It is reasonably easy to use long baseline to boost your reception sensitivity. All you need is two sensitive receivers perfectly tuned, and sufficiently far apart.
To TRANSMIT with a similar gain and focus, you need a fully-filled 2d array of similarly synchronized transmitters. This is difficult, if you try to use the Earth-Moon distance as your base leg.
Also. It is reasonably easy (not easy but doable) to synchronize a number of nanowatt receiver inputs. For starters, you don’t need to do the synch in real-time, you can have recordings that are then post-processed.
It is much,much,much harder to similarly synchronize a number of multi-megawatt transmitters. In real time.
Make them cheap to launch - each one is on the order of a kilo or so. You fire them off by the thousands, using a laser powered by a big-ass nuclear plant. Put the laser on the far side of the Moon, so no one is even tempted to shoot it at Earth.
Want to explore a star system? Mass manufacture 10,000 of the things. Fire a train of a few hundred at each planet, spaced out so they arrive over a period of days or weeks, simulating an orbit. Then fire one off every day or two until the first ones get there. Now you have a communication relay chain. As the first ones arrive they transmit data to the ones following, which pass it back down the chain, all the way to Earth… The ones following can also use data from the first ones to adjust the targets they image or sense as they go by.
Keep doing this with other star systems, and you can explore them in parallel with the same launch hardware.
The key is to make each launch as cheap as possible, so you can create many, many thousands of them and launch them. You need absolute minimum viable probes (like the Breakthrough Starshot concept). I’m thinking an automated manufacturing facility on the moon creating all the stuff of significant mass, with only the tiny electronics and control packages coming from Earth.
A system like this would be fault tolerant, could be upgraded dynamically as new stuff comes along, and would have a lot of flexibility - if the first planet encountered is a bust, the probes far enough back to be able to change course enough could re-target another planet in the system. The amount of data you could collect and transmit would be a function of swarm density, like a mesh network. And launching a train of them a few hours apart for four years gives you a communication relay all the way back to Earth. Launch with enough redundancy that you can handle a significant number of failures without compromising the system.
If you could launch these things for a variable cost of, say $100,000 each, launching an initial burst of 1000 probes over a few days, then five a day for four years would cost about a hundred million bucks. That’s in the ballpark of a small ‘discovery’ mission’s cost.
Even at a million per probe (again, only a kilo or so, launched by laser sail), the whole thing only costs a billion dollars, plus the construction of the launch and manufacturing facilities. But I assume those facilities could be amortized over many star system missions, and even used to send stuff elsewhere in the solar system.
Thanks for the correction, but could you explain how this works? I understand how VLBI can improve spatial resolution, but how dos it improve sensitivity? When you add the 2nd antenna, don’t you just turn the beam pattern from a large circle to a series of stripes? The overall area of those stripes is no better than those antennas close together.
There’s a perfect symmetry between transmitting and receiving. Both are equally difficult to synchronize.
Sam Stone, what power source does a 1-kg probe use in between stars, that would enable it to relay transmissions?
SamuelA, yes, human aging is a much more difficult problem. People joke about how fusion has been “in the next 20 years” for the past 70 years, but we’ve at least made some progress on it in that time. Human aging, we’ve been trying to solve for as long as recorded history, and made no progress at all yet.
Synchronization of VLB type systems when you’re talking about widely separated space probes moving in orbit (with their relative positions changing) is indeed quite hard.
But in terms of other symmetry issues there are some options where one can create an asymmetry that would be useful.
Take eliminating that pesky Sun, for instance. Churns out a ton of radiation. Hard for a probe on a ~straight line from Sol to AC to receive a clear signal. Send out a big relay probe out perpendicular to that path. It sends to the AC probe and will be easier for it to pick up. (Unfortunately, sending the AC probe on a path such that our reception of its signal isn’t harmed by AC is another fuel waster.)
Another is to send a series of relay probes every few years after the original. So there’s a “chain” of stations relaying data in both directions. This chain only exists between us and the AC probe.
One thing about these relays is that you can steadily improve the next ones sent as tech develops. Including increasing their speed. So the AC probe might be known to not be powerful enough to communicate with directly after a ways out. I.e., we don’t have to have solved all the problems at launch time. For me, this is one of those nice “SciFi becomes reality” type things that might happen.
I found this presentation that talks about antenna array designs for interferometers. Slide 25 shows the instantaneous point spread function of the VLA which is made up of 27 antennas in a Y shaped configuration. That would also be the transmitted beam pattern of the VLA. There is a bright central peak, but the power contained in that central peak is a tiny, tiny fraction of total power.
We know some individuals live longer on average than others due to genetic differences
We know the telomeres act as a counter and appear to be a significant system involved.
We know that proteins to re-lengthen telomeres are possible
We know that cancer is immortal as it uses these genes and we have samples of specific tumors from long dead individuals (70 years ago is one notable cell line) and they are in fact immortal.
We know that if we knew exactly which genes to change (to lengthen telomeres but not give someone uncontrollable cancer) we could do it with various forms of adult gene editing
A small number of people have been cured of easier diseases with these forms of edits
I know it’s immensely complicated and I will point out that an enormous amount more knowledge needs to be gained before you could ever develop an industrial scale treatment to negate people’s age. But current evidence leans towards the conclusion that it is possible, and the tools to do it do exist, albeit they are not developed enough.
You say that humans have been trying since the beginning: naw, not really. Or they wouldn’t be so resistant to methods that have a real chance of working. (such as immediate post death brain preservation, whether this is freezing with chemicals that block ice crystals or plastination)
You might say that the present groups practicing it are little more than cults. But, then, why isn’t the NIH investing a billion dollars a year into better methods? It’s “impossible” to preserve a brain? Says who? A preserved brain won’t record the information that encoded their memories and personality? All the evidence points towards the fact that it does.
So I thought about this, and I realize you feel your conclusion is solid. You’re not going to change your mind, no matter the links. I suspect you would just say “well until someone actually lives to 150 you can’t say a treatment for aging is even possible”.
So I have a new tactic. Economics. Fusion-engine-starships (which are much, much, much harder than a terrestrial power generator - I would say the fusion part is the very first step), what value does a working one bring to the table? Or wisp probes or whatever.
Most likely all you will get from the massive investment is a few blurred images of other dead rocks. They may be in different orbits than here, or have slightly different gas compositions than anything in Sol, but there would be no new living organisms and no new elements.
Obviously, a treatment for aging has immense and immediate economic value. Medicine is already one of the world’s largest businesses - what would it be able to charge if it could give people multiple additional decades in good health? What if people undergoing the treatment knew there was a real chance that living an additional 30 years would allow them to benefit from further treatments and advances, thus resulting in an expected lifespan of thousands of years?
Sure, whatever, some people would go to their grave willingly, but soon the entire world, culturally and economically, would be dominated by people over a century old. To die is to be a loser.
I’m a big fan of a mixed approach to interstellar flight. To get your spaceship up to interstellar speeds, use a beam of smart particles to propel a magnetic sail. Jordin Kare’s Sailbeam concept is a good start, but needs some refining.
The magsail could conceivably be reconfigured to act as a brake in order to slow the probe down from interstellar speeds, as described in various papers by Zubrin and Andrews. But this system can’t slow a probe down to orbital speeds, so you would need to be content with a slower flyby, or include some sort of rocket motor. A pulsed fusion motor using small (but not too small) fusion explosions might be enough to allow the probe enter orbit around the destination star.
Note that none of this allows the probe to be controlled at such a great distance- you really have to assume that the probe is largely autonomous. Since all of this technology is at least 100 years away, I’d expect autonomy to be very good by then.
How long after the first launch is arrival at a target star system? How many decades or centuries must that train of probes be launched before we receive planetary data? And as Chronos asked, “what power source does a 1-kg probe use in between stars, that would enable it to relay transmissions?”
There are lots of stars we can see, and we know a lot about them. Like, what they are composed of. How do we know that? Spectral analysis. Every star, including ours, has thin spots in its EM output. So, obviously, the probe’s receiver will use a combination of the frequencies that a weakest from the Sun and will transmit on the frequencies that are weakest at the target star.
And stars really aren’t all that bright anywhere in the radio range, anyway. Even here, a mere 1 AU out from Sol, it’s still only the second-brightest radio source in the sky.
SamuelA, I don’t demand someone living to 150 as evidence of “progress” on aging. I’d settle even for it becoming routine for people to live to 90 or 100. But even today, the span of a man is still threescore years and ten, or fourscore if he be strong.
I would assume something like a small RTG powering these things. If the sail doubles as solar cells, the propulsion laser could provide recharge power to internal batteries for some time, and near the sun and the destination starlight could also be used. I’m also assuming that we will have better tech in say 50 years or so to make things smaller and less power intensive. Also, a mesh network is relatively low powered compared to trying to beam data from another star system back home. Mind you, this ‘mesh’ would be separated by solar system scale distances, so maybe ‘low powered’ is not the right term here…
I’m sure there are lots of other holes we can pick in this, but the same is true for every proposed interstellar probe, as it’s not yet a solved problem. I just think the ‘all eggs in one basket’ approach is too risky for the money it would take to send a multi-ton, self-powered probe to another star system.
The reason I’m leaning in the direction of very small, very numerous probes that work together is that I think it will be a very, very long time before we could power a self-propelled multi-ton probe that could make it to another star system in a reasonable amount of time, and if we’re going to use a laser sail concept, the math doesn’t work unless the probe is very small.
Going small and numerous also reduces uncertainty - a single probe has to survive the interstellar environment for decades while traveling at very high speed - high enough that a particle the size of a gran of sand would utterly destroy it. Then after decades it would have to a few minutes to a few hours inside the other star system, and only minutes near any planet. Get that wrong, or find out that the planet is uninteresting, and you’ve wasted it all.
But with a swarm of micro-probes, you can send some to every planet. If you lose a few of them along the way, no big deal. They could even be specialized - each planet could be targeted by a handful of imaging probes, a few on high-risk trajectories close enough to the planet to get good resolution, some that just carry spectrographic cameras or other sensors, etc.
If we can’t manage a network train back to Earth, perhaps we also send one or two high-powered larger probes with them to act as communications relays. They have no sensors or anything else, and just receive data from the mesh of micro probes and beam it back to Earth with a high-gain antenna.
A hundred microprobes going past a planet once an hour and in range for scientific measurements for say 10 minutes each would give you almost 17 hours of measurements - much better than a single probe flying through. And you could do that for every planet in the system.
Finally, before we send ANY probes we will have built telescopes big enough to actually image the planets around other nearby stars (maybe 10 X 10 pixels, but better than a point source), and to also characterize their atmospheres. We’d have a pretty precise list of interesting targets we’d want to look at.
I was about to object that RTGs don’t scale very well (up or down), but then it occurred to me that you don’t need to make them out of plutonium. You might be able to make a smaller one out of americium or something. Which would of course be hideously expensive, but then, everything about this project would be expensive, so we sort of have to take that as a given.
Still didn’t get to my first question. A train of launched probes will take a LONG time to get anywhere; I doubt we’ll lase them up to a good fraction of c. Does humanity have the patience for centuries of that?
What do you mean by “good fraction”? Most suggested ideas for interstellar probes assume at least 0.1c, and that’s enough to get to a nearby star within half a century. An early career scientist who works on development of such a probe has a good chance of seeing the data before they die.
