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Post by JayUtah on Jun 1, 2005 14:24:48 GMT -4
Let's try to reason with intelligence...We are. Your argument has no logic in it. You are simply begging the question of the LM's flight characteristics. You have provided no objective evidence that the LM was unstable, nor any expert opinion that the LM was unstable. There is simply no argument at all behind your conclusion. lunar modul is very unlike the Harrier.That is correct; the lunar module is easier to fly since there are no atmospheric interferences to contend with, since the LM's control is partially achieved through a computer, and since the lesser gravity necessitates less thrust and therefore lower rates derived from off-axis thrust. Astronauts had to learn to keep lunar module in hovering going backwards, not the Harrier.That is incorrect. The LM was not to be flown backwards. Under manual control the pilots stand vertically and face the direction of travel. It was considered extremely dangerous to attempt to fly the LM backward and so the flight profile called for forward drift only. Harrier has some rocket engines not one on the bottom.Both the Harrier and the LM use a peripheral reaction control system to achieve and maintain stability. Hovering on multiple jets is inherently less stable because roll and pitch rates are caused when the thrust of all jets is not perfectly balanced. Further, the Harrier's jets are gimballed, adding another variable to the control problem. Not only must thrust be precisely controlled in magnitude, it must also be controlled precisely in direction. Hey, don't rocket engines send forth smoke?Some do and some don't. The hydrazines, for example, under steady state combustion produce no smoke. LH2/LOX engines produce water vapor under some conditions, but under most daylight conditions do not produce a visible plume. Your photo is taken of the trainer lifting off. However, the normal flight profile calls for jet thrust only until test altitude has been reached. Then the jet is throttled back and the rocket engines are engaged to begin the training run. Your photo clearly shows the exhaust plume from the jet. But since the rocket would not have been ignited at this time, no exhaust from the rocket motor is expected. Here is a photo showing the LLTV with rocket exhaust. www.friends-partners.ru/partners/mwade/graphics/0/10074716.jpgHey, look at this imagePlease stick to the subject. We will deal with your arguments on Mars when we have made some headway on your contention that the LM was unflyable. So far you have argued that the problem is inherently unsolvable because balancing is hard. In response you were given scenarios in which balance is easier to achieve because the mass properties of the object were carefully controlled. You were also instructed that the "pendulum" or "Coke bottle" model of balancing is inapplicable to rocketry because of the single inertial reference. Finally you were given examples of working rockets from the 1930s and 1940s that solved this guidance problem. You argued that the LM was unflyable because insufficient computing power was available. You were given the example of helicopters, which can be flown by humans without computer control. You have also been given the example of the Harrier, which uses jet propulsion for VTOL and hovering and which -- despite being more difficult to fly because of the additional degrees of freedom -- can be flown by a human without computer control. I'm not sure what line of reasoning you intend to pursue by challenging the airworthiness of the LLTV. It seems you have no coherent argument and are just trying to engender meaningless uncertainty and doubt. LLTV flights were well-documented, witnessed, and filmed. There is no evidentiary question that they were airworthy.
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Post by martin on Jun 1, 2005 14:38:21 GMT -4
Let's try to reason with intelligence: Some will try, some will succeed. Martin
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Post by LunarOrbit on Jun 1, 2005 14:39:29 GMT -4
Unknown: 1) Please do not post such large images directly into the forum. It distorts the forum and requires people to side-scroll. 2) As I already said before, please stick to the topic. We are not talking about Mars here, it has nothing to do with Apollo.
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Bob B.
Bob the Excel Guru?
Posts: 3,072
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Post by Bob B. on Jun 1, 2005 14:59:26 GMT -4
As I posted earlier, the LLRV lift rockets, as well as thrusters, were fueled by hydrogen peroxide. I'm assuming they were mono-propellant decomposition engines.** Can anyone verify this? If so, the exhaust would have been nothing but water vapor and oxygen.
** Rather than bi-propellant with hydrogen peroxide as the oxidizer.
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Post by unknown on Jun 1, 2005 15:19:22 GMT -4
Today at 1:49pm, unknown wrote: Why? What a silliness is that. With a more powerful rocket engine LM could fly on the earth (even if it would roll like a balloon as on the moon).
Bob B. wrote: But that wouldn't be a valid test. A LM with a more powerful engine is no longer the LM that will land on the Moon, so what good is the test?
Hey, do you think you are speaking to an idiot? ;D
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Post by LunarOrbit on Jun 1, 2005 15:25:36 GMT -4
Do you really want an answer to that question?
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Post by unknown on Jun 1, 2005 15:35:17 GMT -4
JeyUtah wrote: You argued that the LM was unflyable because insufficient computing power was available. You were given the example of helicopters, which can be flown by humans without computer control. You have also been given the example of the Harrier, which uses jet propulsion for VTOL and hovering and which -- despite being more difficult to fly because of the additional degrees of freedom -- can be flown by a human without computer control.
I'm sorry but you don't understand anything about mechanics of forces. 1 - Helicopters are thrusted on the top and then it's quite easy to fly them. 2 - Harrier has some jet engines and for this reason it's quite easy to fly it (as 4 friends that lift a chair putting their forefingers under the legs).
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Post by martin on Jun 1, 2005 15:46:33 GMT -4
I'm sorry but you don't understand anything about mechanics of forces. 1 - Helicopters are thrusted on the top and then it's quite easy to fly them. There is a simple way for you to show to us your better knowledge of mechanics. You can put a rotor on the driving shaft of an engine, turn it on the side, and build your own helicopter. Even without control of individual blades of this rotor, it can be easy to fly since the rotor is at the top. Then you can show to us, how easy is it to fly. You can even win a Darwin award this year. Martin
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Post by sts60 on Jun 1, 2005 15:49:23 GMT -4
I'm sorry but you don't understand anything about mechanics of forces.
So far, you don't seem to understand even the most basic aspects of aerospace. (I've had plenty of opportunity to evaluate Jay's, BobB's, and others' understanding of the field, however.) You have yet to do anything other than wave your hands. When will you actually back up your claims with some evidence that the LM was unflyable, or demonstrate that you understand anything about flight? Or even just stop making fundamental mistakes?
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Post by JayUtah on Jun 1, 2005 16:01:03 GMT -4
Why? What a silliness is that.
It is not silliness at all. It is proper engineering. A machine must be optimized for its intended operational environment. Unnecessarily "polluting" the design for testing or other purposes compromises its overall safety and utility by adding unecessarily and probably uncontemplated interactions.
I make my living by designing things. What qualifies you to comment on appropriate design?
A submarine, for example, is meant to operate the water. But operating in the water is dangerous as it exposes the crew to hazards. It would be safer to test the submarine on land, or perhaps unmanned. However, adding terrestrial propulsion systems or providing for full automation introduces variables which do not contribute to the submarine's mission and which, for various reasons, might actually make the submarine's primary mission more dangerous.
If you solve that quandary by engineering two different submarines -- one for operational use and one that can be tested out of water -- then your test is invalid because the testing of one design does not validate some other different design.
There is inherent risk to testing. Mitigating that risk must be done, where possible, without violating the similitude of the test. It is useless to mitigate risk without considering the effect on testing validity.
With a more powerful rocket engine LM could fly on the earth (even if it would roll like a balloon as on the moon).
No.
The undercarriage cannot support the landing of an LM in Earth gravity. Therefore the undercarriage will have to be completely redesigned and replaced. This will alter the mass distribution of the LM, making it more bottom-heavy. That will alter the handling characteristics of the LM, and so the "test" version will not have the same handling as the flight version. That makes it unsuitable for pilot training.
The rest of the structure -- the cruciform descent stage and the cylindrical upper stage -- does not have sufficient strength to withstand a landing. It too would have to be strengthened, thereby increasing the overall mass of the vehicle and rendering its handling characteristics unfaithful to the original.
A "test" LM would have to fly in Earth's atmosphere, subjecting it to aerodynamic drag that need not be accounted for in the design of the flight version. And to preserve the lives of the test pilots in case of attitude excursions caused by air, an ejection system must be provided that is useless in the final design. The ascent stage structure must be modified to accept such a system, rendering it unfaithful to the original design as well as changing the mass of the vehicle.
Simply providing a more powerful motor does not work. The bigger engine would also be heavier, increasing the bottom-heaviness of the ship. Since all our previous modifications added mass, the engine would have to do more than account simply for the increased gravity of Earth. To feed that larger engine and thus produce appropriate thrust over the same length of time would require more than ten times the volume of fuel that the LM can carry.
And a more powerful engine produces more moment when its thrust is applied off-axis. This results in a flight dynamics situation considerably more dangerous than flying with a motor sized for lunar landing. In any case it is not a suitable simulation.
No. The LM simply cannot be adapted to fly in Earth gravity. And a vehicle built on the same geometrical principles as the LM, but sized for Earth gravity, would not have anywhere near the same handling characteristics as the lunar module and would be completely unsuitable for training purposes.
When faced with the dual problems of engineering validation and operator training, we engineers very frequently "decouple" them. This is what the Apollo engineers did. Initial concept studies provided an analytical view of how the LM was expected to behave dynamically. Once you know the approximate size, the approximate mass distribution, and the approximate size of the engines, you can produce machines that duplicate those effects in different environments. However, to produce the same effect under different operating conditions means you have to employ different physical principles than your operational system. That satisfies the need to train operators in a "safe" environment.
The LLTV did not require a spaceworthy airframe. It did not even require an aerodynamic airframe. Thus its airframe is designed solely for structural strength and efficiency. Whether you think it's "clunky" or unattractive is irrelevant. Its airframe is structurally sound and not very heavy. It is not ramshackle simply because your inexpert inspection suggests so.
The LLTV did, however, need to operate in a 9.8 N/kg gravitational field using a rocket sized for a 1.6 N/kg gravitation field in order that the off-axis rates could be accurately simulated. Thus the hybrid jet design, which was thoroughly unnecessary on the LM. All this was done to mimic the dynamic behavior of the LM, not its appearance or construction.
On the other side of the coin, to validate the engineering requires duplication of the environment. The LM engineering structures were subjected to the loads that were suggested by analytical discussion of the concept design. For space engineering this is sometimes difficult to do on Earth. Ideally we want to test in the absence of gravity loads. Thankfully we have become quite adept and designing test rigs that mitigate gravity or apply it in a direction irrelevant to the tests. These tests validate the analytical model of the vehicle's dynamics sufficiently to proceed to flight testing.
Propulsion systems, guidance systems, and peripheral systems can all be tested independently. Thus integration testing is required only to discover behaviors that arise from systemic interactions.
Thermal and vacuum effects can be simulated quite accurately on earth. It is possible to fit fully assembled spacecraft into vacuum chambers on Earth in which entire flight cycles are conducted in the absence of air. Further, these chambers are equipped with lamps that simulate the radiant heat loads of the sun. These tests validate that a design is workable in a space environment.
The LM was tested in unmanned flight test. The computer was programmed to conduct a simple sequence of tests to verify the analytical models upon which the other tests were based. If practical testing valiates the analytical models, then all conclusions derived from those models -- whether specifically tested or not -- can be considered reliable. Those analytical models also fed the design of operator test systems, therefore the behavior of the simulators can be approved by engineering test.
After concept testing, unit testing, integration testing, environment testing, and unmanned flight test, the vehicle is ready for manned flight test in space. The LM was meant to operate only in space, so testing in atmosphere is irrelevant. The vehicle's performance in air is not an issue. The LM was flight-tested in Earth orbit, with the CSM standing by in case of emergency. The LM was also flight-tested in lunar orbit, with the final test flight being that of Apollo 11 which flew the final untested 10,000 feet to the lunar surface.
This pattern of progressive test is actually conservative according to test methodology. Those who say the LM was never properly tested simply haven't studied much about test methodology and are naively trying to argue from irrelevant analogy ("X was tested a certain way, so the LM should also have been so tested") or intuition ("If I were testing it, I would have..."). Intuition rarely results in viable test strategies, and the LM was America's first space-only manned spacecraft; there was no precedent.
If engineering test validates the analytical models on which operator training aids were predicated, then the aids will give rise to sufficient operator proficiency even in the absence of "hands-on" training. In the LM's case those aids included the Langley crane, the LLTV, and computer-based cockpit simulation. Neither one can duplicate entirely the effects.
The LLTV provides realistic vehicle dynamics under gravity, but adds the unnecessary component of air turbulence. It is also expensive to operate and limited in the contingencies that could be tested. It is also somewhat dangerous.
The Langley crane is cheaper to operate and provides a more controlled scenario into which contingencies can be introduced at reduced risk.
The computer simulator manufactured by Link is the cheapest to operate, can be made in multiple copies, and affords the most opportunity for contingency training scenarios. It also offers the least risk and thus can be used often.
An operator who is already skilled in the general principles of flight and who has been conditioned to operating aircraft whose flight envelope is not well understood, and who has been trained according to these validated methods should have little difficulty operating the equipment.
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Post by unknown on Jun 1, 2005 16:04:05 GMT -4
Hey, more intelligent people than me, many persons say Americans never went to the moon.
There is an easy way to demonstrate the contrary: send one spy-satellite of yours in orbit around the moon and film your uncontaminated flag. But don't use Softimage, Maya, 3D Studio Max as usually please. ;D
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Bob B.
Bob the Excel Guru?
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Post by Bob B. on Jun 1, 2005 16:10:33 GMT -4
Bob B. wrote: But that wouldn't be a valid test. A LM with a more powerful engine is no longer the LM that will land on the Moon, so what good is the test? Hey, do you think you are speaking to an idiot? ;D You answer my question first. A LM modified to fly on Earth is longer the machine used to land on the Moon; therefore, what is learned about landing a LM on the Moon by performing this test? Your scenario is analogous to this: Let's say I'm designing a 3/4-ton pickup truck. But before I test it with a 3/4-ton load I strengthen the frame, beef up the suspension, and put a big engine in it to see if it can carry a 5-ton load. I've so modified the vehicle that the test tells me nothing about whether the original design is capable of performing the job it was designed to do. So what's the point?
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Post by LunarOrbit on Jun 1, 2005 16:31:48 GMT -4
See... that's the problem. You've already given yourself an excuse to ignore any satellite images of the landing sites, so why should we bother? If you are just going to claim the images are fake then there is no point in investing the millions of dollars required to take those pictures.
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Bob B.
Bob the Excel Guru?
Posts: 3,072
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Post by Bob B. on Jun 1, 2005 16:31:51 GMT -4
Mulitple posting is considered rude, not to mention immature. We all read your post the first time; there's no need to do it twice. Hey, more intelligent people than me, many persons say Americans never went to the moon. Yes, but find one who is a qualified scientist or engineer. Intelligence alone does not make one an expert in space science or engineering. [/b][/quote] Spending the taxpayers money to go prove something that all but a fringe few, like yourself, already believes is a total waste of resources. Answer this: If NASA sent a probe to the Moon and returned pictures of the landing sites showing the Apollo artifacts, would you believe it? Or would you just claim the new pictures are fakes as well?
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Post by JayUtah on Jun 1, 2005 16:32:17 GMT -4
I'm sorry but you don't understand anything about mechanics of forces.
I have diplomas that say otherwise. What are your qualifications?
Helicopters are thrusted on the top and then it's quite easy to fly them.
No. As I explained, a helicopter does not "hang" from its propulsion, nor does a rocket "sit on top" of its propulsion. The pendulum model for vertical propulsion is wrong. I have explained this numerous times. The helicopter, the Harrier, and a rocket couple the propulsion to the airframe in a single inertial reference. A rocket is no more inherently unstable than a helicopter.
Harrier has some jet engines...
I assume you mean it has multiple engines. Again, this does not make it easier to fly. It introduces another dimension of variability in the thrust that must be controlled by the pilot. The thrust must not only balance in magnitude in order to avoid pitch and roll, it must also balance in direction. This is one more degree of freedom than is provided in the lunar module.
...and for this reason it's quite easy to fly it
No. The Harrier is considered much more difficult to fly than a helicopter, precisely because its vertical thrust system is unforgiving.
Are you a pilot?
...as 4 friends that lift a chair putting their forefingers under the legs.
No. Again you wish to consider separate inertial references as equivalent to the scenario in which the propulsion is rigidly fixed to the airframe.
Let me explain the concept.
Imagine a standard pendulum clock. The pendulum hangs from its pivot and rocks back and forth. The pivot is fixed and held immovable against the force of gravity, while the pendulum is allowed to change its orientation around it in response to its dynamic situation (i.e, its momentum and the force of gravity acting over time). The motion of the pendulum requires its being reckoned according to the fixed pivot. The stability of a pendulum (i.e., its propensity to converge to a stationary equilibrium with respect to the pivot and to the room) is the result of the decoupling.
A rocket motor is rigidly fastened to the airframe and allowed to deflect with respect to it only in controlled ways, if at all. Thus with such a coupling no tendency toward equilibrium exists. A rocket-propelled vehicle that pitches or rolls will continue to do so until an opposing moment is applied. There is no propensity for such a vehicle to "rock" back to the vertical and thus no motivation to "hang" the vehicle from its propulsion. In the presence of gravity, however, the portion of the thrust that once was directed in opposition to gravity will be directed elsewhere, and gravity may accelerate the entire vehicle downward. But this is not "falling off" the thrust in the way that a Coke bottle falls off your finger.
It is more accurate to think of throwing a pendulum clock out of an airplane and contemplate the free-fall relationship of the pendulum and the clock together. The pendulum will not operate under those circumstances because the clock's ballistic trajectory places both the pivot and the pendulum in the same inertial reference frame.
This is the principle that governs the dynamics of rocket-propelled vehicles. The "hanging from the rotor" or "sitting on top of the thrust" concepts are very popular with laymen, but they do not accurately describe the dynamic behavior of a rocket in flight and are thus wrong.
I'll thank you kindly to stop smugly passing off layman's misconceptions as superior to the understanding of those of us here who are qualified to discuss rocket propulsion and guidance. I have given you these same answers twice, and you have completely sidestepped them. Kindly do not repeat your claims until you have demonstrated that you understand my statements.
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