Ponce
3rd May 2015, 02:09 PM
I have been working on my "space fuel" for some time.....why look for something new when what's is already there could (could) work?...vacuum is negative and oxygen is positive....I believe that the vacuum in space itself can work as the needed fuel combined with a drop of oxygen per X? miles, oxygen that can be created onboard......in my mind I can see it working but I need a big container where I can experiment without blowing up a whole city block..........I know, I know, but is only who I am.
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Interstellar Space travel is really difficult!
http://nathangeffen.webfactional.com...fficulties.php
Interstellar Space travel is really difficult!
Dozens of interplanetary spacecraft have been launched. All of them are unmanned. The furthest travelled is Voyager 1. Although Voyager is now considered to be nearing the edge of our solar system, it is still less than 17 light hours from earth. That is less than one two thousandth of the way to our nearest stellar neighbour, Proxima Centauri. It has taken Voyager almost 35 years to get where it is. At that stately pace, it will need about 70,000 years to travel the equivalent distance to Proxima Centauri.
Interplanetary space travel is hard. Manned interplanetary space is very hard. Practical unmanned interstellar space travel is really, really difficult. And manned interstellar space travel is so difficult that it might never be achieved.
Here are some of the massive technological problems that have to be overcome if we are to send a manned spacecraft to another star, say Proxima Centauri which is a mere 4.2 light years from earth.
Doing a one-way trip in a lifetime
To make this as easy as possible, let us say at some point in the distant future, we will fly two young intrepid adventurers on a one-way trip to Proxima Centauri. They're prepared to spend a very long time doing it and they accept they will never return to earth.
To get there in a reasonable time, they are going to have to accelerate constantly for much, most or all of the first half of the journey. Then to ensure they don't overshoot Proxima Centauri when they get there, they have to decelerate during the second half of their journey, essentially mirroring the first half.
Ideally they would like to accelerate at 9.8m/s2, or 1g for the first of the journey. This exerts the same force on the astronauts that they experience from gravity on earth. Then they will decelerate at the same rate for the second half. The advantage of accelerating at exactly 1g is that if the spacecraft is designed so that our astronauts, when standing, are parallel to the direction the spacecraft is moving, they will experience earth-like gravity.
To see how this works out, open the space travel calculator. In the Distance field, enter "pr" to bring up Proxima Centauri and select it. The number 39734219300000000 is filled in for you in the distance. You will probably find the number displayed more intuitive if you change the units to light-years in the adjacent select box. Leave acceleration as is. Click Calculate. By selecting the appropriate unit measurement, you can now see that the maximum velocity, which our astronauts will achieve half way through their journey, is approximately 95% the speed of light. From an observer on earth's timeframe it takes our astronauts 5.8 years to reach Proxima Centauri. But Einstein's theory of relativity tells us that it will only be 3.5 years from the astronauts perspective, because the faster you go, the more time slows down for you. Run the animation to get a very simplistic view of what happens.
That all seems very promising. But sadly there's a great big glitch. The Wikipedia article on space travel using constant acceleration gives this excellent analogy: "Imagine a horse strong enough to pull a wagon carrying enough hay to feed it on a journey from New York City to Los Angeles." Clearly no horse would be able to carry all the hay it needed. Likewise no spacecraft can carry all the fuel it needs to get to Proxima Centauri at a constant acceleration of 1g.
The Spacecraft mass at launch field represents the total mass of the spacecraft at takeoff. The default mass of the spacecraft on the calculator is 2 million kg which is the approximate weight of a space shuttle at take-off, including its rockets and fuel. Our spaceship will be powered using hydrogen into helium nuclear fusion. This is orders of magnitude more efficient than any other rocket fuel in existence. Although the technology to make nuclear fusion bombs is available, controlled nuclear fusion for the purposes of powering a spacecraft is still science fiction. The space calculator's default fuel conversion rate (0.008) assumes we are using nuclear fusion.
The calculator tells us that the energy needed for the journey is a bit less than 780,000 exajoules. Now consider that in 2008, world energy consumption was a mere 474 exajoules and you realise we have a wee problem. Also note that the mass of the fuel you need is several orders of magnitude greater than your total take-off mass, which is impossible. In our horse analogy, the weight of the hay is so great, that the extra energy the horse needs to eat to carry it means it will end its journey from New York far short of Los Angeles (of course the horse wouldn't even be able to start walking because the hay weighs so much, but actually if our spacecraft was launched from space where there was no gravity or air friction, our spacecraft would move, but it would run out of fuel long before it reached half-way to Proxima Centauri).
A legitimate complaint is that the space shuttle would weigh a lot less at lift-off if nuclear fusion instead of current rocket fuel technology was used. But this doesn't solve our problem. The mass of the Endeavour space shuttle orbiter at lift-off is 110,000kg.
So enter 110,000 in the Spacecraft mass at launch field (make sure the unit field is kilograms) and click calculate again. Now you need 43,000 exajoules and your fuel still weighs many more times than your maximum launch weight. You see, no matter how you manipulate the maximum weight of the spacecraft, you will always need many times more kilograms of fuel than this maximum weight. It is therefore impossible, carrying nuclear fusion fuel or any current fuel in existence, to get to Proxima Centauri at 1g.
Is it possible to imagine a more efficient fuel than nuclear fusion? Will that help?
The famous E=mc2 equation tells us the maximum amount of energy you can get from a given mass. For nuclear fusion you get about 0.008 x mc2 joules, so there is significant room for improvement.
Antimatter rockets could in principle convert virtually all of their mass into energy. But these are not even on the technological horizon. Also, in practice 100% efficiency would not be achieved. But let's put that aside for a moment.
Click clear on the calculator. Then enter the distance to Proxima Centauri and replace the 0.008 fuel conversion rate with the number 1 (for 100% conversion of the mass of our fuel into energy). Now click calculate. Our astronauts still need more than 4.5 times as much fuel as their spacecraft mass.
We therefore have to conclude that using onboard fuel, it is theoretically impossible to get to Proxima Centauri. It doesn't matter what we set the spacecraft mass to, the ratio remains the same. So even for unmanned spaceflight a 1g acceleration to our nearest stellar neighbour is impossible.
Some means of space travel that don't use onboard fuel have been proposed, such as interstellar ramjets or beamed propulsion. The Wikipedia article on interstellar travel explains these in more detail. These proposed technologies are highly speculative.
So the only reasonable possibility is to reduce the spacecraft's acceleration and use much less energy. This means increasing the journey time. We can enter different values into the calculator for acceleration to iteratively find the right acceleration. Using nuclear fusion (i.e. a Fuel conversion rate of 0.008 1), our fuel finally starts weighing less than the spacecraft at the stately acceleration of 0.018m/s2. By comparison Usain Bolt accelerates several times faster than this when he runs the 100m sprint. But that's ok because Bolt gets tired after a few seconds, while our astronauts are going to continue accelerating for years building up massive velocity. At that acceleration it will take our astronauts just under 97 years to get to Proxima Centauri. Human life expectancy will therefore have to increase substantially before such a trip is feasible. It's also a one way trip, not merely because of mundane matters like the limits of human life expectancy, but also because our travellers don't have enough fuel to get back. If they do want to get back they are going to carry enough fuel to get there and back. They will also have to live an incredibly long time (at least 266 years) and accelerate at 0.0089m/s2. Their top speed will be about 6% of the speed of light.
There are further challenges:
Our travellers will have to spend their entire journey floating about in the weightlessness of space. This likely has adverse health effects over time. Alternatively gravity of 1g can perhaps be simulated by rotating the spacecraft. There has been serious research and progress on this, but it has not yet been achieved. See the Wikipedia articifial gravity entry.
Our travellers would need enough food for a lifetime. Assume our travellers can live on the equivalent of six cans of 150g corned beef and one litre of water a day. Since there are two of them, and they need this for 97 years, the weight of their food will be in the region of 135,000kg. 2 And that's before we consider water for washing. This is not very practical. Perhaps you could halve this by recycling the water, but that's still a lot of weight for a two-person journey.
The smaller and therefore the lighter the spacecraft the less fuel it will need. But our astronauts are going to be spending their lives on this ship, so they need something that's big enough for recreation, thereby increasing the size and weight of the spacecraft and increasing the fuel needed. Though perhaps with nuclear fusion this will not be too large a challenge.
The psychological stresses of living in space for one's entire life are immense and possibly insurmountable. What would our astronauts do with their days and nights? Well there aren't days and nights; which is itself a massive psychological stress. As romantic as space travel might seem, on the vast majority of 24-hour time periods on a 100 year journey the view out of the space ship window would be the same and monotonous, no matter how beautiful our travellers find the stars. The boredom would be unimaginable, except perhaps to people who have spent years in solitary confinement. Perhaps, as in science fiction movies, we will invent a way of keeping the human body in stasis, in which case they could "sleep" most of the journey and not age. They might find however that when they get to Proxima Centauri, there isn't much to get excited about, or if there is, there is not enough fuel left in their spacecraft to explore.
The space shuttle has fantastically complicated systems to maintain its atmosphere. Yet the longest space shuttle journey has been just under 18 days. We are a long way from building systems that can reliably maintain artificial conditions for life for a century.
There are surely many other difficulties I haven't considered. Manned interstellar travel seems a very distant dream at best. It might never be achieved. Unmanned interstellar travel on the other hand is a realistic future possibility, if we accept that the generation that launches the interstellar probe will not be the one that experiences the joy of that probe sending information on Proxima Centauri back to earth.
Another, not altogether far-fetched possibility, is that one day it will be possible to download the human brain, to something as small as a microchip, with durability of hundreds if not thousands of years. Perhaps if this is the future evolution of our species, we will be able to travel in this form to distant stars without being too concerned about the time it takes.
In the meanwhile, while we have our flesh and blood form, all is not doom and gloom. The solar system is a massive place with hundreds, perhaps thousands, of interesting objects to visit. We haven't fully explored the earth, so you can just imagine how much there is to explore on the nearest planets and moons. We're still a long way from being able to send manned vehicles to other planets, but it is feasible with enough investment.
Finally, when you consider how difficult manned interstellar space travel is and how inhospitable to sustained human life we know the planets and the moons in the solar system are, you realise that even the long term possibility of seeking permanent refuge for humanity in another part of space is minuscule. And then you realise how important it is that we don't mess up our current planet.
================================================
Interstellar Space travel is really difficult!
http://nathangeffen.webfactional.com...fficulties.php
Interstellar Space travel is really difficult!
Dozens of interplanetary spacecraft have been launched. All of them are unmanned. The furthest travelled is Voyager 1. Although Voyager is now considered to be nearing the edge of our solar system, it is still less than 17 light hours from earth. That is less than one two thousandth of the way to our nearest stellar neighbour, Proxima Centauri. It has taken Voyager almost 35 years to get where it is. At that stately pace, it will need about 70,000 years to travel the equivalent distance to Proxima Centauri.
Interplanetary space travel is hard. Manned interplanetary space is very hard. Practical unmanned interstellar space travel is really, really difficult. And manned interstellar space travel is so difficult that it might never be achieved.
Here are some of the massive technological problems that have to be overcome if we are to send a manned spacecraft to another star, say Proxima Centauri which is a mere 4.2 light years from earth.
Doing a one-way trip in a lifetime
To make this as easy as possible, let us say at some point in the distant future, we will fly two young intrepid adventurers on a one-way trip to Proxima Centauri. They're prepared to spend a very long time doing it and they accept they will never return to earth.
To get there in a reasonable time, they are going to have to accelerate constantly for much, most or all of the first half of the journey. Then to ensure they don't overshoot Proxima Centauri when they get there, they have to decelerate during the second half of their journey, essentially mirroring the first half.
Ideally they would like to accelerate at 9.8m/s2, or 1g for the first of the journey. This exerts the same force on the astronauts that they experience from gravity on earth. Then they will decelerate at the same rate for the second half. The advantage of accelerating at exactly 1g is that if the spacecraft is designed so that our astronauts, when standing, are parallel to the direction the spacecraft is moving, they will experience earth-like gravity.
To see how this works out, open the space travel calculator. In the Distance field, enter "pr" to bring up Proxima Centauri and select it. The number 39734219300000000 is filled in for you in the distance. You will probably find the number displayed more intuitive if you change the units to light-years in the adjacent select box. Leave acceleration as is. Click Calculate. By selecting the appropriate unit measurement, you can now see that the maximum velocity, which our astronauts will achieve half way through their journey, is approximately 95% the speed of light. From an observer on earth's timeframe it takes our astronauts 5.8 years to reach Proxima Centauri. But Einstein's theory of relativity tells us that it will only be 3.5 years from the astronauts perspective, because the faster you go, the more time slows down for you. Run the animation to get a very simplistic view of what happens.
That all seems very promising. But sadly there's a great big glitch. The Wikipedia article on space travel using constant acceleration gives this excellent analogy: "Imagine a horse strong enough to pull a wagon carrying enough hay to feed it on a journey from New York City to Los Angeles." Clearly no horse would be able to carry all the hay it needed. Likewise no spacecraft can carry all the fuel it needs to get to Proxima Centauri at a constant acceleration of 1g.
The Spacecraft mass at launch field represents the total mass of the spacecraft at takeoff. The default mass of the spacecraft on the calculator is 2 million kg which is the approximate weight of a space shuttle at take-off, including its rockets and fuel. Our spaceship will be powered using hydrogen into helium nuclear fusion. This is orders of magnitude more efficient than any other rocket fuel in existence. Although the technology to make nuclear fusion bombs is available, controlled nuclear fusion for the purposes of powering a spacecraft is still science fiction. The space calculator's default fuel conversion rate (0.008) assumes we are using nuclear fusion.
The calculator tells us that the energy needed for the journey is a bit less than 780,000 exajoules. Now consider that in 2008, world energy consumption was a mere 474 exajoules and you realise we have a wee problem. Also note that the mass of the fuel you need is several orders of magnitude greater than your total take-off mass, which is impossible. In our horse analogy, the weight of the hay is so great, that the extra energy the horse needs to eat to carry it means it will end its journey from New York far short of Los Angeles (of course the horse wouldn't even be able to start walking because the hay weighs so much, but actually if our spacecraft was launched from space where there was no gravity or air friction, our spacecraft would move, but it would run out of fuel long before it reached half-way to Proxima Centauri).
A legitimate complaint is that the space shuttle would weigh a lot less at lift-off if nuclear fusion instead of current rocket fuel technology was used. But this doesn't solve our problem. The mass of the Endeavour space shuttle orbiter at lift-off is 110,000kg.
So enter 110,000 in the Spacecraft mass at launch field (make sure the unit field is kilograms) and click calculate again. Now you need 43,000 exajoules and your fuel still weighs many more times than your maximum launch weight. You see, no matter how you manipulate the maximum weight of the spacecraft, you will always need many times more kilograms of fuel than this maximum weight. It is therefore impossible, carrying nuclear fusion fuel or any current fuel in existence, to get to Proxima Centauri at 1g.
Is it possible to imagine a more efficient fuel than nuclear fusion? Will that help?
The famous E=mc2 equation tells us the maximum amount of energy you can get from a given mass. For nuclear fusion you get about 0.008 x mc2 joules, so there is significant room for improvement.
Antimatter rockets could in principle convert virtually all of their mass into energy. But these are not even on the technological horizon. Also, in practice 100% efficiency would not be achieved. But let's put that aside for a moment.
Click clear on the calculator. Then enter the distance to Proxima Centauri and replace the 0.008 fuel conversion rate with the number 1 (for 100% conversion of the mass of our fuel into energy). Now click calculate. Our astronauts still need more than 4.5 times as much fuel as their spacecraft mass.
We therefore have to conclude that using onboard fuel, it is theoretically impossible to get to Proxima Centauri. It doesn't matter what we set the spacecraft mass to, the ratio remains the same. So even for unmanned spaceflight a 1g acceleration to our nearest stellar neighbour is impossible.
Some means of space travel that don't use onboard fuel have been proposed, such as interstellar ramjets or beamed propulsion. The Wikipedia article on interstellar travel explains these in more detail. These proposed technologies are highly speculative.
So the only reasonable possibility is to reduce the spacecraft's acceleration and use much less energy. This means increasing the journey time. We can enter different values into the calculator for acceleration to iteratively find the right acceleration. Using nuclear fusion (i.e. a Fuel conversion rate of 0.008 1), our fuel finally starts weighing less than the spacecraft at the stately acceleration of 0.018m/s2. By comparison Usain Bolt accelerates several times faster than this when he runs the 100m sprint. But that's ok because Bolt gets tired after a few seconds, while our astronauts are going to continue accelerating for years building up massive velocity. At that acceleration it will take our astronauts just under 97 years to get to Proxima Centauri. Human life expectancy will therefore have to increase substantially before such a trip is feasible. It's also a one way trip, not merely because of mundane matters like the limits of human life expectancy, but also because our travellers don't have enough fuel to get back. If they do want to get back they are going to carry enough fuel to get there and back. They will also have to live an incredibly long time (at least 266 years) and accelerate at 0.0089m/s2. Their top speed will be about 6% of the speed of light.
There are further challenges:
Our travellers will have to spend their entire journey floating about in the weightlessness of space. This likely has adverse health effects over time. Alternatively gravity of 1g can perhaps be simulated by rotating the spacecraft. There has been serious research and progress on this, but it has not yet been achieved. See the Wikipedia articifial gravity entry.
Our travellers would need enough food for a lifetime. Assume our travellers can live on the equivalent of six cans of 150g corned beef and one litre of water a day. Since there are two of them, and they need this for 97 years, the weight of their food will be in the region of 135,000kg. 2 And that's before we consider water for washing. This is not very practical. Perhaps you could halve this by recycling the water, but that's still a lot of weight for a two-person journey.
The smaller and therefore the lighter the spacecraft the less fuel it will need. But our astronauts are going to be spending their lives on this ship, so they need something that's big enough for recreation, thereby increasing the size and weight of the spacecraft and increasing the fuel needed. Though perhaps with nuclear fusion this will not be too large a challenge.
The psychological stresses of living in space for one's entire life are immense and possibly insurmountable. What would our astronauts do with their days and nights? Well there aren't days and nights; which is itself a massive psychological stress. As romantic as space travel might seem, on the vast majority of 24-hour time periods on a 100 year journey the view out of the space ship window would be the same and monotonous, no matter how beautiful our travellers find the stars. The boredom would be unimaginable, except perhaps to people who have spent years in solitary confinement. Perhaps, as in science fiction movies, we will invent a way of keeping the human body in stasis, in which case they could "sleep" most of the journey and not age. They might find however that when they get to Proxima Centauri, there isn't much to get excited about, or if there is, there is not enough fuel left in their spacecraft to explore.
The space shuttle has fantastically complicated systems to maintain its atmosphere. Yet the longest space shuttle journey has been just under 18 days. We are a long way from building systems that can reliably maintain artificial conditions for life for a century.
There are surely many other difficulties I haven't considered. Manned interstellar travel seems a very distant dream at best. It might never be achieved. Unmanned interstellar travel on the other hand is a realistic future possibility, if we accept that the generation that launches the interstellar probe will not be the one that experiences the joy of that probe sending information on Proxima Centauri back to earth.
Another, not altogether far-fetched possibility, is that one day it will be possible to download the human brain, to something as small as a microchip, with durability of hundreds if not thousands of years. Perhaps if this is the future evolution of our species, we will be able to travel in this form to distant stars without being too concerned about the time it takes.
In the meanwhile, while we have our flesh and blood form, all is not doom and gloom. The solar system is a massive place with hundreds, perhaps thousands, of interesting objects to visit. We haven't fully explored the earth, so you can just imagine how much there is to explore on the nearest planets and moons. We're still a long way from being able to send manned vehicles to other planets, but it is feasible with enough investment.
Finally, when you consider how difficult manned interstellar space travel is and how inhospitable to sustained human life we know the planets and the moons in the solar system are, you realise that even the long term possibility of seeking permanent refuge for humanity in another part of space is minuscule. And then you realise how important it is that we don't mess up our current planet.