A kerosene-fueled X-33 as a single stage to orbit vehicle.
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From: Robert Clark on 25 Apr 2010 02:39 On this forum and in email correspondence the objection has been made to developing the SSTO that it would not be cost effective because two- stage-to- orbit systems could lift more payload. But in addition to dry mass being a key indicator of cost another key parameter of cost is complexity of the system. Single stages are inherently simpler than multi-stages so a SSTO would win on that scale. Moreover if the vehicle were to be a fully reusable two-stage system, then you would have the cost and complexity of making two separate winged vehicles. However, the SSTO can actually help if you wanted to get a TSTO to loft larger payloads. For instance I argued that the X-33, when kerosene fueled, could become orbital, though with small payloads, and the full-sized VentureStar could loft large payloads when kerosene fueled. However, the full-sized VentureStar would be quite expensive, in the billions of dollars range, while the X-33 would be about $360 million to build a new one. So the smaller X-33 could launch smaller payloads at an smaller initial investment. But quite key also is that using two of them as the first and second stages, they could now serve as a heavy launch system, and this would be at a much smaller investment than building the full-size VentureStar. Note also the comparison to a two-stage expendable system: the two stages in such a case would be expendable because they don't have sufficient mass ratio to singly get to orbit. That is they aren't weight optimized. But suppose you were able to make each stage be so optimized that each separately could reach orbit at the same size vehicles. Then now note this means these weight optimized versions could therefore loft *more* payload because the weight savings could go to extra payload AND would be less costly per launch in being reusable. This then would be a key advantage of making a small reusable orbital launcher as I maintain the X-33 can be when kerosene fueled. For your early forms of two-stage to orbit expendable systems, you might want to save on development costs, and just get it done easily by not optimizing it for weight. But IF at some later time you do have the technological development to so weight optimize the stages so they can each be reusable and separately orbital, then you make better BOTH your payload and your costs to orbit. Bob Clark
From: Robert Clark on 25 Apr 2010 11:35 On this forum and in email correspondence a question was asked if this is so easy then why isn't it being done by the aerospace companies or national space programs around the world? A great book to read is: The Structure of Scientific Revolutions. by Thomas Kuhn http://en.wikipedia.org/wiki/The_Structure_of_Scientific_Revolutions Kuhn explained how scientific progress in historical cases had been hampered by scientists having intellectual blinders on. Their understanding of how things worked was directed by what paradigm they were working under. A very good summary of Kuhn's theories is provided in this obituary of him in the New York Times: The New York Times, June 19, 1996, p. B7. Thomas Kuhn, 73; Devised Science Paradigm [Obituary] By Lawrence Van Gelder "Professor Kuhn argued in the book that the typical scientist was not an objective, free thinker and skeptic. Rather, he was a somewhat conservative individual who accepted what he was taught and applied his knowledge to solving the problems that came before him. "In so doing, Professor Kuhn maintained, these scientists accepted a paradigm, an archetypal solution to a problem, like Ptolemy's theory that the Sun revolves around the Earth. Generally conservative, scientists would tend to solve problems in ways that extended the scope of the paradigm. "In such periods, he maintained, scientists tend to resist research that might signal the development of a new paradigm, like the work of the astronomer Aristarchus, who theorized in the third century B.C. that the planets revolve around the Sun. But, Professor Kuhn said, situations arose that the paradigm could not account for or that contradicted it." http://www.des.emory.edu/mfp/kuhnobit.html In the case of SSTO vehicles the paradigm is that any SSTO if it is to be possible must be done by hydrogen because it is regarded as the most "advanced" propellant. Therefore the times that SSTO has been attempted using hydrogen and failed, reinforces the conclusion it is technically very difficult or in fact can't be done. Then the great majority of scientists and engineers in the industry who don't work with hydrogen because of its complexity have the idea an SSTO does not apply to them and won't even investigate it. They get the impression just like the engineers who do work with hydrogen-fueled engines that "if it can't be done using the most advanced fuel, that means it can't be done." It is understandable how this idea arises. Hydrogen is the best on the most important parameter of Isp. However, because Isp is the most important parameter does not mean the other parameters don't have influence. Other quite key parameters are engine thrust/weight ratio and propellant tankage ratio. Hydrogen is better than kerosene in Isp by a factor of about 1.25 to 1. But kerosene is better than hydrogen in engine thrust/weight by about 2 to 1 and in propellant tankage ratio by about 3 to 1. The advantage of kerosene in these other key parameters swamps the Isp advantage offered by hydrogen, so much so that switching from a hydrogen-fueled SSTO to a kerosene-fueled one results in multiple times greater payload. But SSTO's using kerosene will soon be attempted. It's advantage is just too blatantly apparent. When it is and it succeeds, it will be astonishing how easy it was. And scientific philosophers will have another example of how a too strongly held paradigm limited the progress of science. Bob Clark
From: Androcles on 25 Apr 2010 12:02 "Robert Clark" <rgregoryclark(a)yahoo.com> wrote in message news:263a92a7-c623-4eaf-9472-143c2f83c7c4(a)11g2000yqr.googlegroups.com... > On this forum and in email correspondence a question was asked if > this is so easy then why isn't it being done by the aerospace > companies or national space programs around the world? > > A great book to read is: > > The Structure of Scientific Revolutions. > by Thomas Kuhn > http://en.wikipedia.org/wiki/The_Structure_of_Scientific_Revolutions > > Kuhn explained how scientific progress in historical cases had been > hampered by scientists having intellectual blinders on. Their > understanding of how things worked was directed by what paradigm they > were working under. > A very good summary of Kuhn's theories is provided in this obituary of > him in the New York Times: > > The New York Times, June 19, 1996, p. B7. > Thomas Kuhn, 73; Devised Science Paradigm [Obituary] > By Lawrence Van Gelder > "Professor Kuhn argued in the book that the typical scientist was not > an objective, free thinker and skeptic. Rather, he was a somewhat > conservative individual who accepted what he was taught and applied > his knowledge to solving the problems that came before him. > "In so doing, Professor Kuhn maintained, these scientists accepted a > paradigm, an archetypal solution to a problem, like Ptolemy's theory > that the Sun revolves around the Earth. Generally conservative, > scientists would tend to solve problems in ways that extended the > scope of the paradigm. > "In such periods, he maintained, scientists tend to resist research > that might signal the development of a new paradigm, like the work of > the astronomer Aristarchus, who theorized in the third century B.C. > that the planets revolve around the Sun. But, Professor Kuhn said, > situations arose that the paradigm could not account for or that > contradicted it." > http://www.des.emory.edu/mfp/kuhnobit.html The current paradigm, "light is always propagated in empty space with a definite velocity c which is independent of the state of motion of the emitting body" leads to paradox and no research into high speed interplanetary communications. If the Earth-Moon system moves around the Sun and the speed of light remains c in the empty space then the laser ranging light will take longer to reach and return from the Moon at quarter moon than it will at full moon or new moon. Einstein is the modern day Ptolemy, and as Newton said of Ptolemy, so I echo of Einstein. [Einstein Ptolemy] developed certain astronomical theories and discovered that they were not consistent with observation. Instead of abandoning the theories, he deliberately fabricated observations from the theories so that he could claim that the observations prove the validity of his theories. In every scientific or scholarly setting known, this practice is called fraud, and it is a crime against science and scholarship. He even boasted of it. "If the facts don't fit the theory, change the facts." - Einstein. And you concern yourself with fossil fuel? Phooey. > In the case of SSTO vehicles the paradigm is that any SSTO if it is to > be possible must be done by hydrogen because it is regarded as the > most "advanced" propellant. Therefore the times that SSTO has been > attempted using hydrogen and failed, reinforces the conclusion it is > technically very difficult or in fact can't be done. Then the great > majority of scientists and engineers in the industry who don't work > with hydrogen because of its complexity have the idea an SSTO does not > apply to them and won't even investigate it. They get the impression > just like the engineers who do work with hydrogen-fueled engines that > "if it can't be done using the most advanced fuel, that means it can't > be done." > It is understandable how this idea arises. Hydrogen is the best on the > most important parameter of Isp. However, because Isp is the most > important parameter does not mean the other parameters don't have > influence. Other quite key parameters are engine thrust/weight ratio > and propellant tankage ratio. Hydrogen is better than kerosene in Isp > by a factor of about 1.25 to 1. But kerosene is better than hydrogen > in engine thrust/weight by about 2 to 1 and in propellant tankage > ratio by about 3 to 1. The advantage of kerosene in these other key > parameters swamps the Isp advantage offered by hydrogen, so much so > that switching from a hydrogen-fueled SSTO to a kerosene-fueled one > results in multiple times greater payload. > But SSTO's using kerosene will soon be attempted. It's advantage is > just too blatantly apparent. When it is and it succeeds, it will be > astonishing how easy it was. > And scientific philosophers will have another example of how a too > strongly held paradigm limited the progress of science. > > > Bob Clark
From: hcobb on 25 Apr 2010 12:32 There already is a single stage to orbit vehicle in the sense that the Shuttle uses the same main engines from launch pad to orbit and the only part thrown away is a simple fuel tank. How's that single-stagy, reusey thing working out for you? -HJC
From: J. Clarke on 25 Apr 2010 12:43
On 4/25/2010 12:02 PM, Androcles wrote: > "Robert Clark"<rgregoryclark(a)yahoo.com> wrote in message > news:263a92a7-c623-4eaf-9472-143c2f83c7c4(a)11g2000yqr.googlegroups.com... >> On this forum and in email correspondence a question was asked if >> this is so easy then why isn't it being done by the aerospace >> companies or national space programs around the world? >> >> A great book to read is: >> >> The Structure of Scientific Revolutions. >> by Thomas Kuhn >> http://en.wikipedia.org/wiki/The_Structure_of_Scientific_Revolutions >> >> Kuhn explained how scientific progress in historical cases had been >> hampered by scientists having intellectual blinders on. Their >> understanding of how things worked was directed by what paradigm they >> were working under. >> A very good summary of Kuhn's theories is provided in this obituary of >> him in the New York Times: >> >> The New York Times, June 19, 1996, p. B7. >> Thomas Kuhn, 73; Devised Science Paradigm [Obituary] >> By Lawrence Van Gelder >> "Professor Kuhn argued in the book that the typical scientist was not >> an objective, free thinker and skeptic. Rather, he was a somewhat >> conservative individual who accepted what he was taught and applied >> his knowledge to solving the problems that came before him. >> "In so doing, Professor Kuhn maintained, these scientists accepted a >> paradigm, an archetypal solution to a problem, like Ptolemy's theory >> that the Sun revolves around the Earth. Generally conservative, >> scientists would tend to solve problems in ways that extended the >> scope of the paradigm. >> "In such periods, he maintained, scientists tend to resist research >> that might signal the development of a new paradigm, like the work of >> the astronomer Aristarchus, who theorized in the third century B.C. >> that the planets revolve around the Sun. But, Professor Kuhn said, >> situations arose that the paradigm could not account for or that >> contradicted it." >> http://www.des.emory.edu/mfp/kuhnobit.html > > > The current paradigm, "light is always propagated in empty space with a > definite velocity c which is independent of the state of motion of the > emitting body" leads to paradox and no research into high speed > interplanetary communications. > If the Earth-Moon system moves around the Sun and the speed of light remains > c in the empty space then the laser ranging light will take longer to reach > and return from the Moon at quarter moon than it will at full moon or new > moon. > Einstein is the modern day Ptolemy, and as Newton said of Ptolemy, so I echo > of Einstein. > [Einstein Ptolemy] developed certain astronomical theories and discovered > that they were not consistent with observation. Instead of abandoning the > theories, he deliberately fabricated observations from the theories so that > he could claim that the observations prove the validity of his theories. In > every scientific or scholarly setting known, this practice is called fraud, > and it is a crime against science and scholarship. > > He even boasted of it. "If the facts don't fit the theory, change the > facts." - Einstein. > > And you concern yourself with fossil fuel? Phooey. Oh, to Hell with it. <plonk> |