Spacetravel possible?

[Fletcher]

Suppose we were tasked to make a spaceship of some sort that could go really fast like 1/10 c or so. Now we want to space travel. What would happen if we hit something like one of our probes or a piece of rock? Game over?

 

[Wallace]

Yes, I imagine navigation would be a tricky thing to do at relativistic speeds since even a small light object has a huge amount of kinetic energy at those kinds of speeds!

As an interesting but barely related side note, if you were star treking across the Universe using anhttp://en.wikipedia.org/wiki/Alcubierre_drive" [Broken] you would not have to worry about this, since in your local frame you are in fact stationary, so anything that comes into your 'warp bubble' will also be at rest with respect to you.

It's a pity that the Alcubierre metric is probably un-physical

 

[cesiumfrog]

Hard to answer that so simply. Depends on lots of things, like: how big is the ship, how strong is it, does it have any particular technologies to deal with this (say, radar detection plus lasers to avoid impacts, or compartmentisation and repair techniques to deal with impacts), etc.

Moreover, what do you call game over? If we hang around with all our eggs on this rock, it's only a matter of time before an asteroid may wipe us all it, but if even a small percentage of spaceships could survive to reach new colonies..

 

[Fletcher]

I just meant, would the object go right through our spaceship, most likely killing us? Or would we go right through it, destroying it but being mostly ok?

 

[russ_watters]

The Space Shuttle Columbia was almost brought down by a paint chip on a reciprocal orbit (closing speed, 33,000 mph). It went most of the way through the 6-pane (I think it is 6...) windshield. A bolt (there are lots out there) would have gone through the windshield like it wasn't even there.

 

[Janus]

A small grain of sand at 0.1c, would have as much energy as 18kg of TNT.

 

[Brain Dwarf]

Yet another reason why aliens [if they exist] won't come to us...

 

[Tim09]

A small grain of sand at 0.1c, would have as much energy as 18kg of TNT.

That's actually really interesting. Prove it.

 

[Quaoar]

That's actually really interesting. Prove it.

1/2 m v^2 = 1/2 (10^-5 kg) * (3x10^7 m/s) = 4.5 x 10^8 joules = 1 ton tnt.

The relativistic result is only a couple percentage points different, and considering my estimate of the mass of a grain of sand is fairly rough in the first place, I chose to neglect it.

 

[William Astley]

Hi Flecher,

Another safety issue for space travel is radiation. For travel outside of the earth’s protective magnetic field (Space station and all space travel except for the moon trips, are/were within the Earth's magnetic field) the astronauts would have severe cellular damage due to high energy Galactic Cosmic Rays. (GCR), if the spacecraft does not include a shielding system. The March 2006 issue of Scientific America had an interesting discussion of the problem and possible shielding methods for a Mars trip. (See attached for a synopsis.)

1) A material shield such as water is not practical (due to weight issues) as a couple of hundred feet of water is required around the entire space craft, to match the protection of the earth’s magnetic field. (Water was considered to be the best substance for a material shield, over say lead as the high energy GCR (mostly high energy protons) would create radioactive isotopes in the shielding material which are more dangerous than GCR itself. (Same problem occurs in a nuclear reactor. I.e. Non radioactive materials such as cooling lines, valves, reactor vessel, and so forth become radioactive and emit neutrons and alpha particles which are very dangerous.) It is necessary to shield the entire space craft, as without shielding the spacecraft structure would become radioactive.

2) A spacecraft generated magnetic field also was not practical as the required field strength would exceed that of a large particle accelerator. A particle accelerator requires liquid nitrogen, to create a superconductive material. The liquid nitrogen has weight issues and would require a sophisticated refrigeration system. Even with a super conductive material, the energy requirements of the spacecraft would require that a large nuclear power plant, be included on the space ship, which has weight and safety issues.

Shielding Space Travelers; March 2006; Scientific American Magazine; by Eugene N. Parker; 8 Page(s)
In science fiction, the worst threats to space travelers are large ones: careening asteroids, ravenous creatures, imperial battle cruisers. In reality, though, the scariest menaces for humans in space are the tiniest: fast-moving elementary particles known as cosmic rays. On a long journey, they would give astronauts a dose of radiation serious enough to cause cancer. Unlike most of the other challenges of venturing into deep space, which engineers should be able to solve given enough time and money, cosmic rays pose irreducible risks, and dealing with them involves fundamental trade-offs. They could be the show-stopper for visiting Mars.
In the laboratory, cosmic rays first presented themselves as a minor annoyance. They were discovered when physicists noticed that electrically charged bodies do not stay that way; their charge slowly leaks away through the air. Something had to be ionizing the air, allowing it to conduct electricity. Many researchers blamed the ambient radioactivity of the soil and rocks underfoot. Austrian physicist Victor Hess settled the issue in 1912, when he went aloft in a balloon and showed that the higher he rose, the faster the charge leaked off his electroscope. So the cause of the ionized air was something mysterious coming in from space--thus the name "cosmic rays."

 

[Tim09]

Hmm, fair nuff.