|MadSci Network: Physics|
Hello William. A couple months ago I found this article on future space travel - http://www.strangehorizons.com/2004/20041115/orbitalodd-a.shtml You might find some of the ideas work for your story. The reason we launch rockets the way we do is because we know it works. It's a proven method. But it's certainly a slow one. Here are some random thoughts on alternative methods, written in no particular order. Hopefully some of them will be of help. Imagine a giant gun, maybe a barrel length of 20 miles, buried deep in the earth with only the tip exposed to the surface. A fireproof disk sits at the bottom, and a spacecraft sits on the disk. Every quarter mile or so inside this barrel is an explosive charge. When the explosive charge beneath it detonates, the spacecraft is forced upwards. Each time the spacecraft passes a charge embedded in the barrel, that charge detonates, too. The back pressure becomes enormous as the spacecraft gets closer to the surface. It is fired into orbit the same way a bullet is fired from a gun. The big advantage - the spacecraft doesn't need to expend any fuel to escape the earth's gravitational pull. The big drawback - the g forces would kill any passengers and destroy all but the heartiest of spacecraft. So let's modify the gun a bit. Instead of explosives powering the motion, let's use magnetics. We'll need a longer barrel this time, maybe 200 miles long. It would have to be built on the surface of the earth, not buried. We can angle the last few miles of it up at a slight angle. And instead of explosive charges every quarter mile, let's use an electromagnet every 2 inches. What we have now is kind of like a magnetic bullet train, except we're using it to push something much lighter than a train so we can accelerate it faster. The spacecraft starts at one end of the barrel, with all the electromagnets pulling it. As it passes the electromagnets, they switch polarity, pushing it away instead of pulling it forward. Over 200 miles the spacecraft could build up enough velocity to escape the earth's gravity, and do it smoothly enough that the g forces are easily within human tolerances. Such a device could be built near the equator and used to launch spacecraft towards the moon. It wouldn't take much fuel to adjust the direction of travel enough to slingshot around the moon and aim for anywhere in the solar system we want to go. Again, the big benefit is not having to lug around enough fuel to escape the earth's gravity. The drawback is that it limits the size of the cargo. The mass of the cargo is proportional to the length of the barrel. Now let's combine the escape velocity of this system with a constant thrust. Rockets don't use constant thrust. They use enough thrust to escape the gravity pull of the planet they're leaving, then they coast to their destination. But we want a speedy trip to Mars, so let's look at constant thrust. Many different systems would work. Hydrogen fuel cells, atomic reactors, solar collectors, just about any existing way to generate power with low fuel requirements could provide a slight acceleration up to the halfway point of the trip, then a slight deceleration on the other side. Goodbye weightlessness, hello Guiness Book of speed records! We could build such a launching barrel on the moon. From there we could obtain some really staggering speeds because of the lower gravity and lack of atmospheric drag. The spacecraft could be launched towards earth, then use our planet's gravity to slingshot to its real destination. Of course, the immediate drawback that comes to mind is a malfunction or sabotage that causes the spacecraft to smash into the earth. Maybe having a moon based gun pointing at earth isn't such a good idea after all. Scratch that. There's some fascinating work being done with teleportation down in Australia. http://news.bbc.co.uk/1/hi/sci/tech/2049048.stm What Dr. Lam and his collegues have done might someday lead to a Star Trek transporter. It's certainly possible. But the task of identifying, cataloguing, and replicating every single sub-atomic particle in an object then reconstructing it somewhere else would probably take longer than a traditional ballistic trajectory flight to Mars and back. We're already approaching the upper end of computing speed due to that pesky little law stating nothing can move faster than the speed of light. But if we somehow can find a way to increase computer speeds a trillion times faster than they work now, then maybe identifying and replicating all the components of an object through quantum entanglement will give us useable teleportation. This field is in its infancy, and it's as hard for me to envision what will become of it as it would have been for Ben Franklin to envision modern electronics after watching lightning strike his kite. Anyway, let's get back to Mars. If we land our spacecraft on Mars, we're stuck facing the same problems we've already solved getting here, i.e., how do we all go home when we're done? NASA solved this one beautifully with the Apollo missions. Leave the space craft in orbit, where it retains all its velocity. And drop a lander to the surface instead. That way the lander only needs to carry enough fuel to escape and rendevous with the orbiting spacecraft, and on Mars, that's not a lot of fuel. About the window of opportunity - sometimes Mars is pretty close to us. Other times it's on the other side of the sun. So sometimes the trip is going to take about five times as long as it would at other times. Nothing except teleportation is going to change that. Good luck with the story. If you have any more questions about any of these alternative ideas or want to discuss one of two of them in depth, please let us know. Layne Johnson
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