Page 1 of 1

What-If 0038: "Voyager"

Posted: Tue Mar 26, 2013 2:06 pm UTC
by mojacardave
http://what-if.xkcd.com/38/

I'm assuming the delay in the creation of this thread is due to distractions caused by "Time"!

Re: What-If 0038: "Voyager"

Posted: Tue Mar 26, 2013 2:11 pm UTC
by Palpatineli
I suppose an unmanned Orion could bring Voyager back with relative ease?

Re: What-If 0038: "Voyager"

Posted: Tue Mar 26, 2013 2:13 pm UTC
by mojacardave
Voyager doesn't seem to want to return. Maybe we should go and rescue the poor lonely Curiosity rover instead. Lower fuel requirements.

Re: What-If 0038: "Voyager"

Posted: Tue Mar 26, 2013 2:15 pm UTC
by bulltza
There is something I slyghtly disagree in this What if. You can not use Ion engines to come back from where the Voyager is right now. The reason is that to power an Ion engine you need to produce electricity in the order of several kW, and that is only possible with Solar panels at this moment. So when you are further than Jupiter your solar panels are no longer useful and you can not use the ion engines. The RTGs generate less than 200W. This is one of the reasons it is impossible to build at this stage a spacecraft ion powered to navigate in Saturn.

So we need a spacecraft with several RTGs, ok... maybe then it would be possible? using all the RTGs ever made for space exploration? :)

Re: What-If 0038: "Voyager"

Posted: Tue Mar 26, 2013 2:29 pm UTC
by latigid on
I have found an un-word in the title text of the first image, should be "Earth is faster than Voyager..."

Re: What-If 0038: "Voyager"

Posted: Tue Mar 26, 2013 2:45 pm UTC
by Klear
I hope that in a couple of centuries we will have technology that will allow us to grab Voyager in much shorter time.

Re: What-If 0038: "Voyager"

Posted: Tue Mar 26, 2013 2:58 pm UTC
by rmsgrey
Palpatineli wrote:I suppose an unmanned Orion could bring Voyager back with relative ease?

Depends on the supply of nukes, though the minimum size requirements for an Orion mean you might as well go for it and send out a manned one...

Re: What-If 0038: "Voyager"

Posted: Tue Mar 26, 2013 3:17 pm UTC
by Vroomfundel
rmsgrey wrote:
Palpatineli wrote:I suppose an unmanned Orion could bring Voyager back with relative ease?

Depends on the supply of nukes, though the minimum size requirements for an Orion mean you might as well go for it and send out a manned one...


Generally, it's not going to be much more efficient, especially considering the public outrage it's going to cause (thause progressophobics protest against even petty things like nuclear power plants) - the Orion craft has to be quite big to make it viable, so you need to launch loads of steel (or titanium, or whatever) just to get there.

Re: What-If 0038: "Voyager"

Posted: Tue Mar 26, 2013 3:26 pm UTC
by rmsgrey
Vroomfundel wrote:
rmsgrey wrote:
Palpatineli wrote:I suppose an unmanned Orion could bring Voyager back with relative ease?

Depends on the supply of nukes, though the minimum size requirements for an Orion mean you might as well go for it and send out a manned one...


Generally, it's not going to be much more efficient, especially considering the public outrage it's going to cause (thause progressophobics protest against even petty things like nuclear power plants) - the Orion craft has to be quite big to make it viable, so you need to launch loads of steel (or titanium, or whatever) just to get there.


Or establish low-G mining facilities

Re: What-If 0038: "Voyager"

Posted: Tue Mar 26, 2013 3:36 pm UTC
by FrobozzWizard
I'm surprised no one has mentioned the fundamental waste of the exercise: If it's going to take over 2 centuries for Voyager I to return once we launch the mission, why not just wait until 2270 when V'Ger returns entirely on its own accord?

Re: What-If 0038: "Voyager"

Posted: Tue Mar 26, 2013 4:12 pm UTC
by Biliboy
So though I'm generally easily amused, my "laugh out loud" threshold is fairly high... That being said I lost it at the NASA boat.

Re: What-If 0038: "Voyager"

Posted: Tue Mar 26, 2013 4:41 pm UTC
by Jamaican Castle
We'd have to be pretty foolish to go to all that effort and not remember to put reentry equipment on the recovery vehicle... I suppose it would be a lot easier to have a second recovery vehicle that links up with the original probe and the first RV at, say, a year before Earth impact that's carrying all the heavy stuff, no sense carting it all the way out there.

Or we could just wait until they discover FTL travel. That sounds a lot simpler, even if it isn't actually possible.

Re: What-If 0038: "Voyager"

Posted: Tue Mar 26, 2013 4:49 pm UTC
by rhomboidal
FrobozzWizard wrote:I'm surprised no one has mentioned the fundamental waste of the exercise: If it's going to take over 2 centuries for Voyager I to return once we launch the mission, why not just wait until 2270 when V'Ger returns entirely on its own accord?

Yes, we'd really need to be careful, because if we retrieved Voyager 6 before it attained omniscience-seeking sentience, there'd be no Star Trek movie franchise.

Re: What-If 0038: "Voyager"

Posted: Tue Mar 26, 2013 5:45 pm UTC
by MonkeyPuzzle
We choose to go get the sunken Voyager. We choose to go get the sunken Voyager in this decade and do the other things, not because they are hard, but because they are easy?

Re: What-If 0038: "Voyager"

Posted: Tue Mar 26, 2013 6:15 pm UTC
by wumpus
bulltza wrote:[deletia]
So we need a spacecraft with several RTGs, ok... maybe then it would be possible? using all the RTGs ever made for space exploration? :)


This leads to the question of why in the world would you cut the engines and return via gravity? It might have something to do with your RTGs no longer capable of powering your ion thrusters (Pu238 seems to be what NASA likes, and has a half life of 87 years), but I would have to assume that you would design the whole thing so that it can get home reasonably fast. You could even (with significant planning) use slingshot techniques to slow down your spacecraft once it came home to get it to stay in Earth orbit.

Also, nobody mentioned Harry Potter and the Methods of Rationality? The associated website must be in even lower repute around here than the last time I saw them mentioned on this board.

Re: What-If 0038: "Voyager"

Posted: Tue Mar 26, 2013 7:40 pm UTC
by Kit.
bulltza wrote:There is something I slyghtly disagree in this What if. You can not use Ion engines to come back from where the Voyager is right now. The reason is that to power an Ion engine you need to produce electricity in the order of several kW, and that is only possible with Solar panels at this moment. So when you are further than Jupiter your solar panels are no longer useful and you can not use the ion engines. The RTGs generate less than 200W.

There are bigger RTGs than that.

However, I wondered how they would cool that RTG in vacuum.

Then I wondered if it could be possible to feed the mission's solar panels using black body radiation provided by the RTG.

Re: What-If 0038: "Voyager"

Posted: Tue Mar 26, 2013 8:11 pm UTC
by Srt252
bulltza wrote:There is something I slyghtly disagree in this What if. You can not use Ion engines to come back from where the Voyager is right now. The reason is that to power an Ion engine you need to produce electricity in the order of several kW, and that is only possible with Solar panels at this moment. So when you are further than Jupiter your solar panels are no longer useful and you can not use the ion engines. The RTGs generate less than 200W. This is one of the reasons it is impossible to build at this stage a spacecraft ion powered to navigate in Saturn.

So we need a spacecraft with several RTGs, ok... maybe then it would be possible? using all the RTGs ever made for space exploration? :)


True for current RTGs but actually there have been full nuclear reactors flown in space that could generate the power necessary for ion thrusters. Even the 200kw VASIMR

Re: What-If 0038: "Voyager"

Posted: Tue Mar 26, 2013 8:46 pm UTC
by KroniK907
FrobozzWizard wrote:I'm surprised no one has mentioned the fundamental waste of the exercise: If it's going to take over 2 centuries for Voyager I to return once we launch the mission, why not just wait until 2270 when V'Ger returns entirely on its own accord?


obviously you haven't been around here long....

Image

Re: What-If 0038: "Voyager"

Posted: Tue Mar 26, 2013 9:50 pm UTC
by Palpatineli
rmsgrey wrote:
Palpatineli wrote:I suppose an unmanned Orion could bring Voyager back with relative ease?

Depends on the supply of nukes, though the minimum size requirements for an Orion mean you might as well go for it and send out a manned one...

The point of unmanned Orion is that you can have acc flutuations up to 10G. That mean no buffering mechanism behind the plate and much less dead weight. The unmanned variety can be made as small as 3 tons. You can find it in George's book, as a backup plan for asteroid impact.

Re: What-If 0038: "Voyager"

Posted: Wed Mar 27, 2013 12:30 am UTC
by Reka
mojacardave wrote:Voyager doesn't seem to want to return. Maybe we should go and rescue the poor lonely Curiosity rover instead.

Assuming you meant Spirit, not Curiosity (which AFAIK is "alive" and well): Hear, hear!

(I have the t-shirt of Spirit saying "help!". It's my oblique-xkcd shirt: it's not actually #695, but it's what every xkcd-geek thinks of straight away when they see it.)

Re: What-If 0038: "Voyager"

Posted: Wed Mar 27, 2013 4:52 am UTC
by ijuin
Jamaican Castle wrote:We'd have to be pretty foolish to go to all that effort and not remember to put reentry equipment on the recovery vehicle... I suppose it would be a lot easier to have a second recovery vehicle that links up with the original probe and the first RV at, say, a year before Earth impact that's carrying all the heavy stuff, no sense carting it all the way out there.


The problem is that, in order for the reentry vehicle not to slam into the returning Voyager at several dozen times the speed of a bullet, they need to match velocities, which unsurprisingly takes as much fuel as simply hauling the reentry vehicle all the way there and back, unless Jupiter happens to be in exactly the right place in its orbit at exactly the right time to use a slingshot maneuver to help with the rendevous.


wumpus wrote:This leads to the question of why in the world would you cut the engines and return via gravity? It might have something to do with your RTGs no longer capable of powering your ion thrusters (Pu238 seems to be what NASA likes, and has a half life of 87 years), but I would have to assume that you would design the whole thing so that it can get home reasonably fast. You could even (with significant planning) use slingshot techniques to slow down your spacecraft once it came home to get it to stay in Earth orbit.


Using your engines to return to Earth would require that you carry even more propellant, which brings us back to the tyranny of the rocket equation.

Re: What-If 0038: "Voyager"

Posted: Wed Mar 27, 2013 8:43 am UTC
by zyzyzyryxy
Hey, I think that we don't have to bow to the "rocket tyranny" so much. Nobody said that the rescue ship also has to return to earth, right?

That idea is based on laser propulsion for rockets described here

Lets send a ship with a mirror that will attach to the Voyager. It don't have to carry any fuel except that used to reach Voyager and match its speed and position.
Then send another ship with some kind of reactor and a powerful laser, that will reach Voyager and get in front of it (it doesn't even have to match Voyager's speed, although that might help by increasing effectiveness of the solution) and fire its laser to slow it down.

It might be even more effective if we launch a series of laser guns - each next laser may take longer to reach Voyager and will be pursuing already-slowed-down target, so less energy will be needed to launch it. Additionally each next laser will fire from small distance, thus increasing overall effectiveness.

Re: What-If 0038: "Voyager"

Posted: Wed Mar 27, 2013 11:30 am UTC
by CharlieP
Small nitpick: it's the Royal Australian Navy, not the "Australian Royal Navy". :)

Re: What-If 0038: "Voyager"

Posted: Wed Mar 27, 2013 3:16 pm UTC
by Evadman
This does not answer the question I was trying to find out earlier in the week. What will be Voyager's path through the galaxy? What star will it first approach, what will be the velocity of that star compared to voyager, etc. I spent all day on monday trying to find information like this out, and it is apparently well hidden. Therefore, I am a sad panda.

Re: What-If 0038: "Voyager"

Posted: Wed Mar 27, 2013 5:22 pm UTC
by thevicente
Once Voyager had lost nearly all its speed, the Sun’s gravity would take over, and the probe would begin a long slow slide toward the inner Solar System. This would take about 200 years


200-year freefall. I'm not afraid of heights, but I'm feeling sick.

Or it is something I ate. But could be the thought.

Re: What-If 0038: "Voyager"

Posted: Wed Mar 27, 2013 6:50 pm UTC
by wumpus
ijuin wrote:Using your engines to return to Earth would require that you carry even more propellant, which brings us back to the tyranny of the rocket equation.


While ion engines powered by RTGs (or other forms of nuclear power) have to carry a certain amount of propellant, they don't really have to accept the full-blown tyranny of the rocket equation. [url="http://forums.xkcd.com/viewtopic.php?t=99739"]See here[/url]. I have no idea if you can survive the course needed swing back and forth between the inner planets and the Sun while furiously firing your ion power all the time (while using solar power after your Pu238 grew to weak to run the engine), but it would be an option (multiple reverse slingshot moves and atmospheric breaking while in flyby mode still available to the brave).

Re: What-If 0038: "Voyager"

Posted: Wed Mar 27, 2013 7:54 pm UTC
by Koyaanisqatsi
Evadman wrote:This does not answer the question I was trying to find out earlier in the week. What will be Voyager's path through the galaxy? What star will it first approach, what will be the velocity of that star compared to voyager, etc. I spent all day on monday trying to find information like this out, and it is apparently well hidden. Therefore, I am a sad panda.

Unless they pointed it to something (I don't know) then it is overwhelmingly likely that it will never reach another star system, and then exit the galaxy and never enter another galaxy. At least, that's what I heard.

Re: What-If 0038: "Voyager"

Posted: Wed Mar 27, 2013 8:10 pm UTC
by Srt252
Koyaanisqatsi wrote:
Evadman wrote:This does not answer the question I was trying to find out earlier in the week. What will be Voyager's path through the galaxy? What star will it first approach, what will be the velocity of that star compared to voyager, etc. I spent all day on monday trying to find information like this out, and it is apparently well hidden. Therefore, I am a sad panda.

Unless they pointed it to something (I don't know) then it is overwhelmingly likely that it will never reach another star system, and then exit the galaxy and never enter another galaxy. At least, that's what I heard.


"In about 40,000 years, Voyager 1 will drift within 1.6 light years (9.3 trillion miles) of AC+79 3888" and
"Voyager 2 will pass 4.3 light years (25 trillion miles) from Sirius" in 296,000 years. According to JPL.

Re: What-If 0038: "Voyager"

Posted: Wed Mar 27, 2013 9:08 pm UTC
by mfb
Koyaanisqatsi wrote:Unless they pointed it to something (I don't know) then it is overwhelmingly likely that it will never reach another star system, and then exit the galaxy and never enter another galaxy. At least, that's what I heard.

It is way too slow to escape from our galaxy, unless it gets a really close fly-by at a star at some point in the distant future.

Ion drives with a nuclear reactor (not those tiny RTGs) look promising. With an exhaust velocity of ~50km, and a delta_v requirement of ~20km/s to reach Voyager (starting from a low earth orbit), ~20km/s to catch Voyager and slow it down and additional ~5km/s to give it some velocity backwards, a total mass of ~20 tons might be possible, and that can be launched with a single Ariane 5:
~2 tons reactor for more than 400kW
~3 tons ion drives, radiators and other stuff
~15 tons reaction mass
Using the values for HiPEP with the worst case, we can power 8 of them for a total thrust of ~4N. Accelerating 20 tons by 20km/s requires 3 years. So what? We can even go with lower power, reaching Voyager needs decades anyway.

Re: What-If 0038: "Voyager"

Posted: Thu Mar 28, 2013 12:49 am UTC
by Mikeski
Srt252 wrote:"In about 40,000 years, Voyager 1 will drift within 1.6 light years (9.3 trillion miles) of AC+79 3888"

That's actually pretty hilarious. What are our chances of spotting something Voyager-sized at 1.6 light years? Voyager itself won't be making any noise (radio signals, etc) by then.

We sent a phonograph record to aliens who, to find it, would need technology that would make ours look like cavemen discovering fire.

Rather ballsy species we are, eh?

Re: What-If 0038: "Voyager"

Posted: Thu Mar 28, 2013 11:10 am UTC
by bassguy
MonkeyPuzzle wrote:We choose to go get the sunken Voyager. We choose to go get the sunken Voyager in this decade and do the other things, not because they are hard, but because they are easy?


Don't know what this says about me, but I read that from the first words hearing JFK's voice. That speech always makes me feel good about things (the world, government, possibilities) for a few moments...

Re: What-If 0038: "Voyager"

Posted: Thu Mar 28, 2013 11:51 am UTC
by mojacardave
Reka wrote:
mojacardave wrote:Voyager doesn't seem to want to return. Maybe we should go and rescue the poor lonely Curiosity rover instead.

Assuming you meant Spirit, not Curiosity (which AFAIK is "alive" and well): Hear, hear!

(I have the t-shirt of Spirit saying "help!". It's my oblique-xkcd shirt: it's not actually #695, but it's what every xkcd-geek thinks of straight away when they see it.)


Stupid mistake is stupid.

But yes, I meant Spirit. Though I assume Curiosity will be in the same position in a few years...

Re: What-If 0038: "Voyager"

Posted: Thu Mar 28, 2013 3:08 pm UTC
by groszdani
How do we locate the Voyager?

By that time the Voyager won't be able to power any instruments. We know its current trajectory but it may be subject to small perturbations by the gravity of all kinds of solar system bodies, including yet unknown ones. As errors add up, we may have to locate it in an area of space millions of kilometers wide. It is probably possible but requires additional equipment to carry.

Re: What-If 0038: "Voyager"

Posted: Thu Mar 28, 2013 7:05 pm UTC
by speising
groszdani wrote:How do we locate the Voyager?

By that time the Voyager won't be able to power any instruments. We know its current trajectory but it may be subject to small perturbations by the gravity of all kinds of solar system bodies, including yet unknown ones. As errors add up, we may have to locate it in an area of space millions of kilometers wide. It is probably possible but requires additional equipment to carry.


with that RTG it should be pretty hot...

Re: What-If 0038: "Voyager"

Posted: Fri Mar 29, 2013 3:06 am UTC
by ijuin
True, even with the RTG's heat output fading as the isotope decays, it should still be significantly hotter (and brighter in infrared) than ordinary debris. While ordinary material in equilibrium with its surroundings would be at 20-30K, the decay-induced heat should keep Voyager noticeably hotter than that for a couple of centuries to come.

Re: What-If 0038: "Voyager"

Posted: Fri Apr 05, 2013 8:40 am UTC
by azule
There was missing, the greatness present in early to mid what-ifs, the Mythbusters "let's make it happen and let's make it extreme" attitude (but for the theoritical IO inquisitiveness). The question of "what will it take to make a quicker return?" wasn't really explored. Answering only with the actual modern day capabilities of rocket science was a bit disappointing.

BTW, what's an RTG?

Jamaican Castle wrote:We'd have to be pretty foolish to go to all that effort and not remember to put reentry equipment on the recovery vehicle... I suppose it would be a lot easier to have a second recovery vehicle that links up with the original probe and the first RV at, say, a year before Earth impact that's carrying all the heavy stuff, no sense carting it all the way out there.

That's a very good idea.

Re: What-If 0038: "Voyager"

Posted: Fri Apr 05, 2013 11:42 am UTC
by Srt252
Radioisotope Thermoelectric Generator. Generates electricity from the heat given off by radioactive decay of isotopes (typically plutonium 238). Useful for "relatively" long spacecraft missions to deep space where solar arrays are not efficient.

And definitely agree, the last few what-ifs haven't really taken the all-out crazy in-depth approaches from the earlier ones.

Re: What-If 0038: "Voyager"

Posted: Fri Apr 05, 2013 7:37 pm UTC
by azule
Thank you, Srt252.

Re: What-If 0038: "Voyager"

Posted: Sun Apr 07, 2013 5:05 am UTC
by PM 2Ring
bassguy wrote:
MonkeyPuzzle wrote:We choose to go get the sunken Voyager. We choose to go get the sunken Voyager in this decade and do the other things, not because they are hard, but because they are easy?


Don't know what this says about me, but I read that from the first words hearing JFK's voice. That speech always makes me feel good about things (the world, government, possibilities) for a few moments...


http://images.cheezburger.com/completestore/2010/7/19/8e3cb909-59b2-42c6-a3db-5f0306d32337.jpg

Re: What-If 0038: "Voyager"

Posted: Mon Apr 08, 2013 1:37 am UTC
by addams
http://voyager.jpl.nasa.gov/index.html

Voyager.
We have wonderful imaginations.

Spoiler:
It is better to send a probe into interstellar space.
Far better.

Some of the people that worked on Voyager were so very charming.
Their charm is Voyager's charm.

If people are, still, here in one hundred years;
Will they know what JPL did?

We did one good thing. It was a weird thing to do, but we did it.
Voyager is like a bottle in the Ocean. More so.