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October 16, 2012

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i don't want to go anywhere else. i like it here.

that is all.

Closer to the planet because they're easier to detect closer in. Good new is, planets seem to come in flocks, so it might have brothers that *don't* have molten surfaces.

what's the top marginal tax rate on Alpha Centauri Bb ?

and, can it be spelled Alpha Centauri A# ?

Damn, send a flyby probe. Small and fast.

Terrans have no right to be so lucky, to have extrasolar planets so nearby.

Mitt and Dagny visit their money on the planet with the molten surface, where marginal rates were dropped to 0% to attract capital.

They have a beach house on the Sea of Fire. Dagny wears stiletto heels and shades on the hot sand and drinks fire retardant cocktails.

Grover, the neighbor, has a place down the shore a ways. He drowned his baby in the molten lava during the awful eons when the 1% planetary excise tax regime reigned, but folks thought nothing of it amidst the general conflagration.

There are cranks dwelling on the other side of the planet who warn of planetary cooling and the arrival of more hospitable flora and fauna but the forces of the molten status quo keep them at bay with unlimited funding from the Intergalactic Federation of PACs.

The lone gift shop on the planet went up in flames last eon.

Erick Erickson and Hinderacker yelled "Arson!"

I wonder if NASA has plans on sending a probe towards Alpha C. (Or even just conceptual studies.) Considering that the Voyagers, with 40 year old technology, are still going, we ought to have a shot at building something that could make it.

It would take a very long time, but so what? We could learn something along the way. And if faster-than-light drives don't come along, we would actually get there eventually, and learn a lot about how another solar system looks.

It would take a very long time, but so what?

At Voyager speeds, "a very long time" is 83,729 years.

A very long time, in the sense that probes sent with later technology would overtake any sent with today's technology, rendering them pointless. Really, there's no point in launching interstellar probes until you're getting them up to at least a couple percent of light speed.

Turb, if we can't get there any other way, what's the difference? Think of it as an act of faith -- a demonstration of belief that we will be around and interested that long.

Brett, I'm trying to figure out what technology (absent FTL, of course) would produce higher speeds. The gravity slingshot isn't going to get much faster.

I don't know if a solar sail has much potential. But again, I don't see a lot of prospect for massive improvements. Further miniturization will allow weight reductions, of course. But how big a velocity increase will that lead to? (I figure we already know pretty well how to make a carbon-fiber, couple of atoms thick, sail. So not a lot of room to get lighter there.)

Turb, if we can't get there any other way, what's the difference?

I don't think we know how to make devices that will function in 80K years. I mean, electron migration in semiconductors would be a huge problem to start with. Power would be an enormous problem. Materials to resist 80K years of dust bombardment are another nightmare.

But if you arrange to have V(oya)ger get nabbed by an alien civilization and upgraded, it could likely get there much more quickly.

Seriously, Voyager only has power for another couple of decades, so any "very long time" that exceeds that span is moot.

Any kind of probe that we might send would have to have some kind of very high specific impulse propulsion system, enough reaction mass to arrive and achieve reasonable flyby speeds or even orbit around Alpha Centauri B, and a sufficiently robust power-generation system to last for, say, centuries. Or perhaps decades, if you account for the ability to shut down and restart after some very long coast phase.

Getting any information back here would also be a task. And of course the vehicle would have to be autonomous for obvious reasons; two-way lightspeed delay of nine-ish years does not make for stable closed-loop control.

Slarti and Turb, longevity is clearly a problem. But I keep thinking about what the design lifetime for the Voyagers was. And how far they have exceeded that. No doubt it gives me an excessively optimistic view.

The problem with faster is shielding. Even at the leisurely slow cruising speed of 5% lightspeed (which, tossing away accelerate/decelerate time as if they were impulsive, I call average), a 1 milligram speck of interstellar debris packs a disconcertingly large amount of explosive potential.

Goodbye, probe.

I say "leisurely" because at that rate it'd take a century to get there. Cut that speed in half, and reduce our particle of debris to a microgram and you've still got an impact that can wreck any sticking-out bits of equipment. Or, the way Voyager 2 is shielded: the whole thing.

have we ever sent a probe... up? that is, perpendicular to the planetary plane?

Some messages from about 40K years ago.

The medium is charcoal and clay paints. The authors may have been h.sapiens or h.neanderthalensis, it's unclear.

What do they mean?

80K years ago, humans (apparently of various species) were (depending on location) somewhere toward the end of the middle paleolithic.

So, hunter gatherer bands numbering in dozens to hundreds, stone and bone tools, fire and cooked food. Probably music, maybe something we might recognize as religious or spiritual belief and practice. No writing. No farming or livestock. Maybe dogs were "domesticated", where "domesticated" means "lived among humans".

I can't imagine what "being human" will look like 80K years from now, let alone what sense folks then will make of messages beamed back here from an 80K year old device floating around Alpha Centauri.

Not trying to rain on anybody's parade, just trying to understand what "80K years later" looks like IRL.

would have to have some kind of very high specific impulse propulsion system

Yes.

The continual-low-thrust ion engine used on the Dawn probe that visited Vesta and is now on its way to Ceres is one such, and has the potential to achieve really high velocities with a realistic fuel mass and a very small payload. (On the other hand, IMHO, deceleration at the other end is impracticable; the required fuel mass pyramids, and the math no longer works out)

But I still think we're talking a thousand years -- more time than separates us from William the Conqueror. Who will be listening for data in a thousand years when the probe finally flashes through Centauri system?

This whole discussion has occurred a while back, not surprisingly. Computers are probably a whole lot better since then, but I am not sure that propulsion has. At least, it definitely has not improved commensurately.

At least one probe (Ulysses?) got sent over the Sun's poles. And as I recall its path to get there involved going around Jupiter. So it got out of the ecliptic at least a little bit. Whether it included instruments to take any measurements of things other than the sun, I don't know.

Looking at this in terms of delta vee, the plane change aspect of this pales in comparison with everything else. If you can achieve 1% lightspeed in a year, then you can achieve the required plane change maneuver in about a week, which I think simplifies the problem. If it's going to take longer, or you're not going to be able to achieve the kind of velocity you want, it might be better to slingshot out further to, say, Uranus' orbit, where the solar escape velocity is reduced by ~20 km/s.

I've not really done much with transfer orbits other than Earth/Moon, so I could be way off.

If I'm reading this correctly:

http://en.wikipedia.org/wiki/Project_Orion_%28nuclear_propulsion%29

You could get there in 44 years, at the expense of a bunch of hydrogen bombs. Twice that time if you actually want to slow down and visit.

I think one of the long distance probes (one of the Pioneers?) got shot out of the plane by swingby at Jupiter but I'd have to check it.

One project I have heard of as being seriously considered is a very light net (just a few grams) studded with reflector chips that would get accelerated by ground based lasers. That way it would not need to carry fuel by itself because all the energy would be provided externally. The net structure would also make it far less vulnerable to damage on the way. It would reach the next star in a few decades, i.e. managable time. Not much of data collection potential there though since it would pass through the target system at full speed and given how light the whole probe is not that much could be put into the chips. It would just be a feasibility test that we can do interstellar probing in a reasonable timeframe and at managable costs.

I think the future lies in large interferometric satellite telescope networks stationed in stable orbits (e.g. around the Jupiter or Saturn Lagrange points). Current projects for interferometrically linked satellites* already work with baselines of many thousand miles. The step to baselines in the million miles range should be possible quite easily. Given what effects we can achieve already on the ground level, this will make it possible to read newspapers on planets circling neighbouring stars. It would essentially remove the need to send camera probes there or it would give us solid information where it would be useful to send anything material to.

*space based gravitational wave detectors

It was Ulysses, as wj mentioned above, that went "up" with the help of Jupiter's gravitation to orbit the Sun in its polar plane. Not that I knew that before googling it after reading wj's comment earlier today.

I should say "one of its polar planes."

Camera obscuras in space might be a useful approach to viewing light from planets while masking out the interfering light from their stars.

Perhaps the Moties will get out of town on that light sail after all.

"Brett, I'm trying to figure out what technology (absent FTL, of course) would produce higher speeds. The gravity slingshot isn't going to get much faster."

Project Orion, as mentioned above. Generally the direct use of nuclear energy for propulsion, which comes in a lot of flavors. The multiple variety of sails, with or without added artificial "wind" to help them.

There are a lot of proposed propulsion technologies, ranging from 1960's tech, (Orion) to the near future, (Fission fragment propulsion.) to the slightly more distant future, which will get you into the 1-10% light speed range.

1mg specks are, fortunately, rather uncommon in interstellar space, which is why we can see the most distant stars. But shielding IS an issue which would need to be solved. I believe it's entirely solvable, there are a number of approaches. My favorite is pushing a lightweight sail ahead of the probe, which will transform all incoming gas and specks into plasma, and then surrounding the probe with a strong magnetic field to deflect the plasma.

This just proves that there's ALWAYS a use for a big-ass rail gun.

cleek:

can it be spelled Alpha Centauri A# ?

Depends on the temperament of the planet I suppose.

Can we assume a well-tempered exoplanet? or is that merely projection? How does the Pythagorean comma hold up under other gravity/temperature combinations? Do just temperaments lead to just societies?

(Eh, sorry I'm late. Business trip. Taxonomists are a funny bunch.)

The 1st pic is really beautiful, the 2nd pic is quiet scary 4 me. The world is ending in 2012........

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