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Forum:	Publications & Multimedia
Topic:	British Interplanetary Society's Spaceflight

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Your Reply: HTML is ON UBB Code is ON Smilies Legend	[QUOTE]Originally posted by Robert Pearlman: [B] [QUOTE]Originally posted by dbaker: [b]Yes I have seen the comments made by Jim Oberg.[/b][/QUOTE] Jim has replied to David's response: <BLOCKQUOTE>Mr. Baker does not appear to understand the basis of my objections at all, let me try to make the points clearer. For point 1, he writes, "of course the right-ascension influences exactly when they pass but the fact that they do pass each other is admitted and a matter of fact." If Mr. Baker now is satisfied that the two vehicles are not and never will be co-planar, than this totally demolishes the significance he appears so enamored of - that the two inclinations happen to be very close. This demolition is caused by the fact that if criss-cross intercepts are all you are interested in [his new fall-back position, apparently], ANY two orbits of ANY plane will have exactly the same number - 2 per rev [so the coincidence of the orbital inclinations becomes moot]. Baker adds: "The velocity of the flyby does not hinder electronic diagnosis of Tiangong and associated ground facilities in China and Africa and this latter aspect is the point." Perhaps I need to study the original article further because I don't see the point. The undeniable ability of any space vehicle to carry out exactly such observations, from ANY low Earth orbit, totally dispels anything special about the X-37's orbit, and so the apparent central thesis of the article dissolves. In fact, the very closeness of the orbital period of X-37 and Tiangong makes the former vehicle an extremely inconvenient observer of Tiangong, especially in light of the obvious requirements it be observed during specific short intervals of special activities, such as docking. This inconvenience is related to the repeatability of the close passes, which as with the synodic period of planets, is defined as the reciprocal of the difference of the reciprocals of the two orbiting objects. For current values this runs about ten days between repeat passes (a pair of close passes every ten days). During most of the rest of that period the X-37B actually remains totally out of line-of-sight of Tiangong, in one of the BLINDEST POSSIBLE orbits for observation, not hardly the BEST possible orbit. For point 2, he writes that I "express[ed] incredulity that the US could have known the orbital inclination of Tiangong before it was launched (which was after X-37B)" This is an incorrect reading of my words leading to a misrepresentation of my objection. I expressed incredulity that the US could have predicted the orbital PLANE of Tiangong months before it was launched, not the orbital INCLINATION [it's possible some editor garbled this - I will check]. The plane depends both on the inclination, to be sure, as well as the Right Ascension of the Ascending Node, or RAAN. To achieve a co-planar orbit with Tiangong-1, which I surmised was the assertion of the to-appear article, would require prescience of a supernatural form to know the exact TIME it would be inserted into orbit, and hence define its RAAN. I had suspected from my interpretation of the BBC article that Mr. Baker was not conversant in the significance of the RAAN in determining orbit-to-orbit accessibility, and this new misunderstanding only underscores my original concern about his understanding of orbital mechanics.</BLOCKQUOTE>[/B][/QUOTE]
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