Space travel cannot be fast!

[orionrider]

I keep reading posts about spaceships hurtling 'near the speed of light'... :roll:

Let it be clear, anything real fast is impossible. The reason is plain old physics: Ek = 1/2mv²
The kinetic energy of anything moving is proportional to the square of it's velocity.

Example: a single gram of matter hitting a spacecraft at only 0.3c (100,000km/sec) has a potential energy of 5,000,000,000,000 joules. That is the same energy as 130,000 tons hitting the craft at 1,000 kph. :shock:
Space is not empty. When you begin to speak of significant distances, travel time and velocities, hitting something is almost a certainty.

What about avoiding the impact?
Well, for starters there is no way to detect what's on your path. No laser, radar or fancy sensor works at that kind of velocity on such a small target.
Then the same kinetic energy law says that the energy required to quickly alter the inertia of a speeding spacecraft is impossibly gigantic.

Shields, let's use shields!
Again, the energy required to alter the inertia of even a grain of sand at 0.3c would be incredibly HUGE. Besides, magnetic, gravitational or whatever shields do not exist. Shields may sound familiar, but they are fiction, just like Harry Potter.

Keep it in mind: Space travel cannot be fast, at least not in our newtonian universe.

 

[Space_pioneer]

Make physical dust shields out of Diamond

 

[Solifugae]

It doesn't need to be fast if we can make people live longer or put them to sleep for a 1000 years. That's way off too, but it may not hit up against the same fundamental limits of physics.

 

[orionrider]

Thousand-year trips are not only a possibility, it will be a necessity! Only, no machine can survive for so long without failure. :?

If no exotic physics comes to change the game, we're stuck in the Solar System, period.

 

[csmyth3025]

Thousand-year trips are not only a possibility, it will be a necessity! Only, no machine can survive for so long without failure. :?

If no exotic physics comes to change the game, we're stuck in the Solar System, period.

Hence the concept of generation ships - which are essentially orbiting space colonies on the move. On-going maintenance and repair of the colony's infrastructure would be part of the economy of the colony just as street and utility maintenance is part of a city's economy.

I wouldn't say we're stuck in the solar system forever, but it'll be a long time before we go any place else.

Chris

 

[BenS1985]

Oh, to belittle the possibilities of science.

100 years from now, don't you think that they may have at least one potential solution to the problem you are posing?

 

[csmyth3025]

Oh, to belittle the possibilities of science.

100 years from now, don't you think that they may have at least one potential solution to the problem you are posing?

Orionrider did, in fact, stipulate, "...If no exotic physics comes to change the game, we're stuck in the Solar System, period."

Chris

 

[orionrider]

100 years from now

Some fundamental problems cannot easily be solved in different ways. For instance, after more than 5.000years of progress cars still use wheels. There is just no better way to solve this particular problem and I suspect wheels will be around for many more centuries.

People expect that given sufficient time, Science and progress can beat whatever laws Nature throws at us.
If you can accept that progress will never make things colder than -273°K, then why can't you accept that there is in fact a speed limit? Because it is not convenient?

 

[Space_pioneer]

100 years from now

Some fundamental problems cannot easily be solved in different ways. For instance, after more than 5.000years of progress cars still use wheels. There is just no better way to solve this particular problem and I suspect wheels will be around for many more centuries.

People expect that given sufficient time, Science and progress can beat whatever laws Nature throws at us.
If you can accept that progress will never make things colder than -273°K, then why can't you accept that there is in fact a speed limit? Because it is not convenient?

Because it's all on paper?

 

[MeteorWayne]

No, it's in The Universe.... Duh! :roll:

 

[Mee_n_Mac]

SDC ought to have some kind of knowledge base forum. The point addressed by this thread comes up often enough, as do others. It would be nice not to have to retype or search to find the "answer". Also I'd have to have a bunch of stickies spread across the various forums. SDC needs a place where the mods could stick threads like this to be used as reference material. Debate about the content (if it occurs) could be done in the usual forums.

 

[neilsox]

All good points. Our understanding of the laws of nature has changed. Large changes may, but probably won't, happen in the near future. The cloud of diamond (or other) dust can travel 300,000 kilometers ahead of the space craft unless the spacecraft accelerates. That gives perhaps a minute for the H bomb equivalent energy to dissipate before the space craft flies into the expanding plasma ball (which now contains some decelerated diamond dust) at 1/10 c.
A partial solution is perhaps 100 unmanned spacecraft that travel about 300,000 kilometers ahead of the spacecraft, each with a powerful laser, to vaporize possible particles which might hit the manned spacecraft or one of the 100 unmanned space craft. Laser radar can be used to track the possibly impacting particles (as small as one thousandth of a millimeter) up to a few kilometers away from each of the 100 unmanned space craft. Neil

 

[csmyth3025]

A sensible (hypothetical) near-light speed space ship design can be found in John Walker's C-ship web pages here:
http://www.fourmilab.ch/cship/craft.html. His related pages on near-light speed travel are also very instrucyive.

Chris

 

[ZenGalacticore]

TMK, there is nothing in physics that says we cannot approach the speed of light. From what I've read, 84.6% the speed-of-light is possible within the laws of physics and it is the ideal speed because it would minimize time-dilation and the increase of mass, and be the ideal speed for our distant-future spacecraft, if such speeds could ever be achieved.

But achieving such speeds is not a problem with physics, it's only a problem with our as yet too feeble technology.

And shielding from particles and cosmic radiation, etc? Well, I have faith in the future of materials technology. We won't live to see it, but materials a few atoms thick that are thousands of times stronger than steel or harder than diamond, and thousands of times lighter than steel, are certainly not out of the question given our tech progress of the last 200+ years.

And not only materials, but future discoveries and applications in and of quantum physics could lead, finally, to the development of "force-fields" or energy fields of some kind that could protect a craft travelling at relativistic speeds from particles and micro-meteorites in interstellar space. Perhaps artificially generated massive magnetic "shields" could be developed.

"Graphene", one atom thick and 200x stronger than steel, is already known. Who knows what we'll have (with regards to materials) 200 years from now?

I may be becoming an "old fuddy-duddy" and all about this, as I'm not one to suggest that faster-than-light travel is possible. Not at all. But approaching a sizeable fraction of lightspeed IS possible.

 

[yevaud]

A sensible (hypothetical) near-light speed space ship design can be found in John Walker's C-ship web pages here:
http://www.fourmilab.ch/cship/craft.html. His related pages on near-light speed travel are also very instrucyive.

Chris

Interesring, though one item:

"Space is not a vacuum but rather a diffuse gas of relict photons left over from the Big Bang"

I believe I would strenuously argue relict photons are not a "gas."

 

[csmyth3025]

A sensible (hypothetical) near-light speed space ship design can be found in John Walker's C-ship web pages here:
http://www.fourmilab.ch/cship/craft.html. His related pages on near-light speed travel are also very instructive.

Chris

Interesting, though one item:

"Space is not a vacuum but rather a diffuse gas of relict photons left over from the Big Bang"

I believe I would strenuously argue relict photons are not a "gas."

I agree - and I suspect Mr. Walker would also agree. I think he used the "diffuse gas" description to make it easier for non-scientific readers to grasp the idea that there are photons zinging around everywhere in space and, when one moves at relativistic speeds, they do actually impart a "drag" on the ship.

Chris

 

[yevaud]

Yeah, that's probably so.

That friction with the Interstellar medium would be fierce at a substantial percent of C. Those Photons will hit hard.

 

[BenS1985]

100 years from now

Some fundamental problems cannot easily be solved in different ways. For instance, after more than 5.000years of progress cars still use wheels. There is just no better way to solve this particular problem and I suspect wheels will be around for many more centuries.

No, but they can be addressed to make it easier and more convenient to get from point A to point B. We may still use wheels, but we've replaced organically-propelled wheels (horses & buggies) with steel which has been a massive boon to transportation. You say there is no way to solve the problem, but there is really no way to know what the future holds for technologies to accommodate interstellar travel. We've poured only billions into space travel and infrastructure over the span of about 6 decades. Comparatively, we spend trillions per year on automobiles and automotive technology. I believe that when we approach such marks with space travel - interstellar or stellar - we're going to solve some of the problems we see today as insurmountable.

People expect that given sufficient time, Science and progress can beat whatever laws Nature throws at us.
If you can accept that progress will never make things colder than -273°K, then why can't you accept that there is in fact a speed limit? Because it is not convenient?

I never said anything about breaking the laws of the speed of light. I merely said that science may solve problems with the supposed impossibility of interstellar travel. We haven't even left Earth for any sufficient amount of time, yet we're making wild accusations about the plausibility of interstellar travel. I say that we start walking before we say we cannot run.

 

[ZenGalacticore]

A sensible (hypothetical) near-light speed space ship design can be found in John Walker's C-ship web pages here:
http://www.fourmilab.ch/cship/craft.html. His related pages on near-light speed travel are also very instrucyive.

Chris

Interesring, though one item:

"Space is not a vacuum but rather a diffuse gas of relict photons left over from the Big Bang"

I believe I would strenuously argue relict photons are not a "gas."

And, I wonder, would those 'relicit' photons offer any significant resistance? (Not saying they wouldn't, just asking.)

But it seems to me, that if we could ever attain the tech heights necessary to achieve relativistic speeds, that we would en tandem develop other related and apparently unrelated technologies that we could apply.

History itself is full of examples of unrelated technologies coming together. For example, without the tech of intertubes and rubber tech, the automobile or the maximization of internal combustion engine tech could not have been realized.

Another example being submarines. Without radio and sonar, subs would've been practically much more difficult in operation.

 

[bdewoody]

Thousand-year trips are not only a possibility, it will be a necessity! Only, no machine can survive for so long without failure. :?

If no exotic physics comes to change the game, we're stuck in the Solar System, period.

Now you are waking up to the bitter truth.

 

[Skyskimmer]

Thousand-year trips are not only a possibility, it will be a necessity! Only, no machine can survive for so long without failure. :?

If no exotic physics comes to change the game, we're stuck in the Solar System, period.

Now you are waking up to the bitter truth.

Says who. This stuff is silly. 4000 years to the nearest star is not that extreme in terms of human evolution. Sure we will need to develope endurance, but realize, that the engines will not be firing for more than a year, with no rust, or anything of the sort they will last a long time. Life support is the issue. I'm guessing this type of mission will not be planned for atleast a few hundred years so we can let whoever figure it out. It most likely will be done by some other forum of genetically engineered life that have no worries about gravity or radiation. There primarly need is long term energy.

 

[Space_pioneer]

Who ever suggested 1000 years? I'm sure a ship can sustain its self for around 40 years, which would be the amount of time it would take if a ship was going at 10% the speed of light to Alpha centauri.

 

[Skyskimmer]

Who ever suggested 1000 years? I'm sure a ship can sustain its self for around 40 years, which would be the amount of time it would take if a ship was going at 10% the speed of light to Alpha centauri.

Than your talking about a very high risk of running into something, not to mention alot of energy being required. Of course my opionion is that once you get to the high speed you disasemble your space craft into a immense gel. That way if something does hit you it'll pass through like a bullet in air. Something that is often left out of the impact equations is that most materials won't absorbed that kind of energy, it'll pass through like a rock falling into a bucket of water.

 

[Space_pioneer]

Who ever suggested 1000 years? I'm sure a ship can sustain its self for around 40 years, which would be the amount of time it would take if a ship was going at 10% the speed of light to Alpha centauri.

Than your talking about a very high risk of running into something, not to mention alot of energy being required. Of course my opionion is that once you get to the high speed you disasemble your space craft into a immense gel. That way if something does hit you it'll pass through like a bullet in air. Something that is often left out of the impact equations is that most materials won't absorbed that kind of energy, it'll pass through like a rock falling into a bucket of water.

Or you could use a very hard materialto push smaller things out of the way? I'm sure that the ship's computer will be smart enough to realize that you are about to hit sedna.

How in god's name do you dissasemble it to a 'gel'?

 

[Skyskimmer]

Who ever suggested 1000 years? I'm sure a ship can sustain its self for around 40 years, which would be the amount of time it would take if a ship was going at 10% the speed of light to Alpha centauri.

Than your talking about a very high risk of running into something, not to mention alot of energy being required. Of course my opionion is that once you get to the high speed you disasemble your space craft into a immense gel. That way if something does hit you it'll pass through like a bullet in air. Something that is often left out of the impact equations is that most materials won't absorbed that kind of energy, it'll pass through like a rock falling into a bucket of water.

Or you could use a very hard materialto push smaller things out of the way? I'm sure that the ship's computer will be smart enough to realize that you are about to hit sedna.

How in god's name do you dissasemble it to a 'gel'?

Melt the majority of materials into beeds of some sory. and just mix it will gel and water. The nuclear materials of corse, would still needed for heat, so they would have to have multiple back ups along with the trip. Might sound odd but it's essentially mining in reverse.
Of course you can think what you want of that idea, point is, nothing can stop these objects at those speeds, completly pointless to stop them, far far more logical to let them pass. Of course this will mean loss of life for the people, but thats gonna happen regardless.Remember this is space travel it's not limited to the law of science fiction .