Interstellar Flight: Perspectives and Patience

With Alpha Centauri being only 4 light years away, interstellar travel seems almost feasible. But then you consider all the inconvenient details, and realize such a journey would have to take hundreds, maybe thousands or even more years on top of some incredible advances in rocket tech.

If you go to something like Trappist (40 ly) at 0.01c (very optimistic), it's not just that everyone you know will be dead when you arrive. Your entire nation will have disappeared to the sands of time. The landfall announcement you send back will be incomprehensible because of language shifts, and you won't live to see the reply. Meanwhile, such a trip would be an enormous investment, requiring multiple nations to bankrupt themselves, with no hope of even surviving to see the outcome.

With that, it's very hard to imagine interstellar travel being feasible with our current understanding. There would have to be something like FTL travel or wormhole. The only "realistic" development, (much) better engines that can do 0.1c, would not actually change much.

Yes, we have a long ways to go before we can be considered a starfaring species, one that can make and keep long–term agreements when they involve round–trip times in the tens of thousands of years. Still, it can be useful to altruistically start colonies before then.

There’s a book called Count to a Trillion which explores these ideas, and others. At the end of it the main character’s wife sets out on a mission to M33 and isn’t expected to return for at least 70,000 years. He gets stuck on Earth, unable to catch up with her, and promises to be here when she returns. The sequel is all about what he has to go through to keep Earth a going concern while she’s away.

Worse, you have no idea what you will find on the other side and weather that includes somewhere that doesn't make the arctic poles on earth look like paradise. And you'll be traveling in a small confined space. For ages. The good news is, you'll probably be unconscious for the journey. The bad news is that a lot can happen in decades/centuries/milennia and there's no guarantee you'll actually wake up. And everything else you said.

That raises the question who would want to travel and why. And what's wrong with them. Because the profile for people that want this would be hard to distinguish from somebody that is depressed and suicidal.

> it's not just that everyone you know will be dead when you arrive. Your entire nation will have disappeared to the sands of time.

Humans are just a stepping stone. Earth intelligence will transcend our 77 year lifespans and primate brains.

Our lungs are adapted to gas exchange on this particular gravity well and its unique biogeochemistry. There's no reason redox reactions need to happen like this, or indeed even be the primary propulsion mechanism.

This is our frail biases speaking. We are limited by our biology, but we won't be forever.

Given those time frames, maybe don't send primates. Send a computer babysitting a diverse zoo of bacteria and algae, with a variety of landing devices and instructions in what order to deploy them under which circumstances.

Same problem: the best-case outcome is that we never hear anything interesting from that rocket ever again. But it should be a lot cheaper.

> it's very hard to imagine interstellar travel being feasible with our current understanding.

Even with massive advancements in tech, and getting close to the speed of light, interstellar travel will be a lot of "one way heading into the unknown forever" kind of initiative. Interstellar empires only work with truly sci-fi tech that mostly ignores distances, like in sci-fi (instant subspace comms or warp travel with no relativistic effects)

This will never be the same kind of age of exploration as when we crossed the oceans and explored our planet. The scales are so mind blowing that even the fastest speed known to mankind is too slow. The times and distances involved to move and even just send signals (both ways!) and relativistic effects means at best we can "seed" a distant planet and hope that turns into a new (human?) civilization, forever separated from us for all practical purposes.

> Send a computer

Those age too. Especially out there without the earth's shields. If you make one that lives longer than a human it's already quite the feat, add only a bit more radiation, it only gets worse. Computers are much worse with failures than brains too.

The nice thing about biological systems is the self-assembly from tiny molecule parts. Worst case, you can create a closed system with birth/death renewal. For tech the machines that build the machines, and the machines that build or repair those in turn, will all have to be brought along too, or you need to have some impossibly tough requirements for the product to last.

We may need some similar automatic self-assembly for tech for such use cases. The whole spaceship and all its components will deteriorate too.

Even when we sent out ships to venture around the world they had to be able to do replacements for broken parts, like masts. We probably need that capability for space ships too, to stop at some asteroid and rebuild. But then you get the equivalent of the rocket equation: On the one hand, you need a lot of stuff to support that manufacturing, on the other hand, every item you add itself needs maintenance and rebuilding at some point. The way out is this molecular-level self-assembly. You throw a few tiny nano-machinery dust spores on an asteroid, and ten years later you grew some useful machinery...

Maybe not humans, what about robots though?

I recently read this in an interview with Juergen Schmidhuber:

> Of course, such life-like hardware won't be confined to our little biosphere. No, variants of it will soon exist on other planets, or between planets, e.g. in the asteroid belt. As I have said many times in recent decades, space is hostile to humans but friendly to suitably designed robots, and it offers many more resources than our thin layer of biosphere, which receives less than a billionth of the energy of the Sun. Through life-like, self-replicating, self-maintaining hardware, the economy of our solar system will become billions of times larger than the current tiny economy of our biosphere. And of course, the coming expansion of the AI sphere won’t be limited to our tiny solar system.

https://news.ycombinator.com/item?id=44330850

But why would we bankrupt ourselves sending those robots at all? Although, if AI takes over in a way or another, who knows what they recommend/decide.

I’m sure if you ask ChatGPT often enough it’ll recommend exactly that!

I love science fiction because they usually try to play these scenarios in a somewhat feasible future. The 3 Body Problem series (more specifically the 3rd book) goes well into what it would take for humanity to be interestellar even without lightspeed or wormholee tech.

Avoiding spoilers it would basically be through hibernation and/or generational ships. Which basically implies of losing all ties to earth and anyone/anything you left there.

But, then again, why would nations invest in such expensive endeavours if there is no prospect of seeing something back out of it. I imagine only an emergency situation would cause this no?

I used to often hear people joke that because of Moore's law, there was no point running any computation which would take longer than 4 years, as you'd instead be better to wait 2 years for computers to double in power, then run your problem then.

Interstellar travel probably has a similar problem, even if you have an engine that can do 0.1c, you have to be sure in 5 years you won't have one that can do 0.2c, or that ship would beat you.

> it's very hard to imagine interstellar travel being feasible with our current understanding.

Sometimes it's hard realize the with have a good understanding of only 5% of what composes our universe. Let's hope there's still some surprise lest for ours Centauri Dreams...

It's always a bit revealing, with these kids of interstellar missions, how people reveal their own unseen biases.

Clearly such a mission is beyond the capabilities of our world currently. Like, obviously such a mission is something that capitalism cannot accomplish. That communism or anarchism or any -ism just cannot do. And I think that when people look at jaunts out to Alpha Centauri and think in terms of cost, they whole thing is hopeless from the get-go.

To make something like a trip out to Vega, even with just a probe one way at .1c, that's 500 years (right?). We can't fathom doing that right now as staying around to check out any answer. The ultimate 'plant trees in whose shade you'll never sit.'

Generation ships out there, even with magic hibernation tech, I just don't think we have the mental capabilities as great apes to think about this properly. The time scales, the advances in tech, the costs, just even thinking about things in this way shows to me that we're not at all ready to be serious about this.

You don't build a ship by teaching people how to hew oaks or caulk bulkheads. You build a ship by teaching people to yearn for the sea.

Space is still 'not worth it'. Until just being there in the void elicits the same feelings you get when reading about the bowsprits, white with sea-foam, before a quick and fast wind, look, we're not going to do this.

We have to love the trip itself first. The first stars until morning. The good ship to guide by them.

This exactly. Evolution is a stepping stone to engineering., which then will also be subject to evolution. (Is there a word for engineered evolution?)

The trick will be to remain -human- perhaps. Or we just accept the fate of the loser of natural selection, and are replaced by our children of an obsolete god.

I have posited an idea on how this could work and done a bit of world building in that space, perhaps I will overcome my reticence toward writing fiction and publish one day.

I've been reading some sci-fi by Kate Elliott lately. While she gets around large distances with the usual FTL tech of sci-fi, in-system space battles hew a little more to physics, so that you get situations like, "Crap! The bad guys fired all their missiles at us! We have sixteen hours to decide what to do ...." Fun stuff.

I bet you're right about emergency situations. On top of that, people have been getting on boats and pushing off into the ocean for at least 25,000 years[1] when there was plenty of good land to keep them occupied. It's not that we're talking the same time scales, but rather the fact that they probably did it despite completely unknown time scales. It makes me wonder if the right philosophy or religion will come along that makes somebody try a generation ship for non-emergency reasons.

[1] https://teara.govt.nz/en/pacific-migrations/page-1

Also the Queen song "'39", written by Brian May (who resumed and completed his Ph.D. in Astrophysics decades after his time with Queen).

Propulsion technology advances much more slowly than Moore's Law. The rate of progress in terms of ISP or maximum velocity has been approximately zero since 1969. The only way we'll ever be able to afford sending a probe to another star is with some new breakthrough technology, and disruptive technologies don't appear on any predictable schedule.

The notion of a general-purpose molecular assembler or nanofactory appears to be a pure fantasy. We don't even have a theoretical approach to making that happen.

In addition to nradov's point: double your speed, quadruple the blast energy of collisions along the way. Interstellar space (in galaxies) is not as empty as we could wish.

And the relativistic mass equation imposes a very lower upper bound. Light is slow.

I'm reading the sci-fi ExForce series by Craig Alanson. There is jumping (wormholes) and speed of light restrictions where lightseconds, lightminutes, lighthours come in to play. What you see (position of enemy ships) might not be true anymore.

Or humans with their consciousness uploaded to a silicon or other substrate.

Of course, this is in the realm of science fiction but so is interstellar travel.

Greg Egan's Diaspora has a fantastic treatment of interstellar travel - it involves sending copies of your consciousness to different spaceships traveling to different destinations. On arrival, a preset program will verify if the planel/galaxy is worth waking up to. If not, the clone is terminated.

If more than 1 clone wakes up in a hospitable environment, then you have a problem of two copies of yourself separated by light years.

In Diaspora that wasn’t considered to be a problem. Merging two individuals was almost automatic once you’d both decided to do it, and everyone participating in the Diaspora had decided ahead of time whether they wanted to sync back up at the end of it and merge. Also, it was fun that different individuals chose different conditions for waking up, and some stayed awake for the whole trip, or even all of them. Good book.

That’s not entirely true. Drexler’s books contain quite a few solutions to nanoscale engineering problems, though not for all of the problems. He designed and characterized a nanoscale mechanical system for separating CO₂ from the air, stripping the oxygen from it, then using the carbon atoms to build tiny blocks of diamond, then using the tiny diamond blocks to build macroscale objects under computer guidance.

> a pure fantasy

Yes it is, but what does that have to do with my comment? It does not change anything I wrote regardless of if it was already real, is feasible but not now, will never be possible.

We have to figure out interplanetary travel first. Crawl before you walk.

Some of my favorite sci-fi deals with monasticism and space travel.

If you were to create a constitution for a multigenerational space trip, it might look like the Rule of St Benedict. Many of the monastic rules were intended for “families” whose lifespan were intended to infinite.

There’s already some very good sci-fi on this topic, but it seems most of it is quite old. Most recent would be Babylon 5, that I know of.

A similar idea appears in a more recent short story, How It Unfolds (2023) by James S.A. Corey. The premise is using a technology called “slow light,” which can clone people and objects using “enriched light.” The National Space Agency scans a group of 200 people (not only their physical forms, but also their consciousness, memories, and feelings) and transmits several thousand copies of this data package across the galaxy. The hope is that, on arrival, each package can "unfold" into a fully reconstructed version of the original team and habitat on some distant alien world.

Ah yes! I remember that from "The expanse" as well: "let's do a meeting to decide how to evade the missile!"

I think that Physics-compliant sci-fi novels are more entertaining because the solutions (feasible or not) are more ingenious and the consequences more surprising.