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Voyager Probes Give Us ET's View
astroengine writes "For the first time, scientists have been able to measure a type of radiation streaming out from the Milky Way that in other galaxies has been linked to the birthplaces of young, hot stars. There was no way to make our own galaxy's measurement of the radiation, known as Lyman-alpha, until the Voyager probes were about 40 times as far away from the sun as Earth — any closer and the solar system's own emissions drowned out the fainter glow from the galaxy."
Pictures of young, hot, stars?! Count me in!
Voyager has to be the coolest space probe ever. It's been operating for 34 years straight and is LEAVING OUR GALAXY, still receiving commands from Earth and still transmitting data back. If that's not marvelous, I don't know what is. Anyone interested should read: http://en.wikipedia.org/wiki/Voyager_1
That must be one of the most successful space exploration projects so far, too bad it's running out of juice!
I am not sure why you say that. The costs of space technology haven't changed much at all relative to the rate of inflation, and there haven't been any important breakthroughs in launchers. The only thing consequentially different is computer capability, but a faster/more complex computer would just as likely be a liability as a bonus. Software design techniques, if anything, have gone rapidly backwards for this sort of application since the late 70s/early 80s.
It receives commands from Earth, and it's 34 years old. What's to keep enemies of the United States from sending it bad instructions, or from collecting all data it sends back to us? I realize that Voyager isn't of any military importance, but I guess this is more of a hypothetical question. Does it use some type of encryption? Is that encryption still unbreakable today? The keys haven't been compromised after all this time? Just curious.
Software design techniques, if anything, have gone rapidly backwards for this sort of application since the late 70s/early 80s.
I'd say the Mars rovers are a good counterexample of that, they're "new" and have been operating for many, many years now. Particularly when it comes to data compression the current probes have a huge leg up on the old ones. That said, yeah computers can't rewrite physics and launching anything into space is still quite expensive and they don't really go faster from it either.
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If we build the probe from neutrinos we could possibly launch it faster than light. And get the results a few years ago.
If we had known to listen to them, that is.
Launched today they would not do much .... they relied on a chance alignment of the planets that allowed them to use gravitational slingshots to get there in a reasonable time, tour most of the planets, and leave the solar system ... next time this will happen is around 2150 ...
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Oh, I don't know... electrostatic ion propulsion is already proven to be more efficient than ordinary chemical propulsion (once you get out of the gravity well).
As long as you have fuel, you'll keep accelerating, albeit at a very small rate. It might take ten or twenty years, but I reckon that if an ESI probe was launched tomorrow it'd overtake Voyager and still have propellant to go faster.
The bonus is with computer technology; that while it's gotten thousands of times faster in practically every respect, it's also gotten a lot smaller - a non-hardened computer package these days weighs no more than 3lb, with terrestrial ruggedised coming in at little more. The advantage of this is obvious: with the single biggest non-fuel component of the spacecraft now the size of a paperback, you have far less mass to push.
Of course, you don't need a screen or a keyboard in deep space, so cut the weight in half and you've got something a smidge lighter than the several hundred pounds of GE custom machine that went up with Voyager, that has its own battery, that pulls about ten Watts rather than over a hundred, that uses solid state storage, and in most cases can automagically govern its own power load (this would be why the later Shuttle missions used self-contained laptops rather than a room full of mathematicians and radio that meant data moved at the speed of speech) - I've metered my netbook off the line and found it runs on between 3-35W, averaging 11, including the screen on minimum brightness.
That said, you do need to protect the computer against hard radiation. That will obviously push the weight up, but not so much as to make it unmanageable. A couple or three pounds of lead and a steel cage to protect against EMI/RFI I think is all that is needed. The major part of the probe is then going to be propulsion systems and fuel, and the science package.
Operation Guillotine is in effect.
The costs of space technology haven't changed much at all relative to the rate of inflation
When you get away from government projects and missions you find an interesting thing. They've gone down in absolute dollars. It's not rare to find private analogues which cost an order of magnitude or more less than the government counterpart.
For example, prior to the early 80s, there was no commercial space flight of any sort. When it first opened up with offerings from Arianespace, Boeing, and Lockheed, prices were on the order of $20k per kg (to low Earth orbit or "LEO"), a bit better than the Space Shuttle. Now there's perhaps a dozen private space launch providers, some offering flight costs well under $10k per kg. So we've gone from $20k per kg in 80s dollars to under $10k per kg in today's dollars. And if SpaceX delivers, we'll be hitting $5k per kg (in today's dollars), perhaps less. The Russians have a good chance of meeting that price point as well.
It'll never be a Moore's Law thing, but we are seeing a remarkable long term decline in launch costs over a few decades. So no breakthrough in launch technology (with the exception of the creation of commercial space flight in the 80s and the possible exception of SpaceX now) yet we still manage to drop prices considerably even before adjusting for inflation.
Second, there are great economies of scale in launching tens of probes. For example, R&D is divided up over a large number of probes. There are learning curve effects from building tens of probes and part costs will go down. Now maybe building a Voyager-level vehicle wouldn't be as cheap as the original poster claimed, but I bet $3 billion can buy a lot of interstellar probes, just the same. Especially, if one cuts out the slick tools that Voyager used for its planet flybys, but which weren't used for the interstellar portion of the mission (such as the imaging cameras).
They wouldn't be using state of the art chips, but even the old radiation hardened chips needed for space travel would be an big improvement over 30 year old technology.
Probably the biggest improvement would be in propulsion. Isn't this the exact sort of mission the new ion propulsion systems would be perfect for?
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The only thing consequentially different is computer capability, but a faster/more complex computer would just as likely be a liability as a bonus. Software design techniques, if anything, have gone rapidly backwards for this sort of application since the late 70s/early 80s.
Thankfully, some of our/your assumptions about space technology are currently being proven wrong. For instance, take the Nexus One. NASA has been testing it to see if it could make cheaper smaller satellites with it, and its performance in that regard has been completely outstanding.
Granted, it hasn't survived 30 years in space yet, only time will tell on that one.
But it can survive in all kinds of extreme temperatures, all kinds of G forces, and it works perfectly well in a vacuum. And it's so small to begin with, the extra hardware it needs to power it, recharge it, move it, etc, doesn't have to be that big to begin with.
During one of its space test, the Nexus One was even strapped to the tip of a rocket and the rocket accidentally crashed back into the desert leaving a large crater, but the phone only got a cracked screen and was still fully functional otherwise.
And this is probably something that's not unique to that phone, or to Android, in particular. Consumer-grade devices, because they've been designed to survive actual consumers and sometimes even little kids, have come a long way in terms of reliability.
And granted, a Nexus One will still have bugs that would normally be intolerable in the older type of computers designed for space, but it has enough computing power to be reprogrammed remotely and compensate for most bugs that are found after the fact. And since they take much less space and weight, and are much cheaper to launch. You can launch half a dozen for a fraction of the cost it used to launch an older type of satellite, thus building a type of redundancy that we just couldn't afford to have with the older kind.
So if anything needs to improve, it's probably not our technology, but our mindset. We have good technology. That technology may not be perfect, but it should be more than good enough for unmanned space exploration at least. And it's grand time we start using it for that purpose.
Last I heard, the voyagers are about 100-110 AUs from the sun. Is the summary incorrect or do you only need to be 40 AUs from the sun to make these measurments? In which case, why is it news now and not in the 80s/90s when they reached this distance?
You're confusing antenna angular resolution with antenna effective area. The problem with reception of the Voyager probes isn't being able to discern them among other relevant signals. The problem is that the signals are so weak that they need an antenna with large area just to collect enough energy per bit to reliably overcome noise generated in the receiving system. Until you do this, you can't get a signal strong enough for your correlator to work on -- all you'll get out of the correlator is noise, because that's all that's going in to the correlator from your receivers.
Ergo, the 70m dishes.
A couple or three pounds of lead and a steel cage to protect against EMI/RFI I think is all that is needed.
At the high gamma energies found in space, lead is no better than aluminum as a gamma shield, and both are pretty anemic. 1 cm of either will attenuate high energy gamma rays by only about 50-70%.
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This seems to be a pretty good description of the Voyager telecom system. Based on this, the X-band transmitter provides 18 watts to the high-gain antenna, which has a gain of 48 dB, for an effective radiated power of just over 18 * 10^(48/10) = 1.1 megawatts. (At least at launch; I assume the output power will have fallen somewhat over the intervening decades, as the RTG output falls and RF components age.)
This sounds like a healthy amount of power, and it is, but keep in mind that antenna gain comes easy at X-band (8 GHz), and such ERP levels are common in terrestrial point-to-point microwave links. Also keep in mind that the half-power beamwidth of the high-gain antenna is only 0.5 degrees, so any alien not in that narrow beam would hear substantially nothing.
Also, to answer your direct question, the frequencies and beam shapes are different, and one has to consider the shielding effects of the ionosphere vs. frequency, but just to compare (US regulations, YMMV): AM broadcast stations (~1 MHz) are usually limited to 10 kW with more-or-less 0 dB gain antennas, for an ERP of 10 kW; but UHF TV stations (~500 MHz) may have an ERP of up to 5 MW.
Of course, there are a zillion broadcast stations, all transmitting non-coherently (some would say incoherently), but only two Voyagers, so that would have to be taken into account, too.
ESI is the way (as I said, sans gravity well effects), generation of electrical power is somebody else's problem. As you've pointed out, solar is useless as a source for deep space probes; self contained generation of power is the only option, and right now all we have is RTG. This is what ion engines have used in every practical application so far (examples that spring to mind are SERT I and II, and DS1) and until something better comes along, it'll continue to be a sink for RTGs in deep space exploration. As to your claim that there are no RTGs available: I could build a crude but functional one in about five minutes (if I had a pellet of [insert name of suitable isotope here]), and it's not as if we're short of radioisotopes suited for the task. The problem lies in a particular nation state unilaterally and unjustifiably denying any other from possessing any quantity of refined radioisotopes for any reason other than the manufacture of smoke alarms. That nation state continues to throw RTGs all over the Arctic in the name of science and monitoring the military movements of others without the need to lay thousands of miles of power lines, and there is far more than the Apollo 13 RTG sitting at the bottom of the ocean - the Atlantic passive SOSUS net buoys are all RTG powered (there is very little sunlight three miles underwater).
Operation Guillotine is in effect.
This is indeed correct. Radiation hard electronics are created at the microchip layout and design level, rather than with external shielding. It requires an understanding of the damage that occurs from ionizing radiation and high-energy particles, and implementing device layouts that are tolerant of that damage.
Let me give you a little hint: current generation designs with tiny FETs and low voltage drivers cannot operate for very long when the gate Vts start to shift.
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