Voyager 1 this close to leaving solar system | Hacker News Reader

Voyager 1 this close to leaving solar system

theatlantic.com

189 pointsharold80 comments

Is a project like Voyager worth repeating every so often? Speaking in financial terms relative to other space ventures, would it really be all that expensive to launch a deep space probe every few years and send it hurdling off toward some distant recess of space, outfitted with whatever state-of-the-art equipment we had available at the time? It just seems that we keep coming back to Voyager and we continue to be fascinated with the measurements it takes these many years later. Why are we not preparing even more capable craft for deep space exploration that future generations of humans could marvel at?

In order to launch something so far out you have to "slingshot" off the other planets. A launch window like that only comes once every so often.

"For example the Voyager missions which started in the late 1970s were made possible by the "Grand Tour" alignment of Jupiter, Saturn, Uranus and Neptune. A similar alignment will not occur again until the middle of the 22nd century."

source: http://en.wikipedia.org/wiki/Gravitational_slingshot#Limits_...

I was thinking the same thing as yock, but if I had the resources to fund such a project I'd want to give the probe a power source that would allow it to accelerate continuously. I think we've got both the electric generator and propulsion technologies to do that now, where weren't available in the 70's. That would let the probe reach Voyager's distance much more quickly, and we'd be flexible in choosing a launch date.

I'd also want to use some of that power to make the probe 'bright'. It could transit telemetry back to us with more power so we could keep contact with it longer, and it could also broadcast its presence in every other direction too. That way if there is anyone out there, they'll have a chance to find the probe. With the Voyager probes, even if the galaxy is teeming with intelligent space-traveling life it's unlikely that anyone will every find the tiny little things.

The Dawn spacecraft use ion drives. "With the propellant it carries, it can perform a velocity change of over 10 km/s, far more than any other spacecraft has done with onboard propellant after separation from the launch rocket." Voyager 2 got a 20km/s boost from Jupiter, and almost the same from Saturn, about 4km/s from Uranus, and about 10 from Neptune. (See http://www2.jpl.nasa.gov/basics/bsf4-1.php )

In other words, even the best rockets we have now are not as good as that rare lineup of all four gas giants in this system.

Also, we don't have a better energy source. Voyager used RTGs, and that's still what we have. In any case, power isn't the limiting factor, it's exhaust velocity and amount of fuel.

So you can get about 75% of Voyager 2's speed boost from a conjunction of just Jupiter and Saturn, which comes about a lot more often [1].

[1] http://en.wikipedia.org/wiki/Great_conjunction

Here's an interesting graph:

http://en.wikipedia.org/wiki/File:Voyager_2_velocity_vs_dist...

Looks like Uranus gave a tiny boost and Neptune a negative boost -- not through any intrinsic property of the planet, mind you, just the constraints applied when you want to tour the whole solar system without burning any fuel.

That's the same graph as the JPL link I pointed out earlier, but clearer and with more description.

It shows that my earlier reading was incorrect. It looks like the delta-V from Jupiter is 11km/s, Saturn is 8km/s, Uranus is 1km/s and Neptune, as you point out, is a negative delta V w.r.t distance from the Sun. Note that the comment says it's because Voyager 2 deflected out of the plane of the ecliptic as a consequence of doing a flyby of Triton, and not because of fuel constraints.

In any case, I had forgotten that Voyager I did not do the grand tour of the giants. I haven't been able to find a similar velocity profile for Voyager I.

I wonder if it be possible to utilize something like the http://en.wikipedia.org/wiki/Interplanetary_Transport_Networ... to get to the edge of the solar system with low energy requirements, and then burn the engines when you're out near Neptune?

The Jupiter Icy Moons Orbiter (Project Prometheus) had a design delta-V about 40 km/s (100 kW nuclear fission reactor + electric ion thrusters).

http://www.lpi.usra.edu/meetings/jimo2003/hartman.pdf

http://en.wikipedia.org/wiki/Jupiter_Icy_Moons_Orbiter

I suspect an ion drive system could do it. You still need to slingshot somewhat, and you would gain flexibility if you didn't try to fly by all the planets on the way out. New Horizons [1] looks to hit the Kuiper belt in 10 yrs so considerably faster than Voyager.

[1] http://pluto.jhuapl.edu/mission/mission_timeline.php

IIRC Deep Space 1 used an ion thruster and obtained comparable speeds to voyager.

Could you elaborate? Are you talking about velocity outwards from the sun or including the orbital term as well? Are you talking about the Voyager I speed now, or just after the Jupiter gravity assist?

From what I can find, the best ion craft we have now (Dawn) is about 1/2 as effective as a Jupiter flyby, and 1/6 as effective as the series of flybys that Voyager did.

Dawn isn't the best we can do, though, because it's solar powered. Even in the inner solar system, solar power can't give you nearly as much power as you can get from a decent radioisotope thermoelectric generator, and in the outer solar system you can fuhggedaboudit.

If we wanted to send a probe to the middle of nowhere right now and had a billion or two to do it we'd strap our best ion drive to our best RTGs and then send it via a Jupiter slingshot. No idea how fast we could get it. Of course it would continue to accelerate until the power or the propellant ran out.

The New Horizons RTG puts out 300W of electrical energy (and more as heat). The solar arrays on Dawn can supply "10 kW at Earth and 1.4 kW at Ceres". Wikipedia says the NSTAR thrusters on Dawn requires 2.3 kW.

How do RTGs help?

Let's say they somehow do (perhaps I have the numbers wrong). How much more delta V would you get using an RTG? Twice the delta V as solar panels? Note: momentum transfer goes as the square root of the energy, so you would need 4x as much power as Dawn uses. On the other hand, you wouldn't be carrying heavy panels.)

If so, 20km/s is about what a Jupiter or Saturn flyby gives. So RTG+ion thruster+Jupiter is about equivalent to the Jupiter+Saturn part of Voyager. Except Voyager also used the outer gas giants.

My point is that to get the same speed you'll need at least both of Jupiter and Saturn lined up right, and preferably at least one of Uranus or Neptune. Your proposal isn't enough.

I must admit that you've surprised me with the numbers on solar vs RTG. (I've learned something today!) But of course you can always strap multiple RTGs together. According to wikipedia's article on RTGs the most efficient ones produce about 4 watts per kilogram, so you'd need a couple of tons of 'em to equal Dawn's 10 kW at Earth, well in excess of Dawn's mass. Solar panels still rapidly become useless (like the square of the distance from the sun) as you get further out, of course.

Solar is way denser than an RTG in terms of power per kilogram, at least out to Jupiter and probably to Saturn as well.

This doesn't mean that RTGs don't have value. They are continuous and keep things warm, which may be very important depending on your mission.

Well, you don't have to go as fast as the Voyagers to end up out on the edges of the Solar System in a few decades. Even so, it's interesting that the New Horizons Pluto probe was launched with a higher speed relative to Earth than the Voyagers but will ultimately end up traveling slower because it won't slingshot by as many planets.

But Voyager 1 (the faster one) didn't even go the grand tour. It just flew by Jupiter and Saturn. That constellation should happen more often. And as you can see with the Pioneer missions even Jupiter alone can make you quite fast.

The closest thing is new horizons. However, due to some complications with the department of energy, there no longer exist RTGs (the nuclear-decay power source) of the kind that are used to power Voyager. New Horizons has an RTG, but it's much smaller capacity and will degrade much faster, so it's unlikely that NH will provide the same long term results as V1 & V2.

There is the New Horizons Pluto/Kuiper probe belt sent in 2006. The thing is fast, it passed Jupiter in 13 months and is currently beyond the orbit of Uranus.

New Horizons is traveling at about 15 km/s, 2 km/s slower than Voyager 1, and is still slowing down. When New Horizons reaches the same distance from the sun as Voyager 1 is now, its speed will be about 13 km/s (8 mi/s).[15] The close flyby of Saturn and Titan gave Voyager 1 a massive advantage with its extra gravity assist. http://en.wikipedia.org/wiki/Voyager_1

We're lucky that Voyager made it there in the first place. At one point Congress killed the Grand Tour idea in favor of a Jupiter-Saturn flyby. However management responded by adding piecemeal upgrades like a bigger power source and reprogrammable computer that would allow the Grand Tour idea to proceed. http://history.nasa.gov/SP-4219/Chapter11.html

Though perhaps if they had killed the Grand Tour then we might have sent an orbital probe to Uranus or Neptune by now, and we might know a lot more about them. We have literally hours of direct observation on both these planets put together -- there's some really interesting data and it would be fantastic to get back there and do some better observations, because at present we know sod-all about them.

Unfortunately, a probe to Uranus is still a fairly low priority for NASA. I think the worry is that we'd be spending a billion dollars on funding obvious toilet humor.

The deep-space info is cool, but honestly we get a lot more scientific knowledge from leaving a craft in orbit around a planet (e.g. Cassini). If we hadn't had the lucky four-planet-flyby option with Voyager (something that won't happen again for another x00 years) we'd probably have kept it orbiting a single planet until it broke down - and got more data as a result.

I read some speculation maybe a year ago saying a possible reason space outside of our solar system seems to quiet to us is that the heliosphere is blocking almost all radio frequencies from reaching us (or getting out). The author of the piece then questioned if we would hear from Voyager once it's outside. Outside of the heliosphere may be teeming with transmissions, may be noisier than Times Square on New Year's Eve. Voyager might pick that up, but we'd never hear about it.

In this article I see some very slight hinting towards that possibility. Does anyone know what I'm referring to? Anyone have any more input on that?

I don't think there's any evidence of that and we have plenty of radio telescopes listening to deep space.

But there are significant problems picking up 'intelligent' signals like the ones being transmitted by Voyager because of the 'free space attenuation' of the radio signal caused by the spreading of the radio signal: http://en.wikipedia.org/wiki/Free-space_path_loss

The attenuation of radio signals in this way is one of the reasons why it will be difficult for any other civilisations to pick up our radio signals. There were some calculations done by the SETI folks on how far out our common Earth radio signals would be detectable (such as FM radio or broadcast TV) using a very large radio telescope and the answer was that they wouldn't make it our of the solar system.

Earth-based radio telescopes would receive nothing from outside our solar system if that was true.

Unless you mean to imply the heliosphere might be blocking low powered radio signals from other spacecraft?

Well the speculation I mentioned did say something to the effect of "almost all". The possibility it sparked in my mind was that outer space is very very noisy and we only receive a very small sample of radio frequencies which happen to penetrate the barrier.

I'm not a radioastronomer, but I'm fairly sure that if I went next door and talked to one they'd laugh their heads off at the suggestion.

Put your wireless router on top of a microwave then start a Skype call. Before your Hot Pocket turns molten, let me know how good of a connection you have.

It's not a far stretch of the imagination to say radio waves can suffer from interference and even reflection off magnetic fields. It happens here on Earth; bouncing shortwave off the ionosphere is a very common way to communicate long distances.

https://en.wikipedia.org/wiki/Skywave

How is ionospheric reflection related to your claim?

Signals bouncing off a strongly magnetic bubble.

The microwave was a separate but related example of electromagnetic interference on radio transmissions. Both combined paint a picture showing it's possible we might not hear from Voyager again and might not get a good picture of intelligent transmissions outside the heliosphere.

Do they have any better explanations for the Fermi paradox then?

http://en.wikipedia.org/wiki/Fermi_paradox

No, but they know how to estimate the effect of an inhomogeneity in the interstellar medium on radio wave propagation.

The space outside is not quiet. We can pick up all sorts of frequencies from outer space, and the spectra seems to have no gaps.

It just that we can't seem to find any intelligent message buried in heaps of information that's falling on Earth.

If that were true, shouldn't the space beyond the heliosphere be dead quiet then, assuming all the other solar systems had the same effect applied to them? No noise in, no noise out.

If I live in a soundproof house, no noise in no noise out. But when I walk out onto the highway, there's a lot of noise. The speculation was that outer space is a transportation network and high-speed communications hub, but we're being left out by not knowing how to access the stream of noise. I'd really love to find that article again.

The other replies to this comment seem to imply that this is unlikely, but I must say that [while not good for science], it'd be kinda cool in a spooky way for Voyager to just suddenly disappear to us as it passed the boundary.

And then it gets returned to us as lost property a few weeks later, Star Trek style.

With a ticket for littering.

For those who didn't know how Voyager can still be working, it is running on a Radioisotope Thermoelectric Generator (a nuclear device). Solar panels would be useless at its current distance from the sun.

Is there any data on how long that should run for?

They can power down specific instruments to stay within the decaying threshold. Wikipedia has this timeline of instrument power-downs: http://en.wikipedia.org/wiki/Voyager_1#Interstellar_mission

Half-life of plutonium-238 is 87.7 years so there should be approximately half of the original power left after that time. Nowadays the power of the device is about 75 % of original.

You'd think so, in practice it doesn't work that way. A significant factor is degredation of the thermocouples due to heat and radiation. This causes the power output to drop faster than would be expected due to pu-238 decay alone. Right now current power levels are around 63% compared to launch, which would be the expected power level in the 2030s if radioactive decay were the only factor.

Interestingly enough, this did not get caught by reddit's theatlantic.com filter.

http://www.reddit.com/r/junk001/comments/v122m/test1/?alread...

http://www.dailydot.com/news/reddit-ban-the-atlantic-phsyorg...

It's going to be some time before I stop thinking 'spam' every time I see a URL to theatlantic.

I still get goosebumps when I listen to some of the greetings on the "golden record" and imagine someone out there listening to it one day: http://voyager.jpl.nasa.gov/spacecraft/greetings.html

""Friends of space, how are you all? Have you eaten yet? Come visit us if you have time." That is NOT the sort of message I'd send to ETs. What if they mistake humans for food? ;-)

That was my exact reaction when I read that greeting. It almost seems like an invitation for them to consume as a regular dinner.

On Dec 21, 2012, Voyager I will officially leave the solar system and the heliosphere. It will instantly smack into a holographic sheet wrapped around us by the aliens who visited the Mayans. This sheet is the false projection of the rest of the universe. They show everything as distant and empty so we won't investigate. But Voyager I defeats their ruse. And so, the aliens decide we know too much and wipe us out before creating a new solar system rat maze for the next species in line.

Kind of like The Truman Show? https://en.wikipedia.org/wiki/The_Truman_Show#Plot

(oh and Solar System != Universe :-) )

This is really cool, in that I remember being a kid and telling the other kids in school about the Saturn flyby.

It is really cool, sadly I remember as a kid remember NASA saying that it could leave the solar system as early as 2010 and thinking "Wow, I'll be really old then." :-)

I didn't imagine the heliopause having such a (almost theatrical) hard edge. Isn't even a month rather rapid at the scale of distances involved?

At what point would equipment failure be considered, especially given the notable lack of experience in this scenario? Seems that corroborating evidence would be highly desirable before publicizing this. (Or perhaps I am underestimating the data already gathered on this topic...)

1 month = ~44million km which is not exactly a hard edge even by these standards. (17km/s * 60 * 60 * 24 * 30)

I think that these craft are one of mans greatest achievements, so I don't mind hearing this over and over again :). The thought that no matter what, these craft will outlive the human race and continue hurtling through deep space for eons, is one that really blows me away.

So what happens when it leaves the solar system? My knowledge of interplanetary communications is quite limited but will there ever be a time when the Voyager can no longer communicate with Earth because it is out of range? 16 hours to receive a message is quite a long time, will that keep growing until eventually it will take years to receive a message or we won't receive messages at all?

The repressed space geek within me is jumping to all kinds of conclusions as to what will happen when it leaves the solar system, what it will find and what it may accidentally discover.

Any idea how the Voyager managed to escape the asteroid belt without being hit by a 'space stone'. Are we actually manually controlling it ?

The "asteroid belt" is unimaginably sparsely populated. Nothing like you see in Star Wars with spaceships dodging and weaving around dense fields of rocks. Asteroids are separated by a million kilometers. The chance of hitting anything at all on a random trajectory is extremely low, on the order of one in a million.

http://physics.stackexchange.com/questions/26712/what-is-the...

http://wiki.answers.com/Q/What_is_the_average_distance_betwe...

Star Wars the Empire Strikes Back did some horrible things to a lot of people's conceptions about asteroid belts.

The asteroid belt is so unbelievably sparse, you would never even know you are flying through it. Absolutely no concern was given to the prospect of a collision.

To give you some perspective, as a test they flew one of the pioneer spacecraft through the rings of saturn, even the rings of saturn are so sparse that the spacecraft flew through completely untouched.

While I get your point, this surely isn't true though, right?

   Absolutely no concern was given to the prospect of a collision.

Doesn't NASA have to constantly deal with and prepare for one-in-a-million chance scenarios? It seems reasonable to have a collision detector and "auto-route-arounder" that help here (among many other scenarios).

It might be more accurate to say that thought has been given to the prospect of a "generic" collision with a space object, but that no thought was spared for asteroids in the asteroid belt in particular. Twice nearly nothing per cubic megameter is still nearly nothing.

I think Voyager I is leaving our solar system on an angle that takes it away from the (relatively) flat plane of planetary and asteroid orbits.

http://physics.uoregon.edu/~jimbrau/BrauImNew/Chap06/7th/AT_...

They're really not that close together. If you were flying through space, you'd have a fairly difficult time determining that you were in an asteroid field when you reached one. Albeit some asteroids do travel in 'families.'

Dr. Marc D. Rayman on the Dawn Project: Dawn will travel 7.7 astronomical units (AU), or nearly 1.2 billion kilometers (almost 720 million miles), to its July 2011 rendezvous with Vesta. Yet in all that time, and across all that distance, the closest the probe will come to a catalogued asteroid is 1.0 million kilometers (greater than 600 thousand miles), or more than 2.5 times the distance between Earth and the moon.

It had a gyroscope that would rotate it to measure magnetic effects in a 360 range, but I believe it was disabled years ago. As far as I know, it's not being controlled. If it was ever manually controlled, the fuel would likely have run out decades ago. Either it got lucky or the engineers ran the calculations to find a clear path.

You mean "Veeger", right?

I got a pretty good chuckle out of this.

Reference to Star Trek: The Motion Picture, for anyone who may not immediately get the reference. The plot of the story revolves a giant space cloud containing a vessel that's ultimately returning Voyager to Earth.

It was a very appropriately timed movie and really explores the idea of Man's impact even beyond our solar system with the devices we shoot off into the stars.

"Veeger," from the original Star Trek movie, is what made me get up and go learn about Voyager.

It's too bad that the Voyager doesn't have a 24/7 streaming on the web webcam.

Does anyone know why they decided to turn off the cameras?

I've been reading these articles for at least ten years now as Voyager has crossed various different "edge of the solar system" boundaries.

There's still a fair few people working on Voyager, and they don't have much to do now except stare at slightly different types of vacuum, so they feel the need to issue a press release every couple of years.

This actually has scientific significance though. There is no reason to start throwing jabs at scientists related to this research because you're not interested.

I'm not really throwing jabs, I'm being mildly facetious. Still, the "we're nearly at the edge of the solar system" stories have been coming for a long time. From 2000:

http://www.sciencedaily.com/releases/2000/12/001219073936.ht...

The Voyager 1 spacecraft, the farthest human-made object from Earth, may reach the beginning of his boundary region between early next year and the end of 2003

Now, that was the termination shock, this is the heliopause. Next comes the bow shock.

If a discovery last month by IBEX (an earth-orbit satellite with sensors aimed at mapping the interstellar boundary) holds up, it seems that the sun doesn't have a bow shock after all: http://www.nasa.gov/mission_pages/ibex/news/nobowshock.html

Apparently not?

http://en.wikipedia.org/wiki/Bow_shock#Bow_shock_theory_for_...

grumble grumble grumble

Has any specific effort been given to archiving the knowledge and history of the human race, off planet, and at a considerable distance from Earth?

There's actually information aboard the Voyager: http://voyager.jpl.nasa.gov/spacecraft/goldenrec.html

Also, there's a more ambitious project that keeps getting delayed: http://en.wikipedia.org/wiki/KEO

Voyager's data store is what prompted my question: what if all that's eventually left of the human race's history and knowledge is the incredibly tiny Voyager record. Which then got me thinking about a more 'long term' data store for a radically larger amount of data. As long term as we can make it, and as safely far away from Earth as we can place it while still being able to somewhat calculate its safety (understanding the one in a million type risks inherent to anything traveling in space). The point would be to leave behind a record (that can be found), for a what-if scenario.

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