[X] My Assistant

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If this thread's in the wrong place, please relocate...thanks!

Assuming for the sake of argument here that someday we'll have propulsion systems capable of propelling vehicles at a significant fraction of the speed of light, what kinds of technical challenges will be presented by the interstellar medium?

Right out of the gate, I can't see how anything we might build could survive hitting so much as a dust grain at even 0.01C. Heavy forward shields have been proposed, but the jolts from such collisions even if the spacecraft isn't vaporized would seem a bit unsettling to the payload.

Assuming that issue can be overcome and that we can actually go even faster (<0.5C), at what point would interstellar hydrogen become aerodynamically (or even hydrodynamically!) significant as far as drag? Would true starships actually have to look something like hypersonic aircraft, or even subs depending on relative hydrogen density?

[Guest_Myran_*]

Some nice ideas have been presented here, but dividing a probe into several miniature ones doesnt solve one of the most important problems. And that is communication back to Earth.
Would those 'starwhisps' by some magical trick somehow pull a terrawatt laser and nuclear reactor our of their sleeve?
(Yes the sail items might be modified to work as one dish for radio also, but again, that would add quite to the complexity of the sail and the number of things it should be able to do. Then the power needed for transmission would not be that much smaller and complex radio signals carrying megabytes of data will degrade more than laser in the interaction with gas, the stellar wind, galactic magnetic field etc etc.)

Another misunderstanding with lightsails is that they're unable to break their speed. They actually are!

One way would be to use the laser light itself and change to the opposite tack, so that the 'mirror' surface directs the laser light forward.
(Anyone who knows a bit of sailing here? Its more or less the same thing as when you arrange the sails of a ship to go against the wind.)

Its not as efficient as the acceleration but if you could charge the sail with quite a lot of electricity it would generate its own magnetic field and choosing the polarity the sail would be able to break. If the heliosphere around that star are as extensive as for Sol it could break for almost a lightyear in this fashion.

Last and most risky would be to go very near the destination star breaking both by the light and stellar wind.

One insterstellar probe might use not only one but two or all of these methods to either break enough to get a decent observation time at the target star or even come to a stop and so be able to explore interesting worlds one by one at closer range.

[marsbug]

Some nice ideas have been presented here, but dividing a probe into several miniature ones doesnt solve one of the most important problems. And that is communication back to Earth.
Would those 'starwhisps' by some magical trick somehow pull a terrawatt laser and nuclear reactor our of their sleeve?

I would guess that this is where the self replicating probe idea comes into its own, as a probe that could build a copy of itself could build a reactor and transmitter on site as well- if it could find suitable resorces.