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Scientists to unveil new Earth-like planet
- deleted 10y ago[deleted]
- tootie 10y agoProject Longshot estimates 100 years to reach Alpha Centauri B. And that's assuming we launch tomorrow. Add 4 years to receive the telemmetry. https://en.wikipedia.org/wiki/Project_Longshot https://en.wikipedia.org/wiki/Project_Longshot
- Retric 10y agoThat's ~1000 times the velocity of our fastest probe so far when you exclude gravity assist. Stopping at the other end doubles travel time.
- pavel_lishin 10y agoWould it be possible to drop off a much lighter package at the destination and use a solar sail to slow it down? We don't need to slow down a big interstellar engine when we get there; let it keep falling into space, while the instrument package slows down. It could even have a smaller engine of its own; it'll take a lot less time to slow down something that's 10-1% the weight of the entire package.
- Retric 10y agoA solar sail can add or subtract around ~60km/second which seems fast, but this is looking at 13411km/sec so not really that useful.
- pavel_lishin 10y agoThat doesn't seem right; that would mean it would take about four minutes to slow to zero.
- Retric 10y agoSpeed is distance / time, acceleration and deceleration is distance / time ^2. If you accelerate at say 9.8 m/s^2 for 1 second that's 9.8 m/s/s * 1s = 9.8m/s aka if you fall for 1 second your going 22 miles per hour and still being pulled down at 9.8m/s/s. Using a star a solar sail can change it's speed by ~60km/sec by accelerating much much slower than that for months. The problem is the further from a star get the lower your acceleration. To maximize final speed you basically want to get as close to the star as you can in a huge elliptical orbit and then on your final pass just keep accelerating. Or do the reverse on the way back. Is that clear?
- x1798DE 10y agoI don't understand the units here. Surely a solar sail causes acceleration or deceleration, so its contribution would be in m/s^2, not m/s.
- stouset 10y ago60km/s not the acceleration. It's the total contribution to delta-V over a long period of time.
- x1798DE 10y agoWhy is there a total amount of change in velocity possible from solar sails? Shouldn't it depend on the mass of the thing being accelerated, amount of time under acceleration, etc?
- Retric 10y agoThe further from the sun you get the less acceleration you get from the sun. So, 4x the acceleration = 2x the speed because your accelerating for 1/2 the time and 1,000,000x acceleration = 1,000x the speed. Further, the input power is fixed from the sun so the absolute best you could do would be 100% sail that's a single atom thick. However, that sail would be quickly destroyed by the sun and other things. Make an ultra thin sail with a tiny little cargo Say 98% weight of the sail and 2% cargo and dropping the cargo below that does not help much. You end up getting around 60km / second which is really really fast 1km/s = fast sniper bullet. But, we are comparing it to something going 4% of light speed which is insanely fast.
- lucb1e 10y ago> Stopping at the other end doubles travel time. Wow, I knew the physics but never realized the implication: where on earth hitting the brakes is easy and costs next to zero energy, in space breaking takes just as much energy as accelerating.
- danpalmer 10y agoIf you like science fiction, I recommend reading The Algebraist by Iain M Banks - this mechanic features frequently in the story and is quite a core limitation in the galactic civilisation he describes, which results in some interesting outcomes.
- lucb1e 10y agoSounds cool, I'll check it out. Thanks for the recommendation!
- soneil 10y agoI know it's a game, but Kerbal Space Program really helped hammer home a lot of the things I guess I understood in the abstract. Delta-V is Delta-V. Every change in velocity (ignoring external influences) is cost out of the same budget. Braking is just accelerating in the opposite direction.
- fbonetti 10y agoBefore I played KSP I had a lot of hilarious misconceptions about the physics of rocketry and space travel. On my first attempt to get into orbit, I loaded up my rocket with as many engines and boosters as I could strap on and fired the rocket straight up. The rocket breached the atmosphere but to my surprise the rocket came straight back down. I literally thought that launching rockets into orbit meant shooting them really high until they were "in space" haha. I then quickly learned that being in orbit means having a horizontal momentum that is balanced with the gravitational pull of a given body. This balance produces a curved elliptical trajectory.
- 10y ago
- tootie 10y agoWould it double? Couldn't they use the gravity of Alpha Centauri to pull it into orbit?
- Retric 10y agoNot out to five decimal places, at those speeds you would actually run into a fair amount of stuff in the near vaccume of space and you lose some delta V escaping the Suns gravity well etc. But relative to all the unknowns it's about a 200 year trip vs a 100 year trip. If everything else worked about as well as expected. Another consideration is if rocket stops working after 10 years on a fly by you still eventually fly by the general area, but if you want to stop well that's just not happening.
- calgoo 10y agoProject Starshot wants to reduce that to 20 years. [1] http://www.skyandtelescope.com/astronomy-news/100-million-for-probes-to-alpha-centauri-yes-really/ http://www.skyandtelescope.com/astronomy-news/100-million-fo... [2] http://www.space.com/32546-interstellar-spaceflight-stephen-hawking-project-starshot.html http://www.space.com/32546-interstellar-spaceflight-stephen-...
- T-A 10y agoStarshot estimates 20-30 years for a flyby probe (or, more likely, a swarm of them)... starting a few decades from now: https://en.wikipedia.org/wiki/Breakthrough_Starshot https://en.wikipedia.org/wiki/Breakthrough_Starshot
- scotty79 10y agoThese guys want to reach Alpha Centauri in 20 years http://www.sciencealert.com/stephen-hawking-and-a-russian-billionaire-want-to-send-tiny-spacecraft-to-alpha-centauri http://www.sciencealert.com/stephen-hawking-and-a-russian-bi...
- pmiller2 10y agoWell, according to the wiki article you cited, the 100 years figure is assuming a 3 order of magnitude improvement in propulsion technology. We've barely advanced since the project was conceived, so I'd say it'd probably be closer to 100,000 years instead.
- jagger27 10y agoI wonder if the James Webb Space Telescope will be able to image it since it's so close.
- danpalmer 10y agoCan anyone "do the maths" on this. I don't feel well enough equipped, but I'd love to know the feasibility of this, or what we would be able to image if anything.
- cnvogel 10y agoA planet the size of the earth at the distance of proxima centauri is about 6.582⋅10^-5 arcseconds wide (a 20'000th of an arcsecond) angle(in degrees) = size / distance / pi ⋅ 180°, take times 3600 for arc seconds https://www.wolframalpha.com/input/?i=(diameter+of+the+earth)%2F(distance+to+proxima+centauri)+%2F+pi+*+180+*+3600 https://www.wolframalpha.com/input/?i=(diameter+of+the+earth... I didn't find a easy round number for James Webb, but Hubble's angular resolution is 1/10th of an arcsecond, at least a factor 2000 too low to even resolve the planet's disk as one pixel. https://www.spacetelescope.org/about/faq/ https://www.spacetelescope.org/about/faq/
- dalke 10y agohttp://jwst.nasa.gov/faq_solarsystem.html#angularresolution http://jwst.nasa.gov/faq_solarsystem.html#angularresolution says: > The specification is that the telescope is diffraction limited at 2 μm, which means a Strehl ratio of 0.8 and a wavefront error of 150 nm rms. With a 6.5 m telescope, 1.22 λ/D = 0.077 arcsec at 2 μm. The smallest pixels (NIRCam 0.6-2.5 μm) are just 0.034 arcsec. But a lot of the wavefront error is due to imperfect alignment of the parts, and it's possible to do better for a small part of the field of view. A telescope can still detect something smaller than its resolution. We can see stars with our eyes, after all. Even astronauts in space, where there is no atmosphere to move the light around. Here are some of the best attempts at direct imaging with a telescope: http://www.planetary.org/explore/space-topics/exoplanets/direct-imaging.html http://www.planetary.org/explore/space-topics/exoplanets/dir... The problem is the planet is dim and close to a bright star. If this planet is 1 AU out, then there's a 0.77 arcsec between it and the the star, which would make it easier to distinguish the two.
- dTal 10y agoThis is extremely exciting! The million dollar question is of course "how Earth-like?". If the answer is "very" we might actually have found a viable place for an off-world colony! Getting a probe there in a reasonable time is entirely feasible if can figure out how to keep the darned thing accelerating without stupendous fuel requirements. I'm confident we'll figure that out sooner or later.
- denim_chicken 10y agoKeep dreaming. If we cannot even understand or live in accordance with the life support systems of what is literally the most habitable and human-friendly planet in the Universe then there's no way in hell that we will be able to successfully colonize a lifeless planet. Stop thinking about outer space when we are in the middle of an anthropogenic mass extinction here on planet Earth.
- pavel_lishin 10y ago> literally the most habitable and human-friendly planet in the Universe Well, we don't know that it's the most habitable; it's just the most habitable we know of. And huge sections of it are completely unsuited for human life. 2/3rds of it will kill a human being in a matter of hours. Anything above or below, let's call it 50 degrees latitude is inhospitable without technology, and the equator isn't a great place to live, either.
- matroosberg 10y agoIt almost certainly is the most habitable planet for life as we know it today because we and our environment co-evolved to match the conditions. Just because 2/3 of the planet (not sure how you arrived at the number / what parts are in the denominator) doesn't meant it is meaningless to what allows us to live here (e.g., oxygen and food supply from the oceans). OTOH I disagree with the notion that we have to have a full grasp on how to sustain us on this planet before we can make other planets inhabitable for us. I think there are things we will only learn if we try. I am not saying that trying right now is feasible, though.
- digdigdag 10y agoI don't think there are electronic or software components today that can withstand interstellar space travel for thousands of years, even at the distance of proxima centauri. Distance is irrelevant when it comes to space travel. Unless an object is within the vicinity of the Oort cloud, we stand very little chance of actually leaving this solar system in a controlled fashion.
- madaxe_again 10y agoWell, the key is to not take thousands of years about it. Honestly, I doubt we will ever have thousand year missions, unless our lifespans commensurately grow, as humans don't have a great track record when it comes to long term projects. There are ways, but they are expensive and not without risk. Nuclear pulse propulsion (orion) can yield vast acceleration, and fusion rockets, while unproven, are feasible. You then have less exotic options such as laser driven light-sails and nuclear powered ion drives. If we were prepared to throw half a trillion bucks at the problem we could see a flyby in our lifetimes - but without a damn good reason, it won't happen.
- npace12 10y agoIt's probably Trisolaris
- theodorejb 10y agoIt took 9.5 years for New Horizons to reach Pluto (just 32 astronomical units distant). At that rate, it would take a probe more than 80,000 years to cross the 271,000 AUs separating Earth from this exoplanet.
- mabbo 10y agoThat presumes a constant velocity. Any extra-solar ship would certainly need a different acceleration profile. Ion engines come to mind: low acceleration, but constant for a very long time. If you're going a far distance, they're ideal.
- spuz 10y agoUnfortunately, not ideal enough. But there are other options: https://www.youtube.com/watch?v=EzZGPCyrpSU https://www.youtube.com/watch?v=EzZGPCyrpSU
- dalke 10y agoWhile you have a valid point, here's what it works out for ion engines. Assume you want 1,000 years to Alpha Centauri and your ship boosts the entire way. (It'll take a few pictures as it flies through the system.) s = 1/2 a t^2 a = 4.22 light years * 2 / ((1000 years)*(1000 years)) = 8 E-5 m/s/s Sounds great, right? But the final speed is: v = a * t = 4.22 light years * 2 / (1000 years) = 2.5E6 m/s = 0.8 c (!) Let's say your engine has a ISP of 8000 s, which is about 10x better than anything we have. Then from the rocket equation you'll need a dry weight (payload, engines, etc.) to propellant ratio of e^(2500000 / (9.8 * 8000) = 70,579,094,313,732 = 71 quadrillion eg, 1 gram of spacecraft requires 70 kilotons of propellant But wait, there's more! It takes power to push 70 kilotons of propellant backwards at 80,000 m/s. E = 1/2 * m * (v^2) = 2E20 Joule Since E = m c^2 => total annihilation of over a ton of antimatter Almost certainly more as that assumes 100% efficiency. And of course that extra ton isn't propellant, so it hits you in the rocket equation. Note: I am not a rocket scientist and likely made mistakes. Even if I'm off by a few zeros, it's enough to show that an ion engine isn't going to get something to Alpha Centari within a few centuries.
- sevenless 10y agoMoving matter around takes far too long for star travel. We need to figure out how to assemble machines from long distances using light. (Something like https://en.wikipedia.org/wiki/Optical_tweezers https://en.wikipedia.org/wiki/Optical_tweezers)
- Teever 10y agoWhy not just launch a seed factory and send the instructions to build via light? That seems a hell of a lot more practical and cost effective
- kyzyl 10y agoAlso more possible haha. It's all fun and games until you predicate the success of your project on trying to collimate a laser beam from here to alpha centauri, so that it can manually assemble a (dielectric!) robot one piconewton at a time.
- deleted 10y ago[deleted]
- GeneralMayhem 10y agoThat sounds pretty impossible assuming that we're aiming for a planet with an atmosphere. Maybe if the planet has a moon, and then all we have to do is remote-construct a machine that can both do our research and make the small hop down to the surface?
- rcarmo 10y agoCan't wait for the "small furry creatures from Alpha Centauri" memes.
- grondilu 10y agoI vaguely recall a quote saying that if an Earth-like planet was ever found around Proxima Centaury, an international project to build an interstellar probe would begin immediately. Well, we'll see.