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I didn’t realize the Voyagers relied on a once in a 175 year planetary alignment. What a lucky break technology had advanced to the point we could make use of

I didn’t realize the Voyagers relied on a once in a 175 year planetary alignment. What a lucky break technology had advanced to the point we could make use of it.

jmclnx 2y ago
And I remember the "crazies" saying the world will come to an end due to that alignment. That belief was reported in the main stream media. When it did not happen, I think they moved on to 2012 :)
- timthorn 2y ago
  Ah, yes - The Jupiter Effect: https://www.goodreads.com/book/show/3400930-the-jupiter-effect https://www.goodreads.com/book/show/3400930-the-jupiter-effe...
  - fwipsy 2y ago
    Forward by Isaac Asimov? I'm surprised he would have his name associated with this.
    - harrisi 2y ago
      Not just any foreword, a pretty big endorsement. You can borrow the book from the internet archive to read the full foreword, but here's the last bit: And in the end, it turns out that something will happen in 1982 that just may— No, no, read it for yourself. Read it carefully and you'll find it far more fascinating than the tale of any millionaire found stabbed in any library, locked or otherwise. And far more important, too especially if you live in California. ISAAC ASIMOV 17 April 1974
- akira2501 2y ago
  I think fascination with apocalypse is the fear of our individual mortality combined with the fear of missing out.
grapesodaaaaa 2y ago
I’m trying to figure out why the alignment was so important. Wouldn’t it be possible to get a gravity assist in any alignment - albeit just taking a little longer to ping-pong across the system?
- ericbarrett 2y ago
  The alignment greatly reduced the amount of energy/propellant/weight to launch the Voyager missions with all four of the outer planets on the menu. Alignments that allow you to reach a smaller set of the outer planets with the same budget are more common: years or decades. (Edit) Another thought, since you mentioned time—numerical computing power and the math required to exercise it have advanced greatly since the 1970s, and it's likely that some of the trajectories and maneuvers feasible (again with the same fuel budget) today, even if they took 100+ years to complete, weren't even calculable back then.
  - deleted 2y ago
    [deleted]
- vikingerik 2y ago
  The scenario where a gravity assist doesn't work is if turning sharply enough would require your minimum planetcentric approach distance to be less than the radius of the planet - you'd crash into it instead. This is why Voyager 2 couldn't also do Pluto - it would have needed to change course by roughly 90º at Neptune, which would have required going closer to the center of Neptune than Neptune's own radius. The most unusual gravity-assist alignment that we did was for Pioneer 11 going from Jupiter to Saturn. The encounters were separated by roughly 120º of heliocentric longitude. Pioneer 11 used Jupiter to bend its path "up" out of the ecliptic plane and encountered Saturn on the way back "down". Nowadays we wouldn't bother doing that (we'd wait for a more direct launch window instead), but the purpose of this was to get preliminary Jupiter and Saturn encounters done in time before Voyager's launch window for the grand tour alignment.
  - westurner 2y ago
kibwen 2y ago
It wasn't just a lucky break, it was the result of furious efforts by scientists to lobby years in advance to take advantage of the alignment, as well as engineers who repurposed two Mariner probes to save money, as well as canny NASA bureaucrats who sneakily downplayed the possibility of a full Grand Tour in order to reduce estimated costs (with the full intent to underpromise and overdeliver, which Voyager 2 successfully did by "coincidentally" being on course to visit Neptune and Uranus after completing its primary mission to Jupiter and Saturn (to this day, Voyager 2 remains the only visitor to Uranus and Neptune)).
- bigiain 2y ago
  Still a huge amount of luck involved. If that planetary alignment had happened even 10 years earlier NASA probably wouldn't have had the capability to do anything with it. If it had been sometime recently, say after the Challenger disaster, I doubt it would have got funding...
  - KennyBlanken 2y ago
    There's no way that a disaster on a manned mission would affect a satellite launch. They share nothing in common.
    - dylan604 2y ago
      if they used the same booster, say something like a Falcon 9, that was the cause of the disaster, anything using that booster would be put on hold until it was cleared. it just so happens the examples used very different systems, but that's not what you were referring to with your self assured declarative that just doesn't have as much weight as you want it to in modern launch systems.
    - lostlogin 2y ago
      I’m not sure that level of confidence is warranted. What’s going to happen with NASAs funding over the next few years? Or even SpaceX?
shagie 2y ago
The paper for it is readable - Fast Reconnaissance Missions to the Outer Solar System Derived from the Gravitational Field of Jupiter http://www.gravityassist.com/IAF3-2/Ref.%203-143.pdf http://www.gravityassist.com/IAF3-2/Ref.%203-143.pdf (1966) Also fun to play with is: https://trajbrowser.arc.nasa.gov/index.php https://trajbrowser.arc.nasa.gov/index.php (example query with multiple flybys of outer planets - https://trajbrowser.arc.nasa.gov/traj_browser.php?NEAs=on&NECs=on&chk_maxMag=on&maxMag=25&chk_maxOCC=on&maxOCC=4&chk_target_list=on&target_list=Jupiter%0D%0ASaturn&mission_class=oneway&mission_type=flyby&LD1=2015&LD2=2030&maxDT=5&DTunit=yrs&maxDV=20&min=DV&wdw_width=365&submit=Search#a_load_results https://trajbrowser.arc.nasa.gov/traj_browser.php?NEAs=on&NE... )

I didn’t realize the Voyagers relied on a once in a 175 year planetary alignment. What a lucky break technology had advanced to the point we could make use of it.

jmclnx 2y ago

And I remember the "crazies" saying the world will come to an end due to that alignment. That belief was reported in the main stream media. When it did not happen, I think they moved on to 2012 :)

timthorn 2y ago
Ah, yes - The Jupiter Effect: https://www.goodreads.com/book/show/3400930-the-jupiter-effect https://www.goodreads.com/book/show/3400930-the-jupiter-effe...
- fwipsy 2y ago
  Forward by Isaac Asimov? I'm surprised he would have his name associated with this.
  - harrisi 2y ago
    Not just any foreword, a pretty big endorsement. You can borrow the book from the internet archive to read the full foreword, but here's the last bit: And in the end, it turns out that something will happen in 1982 that just may— No, no, read it for yourself. Read it carefully and you'll find it far more fascinating than the tale of any millionaire found stabbed in any library, locked or otherwise. And far more important, too especially if you live in California. ISAAC ASIMOV 17 April 1974
akira2501 2y ago
I think fascination with apocalypse is the fear of our individual mortality combined with the fear of missing out.

grapesodaaaaa 2y ago

I’m trying to figure out why the alignment was so important. Wouldn’t it be possible to get a gravity assist in any alignment - albeit just taking a little longer to ping-pong across the system?

ericbarrett 2y ago
The alignment greatly reduced the amount of energy/propellant/weight to launch the Voyager missions with all four of the outer planets on the menu. Alignments that allow you to reach a smaller set of the outer planets with the same budget are more common: years or decades. (Edit) Another thought, since you mentioned time—numerical computing power and the math required to exercise it have advanced greatly since the 1970s, and it's likely that some of the trajectories and maneuvers feasible (again with the same fuel budget) today, even if they took 100+ years to complete, weren't even calculable back then.
- deleted 2y ago
  [deleted]
vikingerik 2y ago
The scenario where a gravity assist doesn't work is if turning sharply enough would require your minimum planetcentric approach distance to be less than the radius of the planet - you'd crash into it instead. This is why Voyager 2 couldn't also do Pluto - it would have needed to change course by roughly 90º at Neptune, which would have required going closer to the center of Neptune than Neptune's own radius. The most unusual gravity-assist alignment that we did was for Pioneer 11 going from Jupiter to Saturn. The encounters were separated by roughly 120º of heliocentric longitude. Pioneer 11 used Jupiter to bend its path "up" out of the ecliptic plane and encountered Saturn on the way back "down". Nowadays we wouldn't bother doing that (we'd wait for a more direct launch window instead), but the purpose of this was to get preliminary Jupiter and Saturn encounters done in time before Voyager's launch window for the grand tour alignment.
- westurner 2y ago

kibwen 2y ago

It wasn't just a lucky break, it was the result of furious efforts by scientists to lobby years in advance to take advantage of the alignment, as well as engineers who repurposed two Mariner probes to save money, as well as canny NASA bureaucrats who sneakily downplayed the possibility of a full Grand Tour in order to reduce estimated costs (with the full intent to underpromise and overdeliver, which Voyager 2 successfully did by "coincidentally" being on course to visit Neptune and Uranus after completing its primary mission to Jupiter and Saturn (to this day, Voyager 2 remains the only visitor to Uranus and Neptune)).

bigiain 2y ago
Still a huge amount of luck involved. If that planetary alignment had happened even 10 years earlier NASA probably wouldn't have had the capability to do anything with it. If it had been sometime recently, say after the Challenger disaster, I doubt it would have got funding...
- KennyBlanken 2y ago
  There's no way that a disaster on a manned mission would affect a satellite launch. They share nothing in common.
  - dylan604 2y ago
    if they used the same booster, say something like a Falcon 9, that was the cause of the disaster, anything using that booster would be put on hold until it was cleared. it just so happens the examples used very different systems, but that's not what you were referring to with your self assured declarative that just doesn't have as much weight as you want it to in modern launch systems.
  - lostlogin 2y ago
    I’m not sure that level of confidence is warranted. What’s going to happen with NASAs funding over the next few years? Or even SpaceX?

shagie 2y ago

The paper for it is readable - Fast Reconnaissance Missions to the Outer Solar System Derived from the Gravitational Field of Jupiter http://www.gravityassist.com/IAF3-2/Ref.%203-143.pdf http://www.gravityassist.com/IAF3-2/Ref.%203-143.pdf (1966) Also fun to play with is: https://trajbrowser.arc.nasa.gov/index.php https://trajbrowser.arc.nasa.gov/index.php (example query with multiple flybys of outer planets - https://trajbrowser.arc.nasa.gov/traj_browser.php?NEAs=on&NECs=on&chk_maxMag=on&maxMag=25&chk_maxOCC=on&maxOCC=4&chk_target_list=on&target_list=Jupiter%0D%0ASaturn&mission_class=oneway&mission_type=flyby&LD1=2015&LD2=2030&maxDT=5&DTunit=yrs&maxDV=20&min=DV&wdw_width=365&submit=Search#a_load_results https://trajbrowser.arc.nasa.gov/traj_browser.php?NEAs=on&NE... )