Is an interstellar probe possible now?

[Forbin]

Got thinking about how aggrevating the slow pace of space exploration is compared to how I thought it would be when I was a kid watching Trek.

Aside from the fact that NASA would never be given the money to do it, is it currently possible, with current tech, to build a probe that could get to Alpha Centauri system in a reasonable amount of time? Reasonable meaning, say, before I freakin' die?

I'm thinking constant-acceleration ion drive. Could it get a Galileo-sized probe up to a reasonable enough percentage of C that the trip there would NOT take decades? How fast could we get one there with current tech? I guess that includes time to decelerate so it has time to do some science at the destination too.

I'm just tired of my imagination going faster than the real world.

 

[Leandar]

I don't think so. It's still gonna take some advances that we haven't gotten to yet. The fastest probe right now is the New Horizons probe and at the speed that it's traveling, about 12 miles per second, with the Alpha Centauri trinary being about four light years, or approximately 25 trillion miles, a ship traveling 12 miles per second would take, if my calculations are correct, more than sixty-six thousand years to reach Alpha Centauri. I think that it's gonna be quite a while before we get to the point where we can send something out that far and get information back within our lifetimes.

 

[Alpha_Geek]

...and remember that the average speed would end up being somewhere around half your maximum speed since you'll need to pitch over at midpoint.

Wouldn't want to get there only to have your camera travelling at some speed that'd make observation of the destination system impossible, would ya?

AG

 

[USS KG5]

I'm just tired of my imagination going faster than the real world.

The one thing Trek gets consistently right is that Earth's problems are solved so vast resources can be put into space exploration, in our reality things just do not work that way.

Even if you assumed that 100% of the population saw space travel as a priority (in reality I would be surprised if it were as much as 1%) there would still be massive global economic and social problems to solve first. How can you justify spending trillions on going out into space when half the world's population lives in poverty? What kind of message would that send to any life forms we encounter?

Maybe things can change. Maybe trek is right, and at some point contact with alien life will make humans less self centred and provincial, and spur us on to get out there and see the universe instead of fighting amongst ourselves.

Sadly - it is unlikely. It is not really the tech which is the issue (though we certainly do not have it currently) it is the lack of funding and willpower of an indifferent world that scuppers space exploration. Maybe that is quite the correct way for things to be until the human race can be a more positive influence out there...

 

[Forbin]

^That's kinda part of my question - what IF the cost and morality was not a factor? Can we work out the tech right now? Well, actually, I think we already HAVE worked out the tech, but, money and society aside, do we have the ability to build it now?

 

[All Seeing Eye]

wouldn't the time it takes to get to proxima and the speed of the probe rely heavily on how large the probe would be and how much Xenon propellent is kept onboard for the Solar Electric Propulsion?
I would have thought that the more propellent there is onboard the faster it could go.

 

[Alpha_Geek]

Solar power ain't gonna do much good past the Oort Cloud, Taccy....and it's a long, long way to the next gas station.

To answer your question, it has to be a balancing act, you can't simply add more fuel because there comes a point of diminishing return versus the thrust of the engine. We've discussed a very similar hypothetical question eslewhere. The answers haven't changed.

 

[All Seeing Eye]

^ I thought the solar electric propulsion system just electrically charged Xenon gas that got ejected out the back? or did I get the name wrong?
I know solar has to do with the sun but I just thought there was some other reason it got called Solar electric.

 

[TEH BABA]

Why not nuclear power?

 

[Ronald Held]

Without fusion or antimatter, I cannot see the trip being made in a reasonable short period of time.

 

[c0rnedfr0g]

^That's kinda part of my question - what IF the cost and morality was not a factor? Can we work out the tech right now? Well, actually, I think we already HAVE worked out the tech, but, money and society aside, do we have the ability to build it now?

we have definitely not worked out the tech

 

[Alpha_Geek]

^ I thought the solar electric propulsion system just electrically charged Xenon gas that got ejected out the back? or did I get the name wrong?
I know solar has to do with the sun but I just thought there was some other reason it got called Solar electric.

previous ion powered craft used solar power to create a difference in charge between the working mass (Xenon) and the engine, which makes the gas to move aft and out of the engine.

See
http://en.wikipedia.org/wiki/Image:Ion_engine.svg

or

http://en.wikipedia.org/wiki/Image:Wfm_hall_thruster.svg

for popular types of ion engines.

For interstellar usage, there just isn't going to be enough light to collect to produce the electricity needed.

Teh Baba ahs a point though, a set of RTGs may work nicely, but still, interstellar is a long long way, and even the RTGs on the Voyager craft are approaching stone cold and will be unable to power any onboard instruments after 2025.

Incidentally, Voyager 1 is currently the most distant manmade object, at a bit over 104 AU from us. That's 0.001664 kight years.

AG

 

[Zachary Smith]

...and remember that the average speed would end up being somewhere around half your maximum speed since you'll need to pitch over at midpoint.

Wouldn't want to get there only to have your camera travelling at some speed that'd make observation of the destination system impossible, would ya?

AG

Why assume the same drive for acceleration and braking? Wouldn't it be possible to design a craft with, say, a nuclear powered constant thrust ion-drive and allow it to continue to accelerate to maximum until arrival, then utilize a much more powerful, but short term use chemical braking rocket to decelerate?

 

[Alpha_Geek]

...and remember that the average speed would end up being somewhere around half your maximum speed since you'll need to pitch over at midpoint.

Wouldn't want to get there only to have your camera travelling at some speed that'd make observation of the destination system impossible, would ya?

AG

Why assume the same drive for acceleration and braking? Wouldn't it be possible to design a craft with, say, a nuclear powered constant thrust ion-drive and allow it to continue to accelerate to maximum until arrival, then utilize a much more powerful, but short term use chemical braking rocket to decelerate?

Possible but not efficient, because the delta vee is nearly the same for both accelerating and decelerating. By using different motors you're adding weight to the craft that you probably can't afford, whereas using the same motor you only need to add more fuel and fuel storage.

 

[Lindley]

It seems to me that any probe designed to undergo high-stress deceleration after a journey that long is *asking* for something critical to break.

 

[Zachary Smith]

...and remember that the average speed would end up being somewhere around half your maximum speed since you'll need to pitch over at midpoint.

Wouldn't want to get there only to have your camera travelling at some speed that'd make observation of the destination system impossible, would ya?

AG

Why assume the same drive for acceleration and braking? Wouldn't it be possible to design a craft with, say, a nuclear powered constant thrust ion-drive and allow it to continue to accelerate to maximum until arrival, then utilize a much more powerful, but short term use chemical braking rocket to decelerate?

Possible but not efficient, because the delta vee is nearly the same for both accelerating and decelerating. By using different motors you're adding weight to the craft that you probably can't afford, whereas using the same motor you only need to add more fuel and fuel storage.

I understand the weight factor and the (seeming) illogic of hauling eqipment and fuel along the entire journy and using it only for a short while during the very last stages. At the same time, wouldn't it make it possibe to spend, say 22 years accelerating and 3 years decelerating (maybe using bursts from a chemical rocket) and get someplace in 25 years instead of 20 years accelerating and 20 years decelerating to get there in 40?

It seems to me that any probe designed to undergo high-stress deceleration after a journey that long is *asking* for something critical to break.

Well, there's high-stress deceleration and there's HIGH-stress deceleration. Admittedly, you don't want to stop the thing like hitting a brick wall. Instead, you'd want to do something mroe akin to tapping the brakes several times to slow down.

 

[JustAFriend]

Technically, the Pioneer and Voyager probes ARE interstellar probes (as they have left what we classically consider the boundaries of the solar system.)

Now all you have to do is wait 50,000 years for them to come near anything.

...and they are the FASTEST objects Man has ever created so, no, we haven't really worked out the tech yet...

 

[Timo]

It might turn out that the best way to decelerate at destination is to run smack into the local star.

I mean, we can build electronics today that withstand being fired off a cannon. (Hell, we could build primitive vacuum tube detonation time calculators that withstood being fired of an AA cannon, back in WWII!) Just keep on accelerating, and aim carefully, and then slow down in the outer gaseosphere of the star at something like ten thousand gees, riding on a cushion of one's own shockwave.

That might not be enough for getting down to "capture speed", but it would slow down the probe enough that it could do a meaningful flyby survey, and perhaps send further survivable impactors into target planets.

Timo Saloniemi

 

[Bill Morris]

It's a tall order, but a couple of not-so-costly possibilities come to mind. One is polywell fusion. The U.S. Navy funded the lastest prototype the WB-7 and looked at the data but still hasn't coughed up the $200 million needed to build a full-sized model, which is what is needed to see if it can operate at over unity. That would be five feet in diameter. A bonus of the polywell design, if it works, is that it can easily be configured to power a spacecraft, even though that's not its primary intended purpose.

Another is the recent discovery that positrons (antielectrons) can be produced in quantity rather easily, by zapping a 1-mm sheet of gold with a laser. Develop a containment bottle, and you've got antimatter for real, not antiprotons but antielectrons, which NASA has opined would be easier to deal with than antiprotons, anyway, not to mention easier to produce.

Either way, you've got more energy per kilogram of fuel than with chemical rockets, and much lower overall cost, but you still need reaction mass, which might be a teflon rod (vaporize the end a little at a time to get propoulsion until it's all gone) or whatever, but the next star is still a long way off. So maybe a Bussard ramscoop to pick up the trace hydrogen in space would be necesssary.

 

[ConRefit79]

The amount of fuel required to accellerate an ION powered probe to 1/10C would be enormous. Our best bet right now would be a solar sail. After a certain point, it would require additional propulsion from a powerful laser to continue to push it. Of course we don't have much experience with that form of propulsion, but it is the only one that does not require the fuel be taken with it. At 1/10C it would take 43yrs to reach Proxima Centauri. That does not take into account the time it would take to accelerate a Solar Sail probe to 1/10C. Once there, the light from Proxima Centauri would have to be enough to slow it back down to get any decent research accomplished.