Interstellar travel; possible or not?

Great Debates
81

If only, if only, if only there was something we could do in low earth orbit that made money! Some “killer app” onlong the lines of, oh, microgravity materials processing.[sub]1[/sub] If there was only something we could do that would show a return now, even at $6000. a pound, and would earn even more if the investment was made in economies of scale to lower the cost. The research money would be there, people would try 20 different schemes and the 3 or 4 that worked would be implemented, and the whole wonderful synergy of the free market would work it’s magic.

Do you know why we now finally have good quality flat screen video? It’s not because someone said “Let’s invest a billion dollars over thirty years and eventually we’ll get it to work”. No, it’s because laptops created a market for flat sceens. Even those low-res monochrome things would sell. And created a demand for a better lap top screen. And so on.

Was it Quark the Ferengi who said something like: “We didn’t go into space for conquest, or scientific knowledge, or to learn about other cultures; we did it for the pure and unadulterated love of profit itself.”?

(1). Wouldn’t it be ironic if it turned out that the secret to making practical nanofiber cable- necessary for a “space elevator”- was that it had to be grown in microgravity?

82

The problem with talking about wormholes, space warps, hibernation, and all these other science-fiction concepts is that they are a total distraction from the topic. We don’t know if any of it is possible, or if it is what we’d have to do to make it work.

This isn’t a science fiction thread. Let’s leave teleporters and antimatter out of it. This is supposed to be a serious discussion of plausible ways we might advance in space in the near term (say, within our lifetimes). So Bussard ramjets, solar sails, nuclear ion drives, and other technologies are fine. Travelling by wormhole is not.

Let’s try to keep the discussion within the realm of the plausible.

83

Originally posted by ** il Topo **

Well, the specific example I was discussing was two volunteers and a box of eggs and sperm. Now, I’m pretty sure that gametes don’t legally qualify for “informed consent.” Second generation colonists don’t either, but they can’t say no.

The thing is, the frozen embryo solution given by several others is all about imposing a set of choices upon unknown human beings which will entirely dominate any possible life choice they might wish to have had. It’s fundamentally dictatorial, on a scale no earth bound despot ever dreamed of. Hitler was a democrat, by comparison, and a darned liberal one, at that.

And, we will undoubtedly have to include educational materials for the teaching machines. We better make sure they include a lot of very strongly patriotic themes about duty, and the benefits which our intrepid explorers have provided for all their ancestors, and their much more comfortable cousins back home. We probably should make sure there are no references to human rights. Don’t want to give these tools of our utopian dream any counterproductive ideas.

The fact is the dream of space travel in generation ships is a really ugly reality, if you are not one of the true believers, and find yourself on the ship. You can’t have a revolution. There is no turning back. The only option you have, should you decide that you are unwilling to spend your entire lifetime fulfilling the dreams of someone you will never know, and can never meet, is to dedicate your life to destroying that dream, out of vengeance.

I think it would be the most likely eventual outcome. I am not convinced I wouldn’t be throwing monkey wrenches myself, if I were in the same position. So remember, engineering failure is not your only concern, and a hundred years is a long time for a patient man, with a sense of mission.

Tris

84

“‘better’ is the enemy of the good enough” some guy

Solar powered rail gun to the stars. No need for reactors as the capacitors will suffice. And even if they don’t then you use the reactors. The longer the gun the faster you go. Length…well there’s not that much to get in the way of the damn thing is there?

Ok, so we need something to shield us from nasty stuff….layered structure of ceramics, lead and water maybe? You could use the water to cycle past the ships reactor to keep it cool, might as well use it to slow some stuff down.

So how do you slow down? Mag sail. You hit the heliosphere of the target star (or earlier); open it up drag yourself down to a slow enough speed to deploy the nuclear thermal rocket. Start colony, build rail guy. Rinse and repeat.

Oh and insert random “technological advance” into all the gaping holes! :slight_smile:

85

Except for the fact that the feasibility of Bussard ramjets has been all but totally disproven. Even if you could build a scoop the size of Mars (!) to gather all the hydrogen you needed, the drag caused by ramming into the interstellar medium with such a monstrosity would exceed the amount of thrust your engines could produce, even assuming you could achieve effortless nuclear fusion of every atom of captured hydrogen and convert it into thrust with 100% efficiency!

Oh – and nuclear fusion with plain old garden variety hydrogen ain’t gonna be easy to begin with. The fusion reactors we’re working on right now use a mixture of deuterium and tritium. Deuterium is nonradioactive but only accounts for 1 in every 6000 hydrogen atoms encountered in nature. Tritium is, like, super-rare, and is radioactive with a half-life on the order of 12 years. You can forget about scooping up tritium in a Bussard ram, and unless you’re going to go through and separate out that one atom of deuterium from the 5999 atoms of regular hydrogen that came along with it for the ride, you can forget about scooping up deuterium in any useful quantity with a Bussard ram too.

86

Well yeah but which is more realistic? The buildable scoop that wont go anywhere or the super-duper spacetime bending “warp” core ship?

How about feasible as a criteria?

87

Um, just how much drag can a magnetic sail create? Could the heliosphere of our sun, for example, confer enough drag on a practical magnetic sail to slow it down from a maddening 1% of the speed of light (3,000,000 meters per second) to a nice, comfy 10,000 meters per second or so?

88

The first is, of course, more realistic, but only because some doofus might be nutty enough to actually build one. (Assuming he can gather enough material in Earth orbit to build a scoop that’s bigger around than the moon. :wink: )

Personally, I’d put my money on the Orion design, or the ion propulsion NASA tested in the Deep Space 1 space probe, or maaaaaybe the Daedalus if we ever got our controlled fusion act together.

89

Harry Harrison wrote a science fiction novel something along those lines called Captive Universe. On the other hand, one scenario I’ve seen for interstellar travel by generation ship would be to have the generation ships start out as space colonies. The first step–admittedly a doozy–would be for us to get beyond our current primitive little orbiting tin can collections to genuine space stations and space habitats, maybe at the L5 and L4 points of the Earth-Moon system. Once that happens, the space colonists could move on to the Asteroid Belt, becoming the fabled “asteroid miners”. From the Asteroid Belt, over the generations the space colonies could move out by easy stages into the regions around the Outer Planets, on to the Kuiper Belt, and out into the Oort Cloud. The Oort Cloud probably extends halfway to the nearest star–for a nomadic space colony making the long hops from comet to comet to replenish its supply of volatile elements, the decision to head on out into interstellar space wouldn’t really be that big a leap; and over the many generations since the original colonists left Earth orbit, ties to Earth and the rest of the Solar System would have become very tenuous anyway.

90

Jeez… Science as we currently understand it supports Warp Drive moreso than it supports the uber scoop… If you had the slighest clue about the mechanics behind the concept you wouldn’t be so easy to dismiss it as pure fancy. Antimatter, fusion, both are possible within our lifetimes. Well… At least my lifetime. Antimatter is being experimented with as we speak, albeit less publicly known, but it is being toyed with. Fusion, will probably be a reality within 25 years. I highly doubt that we won’t have Fusion by the year 2050 at the latest…

The ion propulsion system was a POS, it died out…, and the drive capacity even though was significantly better than chemical rockets, was still no where close to the amount produced by nuclear powered rockets.

Fusion all the way. Fission is the way of the past. We need to advance to fusion. Fusion will open up a ton of new possibilities…
I agree though. We need to find a reason to be in space besides for pure exploration. Economics drive the human race, therefore, we need to find an economical reason to be out there, whether it be mining for gasses, or growing perfect computer chips, we need to be doing something productive. I’ve said it before, what fun is studying ants and spiders?

91

What you want numbers! :slight_smile:

Snipped some stuff, and here’s a part of the abstract

I get dinged for this but not the solar powered rail gun. :smiley:

92

Physics says it may be possible assuming you can find negative energy matter, or some such

We can scrap a microgram of antimatter together for a few moments. Fusion has been dangling out there at the 50 year mark for …50 years now.

Fission isn’t even a now thing in space travel. That’s like saying “super sonic” speed is sooo 20th century, hypersonics are the way to go.

My point was, and I think Sam’s point too, discussing how we might do it when we get magical technology defeats the quest. We will wind up continually waiting for the better technologies to arrive. While the scoop may not work, we could potentially build it; the space warping stuff is not even on the boards

93

this seems like a good place to pose my problem with star trek’s notion of faster-than-the-speed-of-light travel. gravity propagates at the speed you would expect it to: c. assuming we have this nice little warp or wormhole, sure we can exceed c once we start moving through it, but we can’t “pull” distant space closer to us at a rate faster than c. so how is that faster than c?

maybe there could be a warpzone! where the space is already bent…

i have to agree with polycarp, that it is just a mathematical impossibility (according to special relativity) that we accelerate to c. as a result, there is no physics for what happens when c is exceeded. if there was a way to make a jump beyond c, without accelerating to c, there is no way to know what would happen.

94

Okay, so let’s think about a timetable for a realistic, minimum time it would take before we would reasonably launch an interstellar probe:

  1. The Terrestrial Planet Finder telescope discovers a terrestrial planet in a habitable zone of a nearby star. The atmosphere tests positive for biomarkers, and appears to have an thick, possibly breathable atmosphere. Some time around 2015 at the earliest.

  2. Work is sped up on a large planet imaging array. By 2020 we can map the continents of the planet.

  3. Around this time, extensive efforts would be underway to listen in for signs of intelligence, and to beam signals there.

So here we are in 2020. There’s a planet 4.3 light years away, with an active biosphere. What’s the next step? How do we get there, with what, and how long will it take?

My guess is that the first mission wouldn’t be sent for at least 10 or 20 years, and it wouldn’t be very ambitious. Perhaps a robotic probe with a travel time of 200 years or something. It could be justified by science measurements of the Oort cloud along the way.

Or would we keep waiting for faster ships? That’s always the old condundrum - why launch a probe that would take 200 years, if you think you could wait 100 years and launch a much better probe that only took fifty? And why launch then, when in forty years you can have one that can make the trip in five?

Does that sort of logic doom us from ever launching an interstellar probe until we can hit a significant fraction of C? Even if we pick up intelligent signals from nearby?

95

I think I can get onboard for Sam’s timeline. I am a bit more pessimistic about it, in some ways, though.

I think we can have a great telescope by 1015. I think that we could have continental imaging at two parsecs by 2050. But I really don’t think we are going to find bio probable planets at 4.3, or even six light years. But I will go along for the ride.

So, 2050, we could easily have regular commercial interests in Earth Orbit, and the beginnings of actual facilities on the moon, for scientific purposes. So, we find out that there is a plum planet for exploring just next door, galactic neighborhood wise. Now what?

We are probably best served in the race to space if there turns out to be a large number of small dirty ice balls in the TNO region, and the biological sciences come up with a financially useful thing to do with the odd organics among those objects. Even without that serendipity, we will almost surely be sending probes to the Heliopause fairly often, say once a decade or so. So, expanding such a probe program to include extra mass is doable. All that extra mass has to be starship stuff. And we had better be working on the Trans Neptune Robotic Station, at the same time. I figure robotics is gonna be our real key. Humans are just too expensive to maintain in space.

So, we send the regular probes in orbits that end at TNRS1, depositing their reusable elements, and heading back to Earth with their ice balls, and data recordings. The special probe elements are sent to TNRS1 as late as possible, after an entire superstructure, is assembled and tested. Then we start keeping ice balls for reaction mass, and sending fuel. Given a twenty year long program, we could launch our robotic probe from TNRS1 by 2075. Given a good slingshot off the outer planets, and a few expectable improvements in rocket science, we could expect that .1c figure to be completely doable. Forty five years plus or minus months. Our probe could arrive by 2120.

It’s going to have to be able to spend a long time surveying, before it tries anything even close to landing a probe of its own. It is also going to be going through a lot of chance windows. Missing any one of them means starting over. No ways to know what went wrong, it just never sends us back anything else. (Sound familiar?)

So, some time around 2125 we start getting data feed from the robot Starship Dora Heinlein. Intense laser feeding into our newly constructed whole earth orbit receiver array. Pretty good bit rate, and only triple redundancy necessary. (There ain’t no “pardon me, what was that?”)

Hey, guess what? Little green men! And boy, are they pissed about the so called soft landing probe!

Tris

96

This link gives a short description of most ideas mentioned so far

http://www.grc.nasa.gov/WWW/PAO/html/warp/ideachev.htm

“Here’s the premise behind the Alcubierre “warp drive”: Although Special Relativity forbids objects to move faster than light within spacetime, it is unknown how fast spacetime itself can move.”

maybe there could be a warpzone! where the space is already bent…

i have to agree with polycarp, that it is just a mathematical impossibility (according to special relativity) that we accelerate to c. as a result, there is no physics for what happens when c is exceeded. if there was a way to make a jump beyond c, without accelerating to c, there is no way to know what would happen. **
[/QUOTE]

97

CHAOSGOD: I endorse the last part of your #2 wholeheartedly. Like I said–They are choosing not to contact us–yet!

As for the rest…

“The speed of light? We’ll just go around it!” Tom said evasively.

98

That’s right, and in much the same way there are no maps to tell us what the land masses to the north of the north pole look like.

99

Why are so many people in this thread so bloody impatient when it comes to star travel?

I don’t mean impatient in the sense of “let’s not wait until we start going to the stars”, I mean impatient in the sense of “once we take off for another star it had damn well better not take more than a couple of years to get there!”

Geez! It sounds like a bunch of little impatient kids pestering the drier with “Are we there yet? Are we there yet? Are we there yet? Are we there yet?”

If you’re going to send out frozen embryos or people in suspended animation, what does it matter whether the trip takes 5 years or 50 years or 50,000 years? We’ll get there when we get there, and not a minute sooner, young man!

100

Maybe it’s because we want to get there before we are dead. Some scenarios (albeit improbable) seem to land us at Proxima Centauri in just a few years. Maybe even less from the perspective of the astronauts due to relativistic effect.
6.27 years if travelling at 0.5 c
I’m sure there’s a billion volunteers to make the trip, even if it is one way. Hell, there’s a thread in the dope-boards in which people claimed they’d like to go on the shuttle even if they knew it was doomed.

Actually, proxima centauri is not as interesting as the other two stars which form the system only “inches” away, which are much more similar to the sun and may even harbour life bearing planets.

peace