Science Rapid Interstellar spaceflight, exploration and,colonization thread

[garyw]

and just how much mass will you be accelerating and how will you be using this laser sail? I think this concept is seriously flawed.

 

[fsci123]

and just how much mass will you be accelerating and how will you be using this laser sail? I think this concept is seriously flawed.

Well I am still working on the center hab but last time I checked with Robert forwards PDF he had a manned mission in planning too...

 

[T.Neo]

Well I will be using multiple lasers so I presume that smaller lens could do the same job...

Other proposals used multiple lasers as well, but I think they still needed a gigantic fresnel lens.

Well the helium was supercooled and it was pretty close to superfluid so I just made it superfluid...

Why? What is the advantage of superfluid helium?

Well I don't remember the exact weight as I am using my phone but it was relatively light...

What is the mass ratio then? That is the important number.

Well my craft is suppose to travel at at peak speed of 0.5c so...

My confusion stems from the fact that Daedalus probably has more propellant volume than you do, but achieves a much lower velocity.

To get to 0.5c using He3-He3 fusion (not considering relativistic effects) you would need a mass ratio of something like 1560. :uhh:

If you want to brake then you need to start braking almost before you launch to the target system!

It depends on what rate you can accelerate really. But considering the characteristics of forseen drive technologies, you'd only be able to achieve pretty poor accelerations.

the only interstellar probe project thats being looked at today is Icarus which is a follow on to Daedalus and they are targeting .07c

I hope they don't mind everyone in the program being dead by the time the probe sends its destination data back. :dry:

and just how much mass will you be accelerating and how will you be using this laser sail? I think this concept is seriously flawed.

Seconded.

A laser sail might be able to get you up to speed, theoretically at least, but it can't decelerate you. Forward suggested detaching a part of the sail and using it to reflect back on the primary sail/ship to decelerate it... but it sounds easier said than done.

I think the inclusion of the gigantic laser array and the gigantic mirror would turn an already huge project into an unfeasibly huge one.

 

[garyw]

I hope they don't mind everyone in the program being dead by the time the probe sends its data back. :dry:

No. That was an accepted part of the outcome. It would fall to several generations of people later to pick up the data. of course, the others would have plenty to keep them going with the en-route data collection.

 

[T.Neo]

Maybe they should cut their top speed to 0.1% of c, it would make the spacecraft technology so much less demanding. All you have to do is to make sure the program is continued by several civilisations.

And hope that the probe doesn't break down a fifth of the way there.

 

[fsci123]

Well I invisioned that a couple lasers in sol will propel the craft to 0.5c a few decades later another smaller laser will slow it down enough that fusion engines can succesfully operate... Because the craft should be superexpensive I am considering it returning back to sol to restart the cycle...

 

[T.Neo]

Lasers in sol? Like, in the Sun? Ouch.

Do you realise the scale of everything going on here? If you had 'a couple' of lasers, they would have to be absolutely gigantic.

How do you propose to slow the craft down?

How are you going to return the craft to the solar system if there is no gigantic battery of lasers at the starting point?

 

[fsci123]

Lasers in sol? Like, in the Sun? Ouch.

Do you realise the scale of everything going on here? If you had 'a couple' of lasers, they would have to be absolutely gigantic.

How do you propose to slow the craft down?

How are you going to return the craft to the solar system if there is no gigantic battery of lasers at the starting point?

I meen the sol system...

The batteries will still be gigantic it's just they won't be that powerful... Even if it takes a little longer I still want them back for reuse...

 

[Urwumpe]

Isn't actually Helium already superfluous if it is just liquid? I have problems imagining conditions in which Helium in your spacecraft would not be superfluous. (Pun intended actually)

 

[T.Neo]

The batteries will still be gigantic it's just they won't be that powerful... Even if it takes a little longer I still want them back for reuse...

Yes, they will be powerful. More powerful than the engine on such a spacecraft, at any rate.

And getting the vehicles back for reuse is more a matter of how it is possible and how it is achieved, rather than how much longer it takes.

 

[fsci123]

Isn't actually Helium already superfluous if it is just liquid? I have problems imagining conditions in which Helium in your spacecraft would not be superfluous. (Pun intended actually)

Well I seen liquid helium transition into superfluid and if there is a transition there is more than one state.

 

[garyw]

I meen the sol system...

The batteries will still be gigantic it's just they won't be that powerful... Even if it takes a little longer I still want them back for reuse...

So if the batteries are gigantic and not powerful what is the point? Surely less batteries (less mass) is better? Why would you even need gigantic batteries? Surely the heat from the fusion drive would be enough to keep the batteries charged?

Well I seen liquid helium transition into superfluid and if there is a transition there is more than one state.

Yes? And? What does superfluid helium have to do with an interstellar spacecraft? How do you maintain the superfludity of the helium?

 

[Urwumpe]

Well I seen liquid helium transition into superfluid and if there is a transition there is more than one state.

Yes - but superfluous helium is cooled at least below 2K, instead of the 4K to actually have it liquid. 2K is less than the radiation input you get by the cosmic background radiation, it takes SERIOUS effort to get Helium cooled down so far.

So in practical applications as propellant, you won't be storing helium in its superfluous form.

 

[T.Neo]

So if the batteries are gigantic and not powerful what is the point? Surely less batteries (less mass) is better? Why would you even need gigantic batteries? Surely the heat from the fusion drive would be enough to keep the batteries charged?

The subject is batteries, or arrays, of laser propulsion units to drive a lightsail. I think you're mixing that up with some kind of energy storage device onboard the ship.

 

[fsci123]

Well I chose supefluid helium because of the properties involved... Suplerfluid has a tendency to creep up walls and stuff

 

[garyw]

And of what use is that in space?

In the shuttle fuel is feed into pumps via gasseous helium expanding into the tank to push the fuel. There is no reason an intersteller probe couldn't use the same technique or it could use ullage motors or it could use fusion pellets.

 

[fsci123]

And of what use is that in space?

In the shuttle fuel is feed into pumps via gasseous helium expanding into the tank to push the fuel. There is no reason an intersteller probe couldn't use the same technique or it could use ullage motors or it could use fusion pellets.

Well the previuous craft uses liquid helium as a fuel and you are trying to pump it into the engine using helium...:shifty: