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replace satellites that have been destroyed. I can see some justification for it, but it sounds like it would be extremely expensive to do, and the replacement satellites could be destroyed by a second EMP or ASAT attack. It seems like it would be more efficient to try and find ways to stop the satellites from being destroyed in the first place.
So basically you are creating a theocratic government that worships ((5)^.5)+1)/2?
What would be the tactical and strategic significance of a military base on the moon? Are the moon's advantages enough to make the military favor a lunar base over other options?
It is not perfect, but usually you can understand what people are saying.
The moon holds the keys to the future of mankind's survival on earth. When the population reaches 10 billion by 2050, the moon's minerals will be ever more important.
What minerals does the moon have in abundance that are valuable enough for it to be profitable to mine them on the moon?
Further, the solar power collected on the moon will be vital to meeting the energy needs of mankind.
It would not make sense to use the moon to collect solar power for Earth unless the solar panels were produced on the moon with lunar materials, and there was an efficient way to transport the energy to Earth. Otherwise, satellites would be cheaper and more efficient. Even better would be to continue to use the Earth for solar panels; enough sunlight hits the Earth's surface to meet mankind's energy demands for a long time to come.
There are other isomers that should work besides hafnium-178. I read that 19 different elements were being investigated, and hafnium was just considered the one that seemed to work best.
I think producing any of the possible isomers would be pretty expensive though. Few of the isomers actually exist in nature, so we would have to make them with a particle accelerator.
Wow, we just invented a new propulsion method !!!
What should we call it? Nuclear Isomer propulsion?
Are there materials that can reflect gamma-rays? To use it as a reflector for the chamber?
I have read that gamma rays in the keV range can be reflected, but gamma rays in the MeV range cannot. I do not know the energy at which hafnium emits gamma rays.
I have found that while the Department of Defense believes in nuclear isomer bombs, some scientist are still skeptical about the claims of induced gamma ray emission. Hopefully the findings will be scientifically validated soon *crosses fingers*.
Energy is produced by the reaction, and converting that into thrust should not be too hard. Just let the gamma rays be absorbed by a material that turns into a plasma and pushes the spacecraft.
Thinking about this some more though, I don't think that it is even necessary to actually use bombs. Instead, gas containing hafnium-178m2 can be mixed with gas that absorbs the frequency of gamma radiation that the hafnium emits, but not the low energy X-rays that start the reaction. The mixture is then piped into a reaction chamber where it is hit by the low energy X-rays. The reaction occurs, and the superheated gas is directed out the back of the craft, creating thrust.
It seems that this could become a very efficient and effective method of propulsion. However, we need to improve our techniques for producing hafnium-178m2 or other unstable isomers before it becomes practical.
Interesting. It appears the bombs made with this technology would probably be more expensive and less powerful than conventional nukes. However, they have some advantages in that they can be made smaller, they produce less radioactive fallout, and they may avoid some of political consequences that go along with nukes. Has anyone looked at using this technology with and Orion type spacecraft?
I have read about an ISS module that is under development (called TransHab) that is inflatable. It is claimed that the new module will have much more volume than a conventional module, better protection against radiation, and better protection against micrometeoroids, all while being smaller and lighter to launch. I have read about plans that use inflatable habitats on mars, but has anyone ever considered making the interplanetary spacecraft itself inflatable? If it is an interplanetary craft (not used in atmospheric flight), and it uses a low thrust but high ISP propulsion, I do not see anything that would prevent an inflatable spacecraft from working. All of the advantages of inflatable spacecraft would be even more useful for an interplanetary craft than for a space station, so it would seem that inflatable is the way to go. The only disadvantage I have been able to find about inflatable spacecraft is that they are more expensive to produce. However, I think much of the expense comes from one-time development costs, so they should become cheaper as more experience is gained with inflatable technology.
But could it be made to work, if not exactly as I've suggested, then at least in some similar form?
I think it might work well for groups where most people know most of the other people, but I think that a large country would probably appoint 7 of the most famous celebrities, whether they are competent or not.
I think that the waves themselves do not oscillate. Instead they stay exactly the same and do not change with time. The space the travel through experiences an oscillation only because the portion of the wave that is in that space changes.
Relativity does have some affect at these speeds, but it is not enough to overwhelm the Newtonian equations yet. Most relativistic quantities are multiplied or divided by a factor of (1-v^2/c^2)^.5. For .33, this would come out to about 5% difference. Enough to have a measurable effect, but not enough to be too preoccupied with at this stage.
The real question seems to be, will it be a Ferrari or a slow golf cart.
Slow golf cart. But if you let it run for a long time, eventually you will be going at a very high speed.
If a 50mw nuclear generator can produce .33c.
If the initial mass of the spaceship is 1/3 and the particle accelerant is 2/3 the total mass.
It should be able to obtain a maximum speed of .22c ?
I think the relavent equation is velocity=exhaust velocity*ln(initial mass/final mass), which should give a final velocity of .36c.
Obviously for interstellar distances nuclear is the way to go.
And if no humans are on board then why not 100mw or 500mw?
Part of why I chose 50 Mw was becuase there is a thread in the New Discoveries forum about a "small" nuclear reactor that generates 50 Mw. The core is about 20m long, 2.5m diameter, and weighs 60 tons.
But if you reduce the thrust to say .02c, then the mw requirements also reduce proportionally.
I calculate that to produce thrust of .02c will require about 1mw or less?
Yes it reduces proportionally. So with an exhaust velocity of .02c, it would take (.02/.33)*50Mw = 3Mw to produce 1N of force.
Please excuse this intrusion into your discussion but I have a question for Euler:-
Just browsing through your equations and the example you gave at the end, I noticed that producing 1 newton of thrust appears to require less and less power as you reduce exhaust velocity.
This sounds counter-intuitive, at least to me!
What am I missing here?
Just because it seems counter-intuitive does not mean it is not true! The momentum of an object is proportional to its velocity, but the kinetic energy is proportional to the square of the velocity. If you throw a heavy object (e.g. a bowling ball) at a low speed, you will notice a significant amount of recoil. However, if you use the same amount of energy to throw a light object (e.g. a baseball) at a high speed, you will hardly notice the recoil.
Your particle accelerator engine works in a similar way to an ion engine, though ion engines usually use a short linear accelerator that does not accelerate ions above .001c.
The kinetic energy of the particles (and therefore the energy used to accelerate them) is equal to (1/2)mass*velocity^2. The momentum is equal to mass*velocity. Power is equal to energy/time, and force(thrust) is equal to the change in momentum/time. Therefore power/thrust = velocity/2. So if the exhaust has a velocity of .33c, it would require 50 Mw to produce 1N of force.
I bet the electricity bill will be nasty for this though
Yes. A high exhaust velocity means that the spaceship is fuel-efficient. However, it also means that more power is necessary to produce the same amount of thrust.
US population growth is driven primarily by immigration
Actually, immigration accounts for less than 40% of the population growth. The primary reason for population growth is still that more people are born than die.
Shoul we extend childhood too?
Childhood is being extended. A typical American today spends 7-8 more years being educated compared with 100 years ago. The average ages for first marriage and childbirth are also increasing.
The idea that vegetarianism is somehow better for "the planet" is absurd. First, the amount of farmland that would be required to feed the entire human population solely on vegetable matter is staggering. All that forest being cleared, all that water being diverted. What was that about destroying the planet?
I think the reasoning goes that because livestock are often fed food that is edible for humans, and because it takes several pounds of plant matter to produce 1 pound of meat, meat production is inefficient and necessitates more farms instead of less. There is some validity to this reasoning, though it does not apply to animals that graze in areas that cannot be farmed easily. I think that, while it does typically require more resources to produce meat than it does to produce plants, meat tastes better and is therefore worth the extra expense. Farm yields are increasing faster than population growth, while at the same time farms are taking up less space and require less labor, so I am not too worried about running out of food soon.
It does not matter if the ball bounces or rolls through a tube, it will still pushes the ship backwards when it changes direction. In a closed system, momentum is always conserved, so you cannot get thrust by throwing a rubber ball unless the ball leaves the spaceship.
When the ball bounces off the back of the spacecraft, it pushes the whole spacecraft backwards. This cancels out the gain in momentum from throwing and catching the ball.
Astronomers have calculated that the stars in a galaxy do not have enough mass to hold the galaxy together by themselves (according to the standard laws of physics). This has caused many scientist to search for "dark matter" that would explain why the galaxy does not fly apart.
WIMPs are Weakly Interacting Massive Particles. They are hypothetical particles that are difficult to detect, but which may have enough mass to account for most or all of the dark matter.
Some astronomers also are looking for MACHOs, MAssive Compact Halo Objects. These would be things like stray planets, burned out stars, and other large chunks of matter that do not emit much light. However, there do not seem to be enough MACHOs to explain most of the missing mass.
What has this to do with assisted suicide?
I live in Oregon, where doctor-assisted suicide is legal. However, it is only allowed in cases of terminal illness, in which the patient is sane and chooses suicide. This case would certainly not apply, both because the patient did not choose suicide, and because the illness is not terminal. In addition, death by starvation is not an accepted method of assisted suicide.
This is not suicide at all, assisted or otherwise. If the website's claims about her not being a vegetable are true, than it really is murder.
Now Euler, about "the speed of gravity" controversy--are you willing to take that on. Be great if you did.
I will try to sort out the speed of gravity thing. However, it seems to be a lot more complex than the solar sail controversy, so I may not be able to come up with convincing evidence for either side.
I do not believe that professor Gold?s claim has any validity, and frankly I am surprised that such a notable physicist would make such a claim. As I have said, the motionless mirror would accelerate at roughly the same rate that a moving mirror would accelerate at (for velocities not close to c, at least). It works just like any other elastic collision.
Professor Gold seems to be mixing up kinetic energy and momentum. He seems to think that the acceleration of the spacecraft is proportional to the amount of work done by photons (as evidenced by the redshift). This logic is faulty. Work (energy) is equal to force times distance. Because the stationary mirror is not moving relative to the sun, there is no change in distance, and therefore no work done. However, there is still a force acting on the sail and therefore it will still accelerate.
The pressure of sunlight has been measured and it is significant enough that it is already a factor when computing the trajectories of interplanetary spacecraft. I see no theoretical obstacles preventing solar sails from working.