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Post by SevenOfCarina on Apr 28, 2017 11:13:44 GMT
Comet, mass of around 6.4 x 10^16 kg, impact velocity ~50 km/s. If 0.05 m/s of velocity change is needed to deflect it, and there are ~3 months to accelerate it (assuming it is detected ~7 months before impact), a thrust of >3 GN is demanded. For three whole months.
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Post by The Astronomer on Apr 28, 2017 11:20:50 GMT
Comet, mass of around 6.4 x 10^16 kg, impact velocity ~50 km/s. If 0.05 m/s of velocity change is needed to deflect it, and there are ~3 months to accelerate it (assuming it is detected ~7 months before impact), a thrust of >3 GN is demanded. For three whole months. 50 km/s!?! That's far too high! Is it really natural?
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Post by Enderminion on Apr 28, 2017 12:25:43 GMT
The Astronomer, the max speed something in sol orbit can hit the earth is 72km/s
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Post by The Astronomer on Apr 28, 2017 12:28:30 GMT
The Astronomer , the max speed something in sol orbit can hit the earth is 72km/s That has got to be seriously rare...
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Post by Enderminion on Apr 28, 2017 12:30:02 GMT
The Astronomer , the max speed something in sol orbit can hit the earth is 72km/s That has got to be seriously rare... on the extreme edge of the velocitys achivable in sol orbit so yes its VERY rare, also lets not leave out extrasolar rocks, they can move as fast as they effing want as long as its STL
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Post by The Astronomer on Apr 28, 2017 12:56:02 GMT
That has got to be seriously rare... on the extreme edge of the velocitys achivable in sol orbit so yes its VERY rare, also lets not leave out extrasolar rocks, they can move as fast as they effing want as long as its STL Make it a random weaponized alien rock XD
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Post by SevenOfCarina on Apr 28, 2017 13:43:48 GMT
The comet is in an inclined, extremely eccentric orbit. Hence the impact at fairly high latitudes, and the very short notice (I should probably lengthen it). I doubt there will be very many telescopes scanning for out of plane objects, considering the lower threat probability. If its coming from farther out, it would be cooler, and considering its mass, should develop a tail fairly late. Unless it has a high albedo, it can likely go undetected until a year or two before impact. Also, the impact velocity is 50 km/s. Not the orbital velocity of the comet. Considering the high impact angle, I expect Earth's orbital velocity would contribute a fair proportion to the impact velocity. Also, impacts of 100 km/s should be possible if the object is in a retrograde orbit.
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Post by newageofpower on Apr 28, 2017 15:50:40 GMT
The AstronomerThis is why asteroid deflection, especially with large bodies, should be done with lasers. Assuming conventional (i.e no improvements in tech from today on) pV efficiency, a 100 meter double-layer collector gathers 70-154 GW in Mercurian orbit. Assuming a very conservative 20% Molten Tin/Ce:LLF laser (nevermind a monstrous 70% efficient FEL) we can generate 14-30.8 GW of laser energy per array. IIRC lawson discussed the plausibility of slow roast entire cubic kilometers of space with laser energy in CoADE. Venusian asteroid diversion is for acquiring more resources, not to hit Earth. Why would you ever use NTR for long distance manouvers? Look at my 200 GW Passenger liner, featured by qswitched sama on his facebook page. It is horrifically unoptimized, created long before the amimai revolution in MPD theory. childrenofadeadearth.boards.net/post/7301/threadRegarding surface mining on Venus - you are underestimating the effects of a high pressure, corrosive, high heat environment. Electronics break down. High strength alloys and tools become as weak as putty. Power generation becomes a nightmare; the Venusian atmosphere is almost still at the surface, in addition to being super hot, high pressure, and corrosive. Replacement parts consume huge fractions of your industrial output. Sure, this can be mitigated. We have begun developing high temperature, high pressure electronics. Ceramic tools retain their strength even at high heats. Some of them can be made to resist corrosion from the Venusian atmosphere. You can design your automining robots to be pressure resistance. You can overclock your reactors and run their exhaust at spacecraft levels (and accept spacecraft levels of inefficiency) which would also require you to harden the entire mining robot against spacecraft heat exhaust, or tether power using multikilometer cables from a higher blimp station to the surface. All of this drives up cost. Cost is the bane of rapid industrial expansion. Even a half percent increase in industrial efficiency compounds to a lagging economy over decades - see Great Britain and America in the XX century. And with Venus's incredible, multilayer disadvantages for surface resource extraction? Double digit reductions in industrial growth.
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Post by The Astronomer on Apr 28, 2017 15:55:22 GMT
The Astronomer This is why asteroid deflection, especially with large bodies, should be done with lasers. Assuming conventional (i.e no improvements in tech from today on) pV efficiency, a 100 meter double-layer collector gathers 70-154 GW in Mercurian orbit. Assuming a very conservative 20% Molten Tin/Ce:LLF laser (nevermind a monstrous 70% efficient FEL) we can generate 14-30.8 GW of laser energy per array. What is it? I want to have it!!!
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Post by newageofpower on Apr 28, 2017 16:04:32 GMT
The Astronomer This is why asteroid deflection, especially with large bodies, should be done with lasers. Assuming conventional (i.e no improvements in tech from today on) pV efficiency, a 100 meter double-layer collector gathers 70-154 GW in Mercurian orbit. Assuming a very conservative 20% Molten Tin/Ce:LLF laser (nevermind a monstrous 70% efficient FEL) we can generate 14-30.8 GW of laser energy per array. What is it? I want to have it!!! Free Electron Laser. IIRC laboratory prototypes with efficiencies above 75% have already been built, but a continuous use, military/industrial/commercial system will probably be less efficient.
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Post by The Astronomer on Apr 28, 2017 16:14:09 GMT
What is it? I want to have it!!! Free Electron Laser. IIRC laboratory prototypes with efficiencies above 75% have already been built, but a continuous use, military/industrial/commercial system will probably be less efficient. Is it possible to mod this in? If possible, I'd like to organize a thread for it
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Post by newageofpower on Apr 28, 2017 16:22:58 GMT
Free Electron Laser. IIRC laboratory prototypes with efficiencies above 75% have already been built, but a continuous use, military/industrial/commercial system will probably be less efficient. Is it possible to mod this in? If possible, I'd like to organize a thread for it Uncertain. Like with Casaba tech, quite a bit of the math is classified/obscured.
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Post by SevenOfCarina on Apr 28, 2017 16:37:24 GMT
Apr 28, 2017 21:20:40 GMT 5.5 newageofpower said: -snip- No Gigawatt scale powersats in Mercury orbit or lower till impactor detection because ..... legal issues? Looks like I misunderstood your statement. Apologies. And yet it went from Earth to Mars in four months. I must have forgotten to mention 'bi-modal'. NTR when raising velocity to Earth escape, nuclear reactor for powering electric drives for constant-boost. Electric-drive only vessels are probably going to be unmanned tugs boosting payloads out of a gravity well. Regarding NTR/electric drive propellant, would hydrogen be feasable? Or is something like methane better? In the case of hydrogen, will boil-off losses be low enough to make storage facilities feasable? Or will water from Luna be shipped into orbit and split when needed? Yeah, I guessed that industrial mining on Venus wasn't going to work out. Frankly, I was thinking of something like a large tow cable lowered from floating habs to go snag some rocks and bring them up. Horribly inefficient though, and very limited. It probably wouldn't work anyway. Venus is hell. Except the cloud tops, of course. And I have my doubts about about those as well, what with the high concentrations of H2SO4. So, frankly, are multiple Venusian floating habs with a combined total population in the low thousands likely in a realistic setting? On a side note, why is it taking me an entire day to gather all the details for a single lousy ELE-impactor? Why must this OCD consume me?
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Post by newageofpower on Apr 28, 2017 16:59:51 GMT
HS resistance is not difficult on its own - just stacking all the other mitigation becomes problematic for surface mining. Venusian atmosphere means you receive less rads than on Earth, and the upper atmosphere is warmer and human-pressure. When your blimp city is not about to pass through a cloud of acid, you can put on an oxygen mask and go outside in a T-shirt.
It is the utopia of the solar system, -if- you can find the resources to live there, which is why I suggested asteroid diversion and orbital mining. Shipping resources to Venus is much easier than many bodies; the thick atmosphere makes dV gains from aerobreaking orders of magnitude higher than a Martian orbital insertion.
Regarding MPD/Nuclear hybrid craft, Hydrogen is horrifically undense, escapes through fuel tanks every day, requires gigantic tanks, and non-trivial reprocessing from most easily accessible sources. However, it offers insane exhaust velocities, and with techniques such as subcooling and double layer pumped tanks the loss can be mitigated.
I chose methane in my design because of its ridiculous availability on some sites (Titan, many comets), high density, and acceptable performance in both nuclear rockets and electric drive.
It is up to you to decide how easy subcooling is, how available double-layer polymer fiber-reinforced fuel tanks are, the industrial infrastructure set up to make either fuel... Hell, Venusian local craft might use CO2 based nuclear rocketry and remass; while lunar spacecraft use lunar dust electric drives and ISRU nuclear torches.
And our forum has yet to experiment with the Lithiun Hydrides...
Metallized hydrogen, of course, would be the ideal remass - if it is indeed metastable.
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Post by SevenOfCarina on Apr 28, 2017 17:04:42 GMT
Provided that the blasted stuff can actually remain solid when not under insane temperatures and pressures.
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