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Interesting study on interstellar probe

Posted by: Ekkehard Augustin - Wed Jul 06, 2005 12:05 pm
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Interesting study on interstellar probe 
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Post Interesting study on interstellar probe   Posted on: Wed Jul 06, 2005 12:05 pm
The article "Voyage to the Stars: NASA Study Mulls Options" ( www.space.com/businesstechnology/050706 ... oyage.html ) say that in 2014 a small interstellar probe could be launched that would reach 200 AU distance in 2044 and then do on-the-spot measurements there.

A quote says "'This would be a stepping stone. A lot of people resonate with the science fiction side about taking the first step to the stars'".

The probe will have an electric drive.

What about this? And may it be that in 2014 a better propulsion technology is in use which shortens the time of travel?



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Post    Posted on: Wed Jul 06, 2005 3:53 pm
Again, unfortunately, ion drive just isn't that great to push people around with. It's a very low-thrust drive, meaning that you accelerate at something on the order of a few inches per day per day.

I'm also absolutely positive that we've had this discussion before. I remember talking about ion drives a while back....

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Post    Posted on: Wed Jul 06, 2005 4:09 pm
Hello, spacecowboy,

I too remember another thread about ion drives. They weren't the reason to initiate this thread.

My focus merely is on the project to use a very small probe and to do research of the environment in 200 AU distance. The probe will be very light and small according to that article - it would push out the frontier much farther then currently

I am wondering if there is a chance that in 2014 such a probe would be given a plasma or a nuclear thermal enmgine. Also I am thinking about progresses in miniaturization. The scientific instruments are said to weigh 30 kilograms only. And they are talking about the challenges of communictation over 200 AU.

It is looking to me as if that project would push forward technologies of several different field.



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Post    Posted on: Wed Jul 06, 2005 6:22 pm
There was an interstellar precursor mission called TAU (Thousand AU) mission.

As it turns out the solar foci is 500-800 AUs out. If you place a Hubble sized instrument there--you can use the sun as a gravitational lens to resolve pictures of extra-solar planets with as much resolution as the cameras on Apollo had of the Earth!

Imagine seeing clouds and continents of extrasolar planets.

Nuclear Thermal propulsion is best for this--with some ion drives for station keeping/fine adjustments.

Do a search for "Deep Space Mission To The Solar Foci" and see what you get.

http://www.tsgc.utexas.edu/archive/design/foci/

http://www.nidsci.org/essaycomp/cmaccone.html

In the first of the two links--you see the craft being launched by Energiya. The piece clearly states that an HLLV is needed to do this mission correctly.

Good news on that front as well:

http://www.spaceref.com/news/viewnews.html?id=1040

The sooner Griffin gets support for his vision--the sooner we will be on moon and Mars--and have these TAU type missions.

Then LEO will be a private domain. NASA leads--and private initiatives should follow--not fight.


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Post    Posted on: Thu Jul 07, 2005 12:43 pm
I've always had one question about this whole telescope deal (maybe Peter'll know).

Part I: if, as you develop telescopes, you are able to see progressively farther away; and if, as you look farther away, due to the finite speed of light you are also looking "back in time" (I'm sure all of us here are intelligent and informed enough for me not to have to explain that in detail): then, logically, you will eventually be able to focus at a point far enough away to "see" the Big Bang (or possibly God smirking at us for our ignorance, or the Great Sneeze or something like that). And of course, we know that the Big Bang is there for us to see, as we've detected the radio transmissions, etc., etc..

Part II: but, as the Big Bang was (for all intents and purposes) infinitely bright (in all wavelengths, and therefore the Doppler effect is null and void), and as the original point of the Big Bang (due to the fact that the Universe expanded directly thereafter) appears to be in all directions at once, then the sky itself should be infinitely bright from all directions already.

So is there nothing to see? Is the light from the Big Bang, by some strange twist of physics, only visible through a telescope (or just blue- or red-shifted out of the visible spectrum -- but I already assumed it was infinitely bright in all wavelengths -- maybe this is wrong), or is it, as Douglas Adams would say, just an example of a Somebody Else's Problem.

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Post    Posted on: Thu Jul 07, 2005 2:15 pm
spacecowboy wrote:
the sky itself should be infinitely bright from all directions already.

Ah, Olbers' Paradox! This is a very deep question that has been around for centuries.
http://www.asterism.org/tutorials/tut09-1.htm

The modern take on it is that the Big Bang afterglow should be extremely doppler shifted.
http://map.gsfc.nasa.gov/m_uni/uni_101bbtest3.html


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Post    Posted on: Thu Jul 07, 2005 2:27 pm
Olbers' Paradoxon consists of an infinite number of stars in an infinite large universe - spacecowboy is talking of the flash of the Big Bang.

The flash of the Big Bang really is there - the cosmic 3 K background radiation. What spacecowboy misses is the visibility of the flash in all wavelengths - as far as I understand his post.

If the number the are no upper and lower boundaries of wavelengths he is right. I seem to remember an article saying that the universe has a finite diameter of around 70 billion lightyears. The article said that this sets upper and lower boundaries for the wavelengths at which the Big Bang should be visible. Perhaps this explains why the Big Bang isn't bright at all wavelengths.

But it seems that publiusr is leading the topic out of focus - the article I refer to is talking about measuring the environment in 200 AU distance but not about watching planets orbiting distant stars. The measurements will be restricted to density of particles, gravity, radiation and the like in that distance I suppose.



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Post    Posted on: Thu Jul 07, 2005 2:47 pm
Okay. That makes sense: my argument was almost wholly based on the assumption that EM radiation of all wavelengths was emitted; however, if it functions like their final analogy (light coming down to the surface through a cloud), then the color of the cloud determines the light that comes through it, and therefore makes it possible for the light to be Doppler-shifted out of the visible spectrum.

I'd heard of Olbers' Paradox several times before (along with the CMB), and connected it vaguely with this. So that answers that question.

Of course, I'm still curious to know what it would be like to point a telescope in any direction you choose and still be looking at the same point... The apparent geometry of the Universe as seen from any single point is truly mind-warping.

Oh, and Ekke: sorry for hijacking your thread. About that probe: publius was simply mentioning another probe that would likely be a follow-up to the one you mention. In any case, a probe that is fully functional at such a great distance from the Sun would be a fascinating project to work on, and a great leap for astrophysical research.

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Post    Posted on: Thu Jul 07, 2005 4:13 pm
Hello, spacecowboy,

you are allways doing well and try to understand correctly what someone else said - so I have no problems with your question coincerning telescopes, Big Bang and Olbers while I don't trust publiusr that much no more.

To add some historical informations concerning Olbers' paradox, the CMB and so on - Olbers lived in the nineteenth century. That time astronomers doubted that there are distant galaxies and the Andromeda galaxy was considered to be an object of our galaxy like the Orion nebula. Distant galaxies were considered to be nonsense merely.

This changed in the first half of the twentieth century when telescopes of much higher resolution were available. They enbaled to see resolve the Magellanic Clouds and the Andromeda Galaxy to be resolved into stars. Their spectrum could be measured and thus the expansion of the universe was discovered - and the idea of the Big Bang was born - by Hubble if I remember right. But then the flash of the Big Bang was missed. The flash was discovered after World War II when new parabol antennas have been installed and were tested. These antennas received the CMB. It latsed a while until it was recognized that it wasn't a bug but the CMB.

Olbers' paradoxon was solved but a new question was found.

Regardless of telescopes or of researches about the environment in 200 Au distance I find such a mission interesting because of the following challenges:

- communication over that large distance
- a chance to apply other propulsions than electric ones.

For example Cosmos I could have cause a push of the light sail technology if Volna wouldn't have failed. There is a NIAc study saying that a probe of 10 kg mass would pass Pluto after 100 days if the light sail would be unfold at 3 million km distance from sun.

The paload of the 200 AU-probe has a mass of 30 kg - only three times the assumption used by the NIAC study.

A push to the soalr sail development could provide a reduction of the travle time. But the probe would have to be stopped at 200 AU - which way if a solar sail would be used?

The launch date could be pushed to the future perhaps.

Under this aspect it's much more a pity that the Vlna rocket carrying Cosmos I failed - it could have pushed the 200 Au-mission perhaps.



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Post    Posted on: Thu Jul 07, 2005 4:27 pm
The only problem with deploying your sail 3 million Km from the sun is getting there in the first place.

DOH! I probably shouldn't have said that! Peter and Ekke, please ignore that last comment!

Let's focus on the other end. Assuming you have this spectacular velocity, how DO you stop your rig when you get to 200 AU? There's no mass out there to create a gravity well, you'll have to use an impulse reaction drive. You probably don't want to use something as inefficient as a chemical rocket, lest you'd need to make your probe 20 times heavier for propellant mass. Ion drive? At that range you're talking fission reactor, those are kinda heavy, too.

To get there fast for free is going to cost an awful lot, it seems. Unless you plan NOT to stop, which may not be too terrible. Go a little slower, get there in 300 days instead of 100, put lots of instrumentation aboard, and get as much data as you can in the 2 months during which you are at 180-220 AU.


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Post    Posted on: Thu Jul 07, 2005 5:20 pm
Fast probes are best used to explore the edge of the Solar system--Kuiper objects, etc.

But a bi-modal nuclear thermal/electric system will allow a scope to stay on station for many, many years. It could change its orbit a bit and carry useful instrumentation--where a solar sail is good for a small RTG powered science craft. Sails are still best for the inner solar system until such time as we can get beamed energy propulsion like Forwards Starwisp. But these craft--the faster they go--the less they carry.

To do good science you need a Hubble mass scope out at 500-800 AU out--with plenty of juice. If you try to cheat and Holman your way out there it would take thousands of years--and to get a big craft out there means a very large solar sail indeed--so you are not going to get around the need for greater lift.

We've spent enough time chasing that faster better cheaper chimera.


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Post    Posted on: Fri Jul 08, 2005 6:35 am
publiusr,

stop your Heavy-Lift-talking here - the article I refer to in the initial post explicitly is talking of 30 kilograms only regarding the instruments. keep your posts on-topic or avoid to post.



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Post    Posted on: Fri Jul 08, 2005 3:23 pm
And how about you keeping your posts civil for a change, mister.
And there are all kinds of probes--and you aren't God and nobody said that an interstellar probe has to be under 30 kilo's.


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Post    Posted on: Fri Jul 08, 2005 4:00 pm
My answers to you are civil, mister. You had to behave correct and appropriate but didn't - I had to go against your behaviour previously in other threads and there are at least three other posters here you annoyed too.

Regarding "God" you are talking and behaving by a manner and style as if you are the one who thinks to be God and so you experinece that others don't consider you to be a God.

I initiated a thread about a 30 kilogram probe - I want it to be concentrated and focussed on that. I am allways confident that spacecowboy, SawSS1Jun21 and most of the others retrun to that if they temporarily trun to by-topics - but you have hijacked too much threads to other topics without returning to their inital topics already.

The thread has relations to the thread about System Ships and Space Ships

The referred article is reporting a realistic project - a Hubble-like telescope is NOT within its limits because its mass is much larger than 30 kg. For this reason it will be unrealistic currently because of financial requirements.

Keep your posts on-topic or avoid to post - that one is behaving as if he thihks to be God who ignores the topic and its limits, that one claims to be God who hijacks threads: That one are you yourself.



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Post    Posted on: Wed Jul 13, 2005 1:18 pm
[yawn]So how 'bout getting back to probes: as thoroughly unexciting as the overgrown toasters themselves are, they're better than watching you two b*tch-slapping back and forth.[/yawn]

Ekke: you started talking about a little probe. publius was also discussing probes, albeit larger ones. He didn't start preaching about HLLV; hell, I went off into left field somewhere. If Andy or Peter or anyone else brought up bigger probes, you wouldn't have minded. Ease up on him a bit, man.

publiusr: completely off-topic (see, Ekke?), but were you the one who wrote that first article in the latest AW&ST? If not, you and the writer need to get together, because you seem to hold much the same opinions.

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