Real Physicists Theories on Interstellar travel.

[Txur’Itan]

Sub Light Starship -
Sci Fi Science- Building a Starship

Warp Drive -
Sci Fi Science: Traveling at Warp Speed

[Eyawng te Klltepayu]

Good article on the ISV Venture Star here:

http://www.projectrho.com/rocket/rocket3ap.html#avatar

[kewnya txamew'itan]

I don't like the alcubierre solution. For one thing, it seems at the moment that the creation of the bubble required is impossible, also, crossing into an already existant bubble would be impossible or at least a significantly worse solution that sub-light speed travel, due to the tidal forces and time dilation encountered when crossing the edge, furthermore, it requires the existence of exotic matter in relatively large quantities when such matter is 1. unobserved and 2. has properties that appear to be physically meaningless. In short, while it does allow for ftl travel it is often regarded as simply mathematical slight of hand rather than a meaningful solution and, even if it is  meaningful, it's completely impractical.

Bussard f-ramjets and artificial hibernation (or cryosleep, stasis, time dilation or other similar technique) is the best solution. Using these it would be possible to explore the galaxy in relatively short periods of subjective time albeit astronomical lengths of galactic time.

[Eyawng te Klltepayu]

Bussard f-ramjets and artificial hibernation (or cryosleep, stasis, time dilation or other similar technique) is the best solution. Using these it would be possible to explore the galaxy in relatively short periods of subjective time albeit astronomical lengths of galactic time.

No love for the propulsion methods used by the ISV Venture Star? Obviously the quantities of energy required are utterly monstrous, but other than that...

[kewnya txamew'itan]

It works but is still impractical. Carrying your own fuel around means you need more thrust to sustain the same acceleration. The beauty of Bussard ramjets is that they don't need to carry any fuel, they just scoop up interstellar gas to burn or, in the case of a Bussard f-ramjet, fuse.

[Eyawng te Klltepayu]

Don't forget that the acceleration leg of the outbound flight and the deceleration leg of the return flight will not require any onboard fuel.

Zubrin/Andrews have found that Bussard ramjets may only function along vectors perpendicular to the solar wind. Under other conditions the drag of such a system would exceed the thrust.
http://www.projectrho.com/rocket/slowerlight.php#Bussard_Ramjet
The collection systems may be more useful as a magnetic parachute/sail. You could probably use something like that to decelerate a spacecraft on approach to Alpha Centauri. But then (assuming Zubrin/Andrews are correct) you might need a different means of leaving the system...

[kewnya txamew'itan]

Don't forget that the acceleration leg of the outbound flight and the deceleration leg of the return flight will not require any onboard fuel.

Zubrin/Andrews have found that Bussard ramjets may only function along vectors perpendicular to the solar wind. Under other conditions the drag of such a system would exceed the thrust.

How so?

2. Did not know that. Well, there goes my plan for stellar exploration.

[Eyawng te Klltepayu]

Don't forget that the acceleration leg of the outbound flight and the deceleration leg of the return flight will not require any onboard fuel.

Zubrin/Andrews have found that Bussard ramjets may only function along vectors perpendicular to the solar wind. Under other conditions the drag of such a system would exceed the thrust.

How so

I can't find a link to the Zubrin & Andrews paper. But there's a summary of their critique on wikipedia:

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

Anyway, there's still plenty of semi-plausible starship designs remaining. Zubrin's own 'Entering Space' book has a nice synopsis in the last chapter. The book also has a recommendation by James Cameron on the back cover, so you know it's good...

[Arantele]

It works but is still impractical. Carrying your own fuel around means you need more thrust to sustain the same acceleration. The beauty of Bussard ramjets is that they don't need to carry any fuel, they just scoop up interstellar gas to burn or, in the case of a Bussard f-ramjet, fuse.

This is assuming that the interstellar matter/dust has enough mass or density to actually "burn"

[El Jacko]

It works but is still impractical. Carrying your own fuel around means you need more thrust to sustain the same acceleration. The beauty of Bussard ramjets is that they don't need to carry any fuel, they just scoop up interstellar gas to burn or, in the case of a Bussard f-ramjet, fuse.

This is assuming that the interstellar matter/dust has enough mass or density to actually "burn"

There's about 10^-21kg of Hydrogen per cubic metre lurking around (on average), so there's at least enough to fuse if the sail is big enough.

[kewnya txamew'itan]

Don't forget that the acceleration leg of the outbound flight and the deceleration leg of the return flight will not require any onboard fuel.

Zubrin/Andrews have found that Bussard ramjets may only function along vectors perpendicular to the solar wind. Under other conditions the drag of such a system would exceed the thrust.

How so

I can't find a link to the Zubrin & Andrews paper. But there's a summary of their critique on wikipedia:

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

Anyway, there's still plenty of semi-plausible starship designs remaining. Zubrin's own 'Entering Space' book has a nice synopsis in the last chapter. The book also has a recommendation by James Cameron on the back cover, so you know it's good...

Sorry, my post was very poorly worded, my "how so" was addressed at "Don't forget that the acceleration leg of the outbound flight and the deceleration leg of the return flight will not require any onboard fuel."

On the subject of that paper though, it sounds as though they proved it for a conventional Bussard ramjet, a fusion one would generate far more thrust per kilogram of fuel scooped (and therefore per unit drag) and so might not be limited by it. Also, that paper seems to be rather pessimistic about onboard power supplies and exhaust velocities both of which, if increased, could substantially increase its ability to fly into the solar wind. Lastly, reading what wikipedia said about it, they only showed that it couldn't sail into the solar wind (analogously to a square-rigged galleon being unable to sail closer to the wind than a beam reach (across the wind)) but, if it can accelerate across the wind then it can adjust its angular velocity and thus change it orbital distance around the star so it would be possible for it to drift inwards that way. Lastly, flying into the solar wind is only a problem on arrival when you already have momentum so the extra deceleration the solar wind provides can only be helpful.

[Eyawng te Klltepayu]

Sorry, my post was very poorly worded, my "how so" was addressed at "Don't forget that the acceleration leg of the outbound flight and the deceleration leg of the return flight will not require any onboard fuel."

I was referring to the ISV Venture Star.
http://www.projectrho.com/rocket/realdesigns.php#Avatar_ISV_Venture_Star

On the subject of that paper though, it sounds as though they proved it for a conventional Bussard ramjet, a fusion one would generate far more thrust per kilogram of fuel scooped (and therefore per unit drag) and so might not be limited by it. Also, that paper seems to be rather pessimistic about onboard power supplies and exhaust velocities both of which, if increased, could substantially increase its ability to fly into the solar wind. Lastly, reading what wikipedia said about it, they only showed that it couldn't sail into the solar wind (analogously to a square-rigged galleon being unable to sail closer to the wind than a beam reach (across the wind)) but, if it can accelerate across the wind then it can adjust its angular velocity and thus change it orbital distance around the star so it would be possible for it to drift inwards that way. Lastly, flying into the solar wind is only a problem on arrival when you already have momentum so the extra deceleration the solar wind provides can only be helpful.

No, it was for a fusion ramjet, albeit (as you point out) not one with a particularly high thrust or power supply.

I will point you in the direction of this book:

http://www.amazon.com/exec/obidos/tg/detail/-/1896522998/ref=pd_sr_ec_ir_b/104-1126362-6359942?v=glance&s=books&st=*


Which carries more work (this time by Landis) finding the conventional Bussard fusion ramjet concept unworkable.

However, there is an alternative:

http://www.centauri-dreams.org/?p=315

The Centauri Dreams book is a great read. Has a nice summary of the state of play on all things Bussard:

http://books.google.com.au/books?id=L4fffd3SivkC&pg=PA148&lpg=PA148&dq=landis+bussard+buzz+bomb&source=bl&ots=ov8rGw53d4&sig=cx1fEtSqhROZZF-5c_rpD0gyiBo&hl=en&ei=j3ztTN-kMcjQcdPhkagP&sa=X&oi=book_result&ct=result&resnum=3&ved=0CCYQ6AEwAg#v=onepage&q=landis%20bussard%20buzz%20bomb&f=false

[kewnya txamew'itan]

Sorry, my post was very poorly worded, my "how so" was addressed at "Don't forget that the acceleration leg of the outbound flight and the deceleration leg of the return flight will not require any onboard fuel."

I was referring to the ISV Venture Star.
http://www.projectrho.com/rocket/realdesigns.php#Avatar_ISV_Venture_Star

On the subject of that paper though, it sounds as though they proved it for a conventional Bussard ramjet, a fusion one would generate far more thrust per kilogram of fuel scooped (and therefore per unit drag) and so might not be limited by it. Also, that paper seems to be rather pessimistic about onboard power supplies and exhaust velocities both of which, if increased, could substantially increase its ability to fly into the solar wind. Lastly, reading what wikipedia said about it, they only showed that it couldn't sail into the solar wind (analogously to a square-rigged galleon being unable to sail closer to the wind than a beam reach (across the wind)) but, if it can accelerate across the wind then it can adjust its angular velocity and thus change it orbital distance around the star so it would be possible for it to drift inwards that way. Lastly, flying into the solar wind is only a problem on arrival when you already have momentum so the extra deceleration the solar wind provides can only be helpful.

No, it was for a fusion ramjet, albeit (as you point out) not one with a particularly high thrust or power supply.

I will point you in the direction of this book:

http://www.amazon.com/exec/obidos/tg/detail/-/1896522998/ref=pd_sr_ec_ir_b/104-1126362-6359942?v=glance&s=books&st=*


Which carries more work (this time by Landis) finding the conventional Bussard fusion ramjet concept unworkable.

However, there is an alternative:

http://www.centauri-dreams.org/?p=315

The Centauri Dreams book is a great read. Has a nice summary of the state of play on all things Bussard:

http://books.google.com.au/books?id=L4fffd3SivkC&pg=PA148&lpg=PA148&dq=landis+bussard+buzz+bomb&source=bl&ots=ov8rGw53d4&sig=cx1fEtSqhROZZF-5c_rpD0gyiBo&hl=en&ei=j3ztTN-kMcjQcdPhkagP&sa=X&oi=book_result&ct=result&resnum=3&ved=0CCYQ6AEwAg#v=onepage&q=landis%20bussard%20buzz%20bomb&f=false

1. I'd got that. Looking at the page I hadn't realised they said it would be able to accelerate at 1.5g under sail, in that case, no fuel would be needed although such an acceleration is absolutely ludicrous even for the earth-based satellite let alone the one at the Pandora end which would have to be shipped out in pieces.

The Bussard buzz bomb looks interesting too.

[Eyawng te Klltepayu]

There is no laser array at the Alpha Centauri end.

http://www.projectrho.com/rocket/realdesigns.php?iframe=true&width=100%&height=100%#Avatar_ISV_Venture_Star

The energy that would be needed to accelerate something as massive as the ISV Venture Star at 1.5g for 6 months would be pretty monstrous. Comparable to the energy Earth receives from the Sun per year. This is the kind of problem faced by every science fiction author who wishes to depict crewed transport between star systems in <10 years without resorting to magic.

[Kactima]

Space Travel is very complicating, It is possible but it takes large amounts of time
Traveling to Alpha Centauri (2nd closest) at the speed of light would get us there in 4.37 Years
Traveling to Barnard's Star (3rd closest) would take 5.9 Years
Gliese 581= 20.3 Years
And what makes it worse is that we cant travel faster then the speed of light
the speed of light is the ultimate speed limit
its not impossible it that to travel faster then the speed of light would take infinity energy which is impossible

[Niwantaw]

I seem to remember something about using black holes to warp space or something to travel ftl but I can't remember the exact theory right now...

[Kactima]

there is a theory where we can make space smaller in front of the ship so we can travel faster without going faster then lightspeed, but no one has and idea how such a device will work

[Toruk Makto]

That is the Lorentz-FitzGerald contraction theory. The problem is that the accelerations involved to reach such velocities are defined by General Relativity, which doesn't like correction factors thrown in to satisfy the contraction.

This has been batted around by scientists for a long time. The problem is the lack of a stable reference for the contraction equation.