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Interstellar Precursor - When? How?


SSR Kermit

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There is a special place in my heart for Voyager. Not the Janeway one, although I like her too, but Voyager 1 and Voyager 2 are missions that I have followed my entire (conscious) life. Voyager 2 is STILL doing science! I saw the launch of New Horizons on Nasa TV with some other space geeks, and I'm super excited for the "Fastest Thing Ever" to shoot past Pluto into the kuiper belt and towards the fascinating scattered disc, perhaps glimpsing some other transneptunian objects. However, New Horizons will never overtake Voyager, due to the latters' gravity assists around the giants.

When will we go further and faster? What kind of spacecraft will overtake Voyager as "Really the Furthest and Fastest" and head for the stars?

I personally believe the first interstellar precursors will use only current science but with some new tech; given the political climate nuclear is unlikely in the coming century, so compact, long term energy will have to use novel tech. Solar isn't an option, obviously. The orbital infrastructure for beamed power isn't likely to get it's budget approved; I think it will be an autonomous mission. Probably ion engines. Solar sails are unproven, magnetohydrodynamic propulsion as well-- developing those techs is prohibitively expensive, given that it needs to happen (and likely fail a few times) in deep space.

So I'm thinking, a conventional chemical rocket assembled and launched from LEO as a transfer stage to escape velocity and an extended cruise phase with ion engines. I doubt it will really be designed to actually reach anything, but to study the interstellar medium some ways away from the heliosphere.

I believe the JAXA are the ones who will do it, based on their willingness to do amazing stuff (the quirks of the Hayabusa missions come to mind) and their growing expertise with ion engines. Also, they describe what they are doing as "pawa uppu ion engines" -- they're applying power-ups to their ion engines. My money's on them!

What do you think?

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Further, maybe, but not faster. Ion engines, while possessing high specific impulse, have little in the thrust department. Chemical rockets need enormous fuel tanks for an interstellar mission, even for small probes; Voyager 1 & 2 took multiple gravity assists in order to get where they are now.

My bet for an interstellar mission would be when the first NTR took flight. It had been studied extensively in the NERVA program, and deemed ready for integration into current spacecraft designs. If the political climate and public fears on anything nuclear were nonexistent, an NTR spacecraft could be launched in the short term.

If not NTR, photon sails could also do the job. It works by capturing light pressure, either from the Sun or a laser facility, and use it to propel the spacecraft. It needs neither propellant nor electricity from the spacecraft itself, and it works indefinitely, until the laser is turned off or the Sun died. The caveat is that it produces very small amounts of thrust; on the orders of micronewtons to millinewtons. It would take decades to make significant maneuvers.

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  shynung said:
Further, maybe, but not faster.

In space, kind of the same thing, no?

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My bet for an interstellar mission would be when the first NTR took flight. It had been studied extensively in the NERVA program, and deemed ready for integration into current spacecraft designs. If the political climate and public fears on anything nuclear were nonexistent, an NTR spacecraft could be launched in the short term.

I just don't think that will happen. Not even RTGs are produced anymore.

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If not NTR, photon sails could also do the job. It works by capturing light pressure, either from the Sun or a laser facility, and use it to propel the spacecraft. It needs neither propellant nor electricity from the spacecraft itself, and it works indefinitely, until the laser is turned off or the Sun died. The caveat is that it produces very small amounts of thrust; on the orders of micronewtons to millinewtons. It would take decades to make significant maneuvers.

Again, I just don't think anyone is going to pay for developing those techs. And they lose facility outside the heliosphere unless you deploy lasers in a sun-polar orbit -- or accelerate out of the orbital plane. Maintaining those facilities for decades or centuries isn't likely to happen. That's my reasoning, at least.

Do you see any reason why someone would invest all that over such a long period, or is it simply not going to happen unless it's nuclear?

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  SSR Kermit said:
In space, kind of the same thing, no?

Actually, no. Distance and speed still means the same thing, whether on the ground or in space.

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I just don't think that will happen. Not even RTGs are produced anymore.

The recent Curiosity rover sent to Mars was powered by RTGs. In this case, the public at large, including politicians, know little about it.

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Again, I just don't think anyone is going to pay for developing those techs. And they lose facility outside the heliosphere unless you deploy lasers in a sun-polar orbit -- or accelerate out of the orbital plane. Maintaining those facilities for decades or centuries isn't likely to happen. That's my reasoning, at least.

Photon sails don't necessarily need laser facilities, they still work on Solar radiation. And when space travel is as common as air travel, laser facilities could be as common as airports, but only if laser beam propulsions have advanced that much.

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Do you see any reason why someone would invest all that over such a long period, or is it simply not going to happen unless it's nuclear?

The reason might be because they find space exploration lucrative. For this, things such as asteroid mining and moon mining must be feasible and relatively safe. Other than that, space manufacturing and storage facilities might also be highly profitable. A kilogram of water, while almost worthless in many parts of the world, carry premium prices in orbit because of the expense to lift them off from the surface. Same goes for various metals and elements found in moons and asteroids.

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