Interstellar Travel

Mar25-03, 01:53 PM

(read *lost* in general discussion- thought itd be better if i posted this again here)

interstellar travel. i wanted to know the possibility of it actually being able to happen. iv got coursework to do, and it can be on anything we want it to be on, as long as its got summat to do with physics. so i chose interstellar travel, kinda wish i hadnt now, cos im not sure where im going with the whole thing- iv started talking about the problems involved, such as speed, propulsion and energy, but thats as far as i got.
i dont really know where to go from there

i did get some replies but it was waay to advanced for me to understand- im sure i will after doing the coursework, but i just need the basics to get me going.

ooh- and any ideas about wormhole, space time distortion and warp drives would also be useful.... :)

if anyone has any ideas of how to tackle this- ur help would be much appreciated :)

thanx

TA x x

**LURCH** · Mar25-03, 04:51 PM

Oh yea, that was what you'd asked about!

Regarding "warp drives"; it has been stated by the leading researchers in that field that "any realistic sceem for FTL (Faster Than Light) travel would have to involve negative energy." The laws regarding the existence of negative energy make superluminal travel pretty unlikely.

You might want to look into a phenominon known as quantum entanglement. This strange property of QM causes an event in one place to have an appearent effect in another place without travelling through the intervening space. So the effect is instantanious, no matter how far away. This does not violate relativity because the signal does not travel, it simply "is there". This brings up the possability of "Quantum Teleportation" (if you can get a signal there instantly, maybe you could send a person the same way).

**CJames** · Mar25-03, 05:23 PM

A Lurch said, superluminal travel is unlikely. However, it isn't required in order to accomplish intersteller travel. We can reach the nearest star in a minimum of 4 earth years. However, if you understand special relativity, it becomes clear that even though from a "grounded" person's perspective it could take thousands of years for somebody to cross the galaxy, such a journey could be accomplished within a lifetime aboard the spaceship itself, due to the twin "paradox" and time dilation.

**J-Man** · Mar26-03, 01:24 PM

Interstellar Travel Considerations:

1) Space is big, really, really, really big. Let me try to put it into perspective...

from http://www.grc.nasa.gov/WWW/PAO/html/warp/scales.htm
Interstellar distances are so astronomical (pun intended) that it is difficult to convey this expanse. Consider the following analogy: If the sun were the size of a typical, 1/2 inch diameter marble, the distance from the sun to the Earth, called an "Astronomical Unit (AU)" would be about 4 feet, the Earth would be barely thicker than a sheet of paper, and the orbit of the Moon would be about a 1/4 inch in diameter. On this scale, the closest neighboring star is about 210 miles away.

Another example is light. It takes light about 8 minutes to get to the earth from the sun. From the closest star, light takes over 4 years to get to earth. How fast does light travel? Well, sit in a dark room, turn on the light switch and start counting. I'll bet you didn't even get to "..." before you see the light. And "..." is a much shorter time than counting to "one".

2) Time. It should be intuitive that the faster you travel, the quicker you get there. But we are currently restricted on the velocity we can achive, much less than the universal speed limit of speed-of-light. Look at these examples of how long it would take to get to the Centauri stars at various speeds, from the same site listed above:

At 55 miles-per-hour for example, it would take over 50 million years to get there.

At a more typical spacecraft speed, for example the 3-day trip time that it took the Apollo spacecraft to reach the moon, it would still take over 900 thousand years

And even if we consider the staggering speed of 37-thousand miles-per-hour, which was the speed of the NASA Voyager spacecraft as it left our solar system years ago, the trip would still take 80,000 years.

Even if we achieve 100 times the speed of Voyager, it would still take 800 years, and keep in mind this is to the closest star system. That means, we would either have to have about 40 generations of humans living on the craft before they arrived, or we would have to go faster than light, theoretically impossible.

3) Propulsion. All of our current propulsion systems utilize Newton's third law of action-reaction. That means in order to accelerate, we have to push some mass in the opposite direction. The more we want to accelerate the more mass we have to push out of the spacecraft, pushing it out faster helps. But this means that we have to carry extra fuel (mass) which means we have to push even more out just to accelerate the craft with all this extra fuel mass.
Here is a graphic of how much of 4 types of propellant are needed to send a school-bus sized craft to the nearest star, allowing 900 years to get there.

Things get even worse if you accually want to stop once you get there because you need almost as much propellent to slow down. Almost as much, because you already threw away a lot of mass accelerating. actually it is much less, but in this context, "much less" still means quite a lot.

4) Energy. (quote from same source)

Even if we had a nonrocket space drive that could convert energy directly into motion without propellant, it would still require a lot of energy. Sending a Shuttle-sized vehicle on a 50 year one-way trip to visit our nearest neighboring star (subrelativistic speed) would take over 7 x 10^19 Joules of energy. This is roughly the same amount of energy that the Space Shuttle’s engines would use if they ran continuously for the same duration of 50 years. To overcome this difficulty, we need either a breakthrough where we can take advantage of the energy in the space vacuum, a breakthrough in energy production physics, or a breakthrough where the laws of kinetic energy don’t apply.

This page: http://www.grc.nasa.gov/WWW/PAO/html/warp/ideachev.htm
(another part of what I've been quoting) has some basic information on:
-Worm Hole transportation
-Alcubierre’s "Warp Drive"
-Negative mass propulsion
-Millis’s hypothetical "Space Drives"

(edit: fixed a misspelling, there may be more.)

**MrCaN** · Mar26-03, 01:53 PM

If your gonna write a paper on it, here is a simple thing to think about, once your in space, you can accelerate to extremely high speeds, like DS1 did, but with humans on board you would have to accelerate at a slower rate, but interstellar you would have time, the second thing to think about, is that if you want to stop somewere, you have to deaccelerate at the same rate as before.

**LURCH** · Mar26-03, 03:46 PM

"7x10¹⁹ Joules"; does anyone here know how much mass that would take (per e=mc²)? That is how much a matter-antimatter drive would require.

**Zefram** · Mar26-03, 04:17 PM

That's equivalent to about 778 kg, I believe.

selfAdjoint · Mar26-03, 05:45 PM

Yes, that is the mass requirement for the energy, but the limiting factor with realistic propulsion systems is reaction mass.

Look up the rocket equation and figure out how much reaction mass you would need, with no constraint on energy, to reach, say .1 c, .25c, or .5 c. This is the doom of rocket propelled star travel.

Photon rockets are a possiblility, but their acceleration is so low they are not practical for trips in a human lifetime. Ramjets have been shown not to work; "They make better brakes than drives", and wormholes and warp drives will remain science fiction until someone figures out how to create negative energy by the -tonne.

**g8or** · Mar28-03, 02:46 PM

In the 1970's the British Planetary Society wrote up a rather detailed study called Project Daedalus powered by lasers zapping pellets of deuterium causing small thermonuclear explosions resulting in a hot plasma which was used for thrust in an interstellar vehicle. I can't recall details but I think after about a year of thrusting?! a speed of 0.12 c was postulated.
Anyway,several years later I heard that some physics labs were hitting deuterium pellets with so and so many gigawatts or terawatts from experimental lasers, but what happened thereafter I haven't heard.Maybe it's classified,dunno.Has anyone heard anything recently about those experiments and anything recently about Daedalus?

Mar28-03, 06:12 PM

wow..thanx ppl! *hugs*
gives me summat to think about- shall have to read it all again make sure i know what im doing.

thanx for the ideas! :)

Luv TA x x

Apr7-03, 05:25 PM

how do wormholes actually work? iv read some info on the net, and they kinda contradict each other..

thanx :)

**spacemanspiff** · Apr7-03, 10:43 PM

isn't using wormholes dependent on acessing higher level dimensions than the 3 or so we currently use?

so the earth and pluto are far away in a 3d model but if we look at dimension N they are close together.

is that right?

Apr8-03, 06:49 AM

yeah, thats something to do with it...
but i just dont get the principle of it, like how they come about, ive read that black hole and white holes can be considered as the entrance of one,

A beam of light traversing a path between two points in curved space-time can take longer to complete the journey than a hypothetical spaceship taking advantage of a wormhole’s shortcut connection between the two distinct regions of space-time.

Although they may seem more the stuff of science fiction than science fact, physicists first dreamed up the idea of wormholes. In 1935, Albert Einstein and Nathan Rosen realized that general relativity allows the existence of “bridges,” originally called Einstein-Rosen bridges but now known as wormholes. These space-time tubes act as shortcuts connecting distant regions of space-time. By journeying through a wormhole, you could travel between the two regions faster than a beam of light would be able to if it moved through normal space-time. As with any mode of faster-than-light travel, wormholes offer the possibility of time travel.

is this just the basic stuff?

**J-Man** · Apr9-03, 12:22 AM

Twisted Angel quoted:
"In 1935, Albert Einstein and Nathan Rosen realized that general relativity allows the existence of “bridges,” originally called Einstein-Rosen bridges but now known as wormholes. These space-time tubes act as shortcuts connecting distant regions of space-time."

Keep in mind that just because general relativity allows the existence of wormholes, doesn't mean that they in fact exist. Nobody has ever seen evidence of a wormhole, unless I'm not up-to-date. General Relativity is still only a theory, albiet the best one we have at the moment, so there could be problems with it. Much in the same way that Newton's equations had to be modified by Einstein/Lorentz in the first place.

interstellar travel. i wanted to know the possibility of it actually being able to happen

The fact is nobody really knows if wormholes exist and even if we do find evidence of one, it is unlikely that we'd be able to utilize a wormhole to travel and stay alive at the same time.
That does not make interstellar travel impossible though as pointed out earlier. We can already do it if we want to; it would just take a really, really long time and a great big amount of energy.

is this just the basic stuff?

Yes, I'd use no more than that second quote (that I started to repeat above) in your paper other than mentioning that wormholes offer 'interesting possibilites', but not without some major scientific breakthroughs and a lot of time.

Apr9-03, 05:13 AM

Hello,
The other day I watched Event Horizon. Is there any grounds for developing an engine such as the ship the Event Horizon used? Pretty much it created and contained a small singularity that when used would bend time and space and fit 2 points into 1. Thus you could travel through a "worm hole" and arrive at your destination within minutes. Sure, this would require vast amounts of energy. But is there any grounds for that type of engine or theory? Anyone know what I'm talking about? Here's the example they gave in the movie. Take a sheet of paper, mark a dot on either side, then fold the paper. The paper represents the plane of space. One dot represents yor current location, the other dot's your destination. Folding the paper would bring both dots together and the worm hole would act as your passage to the second dot/location.
Or is this all just Hollywood BS?

**russ_watters** · Apr9-03, 09:48 AM

Originally posted by MrCaN
If your gonna write a paper on it, here is a simple thing to think about, once your in space, you can accelerate to extremely high speeds, like DS1 did, but with humans on board you would have to accelerate at a slower rate.

Isn't DS1 the ion powered probe? Ion engines are currently extremely low thrust but extremely long endurance. Currently they provide thrust on the order of a few ounces of force at most. Also, speed builds up faster than you think it does. At 1 G of acceleration you reach orbital velocity (17,500 mph) in 14 minutes. If it were possible to get a craft up to half the speed of light with an action/reaction engine (it isn't), it would take only 6 months at that acceleration. So having to slow the acceleration isn't an issue.

This is all of course why unless there is a radical change in propulsion technology (warp drive) it won't ever be possible for humans to even reach the nearest star.