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Antimatter Propulsion [pdf]

88 点作者 segfaultbuserr大约 1 年前

13 条评论

hermitcrab大约 1 年前
Summary, as I understand it:<p>-anti-matter is incredibly difficult to produce (the total produced so far in labs is about enough to boil 1 litre of water)<p>-anti-matter is incredibly expensive to produce (currently around 1 trillion USD per milligram)<p>-anti-matter is very difficult to store and manage<p>-a lot of the energy will be given off as high energy gamma rays, which will be difficult to convert into thrust<p>-the high energy gamma rays will be very destructive to the spacecraft and crew (biological or robotic) without lots of shielding<p>-over a ton of anti-matter would be required to get a ton of payload to a nearby star at ~40% the speed of light<p>So don&#x27;t start saving up for a ticket on an anti-matter spaceship. Or maybe do start saving, so your ancestors can take advantage of compound interest to buy a ticket in a few millenia, if we ever manage to develop the technology.
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at_a_remove大约 1 年前
If we had ham, we could have ham and eggs, if we had eggs. Another classic &quot;this will be easy as long as we have unobtanium&quot; concept.<p>I&#x27;ve been baffled, though, by the insistence on this kind of antimatter production. Antimatter production is inherently expensive because we are fighting conservation of baryon number, conservation of lepton number, et al.<p>Physics does have one theoretical method around this, which never seems to be addressed for these proposals, and that&#x27;s the baffling issue of black holes having no hair. You throw whatever past the event horizon, all that is conserved is mass, angular momentum, and charge. Baryon number, lepton number, strangeness ... all lost. Re-emission as Hawking radiation, it is thought, would simply be this sort of thing, redistributed without regard to what went in, so long as mass, angular momentum, and charge are accounted for. You would conceivably get out as much antimatter as matter.<p>Now, that&#x27;s worth looking at. And not from a &quot;we JUST need to capture an itty black hole&quot; (the word &quot;just&quot; does an enormous amount of lifting here) perspective. Rather, passage through the event horizon somehow strips off (we think, some think it might be preserved in some fashion) all of the variables which account for matter versus antimatter. And yet the event horizon isn&#x27;t a hunk of matter, it&#x27;s a ... membrane, a boundary, generated by matter at some distance (as a function of our usual three variables). Somehow, this warpage of spacetime operates on matter, shaving it so it has no hair.<p>That&#x27;s what fascinates me, in the sense of the theoretical having some extremely juicy practical results.
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master_crab大约 1 年前
Assuming it costs $10mil per mg in a highly efficient production scenario and you need 10^9 grams for “fast” interstellar travel means this probably isn’t doable.<p>I guess there’s just no getting around fact that an antimatter reaction that creates 9x10^10 MJ&#x2F;kg requires more robust electrical generation capabilities than we currently have (I.e fusion)
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jcul大约 1 年前
&gt; 1 banana produces a positron ~ every 75 minutes
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tomatotomato37大约 1 年前
I don&#x27;t get the placement of some of the technologies on the chart on page 5. How is pulsed fission being beaten out by both thermal fission and chemical rockets in terms of acceleration, considering for all intents and purposes that&#x27;s propulsion by nuclear detonation? And continuous fusion is all the way on the right despite being the basis of a torchship?? It all just seems so arbitrary
amai大约 1 年前
Unfortunately before we will develop an antimatter drive humanity will develop an antimatter bomb, see e.g. Yoko Tsuno, The time spiral: <a href="http:&#x2F;&#x2F;shareduniversereviews.blogspot.com&#x2F;2014&#x2F;04&#x2F;yoko-tsuno-la-spirale-du-temps-time.html" rel="nofollow">http:&#x2F;&#x2F;shareduniversereviews.blogspot.com&#x2F;2014&#x2F;04&#x2F;yoko-tsuno...</a>
hermitcrab大约 1 年前
It says:<p>&quot;Chemical combustion: ~ a few MJ&#x2F;kg • Solid Propellants: ~ 5 MJ&#x2F;kg • Liquid Propellants: ~ 1 MJ&#x2F;kg&quot;<p>Which doesn&#x27;t look right. My son (a rocketry enthusiast) tells me:<p>&quot;Liquid engines have energy density between 12 and 20MJ&#x2F;kg. Apparently they just left off the 0 and likely meant to put 10MJ&#x2F;kg&quot;
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bananapub大约 1 年前
obviously it&#x27;s not relevant to our interests for probably hundreds of years still, but it&#x27;s a very conceptually simple proposition:<p>1. antimatter is incredibly energy dense, so would be an excellent fuel.<p>2. there&#x27;s essentially none of it sitting around, so we need to make it, which takes lots of energy, but that&#x27;s fine - it&#x27;s an energy <i>transport</i> system, not an energy <i>production</i> system.<p>3. just set up square kilometers of solar panels in orbit around the sun or Mercury, use them to power particle accelerators which produce antimatter.<p>the sun emits enormous amounts of energy - we don&#x27;t need some magic new energy source, just magic new ways to temporarily bundle up energy in a dense form.<p>edit: someone did the maths[0]:<p>&gt; Where will we get the energy to run these magic matter factories? Some of the prototype factories will be built on Earth, but for large scale production we certainly don’t want to power these machines by burning fossil fuels on Earth. There is plenty of energy in space. At the distance of the Earth from the Sun, the Sun delivers over a kilowatt of energy for each square meter of collector, or a gigawatt (1,000,000,000 watts) per square kilometer. A collector array of one hundred kilometers on a side would provide a power input of ten terawatts (10,000,000,000,000), enough to run a number of antimatter factories at full power, producing a gram of antimatter a day.<p>from TFA:<p>&gt; Preliminary mission analysis:<p>&gt; - 10 kg instrument payload could be sent to 250 AU in 10 years using 30 mg of anti-H<p>&gt; - A similar probe could be sent to Alpha Centauri in 40 years using grams of anti-H<p>[0]: <a href="https:&#x2F;&#x2F;worldbuilding.stackexchange.com&#x2F;questions&#x2F;240278&#x2F;how-would-we-make-antimatter-in-industrial-quantities" rel="nofollow">https:&#x2F;&#x2F;worldbuilding.stackexchange.com&#x2F;questions&#x2F;240278&#x2F;how...</a>
antiquark大约 1 年前
Page 26 estimates the cost of antimatter production: six trillion dollars per milligram!
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GordonS大约 1 年前
This is absolutely fascinating, though this isn&#x27;t my field. Are any of the concepts presented feasible? Is mass-production of antiprotons on Earth realistic?
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Ziggy_Zaggy大约 1 年前
Wow, just wow. Great work being done at NASA.<p>Please don&#x27;t retire for another 10 years (or more).
pyinstallwoes大约 1 年前
So, what is antimatter?
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aimonster2大约 1 年前
Antimatter moves mass not space. Its a no-go because of all of the issues--time dilation? You need to move space, but we still haven&#x27;t found a way to fully create negative energy.
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