Sending probe to nearest star.

robnissen · Jun 6, 2007

Decelaration would occur during braking into orbit around Saturn, landing on Enceladus, and returning to earth. Braking by firing a rocket engine to slow down a probe to be captured by a planet, or a star for that matter, will not work for a probe traveling at .1c. For Cassini, it was only necesarry to slow down the probe a few kms per second, for Saturn's gravity to catch it. We are nowhere close to developing a rocket engine that could slow a probe from 30,000 Km/sec (.1c) to the few km/sec necessary for the gravity of a large planet or star to capture the probe. There is NO existing technology that can do that.

MeteorWayne · Jun 6, 2007

Well, except the same technology that accelerated it in the first place. The point is it takes a long time; for a low thrust source you would spend half the trip accelerating and half decelerating. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

centsworth_II · Jun 6, 2007

"the Heliopause (sp?) and Heliosheath (sp?) are not constant distances away from earth. Instead they are orders of magnitude farther or closer away depending on which direction you travel.... I would not want to double or triple the amount of time it would take the probe to get to and through the Heliopause and Heliosheath, merely so the probe could fly by AC in 40,000 years." The parts further from the earth will have different properties than those near the Earth -- different relation to the solar wind and Earth magnetosphere. All parts should be studied eventually. Anyway, I imagine that there is some degree of choice for the probe's path depending on the date of launch. <div class="Discussion_UserSignature"> </div>

robnissen · Jun 6, 2007

Well, except the same technology that accelerated it in the first place. Your missing my point. I was referring exclusively to Orion. You may be able to blow up nuclear bombs to accelerate a probe, by exploding the bombs BEHIND the ship and pushing on the push-plate, but you CAN NOT decelerate a probe by exploding nuclear bombs in FRONT of the ship, because the ship would then fly directly into a massive explosion that would destroy the ship. Orion is a one way ratchet.

robnissen · Jun 6, 2007

I imagine that there is some degree of choice for the probe's path depending on the date of launch. Probably not, the maximum of 2 AUs of distance depending on launch time will make very little differemce in terms of a journey of a 320,000 AU trip to AC.

MeteorWayne · Jun 6, 2007

OK, I get it now. Back to ion thrusters <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

dragon04 · Jun 6, 2007

You can only speed up a ship with nuclear blasts, you can never slow it down. I beg to differ. To decelerate, you simply point the pusher plate in the direction you are traveling, and detonate bombs. <div class="Discussion_UserSignature"> "2012.. Year of the Dragon!! Get on the Dragon Wagon!". </div>

jaxtraw · Jun 6, 2007

I take it nobody followed the link I offered to the "Valkyrie"- a sensible, possibly attainable interstellar spacecraft design? <img src="/images/icons/wink.gif" />

brellis · Jun 6, 2007

hi Rob Still after a few decades the return time for data exceeds the current generaton's lifetime. Wrong, the return time for data could never be more than four years for any probe between here and AC, the data always travels at C. If the probe is going fast enough, would its transmissions back to earth not be noticeably red shifted? For that matter, (theoretically speaking) if it were traveling at the speed of light away from us, how would we hear from it? <div class="Discussion_UserSignature"> I'm a recovering optimist - things could be better. </div>

robnissen · Jun 6, 2007

Doesn't work. The way Orion gets propulsion, is that a serious of nuclear bombs are detonated behind it. The shock wave from the blast pushes the ship forward away from the blast zone, before the blast destroys the ship. Many (10s?, 100s?, 1000s?) of bombs are needed to accelerate it to .1c. Now to slow down, you would have to have the blast be at the front of the ship (in the opposite direction of travel). The first blast might slow the ship down from .1c to (say).095c, but the ship would then continue forward straight into the blast zone and be destroyed.

robnissen · Jun 6, 2007

There would be some redshift at .1c, but it would not interfere with data collection. At c, the data would never get here, but Uncle Albert assures us that our spaceship won't be traveling at c.

jaxtraw · Jun 6, 2007

You're not thinking quite straight- at least not relativistically (in a Galilean/Newtonian sense) <img src="/images/icons/smile.gif" /> If the ship is travelling at .1c, the bomb it shoots ahead and the blast the bomb makes are also travelling at .1c- so in dynamics terms it's entirely identical to the ship being stationary and firing its first bomb, or travelling at .1c and exploding a bomb behind it. In all these cases, all that matters is the differential speed between the ship and the bomb, which will be the same for them all. If this weren't the case, relativity would fall apart since you could tell how fast in some absolute frame you are travelling by exploding a bomb outside your spaceship. Hmm, if you worked it out by measuring the energy release, would that be a bomb calorimeter? <img src="/images/icons/smile.gif" />

pyoko · Jun 7, 2007

I don't think such a mission would put much importance on decelerating the probe. Even if it were traveling at .1c relative to AC, much data can be gathered and sent back to Earth, reaching us a mere 4 years or so later. As for this Orion idea: it sounds expensive. Nuclear explosions and such. What I was originally proposing was a rather cheap probe. Yes, ion engines! Perhaps a push to get it going, but in the long run, I think ion engines are practical. Someone asked where the fuel would come from. Back in school, we had these thingies that have one open end and gamma radiation coming out of it due to the trace amount of radioactive material inside. I believe those little suckers are still spewing out stuff as we speak. 24 / 7 <div class="Discussion_UserSignature"> -pyoko the duck It is by will alone I set my mind in motion. </div>

centsworth_II · Jun 7, 2007

"As for this Orion idea: it sounds expensive." Expensive and very very politically incorrect! Imagine, nuclear bombs in space! Besides, I thought the purpose of this thread was to discuss the advantages/disadvantages of launching an interstellar probe soon, with current technology. <div class="Discussion_UserSignature"> </div>

silylene old · Jun 7, 2007

"As for this Orion idea: it sounds expensive." Expensive and very very politically incorrect! Imagine, nuclear bombs in space! Besides, I thought the purpose of this thread was to discuss the advantages/disadvantages of launching an interstellar probe soon, with current technology. That is why I said that the first probe will almost certainly be a tiny nano-robotic probe, of minimal mass. Low mass makes the proposition of sending a probe to another star (semi-quickly) technologically feasible today, and within budgets which are reasonable. If the nanoprobe is a flyby, it would need to have enough mass to power a laser to shine back to us with the data encoded on the light beam. I also assume we would want a lightweight optical aperture system, perhaps based on a thin curved reflective film. I think such a probe could be designed to be under perhaps 100g mass. A 10g mass would be even better - perhaps this tiny of a size is limited by the mass required to power of the laser beam. Such a tiny probe is almost within the technology improvements we can forecast to occur in the next one or two decades. In a previous post on this thread I discussed a nanoprobe + self automata factory which could decelerate, land and build an observation station on an airless moon. I forsee we may have this technological capability within 100 years. I really think all the discussion of sending huge massive probes, nuclear bombs, Orion's, multi-generational ships, FTL, etc is simply science fiction, and certainly will not occur within the next century (if ever). <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center">- - - - - - - - - - - - - - - - - - - - - - </div><div class="Discussion_UserSignature" align="center">I really, really, really miss the "first unread post" function. </div> </div>

chyten · Jun 7, 2007

Now to slow down, you would have to have the blast be at the front of the ship (in the opposite direction of travel). The first blast might slow the ship down from .1c to (say).095c, but the ship would then continue forward straight into the blast zone and be destroyed. That would be true if the blast zone itself were not moving. But any bomb launched from a ship moving at 0.1c is itself moving at 0.1c -- it is at rest (or very nearly so) with respect to the ship. All particles of the resulting explosion will retain this forward momentum; the blast zone will be at rest with respect to the ship. Hence if the ship could survive a nuclear blast while at rest (with respect to Sun), it will survive it while moving at 0.1c

Boris_Badenov · Jun 7, 2007

Rescoping the project into a probe is an interesting challenge. But one thats already been thought out. Project Daedalus <div class="Discussion_UserSignature"> <div align="center">. </div><div align="center">Never roll in the mud with a pig. You'll both get dirty & the pig likes it.</div> </div>

vandivx · Jun 8, 2007

good link, it gives one some idea of the speeds in form (km/h not sec) most people can 'understand' and comparison to Pioneers' speed which would get the probe there in some odd 123 000 years... midlife people might see the picture taken midway to star but only 20-30 year old at the time of the start of the mission may have some hopes to see the pictures taken on site braking is a problem because as they say fuel for braking would increase the initial payload too much and in additon for the probe to return back which would be in another at least 50 yrs you would also need the fuel to accelerate back to return speed and even if you could return as fast as you went out, all it would mean that your kids might get to see the probe back instead of your kids' kids now why would you go into trouble of braking and speeding up again if you already had the pictures safely transmited back although I am not sure how a transmission over such distance would work really, it is one thing to receive the starlight in telescope but possibly quite another if you wanted to receive broadcast from ~5lght yrs away and apparently those 135 mill km/h would end up in ~ 1mill km/h at the destiantion due to frictional braking from hitting the interstelar particles vanDivX <div class="Discussion_UserSignature"> </div>

dragon04 · Jun 8, 2007

I don't think such a mission would put much importance on decelerating the probe. I shouldn't think that an Interstellar Mission would be "fly by" in nature. Considering the resources, distances, and time involved, a probe that would just pass through a system wouldn't seem to be a worthwhile investment. As for this Orion idea: it sounds expensive. Nuclear explosions and such. Yes, expensive and not so politically correct. I was pointing out that it's the best (and actually possible from an engineering standpoint) current way to get to the Centauri System in reasonable amounts of time. <div class="Discussion_UserSignature"> "2012.. Year of the Dragon!! Get on the Dragon Wagon!". </div>

h2ouniverse · Jun 8, 2007

To me the quicker and most efficient way to send a probe to the nearest star is to develop new physics! <img src="/images/icons/smile.gif" />. Actually I am half-kidding. We know that notions of space and time are fuzzy. We should first clarify that and understand the loopholes in causality theories (a matter of few decades probably) before considering engulfing huge resources in a "classical" travel as primitive as relying on ejection of mass! Space travel today is like crossing a pond on a raft by taking 1 ton of stones on board, throwing them horizontally and counting on the reaction force. It works (painfully) on a pond. But don't think about crossing the Atlantic before at least discovering how to row!. So let's invest in fundamental physics and exotic ideas(even crackpots).

pyoko · Jun 8, 2007

The point in my original post was 'what if we never find a better way to do it?'. Meaning sending something NOW is the best decision. The 'what if' in my post was supposed to be the underlying factor. Although I do hope we discover the 'different physics' soon. Probably the best way to discover something new and fundamental is with accelerators. And they take over a decade to build, unfortunately. <div class="Discussion_UserSignature"> -pyoko the duck It is by will alone I set my mind in motion. </div>

kelvinzero · Jun 8, 2007

I think we are basically certain to develop much better ways to do it. Even if no physics breakthroughs are developed, with in a century I think we could quite possibly:<li> Get a space industry going, eg using luna resources to create something that is simply much bigger than our economy could currently handle<li> Harness massive amounts of sun power eg for beamed propulsion<li> Get better AI, so it can do something much more useful when it gets there<li> Master self reproducing factories, so that even a small payload could start developing something significant on the other end. (also repairing itself in flight)<li> .. which would almost certainly be able to upgrade itself to download plans for the very latest technology communicated from earth. If we sent a probe right now, not only would later probes arrive sooner, but very possibly our telescopes etc would have improved so magically that any information it returned was redundant.</li></li></li></li></li>

dragon04 · Jun 9, 2007

So let's invest in fundamental physics and exotic ideas(even crackpots). Seeing that the only workable system is politically and environmentally not an option (unless perhaps every major power did it as a joint venture with complete transparency), I'm inclined to agree with you. It takes 15 years to get to Pluto, let alone traveling to the Centauri system. Ion engines are problematic. For one, there is the issue of the propellant medium and the quantity needed versus the mass of the craft. Next, I think that time truly would be of the essence. While I have no way to give you probabilities, one thing that we know is the longer a craft is in space, the closer it becomes to some sort of critical failure that would end the mission. That's why I like the Orion. It's crude, but effective. In addition, it wouldn't be constrained to accelerating at a comfy 1g being unmanned. The nanoprobe idea is intriguing, but again, what velocity would we hope to accelerate it to, and how long a transit would or could we tolerate? What I'm getting to is that it seems an ill advised idea to commit the money and personnel to such missions when they might be obsolete before they even hit interstellar space. Again, I have to make a case for an Orion. With current technology, unless I'm wrong, power to transmit data back to Earth from 4 LY away would be prohibitive in nature in terms of mass. Until that hurdle can be jumped, a "there and back again" mission seems like the best way to get data back to Earth. Assuming .1c, that would be about a 45 year transit. Arbitrarily, let's say the mission collects data for 5 years and returns. You basically have a ton of data in a century or so. But even then, our crude, lumbering beast has to function with no major failure for at least long enough to get there, do its mission, and begin the return trip hoping <div class="Discussion_UserSignature"> "2012.. Year of the Dragon!! Get on the Dragon Wagon!". </div>

dragon04 · Jun 9, 2007

The point in my original post was 'what if we never find a better way to do it?'. Meaning sending something NOW is the best decision. The 'what if' in my post was supposed to be the underlying factor. I don't think we've spent nearly enough time in the spaceflight business to consider your "what if" scenario yet. I also think that in regards to exploration of interstellar space, we need to take space based interferometry to the edges of its abilities first. In light of the above, the 800 Pound Question hasn't been asked or addressed yet in this thread. WHY do we attempt a mission to Centauri? What data do we expect to find sending a mission out literally in the blind? Are there interesting planets there? We don't know. I mean yes, it would be really cool to do an interstellar mission, but how much money is "cool" worth considering that we have no clue if we'll even find anything we don't already know about our target System. If it's just to test technology, we can do THAT without leaving the Neighborhood, so to speak. This is a fun topic and gets the brain working, but we're really getting the cart ahead of the horse here, I think. <div class="Discussion_UserSignature"> "2012.. Year of the Dragon!! Get on the Dragon Wagon!". </div>

deapfreeze · Jun 9, 2007

"If it's just to test technology, we can do THAT without leaving the Neighborhood." I agree we can definately test our technology in our own neighborhood. The problem I have is that we don't test enough. There has to be a way that we could get more missions to space do more exploring in our solar system. The money has to be there somewhere. We need to work harder at finding the cash and working together. <div class="Discussion_UserSignature"> William ( deapfreeze ) Hooperhttp://deapfreeze-amateur-astronomy.tk/ </div>

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