35 Years Later, Voyager 1 Is Heading For the Stars 226
DevotedSkeptic writes with news that today is the 35th anniversary of Voyager 1's launch. (Voyager 2 reached the same anniversary on August 20.) Voyager 1 is roughly 18 billion kilometers from the sun, slowly but steadily pushing through the heliosheath and toward interstellar space. From the article:
"Perhaps no one on Earth will relish the moment more than 76-year-old Ed Stone, who has toiled on the project from the start. 'We're anxious to get outside and find what's out there,' he said. When NASA's Voyager 1 and Voyager 2 first rocketed out of Earth's grip in 1977, no one knew how long they would live. Now, they are the longest-operating spacecraft in history and the most distant, at billions of miles from Earth but in different directions. ... Voyager 1 is in uncharted celestial territory. One thing is clear: The boundary that separates the solar system and interstellar space is near, but it could take days, months or years to cross that milestone. ... These days, a handful of engineers diligently listen for the Voyagers from a satellite campus not far from the NASA Jet Propulsion Laboratory, which built the spacecraft. The control room, with its cubicles and carpeting, could be mistaken for an insurance office if not for a blue sign overhead that reads 'Mission Controller' and a warning on a computer: 'Voyager mission critical hardware. Please do not touch!' There are no full-time scientists left on the mission, but 20 part-timers analyze the data streamed back. Since the spacecraft are so far out, it takes 17 hours for a radio signal from Voyager 1 to travel to Earth. For Voyager 2, it takes about 13 hours."
Has it made it ? (Score:5, Informative)
If you look at this picture [nasa.gov], it sure does look like Voyager 1 may have left the solar system (in a plasma sense) in late August. (In other words, it is no longer seeing protons from the solar wind, which means it may be outside of the Sun's bubble of plasma, and into the interstellar medium.
If so, it has impeccable timing.
Re:Always the frontrunner? (Score:4, Informative)
It would be nice to think that one day we'll reach a technological level that allows us to overtake Voyager 1. I'm not that hopeful though. I think that the head start Voyager 1 has means that it always will be more remote from Earth than anything else constructed here. Excluding Pioneer 10, that is.
Voyager 1 is currently the most distant man-made object [nasa.gov], and is more distant than Pioneer 10.
Some kind of dupe (Score:5, Informative)
Voyager seems to be "heading for the stars" once every six months:
- http://science.slashdot.org/story/12/06/15/0115226/new-signs-voyager-is-nearing-interstellar-space
- http://science.slashdot.org/story/12/04/14/012219/voyager-and-the-coming-great-hiatus-in-deep-space
- http://science.slashdot.org/story/11/12/07/2127247/voyager-1-exits-our-solar-system
- http://science.slashdot.org/story/11/04/28/2314203/voyager-set-to-enter-interstellar-space
- http://science.slashdot.org/story/10/12/14/1451216/voyager-1-beyond-solar-wind
Re:Always the frontrunner? (Score:4, Informative)
Re:Always the frontrunner? (Score:5, Informative)
It would be nice to think that one day we'll reach a technological level that allows us to overtake Voyager 1. I'm not that hopeful though. I think that the head start Voyager 1 has means that it always will be more remote from Earth than anything else constructed here. Excluding Pioneer 10, that is.
There's some planetary alignment issues such that it would be really hard to catch Voyager. The New Horizons probe, despite being something like the fastest probe ever launched, is moving considerably slower because it had unfavorable gravitational assists, something like 10% slower than voyager. The planets have to line up, unless you do something ridiculous like launch a tennis ball a Saturn-V
Both are practically slow crawling compared to the Helios probes from the late 70s/early 80s which were moving something like 6 times the speed, although toward the sun not away. The Helios probes are still the fastest controllable "things" produced by mankind. The "controllable" is necessary because there's a famous nuke bomb test film where analysis of adjacent frames shows a manhole cover moving about about 0.1c... at least for a little while.
Re:Voyager 2 launched first? (Score:5, Informative)
So Voyager 2 was launched weeks before Voyager 1? Was the launch schedule changed at the last minute?
No. Per this:
http://space.about.com/od/spaceexplorationhistory/p/voyager1.htm
"Voyager 1 was launched after Voyager 2, but because of a faster route, it exited the asteroid belt earlier than its twin. It began its Jovian imaging mission in April 1978 at a range of 265 million kilometers from the planet; images sent back by January the following year indicated that Jupiter's atmosphere was more turbulent than during the Pioneer flybys in 1973 and 1974."
Re:2020? (Score:5, Informative)
Communications, I believe. It is just going where its inertia takes it at this point, and heading out of the solar system. It is obviously still under the gravitational influence of bodies in the solar system(and all the other ones, as best we can tell); but it isn't on a path that would be described as an 'orbit' in anything like the usual use of the term.
Re:2020? (Score:5, Informative)
The two Voyagers are gyroscope stabilized, so they don't need fuel for attitude control.
They are powered by Plutonium 238 RTG's, and that power is steadily declining as the Plutonium decays and the thermocouples age. I think that is what the article is referring to. I wouldn't call them fuel.
Re:Some kind of dupe (Score:2, Informative)
Won't be very long? Voyager won't be near another star system for roughly 350,000 years. That's more than 30 times the length of recorded history.
That's wy the GP wrote: "it won't be before very long"...
Re:Always the frontrunner? (Score:5, Informative)
It would be nice to think that one day we'll reach a technological level that allows us to overtake Voyager 1.
Keep in mind that with the small velocities that our probes are leaving the Earth with at the moment, a small change of initial velocity makes for a big change in asymptotic velocity as the craft flies through the shallow parts of the gravity well (i.e., when it is far away). That means that we can already do that today.
You don't even need to integrate any trajectory to find this out, that's simple physics the kind of which I was doing in high school. Just calculate the kinetic + potential energy balance of the Sun-Earth-spacecraft system. Just escaping the Sun means balancing the (negative) potential energy of the probe within Sun's gravity well. The balance is v_terminal^2*m*(1/2) = E_p + v_initial^2*m*(1/2), where E_p is negative, of course, and v_initial is the speed relative to the Sun after leaving the Earth ("leaving the Earth" meaning here "getting far away enough so that the remaining potential energy caused by the presence of Earth won't skew the results too much"). If v_initial is 42.1 kps, you'll end up with v_terminal = 0. You'll get that if you leave Earth with initial speed of 16.6 kps which you can calculate in a similar manner. Now as to the the deltas to initial velocity of 16.6 kps near Earth and respective final velocities relative to the Sun in the infinity:
extra 1 kps => 10.6
extra 2 kps => 15
extra 3 kps => 18.4
extra 4 kps => 21.2
There are diminishing returns, but you can overtake Voyager 1 by having extra 3 kps when leaving the Earth *at any time*. The reason Voyager 1 is so fast despite having left Earth at a very modest velocity are the four grav assists. Today, all you need is the same ion engine that Dawn has and you're well on the way much faster than any probe before.
Re:Always the frontrunner? (Score:5, Informative)
Re:2020? (Score:5, Informative)
Re:Always the frontrunner? (Score:5, Informative)
Sorry, but wrong. Voyager I overtook Pioneer 10 in 1998 [uiowa.edu] :
Until 17 February 1998, the heliocentric radial distance of Pioneer 10 has been greater than that of any other manmade object. But late on that date Voyager 1's heliocentric radial distance, in the approximate apex direction, equaled that of Pioneer 10 at 69.419 AU. Thereafter, Voyager 1's distance will exceed that of Pioneer 10 at the approximate rate of 1.016 AU per year.
Re:Has it made it ? (Score:5, Informative)
As they state, it is currently within the heliosheath - the turbulent boundary layer between Sol's plasma bubble and the interstellar medium, so it's outside the region thoroughly dominated by the sun's influence, but not yet within the interstellar medium. Quite an interesting region in it's own right, but not terribly informative of either bounding environment.