Space Travel

[cdinesh1]

HI,

i was wondering if it was possible to propel rockets with rocket fuel till it reaches outer space and then propel it with solar power ...if this was possible the rockets would be able to carry us to other galaxies(if there r people who dare to travel).this was buggin me for a long time.....

[insane_alien]

yeah its possible but only in the inner solar system. inter galactic travel will require more than solar panels. also nobody could survive the trip. nearest major galaxy is 2 million light years away. thats 2 million years. thats how long ago the earliest humans fell out of the trees and couldn't be bothered climbing back up.

[Connor]

well, with length contraction, you could arrive in a year at extreme speeds, but everyone back home would be gone.

[Sisyphus]

You're thinking about solar sails, which propel themselves by photon pressure, thus having no need to carry fuel aboard. The Planetary Society funded a prototype called Cosmos One, but the launch rocket failed before it could reach orbit (stupid Russian surplus!).

 

There would be very little acceleration except close to the sun, but this problem could be overcome with huge space-based or moon-based lasers that could fire on the craft, thus providing it with lots of thrust.

 

Connor is right about length contraction. With a 1g acceleration, quite comfortable to humans, we would spend most of the trip near lightspeed, and thus with very slow passage of time. We could get to another galaxy in about 28 years, ship's time. Of course, millions of years would have passed back home...

[ecoli]

There would be very little acceleration except close to the sun, but this problem could be overcome with huge space-based or moon-based lasers that could fire on the craft, thus providing it with lots of thrust.

 

That doesn't really help out the return voyage, though.

[Sisyphus]

That doesn't really help out the return voyage, though.

 

It does, though. On a return voyage, it helps you slow down much faster, meaning you can spend most of the journey accelerating. Thus, you get the same speed boost both ways.

 

EDIT: Oh, wait. You're talking about the fact that by the time you return, there'll be nobody left to turn it on...

[Janus]

You're thinking about solar sails' date=' which propel themselves by photon pressure, thus having no need to carry fuel aboard. The Planetary Society funded a prototype called Cosmos One, but the launch rocket failed before it could reach orbit (stupid Russian surplus!).

 

There would be very little acceleration except close to the sun, but this problem could be overcome with huge space-based or moon-based lasers that could fire on the craft, thus providing it with lots of thrust.

 

Connor is right about length contraction. With a 1g acceleration, quite comfortable to humans, we would spend most of the trip near lightspeed, and thus with very slow passage of time. We could get to another galaxy in about 28 years, ship's time. Of course, millions of years would have passed back home...[/quote']

 

Of course, in order reach this velocity we would have to expend a lot of energy.

For example, assuming your 28 year voyage to Andromeda:

 

It would take about 3.24e+21 Joules of energy per kilogram to get a mass up to this speed at 100% efficiency. This is about 1/100000 of the amount of total energy the sun puts out in 1 sec. Now for a 28 year manned voyage, you are going to need a fairly large ship to maintain a proper living enviromenr for the entire time. Maybe something along the lines of the QE2.

 

The QE2 masses at 70,000,000 kg, which increases our energy requirement to that of the Sun's total output for 11 min 40sec.

 

To put this is Earthly terms:

 

The Sun burns hydrogen at a rate of 6.36e +11 kg per sec For our ship this works out to 4.45e+14 kg of hydrogen used. This is the equivalent of the amount of Hydrogen contained in 0.00028% in all the water on the Earth's surface. Unfortunately, we can't use all the Hydrogen, we need a particular isotope, Deutrium. Deutrium only makes up .02% of the naturally occuring Hydrogen, so we would need to process 1.4% of all the water in the world to provide enough hydrogen to get our ship up to speed.

 

Or to put it another way, we would have produce the same amount of energy as is realeased in the detonation of 11 million 50 megaton thermonuclear bombs. And this is with no loss of energy.

[Blunt]

Of course' date=' in order reach this velocity we would have to expend [i'] a lot[/i] of energy.

For example, assuming your 28 year voyage to Andromeda:

 

It would take about 3.24e+21 Joules of energy per kilogram to get a mass up to this speed at 100% efficiency. This is about 1/100000 of the amount of total energy the sun puts out in 1 sec. Now for a 28 year manned voyage, you are going to need a fairly large ship to maintain a proper living enviromenr for the entire time. Maybe something along the lines of the QE2.

 

The QE2 masses at 70,000,000 kg, which increases our energy requirement to that of the Sun's total output for 11 min 40sec.

 

To put this is Earthly terms:

 

The Sun burns hydrogen at a rate of 6.36e +11 kg per sec For our ship this works out to 4.45e+14 kg of hydrogen used. This is the equivalent of the amount of Hydrogen contained in 0.00028% in all the water on the Earth's surface. Unfortunately, we can't use all the Hydrogen, we need a particular isotope, Deutrium. Deutrium only makes up .02% of the naturally occuring Hydrogen, so we would need to process 1.4% of all the water in the world to provide enough hydrogen to get our ship up to speed.

 

Or to put it another way, we would have produce the same amount of energy as is realeased in the detonation of 11 million 50 megaton thermonuclear bombs. And this is with no loss of energy.

 

God damn... im stunned

 

 

Well what about the phycological part... lets assume(just for once) that food,water,oxygen,beds, etc etc could be contained in a normal size space shuttle. would we be able to finde 6-8 people who could bear living with eachother for 28 years ? i dont even think that dr. phil´s family would be able to do that(if you want prove go watch an episode of big brother or survivor).

 

 

On the subject of the sun sail would we be able to communicate with it at all ? if its traveling at a top speed of 150000 Mph or 75% the speed of ligth.. ?

[Klaynos]

well, with length contraction, you could arrive in a year at extreme speeds, but everyone back home would be gone.

 

You're ignoreing the fact you need to accelerate to reach a speed where this would be noticeable....

[Connor]

yeah, I'm just saying it would be theoretically possible to arrive in one's lifetime.

[Martin]

HI' date='

i was wondering if it was possible to propel rockets with rocket fuel till it reaches outer space and then propel it with solar power ...if this was possible the rockets would be able [b']to carry us to other galaxies[/b](if there r people who dare to travel).this was buggin me for a long time.....

 

our own galaxy has hundreds of billions of stars in it, and apparently many of these stars have planets going around them----already 100 or more have been found

it seems like there are planets everywhere we look IN OUR OWN GALAXY

 

 

so I don't understand, cdinesh, why you are already asking about how to go TO OTHER GALAXIES, why not first consider finding out about stuff in our own galaxy?

 

it makes for a confused discussion. the nearest other galaxies are roughly around a million lightyears away------so you get people started talking about voyages of a million lightyears or so. but the nearest stars in our own galaxy are only around 5 lightyears.

 

and the nearest STARS WITH PLANETS that we know of are only on the order of 10 to 100 lightyears. It might make sense to launch a robot probe to explore one of them sometime

 

it would take considerable time and resources to send a robot spacecraft on a journey of 100 lightyears, but it is not inconceivable. However in that case we are talking about staying IN OUR GALAXY

 

I think the technical requirements for that are more interesting to try to figure out than the requirements to go one or two million lightyears

 

Please get straight on what you want to ask about, and clarify the question.

[Sisyphus]

Of course' date=' in order reach this velocity we would have to expend [i'] a lot[/i] of energy.

For example, assuming your 28 year voyage to Andromeda:

 

It would take about 3.24e+21 Joules of energy per kilogram to get a mass up to this speed at 100% efficiency. This is about 1/100000 of the amount of total energy the sun puts out in 1 sec. Now for a 28 year manned voyage, you are going to need a fairly large ship to maintain a proper living enviromenr for the entire time. Maybe something along the lines of the QE2.

 

The QE2 masses at 70,000,000 kg, which increases our energy requirement to that of the Sun's total output for 11 min 40sec.

 

To put this is Earthly terms:

 

The Sun burns hydrogen at a rate of 6.36e +11 kg per sec For our ship this works out to 4.45e+14 kg of hydrogen used. This is the equivalent of the amount of Hydrogen contained in 0.00028% in all the water on the Earth's surface. Unfortunately, we can't use all the Hydrogen, we need a particular isotope, Deutrium. Deutrium only makes up .02% of the naturally occuring Hydrogen, so we would need to process 1.4% of all the water in the world to provide enough hydrogen to get our ship up to speed.

 

Or to put it another way, we would have produce the same amount of energy as is realeased in the detonation of 11 million 50 megaton thermonuclear bombs. And this is with no loss of energy.

 

Clearly a daunting task! And not one meant to be taken as a serious proposal. To be fair, though, I'd disagree with your estimate for necessary mass of the ship (even by a few orders of magnitude), and also with the necessity of using deuterium that we'd have to take with us as fuel. Solar sails and Bussard ramjets, even if neither would necessarily work, are examples of propulsion systems that don't even require fuel.

 

Also, are you sure your math is right? I haven't checked it, but that seems like an awful lot of energy for 28 years of 1g acceleration.

[insane_alien]

its right if you factor in relativity. which is inescapable considering you would be going faster than the speed of light without it.

[Janus]

Clearly a daunting task! And not one meant to be taken as a serious proposal. To be fair' date=' though, I'd disagree with your estimate for necessary mass of the ship (even by a few orders of magnitude), and also with the necessity of using deuterium that we'd have to take with us as fuel.

Solar sails and Bussard ramjets, even if neither would necessarily work, are examples of propulsion systems that don't even require fuel.

[/quote'] Actually, I was only calculating the amount of energy needed to get the ship up to speed without carrying fuel along. IOW, it is eqaul to the amount of Energy that woul dhave to be output by a LASER to push a light sail up to the needed velocity if 100% of that energy went into propelling the craft. I you want to consider the case where you do carry your own fuel then it gets much much worse.

edit: Carrying your own fuel, it turns out you need 1.8e+125 kg of fuel per kg of payload. This is assuming an exhaust velocity of 0.10c from nuclear fusion.

Bussard ramjets would be limited to velocities of less that 10% of c. At a certain point the drag caused by collecting your fuel exceed the thrust you would get from burning it.

 

Also, are you sure your math is right? I haven't checked it, but that seems like an awful lot of energy for 28 years of 1g acceleration.

 

If anything, it is on the conservative side. For instance, I just calculated the energy needed to get up to a speed that will get you to Andromeda in 28 yrs. But that is coasting at that speed for the majority of the trip. If you are accelerating the whole way, the velocity I used would be just your average velocity. Your top velocity would be twice that, meaning you would need even more energy than I calculated.

Edit: It turned out to be really conservative. Calculating for accelerating at 1g for the entire 28 yrs, it comes out to 2.5e41 joules of energy per kilogram. Thats equal to the entire energy output of the Sun for 21 million years!

[s pepperchin]

our own galaxy has hundreds of billions of stars in it' date=' and apparently many of these stars have planets going around them----already 100 or more have been found

it seems like there are planets everywhere we look IN OUR OWN GALAXY

 

 

so I don't understand, cdinesh, why you are already asking about how to go TO OTHER GALAXIES, why not first consider finding out about stuff in our own galaxy?

 

it makes for a confused discussion. the nearest other galaxies are roughly around a million lightyears away------so you get people started talking about voyages of a million lightyears or so. but the nearest stars in our own galaxy are only around 5 lightyears.

 

and the nearest STARS WITH PLANETS that we know of are only on the order of 10 to 100 lightyears. It might make sense to launch a robot probe to explore one of them sometime

 

it would take considerable time and resources to send a robot spacecraft on a journey of 100 lightyears, but it is not inconceivable. However in that case we are talking about staying IN OUR GALAXY

 

I think the technical requirements for that are more interesting to try to figure out than the requirements to go one or two million lightyears

 

Please get straight on what you want to ask about, and clarify the question.[/quote']

 

 

Good Point! That leads me to ask the question what about our own solar system? We get a few rovers on mars and all of the sudden its lets take a joy ride around the universe. I think that we should start with getting back to the moon myself. You don't see infants jumping out of their cribs to run marathons do you? Lets take it one step at a time and not get ahead of ourselves.

 

I will add that I would like to see travel to other galaxies happen.