interstellar travel

[MRlogic]

i started this thread to get peoples opinions of how humans can travel to even the distant star in a humans average lifetime. got any ideas?

[Mr Skeptic]

Invent new laws of physics!

 

Or, build a solar-system sized coilgun, put the human into a liquid (preferably also fill lungs with breathable liquid), and shoot them at close to the speed of light at a target system.

[MRlogic]

Invent new laws of physics!

 

Or, build a solar-system sized coilgun, put the human into a liquid (preferably also fill lungs with breathable liquid), and shoot them at close to the speed of light at a target system.

 

 

cant you need to have less mass to even get close to the speed of lght

[CaptainPanic]

The nearest star is 4 lightyears away.

 

To get there within a professional lifetime, which is about 40 years, you'd need to travel at an average 1/10th of the speed of light.

Since the main problem is likely to be acceleration (and delivering the energy in the first place), I propose that we accelerate half the time, and decellerate the other half the time. In other words, our desired top speed is 1/5th of the speed of light, or nearly 60,000 km/s, to be reached after 20 years.

 

The necessary acceleration for that is:

V(t) = a*t + V(0)

60,000,000 = a*(3600*24*365*20)

a = 0.1 m/s2

 

So far, it seems quite reasonable...

 

In terms of kinetic energy (assuming a super lightweight 1000 kg spacecraft), that is:

E = 1/2*m*v^2 = 0.5*1000*(60,000,000)^2=1.8*10^18J, or 1.8 EJ.

 

If we express that in terms of fuel, it's the equivalent of 12.6 million metric tons of hydrogen... which shows that we at least will require a different propulsion. Either we provide the energy from the earth (earth consumes 474 EJ per year), or we go with Mr Skeptic's plan:

 

Invent new laws of physics!

 

Or, build a solar-system sized coilgun, put the human into a liquid (preferably also fill lungs with breathable liquid), and shoot them at close to the speed of light at a target system.

And indeed, it may be easier to invent new laws of physics. Until then, I think we'll be stuck here for a little longer.

[Danijel Gorupec]

I think, it would be much easier to expand average human lifetime to a thousand years (probably by slowing us down - like extremely slow turtles). This way stars would at least seem closer.

[MRlogic]

The nearest star is 4 lightyears away.

 

To get there within a professional lifetime, which is about 40 years, you'd need to travel at an average 1/10th of the speed of light.

Since the main problem is likely to be acceleration (and delivering the energy in the first place), I propose that we accelerate half the time, and decellerate the other half the time. In other words, our desired top speed is 1/5th of the speed of light, or nearly 60,000 km/s, to be reached after 20 years.

 

The necessary acceleration for that is:

V(t) = a*t + V(0)

60,000,000 = a*(3600*24*365*20)

a = 0.1 m/s2

 

So far, it seems quite reasonable...

 

In terms of kinetic energy (assuming a super lightweight 1000 kg spacecraft), that is:

E = 1/2*m*v^2 = 0.5*1000*(60,000,000)^2=1.8*10^18J, or 1.8 EJ.

 

If we express that in terms of fuel, it's the equivalent of 12.6 million metric tons of hydrogen... which shows that we at least will require a different propulsion. Either we provide the energy from the earth (earth consumes 474 EJ per year), or we go with Mr Skeptic's plan:

 

 

And indeed, it may be easier to invent new laws of physics. Until then, I think we'll be stuck here for a little longer.

 

 

but how do we obtain that much energy?

[Airbrush]

i started this thread to get peoples opinions of how humans can travel to even the distant star in a humans average lifetime. got any ideas?

 

First send probes to nearby stars. These can be designed to withstand tremendous G forces. Try nuclear pulse (see project Orion) to accelerate the probes to over HALF light speed, then decelerate upon arrival. Explore the star system and send the findings back to Earth. No return trip necessary, but the probe can explore the planets around the star and send the info back to Earth. That way we know what to do if we send humans on such a mission.

 

http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)

Edited September 21, 2010 by Airbrush

[Janus]

First send probes to nearby stars. These can be designed to withstand tremendous G forces. Try nuclear pulse (see project Orion) to accelerate the probes to over HALF light speed, then decelerate upon arrival. Explore the star system and send the findings back to Earth. No return trip necessary, but the probe can explore the planets around the star and send the info back to Earth. That way we know what to do if we send humans on such a mission.

 

http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)

 

Thrust is not the issue, exhaust velocity is. The relativistic rocket equation is

 

[math]V_f = c \tanh \left( \frac{Ve}{c} \ln(MR) \right )[/math]

 

With Ve being the exhaust velocity and MR is the mass ratio (initial mass/final) of the craft.

 

Rearranged to solve for MR, and given that a Nuclear pulse rocket can deliver an exhaust velocity of 30 km/s, we get a mass ratio of 2.1e43 just to get to 1/100 of the speed of light.

 

To put this in perspective, the upper estimated mass of the entire galaxy(dark matter included), is only 2e42 kg. So it would take the order of a mass equal to ten galaxies in fuel per kilogram of payload mass to reach even 1% of c with a nuclear pulse drive.

 

The only foreseeable way that interstellar travel within a lifetime will be possible is to develop propulsion systems that are capable of much higher exhaust velocities.

[MRlogic]

Thrust is not the issue, exhaust velocity is. The relativistic rocket equation is

 

[math]V_f = c \tanh \left( \frac{Ve}{c} \ln(MR) \right )[/math]

 

With Ve being the exhaust velocity and MR is the mass ratio (initial mass/final) of the craft.

 

Rearranged to solve for MR, and given that a Nuclear pulse rocket can deliver an exhaust velocity of 30 km/s, we get a mass ratio of 2.1e43 just to get to 1/100 of the speed of light.

 

To put this in perspective, the upper estimated mass of the entire galaxy(dark matter included), is only 2e42 kg. So it would take the order of a mass equal to ten galaxies in fuel per kilogram of payload mass to reach even 1% of c with a nuclear pulse drive.

 

The only foreseeable way that interstellar travel within a lifetime will be possible is to develop propulsion systems that are capable of much higher exhaust velocities.

 

 

what about using shortcuts?

[Moontanman]

Why does it have to be fast interstellar travel? A torus using magnetic sails could there in a few generations...

[Maximus Semprus Veridius]

Even if we could somehow travel at the speed of light to propel even an everyday car you would need most of the energy in the Universe to do it, so it's not gonna happen in my lifetime!! However we don't know enough about....well...everything I suppose to make claims like the one I just made .

[Airbrush]

To put this in perspective, the upper estimated mass of the entire galaxy(dark matter included), is only 2e42 kg. So it would take the order of a mass equal to ten galaxies in fuel per kilogram of payload mass to reach even 1% of c with a nuclear pulse drive.

 

That is not what the proponents of project Orion believe:

 

"Later studies indicate that the top cruise velocity that can theoretically be achieved by a thermonuclear Orion starship is about 8% to 10% of the speed of light. An atomic (fission) Orion can achieve perhaps 3%-5% of the speed of light. "

 

Medusa propulsion can go even faster.

 

http://en.wikipedia.org/wiki/Nuclear_pulse_propulsion#Medusa

 

Then there is also the Star Trek method if you can get some antimatter.

 

"A nuclear pulse drive starship powered by matter-antimatter pulse units would be theoretically capable of obtaining a velocity between 50% to 80% of the speed of light."

 

http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)

Edited September 22, 2010 by Airbrush

[Janus]

That is not what the proponents of project Orion believe:

 

"Later studies indicate that the top cruise velocity that can theoretically be achieved by a thermonuclear Orion starship is about 8% to 10% of the speed of light. An atomic (fission) Orion can achieve perhaps 3%-5% of the speed of light. "

 

Medusa propulsion can go even faster.

 

http://en.wikipedia.org/wiki/Nuclear_pulse_propulsion#Medusa

 

Then there is also the Star Trek method if you can get some antimatter.

 

"A nuclear pulse drive starship powered by matter-antimatter pulse units would be theoretically capable of obtaining a velocity between 50% to 80% of the speed of light."

 

http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)

 

The problem is that predicted exhaust velocities for Orion are all over the map. So until an actual nuclear pulse engine is built, we don't know which of these values are achievable in practice. A lesson in history would be the NERVA engine. It was hoped that it would be a significant improvement over chemical rockets. The actual tests done didn't quite hold up to the promise. They were an improvement, just not to the degree they thought they would be.

[Moontanman]

There is always the Nuclear light bulb rocket with many times the Specific Impulse of the NERVA type nuclear rocket.

 

Best chemcal rocket Specific impluse 450

NERVA Specific impluse 900

Nuclear light bulb rocket Specific impluse 5,000

 

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

 

A nuclear lightbulb is a hypothetical type of spacecraft engine using a Fission reactor to achieve Nuclear propulsion. Specifically it would be a type of Gas core reactor rocket that separates the nuclear fuel from the coolant/propellant with a quartz wall. It would be operated at such high temperature (approx. 25,000°C) that the vast majority of the electromagnetic emissions would be in the hard ultraviolet range. Fused silica is almost completely transparent to this light, so it would be used to 'bottle' the uranium hexafluoride and allow the light to escape and be used to heat hydrogen gas for a rocket propellant or to generate electricity using Photovoltaics.

 

This type of reactor shows great promise in both of these roles, as a rocket engine it has the enormous advantage of being completely reusable, greatly reducing costs by amortizing the cost of the rocket over many launches. This is very attractive compared to the current practice of using disposable rockets. As a method to generate electricity, nuclear lightbulbs can be combined with photovoltaics. This method also does not involve the release of any radioactive material from the rocket, unlike other designs which would cause Nuclear fallout if used in a planetary atmosphere (i.e. Project Orion).

 

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

 

A gas nuclear reactor (or gas fueled reactor) limits the only temperature limiting materials in a reactor to the reactor walls. A limitation for conventional nuclear fission reactors is that if the nuclear fuel temperature were to rise too high in temperature, the Nuclear reactor core would melt. It may also be possible to confine gaseous fission fuel magnetically, electrostatically or electrodynamically in the reactor so that it would not touch (and melt) the reactor walls. A potential benefit of the gaseous reactor core concept is that instead of relying on the traditional rankine or brayton conversion cycles, it may be possible to extract electricity magnetohydrodynamically, or with simple direct electrostatic conversion of the charged particles.

[MRlogic]

Even if we could somehow travel at the speed of light to propel even an everyday car you would need most of the energy in the Universe to do it, so it's not gonna happen in my lifetime!! However we don't know enough about....well...everything I suppose to make claims like the one I just made .

 

 

we will never be able to travel the speed of light but use shortcuts that will take us to destinations almost instant

[Mr Skeptic]

we will never be able to travel the speed of light but use shortcuts that will take us to destinations almost instant

 

Except that you can't make wormholes without exotic matter, and even then they would probably kill you, among other problems.

[MRlogic]

Except that you can't make wormholes without exotic matter, and even then they would probably kill you, among other problems.

 

 

i dont thing wormholes would kill us. i think there just portals, rips in space to other worm holes or even other dimensions. but to open a worm hole it is believed that you need the power of a trillion of a trilion hydrogen bombs at once. or dark matter perhaps?

[CaptainPanic]

That is not what the proponents of project Orion believe:

 

"Later studies indicate that the top cruise velocity that can theoretically be achieved by a thermonuclear Orion starship is about 8% to 10% of the speed of light. An atomic (fission) Orion can achieve perhaps 3%-5% of the speed of light. "

 

Medusa propulsion can go even faster.

 

http://en.wikipedia.org/wiki/Nuclear_pulse_propulsion#Medusa

 

Then there is also the Star Trek method if you can get some antimatter.

 

"A nuclear pulse drive starship powered by matter-antimatter pulse units would be theoretically capable of obtaining a velocity between 50% to 80% of the speed of light."

 

http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)

 

These bomb-propulsion systems seem quite hard to control, and maintenance might be a nightmare on that space ship. But it will work (after all, it's only an external nuclear space version of the good old combustion engine).

 

But with nuclear materials, shouldn't it be possible to do this in a more controlled and continuous way? If you allow a regular nuclear reaction to detonate, a large number of particles will push onto some sail or pusher plate. But if you just have a controlled reaction in open space behind a spacecraft, particles will radiate in all directions (like in a blast), but this will be continuous, rather than pulsed. Seems a more relaxing way of space travel, and much less stress on the craft.

 

Is it just a matter of being able to burn up more nuclear material in a shorter period of time with this bomb-propulsion systems??

[between3and26characterslon]

I don't think any form propulsion that relies on throwing stuff out the back (ie rockets etc...) is going to get humans anywhere on an atronomical scale. It might get a probe out of our solar system a bit quicker than voyager but that's about it.

 

 

If we ever get a grip on gravity, if we could generate gravity without needing mass to do it then we could gernerate a gravitational field in front of a ship and that ship would fall into the gravity well for as long as it's turned on.

 

The rate of acceleration would be almost limitless because the gravity would affect everything in the ship equally, and could possibly achieve speeds near to 'c'. This is totaly science fiction though

 

 

Any other form of propulsion would realistically have to be limited to an acceleration of 1g so that humans could live comfortably. So although our nearest star is 4.5 lightyears away, accelertating at 1g to near lightspeed turning round and decelerating at 1g it would take us about 280 years to get there.

[Moontanman]

I don't think any form propulsion that relies on throwing stuff out the back (ie rockets etc...) is going to get humans anywhere on an atronomical scale. It might get a probe out of our solar system a bit quicker than voyager but that's about it.

 

 

If we ever get a grip on gravity, if we could generate gravity without needing mass to do it then we could gernerate a gravitational field in front of a ship and that ship would fall into the gravity well for as long as it's turned on.

 

The rate of acceleration would be almost limitless because the gravity would affect everything in the ship equally, and could possibly achieve speeds near to 'c'. This is totaly science fiction though

 

 

Any other form of propulsion would realistically have to be limited to an acceleration of 1g so that humans could live comfortably. So although our nearest star is 4.5 lightyears away, accelertating at 1g to near lightspeed turning round and decelerating at 1g it would take us about 280 years to get there.

 

 

Umm no, accelerating at 1G to very near light speed and then decelerating would get you there in a little over 6 years earth time and less than 4 years ship time. I can't seem to find the equations I need to be exact but 280 years is way off the mark...

[Janus]

 

 

 

Any other form of propulsion would realistically have to be limited to an acceleration of 1g so that humans could live comfortably. So although our nearest star is 4.5 lightyears away, accelertating at 1g to near lightspeed turning round and decelerating at 1g it would take us about 280 years to get there.

That figure is way off. Accelerating halfway and decelerating the rest of the way at 1g will get you there in ~3.6 yrs, ship time (~6 years Earth time).

Edited September 23, 2010 by Janus

[losfomot]

Umm no, accelerating at 1G to very near light speed and then decelerating would get you there in a little over 6 years earth time and less than 4 years ship time. I can't seem to find the equations I need to be exact but 280 years is way off the mark...

 

If you scroll down the page at THIS LINK there is a calculator for 'long relativistic journeys' you can enter the acceleration and the distance and it will figure out how long to get there. (It automatically assumes acceleration for half the trip and deceleration for the other half).

 

4.3 light years at 1G would take about 3.56 years.

[between3and26characterslon]

Umm no, accelerating at 1G to very near light speed and then decelerating would get you there in a little over 6 years earth time and less than 4 years ship time. I can't seem to find the equations I need to be exact but 280 years is way off the mark...

 

 

Ok didn't check my facts there, just remember hearing along time ago it would take something like 280 years. I still think though that ejecting stuff out the back of a space ship is not going to work for any manned interstellar flight

 

You might like to watch this, particularly the last 5 mins which are all about space and time travel.

 

http://www.youtube.com/watch?v=3zrGkiPJn5s&p=9A8A80BC2834046A&index=18

[Moontanman]

If you scroll down the page at THIS LINK there is a calculator for 'long relativistic journeys' you can enter the acceleration and the distance and it will figure out how long to get there. (It automatically assumes acceleration for half the trip and deceleration for the other half).

 

4.3 light years at 1G would take about 3.56 years.

 

 

Thanks great resource...

[Janus]

There is always the Nuclear light bulb rocket with many times the Specific Impulse of the NERVA type nuclear rocket.

 

Best chemcal rocket Specific impluse 450

NERVA Specific impluse 900

Nuclear light bulb rocket Specific impluse 5,000

 

 

 

Great for interplanetary (about a month to Mars with a mass ratio of 10) Not so great for interstellar.