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#61
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Towards routine, reusable space launch.
On Jun/15/2018 at 11:34 PM, Fred J. McCall wrote :
JF Mezei wrote on Fri, 15 Jun 2018 22:13:01 -0400: On 2018-06-15 19:21, Alain Fournier wrote: Yes. But I think I am a little less optimistic than you about it becoming practical in the future. If we have fantastic materials in the future, maybe an elevator will become more practical, Apart from lifting geostationary satellites to just below orbit and then let them use their own thrusters to position to their assigned slot/longitude, what other use would a space elevator have ? You go above the GEO point on the cable and get flung on interplanetary trajectories. Yes! You would also likely put at least one cable above GEO rotating in a plane perpendicular to the main cable. So you can give an extra push for interplanetary trajectories and to fine tune in which direction you depart for said trajectories. You can also jump off at an altitude of about 15000 km (that figure is from the top of my head, it might be more or might be less). From there after a few passes of aero-braking you can reach LEO with very small thrusters. For polar orbits, you use the rotating cable above GEO mentioned above. But instead of using it for extra push you get off while it is subtracting some speed but not quite in the direction of rotation of the cable. So you subtract some speed in the direction of rotation of the cable and give some speed in the north-south axis. You then use aero-braking again to lower apogee, and a small thruster to raise perigee. Note however that using the elevator to reach polar orbits in this way isn't obvious. You would want a long and fast rotating cable and you would want it far above GEO, it might not be practical to do so. Building an elevator, with current technologies, is outrageously expensive. But if you have one, it can be very useful. Alain Fournier |
#62
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Towards routine, reusable space launch.
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#64
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Towards routine, reusable space launch.
On Jun/16/2018 at 10:06 AM, Jeff Findley wrote :
In article , says... how about a Space Slingshot ? A fool and his money are soon parted. They're not getting enough money to actually develop and build the thing. They're raised what $40 million or something? They'll need a hell of a lot more than that to turn their design into a reality. Are you two talking about SpinLaunch? If no, what do you mean by Space Slingshot? Alain Fournier |
#65
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Towards routine, reusable space launch.
In article , says...
On Jun/16/2018 at 10:06 AM, Jeff Findley wrote : In article , says... how about a Space Slingshot ? A fool and his money are soon parted. They're not getting enough money to actually develop and build the thing. They're raised what $40 million or something? They'll need a hell of a lot more than that to turn their design into a reality. Are you two talking about SpinLaunch? If no, what do you mean by Space Slingshot? That was my guess. I personally don't think SpinLaunch is viable, at least not without a heck of a lot of development. G loads will be pretty crazy, so you can't use it for much except bulk cargo. Jeff -- All opinions posted by me on Usenet News are mine, and mine alone. These posts do not reflect the opinions of my family, friends, employer, or any organization that I am a member of. |
#66
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Towards routine, reusable space launch.
On Jun/16/2018 at 1:57 PM, Jeff Findley wrote :
In article , says... On Jun/16/2018 at 10:06 AM, Jeff Findley wrote : In article , says... how about a Space Slingshot ? A fool and his money are soon parted. They're not getting enough money to actually develop and build the thing. They're raised what $40 million or something? They'll need a hell of a lot more than that to turn their design into a reality. Are you two talking about SpinLaunch? If no, what do you mean by Space Slingshot? That was my guess. I personally don't think SpinLaunch is viable, at least not without a heck of a lot of development. G loads will be pretty crazy, so you can't use it for much except bulk cargo. On Feb/25/2018 at 11:32 AM, (In sci.space.policy) I wrote: "I might be wrong but I suspect those proposing SpinLaunch are aware of the problems. Their business plan is probably more about collecting investors money than about putting anything in orbit." I haven't seen anything since that would make me change my mind about that. So they aren't going to get any investment money from you and I. Alain Fournier |
#67
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Towards routine, reusable space launch.
JF Mezei wrote on Sat, 16 Jun 2018
17:51:21 -0400: On 2018-06-16 10:38, Jeff Findley wrote: They already built the thing and it's stitting inside a tent at the BFR/BFS production facility: Just because they already built it doesn't negate the potential for them to have needed breaktrough to scale this not only for size but also repeated cryo load/unload cycles. Yes, they could always discover that magical unicorns are attracted to it to **** on it and that breaks it, but having run full pressure tests and burst tests that's pretty damned unlikely. Just because they built test articles using conventional stuff available from yor local hardware store doesn't mean that the final product will not be highly propriettary with new version of fibres and resin. Yes, because engineering organizations always build **** that isn't representative of what they're actually building. Quickly building one with available composites allows them to make initial tests on strength and then do the fatique tests quickly, see if/how it fails and then develop what is needed to make this long lasting tanks. Not how engineering works. Can you really be this clueless? The fact that SpaceX is tight lipped about how it built its tanks points to them already beyond using already commercial available materials and process. There is more to a picture of a mandrel in making a large composite cylinder. Hogwash! Also note: neither SpaceX nor orbital ATK have this in production yet. Either could hit stumbling blocks on the way. Yes, and monkeys might fly out your butt. Using composite for room temperature + very hot SRBs is not the same as a tank that goes from room temperature to very cold in cryo to very hot once expose to sun in space. What makes you think the case on an SRB gets all that hot? Tanks only get exposed to sun in space if you plan on peeling the shell of the spacecraft off. I don't know of any spacecraft that do that. -- "Ignorance is preferable to error, and he is less remote from the truth who believes nothing than he who believes what is wrong." -- Thomas Jefferson |
#68
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Towards routine, reusable space launch.
In article ,
says... On 2018-06-17 05:16, Fred J. McCall wrote: Not how engineering works. Can you really be this clueless? Engineering tries to PREDICT how a structure will behave. snip? I snipped the rest of your rambling post. You really should stop telling engineers how you think engineering works. Also, you act like they've done zero cryogenic testing on this composite cryogenic tank design. This is utterly false. Here is a cite from Composites Manufacturing Magazine: SpaceX Successfully Tests Carbon Fiber Tank for Mars Spaceship Evan Milberg, November 29, 2016 http://compositesmanufacturingmagazi...-successfully- tests-carbon-fiber-tank-mars-spaceship/ You seem to keep assuming SpaceX engineers don't perform any sort of ground testing and just "wing it" every time they fly. The facts do not support that assertion. Note also that this article was from November 29, 2016. It's quite likely SpaceX has performed other tests between then and now, nearly two years later. But, since they're a private company, they don't *have* to tell us anything, now do they? Jeff -- All opinions posted by me on Usenet News are mine, and mine alone. These posts do not reflect the opinions of my family, friends, employer, or any organization that I am a member of. |
#69
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Towards routine, reusable space launch.
JF Mezei wrote on Sun, 17 Jun 2018
15:49:50 -0400: On 2018-06-17 05:16, Fred J. McCall wrote: Not how engineering works. Can you really be this clueless? Engineering tries to PREDICT how a structure will behave. Like I said, not how engineering works. You really don't understand any of this except in the most simplistic ways, do you? snip idiocy -- "Ignorance is preferable to error, and he is less remote from the truth who believes nothing than he who believes what is wrong." -- Thomas Jefferson |
#70
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Towards routine, reusable space launch.
JF Mezei wrote on Mon, 18 Jun 2018
02:44:03 -0400: On 2018-06-17 16:52, Jeff Findley wrote: Also, you act like they've done zero cryogenic testing on this composite cryogenic tank design. This is utterly false. Here is a cite from Composites Manufacturing Magazine: I mentioned that they built one, filled it succesfully, then destructively tested it to see at what pressure it failed. I did not ignore this. The article you linked is older and doesn't mention the destructive test SpaceX did (which I mentioned). You also claimed that what they built and tested wasn't representative of what they intend to build as a final article and fly, which is just a stupid assertion. These tests do not mean the tank is ready. There are other tests they need to do, in particulat measure how many fill/empty cycles can be made before flaws start to appear. And if that number if below expectations, fix the design to add longevity. This is a normal part of development. Nothing nefarious about it. But just because they did 2 tests doesn't mean that they did all the tests. Just because they only told you about two tests doesn't mean they didn't do any others. You seem to keep assuming SpaceX engineers don't perform any sort of ground testing and just "wing it" every time they fly. The facts do not support that assertion. I was responding to McCall who claimed engineers can build stuff that works (in response to my arguments they need to test to validate the designs and in doing so, can possibly find problems that need to be fixed. Apparently your deficiency in knowledge of engineering is only surpassed by your defective English skills, since I said no such thing. My responses were replies to your massively stupid assertion that they just built any old tank and tested that without any idea at all of what they're actually going to build. -- "Ordinarily he is insane. But he has lucid moments when he is only stupid." -- Heinrich Heine |
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