Newbie
Since October 19, 2002, a very persistent and very anonymous HB has posted
THIS "Apollo FAQ"
in various astronomy-related newsgroups.
The same content has been posted as separate parts in various newsgroups since, at least, August 25, 2002.
In order to see Jim Oberg respond to yet another of this persons countless postings, click HERE.
<font size=-1>[ This Message was edited by: Lunatic on 2002-11-03 19:02 ]</font>
Established Member
I think I'll pass. Where would one begin debunking this Grade-A ignoramus?
Established Member
I didn't have time to read the whole page. I had to wax my ear hair.
Newbie
Lucky you, John, still to HAVE ear hairs ! MY ear hairs self-ignited, where I heard Bill Kaysing´s voice on the FOX show ......
<font size=-1>[ This Message was edited by: Lunatic on 2002-11-03 20:18 ]</font>
Order of Kilopi
The criticisms and refutations by authors
such as David Percy, Ralph Rene, the late James Collier, Bill Ka[y]sing and others take the form of analysis of the photographic
record and video footage shot by NASA astronauts and questions about the viability of other aspects of the operation such as
the flight worthiness of the lunar module (LM) and the radiation risk ...
David Percy (filmmaker), Ralph Rene (carpenter), James Collier (journalist), and Bill Kaysing (librarian) generally do not have the technical expertise to comment on the spaceworthiness of spacecraft and the effects of astrophyisical phenomenon. David Percy, as a professional photographer, is the only one even remotely qualified to discuss Apollo video and photography, but we find that Mr. Percy has little or no skill at photographic interpretation and analysis, which are different fields than photography. Other expert photographers and photo analysts strongly disagree with Mr. Percy's findings and methods.
I would remind the reader that It's up to scientists and claimants of this or that fact to provide proof of their claims.
Agreed. However, the standards which prevail in historical research must be applied to questions of Apollo's historical authenticity. Conspiracy theorists wish to set a higher standard for Apollo defenders. They do not accept a burden of proof themselves.
That's how it works in science. It's called the scientific method.
No. The scientific method entails presenting a falsifiable conclusion -- that is, a conclusion which can be, on the basis of evidence, determined to be true or false. Instead, the conspiracy theorists present a conclusion which cannot be proven false, thereby circumventing the scientific method.
Unfortunately the scientific method does not apply well to historical research. In most cases falsifying the hypothesis means attempting to prove a negative. Thus, conclusions that require proof of a negative in order to falsify them are generally rejected as poor (untestable) hypotheses.
Most of the NASA believers that swallow the NASA story hook line and sinker usually end up making remarks of this kind or worse.
The author dismisses as a "non-argument" the notion that people will believe anything. Unfortunately it is still a phenomenon of belief, and something must be said to explain the propensity of people to believe an unsupported conclusion in the face of a preponderance of evidence to the contrary.
What is to be said for those of us who, contrary to buying NASA's story "hook, line and sinker", have studied NASA's story in great depth with professional expertise and have found it to be fully supported? The standard conspiracy argument is that anyone who rejects the conspiracy must be deluded. In fact, we can reject the conspiracy theory on the basis of careful and critical examination.
Though it's correct that stars will have been absent from the lunar photographic images it is strange that none of the astronauts remarked on the stars in the sky. The stars really will have been a magnificent sight at all times from the Moon.
Bill Kaysing's argument. The author still has not defended his assumption that the stars would have been "magnificent". In fact, at most times the astronaut would have been looking at a glaringly bright lunar surface illuminated by unfiltered sunlight, or similarly sunlit objects. The earth's atmosphere attenuates little light in the visible spectrum.
Astronaut Ed Mitchell said that he could see some stars if he blocked the sources of light and allowed his eyes to get used to the black sky. Astronaut John Young said it was disconcerting to see a black sky with no stars.
Therefore it is difficult to say whether the foot pads would have been covered in dust with any certainty.
We can be pretty certain. The footpads were 1-1.5 meters above the surface when the descent engine was stopped. As seen in the descent 16mm film, the dust fell immediately to the surface. From the study of fluid dynamics we know that the dust driven by the DPS plume hugged the surface, and Buzz Aldrin confirmed this by observation during his debriefing.
The LM cabin will have been filled with the sound from the engine and control thrusters.
No. The author relies on David Wozney's invalid comparison of the space shuttle's RCS and OMS engines. Wozney quotes the description of the shuttle RCS ignition transient. Similar ignition transients were heard by the LM astronauts.
The roaring sound from a rocket engine at steady state is produced by the interaction of the exhaust plume with the surrounding atmosphere. No atmosphere, no roar. In fact, if a rocket engine roars in a vacuum (as heard in the cabin), that would be the sign of a poorly designed engine. Flow noise would indicate imbalances or errors in the chamber construction.
Further, the microphones were designed to cut cabin noise. Anyone who has used a flight microphone knows this.
And finally, the astronauts had their helmets on.
However it is known that the LM engine and the space shuttle orbiter both use hypergolic fuel engines of the same type and same fuel ...
Absolutely false. The space shuttle's OMS and RCS use monomethyl hydrazine. The LM used a mixture of hydrazine and unsymmetric dimethyl hydrazine. The word "hydrazine" appearing in all of these does not mean they are identical. MMH and UDMH are related in the same way that gasoline and kerosene are related. They share many common chemical properties, but not necessarily the same combustion products and characteristics.
Further, the visibility of an exhaust plume depends on many things, including the size and construction of the engine and the viewing characteristics.
The Titan2 rocket used exactly the same fuel and oxidizer mix as the LM and yet it produced copious amounts of highly visible flame
Nope. Obviously this author hasn't seen many Titan 2 launches. The Titan 2 at steady state produces a nearly invisible plume. Its ignition transient produces copious amounts of highly visible smoke, but that too is due to interaction with the atmosphere.
Something very wrong there.
Yes, but what's wrong? How about people who can't even solve the most rudimentary physical and chemical equations pertaining to rocket propulsion giving us "authoritative" predictions and comparisons?
NASA is still to this day having trouble with vertical take off and landing rockets.
False.
The last known attempt ended in a crashed landing in 1996.
The crash in question happened after a successful landing, the last of several successful landings. The cause of the crash was an improperly configured landing gear.
The author neglects certain DCX problems, such as a reusable ascent/descent propulsion system, and the fact that it was unmanned.
The LM would have had to balance on one engine output only.
What preposterous ignorance. Rockets since the 1920s have had to "balance on one engine output only". This problem has been solved for decades.
The LM also had 16 small (110 pound) thrusters for attitude control and translation complicating matters considerably
What about the RCS jets would have "complicated" the LM's stability considerably? That's like saying that the brake pedal and accelerator "complicate" the operation of an automobile. This is really getting silly. This author has absolutely no clue what flight dynamics and flight control is about.
The Harrier is much flatter and with a much lower centre of gravity than the LM resulting in a more stable configuration as well.
I disagree. I've done some preliminary moment of inertia analysis on the lunar module. I doubt that the author of this FAQ even knows what that is. In the docked configuration the RCS would have provided considerable rotation moment. In the ascent-only configuration, the center of mass is actually below the center of thrust! The LM is a very stable design.
It can be seen that the Harrier jump jet and the LM are two different kettle of fish entirely.
Agreed, but the author's ceremonial gutting of the Harrier straw man completely ignores the fact that he doesn't know anything about the Apollo lunar module, how it was designed and flown.
The Moon is covered in powdered rock and rubble. The dust has a consistency described as being like cornflour.
For half an inch. Then it's hardpack. Surveyor proved this.
however NASA claims that the regolith (the powdered rock and rubble) that covers the Moon is 5 to 15 metres deep.
But not at the same density.
Instead we see a fairly smooth surface with a few light brush marks underneath the bell.
"Light brush marks"? Obviously this author has little understanding of fluid dynamics. It takes quite a bit of pressure and flow to create just "light brush marks".
There should have been a starburst pattern extending out beyond the footpads.
Wow, that's quite a prediction considering the author hasn't given any fluid dynamics equations or values to support his point, nor even given any understanding that he understands what fluid dynamics is.
I, on the other hand, have done a fair amount of fluid dynamics analysis on the DPS plume. What I see is what I expect. I want the author to give me a much more detailed and quantitative argument before I accept it as an authoritative expectation.
The main engine was not extinguished untill after touch down on some missions NASA say
Absolutely false.
In parts of the rover footage "vertical walls" or "curtain" formations of dust are seen to form in the wake of the dust kicked up by the rear wheels.
Nope, and this doesn't occur on earth. When particulates encounter a sufficiently dense ambient fluid, their trajectories become chaotic. This is not observed in the rover footage. Instead, the particles follow a ballistic trajectory.
Small particles of dust encountering atmosphere will have their ballistic flight path impeded to the point where sideways velocity drops to zero.
Not necessarily, but the trajectories will probably become chaotic.
In the Grand Prix footage the trajectories are primarily vertical because that's how they came off the wheel. The author relies on an affirmed consequent.
Also it's just not good enough to ascribe the cloud like appearance of the dust kicked up by the rover to "random motions".
I don't ascribe it to "random motions". In fact, I believe the motion is characteristically ballistic and not random. The author simply gives his subjective opinion that it looks like it's hitting air, when to my eye it looks exactly the opposite.
If you drive the wheels over coarse sand you will see the same thing.
Along with clouds of airborne dust, which are completely absent in the Apollo footage.
Jodrell Bank and sundry government scientists might have pointed their antennae at the Moon but none of that will prove man set foot on the Moon.
But when those station operators have interactive conversations with the people at the other end of the transmission, that's a pretty good indicator that someone's home. And when the time frame for those conversations doesn't allow for a double relay, the hoax argument collapses.
The only means of detecting a fraud would have been from the "leakage"
No. A central tenet of the hoax movement is the inability of spacecraft to pass safely through the Van Allen belts. The Soviets knew from their Zond experiments just how much radiation was there and what kind of shielding would be necessary. The Soviets also knew how the Apollo spacecraft were built. They even recovered an Apollo CM boilerplate. The Soviets are not dumb. They would know that the CM design would not work.
That would not have proven a problem however as microwave links are highly directional and thus inherantly very "leak proof"
Well, first, at 2 GHz the S-band radio communications are just barely microwaves. Second, the beam dispersal is between 0.5 and 3 degrees.
The answer to that is, why should the deployment and docking trials of the LM be any more real than the Moon landings?
Speculation piled on top of speculation.
If the LM wasn't fit to land on and takeoff from the Moon ...
The "proof" that it wasn't is nothing more than uneducated lay opinion.
So, aside from the fact that the operational suitability of the LM for such missions was in doubt given the history of the training vehicles
The only doubters are, again, untrained layman who can only handwave. By "history of the training vehicles" I suppose the author means the crash of the LLTV piloted by Armstrong. Strangely the conspiracy theorists never refer to the dozens upon dozens of completely successful LLTV flights and refer only to the one that was compromised by a technical failure.
the fact that even today it is beyond NASA's reach to have a rocket land and take off vertically with any reliability ...
Again, total ignorance of the facts. The DCX was much more ambitious than the lunar module and took off and landed successfully a number of times prior to its demise.
"According to an expert at DERA in the UK: Radiation is the biggest show stopper affecting mankinds exploration of the universe. ..."
And it is, because the missions being contemplated now are months or years long, not a maximum of two weeks as were the Apollo missions.
the thin-walled Apollo craft (from 8 through to 12) travelled during a solar maximum period, a time when there was a likelyhood of three or four severe flares per mission.
Um, what likelihood, exactly? Statistical probability gives us the ability to predict the likelihood of a solar flare occurring within a given two-week period. Where are the computations that prove how dangerous the Apollo missions actually were?
Even NASA admits that should there have been a severe flare while astronauts were on the Moon
Where exactly did NASA say this? This is contrary to what I've seen from NASA on the subject. NASA considered the probability of a relevant SPE during an Apollo mission to be relatively low.
They mislead the reader! It takes millions of years for anything to "boil up" from the depths of the Sun. It's just not possible to accurately predict when a solar flare will occur.
I am certainly not misleading the reader. At least not to the egregious extent to which Percy et al. are misleading the reader. An x-ray precursor provides the means of knowing as much as 36 hours in advance of the arrival of the damaging particles.
What good does that do? Depends on what phase of the mission the astronauts are currently in. During cruise flight the best option is to turn the tail of the CSM into the wavefront and hope for the best. During lunar EVA this provides enough time for the astronauts to return to the LM, ascend, and rendezvous with the heavier-shielded CSM. The CSM in lunar orbit is exposed to the particle wavefront for only half the time, and with the tail turned into the "wind" there would be a passable chance of survival.
About the best you can do is say they correlate with high sunspot numbers
No, that is not the best I can say. Predicting SPEs is big business for satellite operators.
That's right, they gambled with the astronauts lives.
Yes, they did, just as they gambled by putting them on a rocket filled with explosive fuel, just as test pilots do every day when they test experimental technology, and just as you and I do every day when we climb into our cars and drive at freeway speeds.
The conspiracy theorists have this odd notion that Apollo would be acceptable only if it could have been made perfectly safe. Nothing about Apollo was safe. It was dangerous, daring, and bold, and that's why it is worth our admiration.
When the chance of encountering severe solar flares was 3 or 4 per mission
Huh? Severe SPEs during a solar maximum do not occur at a rate of 3 or 4 per two-week period. Perhaps if all the events (including the benign ones) were considered you might come up with that figure.
But the command module didn't have the sheilding to protect against a severe flare.
As such, no. However the skin of the CM was thicker than the LM's. The real genius of the plan was the fact that by orbiting the moon the astronauts' exposure would have been cut in half. And if you turn the CSM so that the bulk of the SM is between the astronauts and the sun, you can cut the exposure even less.
NASA and its astronauts knew of the dangers and accept them. There were many aspects of Apollo missions that were simply unavoidably dangerous. The space shuttle still requires perfect operation during the first two minutes of flight, when under SRB power. This unmitigatable risk is accepted by the people who fly it.
The Moon relects only 7% of the sunlight that falls upon it ...
The albedo argument again. Albedo is not the be-all and end-all of reflectivity. 7% of sunlight is still very, very bright. 2-year-old asphalt has about 7% albedo and that's still enough to hurt your eyes. 7% of sunlight is still very photographically significant.
The alternative to the surface reflection hypothesis is that studio lighting was used. However, the conspiracy theorists cannot show any evidence that studio lighting is responsible for the fill lighting other than their rejection of all other potential sources. And there are many photos (e.g., the Aldrin egress photos) that clearly show the direction of fill lighting as below the astronaut.
They must have used a spotlight to take that photograph because the hotspot cannot have been caused by the heiligenschein effect.
Affirmed consequent. Just because heiligenschein causes hot spots does not mean that all hot spots are caused by heiligenschein.
Many images look like the background is dropped in to the foreground
I see this every day. I live in mountainous country.
In some NASA film footage included in the late Jim Collier's video "Was it only a paper Moon?" Young and Duke of Apollo 16
can be seen against exactly the same backdrop on two different EVA's (EVA1 and EVA2)
Collier uses secondary sources. It is correct in the primary source; the secondary footage was edited improperly and we have known about this for decades.
"Ordinary ektachrome slide film will shatter at -4F".
Not if it's on the Estar base. Most conspiracy theorists don't know the difference between emulsion and base. The emulsion is the chemical substance that records the image, and the base is the mechanical substrate on which the emulsion is coated. You can paint the Ektachrome emulsion on any transparent surface.
"Ordinary" Ektachome "film" would probably refer to the E-6 process emulsion on a cellulose base. That would indeed shatter at low temperatures. However the Estar base is a polyester base and was formulated for high-altitude reconnaissance photography and is good to temperatures near -50 F.
Wrong. There is plenty of heat in the vacuum and especially close in to a star. Heat is energy and there is plenty of it in the "vacuum" of space in the form of an energy flux.
This is a monumental piece of misdirection. The author is attempting to describe radiant heat transfer, and gets the flux right, but he neglects to mention that the "energy flux" is completely stopped by anything opaque. Stand in the shade and that "energy flux" is irrelevant.
EM radiation is not heat. It can be produced by heat and converted to heat, but it is not heat itself.
Claims that astronauts landed on the Moon
during the "lunar morning" in order to "avoid noon day heat" are ridiculous.
Not to someone who understands thermodynamics. "Heating up" is a matter of arriving at equilibrium, and heat transfer modes on the lunar surface are limited.
surface temperatures ... may reach 200 degrees fahrenheit on Earth in places like deserts and so forth [in a few hours].
Insolation on earth is radically different because the angle of insolation changes rapidly, presenting an increasingly favorable form factor for absorption. The sun rises very slowly over the lunar surface, a mere 12.5 degrees per day. That change is accomplished in less than one hour on earth.
Angle is everything, as any thermodynamicist can tell you.
It is fairly obvious from this that surface temperatures on the Moon can rapidly heat to more than +200F in much less than 24 hours of sunlight depending on angle of incidence. (emphasis mine)
Yes, exactly. Perhaps this author would like to do the calculus which compares insolation on earth versus insolation on the moon. Such a computation would be required in order to support the author's statement. Earlier the author reminded us that those who make a proposition are responsible for defending it. Here is a proposition that has a clearly outlined and clearly lacking defense.
This whole point is nothing but a bunch of vigorous handwaving. He clearly understands very little about practical thermodynamics.
For a recently landed lunar module standing vertically on the ground and presenting a surface that is perpendicular to the Sun's rays (which it will be during the lunar morning) the heating effect will be rapid and similar to that for level ground at midday.
This would be true if the polished aluminum and aluminized mylar of the lunar module had the same thermodynamical properties as the lunar surface. The author forgets that the equilibrium temperatures cited for the lunar surface are only valid for the surface material itself, not for any old object on the lunar surface.
The author takes albedo into account earlier. At 7% albedo, 93% of the sun's radiant energy (at some wavelength or group of wavelengths) is absorbed. What about aluminized mylar (albedo 50%) and polished aluminum (albedo 93%)?
These are all arguments that can be supported by thermodynamic computations, but where are they? As our resident thermodynamicist JR Keller has said, I have yet to see anyone who knew anything about thermodynamics.
It's just not true that it will take years, industrial diamonds are manufactured in much less time.
But gemologists are not fooled by industrial diamonds. The point is not that the process cannot be accelerated. The point is that if you accelerate the process, you lose the ability to fool experts.
Except of course that lunar evolution is still undecided. We know so much about the Moon from the samples that we still aren't sure exactly how the Moon formed.
Irrelevant. The author confuses uncertainty on a macro scale with perfect certainty on a smaller scale. Every geologist I have consulted is absolutely sure of what should constitute lunar surface samples and would recognize it if he saw it.
Again the author handwaves his way around unanimous expert opinion.
The trouble is that many facets of the Apollo story do not [stand up to scrutiny]
They do, to reasonable scrutiny. Inconsistencies based on the ignorance of the conspiracy theorists and selectively considered evidence are not legitimate questions.
Conspiracy theorists bring up the same arguments again and again, each time ignoring the clear refutations. This does not constitute ongoing scrutiny. It only constitutes ongoing closed-mindedness.
The Apollo samples have to match the known
Earthly samples.
No. There are aspects of meteoritic samples which should not be expected in lunar surface samples.
why should we believe that the samples were retreived manually just because they (NASA) say so?
Because the Soviet samples were undiscriminated. The Apollo samples consist of several sampling techniques (rake samples, bulk samples, chip samples, and core samples) and in many cases were specifically ordered by backroom geologists. The geologist says, "Hey, pick up that rock right there," and the astronaut does it. Then the geologist examines that precise sample.
"30 billion dollars were spent in sending man to the moon but all the paper work has been flushed down the toilet" [Collier]
Collier is dismayed that some of the design and manufacturing documents for Apollo spacecraft were destroyed. Collier is unaware of just how much and what kind of documentation accompanies such a project, nor what was destroyed. The amount of material that remains is colossal and astounding. I can find more information, faster, on the Apollo spacecraft than I can on, say, the Boeing 737 -- a relatively common machine.
The amount of historical material remaining from Apollo is monumental, and it's obvious that Collier nor any other conspiracy theorist has bothered to explore it.
Member
Here's a Gemini/Titan rocket lifting off with "copious" amounts of visible flame:
http://images.jsc.nasa.gov/images/pao/GT5/10074080.jpg
<font size=-1>[ This Message was edited by: Gastown on 2002-11-04 02:11 ]</font>
Established Member
In response the HB will cite the films, "Capricorn One" & "The Dish" as 'whistle blows' that prove that NASA can fake Earth-Space transmissions.Jodrell Bank and sundry government scientists might have pointed their antennae at the Moon but none of that will prove man set foot on the Moon.
But when those station operators have interactive conversations with the people at the other end of the transmission, that's a pretty good indicator that someone's home. And when the time frame for those conversations doesn't allow for a double relay, the hoax argument collapses.
Established Member
Here's an even better shot:Here's a Gemini/Titan rocket lifting off with "copious" amounts of visible flame:
http://grin.hq.nasa.gov/IMAGES/MEDIU...000-001020.jpg
Notice that the flame is far more transparent than, say, the flame from an Atlas or Saturn V. Also keep in mind that this was taken within Earth's atmosphere, so I wouldn't be surprised to see some visible effects. The space shuttle's main engines are another example.
-Adam
[EDIT]Changed img tags to url
<font size=-1>[ This Message was edited by: Firefox on 2002-11-04 09:04 ]</font>
Order of Kilopi
Noticee that the flame is far more transparent than, say, the flame from an Atlas or Saturn V.
Yes, absolutely. The Titan engines are larger too than the LM ascent engine. The white part above the nozzle is the combustion chamber, the component on this rocket that I've spent the most time studying. It's about 12 inches in diameter at the throat.
Note also that the "smoke" in this picture is actually water from the water suppression system. It's being hosed upward.
The Atlas and Saturn and space shuttle burn different fuels and so they aren't subject to direct comparision. But in the other picture you can clearly see the difference between the conflaguration of the ignition transient and the smoothness of steady-state firing.
There are dozens upon dozens of films of the Titan 2 being fired as an ICBM. The conspiracists have obviously seen none of it. Most of the conspiracists simply return to the same invalid comparisons to the shuttle RCS engines, obviously because that's the only detailed description they have of such rockets firing. Therefore the oddly ignorant assertions that the shuttle and LM burn "the same fuel". That has to be true, otherwise their argument falls apart. So they simply declare it to be true and sidestep around the fact that not everything with the word "hydrazine" in the title behaves the same.
Member
>Therefore it is difficult to say whether the foot pads would have been covered in dust with any certainty.<
Concerning the reasons why there is no dust on the lem's landing pads earlier in the thread, I have formulated a pet (half baked) theory which I'd like to put up on offer.
In some of the better photographs you can discern on the inner faces of each of the pads where it is adjacent to the engine exhaust bell, it appears to be covered with a different coloured material to the outer edges which are covered in the gold coloured Mylar. The material is similar in colour to the engine's exhaust bell. Dark grey/black. It is fairly clear on
http://www.hq.nasa.gov/office/pao/Hi...11-44-6574.jpg
LLL
http://www.hq.nasa.gov/office/pao/Hi...11-40-5917.jpg
or http://www.hq.nasa.gov/office/pao/Hi...11-40-5920.jpg
This suggests to me that the designers were providing some form of protection from the heat of the exhaust efflux. Therefore it seems to me likely, that they expected the possibility that the exhaust gasses would diffuse downwards and sideways sufficiently to partly impinge on the pad.
Common sense expectation tells me that if the exhaust is directed downwards it would not be likely to come anywhere near the pads which are well outboard of the exhaust nozzle. But consider the film of any Saturn launch when it reaches high altitude and is above the Earth's atmosphere. It can be seen that its exhaust appears to extend well above the level of the exhaust nozzles and 'creeps' up the side of the stage. This, I understand, is because it is exhausting into a vacuum, and it is occurring on a vehicle travelling forwards at several thousand mph. During the descent phase of the landing the lem is travelling backwards into its own exhaust at relatively low speed and would be descending into a dissipating zone of pressure, especially in the last moments before touchdown.
If that were so, then the pad would be swept clear of any displaced dust as it travelled backwards into its own exhaust until the engine cut off some three feet (plus) above the surface. By the time the pad touched down any dust displaced by the exhaust would have long since departed on a flat, sideways trajectory and therefor, in a vacuum there would be no possibility of dust coming anywhere near the pads, much less settle on them.
No doubt others who are more familiar with lem and engine design will find the holes in this theory that probably exist but it seems to me to be an aspect that I haven't seen considered before.
DK
edit: added photo reference
<font size=-1>[ This Message was edited by: Dave Kew on 2002-11-04 18:47 ]</font>
Order of Kilopi
I'm not sure the exhaust characteristics of the ascending Saturn V can be directly compared to the descending LM, but I can confirm that different skin materials were used on the inboard sections of the LM footpads. The dark material is H-film and was used to protect parts of the LM that would possibly be subjected to exhaust impingement. The "gold" aluminized mylar is not well suited to direct exhaust impingement.
Member
Thanks for the reply.[img]/phpBB/images/smiles/icon_smile.gif[/img]
I wasn't sure if this would hold water.
I was trying (badly) to use the S-V phenomenon to illustrate the point that the exhaust would dissipate 'sideways' and not just straight down as one might think.
Looking at the photo of the lem in flight the pads are well to the side and nowhere near in line with the exhaust bell yet they seem to have been protected.
My thought was that the pads were being 'swept' by the exhaust and therefor there never was any possibility of 'dust' getting anywhere near them.
Jus' a thought
DK
Order of Kilopi
You are correct about the plume dispersal in the F-1. But recall that the F-1's nozzle was tuned for sea level. The LM's nozzle was tuned for vacuum. There will still be some plume dispersal from the DPS because the perfect convergent-divergent nozzle is practically impossible. But it will be nowhere near as pronounced as the Saturn V at high altitude.
Order of Kilopi
I recall that the old animations that were used by the TV networks during the Apollo missions often showed a kind of "double plume" for rocket engines firing in a vacuum. There was a relatively strong "central plume" directed out along the engine axis, but also a much wider "inverted umbrella" plume spreading out from the engine bell.
Now, of course I realize that an artist's conception doesn't necessarily correspond to reality (thank goodness!), but I'm wondering if there may be a bit of truth in those animations. No doubt they used technical consultants and tried to get the effect right. Perhaps some of Von Braun's people were involved, or engineers from Rocketdyne.
In any case, I can speculate a bit on what might be happening here. There would be a boundary effect at the lip of the engine bell, a point of discontinuity where the exhaust gasses are no longer constrained by the nozzle. This might lead to a bit of turbulence along the margin of the exhaust flow, sending a small fraction of the plume out to the side.
This roundabout argument is to suggest that the "blow-dry" model of dust removal may just have some merit! [img]/phpBB/images/smiles/icon_biggrin.gif[/img]
<font size=-1>[ This Message was edited by: Donnie B. on 2002-11-05 10:30 ]</font>
Established Member
Here's another laughable bit of tripe from the same group.
LRV couldn't fit in, even when it's folded up? LOL, what a maroon.
Member
I know this is an ancient thread, but I figure at least some of the original participants may see it.Originally Posted by JayUtah
I think the different thermal protection on the inboard footpads may have been to protect against infrared radiation from the descent engine bell, as well as (or maybe instead of) direct impingement by hot gas. There may also have been thermal radiation from the plume. We know hypergolic engines in steady state emit little visible light, but what about other wavelengths? Burning hydrogen, for example, is almost invisible too but it emits a lot of ultraviolet.
There's a shield between the engine bell and the landing radar, designed to protect the latter from the intense infrared radiation. It's pretty obvious from the design of this shield (a simple rectangular plate) that the problem is radiation and not flowing gas.
Member
I agree. My simple calculations suggest the exhaust gas pressure at the bottom of the engine bell just before landing was about 6 psi. Four feet down this pressure probably less than 2 psi. Off to the side of the engine bell, well, I'm not sure how to calculate that. But I figure that the landing radar shield probably had to withstand up to 3 psi of pressure. That ain't much at all.
Order of Kilopi
Except that NASA does not fake transmissions in The Dish.
Order of Kilopi
Maybe Jay's post to should copied to all those Bulletin boards.....
Member
I don't think it would be the pressure so much as the heat transferred from the hot gas that might damage the radar antenna. 3 psi is actually a lot, but I doubt anything like that much was actually applied to that landing radar shield. It would have only had to block direct thermal radiation from the engine bell. I don't know how hot they get, but I've seen launch videos in which hypergolic second stage engines glow cherry red. They may or may not actually look like that to the naked eye -- CCD cameras are sensitive to the near IR -- but that's still a lot of heat if you're just a meter or so away.
Have you worked out the flow patterns of the DPS plume during landing? I'm curious to know just how the dust flowed, and why it didn't leave any appreciable amounts on the landing pads. The movies don't really give a sense of depth but it seems as though the plume went straight down and then out radially after hitting the surface, hugging it and taking dust with it. There would be nothing, no back pressure from an atmosphere, to launch the dust particles up at any angle from the surface.
Something else I've noticed in those movies: you see radial streaks in the dust sheet. I had always thought these were due to shadowing by rocks embedded in the surface, but they resemble the expanding, radial streaks of smoke I see looking down along launcher engine plumes in a vacuum. I don't know what they are, probably small eddies or instabilities in the plume as it leaves the engine bell.
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Why did I bother to even start reading something whose Table of Contents starts with "Forward and Intent"?
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Masochism?
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True, but what I was trying to say way back then was that they would cite fiction in support of their 'factual' claims.
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Small point...
Though it's correct that stars will have been absent from the lunar photographic images it is strange that none of the astronauts remarked on the stars in the sky.
This is largely thought to be due to the gold-plated visor used on the helmets. In 'A Man On The Moon', Mattingly's spacewalk on Apollo 16 is described in detail. Here, it is describes how Mattingly could not see the starts initially, but discovered upon lifting his visor he could.
Only a small point, but given I've just re-read that passage, that particular claim struck with me.
Ref: 'A Man on the Moon' - Andrew Chaikan, page 494 UK paperback.
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Though it's correct that stars will have been absent from the lunar photographic images it is strange that none of the astronauts remarked on the stars in the sky.
Some of them did -- it's wrong to say that none did.
Do people ever think clearly about something, or, better still, do a suitable experiment before they argue about what can or cannot supposedly be done under certain circumstances?
To check this out, one clear, starry night I decided to try to create a standard "sunlit" scene I could stare at with my right eye, while keeping the left eye in darkness, then go outside and look at the stars with one pupil wide open and the other stopped down. I live under almost-black sky on the edge of a small rural village and only have to walk a few hundred metres to get really black sky.
The "sunlit scene" proved to be far easier to create than I thought. Using a photographic light meter I positioned a piece of ordinary A4 80 gsm white paper next to a 50 Hz 200 watt light bulb. Reading only the paper with the meter set on 125 ISO gave a read-out of 1/125th of a second at f16 -- the perfect "sunny 16" setting.
For the left eye, I put a thick, black woollen glove over my left hand and cupped it over the eye so that no light got to it but I could keep it open and blink so that tears would not obstruct the view of the stars.
After cupping the left eye for about five minutes in ordinary room light, I continued this for about another four minutes while staring at the paper close up with the right eye. This length of time ensured a near-maximum difference in the size of my pupils.
The next trick was to get outside to a dark area quickly, using red torchlight, and check out the stars with both eyes. The difference was so great that it was confusing and initially made me feel quite giddy.
With the left eye I could make out all the faint stars I usually see after five minutes of dark adaption, plus the two Magellanic Clouds and globular clusters Omega Centauri and 47 Tucanae.
The right eye was a real problem. At first I could only see about four of the brightest stars and didn't really have a clue exactly which was which. Among them were probably Alpha Centauri, Canopus and Alpha Crux. It took between three and four minutes for some of the dimmer stars to become visible and for me to start recognising constellations. Mike Collins wrote about the same thing happening to him in Columbia on the way to the moon. And it was around eight to ten minutes before the right-eye view matched the left.
This experiment convinced me that it would have been very difficult for Apollo astronauts on the moon to see all but the brightest stars, if any. They had the disadvantage of sunlight affecting their dark-adaption and therefore their view of the stars. I didn't.
Last edited by Kiwi; 2009-Aug-27 at 04:51 PM.
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Isn't that an excellent book? I loved it.
Gene Cernan said in the ALSJ that he was able to see some stars from the lunar surface under the right conditions: "When you were in the lunar module, looking out the window, you certainly couldn't see stars. Using the telescope was sort of like being in a deep well; it cut out all the reflected light and let you see the stars. It was also generally true that, when you were on the surface in the LM's shadow, there were too many bright things in your field-of-view for the stars to be visible. But I remember that I wanted to see whether I could see stars, and there were times out on the surface when I found that, if you allowed yourself to just focus and maybe even just shielded your eyes to some degree, even outside the LM shadow you could see stars in the sky."
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Minor nitpick: You can have one eye adapted to darkness and the other eye to a bright scene. Your pupils however do both constrict if you're healthy.
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Well, that explains why it worked so well for me.I've been an invalid for 20 years, had "variable" health since a rugby accident in 1963, and without modern cataract surgery would have been completely blind for the last ten years. Going from can't-see-my-fingers-in-front-of-my-face to full vision overnight is an amazing and wonderful experience.
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