Mini spacecraft to Alpha Centauri

[kolleamm]

The idea for the mission is that if we built a spacecraft small enough, we could push it with laser(s) to Alpha Centuri within a resonable amount of time, and once there it could send us back images of the star/planets.
My question is, would a tiny spacecraft even able to transmit the data back successfully? Would it not get canceled out by the other cosmic noise?

 

[Ibix]

Communications is definitely a problem to solve before you send the mission, yes. I don't know what space science types might have come up with, but off the top of my head: if it's going to be laser powered from home it's going to need a big solar sail (well, laser sail, I guess) which could probably be repurposed as a big communication dish. We can pick frequencies that aren't too noisy and use low data rates so we don't miss single bits. And at this end we could use a fleet of other micro craft to deploy really big antennae to receive the signals.

 

[phinds]

use low data rates so we don't miss single bits

Moderately extensive error correction schemes are more likely to give better results.

 

[Oldman too]

I've recently seen reference to using the propulsion laser as a conduit for data return, I'll try and find the page that was on for reference. It does seem that "breakthrough listen" is already focusing (no pun involved) on that area. https://www.nature.com/articles/s41550-021-01479-w
From the Abstract:
Here, we report on the detection of a narrowband signal of interest at ~982 MHz, recorded during observations towards Proxima Centauri with the Parkes Murriyang radio telescope. This signal, BLC1, has characteristics broadly consistent with hypothesized technosignatures and is one of the most compelling candidates to date. Analysis of BLC1—which we ultimately attribute to being an unusual but locally generated form of interference—is provided in a companion paper. Nevertheless, our observations of Proxima Centauri are a particularly sensitive search for radio technosignatures towards a stellar target.

https://breakthroughinitiatives.org/news/33
https://seti.berkeley.edu/blc1/

These PF threads discuss starshot points, you might find them interesting if you haven't read through them.
https://www.physicsforums.com/threads/beam-powered-propulsion-keeping-the-beam-focused.896207/
https://www.physicsforums.com/threa...ing-a-ground-based-laser.963058/#post-6110490As an afterthought, I would imagine the Proxima Centauri system is going to be high on the JWST list of exoplanet studies.

 

[Ibix]

I've recently seen reference to using the propulsion laser as a conduit for data return

Hit the mirror with a lot of laser light from the "drive" lasers here and modulate the mirror position/reflectivity to generate a message, you mean? Ingenious.

 

[Oldman too]

Ingenious.

Yes, ingenious would be a good fit for that idea. I don't understand the tech involved but it seems like a logical path to develop. I'll keep going over pages until I find the particular reference, that will describe the idea better than I can.

 

[Oldman too]

Hit the mirror with a lot of laser light from the "drive" lasers here and modulate the mirror position/reflectivity to generate a message, you mean? Ingenious.

Here is the best example of data transmission research that I've come up with at this point, no doubt there are more examples out by now but I haven't found more than oblique references besides this. https://arxiv.org/abs/1801.07778v3

I'm very surprised to learn just how much R&D is currently focused on making this Sci-Fi into Sci-reality. Trying to keep within the bounds of acceptable sourcing, I'd like to add these links regarding progress being made.
https://www.deepspace.ucsb.edu/
https://www.deepspace.ucsb.edu/projects/starlight
https://www.news.ucsb.edu/2019/019460/first-flights
https://www.deepspace.ucsb.edu/projects/wafer scale spacecraft development

It seems NASA prefers the term "Starlight" when involving it's self with Starshot, but that's likely just convenient semantics.

Respectfully, Scott

 

[Vanadium 50]

"Current technology

Is just covering their posteriors. If you have a 150 mg RTG, and it was entirely Pu-238 - i.e. zero mass to turn this into power - you have a power budget of 80 mW at launch and maybe 60 mW at destination. This is down 320 dB or so from typical radios, e.g. Bluetooth. 320 dB is not a typo.

If this signal were optical, you would be 275 dB below the star you are right next to.

Your problem is that you have a very low power transmitter right next to a high powered star.

 

[Oldman too]

Your problem is that you have a very low power transmitter right next to a high powered star.

I would have preferred the option of giving your reply an "informational" well as a "like" at the same time, I went with the like because to me that also confers informational. It would be very difficult to find a site more informational than PF.

Although I'm not familiar with the technical aspects you mention with the RTG or the power limitations of the transmission, it does make perfect sense when considered from my limited understanding. I see that signal to noise would be better phrased as noise to signal, you raise a very valid point.

I'm assuming, from my understanding of Starshot and discussions here on PF, in particular,
https://www.physicsforums.com/threads/beam-powered-propulsion-keeping-the-beam-focused.896207/ that both the propulsion as well as the communication channel transceiver would best be located in orbit or relayed from GSO, particularly if an optical link verses some other form of energy were used (I'll bet on optical). As to the power supply, I'm imagining that powerbeaming will be a strong contender. I recently posted something on that in the SS & launch info or traveling to Mars thread but here's an example link, https://nps.edu/web/eag/emerging-game-changing-technology-power-beaming

I see that the early power estimations by Starshot called for a 100 GW phased array system, not sure yet if that's been revised but whatever power source is utilized, that should keep the engineers sharpening their pencils for some time.

I'd like to see @kolleamm post back with any thoughts or questions. I believe the Di- part of Dialogue is what makes a forum most beneficial for everyone.
Thanks, Scott

 

[kolleamm]

Would the star cancel out any meaningful information being sent back with its EM interference as well?
Another thing that came to mind is, how would a small spacecraft even take good photos?
Even a pair of binoculars takes up a resonable amount of space.

 

[Oldman too]

There are some interesting prototypes already being tested.
From: https://www.news.ucsb.edu/2019/019460/first-flights
"The spacecraft prototype worked flawlessly and collected more than 4000 images of the Earth in what Rupert said was “an excellent first flight and it will evolve dramatically from here.”
This was a balloon launched test in 2019, 105,000 feet.

On the signal cancelling question, that's way above my level for an answer. There
are folks here who can give a much better explanation than I can give or even grok,
@Vanadium 50 in Post #15 gives a good example from a much more knowledgeable perspective.
That post would be a good one to study as to the science of signal strength and interference. I do have a lot of faith in science to overcome current problems, especially when hundreds of millions of dollars get thrown into R&D.

 

[Vanadium 50]

After some thought, I concluded that if you have the ability to see a 60 mW signal from 4 ly away, broadcasting for an hour or two, you probably have the technology to observe any planets directly over the 20 year trip. These radiate ~10¹⁷ watts, or about 20 orders of magnitude more power for 5 orders of magnitude more time.