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My sincere hope is we revisit both uranus and Neptune within my lifetime. Each has only been visited once and that was over 30 years ago with the Voyager missi

by jmyeet 5y ago

My sincere hope is we revisit both uranus and Neptune within my lifetime. Each has only been visited once and that was over 30 years ago with the Voyager missions. We learned a lot but now we have way better tech, way better cameras and can learn way more. It takes a particular planetary alignment to make such a trip possible. The next such window is in the early 2030s. These outer Solar System missions are really expensive and take a long prep time so that window to prep a mission in time is rapidly closing. And that's to get there around 2040. People don't realize just how hard it is to reach these outer planets. New Horizons was a flyby on Pluto because an intercept mission was essentially impossible. Crossing such a large distance to a slow-moving planet means a massive delta-V budget (which is impractical or impossible) or it takes so long you risk instrument or mission failure. At least Uranus and Neptune have a much larger gravity well and have higher orbital speeds so gravitional capture is much more practical. We won't see both visited in the next window but I'd settle for at least one.

iso1631 5y ago
Window wise are you talking about slingshotting off Jupiter? The Voyager 2 "grand tour" type alignment only happens once every 200 years or so.
- Sharlin 5y ago
  I believe that's what the GP means, yes. With a future superheavy launch vehicle, however, a tandem mission could be possible, with separate Neptune and Uranus probes being inserted into different trajectories by the same LV/upper stage. Both spacecraft would still do a Jupiter slingshot but at different times.
- jmyeet 5y ago
  Voyager launched on a couple of Grand Tour alignments [1]. One was Jupiter, Saturn and Pluto. The other was Jupiter, Uranus and Neptune. And yes, that occurs every ~200 years. But that's not really relevant for reaching Uranus. That requires a more common alignment, which is with Jupiter. Jupiter orbits every ~12 years. Uranus orbits every 84 years. Jupiter is the vast bulk of mass in the Solar System that isn't the Sun, which is why it's such a good slingshot. So there's a window every ~12 years. If we miss the early 2030s window, we'll be waiting to at least the mid 2040s. [1]: https://en.wikipedia.org/wiki/Grand_Tour_program https://en.wikipedia.org/wiki/Grand_Tour_program
robbedpeter 5y ago
Maybe SpaceX can send a few probes. I'm sure Elon would be thrilled just for the meme potential, and they could treat it as product development for navigation and reconnaissance. If it became a regular thing, they could start sending swarms of probes wherever the current conjunction of planets makes optimal. SpaceX probes Uranus!
choeger 5y ago
Yeah, about that "impractical" part. I think it's time to reconsider it. With the Falcon, SpaceX has made access to space if not cheap then at least very affordable. The sheer cost of the Mars missions, as an example, make the market launch price look like change. The design also has to be perfect due to this "once in a decade" mentality. So I really think it's time to focus on "get there quickly" to make missions cheaper. Design a relatively simple vessel weighing around 40t or so with enormous ISP (electrical or chemical, whatever fits the bill) and then use it twice per year or even more often to send more or less standardized probes to whatever target you find interesting. I am well aware that this concept sketch trivializes many aspects of space missions: Communication, power, navigation to name just a few aspects. But I still think that oversizing and then using the same design often would be much cheaper in the long run.
- jerf 5y ago
  I'm looking forward to lifting fuel into orbit as the next major progress item for this. A lot of the math changes if you lift fuel into orbit. Our mindset is currently very confined by the need to launch everything in one shot. I'm not sure exactly how fast you could get to the outer planets, but I expect it's at least enough that you would no longer need a "grand tour" to do it. (Also depends on whether you just get there fast as a fly-by or whether you want to go into orbit, I'm sure.) Honestly kind of unsure why we're not hearing more about this already. The costs of it are an increasingly small fraction of what we're spending on these probes anyhow.
  - mr_overalls 5y ago
    Aren't multi-stage rockets essentially "lifting fuel into orbit"?
    - jerf 5y ago
      I mean fuel as the payload, to be used as fuel for future missions via something rendezvousing with it in orbit and picking up the fuel. You could think of it as one more stage, mathematically that's how you might treat it, but from an engineering perspective it's a qualitative difference versus what we have now.

by jmyeet 5y ago

iso1631 5y ago

Window wise are you talking about slingshotting off Jupiter? The Voyager 2 "grand tour" type alignment only happens once every 200 years or so.

Sharlin 5y ago
I believe that's what the GP means, yes. With a future superheavy launch vehicle, however, a tandem mission could be possible, with separate Neptune and Uranus probes being inserted into different trajectories by the same LV/upper stage. Both spacecraft would still do a Jupiter slingshot but at different times.
jmyeet 5y ago
Voyager launched on a couple of Grand Tour alignments [1]. One was Jupiter, Saturn and Pluto. The other was Jupiter, Uranus and Neptune. And yes, that occurs every ~200 years. But that's not really relevant for reaching Uranus. That requires a more common alignment, which is with Jupiter. Jupiter orbits every ~12 years. Uranus orbits every 84 years. Jupiter is the vast bulk of mass in the Solar System that isn't the Sun, which is why it's such a good slingshot. So there's a window every ~12 years. If we miss the early 2030s window, we'll be waiting to at least the mid 2040s. [1]: https://en.wikipedia.org/wiki/Grand_Tour_program https://en.wikipedia.org/wiki/Grand_Tour_program

robbedpeter 5y ago

Maybe SpaceX can send a few probes. I'm sure Elon would be thrilled just for the meme potential, and they could treat it as product development for navigation and reconnaissance. If it became a regular thing, they could start sending swarms of probes wherever the current conjunction of planets makes optimal. SpaceX probes Uranus!

choeger 5y ago

Yeah, about that "impractical" part. I think it's time to reconsider it. With the Falcon, SpaceX has made access to space if not cheap then at least very affordable. The sheer cost of the Mars missions, as an example, make the market launch price look like change. The design also has to be perfect due to this "once in a decade" mentality. So I really think it's time to focus on "get there quickly" to make missions cheaper. Design a relatively simple vessel weighing around 40t or so with enormous ISP (electrical or chemical, whatever fits the bill) and then use it twice per year or even more often to send more or less standardized probes to whatever target you find interesting. I am well aware that this concept sketch trivializes many aspects of space missions: Communication, power, navigation to name just a few aspects. But I still think that oversizing and then using the same design often would be much cheaper in the long run.

jerf 5y ago
I'm looking forward to lifting fuel into orbit as the next major progress item for this. A lot of the math changes if you lift fuel into orbit. Our mindset is currently very confined by the need to launch everything in one shot. I'm not sure exactly how fast you could get to the outer planets, but I expect it's at least enough that you would no longer need a "grand tour" to do it. (Also depends on whether you just get there fast as a fly-by or whether you want to go into orbit, I'm sure.) Honestly kind of unsure why we're not hearing more about this already. The costs of it are an increasingly small fraction of what we're spending on these probes anyhow.
- mr_overalls 5y ago
  Aren't multi-stage rockets essentially "lifting fuel into orbit"?
  - jerf 5y ago
    I mean fuel as the payload, to be used as fuel for future missions via something rendezvousing with it in orbit and picking up the fuel. You could think of it as one more stage, mathematically that's how you might treat it, but from an engineering perspective it's a qualitative difference versus what we have now.