The Universe Within 12.5 Light Years

It should be a goal for Earth to send a probe to one of those stars. As the probe will be unmaned, a mission taking a hundred years or more is not out of question.

How would it be powered?

some combination of nuclear radiation and/or solar seems like it would fit the bill? 100 years is within the useful range of a large radioisotope generator.

https://en.m.wikipedia.org/wiki/Radioisotope_thermoelectric_...

There are already plans to reach alpha centauri in about 20 years with unmanned probes (1). There still remain some technical hurdles in terms of the laser design to propel these probes afaik but it seems like this could be solved with more funding.

Too bad we are in the current era of eschewing scientific research in favor of crony politics.

https://en.wikipedia.org/wiki/Breakthrough_Starshot

One issue with the latter is that tech is likely to advance fast enough that a subsequent probe launched a couple of decades later would overtake the first probe.

Regarding the former, various studies have been made and will certainly continue to be made: https://en.wikipedia.org/wiki/Interstellar_travel#Designs_an...

Exploration of the Very Local Interstellar Medium (VLISM) will likely come first: https://link.springer.com/article/10.1007/s11214-022-00943-x

RTGs lose power rapidly as the isotopes decay, and any sort of communication over those distances requires massive power. The Voyagers are essentially dead due to this issue, and they haven’t been out there nearly that long.

I’d still settle for getting the probes out the door because no matter what advancement happens if you can’t get them into space it’s a moot point. I’d simply take something we can reasonably launch into space for research at this point.

Also, I would love to see a lunar base happen in my lifetime

This project is currently on hold, at least for the long-distance part.

https://www.universetoday.com/articles/starshot-not-get-a-re...

Solar would not work when you're out past Uranus or so, and the Sun is just a bright star with barely a visible disk. There's simply not enough sunlight out there, and you won't get enough light from your destination(s) star until you're similarly close to it.

What about a fission reactor?

Yeah given the current situation I bet China or India might end up sending those out before us.

Something like Starshot seems like it could benefit from future developments without holding back a launch today. Something with a sail can always have a laser aimed at it; maybe we launch it today with a tiny laser we fire from orbit, and in 50 years, we accelerate them to a significantly better cruising speed by firing from a laser array on the moon.

Yeah, I don’t think it will happen that fast. There are a lot of hard problems to solve, and you have to make a case for the expected scientific (or other) benefits to be worth the costs. Look at how long the JWST took from initial planning to launch, that was about twenty years, despite clear and specific objectives.

Which, to be fair, is embarrassing for the US, but is just fine as far as species achievement is concerned.

That runs for dozens of years without maintenance? And how do you dissipate the heat?

That's not an issue. Thats a good thing!

Sadly if an alien civilization sent a probe to the Sun, would we even know?

Absolutely. At the same, I would love for U.S. embarrassment to spawn another "space race".

As someone who has been fascinated by the universe and galaxies from a young age, I too thought interstellar was the way to go. Nowadays, however, I've started to feel that we've been wrongly conditioned by science fiction to see interstellar exploration as the next logical step for humanity.

Our species is still very immature ethically, socially, and politically. We haven't even learned to accept each other and co-exist happily on Earth. Our distant hominin ancestors crossed entire continents but today we set up physical borders and cultural barriers to prevent even neighborly visits. We certainly won't become the broad-minded united ethical species that Star Trek TOS/TNG portrayed within the next 2-3 centuries.

Gradual spatial expansion, and through that, gradual cognitive and worldview expansion, has been our track record. Whenever things got hairy for someone in our hominin tree at any time, they moved just a little bit more to survive.

So, I feel exploring and settling other solar system bodies should be our next logical step. There are 4 solid planets, 5 dwarf planets, and as per Gemini, ~40 moons, ~3000 asteroid belt objects, and 200000+ Kuiper belt objects, all above 10 km radius. That's a lot of nearby space to explore and more practical than interstellar. Some of them will become the solutions or refuges from our current social and political problems on Earth.

It'll take us 1000s of years more, maybe even 100s of 1000s, to do all this. Including a lot of violence, conflicts and injustice. But eventually, we will learn to develop the cooperative institutions and cognitive/ethical frameworks we currently lack to become a multi-planet species. Interplanetary cooperative institutions and technologies will emerge eventually, just like today we have airplanes, the Internet, UN, WHO, EU - institutions and technologies that, while far from perfect, seemed downright unlikely for 100s of 1000s of years of our hominin history.

It would likely need a standalone fission reactor that only ‘goes hot’ when it arrives.

I’m not sure that we have the engineering ability to actually do that with any real chance of success after a 100 year deep space flight, or the willingness to wait that long to find out.

Unlikely, but possible (if the probe was really big or really chatty in parts of the spectrum we pay attention to). Tiny probes could pass by us without us noticing them I'd think, though if they needed to send transmissions back toward their origin we might pick that up.

Open the rear end and you get propulsion as well. Just don't start close to earth

Funded by ICE, to deport illegal aliens to space.

No, you have to zap them early. Lasers still spread out (see "beam divergence"), so you have to impart most of the momentum while they're still close enough for your lasers to hit with enough power.

Sadly, that also means you have to accelerate them hard if you want to get to a decent fraction of c before they're effectively out of range. Which means your solar sail has to be really, really tough while being really, really light.

You still need matter to carry the heat, and matter is heavy (by definition!) Radiating the heat isn't going to be enough if you want to send anything other than a blob of plasma.

Which is an interesting thought when considered as a weapon. Fire a self-immolating fission reactor at your target...

I miss the days when a Bussard Ramjet was a viable dream.

Also, if there are aliens there, sending a highly radioactive blob of plasma at them at interstellar speeds might cause a little trouble.

I haven't done the math, but if we had significantly powerful lasers, shooting from the vacuum, isn't it very possible that we could actually deliver more acceleration to a far-away probe in 20 years than we could from Earth-based (or even orbit-based) lasers right now?

I have no idea what the best-case scenario for laser acceleration is.

No.

Let's say our initial boost got it up to 0.1c. After 20 years, it's gone 2 light years. If we make our space-based laser aperture really big, let's say 1km, then the light reaching our probe is something like a 25000km wide radius. That's not going to power anything.

If you slow down the initial 0.1c, then pretty quickly you're better off not sending it out at all and getting a bigger boost from your giant space laser being close for the initial acceleration.

The diffraction limit is annoying.