It seems to me that the accuracy required to aim an unguided projectile anywhere near the target stars will be impossible. They'll fly by pretty far. At what distance to Alpha Centauri does an iPhone quality camera outmatch the Hubble's photos?
A Visionary Project Aims for Alpha Centauri, a Star 4.37 Light-Years Away
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Re: A Visionary Project Aims for Alpha Centauri, a Star 4.37 Light-Years Away
#32Sending a swarm of unguided relativistic projectiles across the universe seems profoundly rude.
Ten thousand years from then, some alien on some planet somewhere might have a very bad day.
"That is why, Serviceman Chung, we do not eyeball it!"
Re: A Visionary Project Aims for Alpha Centauri, a Star 4.37 Light-Years Away
#33So the whole thing should weigh in the order of several grams, yet it should be able to deflect 100GW of incoming radiation near perfectly (otherwise it will instantly vaporize) while maintaining structural integrity under the acceleration of 60,000g for two minutes? And whatever laser sources we're using must track this smartphone-sized object during these two minutes across several million kilometers. Perfectly. (I…
One thing to note is the reported mindset of the program. It doesn't really talk about their expectations around plausability of this, but rather that they seem to be targeting success through large numbers even at low probabilities. They might not care to anticipate/correct anomalous "course deviations" but rather write those off as a loss completely, hoping that just a few of many initially accelerated succeed.
Re: A Visionary Project Aims for Alpha Centauri, a Star 4.37 Light-Years Away
#34Zuck to fund interstellar travel w/in decades? 2040 Breaking News: Alpha Centauri Rejects Facebook's 'Free' Internet
Re: A Visionary Project Aims for Alpha Centauri, a Star 4.37 Light-Years Away
#35I thought very strange things start to happen at even 10% the speed of light (mass increase, etc.) so 20% sounds impossibly ambitious? Also the fastest physical object we've ever observed is only 1000 miles per second. A far cry from even 10% of c Then there is that pesky problem of deceleration.
At 20% the speed of light, time would dilate by around 2%, but that's about the extent of the effects, afaik. Also: why bother decelerating at all? Take a picture as you fly by.
Have you ever tried to take a picture from a moving car? They never turn out.
Re: A Visionary Project Aims for Alpha Centauri, a Star 4.37 Light-Years Away
#36Sending a swarm of unguided relativistic projectiles across the universe seems profoundly rude.
Their speed isn't particularly relevant, what matters more is their energy. As big as that number is to us, it's still pretty insignificant; there's a lot of objects already traveling around with us in our own solar system with 70kT (per PaulHoule in other comments) of energy. A looooooot of objects. In the grand scheme of things, this is a rounding error on a rounding error. We are small.
Re: A Visionary Project Aims for Alpha Centauri, a Star 4.37 Light-Years Away
#37So the whole thing should weigh in the order of several grams, yet it should be able to deflect 100GW of incoming radiation near perfectly (otherwise it will instantly vaporize) while maintaining structural integrity under the acceleration of 60,000g for two minutes? And whatever laser sources we're using must track this smartphone-sized object during these two minutes across several million kilometers. Perfectly. (I…
Solar sails seems more feasible to me.
Re: A Visionary Project Aims for Alpha Centauri, a Star 4.37 Light-Years Away
#38So, how is a tiny smartphone-sized probe supposed to transmit data back to Earth from 4.37ly away?
That is a good question. The Voyager spacecraft send out detectable signals with a ~20 Watt signal. This is larger than the ~3 W signal that a smartphone sends, but by less than an order of magnitude.
Voyager is at ~130 AU. Alpha Centauri is at ~275,000 AU. With the 1/r^2 decrease in signal, that means the signal from earth will be smaller by a factor of ~3 x 10^6. Now, supposing we have ~1000 of these smartphone probes, this means that their combined signal will be weaker than the Voyager signal by a factor of ~3000. We might imagine that they are somewhat more optimized to send a stronger signal than an ordinary smartphone. Let's say they have a 30 W radio instead of 3 W. This means that they will have a weaker signal by a factor of ~300. This is a lot, but if they manage to build a detector that has a larger effective diameter than the Deep Space Network by a factor of ~15. Given the budget of the project, and the fact that they have 20 years of time to prepare after the launch, this could be feasible.
Looking at the project's website, though, it looks like they are taking the approach of using a laser onboard the probe instead of using a traditional radio transmitter [1]. This would increase the efficiency of the transmission by several orders of magnitude. It might even be possible to detect the signal from a single probe with this approach.
[1]: http://breakthroughinitiatives.org/index.php?controller=Foru...
Re: A Visionary Project Aims for Alpha Centauri, a Star 4.37 Light-Years Away
#39So the whole thing should weigh in the order of several grams, yet it should be able to deflect 100GW of incoming radiation near perfectly (otherwise it will instantly vaporize) while maintaining structural integrity under the acceleration of 60,000g for two minutes? And whatever laser sources we're using must track this smartphone-sized object during these two minutes across several million kilometers. Perfectly. (I…
A laser capable of propelling an interstellar probe is also a mighty space weapon. Some people proposed constructing that on the far side of the Moon so that it hass less of a chance of being used as against Earth targets (intentionally or by accident).
Re: A Visionary Project Aims for Alpha Centauri, a Star 4.37 Light-Years Away
#40Sending a swarm of unguided relativistic projectiles across the universe seems profoundly rude.
> a swarm of unguided relativistic projectiles In a sense, this is essentially what the universe is .
True, the universe is generally a pretty unfriendly place that tries to kill you in any possible way.