On the feasibility of putting fuel sources in LEO

[eternalsky]

I actually wrote an article on this Idea many weeks back. If anyone cares to check it out

http://spacecompanynews.com/2009/07/can ... -a-profit/

its basically about how we can profit from the moon, and one of the idea's I suggested is that although we would travel to the moon to mine a valuable resource such as platinum. We would eventually be able to produce rocket fuel at the same time, in order to cut costs, and increase potential profits.

The premise of the space fuel depot is that it takes as much fuel to get into LEO than it does to get into GEO. Therefore placing a fuel depot in low earth orbit, like where the space station is, we can essentially cut the costs of fuel in half, for travel to the moon, if not more.

 

[Crossover_Maniac]

There is plans to build an extremely cheap ELV called Aquarius. It sacrifices reliability for cost based on the idea that paying $1 million for a launch vehicle that has a 1 in 3 failure rate makes more sense than $10 million for a launch vehicle with a 1 in 20 failure rate if the cargo is cheap consumables like fuel, water, air, and food. Something like Aquarius would make it worth while to have an orbital fuel depot.

 

[geremiah]

E=mc2 Is actually E=m2 the speed of light varies from gravitational forces, our solar system does generate gravitational forces on particals. Emagine what if there was one force" the source" that imposed on light instead of a whole system of planets and debris, it would certainly travel faster. HHHHHMMMM. To a degree!
Black holes are evidently considered not to let light travel because they impart forces that are greater than to photonic travel and what esle?
What if? Is what I say. Energy is limitless, hydrogen is abundant and it will take a few plenty long millenia before it runs out. Then it will turn to something else from decay, whatever the composition of the star wherever it is, but it is limitless
What I am saying is that instead of wasting resources launching craft into the void. Lets squeeze the resources if we are spending millions of dollars on launching every bit thought into the craft could be used. The tech we have now is well sufficient for it. Stop wasting resources. Space is definetly a green place. Hydrogen is the best possible method of fuel in the universe. If not, mabe Baryons.

 

[geremiah]

Launching from gravity can impose energy problems but a gravityless environment can allow for usefull resources mabe like VASMIR to prosper. Protons are abundant for something like this to work once in space of course.

 

[aremisasling]

The short answer is no.

The Earth is a massive gravity well. Sending anything up is expensive and should be done with thought. Right now it costs from $3,000/lb to $10,000/lb to get things to orbit (depending on type of orbit). Fuel is very heavy and you can imagine filling your space ship up is going to cost and arm and a leg and several internal organs as well.

Most of the fuel a ship needs is gobbled up in getting into orbit. You really dont need that much fuel to do deep space exploration. What you really need for deep space human exploration is an RTG (Radioisotope thermoelectric generator) in your space ship. This will produce all the heat your ship will need to stay warm and you can use some of the heat to generate electricity and use that to propel yourself in space. You dont need massive fuel tanks.

Big fuel depot's in space is a bit sci-fi to me. I think that will only happen in sci-fi movies (usually followed by massive explosions).

EDIT: Getting my technologies straight.

RTG's aren't a propellant source, they are only an energy and heat source. As such, they wouldn't replace chemical rockets and their radioactive nature makes them undesirable for powering manned spacecraft applications. They may be useful as power sources for VASIMR or similar ion propulsion technologies, but you'd still need a fuel source. Electricity is not a propulsion system in and of itself. Most electricity-driven engines, such as ion engines, are slow to accelerate, making them impractical for lunar trips. Moon bases may be a good use as they could be put farther away from the astronauts, but their low efficiency and low output makes them not a particularly good candidate for that either. Earth orbital satellites and interplanetary spacecraft would be good applications and indeed ion propulsion is currently used for exactly those sorts of missions. But again, having a highly radioactive power source on board limits it's usefullness for manned spacecraft.

On the other hand, your argument works nicely for a fuel depot or at least fuel rendezvous point for a VASIMR or other ion engine that could be powered by an RTG. In fact, the fuel pellets might be a nice fit for a fuel depot application as generally the best radioactive decay fuels are pretty heavy. Float a couple of spare plutonium pellets up there and you've got fuel sources for the next few dozen missions and refills for earth-orbiting spacecraft that need a freshening up. It would also cut down on the total number of launches of nuclear material and offer the opportunity to launch on trajectories that limit their crossing of sovereign territories with a tug to transport the fuel to the spacecraft.

As for your first argument, it actually makes very little sense. If it takes more fuel to get out of the gravity well than to travel around once you're up there, I would expect the gains in having a large dedicated fuel source launched solo for both transitory spacecraft and LEO station-keeping operations would be enormous. In the event of a space-tug style operation, the spacecraft in question is already orbital. Launching supplies in a dedicated fashion would appear to me to be very beneficial in that case. It seems like you are arguing for the other side to me.

 

[aremisasling]

E=mc2 Is actually E=m2 the speed of light varies from gravitational forces, our solar system does generate gravitational forces on particals. Emagine what if there was one force" the source" that imposed on light instead of a whole system of planets and debris, it would certainly travel faster. HHHHHMMMM. To a degree!
Black holes are evidently considered not to let light travel because they impart forces that are greater than to photonic travel and what esle?
What if? Is what I say. Energy is limitless, hydrogen is abundant and it will take a few plenty long millenia before it runs out. Then it will turn to something else from decay, whatever the composition of the star wherever it is, but it is limitless
What I am saying is that instead of wasting resources launching craft into the void. Lets squeeze the resources if we are spending millions of dollars on launching every bit thought into the craft could be used. The tech we have now is well sufficient for it. Stop wasting resources. Space is definetly a green place. Hydrogen is the best possible method of fuel in the universe. If not, mabe Baryons.

I will note that I'm only commenting here for my own amusement and the amusement of others.

Aside from the crazy nature of this post, the E=mc^2 equation is not invalidated by the change in the speed of light itself. c in Einstein's equation is a representation of light's speed when unhindered by its medium. c is kind of like horsepower. 1 horsepower is roughly equivalent to the power of 1 horse. The existance of faster and slower horses doesn't innately increase the power of a car engine because it is measured in horsepower. If that were the case, our cars would become more or less powerful depending on the power of the strongest living horse or the mean of all living horses. In short, it's a quantity, not a number pegged to measurements of specific instances of photons. Furthermore, unless you can demonstrate that c=1, you can't just cancel it out like that. It violates basic principles of algebra.

Hydrogen, which is already used as a fuel source for rockets, doesn't generate energy in and of itself unless it is destroyed. If you can come up with an effective way to annihilate a hydrogen atom, there are some folks in governments around the world that would love to talk to you. As for energy, sure there's lots of it. It's collecting it that's the issue. The absolute best power source in the solar system is the sun, and we collect its energy regularly. But we are only moderately efficient at doing so. Again, if you have a solution to the problem, build it, sell it and retire a rich man.

And for the record, Baryons = normal matter. In other words, when you are lighting a match, you are using Baryons. When you eat a doughnut, you're body derives energy from its Baryons. When a rocket lifts off, nuclear, chemical, ion, or otherwise, it's deriving its energy from Baryons. Light bulb? Baryons. Nuclear reactor? Baryons. AA battery? Baryons. Etc.

We currently have no non-baryonic methods of producing energy. Though your proposal does inspire some ideas for mischief along the lines of the various tongue-in-cheek attempts to ban Dihydrogen Monoxide.

Edit: oh yeah, and stars are made of hydrogen. The biproduct of stars is Helium and larger elements. Since hydrogen is one of the most abundant elements in the universe, we won't ever run out of it. But to do what the sun does, we need to create controllable and sustainable fusion which we don't currently know how to do. Though we are a lot closer than we ever have been, having now created reactors that can generate positive outputs for brief periods, we've still got a long way and a lot of money to go before we've got one that is scallable or economically feasible.

Aremis