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Interstellar Flight: Perspectives and Patience

centauri-dreams.org

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Re: Interstellar Flight: Perspectives and Patience

#11

Post by mr_toad »

os2warpman wrote: post #6

>To get around thousand-year generation ships, we are examining some beamed energy solutions that could drive a small sail to Proxima in 20 years. The odds of a spacecraft hitting a single particle of dust while in space are 100%. A spacecraft hitting a single particle of dust at 0.2c will impart tens of millions of joules into the body of the spacecraft, the equivalent of getting hit with hundreds of pulses from the…

Ten megajoules sounds like a lot, but a single kilo of TNT produces about 4 megajoules of energy. And the size of particles of dust and how often you’re likely to hit one in the interstellar medium is quite speculative.

Re: Interstellar Flight: Perspectives and Patience

#12

Post by agentultra »

cryptoz wrote: post #4
agentultra wrote: post #3

Won't dreams stay dreams? There's literally nothing there, why go all that way? The distances are so incredibly vast. It seems like we ought to be content with staying put.

All life on Earth is going die. Humanity has never been content with staying put, why would we start now? And what do you mean "literally nothing there"? The universe has a loooooot of stuff in it.

It's mostly empty, isn't it?

By "literally nothing there," I mean there's literally nothing for us. Three stars and a few Earth-sized planets in the habitable zone that are, more than likely, uninhabitable by humans. There's nothing there worth going all that way for.

I like sci-fi as much as the next person but the reality of the situation, it seems to me, is that the universe is mostly empty, vast, and inhospitable to human life.

Re: Interstellar Flight: Perspectives and Patience

#13

Post by WalterBright »

The only way I can see hope for spreading terrestrial life through the galaxy is to send tiny spacecraft. The spacecraft can survey what it finds and send the information back to earth. Earth can send back instructions to the nanobots on the spacecraft to build what is necessary from local materials, and then build life to inhabit it.

Re: Interstellar Flight: Perspectives and Patience

#14

Post by mr_toad »

agentultra wrote: post #3

Won't dreams stay dreams? There's literally nothing there, why go all that way? The distances are so incredibly vast. It seems like we ought to be content with staying put.

> There's literally nothing there

“Literally everything is in space.”

Re: Interstellar Flight: Perspectives and Patience

#15

Post by trhway »

os2warpman wrote: post #6

>To get around thousand-year generation ships, we are examining some beamed energy solutions that could drive a small sail to Proxima in 20 years. The odds of a spacecraft hitting a single particle of dust while in space are 100%. A spacecraft hitting a single particle of dust at 0.2c will impart tens of millions of joules into the body of the spacecraft, the equivalent of getting hit with hundreds of pulses from the…

alternatively you ionize that particle, may be make in into plasma by laser for ease of "digestion" down in the engine, direct in into the engine where it is used as working mass for your ion thruster, kind of similar to scramjet.

As far as i see with today's tech - like Starlink's ion thruster + classic nuclear reactor - we can get to 300km/s in about 4 stages. Straightforward improvement of ion thrusters - mainly voltage increase and associated engineering (which will immediately happen once we start flying to Mars and beyond as ion thruster currently our best/fastest option inside the Solar system) - can get us to 1000-2000km/s, i.e. under 1000 years to Alpha Centauri (that for a large populated spacecraft, and for just tiny probe to announce our existence (and to send back photos which we'd receive using Sun's gravitational lensing) we can do even better). And using interstellar gas and dust scramjet-style will improve on those numbers (as such ship is mostly limited by the working mass it starts with while the reactors would be able to continue produce the energy much longer).

Re: Interstellar Flight: Perspectives and Patience

#16

Post by krunck »

The comment by Benjamin Stockton on the article page is spot-on:

>I just wonder if humanity’s adventurous nature is leading us away from a proper focus on the sustainability of our civilization, our specie, and our fragile planetary environment?

But we still need spaceflight at least for planetary defense against asteroids, mining asteroids(so we don't have to mine Earth), etc.

Re: Interstellar Flight: Perspectives and Patience

#17

Post by AnimalMuppet »

agentultra wrote: post #3

Won't dreams stay dreams? There's literally nothing there, why go all that way? The distances are so incredibly vast. It seems like we ought to be content with staying put.

There was a time when there was nothing (European) in the entire New World. There was a time when there was nothing known (to the US) about what was in most of the Louisiana Purchase. There was a time when there was nothing (European) in, say, Ohio. And then Nebraska. And so on.

There was literally nothing there? Why go all that way? To see what was there. And then to make something there.

[Edit, because I'm rate limited: No, interstellar space is something to cross, to get to stellar space. You think the New World was rich? How about a whole solar system of untapped resources?

That's why people will try to go.]

Re: Interstellar Flight: Perspectives and Patience

#18

Post by os2warpman »

archermarks wrote: post #9
os2warpman wrote: post #6

>To get around thousand-year generation ships, we are examining some beamed energy solutions that could drive a small sail to Proxima in 20 years. The odds of a spacecraft hitting a single particle of dust while in space are 100%. A spacecraft hitting a single particle of dust at 0.2c will impart tens of millions of joules into the body of the spacecraft, the equivalent of getting hit with hundreds of pulses from the…

Only true if the dust grain is stopped by the craft. For a thin lightsail the grain will probably pass right through without depositing much energy

I wasn't even considering the sail.

Most of the designs for a system like this are "chip" designs where a single 1cm x 1cm silicon wafer is towed by the sail.

This design prevents the need for lasers so large that they create enough ozone to kill the entire human race.

The contents of the chip vary, based on who is speculating, but tend to contain exotic, uninvented, circuitry capable of both harvesting energy from the laser and doing "something" of use besides zipping by the target at 0.2c deaf, dumb, and blind. Sometimes it's even an AI-enhanced swarm! (Shoulda figured out how to work blockchain in there, post-doc guy)

Regardless, during the 40 trillion kilometer voyage to Proxima Centauri, that 1x1cm silicon wafer (and the sail) will hit space dust, and numerous other atoms and molecules (including carbon rings) because empty space... isn't.

Re: Interstellar Flight: Perspectives and Patience

#19

Post by ta1243 »

KineticLensman wrote: post #2

> those of us with an interstellar bent naturally start musing about ‘sundiver’ trajectories, using a solar slingshot to accelerate an outbound spacecraft, perhaps with a propulsive burn at perihelion. . The latter option makes this an ‘Oberth maneuver’ and gives you a maximum outbound kick. You can't do a solar slingshot like you can with (say) Jupiter because the sun is essentially at rest with respect to the rest…

If you unfurl a solar sail after perihelion, presumably you get more energy while nearer the sun, giving more of a "kick", and lower in the gravity well (would oberth still apply for solar sail)

Your speed once you get to 1AU would I assume be far higher than if you had simply started at Earth

Re: Interstellar Flight: Perspectives and Patience

#20

Post by sorcerer-mar »

krunck wrote: post #16

The comment by Benjamin Stockton on the article page is spot-on: >I just wonder if humanity’s adventurous nature is leading us away from a proper focus on the sustainability of our civilization, our specie, and our fragile planetary environment? But we still need spaceflight at least for planetary defense against asteroids, mining asteroids(so we don't have to mine Earth), etc.

What resources are on asteroids that justify the energy expenditure to get from space and back? Can't be many of them...
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