Researchers with the UCSB Experimental Cosmology Group (ECG) reached a major milestone by successfully testing a prototype version of system carried by a high altitude balloon. They plan to continue improvements and eventually have a laser-propelled interstellar StarChip spacecraft.
They want the Starchips to weigh about one gram and have the cameras, radios and other systems.
Breakthrough Starshot is a $100 million research and engineering program aiming to demonstrate proof of concept for a new technology, enabling ultra-light unmanned space flight at 20% of the speed of light; and to lay the foundations for a flyby mission to Alpha Centauri within a generation.
SOURCES -UCSB, Universe Today
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There is a possibility that the endurance issue helps the power issue. Because there is one more source of power… high power. And that is your 4.6% of C. When you reach the heliosphere you hit a bunch of ions at 4.6%C… and there’s a lot of power there. For a short time anyway.
The gravitational focus is actually more of a line than a point; The “focus” appears as a ring around the lensing star, which moves away from the star as you get further away. 550 AU is just about where it gets far enough from the Sun to not be lost in the glare.
And, conveniently, you’ll be traveling parallel to that line, not perpendicular, which will stretch out the period when you’re in a good position for sending.
The real problems are power, (No PV is going to work that far from a star!) and background noise. Because the image resolves to a circle around the star, not a point, there’s going to be a LOT of luminous stuff in line with the image.
So I don’t really see it as practical for a probe this size. But it’s still the best bet. Especially if you can get the probe onto a line that points directly towards the sun, because then you can send a telescope to the opposing focal line of the Sun, and collect a lot more of the signal. Might be practical then.
https://www.centauri-dreams.org/2009/11/06/the-gravitational-lens-and-communications/
Yep, you’re right — I missed the “detail” of a fly-through, picture taking (under high PV power conditions) followed by a drift to E₁, then pointing back at Earth to do a high-speed data squirt. It is kind of a remarkable-precision one-shot chance though. Once the prime focal spot is passed, well … its past.
Let’s see.
Geometers, come to arms.
Trigonometers, get out your slide rules.
Metrologists, your calipers…
Distance to αCen is what, 4.1 LY?
4.1 LY × 365.25 d/y × 24 h/d × 60 min/h × 60 s/min × 299,792,458 m/s
… = 3.8789×10¹⁶ m
And E₁ is what, 550 AU or so?
550 AU × 149.5×10⁶ km/AU × 1,000 m/km
… = 8.2225×10¹³ m
And “target Earth” has a target resolution angle of
d = 1,000,000 km (say… in round numbers, and…)
D = 3.8789×10¹⁶ m
a₁ = 1,000,000,000 m ÷ 3.8789×10¹⁶ m
a₁ = 2.578×10⁻⁸ radians (÷ 2π × 360° × 60 min/° × 60 sec/min)
a₁ = 0.00544 arcsec
Xcrit = a₁ × 550 AU ( × 149.5×10⁹)
Xcrit = 2,121,000 m
Xcrit = 2,121 km.
Now, if one is swinging past the E₁ point at what, 0.1% c or (299,792,458 m/s × 0.001 = 299,792 m/s), then one is at Xcrit for
2,121,000 m ÷ 299,792 m/s = 7.08 sec.
NOT very long to “make the squirt” sending the entirety of “the mission” back to Old Planet Dirt.
Just saying,
GoatGuy ✓
I hope they send both the 20% interstellar probes *and* the slow probe since I want at least a slim chance of living long enough to see an interstellar mission.
They will not have much of an energy budget in interstellar space.
Well, there has been some work recently on flat imaging systems that effectively act like photonic phased array antenna. And, given power, chip scale ion propulsion has been demonstrated in the lab. Functional redundancy can deal with gas molecule strikes if there aren’t too many of them.
But, yes, I think the concept is way too optimistic in its weight budget to achieve back comm. Even something the size of Voyager would have a tough time with that problem.
If they can get any kind of micro-probe working at all at those accelerations and speeds, you can use them as part of a mass beam propulsion system for a decent sized probe. That’s my take on it. Get something larger up to speed by using the tiny probes as propellant.
Well, *maybe*, if the probes do have some maneuvering capacity, they could link up into a larger probe along the way. I still find the proposal dubious.
Oh, and the laser is proposed to be located on Earth, in a high, dry mountain plateau. (On Earth, so it can’t be pointed at Earth.) So, add getting all those gigawatts up through the atmosphere without losing focus to the list.
I think you missed an important detail: The probe would do a fly-through the inner system collecting data, and then transmit it back when it reached the gravitational focus. Not arrive directly at the focus and do it’s survey from there. The relevant positions are on the far side of their respective stars, after all, the probe has to pass the inner system to get there.
But, yeah, the data transmission problem is the real killer with this proposal, no question.
My thoughts exactly. I’d try a gargantuan superconducting parabolic antenna in the Oort cloud. There will be 95 years to build it after launch, before flyby.
Use them now in the solar system. The nano-probes can dived as close as possible into the sun and ride sunlight out to the rest of the solar system. Mass produced they would be very cheap. And you could launch millions of them at a time using a Space-X launcher.
I think a critique could best be summed up in this list:
№ 0 — Mass budget
№ 1 — Optics
№ 2 — Fine guidance
№ 3 — Back communication
№ 4 — Power
№ 5 — Endurance
№ 6 — Acceleration
OPTICS has interlocking parts. Grainy lo-rez pictures can be done with Fresnel films; for planetary imaging, much better optics required.
FINE GUIDANCE requires momentum transfers. Fuels, reaction mass, micro-rocketry, gyros. 1000 mg budget.
BACK COMM … the point of a mission evaporates if the findings cannot be returned to Earth.
POWER underlies the BACK COMM problem, the fine guidance and ultimately most of the operational problems. Nothing powerful is very compact, except PV, but that depends on being relatively close to any of the Centauri stars.
The ENDURANCE issue relates to the 24 TRILLION MILE span of Space a’tween here and there. Who knows what compendium of destructive bits might be encountered. Even gassy bits. At 4.6% of c, a single gas molecule would completely perforate a millimeter of chip-stuff. Chips don’t like that.
And then ACCELERATION. The only practical way to get to sub-c speeds is to be blazed by a ridiculously high power (gigawatt) laser. The pod, connected to a reflective “parachute” is launch forward, thus. Limited by beam divergence, budget and distance. Where’s that laser?
Anyway,
Just saying,
GoatGuy ✓
some sort of relay system? send a couple of million of these at different speeds and let them talk to each other to get the message back?
And of course the “what’s the point, then?” problem.
If we had a silver-dollar sized 1 gram chip-sats hanging out at 550 AU (grav focal point), what-all of the Inner Solar System would be imaged?
Use of curved optics is ruled out — too much mass, full stop.
Use of Fresnel type optics is all-but ruled out, resolution goes to shît, and almost cannot be improved. Use of extraordinary thin films bearing Fresnel plates (nifty interference patterns, which end up focussing) might fit the bill, as mass might be constrainable to hundreds-of-milligrams. But positioning the darn things would itself be quite the challenge.
One thing I rarely recount, but which is also important in answering the “how do we get data back?” problem, is that whatever solution to high-res imaging is crafted, the same could be used to create a usefully tight beam pointed back at Earth. Every once in awhile. If the mass budget weren’t so constrained, having large-capacity supercapacitors would help in upping the transmit power, too.
But the whole thing presently needs to fit in a 1000 milligram budget. Flog the ideas around, and it feels too tight to actually do real science AND solve the comm problem.
Just saying,
GoatGuy ✓
PS-kind-of: the other gotcha would be crafting a 1000 milligram solution that could deal with the remarkable forces of achieving 4.6% of lightspeed. A thinker…
So, you are going to keep sending them every few hours for the next how many years? And one break in the chain because one failed and that is that.
Better would be a big batch every 6 months. Send up a thousand as quickly as you can. Then they relay in unison to the next batch, and so on.
The only vaguely plausible suggestion I’ve seen involves a large telescope in the appropriate gravitational focus of the Sun, and the probe continuing on to the destination star’s gravitational focus, so that you can use both stars as gigantic optics.
Even then I expect the signal would be down in the background noise. Just not enough photons would be captured.
I think this will spin and wobble. How are you going to get a clear shot of anything? You going to put reaction control on a chip? I suppose you could have some little tubes with some powder that can burn with a little voltage. Still, will be very tricky to get it stable. Or you could have a near microscopic spinning mirror to compensate for spin. And time the frames to compensate for any other axis of motion. Hmm. That might work for the camera…might not work so well for the antenna.
One idea is to send lots of them, so the following ones will re-transmit data back.
Because of the possible failure and limited capabilities the idea is to keep sending them every few hours anyway.
Also the very propulsion laser array is meant to be the large interferometer receiver for this weak signal and the transmission is intended on slow rate high frequency photons, e. g. just a picture per probe, which is already much more than we have.
Latest cargo to ISS delivered testing equipment for X-ray communication, which is several orders of magnitude more energy efficient (per bd) than radio frequencies.
You’re going to need a LOT of wattage on that end and a hell of an antenna on this end.
Even then – teasing the signal from background noise will be very, very difficult. Lasers might help, but even then you’re talking megawatts – which are going to be tough to get from a tiny chip…
No, they don’t. They’re just sort of avoiding looking at that for now. It really IS the glaring problem with interstellar micro-probes.
Kind of like a twig floating down a stream is the precursor of a trans-Atlantic cruise ship, yeah.
I am very hopeful for this incremental development, they should learn a lot by making it step by step.
They figure out how to keep the CCD camera from jello while en route to alpha Centauri?
Do they have a solution to how something the size of a single chip can broadcast a signal strong enough to make it back here?
THe linked articles don’t address this.
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