Your ideal Interstellar vehicle/system (no FTL)

[jfull]

Lets suppose that, a few centuries from now, humanity has a need or desire to send a significant number of craft to other stars. Unfortunately warp drive and other FTL concepts are either still beyond our technology or have been proven to be outright impossible.

In this scenario, what kind of propulsion technology would you use and what kind of craft would you build?

I would imagine that at that point we might have many giant solar arrays orbiting the sun and beaming power back to Earth. However, they could also beam their power to giant laser stations of some kind. My craft would have solar sails and be pushed as far as possible by intense laser beams. When the beam no longer becomes effective, it would jetison the sail and use pulsed nuclear propulsion to continue accelerating.

By using a sail, it could avoid having to carry quite a lot of reaction mass for propulsion.

Even further in the future, I think it would be ideal to use small singularities for propulsion (yes that's a valid propulsion method, as a small singularity will radiate away all its mass)

Edited March 16, 2014 by jfull

[SargeRho]

Nuclear fusion pulse propulsion (Z-Pinch or Electron Beam Confinement), coupled with magnetic sails at first. These ships are used as first-wave colony ships. At the destination, some of the ships enter a low orbit around the target star, and being constructing particle beam emitter stations, that will emit particle beams for future ships to break on. Due to the absence of such beam stations, the initial colony ships would be slower than the ships that come later.

Once the beam emitters are all up and running, future ships won't be carrying their own interstellar engines. Instead, they carry only magnetic sails and small fusion engines for in-system travel. Since they have a beam to brake on, they are also accelerated to greater speeds than the colony ships before them, reducing the travel time significantly. The magnetic sails are also used as interstellar parachutes, more so by colony ships than by the regulars that come later.

The colony ships in turn, are sleeper ships. They carry a few hundred people, and thousands of frozen embryos, and all the equipment needed to build a colony (in the first wave) and additional supplies (later on). They might even carry fusion or fission-powered SSTO space planes, instead of blunt capsule landers, that go back and forth between the ships. The much greater mass of such a plane might be justified by not needing as many landers.

Shameless self-advertisement ahead:

Further into the future, we might develop antimatter engines and, more importantly, a way to produce antimatter in sufficient quantities. That would open up high relativistic speeds (In exess of 50% of the speed of light).

Edited March 16, 2014 by SargeRho

[Rakaydos]

Fusion pinch with a magnetic ramscoop. A torroidal spacecraft that is sped up to a high velocity by electron-beamed magsails, it protects it's crew from ionizing radiation with a magnetic field. This magnetic field pinches interstellar hydrogen plasma through the center of the torus, where pinch fusion is induced, pushing the vessel faster through space.

[Dispatcher]

Ideal? Antimatter. The problems are production and containment. If those are overcome, it will be very efficient.

[meve12]

Ideal? Antimatter. The problems are production and containment. If those are overcome, it will be very efficient.

This. Specifically, Antimatter RAIR, for scouting missions.

For trips between civilized worlds, a beamrider will do.

[jfull]

I have some doubts about whether antimatter will ever be feasible to produce and contain

[Sillychris]

I also choose antimatter. The ISP would be outright absurd.

[Force21]

We can already contain a couple hundred atoms of antimatter in an electro-magnetic sphere in a vacuum chamber. Not for very long, just enough to prepare for tests, like a recent one in which scientists released the nano sized glob of anti-atoms from it's confinement. After about a second, a small explosion was heard like a firecracker, and thus we learned that the antimatter moved out of where it was contained... That's about it... Nobody knows much about the stuff, but what we know for certain is that it's ~100 times more explosive than a hydrogen bomb in relative size of reactant. So yes, if we can contain and produce massive quantities of the stuff, bombs will be made Oh yeah and rocket fuel

[meve12]

Another thing: Why carry the planes along? Drop the colonists on reentry pods, and let them build the planes for the next ship once they've bootstrapped to the required infrastructure.

[jfull]

Another thing: Why carry the planes along? Drop the colonists on reentry pods, and let them build the planes for the next ship once they've bootstrapped to the required infrastructure.

Well, if something goes wrong before they've established infrastructure, they may need some way to get back into orbit, or simply relocate to a different location on the surface.

[palioxis1248]

Proton decay rockets, if they're at all possible. Closest thing to a mass-converter we'll ever have.

[SargeRho]

Another thing: Why carry the planes along? Drop the colonists on reentry pods, and let them build the planes for the next ship once they've bootstrapped to the required infrastructure.

Because SSTOs can return to the ship, and fly around on the planet. A pod can't do that so easily. If your SSTOs are fusion powered, you'll be able to refuel them near the ocean/sea, since you'll want to build your colony near running water. And you can extract deuterium from water. If the planet in question has a long biological history, you can have LNG powered SSTOs. If your goal is to shave mass off, go with SSTO shuttles.

Edited March 16, 2014 by SargeRho

[cantab]

Early exploration: Nuclear pulse propulsion. It's the nearest to being feasible, and for a first expedition I would want to be self-sufficient. If you're relying on beamed power, what if Earth by mishap or choice switches off the beam?

Medium stage: A high Isp decent thrust electric propulsion system, powered by beamed power and fusion reactors. By this time things will be more established, the beams will be considered reliable and synergise well with the reactors; likely beams for when you're near a settled system and fusion for deep space.

Late stage: Antimatter, powering anything. Best energy-to-mass ratio you can get. By this point ships will be capable of 1 g accelerations for months or even years on end, which gets them up to a good fraction of light-speed. The nearest stars remain too far away for holidaying, but emigration becomes feasible.

Don't forget that along with these developments, we'll probably extend our lifespan. A 50 year journey becomes reasonable when you expect to live for a thousand years.

[*Aqua*]

Don't forget that along with these developments, we'll probably extend our lifespan. A 50 year journey becomes reasonable when you expect to live for a thousand years.

That's a good point. I believe in one or two hundred years is will be quite normal to have cyberimplants in our bodies. If it's possible to transfer a human mind into a computer we'll be almost immortal. Then traveling for a thousand years to the next star isn't a problem anymore.

So I choose ion drives powered by fusion reactors. Ion drives are save. They do not tend to self-destruct on a wimp and even today they are robust enough to work for months. Continuously. Which other engine can do this?

Fusion reactors needs maintenance every few years, so a ship needs several of them. They provide enough power to boost the thrust of the ion drives to reasonable levels and they seem to be safe enough - behind a lead plate. Unfortunately they are quite complicated. The more complicated things get the easier they break.

[jfull]

If you can make a fusion reactor, there's no reason not to make a fusion rocket. You wouldn't need to mess around with the ion engines because you'd get much higher velocity plasma directly from the fusion (and thus, better ISP)

[*Aqua*]

I'm not really sure if fusion reactors are the right energy source. Can they work for hundreds or thousands of years? That's what they need to do.

This is the Wendelstein 7-X stellarator. Look at how complex this thing is. If there is a malfunction somewhere you'll need months to disassemble it. I don't think this is acceptable.

For interstellar travel we need something much simpler. I'm not sure what that could be.

Edited March 17, 2014 by *Aqua*
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[78stonewobble]

Well KSP taught me it should have lots of struts. The mass effect series taught me that the reason to go to space is to have physical relationships with aliens, so that rules out uploading ourselves to computers.

Beyond that I'd say something fusion powered, simply because I can't quite see the alternatives working. Matter/antimatter, blackholes, wormholes, stargates, warpdrive and whatever... They would be nice offcourse, but I just don't see them working.

[architeuthis]

Nuclear fusion pulse propulsion (Z-Pinch or Electron Beam Confinement), coupled with magnetic sails at first. These ships are used as first-wave colony ships. At the destination, some of the ships enter a low orbit around the target star, and being constructing particle beam emitter stations, that will emit particle beams for future ships to break on. Due to the absence of such beam stations, the initial colony ships would be slower than the ships that come later.

Once the beam emitters are all up and running, future ships won't be carrying their own interstellar engines. Instead, they carry only magnetic sails and small fusion engines for in-system travel. Since they have a beam to brake on, they are also accelerated to greater speeds than the colony ships before them, reducing the travel time significantly. The magnetic sails are also used as interstellar parachutes, more so by colony ships than by the regulars that come later.

The colony ships in turn, are sleeper ships. They carry a few hundred people, and thousands of frozen embryos, and all the equipment needed to build a colony (in the first wave) and additional supplies (later on). They might even carry fusion or fission-powered SSTO space planes, instead of blunt capsule landers, that go back and forth between the ships. The much greater mass of such a plane might be justified by not needing as many landers.

Further into the future, we might develop antimatter engines and, more importantly, a way to produce antimatter in sufficient quantities. That would open up high relativistic speeds (In exess of 50% of the speed of light).

Sarge Rho, have you read Karl Schroeder's Permanance? You might find it interesting. He describes a slower than light interstellar culture based on brown dwarf way stations and relativistic mag-sail interstellar cyclers. It's pretty awesome. Here is a little essay he wrote about it.

[SargeRho]

I got the inspiration for the magsail beamliners from SMPrichard's artwork called "Beamliner": http://smpritchard.deviantart.com/art/Beamliner-311375994

I'll definitely take a look at that book though.

[xenomorph555]

What I'm thinking is a large orion H bomb propulision system with a large bigelow AG ring and other sections, made up of many Olympus modules and a massive radar. Plus landers/skylons.

[Guest]

First, rule out any pulsed propulsion system with a TWR anywhere near one. Remember, you've got to run it for quite some time, and for that, you need a stable thrust, or thrust low enough the crew doesn't notice the jolt. In the long run, any pulse drive will put unbearable strain on the crew, if only because it'd be really frustrating and unnatural. Save those for asteroid redirection and unmanned flights.

My first choice would be a magnetic confinement fusion drive. Isp about 7 million, near-future (uses basically the same tech as fusion reactors currently in development), constant thrust and an ability to augment it with hydrogen injection into the exhaust (and perhaps also oxygen, for liftoffs). See Discovery and Discovery II NASA concepts.

Later on, antimatter. Regardless of which kind of core you chose, you can easily achieve enormous Isp and decent thrust, making it possible to make a 1G interstellar torchship.

For habitation, the ship should have a centrifuge producing most of the gravity, or, in case of a torchship (even if it doesn't do 1G), just use the engines for this. The crew can't live in 0G. Also, keep in mind to calculate the actual travel time. Depending on how far and how fast you're going, relativistic effects can and will shorten the journey by a lot, so you might just need a ship capable of housing a self-sufficient crew for 10 years or so. No cryosleep needed, just a whole lot of books. IIRC, the minimum self-sustainable population is about 10 000 people. So you've got to take at least that many, or genetically engineer your colonists to remove genetic diseases that make interbreeding dangerous.

Now, the largest cruise ships can carry over 6000 passengers and crew in very comfortable conditions, you could probably live 10 years on one of those. So, a crew centrifuge twice the size of an Oasis-class cruise liner would likely be what you need.

[jfull]

I got the inspiration for the magsail beamliners from SMPrichard's artwork called "Beamliner": http://smpritchard.deviantart.com/art/Beamliner-311375994

I'll definitely take a look at that book though.

oh, I like it

[SargeRho]

Shock absorbers mostly solve the issue with pulsed engines. And with the Daedalus-type fusion pulse engines, you don't feel the pulses anyway, since they occur 250 times a second, and the acceleration is nowhere near 1g.

[KASASpace]

I am so so sorry, but I must say this:

Alcubierre drive.

It actually isn't FTL because you never move faster than light.

I just beat the reasoning.

BUT, in all seriousness, probably either Z-pinch fusion engines or solar sails. Or some combo of the two.

[SargeRho]

It's faster than light in relation to whatever point of refference you choose to pick outside of the warp bubble.