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Post by ka9q on Jul 23, 2010 16:40:02 GMT -4
What radiation? No, really, ask him what sorts of radiation they needed protection from Precisely. The layman often just doesn't realize that scientists and engineers apply that word to several very different things: particulate radiation, such as alpha, beta, proton, neutron and heavy ions; and electromagnetic radiation, such as visible light, infrared, ultraviolet. To further confuse things, gamma radiation is electromagnetic, not particulate (unless we want to start discussing wave-particle duality!) I've had to be careful about who's listening when I use that word in connection with radio signals or with heat transfer in a vacuum. Laymen, especially the many who suffer from radiation phobia, can get pretty worked up about it.
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Post by ka9q on Jul 23, 2010 13:16:59 GMT -4
I brought this up on another forum, and Frank O'Brien responded with an explanation that essentially boiled down to that secondary heat exchanger (the one intended to warm the suit gas circuit) just wasn't very effective at transferring heat.
If he's right, then it meant that the coolant would have had to get unacceptably warm before significant heat could have been transferred to the cabin and/or suit gas circuits to warm the astronauts.
Which, to me, raises the question of why even bother to have that second heat exchanger there. Under normal operating conditions there'd be a lot more waste heat from the electronics. The cabin would be at a comfortable temperature, and the heat transport section would only have to remove the astronauts' metabolic heat, not warm them up.
One way to make a heat exchanger more efficient is to change the fluid from air to water. The LM did provide cooled water for (two) astronauts' liquid cooling garments, which I take as tacit evidence that the heat exchanger used to cool the suit gas circuit (and cabin atmosphere) wasn't very effective either. The CSM cooled the astronauts only by cooling their suit gas, so it must have had a more efficient or effective gas/coolant heat exchanger.
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Post by ka9q on Jul 23, 2010 13:08:36 GMT -4
I don't know how much power was drawn by each LM system still running on Aquarius, but the total consumption in the powered-down state is given in the histories as 12-14 amps. If the batteries were at 29 volts, that's 348-406 watts.
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Post by ka9q on Jul 23, 2010 3:50:59 GMT -4
Interesting that they were all so close, despite the different inclinations of the CSM orbit (and latitudes of the landing sites). What was different about Apollo 16?
Did the LMs all fly minimum energy ascents, or did they perform doglegs to change inclination or RAAN?
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Post by ka9q on Jul 23, 2010 3:20:39 GMT -4
Were these systems outside the LM's pressure vessel? That would make it impossible to dump the heat back inside. I've studied the manuals for the heat transport section of the LM's environmental control system. There are two glycol/water coolant (essentially ordinary antifreeze, like you have in your car) loops, primary and secondary. The secondary loop was only used if the primary failed, so setting it aside, the primary coolant loop was as follows: Pumps; check valves; electronic equipment cold plate & suit gas heat exchanger (in parallel; the suit gas exchanger flow could be adjusted for comfort); liquid cooling garment heat exchanger; aft equipment bay cold plates; suit gas heater (also bypassable for temperature control); primary sublimator; ascent and descent battery cold rails; and back to the pumps. Obviously the order of these nodes is important, as each one will be warmer than the previous one until the coolant reaches the sublimator where it reaches its lowest temperature in the system. That the batteries immediately followed the sublimator says that the engineers wanted them colder than everything else. The relevant part for Apollo 13 is the suit gas heater. It comes right before the sublimator, so I don't see why it wasn't possible to simply shut off the sublimator water supply and dump all of the heat generated by every LM system right into the cabin to warm the crew. Running the sublimator (and consuming water) should have been necessary only if the crew became overheated (which didn't happen) or some subsystem (the batteries, perhaps?) had to be kept even colder than the crew. So I still don't understand this. My reference is the Apollo Operations Handbook, Lunar module LM 10 and subsequent, Volume 1, subsystems data. Since Aquarius was LM7, it's entirely possible that its heat transport system was not as documented here. Maybe the later LMs were reworked specifically because of Apollo 13's experience to permit warming the crew with waste heat without running the sublimator? Maybe the suit gas heater didn't even exist on LM7? I haven't yet found an earlier version of this reference that covers LM7. Perhaps this was covered by the recommendations of the Apollo 13 review board. That's another reference to check.
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Post by ka9q on Jul 23, 2010 2:47:36 GMT -4
It clearly shows all sorts......the ground is 'moving'.....and so is the flag, it is just bizzare and clearly something to do with the video. Keep in mind that Youtube compresses its videos VERY heavily. So when you consider everything that image has been through between the camera lens and your screen, it's pretty amazing that you can see anything at all... I would really like to see us return to the moon in my remaining lifetime, if for no other reason than to see it all over again but with modern high resolution digital cameras and transmission links. It would be a completely different experience. And it would be fun to watch the smoke come out of the conspiracists' ears as we watch the astronauts examine the artifacts at an Apollo landing site, showing the effects of nearly a human lifetime of unfiltered solar UV and extreme temperature cycling.
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Post by ka9q on Jul 22, 2010 5:47:00 GMT -4
Has anyone read my note? Just a friendly ping...
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Post by ka9q on Jul 21, 2010 22:54:02 GMT -4
The explosion wasn't QUITE as dramatic as shown in the film Apollo 13, though they did feel it. Yeah. Neither were the attitude excursions during the manually controlled burn quite as violent as depicted. One thing they apparently depicted right, or maybe even less violently than the real thing, was S-IC/S-II staging. Looking at the Saturn V flight reports for these missions you can easily see that the acceleration compressed the stack, and S-IC shutdown excited a longitudinal mode - essentially the stack oscillated like an accordion for a second or two, with the accelerometers showing both negative and positive longitudinal g-force peaks. The movie "Apollo 13" simply showed them being thrown forward into their straps rather than being thrown back and forth a few times. I did get the opportunity to ask two Saturn V veterans - Bill Anders and Alan Bean - about this and they both thought the Apollo 13 depiction was more or less accurate.
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Post by ka9q on Jul 21, 2010 22:47:26 GMT -4
Does it include combat losses? Or just accidents?
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Post by ka9q on Jul 21, 2010 15:10:22 GMT -4
Any thoughts (Jay?) on this cooling/heating issue on Apollo 13? Why couldn't the waste heat from the LM electronics (which are mostly in the aft equipment bay, as Jay points out) have been dumped into the cabin to keep the astronauts warm instead of being dumped overboard by the sublimator, consuming precious water while the astronauts froze?
It looks to me that the LM cooling system should have been able to do this. In normal operation the sublimator would be needed to dump excess heat from the electronics and crew, but in the powered-down mode it should have been possible to shut it down whenever the crew cabin was too cold.
What am I missing?
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Post by ka9q on Jul 21, 2010 14:53:06 GMT -4
I finally watched this, a little apprehensive because of Colbert's usual style. I half expected him to spend most of the interview challenging Bean to prove that he really went to the moon. And frankly, I'm tired of seeing these personal heroes of mine mistreated in public. But this went pretty well. Colbert was remarkably respectful, the 'hoax' didn't even come up, and Bean and the audience seemed to enjoy it.
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Post by ka9q on Jul 21, 2010 14:19:12 GMT -4
The early Apollo landing missions all landed near the equator, so the CSM/LM went into near equatorial orbital planes and there wasn't much worry about the problem you speak of. The later missions landed at moderately greater latitudes (Apollo 15 was the highest at 26 N) so the CSM typically made a plane change the day before the LM ascent stage left the moon. You'll see them listed in the mission events list of a typical mission report.
I haven't really studied perturbations in lunar orbits so I don't know the extent to which they could be used to help change the CSM's orbit to match lunar rotation (and thus minimize the fuel in a plane change). I do know that the perturbations quickly changed the eccentricity (the main reason lunar orbits are so unstable and short lived) and the CSM also had to make allowances for that effect in the longer missions.
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Post by ka9q on Jul 21, 2010 12:50:48 GMT -4
Very impressive. Was it good enough for a landing or reentry? Wouldn't it become harder as the body's relative size gets bigger? Lovell's observations of stars against the limbs ("edges") of the earth and moon were good enough to generate state vectors that exactly matched those produced by Houston from radio tracking data. This meant that yes, they could have landed on Earth with them. Apollo 8 had no lunar module. I don't know if they could have landed on the moon with one using only their own observations. Lovell was CMP, which meant that on a regular Apollo flight he was only responsible for CSM navigation. The ground could produce radio-based orbital solutions much more quickly than the crew. During the first few landings this was vital after descent orbit insertion to ensure that the orbit would not intersect the moon (i.e., they wouldn't crash before powered descent initiation). They had to determine the LM's orbit ASAP after AOS (the burn was done on the far side) so the crew could still do an emergency wave-off burn if the pericynthion was dangerously low. A similar risk presented itself after lunar orbit insertion (the initial arrival at the moon) but was greatly alleviated by breaking the burn into two components. The first put the CSM+LM into an elliptical orbit, and the second circularized the orbit. This made the first burn far less critical and eliminated the risk of a slight overburn that would have them crashing on the near side a half orbit after LOI.
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Post by ka9q on Jul 21, 2010 12:24:43 GMT -4
I don't think Collins' suit was completely lacking in thermal protection, but it didn't have the many layers of thermal protection that Armstrong and Aldrin had in their suits.
Inside the command module cabin, when they were hooked up to its environmental control system, they were cooled by oxygen gas flow. This was sufficient since they were only dissipating heat at their basal metabolic rate (i.e., they were resting).
On the moon, Armstrong and Aldrin were exerting themselves much more heavily, and gas cooling would have been insufficient. So they wore an inner suit consisting of small water tubes, and their PLSS backpacks pumped cooling water through this inner suit to keep them from getting overheated. When they were in the lunar module, the LM environmental control system also supplied cooling water, just like the PLSS.
All this was necessary because the pressure suit itself contained excellent thermal insulation that more or less completely blocked any loss of metabolic heat from passing through the suit. So it had to be removed by other means, which during an Apollo EVA means the evaporation of water into a vacuum. Their backpacks contained a water tank for this purpose, and in the lunar module they also had a water evaporator to get rid of both metabolic and equipment heat.
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Post by ka9q on Jul 21, 2010 9:09:00 GMT -4
Note that starting with A15, the CMPs had two sets of gas connectors just like the LM crew. This was for their deep space EVAs during the trip home when they recovered film cassettes from the SIM bay instruments in the service module. One set of gas connectors was connected to the umbilical, just as the surface crew connected theirs to the PLSS, and the other set was connected to the OPS and a purge valve, again just as the surface crew had done.
With the switch to the AL7B suit, the connectors on both the CMP and lunar EVA suits were rearranged to allow the new waist joints to function.
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