Is it time to give interstellar travel a shot?

[78stonewobble]

Well it's still an interesting "technological" limit for space travel, especially if we wanted to go with the "only send embryos" route (raised by robots at destination).

[mego-pie]

ever heard of the orion projected? it's relatively reasonable price wise and could reach a speed of 3.3% of the speed of light in just 10 days. it's been possible since the fifties. there are newer even better and more efficient versions based on the same principle which are not far of from being possible.

[Nuke]

now try and pull it off in a nuclear non-proliferation society. maybe the north koreans can build one.

[Accelerando]

for an interstellar mission using fission fuel, how does decay constrain mission time or increase fuel mass requirement? like Orion or fission-fragment rocket, or an Orion system for low fraction of c and FFR to boost to relativistic velocity, like 10% c?

[Nuke]

for an interstellar mission using fission fuel, how does decay constrain mission time or increase fuel mass requirement? like Orion or fission-fragment rocket, or an Orion system for low fraction of c and FFR to boost to relativistic velocity, like 10% c?

idk, i think you can just store fuel in its natural state and process it in flight. that would be your best bet. idk what the shelf life of weapons grade plutonium is.. according to wikipedia a ready to fire pit has an estimated shelf life of a century or more (wikipedia is a horrible source though).

http://en.wikipedia.org/wiki/Pit_(nuclear_weapon)#Pit_sharing_between_weapons

Edited March 21, 2014 by Nuke

[Accelerando]

idk, i think you can just store fuel in its natural state and process it in flight. that would be your best bet. idk what the shelf life of weapons grade plutonium is.. according to wikipedia a ready to fire pit has an estimated shelf life of a century or more (wikipedia is a horrible source though).

http://en.wikipedia.org/wiki/Pit_(nuclear_weapon)#Pit_sharing_between_weapons

aye, coming with no references. weapons pits do indeed last at least a century from a 2006 NPR report corroborated by Lawrence Livermore Labs and last at least 150 years from a later LLNL report.

[Rakaydos]

Enriched Uranium 235 has a half life of 703,800,000 years. In that many years, half of your materiel will have decayed naturally into lighter elements.

A uranium reactor, I would think, would last quite a few years before a significant drop in reactivity... though that might be reduced by having a critical reaction going on.

[Nuke]

a bomb pit will be kept subcritical while in storage. so there is not a whole lot of reactivity going on there. but the story is different when you have nuclear fuel in a reactor, where the fuel is kept critical for long periods of time. poisons will build up and eventually render the fuel useless. thats why most reactors need to be serviced every 10 or so years. you can use a breeder or use online reprocessing to get around that problem. thats one of the good attributes of molten salt reactors, since the fuel is liquid you can reprocess it while the reactor is running.

[jwenting]

Enriched Uranium 235 has a half life of 703,800,000 years. In that many years, half of your materiel will have decayed naturally into lighter elements.

A uranium reactor, I would think, would last quite a few years before a significant drop in reactivity... though that might be reduced by having a critical reaction going on.

a nuclear weapon however requires a rather more pure fission mass. Even after several decades it's become unreliable enough there's a good chance it won't go BOOM when you pull the trigger.

[DarkStar64]

ever heard of the orion projected? it's relatively reasonable price wise and could reach a speed of 3.3% of the speed of light in just 10 days. it's been possible since the fifties. there are newer even better and more efficient versions based on the same principle which are not far of from being possible.

yes I have, but were not allowed to use nukes in space.

[Red Iron Crown]

yes I have, but were not allowed to use nukes in space.

If it meant going to another star in a reasonable time frame, any rule of that sort would be quickly amended.

[shynung]

ever heard of the orion projected? it's relatively reasonable price wise and could reach a speed of 3.3% of the speed of light in just 10 days. it's been possible since the fifties. there are newer even better and more efficient versions based on the same principle which are not far of from being possible.

I propose upgrading the Orion drive to fusion fuels.

[Rakaydos]

I propose upgrading the Orion drive to fusion fuels.

Isnt that called Project Daedalus?

[shynung]

Isnt that called Project Daedalus?

Project Daedalus was dealing with a complete spacecraft. I think the specific technology (which Daedalus planned to use as well) is inertial confinement fusion drive.

We have to develop fusion first, obviously, but I'm confident we will have it before 2100.

[KASASpace]

Heck no!

For one thing politics will kill it instantly.

But tech wise, no. Perhaps not until we develop cryogenics to a point where humans can last many lifetimes.

Now if you want to go generational, maybe..... maybe not...... not

Of course we would need either a fusion drive or antimatter drive. Perhaps Orion NPP?

Honestly, I think not. But we do need to go interplanetary.

[KASASpace]

Isnt that called Project Daedalus?

No, it would be using a pulsed explosion from a nuclear fusion bomb, not continuous laser initiated fusion.

[shynung]

Heck no!

For one thing politics will kill it instantly.

But tech wise, no. Perhaps not until we develop cryogenics to a point where humans can last many lifetimes.

Now if you want to go generational, maybe..... maybe not...... not

Of course we would need either a fusion drive or antimatter drive. Perhaps Orion NPP?

Honestly, I think not. But we do need to go interplanetary.

We must. There isn't enough resources on any planet that could run any civilization indefinitely, even with extensive recycling and conservative energy mining. Even the sun will die out some billions of years into the future, rendering the Solar system barren.

On fusion tech, if we were to research power generation reactors, we may be able to get more leeway. If so, things like VASIMR or other kinds of high-energy electric propulsion would be the order of the day.

Plus, with enough relativistic speeds, time dilation effects will kick in. Even normal humans can live for thousands of years if living in a spacecraft travelling fast enough. This kind of speeds is the problem where Orion, fusion drive, or any other drives try to tackle.

[Mitchz95]

Maybe with a tiny scientific probe. Manned missions should wait until we have the technology to make the trip in no more than fifty years.

[KASASpace]

We must. There isn't enough resources on any planet that could run any civilization indefinitely, even with extensive recycling and conservative energy mining. Even the sun will die out some billions of years into the future, rendering the Solar system barren.

On fusion tech, if we were to research power generation reactors, we may be able to get more leeway. If so, things like VASIMR or other kinds of high-energy electric propulsion would be the order of the day.

Plus, with enough relativistic speeds, time dilation effects will kick in. Even normal humans can live for thousands of years if living in a spacecraft travelling fast enough. This kind of speeds is the problem where Orion, fusion drive, or any other drives try to tackle.

Yes, we must, but not now. With a government like this! the UN is horrible at what it does, as people still die and people are still ignored.

Fusion rockets are really far away, and VASIMR just doesn't have the Isp for sufficient fractions of light speed.

That's NEAR the speed of light, not one tenth.

[shynung]

Yes, we must, but not now. With a government like this! the UN is horrible at what it does, as people still die and people are still ignored.

Fusion rockets are really far away, and VASIMR just doesn't have the Isp for sufficient fractions of light speed.

That's NEAR the speed of light, not one tenth.

The UN's existence clings to the fact that powerful countries make up the bulk of its capacity. Considering the social problems typical in modern society, even if the UN were to succeed, there would still be sociopolitical problems. But I digress.

Right now, we still have to research things like fusion and antimatter power. Considering it's still in its infancy, it would still take quite a while before the first fusion drives are flown. Most likely, we would not be around to witness it.

Yes, I did mean near-light-speed. It might sound like a quantum leap, but we'll get there eventually. Let's hope some disgruntled army general didn't start an apocalyptic war in the middle of the progress, and reduce everyone back to the dark ages.

[Pigbear]

I think the real problem here is not speeding up but slowing down.

[Seret]

I think the real problem here is not speeding up but slowing down.

Is there a difference?

[SargeRho]

Yes. It takes an absurd ammount of fuel to accelerate to relativistic speeds, something in the order of 95-99% of the ship's mass will be fuel. As a consequence, it takes a lot of fuel to decellerate. So there are only two ways to solve this, well, three actually. You can make the trip take centuries or millenia, you can get rid of the fuel for part of the accelleration or decelleration by using some form of sail, be it solar, magnetic or a photon sail, or you can use antimatter engines, which might allow you to get to a significant fraction (let's say 10%?) of the speed of light, and back down.

Of the three, the sail solution is likely the most viable.