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[wierd]

(I see someone has played star control)

However, it neednt be scifi clones. We already have DNA synthesis technology, it just isnt up to easily synthesizing whole genomes as a trivial exercise yet.

For a multibillionaire, like Elon Musk and pals, a 5000 member colony ship is within the realm of plausibility.

Burned toast:

Even if it is a generational ship, a reactionless drive overcomes a number of other problems that come from having single burn engines. So, even if it takes a few thousand years to get to the Gliese system (or other nearby candidate system), the vessel will be able to make course corrections, refuel in-transit, and a number of other things that a chemical rocket driven drive simply could not do.

Additionally, the NASA test was not to see if the em-drive "works"-- the chinese space agency already did that with a much better test setup designed to detect impulse. Instead, what the NASA test was evaluating was a different design by a different inventor who as asserting some radical microwave energy quackery. His engine was called the "QDrive", (then, now called the cannae drive) and had some silly ideas about how the thrust was going to be generated.  The "null" device was a device that had an active resonator, but had a topological design that according to the cannae drive's inventor, should result in zero thrust. It didn't.

Not that the em-drive's inventor is any less quacktastic, but his design produces more efficient thrust, as recorded by the chinese experiment.

[BurnedToast]

Burned toast:

Even if it is a generational ship, a reactionless drive overcomes a number of other problems that come from having single burn engines. So, even if it takes a few thousand years to get to the Gliese system (or other nearby candidate system), the vessel will be able to make course corrections, refuel in-transit, and a number of other things that a chemical rocket driven drive simply could not do.

My reply was only to his comment that the distance didn't matter because time compression would make the journey short for the passengers. While technically true, the amount of energy required to achieve that sort of time compression is just completely unreasonable.

Generation ships are a whole separate issue with their own problems, both engineering and moral.

[wierd]

Indeed. The trip would be:

1) Toxic, unless the ship is made of solid lead/and or/ totally encrusted in water ice for rad shielding
2) BORING AS HELL. The only diversions would be those created by the crew themselves. Due to the above, there probably wont even be any windows to look out of, and if you did, it may induce psychosis after awhile.
3) Dangerous. You think it's annoying when your car breaks down now? Try when your car breaks down after leaving the heliopause of the sol system.
4) Very hard to plan logistically. It would require cental planning a-la the command economies of the former soviet union and eastern bloc countries. History shows how well that went over, and how well humans responded to resource rationing.

A compromise might be chemical suspended animation with periodically scheduled wake-up periods for exercise, and health reasons. That would reduce the problems for a number of the above issues, and may even prolong the total elapsable time that humans can endure the voyage.

[LordBucket]

Wait, I thought we were discussing theoretical engines. Are we just looking for a way to become an interstellar civilization? We can do do that right now. We've had the technology to do that for decades, there have been a couple proposals. Most interesting was probably Project Prometheus which was estimated to get us to another star in only 50 years.

Alternately, same idea but with antimatter explosions rather than nuclear explosions, there was also Project Valkyrie. That's feasible. We could do it. Though It suffers from a problem of high energy requirements to produce all the antimatter required accelerate to large fractions of c, and unlike nuclear pulse projects, I don't think Valkyrie ever made it out of the planning stages. But we could do it within a single generation if we really wanted to.

It only took us 7 years from deciding to go to the moon to landing on the moon.  And throughout the 70s NASA was seriously talking about colonizing Mars, building a permanent moon base, visiting other stars and other generally awesome stuff. But then for whatever reason we collectively lots our will to explore space, and pretty much nothing happened.

[wierd]

Nuke propulsion can get you moving very quickly in a very short amount of time, true-- but it also is still a reaction mass based propulsion system, and once the fuel is exhausted, ship no change velocity no more.

In addition to that, the impulse equation changes after each and every detonation, since the ship gets lighter each time, having expended a nuke.

A reactionless drive on the other hand, has a mostly static vehicle mass, which makes computing velocity changes easier, and means that as long as the vessel has power, it can change course, speed up, or slow down.



As for what happened after the 70s..  The soviet union collapsed, and expending lots of money on political penis waving was no longer a matter of nationalist pride/ego.  As such, the funding was cut, and money was spent safeguarding the US as the last remaining superpower, leading to the political climate we now find ourselves in, with "Team america, World Police" type foriegn policy that the rest of the world wishes we would die in a fire over. (and I cant say I blame them)

Given that private enterprise is not beholden to nationalistic policies, and could reasonably leverage multinational resources and labor pools to accomplish such goals, I fully expect that this is where the future in humans space travel lies.

[Sergarr]

Reactionless drive also break one of the fundamental laws of nature, if taken at face value, so there's probably something shady going on there.

[wierd]

Not really;  charged virtual particles exhibit mass like terms, which is why they can modify momentum through the interaction. That they just go "Poof" shortly afterward leaving nothing behind makes physicists go nuts though.  The energy supplied to them has to go SOMEWHERE. Most likely, it gets converted into spacetime, or re-emitted as a photon if the energy delivered is significant enough.

This mass like term is also why hawking radiation could be real.  The mass like terms of virtual particles is already documented, after all.

[Sergarr]

They quite obviously can't simply leave nothing afterwards, since conservation of momentum is an unbreakable law of nature.

More likely, there's some virtual-virtual processes going on there that moves that momentum through space until it hits something and then transfers that impulse back into the real world... somewhere.

And, wierd? The idea that you can convert momentum to energy is one of the most weird ones I've heard.

[i2amroy]

As I recall the current idea with nuclear pulse propulsion is to combine it with a fuel scoop. There's tons of hydrogen out there in space, at the extremely low pressure of hundreds of atoms per square meter. If you stick a few kilometer wide scoop on the front of your spaceship, then you can just scoop that hydrogen up and turn it into hydrogen bombs to continue your pulse propulsion. It's not technology we've quite perfected yet, but it's mostly just simple engineering and logistics problems, no new physics or anything required.

As for antimatter, I'd say we would need to have a major breakthrough in both antimatter production and containment before we are going to do anything with it soon. Right now antimatter yearly production rates are mostly measured in atoms, and containment lifetimes in seconds. We've got a long way to go before we are talking the kilograms and decades that we'd need for any sort of antimatter propelled spacecraft.

And yeah, while even with nuclear pulse engines we aren't going to be seeing time dilations anywhere near enough to extend lives by more than a short handful of years, current designs could totally reach nearby stars in only a hundred years or so, fast enough that you might be able to stretch out a life that you got to see both the start and the end of the trip (and some of which contain some planets we think could very well be able to support life).

[Urist Tilaturist]

If you think hell would be boring, you must have the nopain tag...

We do not have the capability for interstellar travel now. Even going to Mars would cost hundreds of billions of dollars and possibly end with the death of the crew by radiation or some malfunction. Manned space exploration (probes are still going) stopped because of the ludicrous public expenditure long before the end of the Cold War - the last moon landing was 1972 - because they had already done the moon, and Mars was a step too far, and still is in practice, whatever NASA's empty promises are.

If you think the USA was not acting as "world police" during the cold war as well, you do not know much cold war history. Adventures like the Bay of Pigs, Viet Nam, Operation Condor and supporting all kinds of dictators (Saddam) and terrorists (Taliban) were standard procedure.

By the time any sort of interstellar travel is possible, the crew of the craft will either be modified to remove ageing, cyborgs or uploaded consciousnesses on computers. All these advances seem far closer than flying to Proxima Centauri.

[mainiac]

I think an industrial spacedock on the moon which would be capable of making much larger craft is a lot more immediate then some sort of transhuman future.  The problem with off planet colonies is that it's really expensive to get mass into space.  While being more efficient with your mass is one answer, another answer is to just increase your ability to get redundant equipment into space.  A large enough spacecraft is the solution to pretty much any problem.

[Sergarr]

I think an industrial spacedock on the moon which would be capable of making much larger craft is a lot more immediate then some sort of transhuman future.  The problem with off planet colonies is that it's really expensive to get mass into space.  While being more efficient with your mass is one answer, another answer is to just increase your ability to get redundant equipment into space.  A large enough spacecraft is the solution to pretty much any problem.

Except for funding and Congress. No ordinary spacecraft can hope to solve these two. Only a true technological terror would be capable of that.

[mainiac]

Well if you have a Death Star you can just dissolve the Galactic Senate.

[Rez]

Perhaps one of the new aerospace start-ups will go mad scientist and build the Sea Dragon (or another BDB).  It was estimated to have a payload of 450000 kg at $667 per kg.

Why would anyone invest in such a monstrosity?  To be the source of all space development for the foreseeable future. With payloads that heavy, you could lift entire industries into orbit. 

[wierd]

They quite obviously can't simply leave nothing afterwards, since conservation of momentum is an unbreakable law of nature.

More likely, there's some virtual-virtual processes going on there that moves that momentum through space until it hits something and then transfers that impulse back into the real world... somewhere.

And, wierd? The idea that you can convert momentum to energy is one of the most weird ones I've heard.

No, not weird at all.  Think about what heat energy is. It's just diffuse kinetic energy, related to the chaotic motion of the constituent atoms, all of which have discrete vectors of momentum, all jostling around together.  Now, throw in black body radiation. photons are emitted from the matter as long as it is hotter than absolute zero, and this emission results in the "cooling" of the substance. Likewise, absorption of photons increases the temperature.  Since the atoms stop jostling with as much momentum as they emit photons, it is possible to describe momentum as an energy quanta.

There's also the wide world of radiation pressure, and the math behind why particle accelerators need fast moving particles to get greater collision energies. (the momentum of the particles adds to the energy value of the collision)

So, no. not a strange thing at all.