The landing sites were to be on the near side, as communication with the far side required relay satellites that added an unacceptable level of complication. That places all landings between new and full moon, with the complications of libration zones ruling out the limb areas. That narrows your time frame to around a week, during which the Moon goes from a thick waxing crescent through first quarter on to a waxing gibbous phase. And what do you know, that's when they all took place. It's just time, temperature and lighting considerations that determined the landings for Apollo. Nothing to do with gravity or the magnetotail.

Not that it could have been anyway. The 'killer electron' discovery was made well after Apollo.

Further, future landings won't be considering avoiding the magnetotail because it would be pointless in terms of the intended mission duration. Apollo went for a couple of days maximum. The planned future missions will last a lot longer than that and absolutely will be passing through the magnetotail.

Irishman
2007-Apr-05, 11:05 PM
I guess I'm still confused about this "magnetotail". I didn't see that word in the linked article, and am not sure what it means. How does it relate to the magnetosphere?

JayUtah
2007-Apr-05, 11:39 PM
The magnetotail is the elongation of the magnetosphere on the night side of Earth.