Space 18: A Holiday Card for the Kelvans

[wrog]

(continued from here)

So, now what?

Intergalactic Travel

This is where we get full-on, batshit crazy. (You knew this was coming, right?)

Quick reminder in case you forgot or didn't know: M31, i.e., item #31 on comet enthusiast Charles Messier's list of things that annoyed the shit out of him because they weren't actual comets, otherwise known as the Andromeda galaxy, is one of our nearer galactic neighbors, perhaps not the nearest, but it's the one everyone thinks of, so let's just go there.

It is 2.54 million light-years (2.62 million aLY) away. No problem, right? Let's have a look at the numbers:

accel / decel		total shiptime (aY)	mass Cost
shiptime (aY)	distance (aLY)
14.78	1,310,986.97	29.56	2,621,975.93
14.52	1,015,049.37	29.63	2,030,100.74
14.27	785,915.64	29.87	1,571,833.28
14.01	608,505.71	30.33	1,217,013.42
13.76	471,143.65	31.08	942,289.29
13.50	364,789.19	32.19	729,580.38
13.24	282,442.80	33.77	564,887.59
12.99	218,684.97	35.97	437,371.95
12.73	169,319.61	38.95	338,641.21
12.48	131,097.80	42.95	262,197.59

Yes, these mass costs do look a teentsy bit prohibitive.

And yes, you're reading that right:  Even in the cheap case where we're opting to have the journey take 43 years — presumably, by the time we're contemplating this, we'll have figured out how to make an interstellar cruise ship tolerable for a few decades of travel rather than merely a few years (unless we're doing the Australia Thing, it's all prisoners, and we don't care) — we're still burning an entire Enterprise-class aircraft carrier (100,000 metric tons) for every five people we send.

On the other hand, it's a fair bet we won't even be considering this until we've developed, say, a substantial fraction of the Milky Way, say, 100 billion systems. Note that for this particular purpose "developed" means having gotten as far as building energy collection infrastructure and transit tubes; we don't need for them all to be inhabited. If they've all got the same 43,200 kg/day transit budget and we just declare a one day Transit Holiday for everybody, that's … rather a lot of aircraft carriers filled with antimatter, enough to send 200,000 people.

Do that a few days a year for a century and we're basically sending a Europe or 1/3 of an India. Which is not entirely bad for starting off a new galaxy.

But it's possible I'm being too conservative here. Because of something I haven't mentioned yet (it really only occurred to me today).

The Absolute Best Power Plant Ever

By the time our exploration sphere has expanded 25,000 light-years to include the center of our galaxy, we will then be encountering the Sagittarius black hole…

… which I originally thought we'd be wanting to stay the hell away from, but…

It spins, see, which means if you throw shit into it at just the right angle and arrange for it to break apart inside the ergosphere (weird-ass 2nd-event-horizon thing that spinning black holes have that you can actually get out of) at just the right time, then half of it will be spit out way, way, way, faster than anyone should reasonably expect, and then you collect all of that extra energy at some safe distance (hahahaha) and use it to charge up antimatter cells.

And then we're building the Really Big version of the solar energy conveyor thing to get all of that antimatter shipped out of there.

These guys say the rotational parameter for the SBH is around 0.44, which means that about 2.6% of its million-some-odd solar masses is rotational energy that can be completely extracted in this way, meaning there's about 5×10³⁴ kg theoretically available to be harvested.

That's half a billion billion billion aircraft carriers. Possibly more as long as there's crap continuing to fall in to speed up the hole. If we don't get greedy and, say, only take a trillion aircraft carriers per year, that's 3 trillion star systems worth of power generation right there.

Without having to explore and settle 3 trillion star systems.

… modulo certain engineering issues that I will not be attempting to address at this time. I suspect we will need to be using both sides of the paper for this one.

I'll grant that my original timeline has the explorers taking a few million years to reach the center of the galaxy and the SBH. It may be that once we have sufficient infrastructure in our immediate neighborhood, we may want to splurge and launch a few Really Fast explorers in the general direction of Sagittarius so that they're getting there a lot sooner, say 30,000 years.

This will be expensive: We're talking 5/6 lightspeed, which means mass cost ratio of around 11 and recall the explorer ships are big, ten aircraft carriers each, so that's 110 aircraft carriers to launch each one or 7000 times our annual single-system transit budget. Then again, recall that Earth is going to have thousands of years of downtime waiting for those first terraformed exoplanets to come on line. Or we could wait the 2500 years to have energy infrastructure set up in 100 systems so that launching the SBH-explorers won't be as big of a bite.

There's also be risk in launching explorers that far that fast in that we currently have no idea what the solar systems are like in closer to the center of the galaxy, whether the mining/reproduction stuff is even going to work out there; the advantage of the slower plan would be in knowing what's there long before we arrive.

But it may well be worth it if we can have this fucking huge energy pipeline up and running in a mere 60,000 years.

If we have the FHEP, we're definitely getting to Andromeda.

Or, if we want to be more ambitious some year and can extract just 0.00000000000002% of the SBH energy available, that's enough to send a billion people each to every single galaxy in the Local Group using the completely wasteful Andromeda-in-29.56-years schedule (first line of the chart above).

Doing the Long Range Exploring

The economics get a little weird, because there's no getting around spending a few million years on exploration and tube construction, and if we're willing to wait another million years, then the entire galaxy will be already terraformed and harvesting energy by the time we get there.

Also, Andromeda almost certainly has it's own big-ass black hole, and unlike with the Milky Way, our explorers can be heading straight there first thing to get that pipeline started. Which then gets us started on the next galaxy quite a bit sooner than you might think.

Never mind that we're now operating on a timescale where there'll be time to build some real Earths, not just the fake ones you can throw together in a few thousand years. Assuming we even care about that anymore (we might!).

We're clearly going to need to run the explorers differently, since proceeding at 1/100 lightspeed and waiting 250 million years for the explorers to get to Andromeda is really not optimal anymore, nor is the randomly expanding-in-all-directions thing going to work for us. We need to be a lot more goal-oriented now.

Also, intergalactic space is really, really thin. The most we're going to be able to expect is maybe 1 star every 1000 light-years and the mineralogical pickings may be slim once we're away from places where Type III supernovas have happened (though maybe building everything out of aluminum will work just fine). But there are indeed going to be stars. Assuming we can find 2500 systems vaguely lined up 1000 light years apart, we can then have the explorer taking, say, 500 years to build up some energy infrastructure in a system — again, all we need is a stupid little red dwarf — to accumulate enough energy to do the next 1000 light-year hop at 2/3 lightspeed and then begin construction of that portion of the transit tube backwards towards the Milky Way, so as to generally progress at 50% lightspeed and get there in 5 million years (starting up the Replication Thing and going back to the old explorer schedule once we get close to the end) with the transit tube mostly completed.

And we'll probably want to wait an additional 2.5 million years, because, among other things it might be nice to hear back and find out that our explorers actually made it there and were able to do stuff, and also confirm that the tube's been completed, before sending the first actual payload ships with Actual People, (though I suppose it'll be possible to have the transit tube start turning payloads around if the laser ships entirely lose contact with the far end, or receive an "oops", or attain some other reason to believe there isn't actually a far end).

Because once we get into the intergalactic realm, we're now operating on timescales where evolution can happen.

In other words, this is where we're more likely to be running into Opposition.

(next up: Aliens… oh wait, I'm lying; there are a few other things to cover first)

Comments

[rmd]

Excellent batshit nerdery. Thanks!