How will we get to Alpha Centauri?

[alfa015]

As you probably know, there is a project called starshot to send nanocrafts to Alpha Centauri by 2036.

What are your thoughts? Do you think it will succeed? If not, what other alternate would you propose?

I think this live streaming of Alpha Centauri might motivate you:

[libra]

The only interstellar drive on hand that is presently workable, remain... the late Freeman Dyson, Orion nuclear pulse.
Alas, politically, it is as dead as door nail. 

(although I wonder if you could launch one to EML-2 with a SLS and / or using conventional explosives, starting the nuke drive only from EML-2 not to wreck Earth electrical grid and radiationb elts...)

[laszlo]

The only interstellar drive on hand that is presently workable, remain... the late Freeman Dyson, Orion nuclear pulse.
Alas, politically, it is as dead as door nail. 

(although I wonder if you could launch one to EML-2 with a SLS and / or using conventional explosives, starting the nuke drive only from EML-2 not to wreck Earth electrical grid and [radiation belts]...)

Using a chemical booster to lift a nuclear pulse driven vehicle to space is in effect using conventional explosives. At the low energy levels available to chemical bombs, the steady impulse of a rocket engine is much more efficient.

[daedalus1]

I presume you mean unmanned so the craft doesn't have to decelerate at the system?

[high road]

Or a generation ship? Once it costs a couple of billion USD to ship in spare parts, we're bound to make quite some progress on such technology.

[daedalus1]

Or a generation ship? Once it costs a couple of billion USD to ship in spare parts, we're bound to make quite some progress on such technology.

A generation ship has to decelerate.
An unmanned ship does not have to, so simplifying the endeavour enormously.

[Comga]

It will be easier to borrow ships from the Trisolarians and ride them back to Alpha Centauri. 
That's at least as practical as impulse propulsion with conventional explosives. 
I don't recall even Freeman Dyson talking about interstellar travel in Project Orion.

[scienceguy]

What about accelerating  a solar sail from a laser on the moon? Isn't that what they were going to use for Starshot?

[daedalus1]

Unless you narrow down the conditions of the original question i.e. manned or unmanned, orbit around the system or fly through, then this discussion is just going to get lost in too many differing discussions. As it already is, and its only just begun.

[Eerie]

The most plausible way to "get to" Alpha Centauri in the next 50 years is to build a huge space telescope and observe it. With cheap reusable rockets and in-space assembly we could construct very big segmented mirrors. Like, hundreds of meters in diameter.

[Comga]

The most plausible way to "get to" Alpha Centauri in the next 50 years is to build a huge space telescope and observe it. With cheap reusable rockets and in-space assembly we could construct very big segmented mirrors. Like, hundreds of meters in diameter.

It is taking a decade or two and ~$10B, depending on how you count, to construct the 6 meter segmented James Webb Space Telescope.
Launch is a small fraction of this, possibly 3%.
Given that telescope costs tend to grow as the square or cube of aperture, even with huge advances, a 100 m space telescope is decades and trillions of dollars away. 
Remember when the 2.4 m HST was built, state-of-the-art ground based observatories was the 10 meters Keck Observatory, about 4X
The 30 meter TMT is under construction, which is ~5X JWST.  The proportionality holds.
LUVOIR at 8 or 12 meters is under consideration.
When a 100 meter Overwhelmingly Large Telescope is built, perhaps a 25 meter space telescope will be feasible.

Maxar has a contract to build an segmented radio dish to be assembled in space as part of the Restore-L mission.
This is only a few orders of magnitude less precise than a segmented optical telescope.
"Soon.  Real Soon."

But you are correct.  It will still be much cheaper than physical interstellar travel.

[Paul451]

The most plausible way to "get to" Alpha Centauri in the next 50 years is to build a huge space telescope and observe it. With cheap reusable rockets and in-space assembly we could construct very big segmented mirrors. Like, hundreds of meters in diameter.

It is taking a decade or two and ~$10B, depending on how you count, to construct the 6 meter segmented James Webb Space Telescope.Launch is a small fraction of this, possibly 3%.
Given that telescope costs tend to grow as the square or cube of aperture, even with huge advances, a 100 m space telescope is decades and trillions of dollars away. 

If transport is cheaper than size. The answer is to send it out to the gravitational focal line of the sun. Adds a primary "lens" bigger than the sun.

Only works for one target per telescope, but it's still cheaper and easier than an interstellar probe.

[Coastal Ron]

The most plausible way to "get to" Alpha Centauri in the next 50 years is to build a huge space telescope and observe it. With cheap reusable rockets and in-space assembly we could construct very big segmented mirrors. Like, hundreds of meters in diameter.

It is taking a decade or two and ~$10B, depending on how you count, to construct the 6 meter segmented James Webb Space Telescope.
Launch is a small fraction of this, possibly 3%.
Given that telescope costs tend to grow as the square or cube of aperture, even with huge advances, a 100 m space telescope is decades and trillions of dollars away.

The cost of the JWST is not fixed to size of the telescope, but more based on the length of time it has been in development, and the technical challenges they needed to overcome to make the telescope work for years without the need for repair.

However once you have inexpensive access to space, the design of a space telescope can be changed to take advantage of the lower cost transportation - which also provides for large payload volumes. Add on top of that the ability to assemble and test the telescope in LEO before moving to its final destination, that addresses many of the reasons why the JWST is so costly.

And if you can remove politics from the total build cost, then the cost really goes down. 

Ah, one impossible thing at a time...

[high road]

The most plausible way to "get to" Alpha Centauri in the next 50 years is to build a huge space telescope and observe it. With cheap reusable rockets and in-space assembly we could construct very big segmented mirrors. Like, hundreds of meters in diameter.

It is taking a decade or two and ~$10B, depending on how you count, to construct the 6 meter segmented James Webb Space Telescope.
Launch is a small fraction of this, possibly 3%.
Given that telescope costs tend to grow as the square or cube of aperture, even with huge advances, a 100 m space telescope is decades and trillions of dollars away. 
Remember when the 2.4 m HST was built, state-of-the-art ground based observatories was the 10 meters Keck Observatory, about 4X
The 30 meter TMT is under construction, which is ~5X JWST.  The proportionality holds.
LUVOIR at 8 or 12 meters is under consideration.
When a 100 meter Overwhelmingly Large Telescope is built, perhaps a 25 meter space telescope will be feasible.

Maxar has a contract to build an segmented radio dish to be assembled in space as part of the Restore-L mission.
This is only a few orders of magnitude less precise than a segmented optical telescope.
"Soon.  Real Soon."

But you are correct.  It will still be much cheaper than physical interstellar travel.

Well, there's a 9m diameter launcher on the way that would have made JWST a ĺot cheaper. No segmentation required. After that, it's back to segmentation. But hopefully in space assembly has some effect too.

[Eerie]

It is taking a decade or two and ~$10B, depending on how you count, to construct the 6 meter segmented James Webb Space Telescope.
Launch is a small fraction of this, possibly 3%.

You know what? I bet for two decades and ~$10B, SpaceX could build a much larger space telescope.

[daedalus1]

Ok. So that makes it a very much more complex problem. Not least with having to keep the humans alive for a very long period of time as well as carrying the means to decelerate at the system.

I suggest you change the title question to manned, so it doesn't get filled with lots of irrelevant comments and answers.

[Nomadd]

The most plausible way to "get to" Alpha Centauri in the next 50 years is to build a huge space telescope and observe it. With cheap reusable rockets and in-space assembly we could construct very big segmented mirrors. Like, hundreds of meters in diameter.

It is taking a decade or two and ~$10B, depending on how you count, to construct the 6 meter segmented James Webb Space Telescope.Launch is a small fraction of this, possibly 3%.
Given that telescope costs tend to grow as the square or cube of aperture, even with huge advances, a 100 m space telescope is decades and trillions of dollars away. 

If transport is cheaper than size. The answer is to send it out to the gravitational focal line of the sun. Adds a primary "lens" bigger than the sun.

Only works for one target per telescope, but it's still cheaper and easier than an interstellar probe.

Buying a box of doughnuts is cheaper too. But it doesn't really address the question.

[dror]

I'd think it has to be some sort of propelantless propulsion, at least for the later stages, and we have some possible concepts already.
The first three stages may be:
1. Reusable chemical to orbit
2. Chemical to Sun or planetary sling
3. Chemical at planetary Oberth or
3. thermal at Sun Oberth manuver

At this stage the long term high speed mechanism will be deployed. I'm thinking about a magnetic sail because it can be used both for acceleration and deceleration at the target with some maneuverability  without expending propelant. Could be a physical sun sail or electrical based instead.

Capturing at the target and landing is beyond me, but after the first robotic missions will inform us better, that could be figured out.

I believe such a mission can't possibly be done in less than 50 years from launch to capture, I'd like to know if someone can make a more calculated guess.

[libra]

Buying a box of doughnuts is cheaper too. But it doesn't really address the question.

ROTFL

Such a Simpson-esque answer ! 

[Paul451]

As you probably know, there is a project called starshot to send nanocrafts to Alpha Centauri by 2036.
What are your thoughts? Do you think it will succeed? If not, what other alternate would you propose?

The original post only mentions nanoprobes like Breakthrough-Starshot's Starchip, a magic postage stamp turned space-probe. The gap between that and a manned mission is... a lot. So if you intended the question, "How could people travel to Alpha Centauri" then both the title and original post need to be changed.

The most plausible way to "get to" Alpha Centauri in the next 50 years is to build a huge space telescope and observe it.

Given that telescope costs tend to grow as the square or cube of aperture, even with huge advances, a 100 m space telescope is decades and trillions of dollars away. 

If transport is cheaper than size. The answer is to send it out to the gravitational focal line of the sun. Adds a primary "lens" bigger than the sun.
Only works for one target per telescope, but it's still cheaper and easier than an interstellar probe.

Buying a box of doughnuts is cheaper too. But it doesn't really address the question.

If "the question" is an interstellar probe, then yes it does. A kids' telescope at the gravitational focus would delivery more science of a higher quality, probably better than even a New Horizons sized interstellar probe.

Any speed that allows a flyby in our lifetime will whip through the system with barely any time for observation. 10% of lightspeed means you transit one side of the system to the other (say 100AU total) in less than 6 days. The inner system (say 10AU) in less than 14hrs. That does not give you time to do a decent survey, therefore you are limited to imaging planets that have already been detected. And observation will generally be limited to multi-AU distances because you are limited to observing an entire solar system from a straight-line fly-through path, and trajectory accuracy is not going to be high. A telescope at the gravitational focus can remain on-station for its entire lifetime, say a decade.

[Starchip's are meant to decelerate into the system. But they are tiny. We're talking sub-cellphone level instruments.]

The distance to AC means bandwidth will be _slow_, so data will be even more limited than simple lack of observation time. A telescope at the gravitational focus is over 300 times closer, allowing faster, higher-bandwidth communication. Still slow. But vastly faster than an interstellar probe of the same size, and orders of magnitude faster than an interstellar probe of the same cost.

To be practical, any interstellar probe would obviously have to be small (Starchip being an extreme example), limiting telescope size, number/quality of instruments, and especially power available, so the observations it could make of most targets in the AC system would probably be equal or worse than a mundane "big" telescope near Earth, like JWST, or any of the 10m+ scopes on Earth.

A gravitational lens array would be superior, cheaper, quicker to deploy, and, technologically, be developed sooner. After all, if you can reach AC, you can, by definition, reach 700AU with a much larger probe for the same price.

Obviously, if the OP meant a manned mission or colonyship to Alpha Centauri, then there's no comparison. But the original post only talks about Starshot, and I responded in that context.

[edit: Some words.]