Only in the sense that staying here on Earth is also a suicide mission. Life: You’ll never get out of it alive.
I have no idea whether a gamma ray or x-ray communications laser pointing at us from another solar system could be dangerous, but it SOUNDS dangerous. That’s enough for most people. It would never fly, politically speaking.
Perhaps many. As has already been noted, the planet hunters can’t yet find an Earth-sized planet orbiting an Sun-like star. There might be many that we simply can’t yet “see.”
Solar sails provide inadequate propulsion impulse for anything beyond the asteroid belt as solar flux drops off as a square of distance. At Jupiter’s orbit (at about 5.2 AU) is less than 4% of what it is at Earth orbit. Nuclear pulse propulsion (like the Project ORION concept) is inadequate for interstellar transportation; the specific impulse just isn’t high enough (peak I[sub]sp[/sub]~10,000 seconds, where as a minimum I[sub]sp[/sub] for a practical interstellar vessel is >100,000 seconds). I don’t know anything about this EmDrive concept other than it claims to be a reactionless drive and would rewriting some basic physics in order to work. There just isn’t a practical method of propulsion that currently exists to propel a probe or vessel across interstellar distances in any reasonable timespan.
To give this perspective 20 light years is the same distance that the Earth travels in its orbit (at a speed of ~30 km/s) in over two hundred centuries. Until we have some means to significantly increase propulsive capability in order to accelerate a probe up to a useful speed and decelerate it at the other end, there isn’t any reason to consider sending a probe to another system. The effort and cost would be far better spent on developing propulsion technology and improving our means to understand other systems from here.
This is a concern borne out of pure scientific ignorance. Not only is the cosmic radiation environment far more energetic than any x-rays or gamma rays we could produce (and mostly filtered out by the atmosphere), the actual intensity of a communication laser from another system as measured at Earth would be insignificant. You actually wouldn’t want to make it more powerful than absolutely necessary to detect, as that would require more energy on the transmitter end.
Stranger
Of course it is. So? How often is policy driven by knowledge, and how often by ignorance? Logic would argue that the former is more frequent, but I wouldn’t count on it. Especially in recent years. Sad, really.
The question no one has attempted to address is: how long would it take to build a solar system wide interferometer?
My position is more or less along the line of SmithCommaJohn’s. I agree we don’t have the technology to build a reasonable star probe now. However, we are far more likely to direct resources at such a probe over the coming decades than we are to build enormous scientific instruments for no better reason than to cut a couple of light years off the trip. What is the comparative cost in improving the target from the 87th nearest system to, say, the 67th nearest system? Who is going to win that argument about allocation of resources?
We could do that with existing technology or a very small extension thereof. You’re basically talking about an array of James Webb Space Telescopes in solar orbit, coordinated to observe the same area of the sky at the same time.
It’s impossible to talk about costs of a concept that is in such a speculative state, but before you invest hundreds of billions or trillions of dollars into sending a probe on a journey for decades or centuries, you’d definitely benefit by knowing as much about the various targets as you possible can by observation. Why waste time going to a system with a handful of uninteresting gas giants when you might find a system with a more Sol-like distribution of planets, or a planet that shows some indication of life-like activity like a highly oxidizing atmosphere. When you only have one or two shots at a mission, you do everything you can to know as much as possible about the target in order to design the mission for optimum scientific benefit.
However, I don’t think anyone is going to be willing to fund a mission that doesn’t yield results until the originators are long dead. We’ll be using passive observation methods and inference in order to “explore” other planetary systems for the foreseeable future.
Stranger
How are you proposing that the telescopes communicate with each other, with sufficient bandwidth to do interferometry? You could probably do well enough with radio, or even microwave, but near IR or visible would be a huge challenge.
They would need to have a system to regularly synchronize internal clocks based upon some external reference. For spatial reference you’d probably need a secondary telescope that relies on some fixed astronomical points, corrected for parallax. With enough points you should be able to refine the orientation to any desired precision down to your sensor’s resolution capability. The interferometry itself would have to be done in post-processing rather than real-time imaging. It’s not a trivial control and calibration problem for certain, but I don’t think it is beyond feasibility.
Stranger
Do we even have good enough clocks and data storage to make that possible? You need a temporal resolution significantly better than the light frequency to make post-processing interferometry possible.
The interstellar mission is a multi boot strap step at a time mission.
First you need a fleet of deep space telescopes, and a couple of decades of observations on their own orbital pattern to create a virtual telescope with a ten or twelve AU aperture. Then you need a few more decades with your virtual instrument to do extensive studies of the near solar regions to ascertain the most probable safe route out.
Now you have a solid base line for your home base. You begin your engineering practice in long term use system design, and at the same time build your next step: Oort Cloud Telescopic Observation Platform Unification System.
Eventually, your 100 AU system is functional, and reliable over its second century, and your state of the art is ready to attempt launching multi-century projects. You also have a vast number of surveys of the local stellar systems, and some pretty impressive mapping of the nearer ones. Using Oort Cloud objects as reaction mass resevoirs, and long term orbital mechanics to slingshot to reasonable interstellar velocities (going in and then out to stay in proximity for long enough to get very accurate trajectories) in only a few more decades. Now you can cover the near neighborhood in Parsecs per century rates that make your new reliability usefull.
It’s about standing on the shoulders of giants. Or a whole lot of dwarves.
Tris
No matter how long term you go, I don’t think it’s actually possible to get to speeds greater than twice the escape speed of the solar system using orbital slingshots. That’s nowhere near the few percent of c that you’re talking about.
But couldn’t you use the slingshots to increase the total amount of mass you could get up to twice escape speeds, and then use it as reaction mass to get up to much higher speeds? (I admit that does not solve the slowing down problem at the other end.)
Tris
I have read of a similar application with the most recent generation of satellite imagery systems to allow for higher resolution images than possible from a single camera (and of course, three dimensional imaging) by using slow group velocity signals to interpolate between two or more signals, allowing an increase in effective spectral resolution. I don’t know the technical details of these systems or whether it is in fact practical to apply them to signals collected from an interstellar source by receivers separated by several AU, but it doesn’t seem to be physically impossible to apply the same principle.
Stranger
Solar escape velocity at the Sun’s surface is ~6.2*10^5 m/s. That’s approximately 0.2% of c. And you can only get a momentum change of twice the escape speed if you are basically standing still at the boundary of the Sun’s influence, essentially following a u-shaped parabola. Nothing is free in orbital mechanics.
Stranger
Every little bit helps, but it wouldn’t make much of a difference.
Also, it should be noted that it does help at the other end, too: Provided you get a good ephemeris for objects in your destination system, you can use the same slingshot processes in reverse to slow you down.
How much longer will it be until it would be faster to send a probe ‘now’ than to wait for a better technology to become available?
Wow, progress IS quick…
A self repairing self replicating nano tech would seem to be a way if we could manufacture a power source that lasts that long.
Barring that something may be able to be placed in a deep freeze near absolute zero (deep space is near that isn’t it). Then it would thaw out when it approached the star, perhaps a battery, fuel cell or solar array could survive in deep freeze without deteriorating.
You’d need insane accelerations to make that practical. If you’re not thawing out until you’re that close to the destination star, you’re going to have a ridiculously short distance in which to do all your deceleration.