The Most Scientific Plausible Method of Interstellar Movemen

[eion]

Fine Destructionator, you win the argument over which crazy scheme will get us to the stars. I love how GMB starts these threads and never shows up again.

I just mentioned NSWR because no one else had, and I thought it a novel idea that combines high trust with high exhaust velocity (a rather unique feat), solves some of the problems of Orion (while creating a few of its own), and is comparativly victorian in design compared to over intersteller propulsion methods.

You've got some factual errors in your posting, mostly about fusion and confusion between D-T and D-He3, but I'm too tired of this shit to correct them.

[eion]

GHETTO EDIT: on further reading the Discovery II does use a divertor channel to dump a portion of the reactant into the exhaust to heat it.

[Wyrm]

The major benefit it brings to interstellar propulsion is the fact that it produces virtually no neutrons, and therefore no significant neutron radiation and the resulting reactor embrittlement.

Your own source says that the D3He process puts out about 3% of its power in neutron radiation. While this is a significant improvement over 80% in neutron radiation for DT, this is hardly "virtually no neutrons".

Points on the other stuff.

Since you aren't replacing the entire reactor assembly every decade or so you can afford to design a "tighter" confinement system.

You'll only be replacing them every century or so, but it still won't get you to the nearest star if you're only going 3%c.

[eion]

The major benefit it brings to interstellar propulsion is the fact that it produces virtually no neutrons, and therefore no significant neutron radiation and the resulting reactor embrittlement.

Your own source says that the D3He process puts out about 3% of its power in neutron radiation. While this is a significant improvement over 80% in neutron radiation for DT, this is hardly "virtually no neutrons".

Points on the other stuff.

True, the source I had in front of me at the time didn't list a specific figure, but the neutrons aren't coming from the main D-He3 reaction, but rather from side D-D reactions, so better reactor design might be able to cut that 3% down further by reducing those side reactions.

Since you aren't replacing the entire reactor assembly every decade or so you can afford to design a "tighter" confinement system.

You'll only be replacing them every century or so, but it still won't get you to the nearest star if you're only going 3%c.

Well if you use the D-He3 only for power and propulsion once you reach the target location you can just leave it turned off until you get there, and use whatever other means of propulsion to get to the star. That means you'll have a century of scanning time versus a century of travel time.

[Wyrm]

True, the source I had in front of me at the time didn't list a specific figure, but the neutrons aren't coming from the main D-He3 reaction, but rather from side D-D reactions, so better reactor design might be able to cut that 3% down further by reducing those side reactions.

Unless the reactor can magically sort the nuclei such that only the deuterium smashes into the helium-3, I don't see how that's possible. The fusion results from thermal motion of the nuclei, so there will inevidably be a small percentage of deuterium smacking together with itself and fusing. In fact, it will fuse into more ³He, so it's probably an important contribution to the characteristics of the D-³He reaction.

[eion]

True, the source I had in front of me at the time didn't list a specific figure, but the neutrons aren't coming from the main D-He3 reaction, but rather from side D-D reactions, so better reactor design might be able to cut that 3% down further by reducing those side reactions.

Unless the reactor can magically sort the nuclei such that only the deuterium smashes into the helium-3, I don't see how that's possible. The fusion results from thermal motion of the nuclei, so there will inevidably be a small percentage of deuterium smacking together with itself and fusing. In fact, it will fuse into more ³He, so it's probably an important contribution to the characteristics of the D-³He reaction.

Then I guess a hundred year running life will just have to do. I can't think of too many other powerplants you can run for 100 years plus without a complete overhaul.

[HMS Conqueror]

Anti-matter is probably the best candidate for a propulsion system that has semi-acceptable performance without requiring made-up physics. It is still rather speculative because of production and containment problems, however. The most dull answer is, "There is no plausible method of interstellar movement."

[GrandMasterTerwynn]

Anti-matter is probably the best candidate for a propulsion system that has semi-acceptable performance without requiring made-up physics. It is still rather speculative because of production and containment problems, however. The most dull answer is, "There is no plausible method of interstellar movement."

I have to ask . . . did you even bother to read the whole fucking thread first? Or did you just skim the OP and jump right to the end like a retard? I mean, there's three pages that go into loving detail why "no plausible method of interstellar movement" is, in fact, comically wrong.

Of course, antimatter itself, is also quite a ways down the plausibility list. Barring some magic physics we don't know about, the only way to reliably produce it is by smashing atoms into other atoms. Which means papering the inner Solar System with solar-powered atom-smashers. On top of the challenges implied in getting all that antimatter into containment vessels, and stopping the whole mess from cooking off from a particularly energetic cosmic ray strike. At which point, you must then contend with the fact that antimatter reactions produce useless neutrinos and deeply-penetrating gamma rays. It's certainly less plausible than fusion (and, as we all well know, fusion has its own issues.) It's probably even less plausible than interstellar sail, since you can overcome the problems with constructing a single giant laser by building a bunch of smaller ones.

[adam_grif]

Like I said, you wouldn't have ONE big laser pushing it, you'd have like 30, in a row, where it would leave the range of one and then come into the range of another. Obviously it requires a significant infrastructure investment, but if it means you can get to 20 or 30% of C instead of 2 or 3%, it's going to be fantastic.

[sirocco]

But the farther you get, the less effect the laser array will have on your acceleration.

If they are in the inner solar system, they can be powered by the sun and then deliver more thrust to your spacecraft. Depends on how far it's still effective.

In the outer solar system, you'd probably have to count on nuclear reactors (fusion or fission) to provide sufficient power. but you could get farther too

[Junghalli]

But the farther you get, the less effect the laser array will have on your acceleration.

That's why the Forward lightsail proposal calls for a ridiculously huge focusing device (1000 km across); to focus the laser tightly enough that it's a potent propulsive force even at very large distances. A less ambitious proposal might be the sailbeam concept, where you accelerate lots of tiny sails quickly and they transfer momentum to the ship by hitting it (more precisely by being vaporized and ionized by a laser, particle beam, or collision with a small impactor dropped behind the ship, and then hitting a magsail's field; a direct physical collision with the ship probably wouldn't be too healthy for it at the kind of velocities we're talking about here, even if the individual sails might mass milligrams).

[Sea Skimmer]

A laser pumped solar sail sounds like a damn good way to initially accelerate a ship, after which you dump the sails. It’s pretty implausible as a means of propulsion for the whole trip simply because it cannot be reliable. Sending a ship out for a 50 year trip and leaving it totally dependent on the political stability of the home system is just a bad idea. I mean what if hypothetically the USSR had launched such a ship in 1980, then collapsed in 1991 and can’t afford to turn on the laser anymore? Everyone just dies in space? Even automated lasers stationed on the edges of the solar system will still need some kind of maintenance and constant control, and they’d be exposed to attack should a war break out.

The number one reason to spread past the solar system, which already has vast resources and endless space, is to ensure a reliable existence of humanity. It doesn’t make sense to me to spend so damn much money to build the required fleet of ships, sending just one at a time is far too unsafe, and then risk it all being screwed over by a change of government. Using the sail only for initial acceleration would also remove the need for massive elaborate laser beam focusing systems, which might end up costing just as much as building colossal interstellar ships which are almost all fuel. Breaking requirements could be reduced enormously by dumping most of the ships fuel tank along the way as well. Note that I am considering everything other then the remote laser system as falling under 'fuel', not calling for any specific alternative. Just that I think very strong reason exists to make the ships capable of independent operations past the first couple years.

[sirocco]

A laser pumped solar sail sounds like a damn good way to initially accelerate a ship, after which you dump the sails. It’s pretty implausible as a means of propulsion for the whole trip simply because it cannot be reliable. Sending a ship out for a 50 year trip and leaving it totally dependent on the political stability of the home system is just a bad idea. I mean what if hypothetically the USSR had launched such a ship in 1980, then collapsed in 1991 and can’t afford to turn on the laser anymore? Everyone just dies in space? Even automated lasers stationed on the edges of the solar system will still need some kind of maintenance and constant control, and they’d be exposed to attack should a war break out.

The number one reason to spread past the solar system, which already has vast resources and endless space, is to ensure a reliable existence of humanity. It doesn’t make sense to me to spend so damn much money to build the required fleet of ships, sending just one at a time is far too unsafe, and then risk it all being screwed over by a change of government. Using the sail only for initial acceleration would also remove the need for massive elaborate laser beam focusing systems, which might end up costing just as much as building colossal interstellar ships which are almost all fuel. Breaking requirements could be reduced enormously by dumping most of the ships fuel tank along the way as well. Note that I am considering everything other then the remote laser system as falling under 'fuel', not calling for any specific alternative. Just that I think very strong reason exists to make the ships capable of independent operations past the first couple years.

I think the remote laser system will be a later addition to space travel like in Avatar. You'll need first companies that have economic interests in the neighbor solar system and want their ship to get there faster. And you'll probably have the same laser array at the receiving end.

For regular exploration, you'll have robots and AI instead of humans. Even if you shut down the laser, they will drift until they meet something. At worst they can use the anti-slingshot effect to slow down along the way.

For colonization, potentially the same thing except the fact that people will feel safer with bringing the propulsion system with them. At best, they could always mine/extract the fuel on the way to their destination. The laser arrays will just be the initial boost to reduce fuel expenditure.

As to why go to space, I'd say virtual immortality. Self preservation and scientific boost is just the cherry on top of the gigantic cake that is the awesomeness of seeing phenomenon that have never been seen by the naked eye. And build something that will not be affected by what happens in our solar system.

Because, let's face it our world has suffered at least 3 or 4 massive extinction episodes (MEE) seperated by eras that were far longer than our own. Nothing can be really said about mankind ability to avoid or survive a MEE until the day we have to face one. Could be an asteroid on collision course with Earth or a brown dwarf on collision course with Jupiter. We may be able to do something about the first problem but the latter? I see death at short or long term. (But don't worry it will only be about us... Life will find another way.)