Sedna is one of the most distant objects in the Solar System. Its about 3 times as far from the Sun ad Neptune is.
Is there any technically feasible way to get a probe there? I suspect the mission would have a decades long trip.
Getting there is easy. The same techniques that can be used to get to Neptune or Pluto can be used to get there. It just takes three times as long.
Would an ion-drive spacecraft be feasible? I’m sure it would eventually run out of available solar power once it passes, say, Jupiter, and my WAG is that an RTG-powered ion thruster would probably be too feeble to bother with.
But, as a comparison point: the Dawn mission to Ceres is a solar-powered, ion-drive spacecraft flying a fair bit past Earth’s orbit. The ion propulsion system gives it 10 km/s delta V. It’s weight, including the xenon propellant, is 1240 kg.
New Horizons, weighing only 478 kg, was launched at 16.24 km/s by one of the heaviest available launchers. It used a Star-48b solid rocket 3rd stage, which weighs about 2100 kg. Perhaps an ion-powered inner solar system boost stage could be used instead? Are there any ion thrusters that could provide useful amounts of thrust in the outer solar system, just using a few-hundred watt RTG?
More simply, if money was no object, a mission to Sedna could launch a probe similar to New Horizons with a larger launch vehicle (Delta IV heavy, or in future years potentially Falcon Heavy or SLS).
I need to get myself to lab now, but I’ll do some quick calcs later to see how fast we can launch a deep-space probe using existing or near future technology.
Sadly I suspect Sedna will not get a probe anytime soon. Unless there is a major cost reduction in what such a probe would cost and/or a breakthrough in propulsion technology.
The Pluto probe got lucky so to speak. The people responsible for it pushed like hell to get it and keep alive program wise. And, as the ice dwarf formerly known as Pluto the Planet, it had some cache left. And, it was on the inner part of its orbit, so that made a good argument for “let’s go now, while it’s closer”. And “lets go now while its more active because its closer (summer basically)”. And probably some other circumstantial dynamics that I’m not thinking of at the moment.
Pluto was the last of the planets. It’s also the King (and closest) of the many many such kind of objects past Neptune.
It would be a very hard sell economically speaking, politically speaking, and probably even scientifically speaking to justify a probe dedicated to go to Sedna or its other distant relatives out that way.
My WAG is young people today MIGHT see such a probe somewhere around retirement age.
Oh, sure, it is *technologically *possible to get a probe to Sedna. The Voyager craft are even farther out than that, now - it just took decades to get there, that’s all.
The biggest problem is getting funding and someone willing to sponsor a probe that won’t see results for half a human lifetime.
Could New Horizons get there?
New Horizons is a mighty long way from Sedna at the moment.
For random readers that don’t know about such things.
The NASA Voyager 1 and 2 projects were rather lucky timing wise.
Due to planetary alignment, they could hit Jupiter (and gain speed), then hit Saturn (and gain speed), then hit Uranus (sorry bout that, unless thats your thing)(and gain speed), then finish with Neptune (and gain speed again, though I doubt the final boost was much of a deal science wise).
It was called the Great Alignment IIRC. Fortunately it was recognized early enough in the space probe business (though I would argue that had it happened a few decades later that would have been a good thing).
Off the top of my head, I don’t know how often ALL FOUR are so usefully aligned, but I suspect its rather uncommon time/percentage wise.
The probe’s name should be Whip Me, Beat Me, Call Me Sedna
Can we walk on her with spike heeled shoes on?
Man, I gotta story to tell there.
They would probably need another alignment like the above so as to see both Sedna and Eris (+ anything else they could reach). Changing delta-vee is HARD…
Getting a small probe to Sedna isn’t that hard. We could even do it reasonably quickly if we wanted to - Launch the smallest probe possible on something like a Falcon Heavy or the SLS with a really large boost stage, or build a Cassini-like probe with a powerful nuclear source and use ion thrusters, or both.
If you really wanted to get there fast, launch the satellite on one rocket, and a huge booster stage on another, connect them up in orbit, and fire away.
So the 3rd stage plus probe weighed about 2600 kg. A Falcon Heavy could lift 53,000 kg into LEO. In comparison, the Atlas V used to launch New Horizons has a max payload to LEO of 9,800–18,810 kg, depending on configuration.
So imagine the same probe with a boost stage 20 times the size of the one New Horizons had. How quickly could we get that probe to Sedna? Even Cassini, one of the larger probes we have sent out, weighs only 5,712 kg, including propellant. A probe like that launched on a Falcon Heavy could have an additional boost stage with over 20,000 kg of fuel.
Or, with a rocket that size we could launch a probe that has an honest-to-god nuclear reactor on it, driving a nuclear rocket. A nuclear rocket has been in NASA’s plans for decades, but was finally killed for budgetary reasons. But if we had a real need to get out to the Kuiper belt and do major science out there, we could build nuclear rocket engines and large probes and launch them with Falcon Heavy or SLS.
It really comes down to cost and tradeoffs. Would we learn enough from a mission to Sedna to warrant the expense of a major planetary mission, rather than use those resources to go somewhere more interesting and a lot closer, such as Europa? I think if we discovered something really incredible on Pluto such as life or a liquid underground ocean, that might change our priorities a bit But that would probably result in another mission to Pluto - not one to Sedna.
If it turns out that Ceres has a liquid ocean somewhere under its crust, that strikes me as a much better candidate for a new major mission. And it’s a hell of a lot easier to get to.
BTW, when the new generation of giant telescopes start coming online in the 2020’s, I think we’re going to discover a lot more Kuiper Belt objects - possibly including some planets much larger, maybe even up to earth-sized. There is even speculation that there may be brown dwarf stars circling around out there. The Kuiper Belt is bound to get a lot more interesting in the next decade or two, but it’s also very far away.
It would be quicker to back up and send a probe to the Andes.
You seem to be assuming that the New Horizons’ 3rd stage was put into LEO and started from there, but that’s not correct. The Centaur 2nd stage rocket put the whole probe + 3rd stage motor into an Earth escape trajectory. The spent Centaur coasted halfway to Jupiter after the 3rd stage separated.
The Atlas V 551 configuration (used for New Horizons) can put 8.7 tons into geostationary transfer orbit, while the Falcon 9 Heavy can put 21.2 tons. So the mass available for the 3rd stage + probe is more like 2.5 times larger than New Horizons, not 20.
I was basing the math on the actual mass of the new Horizons probe, which was only about 2.6 tons. I assumed that since it was much smaller than the theoretical limit of the Atlas V, it must have been launched with one of the smaller configurations, or that the launch was combined with another satellite or something. I had assumed that the payload was launched from LEO after separating from the Atlas. If not, then you’re correct.
Still, even given the limitations of the rocket equation, increasing the propellant by 2.5 times is going to make for a much speedier probe. Mind you, once you get away from optimum orbits the fuel requirements go up dramatically, so perhaps it wouldn’t be ‘that’ much faster.
However, there’s still the option of building nuclear rockets and using those like we were planning to do with the Jupiter Icy Moons Orbiter. We should be building those anyway for future Jovian and Saturnian missions to explore the moons.
The bottom line remains that Sedna currently offers nothing interesting enough to warrant such an ambitious project. Hell, New Horizons only got funded by the skin of its teeth, and it had the justification that it would likely be the last opportunity in our lifetime to examine Pluto’s atmosphere before it froze out.