[Lars Larsen (OP)]

As far as I know, there is a certain particle concentration even in interstellar space (like one atom / cm^3 or so). If a space ship moves through interstellar space at a relativistic speed, would it melt down like a meteor in the atmosphere of the earth?

[Mr. Scientist]

In what sense? You mean a high density gas perhaps? A dense cloud maybe of radiative particles?

[lightarrow]

As far as I know, there is a certain particle concentration even in interstellar space (like one atom / cm^3 or so). If a space ship moves through interstellar space at a relativistic speed, would it melt down like a meteor in the atmosphere of the earth?

Certainly, you're right.

[Madidus_Scientia]

In what sense? You mean a high density gas perhaps? A dense cloud maybe of radiative particles?

What??

Certainly, you're right.

Bugger, just when I thought my interstellar spaceship was all set to go, now I have to invent shields

[Mr. Scientist]

In what sense? You mean a high density gas perhaps? A dense cloud maybe of radiative particles?

What??

Certainly, you're right.

Bugger, just when I thought my interstellar spaceship was all set to go, now I have to invent shields

Well it depends - you might survive the normal background scatter of radiation; its so cold you see. When we consider the massive clouds of particles which can be quite dense, there would be no way to travel through them sucessfully without cooking in the process.

[lightarrow]

Certainly, you're right.

Bugger, just when I thought my interstellar spaceship was all set to go, now I have to invent shields

Anyway, it depends: if the speed is not very high, you can use shields, otherwise there is no shield in the universe... []
The greater the speed, the greater the kinetic energy of the atoms you collide *and* the density of atoms, and these numbers goes to infinity as you approach light speed...

[Lars Larsen (OP)]

thanks a lot. What do you think, how long would a ship travelling at, say, 1/3 c survive out there? Hours, days, months...?

[lightarrow]

thanks a lot. What do you think, how long would a ship travelling at, say, 1/3 c survive out there? Hours, days, months...?

I'm sorry, I have no idea because it's not a speed so near to c.

[Soul Surfer]

The density of space is very low and in general you would have to be moving really close to the speed of light for it to be a problem however it does put a limit on the energy of cosmic ray particles.  The big problem is the cosmic microwave background photons which get blue shifted and eventually cause the particle to loose energy.

[Pmb]

As far as I know, there is a certain particle concentration even in interstellar space (like one atom / cm^3 or so). If a space ship moves through interstellar space at a relativistic speed, would it melt down like a meteor in the atmosphere of the earth?

Seems to me that when the radiation is of high enough energy to be of risk it is also of high enough energy to merely pass through the ship and not absorb a lot of it. There is a trade off. This is a good question though. Nice!

[AllenG]

Certainly, you're right.

Bugger, just when I thought my interstellar spaceship was all set to go, now I have to invent shields

Anyway, it depends: if the speed is not very high, you can use shields, otherwise there is no shield in the universe... []
The greater the speed, the greater the kinetic energy of the atoms you collide *and* the density of atoms, and these numbers goes to infinity as you approach light speed...

http://www.universetoday.com/2008/11/04/ion-shield-for-interplanetary-spaceships-now-a-reality/

Depends on what the shields are designed to defend against.
The small and very small work with different rules than large objects.

[Lars Larsen (OP)]

http://www.universetoday.com/2008/11/04/ion-shield-for-interplanetary-spaceships-now-a-reality/ [nofollow]

Depends on what the shields are designed to defend against.
The small and very small work with different rules than large objects.

That is amazing. But such a shield would only protect against ions and electrons, right? I have no idea, what the interstellar matter consinsts of - would this shield be usefull out there?

[LeeE]

The Bussard ramjet seems like a nice solution...

http://en.wikipedia.org/wiki/Bussard_ramjet

[Lars Larsen (OP)]

Seems that about 15-25% (by Fractional Volume) of the interstellar matter consists of neutral atoms or moleculs. The rest is ionized.

http://en.wikipedia.org/wiki/Interstellar_medium [nofollow]

Hemce a shield as suggestet above would not prevent those parts of the interstellar medium from colliding with the spaceship. Furthermore it is noteworthy, that the so called "molecular clouds", though only representing less than 1% (by fractional volume) of the interstellar matter, have a relatively high density (10^2—10^6 atoms/cm^3) - and those are neutral too.

The good news is, that the INTERGALACTIC MEDIUM is almost a perfect vacuum, if you want to trust wiki once more:

http://en.wikipedia.org/wiki/Intergalactic_medium#Intergalactic [nofollow]

So all we have to do is reaching the rim of our galaxy at a modest speed and then accelerate.

Who wants to join me? I'm so tired of this galaxy. We still need a chief cook and a navigator.

[yor_on]

Reading about that ion shield.
"a system no bigger than a large desk that uses the same energy as an electric kettle." And deflect all high energy particles? Or do they mean, only when not 'switched on'?