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This article is rather thin on detail. It says the probe itself is the size of a microchip. Let's be generous and suppose it's the size of a modern Intel x86 p
by denton-scratch 5y ago
This article is rather thin on detail.
It says the probe itself is the size of a microchip. Let's be generous and suppose it's the size of a modern Intel x86 processor. How does it communicate with Earth? There has to be some kind of antenna dish; so OK, maybe the sail can serve dual functions. How does it do attitude adjustment?
Presumably some of this chip-sized probe is a sensor of some kind; perhaps a camera. Without a sensor, it's hard to see how one could think of it as a "probe" at all. Does this camera have a lens? How big? A lens the size of an Intel processor won't capture much light, and I'm not sure the bandwidth from Alpha Centauri is going to be good enough for digital imagery.
How is the probe's transmitter to be powered? A battery no larger than a microchip seems a little inadequate for communicating between Alpha Centauri and Earth.
OK, so the probe doesn't start transmitting until it can harvest energy from Alpha Centauri itself. But now it needs a solar panel! A solar panel up to the job simply can't be made the size of a microchip.
Maybe it's not supposed to send any data back at all; maybe it's just meant as a proof of concept. But even our best telescopes can't detect something 3m wide, in the region of Alpha Centauri. So the only concept this could ever prove is that you can accellerate something to c/5; there's no point in aiming it Alpha Centauri.
The article doesn't say how long these lasers are supposed to keep running; it seems unlikely they'll stay focused on the sail much past the orbit of Jupiter. I haven't tried to do the maths, but to accellerate something the size of an x86 to c/5, I imagine the lasers will have to run continuously for over a year; how much is that going to cost, for a probe that can't send back data?
Hmm - the article is bylined "Deborah Byrd". So I click on the byline, and get a photo and bio of astronomer Theresa Wiegert. Who is Deborah Byrd?
I've never heard of earthsky.org before, but my confidence in this publication is immediately diminished on my very first visit.
- dylan604 5y ago>This article is rather thin on detail. You think? It's at the level of coming from someone's head written down on a napkin told at a cocktail party. Only, now, they've added a friggin' laser.
- stephenhuey 5y agoThis topic was discussed at length 6 years ago: https://news.ycombinator.com/item?id=11480840 https://news.ycombinator.com/item?id=11480840
- molticrystal 5y agoWould a solution be to send them off like train cars, perhaps a few months apart or sooner for redundancy in case one of the "cars derail" and aligning their paths up as they leave earth so they can act as relays and improving their designs as time go on?
- fennecfoxen 5y agoNo, easier to just target the Earth than some random invisible speck in empty space along the way. Earth is easier to aim for and you can build a bigger dish.
- JPLeRouzic 5y ago> Who is Deborah Byrd? > I've never heard of earthsky.org before https://en.wikipedia.org/wiki/Earth_%26_Sky https://en.wikipedia.org/wiki/Earth_%26_Sky
- denton-scratch 5y agoAh, so Deborah Byrd runs the site; I still don' know who the article is attributable to.
- tuwtuwtuwtuw 5y agoIt says the article is posted by Deborah Byrd. What do you mean?
- Helloyello 5y ago
- fennecfoxen 5y agoMy understanding is that the Breakthrough Starshot approach intends to use a small RTG thermocouple of a few milligrams plutonium or americium, not solar. The optics are minimal and low resolution (~2 megapixel). The uplink is slow (~2 baud) — it’s basically reflecting a laser off its own sail. That’s still going to be optically better than anything you’ll get on or near Earth because you’re near the subject. As for the time to accelerate, you may overestimate. Constant acceleration for months on end brings you to very high speeds indeed. If you’re accelerating at 1G a full year I think it’s closer to 0.9c than 0.2, I’d have to do the math to check.
- BbzzbB 5y agoCould such a probe do a round-trip if it does a 180 flip when it gets ~midway (adjusted for star brightness)?
- Someone 5y agoThis probe isn’t solar-powered, it’s laser-powered (because solar energy/area goes down too fast at larger distances. Creating and aiming the lasers for this is a technical challenge in itself) So, it could do a round-trip only if you had a similar laser set up at the destination. If you can do that, why build this tiny spacecraft?
- BbzzbB 5y agoOh crap, silly me... It slipped me that this project is/will be laser powered. I'll go into hiding now.
- Rebelgecko 5y agoChanging orientation doesn't necessarily change velocity. I don't think there's a way to "tack" 180°.
- Someone 5y agoThe 0.2 fraction comes from the article: “With the use of lasers, these researchers say, this tiny probe from Earth could travel up to 1/5 the speed of light.”
- Someone 5y agoThe article does have hyperlinks, though, pointing to, for example https://blog.seas.upenn.edu/how-to-design-a-sail-that-wont-tear-or-melt-on-an-interstellar-voyage/ https://blog.seas.upenn.edu/how-to-design-a-sail-that-wont-t... or https://breakthroughinitiatives.org/initiative/3 https://breakthroughinitiatives.org/initiative/3. The latter has a nice (and long) list of challenges to be solved.