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[GreatWyrmGold]

until we can rework physics it seems to me a multi-generational approach is the only reasonable approach to making it to our neighboring stars' planets.

Hypothetically, if we could create a well- or self-maintained* starship and had a way to put humans into indefinite hibernation, using that could work. Less chance of a degradation of technical skills/loyalty to Earth/etc.

[Il Palazzo]

[1] Let's see, ignoring the relativistic effects that we seek, with 9.8m/s per second increase over two years that would take us to 61,852,896m/s, wouldn't it?  c= 3x10⁸, so a tad over 0.2c, so we'd reach only 96-ish percent of the time passing (at the top end) of what 'actually' passed for the non-travelling observer...  So doesn't sound like we need to bother too much with integrals to work out how that all works when you add in the changing T/T₀ factor, it'd still take almost four years (apparent) to get there, such a short distance away.  Now, sustaining 3g (possible in the long term? ...probably would need a lot of risky training/acclimatising) would give a "raw max" time dilation that would make 4y seem like 2.5-ish...  still not good enough, especially as most of the time you woukdn't be going that fast in the first place...  but such a book-ended journey to somewhere more than 10ly distant could give us some calculations to do that give far more worthy "trip-shortening" tricks... albeit for a longer trip both in objective and subjective POVs...))

Here's a nice calculator for this kind of problems:
http://www.convertalot.com/relativistic_star_ship_calculator.html
(your back-of-an-envelope math is close enough)

[Aseaheru]

well, unless there is a form of instantaneous communication then loyalty to earth is not that much of an issue, as by the time anything happens it will already be to degraded to matter.

[Starver]

(and happier with a practical Venusian surface base than a "cloud city" one),

Unless we find a way to obliterate 99% of a planets athmosphere, we ain't having no Surface bases on Venus. Why does nobody like the floating base thingies.

I don't actually dislike them, and I acknowledge that there'd be problems behind a surface base (thus qualifying the base as needing to be "practical").  I was just stratifying my imagined preferences.  Ground best, orbital worst.  A semi-stable cloud-city might sit between the two.

OTOH, if I think about it more, I could actually be saying "Ground best, orbital next-best, cloud-city worst".  A problem in orbit tends to mean at least some time 'just' in a different orbit (which could be corrected for, or rescued from, as required).  A whole cloud city (or a person working on the outside of it) that somehow ends up falling is just going to quickly find it/themselves heading downwards.  Potentially at great speed.  You have the generally Earthly problem of how to survive the fall mitigated a bit by the thick atmosphere.  But, in turn, you are now faced with the almost-uniquely Venusian issue of how to survive the ground-level pressure and heat and acidity that so discouraged the guys in R&D from constructing any ground-base... And, should you survive, how soon might any practical rescue arrive?

Get me an active Venus Ground Base below me, and I might be happier (with precautions) working on a Venus Cloud Base.  Something tells me I really wouldn't enjoy a tour of duty on a Jovian Cloud Base, even if they can make it a nominally Earth-normal environment by one means or another, and I've a feeling that that's impossible gravity-wise but don't even fancy it enough to speculatively check that out...

[10ebbor10]

About Orbital power plants. Once we get a spaceelevator, or any sort of renewable rocket, they're more viable. Still need increased efficiency (though up to 40% is possible in the lab), and transmission remains a problem; but it could work. (Note, the Falcon Heavy could in fact lay the foundation of such an installation, once the Grasshoper technology(which makes the rocket reuseable) is completely functionall ). Just for comparison. Currently, the cheapest launch cost in reach is 1000 dollar/kg, with a reusable rocket that can halve, with a space elevator it could drop below 50 dollar, at which point only the energy prices matter.

About relativistic speeds. I think if we take 0.7 c as top speed, we can get to alpha in 6 years, and it'll seem like less than 4. Completely surviveable, but also completely bonkers from an economical/energy viewpoint.

About magnetic shielding. Fairly bad at the moment. They use a lot of power, and tend to overheat/shortcircuit. And we, AFAIK, never tested one in space. Positive side is that we can use the magnetic shield as propulsion, either for fusion drive containment, or as a gigantic solar sail. Gamma and X rays are easier to shield from, and appear less frequently than charged particles.

Another note about computers, I expect the ones on a spaceship to be really outdated. Like vacuumtubes and such. Mostly because those are much better at resisting radiation and interference.

[Starver]

I've yet to see a 200 years old skyscraper

...give it time...

(or would we send pyramids in space ?)

Oh yes!  Just 'Yes'!  If the aliens aren't doing it, already, we should.  In fact, at the first opportunity I'm gonna carve me a solid pyramid out of some unwanted asteroid and slingshot it out to some distant star, just to mess with the aliens' heads/head-equivalents.

[Starver]

Of course, most computers haven't been around since before 1993.
...Not that there's a lot of computers from pre-1993 that still function, but that might be as much from changing technology as anything. On that note, the toughest computers probably include some of the newest.
I'm going to stop and leave this to someone who knows what they're talking about before I embarrass myself more.

My own personal knowledge (which may not be complete and up-to-date) is that space missions do not use the latest technology, as they're too sensitive to cosmic rays.  (Or, possibly, too untested against them, but I've a feeling that 486s/early Pentiums with their less microscopic circuitry are used because they're more resilient, just like vacuum tubes were deemed to be more proof against nuclear EMPs than the component transistors and ICs that came after them.)

[Aseaheru]

i believe that the shuttles use 70s tech, which is non-vacuum tube.

[GreatWyrmGold]

well, unless there is a form of instantaneous communication then loyalty to earth is not that much of an issue, as by the time anything happens it will already be to degraded to matter.

Four words: Violent counter-colonization fleet.
It's something to worry about a little.

(and happier with a practical Venusian surface base than a "cloud city" one),

Unless we find a way to obliterate 99% of a planets athmosphere, we ain't having no Surface bases on Venus. Why does nobody like the floating base thingies.

I don't actually dislike them, and I acknowledge that there'd be problems behind a surface base (thus qualifying the base as needing to be "practical").  I was just stratifying my imagined preferences.  Ground best, orbital worst.  A semi-stable cloud-city might sit between the two.
OTOH, if I think about it more, I could actually be saying "Ground best, orbital next-best, cloud-city worst".  A problem in orbit tends to mean at least some time 'just' in a different orbit (which could be corrected for, or rescued from, as required).  A whole cloud city (or a person working on the outside of it) that somehow ends up falling is just going to quickly find it/themselves heading downwards.  Potentially at great speed.  You have the generally Earthly problem of how to survive the fall mitigated a bit by the thick atmosphere.  But, in turn, you are now faced with the almost-uniquely Venusian issue of how to survive the ground-level pressure and heat and acidity that so discouraged the guys in R&D from constructing any ground-base... And, should you survive, how soon might any practical rescue arrive?
Get me an active Venus Ground Base below me, and I might be happier (with precautions) working on a Venus Cloud Base.  Something tells me I really wouldn't enjoy a tour of duty on a Jovian Cloud Base, even if they can make it a nominally Earth-normal environment by one means or another, and I've a feeling that that's impossible gravity-wise but don't even fancy it enough to speculatively check that out...

I wouldn't mind a cloud base designed by halfway competent engineers. It would probably work by the same principles a balloon or (sea)ship works, and be sealed off similar to a spaceship. I'd rather live in such a base than a spaceship--it's easier to make bigger and has gravity. The biggest problem is power, actually...

[Aseaheru]

well, would geothermal work?

i mean, VENUS. HOT.

[Sheb]

Re: Magnetic fields and stuff.

I remember reading in some magazine that an effective field would have to be several Tesla. We don't know the effect on health of such intense fields, but they had an interview from some physicist that once put his head in between a cyclotron's magnets and reported intense headeache and temporary loss of vision.

[Dutchling]

I want to know more about that scientist. He seems like a rather awesome fellow.

[Aseaheru]

he sounds like a dwarf.

[PanH]

I've yet to see a 200 years old skyscraper

...give it time...

(or would we send pyramids in space ?)

Oh yes!  Just 'Yes'!  If the aliens aren't doing it, already, we should.  In fact, at the first opportunity I'm gonna carve me a solid pyramid out of some unwanted asteroid and slingshot it out to some distant star, just to mess with the aliens' heads/head-equivalents.

I was pointing out that few building actually make to 200 years. The pyramids being one of the few exceptions

some physicist that once put his head in between a cyclotron's magnets and reported intense headeache and temporary loss of vision.

This man. Is AWESOME. Real !!SCIENCE!!

[vadia]

well, would geothermal work?

i mean, VENUS. HOT.

You're joking right?

Just in case you aren't.  We don't currently have tech that would last much more than an hour on the surface of Venus in that the pressure is like being under 1km of water. 

It is MUCH easier to throw mercury into Venus and mine the heck out of what is left than to do any colonization of those two, (but I think Venus is much harder than Mercury)