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Post by Jairo on Nov 19, 2009 1:24:46 GMT -4
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Post by LunarOrbit on Nov 19, 2009 1:29:06 GMT -4
Well, since people tracked Apollo all the way to the moon I think it's safe to say he is wrong.
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Post by JayUtah on Nov 19, 2009 2:48:08 GMT -4
Well, the site at which he posts seems to be dedicated to historical revisionism for its own sake. One wonders if these are the "peers" who reviewed his claims.
One of his articles attempts to argue that the visible artifacts of flight aerodynamics are inconsistent with the speed at which the vehicle was said to be traveling at or near staging. But another attempts to argue that the metallurgy of the F-1 nozzle is impossible. Yet the F-1 engines are clearly seen powering the vehicle. Which is it?
Unfortunately the software translation from Russian is not very good and not really sufficient to see where the ideas might be going wrong.
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Post by laurel on Nov 19, 2009 2:53:27 GMT -4
The Wikipedia article says that Porkrovsky claims a loop around the Moon was possible but landing was not. I might be completely off base here (wouldn't be the first time  ) but I just keep thinking that this sounds wrong. If you could use the Saturn V to send people to the Moon, why couldn't you send them there to land? Am I making any sense at all? |
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Ian Pearse
Mars
Apollo (and space) enthusiast
Posts: 308
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Post by Ian Pearse on Nov 19, 2009 4:59:52 GMT -4
The Wikipedia article says that Porkrovsky claims a loop around the Moon was possible but landing was not. I might be completely off base here (wouldn't be the first time ) but I just keep thinking that this sounds wrong. If you could use the Saturn V to send people to the Moon, why couldn't you send them there to land? Am I making any sense at all? If you can get into a loop round the Moon, then it only takes the relevant delta-v to turn that into a lunar orbit, then another change to make it a descent. The Saturn V wasn't doing that bit anyway, it was the Apollo spacecraft, so I can't guess what he is on about. edit for typo |
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Post by tedward on Nov 19, 2009 5:33:35 GMT -4
The tracking sort of knocks it on the head I would have thought? Especially if the Russians (and others) can claim to have listened in to the comms, then there had to be someone there. In being there they needed life support and the method is known for the duration so that capsule and support was on the way and around and bits of it on the moon.
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Post by homobibiens on Nov 19, 2009 6:24:01 GMT -4
My Russian is bad enough these days that I don't think I'll try a translation, but could the argument simply be that, if the speed on the way to (and therefore back from) the moon is too low, then there just wasn't enough time to land and do the various lunar surface activities in the amount of time spanned by a mission?
Edited to add - it bugs me that I have to say things like this, but my speculating about what the particulars of this person's argument are, in no way means that I endorse said argument in part or in whole.
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Post by Jason Thompson on Nov 19, 2009 7:27:50 GMT -4
The trouble is that if the speed was too low it couldn't have reached the Moon in the first place. Anything less than 25,000mph doesn't allow the spacecraft to get near enough for the Moon to capture it before it gets pulled back by Earth's gravity.
Space travel isn't like car travel, where you can pretty much drive at any speed you like. There are certain speeds you have to achieve in space in order to get you anywhere. In this case it really is true that either the Saturn V could send them to the Moon or it could not. There is no middle ground.
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Post by homobibiens on Nov 19, 2009 8:36:53 GMT -4
The trouble is that if the speed was too low it couldn't have reached the Moon in the first place. Anything less than 25,000mph doesn't allow the spacecraft to get near enough for the Moon to capture it before it gets pulled back by Earth's gravity. Space travel isn't like car travel, where you can pretty much drive at any speed you like. There are certain speeds you have to achieve in space in order to get you anywhere. In this case it really is true that either the Saturn V could send them to the Moon or it could not. There is no middle ground. I recognize that, but neither speed referenced in the summary article is anywhere close to escape velocity, so I am not sure what they are supposed to be. The higher quoted speed comes out close to the simple average (total distance divided by total time) Apollo craft took to the moon. The lower speed is way too slow to be interpreted as the average speed on a simple loop around the moon though. So I guess I don't know what his speeds are supposed to be. |
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Post by JayUtah on Nov 19, 2009 12:35:58 GMT -4
Again, dealing with the mechanical Russian translation is problematic. We may be getting much of this wrong. Pokrovsky's line of reasoning seems to be that since he believes he has proved that the Saturn V was underpowered, the only mission that could have been flown with it is a circumlunar or orbital mission such as Apollo 8. He uses the Apollo 11 film and photography as the basis for his interpretation. Apparently he presumes the payload loadout for this mission was as published and is consequently too heavy for the "underpowered" Saturn V. Since it will be his claim that NASA never intended this mission to be successful, one wonders why they so scrupulously overloaded their launch vehicle to the proper payload mass. His photo analysis attempts to measure various aerodynamic effects in the photographs and fit them to theoretical models of transonic and supersonic behavior. The models predict a lower speed than the normalized Saturn V published profile, given the photographic observations. Pokrovsky derives a key value for his analysis -- the half angle of the shock wave from the SLA -- as 22.5 degrees. But the derivation is completely missing from his paper. He simply measures it at various angles in photographs, then says "taking into account all errors" (tr.) it should be 22.5 degrees. From this, and using a theoretical model of atmospheric density (not the actual flight conditions), he derives a speed of 3.2 Mach. In other words, he has pulled his most crucial figure out of thin air (pun intended). The rest of the paper seems to be the standard "dazzle 'em with math" smoke-blowing, of the kind done by David Groves on behalf of David Percy. We can take a short detour and look at one of Pokrovsky's other paper describing the supposed deficiency of the F-1 engine. babelfish.yahoo.com/translate_url?doit=done&tt=url&intl=1&fr=bf-home&trurl=http%3A%2F%2Fsupernovum.ru%2Fpublic%2Findex.php%3Fdoc%3D62&lp=ru_en&btnTrUrl=TranslateBased on what he claims to be recent discoveries in the high-temperature properties of Inconel (a trade name for a nickel alloy commonly used in aerospace), Pokrovsky claims the Rocketdyne F-1 engine could not have performed as claimed because the regenerative-cooled nozzle and thrust chamber could not have withstood the heat. The translation makes it difficult to determine whether he is claiming the F-1 wouldn't have worked at all, or simply whether American engineers could not have known the F-1 would work. Notably absent in Pokrovsky's paper is his actual examination of the nickel used in the F-1 engine. All his claims and computations are derived from theoretical models. Apparently Pokrovsky has never seen a Rocketdyne F-1. But what's most notable about this paper is that about halfway through it Pokrovsky tap-dances through a discussion of a necessary decrease in radiant flux in order to reduce engine temperature (and therefore performance) in order to avoid overheating the Inconel nozzle. Again, no actual measurements of exhaust-product heat content -- just references to simplified theoretical models. Not surprising, the figure he arrives at after some well-concealed handwaving and guesswork is exactly what would it would need to be in order to reduce the fully-laden Saturn V's velocity by the amount he estimates in his first paper. Hm. But a very tell-tale statement appears in this paper. Pokrovsky doesn't question the upper stages of the Saturn V or the performance of the J-2 engines. He only questions the S-1C and its F-1 engines. In the broader perspective, Pokrovsky's measurements of the Saturn V velocity derive entirely from about five seconds of the vehicle's flight. He essentially takes a snapshot of the vehicle performance at one instant in its flight and extrapolates a whole lot from that. Even in the worst case, if the actual performance of the Saturn V fell short of its published performance (which, in Pokrovsky's case, he gets from a 1973 Russian source) in that instant, that doesn't mean it didn't fly. The first two and a half stages of the Saturn V had only the task of getting the S-IVB and its payload to Earth orbit. The flight to the Moon consisted of the TLI burn. Since Pokrovsky accepts that the S-IVB and J-2 engines performed as advertised, and since he seems to take as a premise that the full Apollo spacecraft stack was on the Apollo 11 launch vehicle (hence why the poor S-1C stage was huffing and puffing), there's a massive non sequitur in his claims. To reiterate, it seems that Pokrovsky has focused on the minutiae of tree bark in his claims while missing the fairly obviously validity of the forest. Apparently he hopes that his mathematical razzle-dazzle will convince the majority of non-technical readers that there's something to his claim. |
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Post by JayUtah on Nov 19, 2009 12:43:36 GMT -4
I recognize that, but neither speed referenced in the summary article is anywhere close to escape velocity, so I am not sure what they are supposed to be. Pokrovsky's study considers the visible aerodynamic indicators (e.g., shock waves) only at and around S-1C (first-stage) staging. For him this constitutes a point in the ascent profile where altitude and velocity should be precisely known from published expectations. S-1C staging occurs nominally about 160 seconds after ignition. Therefore at T-plus 2 minutes 40 seconds the vehicle should be traveling at a certain speed. That speed won't yet be escape velocity or even orbital velocity. The second stage has yet to do its thing. Pokrovksy's claim is that he measures the vehicle's speed at T+2:40 far lower than it was supposed to be at that point in the flight. |
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Post by homobibiens on Nov 19, 2009 15:05:55 GMT -4
Again, dealing with the mechanical Russian translation is problematic. We may be getting much of this wrong. I may have a look sometime, but it's been a really really long time  Pokrovsky's study considers the visible aerodynamic indicators (e.g., shock waves) only at and around S-1C (first-stage) staging. For him this constitutes a point in the ascent profile where altitude and velocity should be precisely known from published expectations. S-1C staging occurs nominally about 160 seconds after ignition. Therefore at T-plus 2 minutes 40 seconds the vehicle should be traveling at a certain speed. That speed won't yet be escape velocity or even orbital velocity. The second stage has yet to do its thing. Pokrovksy's claim is that he measures the vehicle's speed at T+2:40 far lower than it was supposed to be at that point in the flight. Ah, that makes sense. So then, the argument is supposed to be something like, less speed per amount of fuel burnt ==> more fuel needed to get to the moon ==> less payload can be carried ==> not enough hardware to land on the moon? |
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Post by Jairo on Nov 19, 2009 20:17:28 GMT -4
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Post by JayUtah on Nov 19, 2009 21:00:30 GMT -4
Would it worth to check if those things really exist? It may, but the fault in Pokrovsky's work lies in his carefully-disguised or off-the-record derivations, assumptions, and simplifications. Those will not be easily spotted by the reader. Whether those sins were committed by an expert or a layman does not materially alter their nature or why they compromise his findings. |
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Post by Count Zero on Nov 20, 2009 1:07:30 GMT -4
He only questions the S-1C and its F-1 engines. That's rich! The one part of the entire flight that the most people (including myself) watched in person... ...didn't happen as advertised.  |
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) but I just keep thinking that this sounds wrong. If you could use the Saturn V to send people to the Moon, why couldn't you send them there to land? Am I making any sense at all?
