|
|
Thread Tools | Display Modes |
#11
|
|||
|
|||
I didn't see the original postings, but a whole infrastructure needs to be
built that can handle going to the moon. Currently, I believe the heaviest booster is the Titan with strap-on booster which could make a payload trip; however, it is still insufficient to do a job the size of continuly going to the moon. It's is technically possible, but look at what is needs: very-heavy boosters, that are more efficient and less costly to lauch and service, that are reusable. Something capable of at a minimum of acheiving high earth orbit to a space station for transfer to the Moon, or just being able to go straight there with payload and manned space ships, not shuttle, no need for aerodynamics and the weight. Cargos that aren't time constrained may benefit by use of ion and solar propulsion systems. Non-the-less, going to the Moon, which I favor as a staging point for Mars, involves a whole new industry's and it's infrastructure, and would be the testing grounds for mission beyond. davon96720 "Greg D. Moore (Strider)" wrote in message ... wrote in message oups.com... I was arguing with a friend that the lunar landing required very little new science but merely extrapolations of existing technology. This leads to: If it had been necessary, and cost was no object, what would be the earliest time that a lunar landing would have been possible. I argue that the Germans could have done it with their 1940s technology. "It depends". You can look at the Saturn V as a scale-up of the V-2. Just a much bigger rocket. That is of course an extremely simplified look at things. Getting the F-1 engines to burn stablely was itself a large task. Then of course you have things like the IU and on-board computation. Even with the advances there, much of the navigation was helped out by the ground. And of course things like fuel cells. While the science had been around for I think about a century, making it work effectively was part of the problem. Ultimately I think it comes down to, "how much brute force and money are you willing to throw at the problem?" |
#12
|
|||
|
|||
I didn't see the original postings, but a whole infrastructure needs to be
built that can handle going to the moon. Currently, I believe the heaviest booster is the Titan with strap-on booster which could make a payload trip; however, it is still insufficient to do a job the size of continuly going to the moon. It's is technically possible, but look at what is needs: very-heavy boosters, that are more efficient and less costly to lauch and service, that are reusable. Something capable of at a minimum of acheiving high earth orbit to a space station for transfer to the Moon, or just being able to go straight there with payload and manned space ships, not shuttle, no need for aerodynamics and the weight. Cargos that aren't time constrained may benefit by use of ion and solar propulsion systems. Non-the-less, going to the Moon, which I favor as a staging point for Mars, involves a whole new industry's and it's infrastructure, and would be the testing grounds for mission beyond. davon96720 wrote in message oups.com... I was arguing with a friend that the lunar landing required very little new science but merely extrapolations of existing technology. This leads to: If it had been necessary, and cost was no object, what would be the earliest time that a lunar landing would have been possible. I argue that the Germans could have done it with their 1940s technology. |
#13
|
|||
|
|||
Henry Spencer wrote:
Right up till they got to their 30 engined N-1 Moon rocket it worked, then it didn't work. There was nothing intrinsically wrong with the N-1 design; I disagree, I think it had too many motors to be reliable, and that the decision to mount the kerosene tanks on top of the Lox tanks was fundamentally flawed for the following reasons: 1.) One of the basic ideas that the N-1 was based upon was that of having the ability to lose a motor or two during ascent, and have the KORD system shut down the opposing motor to keep things balanced in regards to thrust from the ring of motors so far from the rocket's centerline. Good idea, but it relies upon a benign shutdown of the motor before it suffers a catastrophic failure and damages the motors near it; since the maximum number of motors that could be shut down was four (two malfunctioning motors and two opposing motors shut down to compensate for the asymmetrical thrust), and a catastrophically failing motor was liable to damage the motors on either side of it...causing three motors to shut down, and thereby exceeding the total of four shutdown motors maximum- as three motors on the opposing side of the vehicle also shut down- what you've effectively got is a rocket that will fail if it has even one motor undergoes a destructive failure rather than a benign shutdown, and of course this scenario actually happened during the second launch attempt. Further, the large number of motors that need to be manufactured for even a modest number of launches (the Soviets made a total of around fourteen N-1's, or at least had that many at some stage of construction although they only launched four- that's a total of 420 motors for the first stages alone, and a total of 588 if you count the basically similar second (8) and third (4) stage motors) means that you can't afford to do strenuous tests on the individual motors if you want to get up to a reasonable launch rate, and must minimize the man-hours spent on making each motor. Neither of those choices is going to add to the overall reliability of an individual motor. 2.) Whereas the stacked-spheres approach to the propellant tankage was a seemingly clever use of the different volumes need for the Lox and kerosene, it inevitably ends up with the larger diameter Lox tank sphere in the bottom position in all three stages of the basic booster; and with that decision comes a real problem- if you put the Lox tank on top (like in Atlas and Saturn V) you can put an insulated Lox feed pipe through the interior of the kerosene tank...the pipe will begin to chill when Lox flow starts at the beginning of the engine ignition process, but the cold won't have much chance to migrate through the insulation into the kerosene during the short time that the motors will be burning, and the thermal effect on the feed pipe will cause it to shrink in diameter from the cold; so that it might pull itself free from some of its insulation at worst. Now, consider what happens if you try the same thing with the Lox tank on the bottom, like in the N-1; now you have a insulated kerosene_ feed pipe going through the interior of the Lox tank. During the fueling process this pipe is going to be slowly immersed in cryogenic Lox, and it will start to supercool even if it's insulated, due to the amount of time the propellant loading process takes. Then comes the moment of propellant feed starting to the motors in preparation for ignition... two things happen... first, warm kerosene comes in contact with the cold metal of the kerosene feed pipe that is traversing the Lox tank, causing thermal shock and rapid expansion of the pipe inside of its insulation blanket, this could easily result in cracking of the pipe in much the same way that sticking a hot dinner plate into cold water can. Second, as the kerosene transmits its heat into the feed pipe, the feed pipe transmits its cold into the kerosene, which begins to gel, choking off the fuel flow, and causing chunks of gelled kerosene to break free and enter the engine turbopumps, with disastrous consequences. So on the N-1, the fuel had to flow around the exterior of the Lox tank rather than through it; and as soon as you do that, the amount of plumbing needed goes right through the roof. The Lox belongs on top of, not under, the fuel supply. I tried to figure out a way to feed a large number of motors while minimizing plumbing weight, and assuming you're going to arrange them in a circle, like the outer twenty-four on the N-1 were, then the only thing I could come up with was have the propellants feed into two toroidal pipes- one, carrying the heavier propellant (kerosene in the case of the N-1; Lox in the case of Lox/LH2) sets just inside the ring of motors; the other sits on top of the motors, and the motors and their turbopumps are "plugged into" these toroidal pipes at their tops and sides. The toroidal feed pipes are themselves connected to their respective propellant supply tank by a single feed pipe. it simply was an overly-rushed and cash-starved development program, e.g. with *no* ground test of the full first-stage propulsion system, and the politicians' patience ran out before debugging was finished. Note that when it came time to do a new heavy lift booster, Energia was a far different design with far fewer motors. The Saturn V, with somewhat more time and a lot more money, still had serious bugs as late as Apollo 13. By luck -- quite a bit of luck in the case of Apollo 13's second stage -- none was catastrophic. I think that the Saturn V's good luck was partially due to it's good engineering and straightforward and tough design; and that the N-1's bad luck (it never even got to the end of first sage burn in four launch attempts) was due to bad engineering and an overly complex design. The big feed lines for a handful of large engines aren't light either. There *is* extra plumbing mass with a many-engine cluster, but the difference comes from second-order effects. In the case of N-1 it was from the need to get those kerosene lines all the way around the big Lox tanks; each of those pipes is around fifty feet in total length from the base of the kerosene tank and the motor it goes to, and you are dealing with thirty of them- for around 1,500 feet total of kerosene feed pipe in the N-1's first stage. Some of us don't think four launches per day is at all unrealistic -- although it might have required a somewhat different vehicle design -- viewed from a clean-sheet-of-paper perspective, rather than from the stifling trap that we've gotten ourselves into in the last few decades. Remember- four launches a day; first and second stages recovered at sea; and a twenty shuttle fleet. In short; you have to launch one, recover the two stages, check everything for condition, restack it, add payload, move it to the pad, fuel and relaunch it inside of five days. On any given day, you have four in operation, and sixteen being recovered, refurbished, and readied for launch. That's a hell of a big infrastructure- even with something far simpler that the Shuttle. We were awestruck when the Soviets managed to put up two Vostoks in a 24 hour period in 1962; and the Vostok booster was a far smaller and less complex thing than these rockets would be. We're talking about launching things the size of Saturn V's every six hours, day in and day out, and I think that would be almost impossible nowadays- much less in the time frame we are discussing particularly given the rocket's reusable aspect, and all the effort that implies in regards to recovery and re-flight certifying the first and second stages. Bell shares a fundamental error with most of today's Old Guard rocketry establishment: he thinks today's incredible stupidities are laws of nature, that the Emperor couldn't *possibly* really be standing there with no clothes on. Well, would you care to define a design using the technology available in the 1945-1960 time period that would allow the building of a space station and manned moonship? It wasn't like we were sitting on our thumbs during that period in regards to rocketry; we were moving from tactical missiles to IRBMs to ICBMs at a pretty good clip, as were the Soviets. The only thing we weren't doing was pushing for manned spaceflight immediately, as I assumed that both sides realized that the technology was advancing at such a rate, that what would be very expensive and difficult in 1950 would be far easier by 1955, and easier yet by 1960. A lot of Armstrong's problems were because he was improvising a landing in unfamiliar terrain. And *that* was the result of, to put it bluntly, a mistake he made earlier: Of course, heading for the Moon with a manned expedition before you have had a good look at it via robotic landers and photographic probes like Surveyor and Lunar Orbiter means that the whole place won't be known in detail until the first ship is on landing approach...and the robotic probes and landers require fairly sophisticated electronics to perform their missions, electronics that weren't in existence in the time frame we are discussing. he had his attention inside the LM looking at the computer alarms, when he should have left those to Aldrin and kept his mind on navigation and his eyes on the surface. Nowadays, this is a standard lesson all pilots learn -- you must divide responsibilities, it's a lethal mistake to have *everyone* preoccupied with troubleshooting and nobody flying the damn plane -- but it wasn't part of the gospel then. And the Apollo 11 crew probably wasn't all that well integrated, simply due to shortage of training time, so Armstrong may not have been all that confident in Aldrin. With more eyes watching -- say, a dedicated navigator -- this would have been much less of a problem. And with no computer, you don't have computer alarms. :-) The only big question is whether you abort the first landing attempt when you realize you're coming down well off course, or try to correct. (If you abort, the *next* ship has the proper correction cranked in ahead of time.) Probably you try to correct, because the navigator catches the growing discrepancy early. I'd be very concerned about your descent speed in a situation where you can only rely on your radar return and eyes during landing. With no way to know the scale of the surface features you are looking at, a horizon that is far closer than on Earth, and a lack of any haziness of objects in the distance due to atmosphere, I could see the crew of the moonship ending up hovering at several hundred feet above the surface and using up all their fuel thinking that they are going to touch down at any moment, or worse hitting the surface at high speed thinking that they are still several hundred feet up and have time to brake their descent. Not a trivial issue, although eased considerably by assembling the lander in space so you're not wrestling with packaging constraints too. And the LM landing gear turned out to be drastically overbuilt. That's because Grumman built it; the thing was designed to slam down on a carrier deck at 100 mph, you know. :-) What matters is not so much how big the lander is, as how well it responds to the controls. Large size and poor control authority don't *have* to go together. That means big RCS motors though, and with those comes a structure strong enough to tolerate their thrust, and the higher propellant consumption that would go with them. The problem was more that it was going to be as *tall* as an Atlas, and that the constraints of launch from Earth meant that the crew were going to be at the top. No one ever did figure out a good solution to that conundrum, did they? Which made for very awkward problems of adequate view for the landing, the issue that finally sank EOR. This is much less of a concern with a space-assembled vehicle. Yeah, you could put the crew at the bottom, the fuel on top of them and four outward angled rocket motors at the top. By gimbling them and varying their thrust, you wouldn't even need an RCS system. Not that any of those 1950's designs I've seen ever _did_ it that way of course...the poor astronauts always face a long trip down to the lunar surface from around a hundred feet up or so, even on the space assembled landers. and we couldn't get one of those to take off reliably, much less have it gently touch down without exploding. A problem that had very little to do with its mass. But to work in a reasonably sized package (something smaller than a Saturn 1), a lunar lander has to be fairly lightly built in regards to its mass ratio, like the LM was. A lot of propellant weight in a lightly built spacecraft structure isn't going to like a hard landing. Getting a heat shield to take those reentry heats would have been a real problem given the state of technology at the time, and Titanium and Inconel metallurgy for spacecraft structure wasn't nearly as finessed as it later became... You don't really need high-temperature structures if your thermal protection is good. And suitable steels make quite good high-temperature structures -- more heat-resistant than titanium -- although they're rather heavy. But an adequate heatshield would indeed have been a problem; von Braun's ideas on that aspect were naive, in hindsight. Remember, these were the guys who put wooden wings on the A4b, and then were surprised when one came off during reentry. Prior to 1950, our knowledge of the upper atmosphere wasn't all that good, and we didn't get a good handle on what a space vehicle encounters during reentry at high speed until around 1955. The difficulty is not so much materials technology -- notably, there would be nothing very difficult about making an ablative heatshield, even with WW2 technology, so long as you weren't too worried about how much it weighed -- as the insight that reentry bodies should be *blunt*. It took quite a while for people to realize that; it wasn't obvious. I'm picturing a CM sized copper heat sink heatshield to take the heat of lunar reentry...okay we get the LM and SM up into orbit on one Saturn V....then a second Saturn V is launched with the CM on board, after the two S-IVB stages accelerate the separate vehicles onto a lunar trajectory, the CM docks to the LM, and then to the SM... :-) Assuming somebody hits on a suitable approach to the heatshield problem, say five years for the first orbital scout flights, another five for a heavy ferry and construction start on a station, and five more to finish the station, fly a scout mission around the Moon, and gear up to attempt a landing. Maybe 1960. That's about what I thought if you threw a tremendous amount of resources at it, and got some lucky breaks. But the cost of such a crash program would have made Apollo look cheap. You might be able to cut a few years off that if it's a crash program from the start, aimed at a lunar landing soonest rather than systematic progress while building infrastructure. That would mean (as Pat says) tolerating both failures and loss of life, and a certain amount of conspicuously wasted money. And perhaps a bit of luck. This would be like making the space program the equivalent of the Manhattan Project- absolutely ASAP, no matter what the cost. It wouldn't have been a rational approach to the problem, and I doubt if it would have been politically possible. There has been quite a bit of development work on automated docking in US labs; what is lacking is funding for flight tests, and that is closely tied to a lack of any real requirement for it (given that all US station flights are manned anyway). It would have allowed us to assemble stations in orbit before a crew was launched to them, or enlarge them without needing further manned launches or involved EVAs. Mir made Skylab look clumsy; but having the Saturn V's lifting capacity along with a means of docking Skylab sized modules in orbit automatically would have given us a great station by 1980 at a comparatively knock-down cost. Anyway, with a von Braun approach, both the ferry and the station's tug are manned, so that's not an issue. The problem is that you have to rethink both the station design and the moonship design to be *modular*, so that you are plugging modules together rather than riveting girders together. That may also require one more rev of the ferry design, to give it a larger cargo hold -- not necessarily more cargo mass, you can outfit the modules from within once they're connected up, but more cargo volume so you can launch a reasonable module shell in one piece. Of course, one of the reasons that von Braun had everything manned, was that they didn't have sophisticated electronics to do the comparatively mundane tasks that he had people doing instead...he points out that a enemy missile with a sophisticated enough guidance system to intercept his space station would be too heavy to work...and even if it could be built, it's going to encounter the station's _cannons_...which oddly enough, don't seem to be on those cutaways of the station that are in Colliers. Even in WW2, if I've got the dates straight, people understood that solar flares produced radiation; the neutrons from upper-atmosphere particle hits at high latitudes are detectable on the ground. I don't think they knew the severity of the radiation till they encountered the Van Allen belts and the space beyond them though. Mind you, the crash-program timing I noted above is unfortunate, in that it may put your first lunar expeditions during the nasty solar maximum of the late 50s. The belts would be discovered by early orbital scout flights, cosmic radiation being recognized even then as an area of concern. In the real world, while nobody (well, except for Nick Christofilos and a handful of other people acquainted with his highly-classified work) was expecting trapped-radiation belts, cosmic rays had been known since 1911 and their intensity outside the atmosphere was a serious unknown... as witness the fact that the major science instrument on the first US satellite was a cosmic-ray detector. Some of the scout pilots might get rather high doses while finding out the extent of the problem, mind you. I'm still waiting for the ferry rocket to malfunction during launch and having it fall on one of the other ferry rockets on it's pad and then all four scheduled for that day's launches go up in one big poisonous fireball. :-) Pat |
#14
|
|||
|
|||
Greg D. Moore (Strider) wrote:
"To a point". The N1's problems I don't think were ever fully resolved. The point is still the same. That at that point it was mostly an engineering problem, at least I'll argue it was. :-) I should have thought of this before- there is one real historical incident that sort of mimics what we are discussing here; a crash program to develop former Nazi technology in regards to spaceflight...it's the Saenger Antipodal Bomber project, and it's Soviet offshoot- designed by Keldysh: http://www.luft46.com/misc/sanger.html http://www.astronautix.com/lvs/kelomber.htm The whole thing was far too ambitious given the technology and limited data on the upper atmosphere of the time, and the program collapsed in favor of ICBMs. Pat |
#15
|
|||
|
|||
Am Mon, 20 Dec 2004 16:30:38 -0600 schrieb "Pat Flannery":
However, that was mostly a consequence of its very large combustion chamber. When the Russians ran into similar problems, they responded by clustering smaller chambers instead, which worked. Right up till they got to their 30 engined N-1 Moon rocket it worked, then it didn't work. There is also a great deal of propellant feed plumbing weight associated with such an approach. [...] Oh, I'll back Henry. In the beginning the Russians did not really cluster large amounts of ENGINES - they clustered THRUST CHAMBERS. The original R-7 ICBM had 'only' five engines, but 32 thrust chambers in total. I agree your opinion, that their later approach of using 30 independent engines in the 1st stage of N1 (and not to forget the clusters of upper stages) was deemed to fail. cu, ZiLi aka HKZL (Heinrich Zinndorf-Linker) -- "Abusus non tollit usum" - Latin: Abuse is no argument against proper use. mailto: http://zili.de |
#16
|
|||
|
|||
"Pat Flannery" wrote in message
... Henry Spencer wrote: Right up till they got to their 30 engined N-1 Moon rocket it worked, then it didn't work. There was nothing intrinsically wrong with the N-1 design; I disagree, I think it had too many motors to be reliable, and that the decision to mount the kerosene tanks on top of the Lox tanks was fundamentally flawed for the following reasons: 1.) One of the basic ideas that the N-1 was based upon was that of having the ability to lose a motor or two during ascent, and have the KORD system shut down the opposing motor to keep things balanced in regards to thrust from the ring of motors so far from the rocket's centerline. Good idea, but it relies upon a benign shutdown of the motor before it suffers a catastrophic failure and damages the motors near it; since the maximum number of motors that could be shut down was four (two malfunctioning motors and two opposing motors shut down to compensate for the asymmetrical thrust), and a catastrophically failing motor was liable to damage the motors on either side of it...causing three motors to shut down, and thereby exceeding the total of four shutdown motors maximum- as three motors on the opposing side of the vehicle also shut down- what you've effectively got is a rocket that will fail if it has even one motor undergoes a destructive failure rather than a benign shutdown, and of course this scenario actually happened during the second launch attempt. Catastrophic failure of liquid fueled engines is a "bad day" no matter how many engines are in your cluster. Note that a catastrophic failure of an F-1 engine on the S-1C stage or a J-2 on either the S-II or S-1VB stages would have been a "bad day" for an Apollo Saturn V. Note also that for benign failures of liquid fueled engines, the Saturn V had a limited ability to continue with engines shut down, but that was only a possibility later in the stage burns, and wasn't a possibility at all for the S-1VB stage. In particular, loosing an F-1 engine early in the flight would have been very bad. Here's an article that mentions "Studies indicate that the immediate structural dynamic transients at engine-out will not cause structural failure. However, certain combinations of engine failure and wind direction and magnitude may result in a divergent control condition which could cause loss of the vehicle.": http://www.apollosaturn.com/s5flight/sec2.htm Here's an interesting article which talks about F-1 engine failure modes: http://www.system-safety.org/~journal/techarticle.html As you can see, the Saturn V, with fewer engines than the N-1, could also be destroyed by an engine failure, even if that failure wasn't "catastrophic" in and of itself. Further, the large number of motors that need to be manufactured for even a modest number of launches (the Soviets made a total of around fourteen N-1's, or at least had that many at some stage of construction although they only launched four- that's a total of 420 motors for the first stages alone, and a total of 588 if you count the basically similar second (8) and third (4) stage motors) means that you can't afford to do strenuous tests on the individual motors if you want to get up to a reasonable launch rate, and must minimize the man-hours spent on making each motor. Neither of those choices is going to add to the overall reliability of an individual motor. This seems to be an unfounded assertion. A higher manufacturing rate usually allows you to improve manufacturing in terms of repeatability, tolerances, and the like. Manufacturing problems can easily happen when you have a very small, limited production run, which means that your need for "strenuous tests" is likely higher with a small run as compared to a very large run, where repeatability in the manufacturing processes has already been achieved. Sounds like "damning with faint praise" to me. The strenuous tests of the F-1 were required due to the small production run, and the high likelihood of the Saturn V being destroyed by an F-1 engine failure early in the flight. Jeff -- Remove icky phrase from email address to get a valid address. |
#17
|
|||
|
|||
Pat Flannery wrote:
Further, the large number of motors that need to be manufactured for even a modest number of launches (the Soviets made a total of around fourteen N-1's, or at least had that many at some stage of construction although they only launched four- that's a total of 420 motors for the first stages alone, and a total of 588 if you count the basically similar second (8) and third (4) stage motors) means that you can't afford to do strenuous tests on the individual motors if you want to get up to a reasonable launch rate, and must minimize the man-hours spent on making each motor. Neither of those choices is going to add to the overall reliability of an individual motor. Nonsense. If you allow for testing/tweaking time in your manufacturing schedule and budget, it doesn't matter if you are making 10 motors or 10,000. D. -- Touch-twice life. Eat. Drink. Laugh. -Resolved: To be more temperate in my postings. Oct 5th, 2004 JDL |
#18
|
|||
|
|||
Jeff Findley wrote:
Catastrophic failure of liquid fueled engines is a "bad day" no matter how many engines are in your cluster. Note that a catastrophic failure of an F-1 engine on the S-1C stage or a J-2 on either the S-II or S-1VB stages would have been a "bad day" for an Apollo Saturn V. But assuming that the motors have an equal potential for catastrophic failure, the more motors you put on the vehicle, the more likely it is that one will catastrophically fail. Because of its large size, the F-1 probably had a greater potential for catastrophic failure than a NK-15, like the N-1's first stage used, but to get equal reliability in the overall booster stage, the NK-15 would have to be _six times_ as reliable as a F-1 in this respect...and I don't think that that was the case. Note also that for benign failures of liquid fueled engines, the Saturn V had a limited ability to continue with engines shut down, but that was only a possibility later in the stage burns, and wasn't a possibility at all for the S-1VB stage. In particular, loosing an F-1 engine early in the flight would have been very bad. Yes, it would result in a abort situation, but of course the four N-1 launches all resulted in abort situations before first stage burn was completed- and two of those abort situations (flights 2 and 4) could be directly related to problems with its first stage propulsion. Here's an article that mentions "Studies indicate that the immediate structural dynamic transients at engine-out will not cause structural failure. However, certain combinations of engine failure and wind direction and magnitude may result in a divergent control condition which could cause loss of the vehicle.": http://www.apollosaturn.com/s5flight/sec2.htm Here's an interesting article which talks about F-1 engine failure modes: http://www.system-safety.org/~journal/techarticle.html As you can see, the Saturn V, with fewer engines than the N-1, could also be destroyed by an engine failure, even if that failure wasn't "catastrophic" in and of itself. I'm still of the school that "the fewer the motors, the better" (which is one reason I like Delta 4 BTW- now watch... the sucker will blow on the pad :-) ) To me, it comes down to keeping things simple, rather than developing a complex system that can be failure tolerant. And it's hard to beat a single motor in this regard- but if you are going to cluster, then I'd draw the line at around six motors, as beyond that I think that the gains you get in not having to develop big motors are offset by increased plumbing weight and complexity, and a greater risk of having one of the motors fail in a way that will doom the vehicle. Back in the early days of jet engines, thought was given to simply clustering large numbers of small jet engines to power aircraft; but after the eight-engined B-52, the trend in both military and civilian aircraft has been to _minamize_ the number of motors needed for propulsion. Two is about the maximum you are going to see in future fighters and small and medium airliners, four in bombers and large airliners. I think there is a lesson there in regards to numbers vs. reliability. Further, the large number of motors that need to be manufactured for even a modest number of launches (the Soviets made a total of around fourteen N-1's, or at least had that many at some stage of construction although they only launched four- that's a total of 420 motors for the first stages alone, and a total of 588 if you count the basically similar second (8) and third (4) stage motors) means that you can't afford to do strenuous tests on the individual motors if you want to get up to a reasonable launch rate, and must minimize the man-hours spent on making each motor. Neither of those choices is going to add to the overall reliability of an individual motor. This seems to be an unfounded assertion. A higher manufacturing rate usually allows you to improve manufacturing in terms of repeatability, tolerances, and the like. You want to manufacture five turbopumps or 30 turbopumps? You can give more production care per turbopump to five rather than thirty....the Soviets weren't even test firing all the N-1s motors as they were produced, but rather just some from each production batch, on the assumption that if those worked alright, then the whole batch was good...which is fine until somebody incorporates a vodka bottle cap as a new design element into one of the motors. Manufacturing problems can easily happen when you have a very small, limited production run, which means that your need for "strenuous tests" is likely higher with a small run as compared to a very large run, where repeatability in the manufacturing processes has already been achieved. In the perfect world, yes...but in the real world every one of those motors is going to be at least a bit different from its sisters due to it's complexity, and when you are dealing with hundreds of them turned out in a fairly short period of time, at least one is going to be different in a fatal way. Sounds like "damning with faint praise" to me. The strenuous tests of the F-1 were required due to the small production run, and the high likelihood of the Saturn V being destroyed by an F-1 engine failure early in the flight. Jeff |
#19
|
|||
|
|||
Heinrich Zinndorf-Linker (zili@home) wrote:
[...] Oh, I'll back Henry. In the beginning the Russians did not really cluster large amounts of ENGINES - they clustered THRUST CHAMBERS. The original R-7 ICBM had 'only' five engines, but 32 thrust chambers in total. Don't get Henry started on this...he counts every thrust chamber as a rocket motor in its own right...we went round and round about this years ago. I argued that my car has four combustion chambers in it, but that doesn't mean it has four motors. Steer clear of hydrogen peroxide also- back in the 60's, Henry was a member of a engineering student revolutionary group that attempted to push the use of hydrogen peroxide in rockets, and were willing to resort to violence to achieve that end; the FBI files are full of incidents of solid rocket fuel production plants being put to the torch by the masked and bleached blonde members of The Superoxide Radicals. ;-) Pat |
#20
|
|||
|
|||
Derek Lyons wrote:
Nonsense. If you allow for testing/tweaking time in your manufacturing schedule and budget, it doesn't matter if you are making 10 motors or 10,000. Do you think you are going to have more man hours in five big motors and their plumbing or thirty medium sized ones? More man hours mean more possibility for mistakes. All of our manned moon landings (Apollos 11, 12, 14, 15, 16, 17) used the same number of F-1 motors as the number of NK-15's used in one N-1 first stage. If you have forever to make them, you can take time on each of the motors and check it out...but the 14 N-1's the soviets had finished or in construction meant they needed 420 motors for the first stages, and an additional 112 modified NK-15s for the second stages. That's 532 motors total, and that is a _lot_ to build and inspect. One thing that indicates the degree of confidence that the Soviets had in the N-1 was that they wanted a dozen successful unmanned launches before they were going to put a crew on it. Pat |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
The Apollo Hoax FAQ (is not spam) :-) | Nathan Jones | UK Astronomy | 8 | August 1st 04 09:08 PM |
The Apollo Hoax FAQ (is not spam) :-) | Nathan Jones | Astronomy Misc | 5 | July 29th 04 06:14 AM |
The Apollo Hoax FAQ | darla | Misc | 10 | July 25th 04 02:57 PM |
The Apollo Hoax FAQ | darla | UK Astronomy | 11 | July 25th 04 02:57 PM |
The Apollo Hoax FAQ | Nathan Jones | Astronomy Misc | 5 | November 7th 03 08:53 PM |