[X] My Assistant

[nprev]

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?

[nprev]

Points noted, Bob. Problem is, as Helvick so ably articulated, that the kinetic energy release from a collision with even minute objects at these speeds is so large that it would almost certainly destroy a spacecraft even if it had a shield that could absorb the impact.

I'd think that a jolt of hundreds of thousands of Gs would result from such a collision. While the structure itself might survive if designed appropriately, I can't begin to imagine all the things that would happen to, for example, solder joints on the circuit boards. Unless the bus & payload electronics physically consisted of something like a giant diamond crystal with few (if any) mechanical interfaces like connectors, I just don't see the thing operating at nominal levels after the event.

[marsbug]

Give it all of the above, lasers, layerd areogel shields, small cross section, and include huge shock absorbers.

Perhaps trying to make one probe proof against all possible disasters is the wrong approach. If we have our unfeasibly huge power supply why not split it between a couple of dozen probes, take some basic precautions with each (aerogel shields, small cross section ect) and accept that at least some of them won't make it?
If IEE comes to fruition it might open the door for missions to the interstellar medium that would tell us exactly what precautions are needed, and in what amount.

Edit: nprev point about the power supply is well made, clearly it is this more than engineering issues which will be a showstopper for any mission to another star. Although not forever I hope.

[nprev]

Perhaps trying to make one probe proof against all possible disasters is the wrong approach. If we have our unfeasibly huge power supply why not split it between a couple of dozen probes, take some basic precautions with each (aerogel shields, small cross section ect) and accept that at least some of them won't make it?

That would be an excellent approach if it's affordable by the time that high-energy technology's available. IMHO, we sure don't want to launch our first interstellar Flagship-class equivalent mission without a few smaller, cheaper forays first. Pioneers necessarily must precede Galileos & Cassinis!

EDIT: Here's a worst-case scenario thought. How about two spacecraft for the first interstellar mission? The first (leading) one is big & dumb. It consists of as much durable mass as we can fly, and its only real function is to act as a cosmic bulldozer, paving the way for spacecraft #2, which is smaller & smarter (the payload).

#1 doesn't even have to decelerate as it approaches the target star; it's no longer needed when #2 begins deceleration, since the drive exhaust in this scenario would probably be energetic enough to zorch incoming dust particles along the line of flight.

Another thing I like about this is that if #1 actually hits something any secondary debris is still probably traveling at or near the transit velocity (in the same inertial reference frame, anyhow), so #2's shielding probably doesn't have to be extremely robust.

[Thu]

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EDIT: Here's a worst-case scenario thought. How about two spacecraft for the first interstellar mission? The first (leading) one is big & dumb. It consists of as much durable mass as we can fly, and its only real function is to act as a cosmic bulldozer, paving the way for spacecraft #2, which is smaller & smarter (the payload).
...

Good idea but I think this will lead to a very challenging positioning/navigation problem as S/C #2 must follow a straight line left behind by #1 at extremely high speed.

There's another idea to send a giant spider web-like spacecraft for the first interstellar mission, driven by powerful laze beam from Earth orbit. Its light-weight miniatured payload will be distributed at the web's many nodes to counter against the problem of hitting dust particles along the way. If some nodes fail, the remaining will continue to operate just like the way the Internet works.

[marsbug]

I've always liked the idea of propelling a space-sail using lasers, and you could even decelerate at the target star by sending a secound sail/mirror ahead to reflect the laser back at the first.
However I have read a laser sail study (soz I can't remember the title or author) that the laser would need a titanic muzzle apeture to drive the sail across interstellar distances, something like 10,000 meters. If anyone else knows what I'm talking about could you direct me toward the study as I can't remember why the laser needed to be so large. After all even a ten km laser would look like a point source after travelling from earth to mars, never mind a fraction of the distance to alpha centauri.