# Interstellar travel

Post on 17-Jul-2015

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<ul><li><p>INTERSTELLAR TRAVELName:Amit samrat mauryaBranch: ECE 3rd year</p></li><li><p>Motivation: Fermis ParadoxIf the chances of developing a technological civilization are 1 in a million:100,000 civilizations in the galaxyThis is an application of the Drake Equation, but ignoring the Lifetime of civilizationsIf these are spread over the lifetime of the Galaxy, the time between civilizations is about 50,000 years</p></li><li><p>Fermis ParadoxWith such a long time, a civilization might be able to colonize the Galaxy or at least make its presence knownThey could at least send self-replicating machines</p></li><li><p>Solutions to Fermis ParadoxThere are three solutions to Fermis Paradox:We are aloneA galactic civilization exists, but it remains hidden from usOther civilizations exist, but none have colonized the galaxy. Why?No interest in doing soSelf-annihilationTechnological difficulties</p></li><li><p>IntroductionIn order to travel to the stars, colonize other worlds, and establish an Everlasting Galactic Empire, we will need interstellar travel</p></li><li><p>Rocket ScienceCurrent rockets use chemical fuelsThese can be solids, liquids, or gasesEfficiency of a rocket measured with the mass ratio = Mass with fuel / Mass without fuel</p></li><li><p>Rocket ScienceTo escape the gravity of the Earth need a mass ratio of ~39Single stage rockets have mass ratios of ~15 or lessThis is not enough, so we cant leave the EarthOr can we?</p></li><li><p>Multistage Rockets</p></li><li><p>Distances to StarsThe nearest star system (Alpha Centauri) is 4 light-years away (40 trillion km)At 60mph, this would take 44 million yearsAt 17,000mph, this would take just 160,000 yearsAt this speed, it would take a billion years to reach the center of our Galaxy</p></li><li><p>What can we do?We need to go faster!Its all a mater of getting higher efficiency from our fuelI can make 0.5 past light speed!</p></li><li><p>Nuclear RocketsUse fission to heat hydrogen gas, which provides the thrustFuse small pellets of hydrogen, the energy released moves it forwardSet off a nuclear bomb behind you</p></li><li><p>Ion DrivesShoot out ions from light-weight gasesLittle thrust, but can work for longer times and therefore get large velocities</p></li><li><p>Solar SailsUse the pressure from photons of light to push the craft forward- like wind on a sail.Can also use lasers</p></li><li><p>Antimatter is like regular matter but with opposite chargeWhen antimatter and matter meet, they completely annihilate each other producing energyAntimatter Engines</p></li><li><p>Like the solar sail, an interstellar ramjet carries no fuelTake hydrogen from space and fuse itRamjets</p></li><li><p>To Infinity, and Beyond!These new technologies allow light-weight space craft to reach very high speeds with very little fuel.In order to go faster we just need to run the engine for a longer time</p></li><li><p>But then this guy came alongImage credit: Kevin Hainline</p></li><li><p>A Maximum SpeedThe speed of light in a vacuum is always a constant with respect to any observer.This speed, c, is300,000 km/s186,000 miles/s1.8 terra furlongs/fortnightNothing can travel faster than light</p></li><li><p>Special RelativityAll motion is relativeMany weird effects will happen when special relativity is applied, but Ill only mention a few:Moving clocks run slower as seen by a stationary observer time dilationDistances are contracted along the direction of motion of a moving object length contraction</p></li><li><p>Special RelativityAt 99.99% of c, to go to Vega (25 light-years away) and back:Space ship frame: 8 monthsEarth (stationary) frame: 50 yearsBut light takes 50 years to travel 50 light-years, yet you do this in 8 months:Length contraction: you travel 0.4 light-year rather than 25 light-year</p></li><li><p>General Relativity to the Rescue?</p></li><li><p>WormholesA highly curved region of space could intersect another region of space and form a hole between themThese wormholes are unstable and collapse if anything goes through them</p></li><li><p>The Alternative: Interstellar ArksUse conventional technology, but be prepared to wait a very long timeThe original travelers will die and new ones will be born before reaching the destinationOr you could place everyone in suspended animation for thousands of years</p></li><li><p>Questions?</p><p>********A multistage rocket is built of parts, when the fuel runs out in one part it gets ejected. This reduces the mass, which means it is easier to accelerate the remaining stages.****Have been around since 1960sUsed in Deep Space 1 (1998) for 16,246hours and has consumed about 72kilograms (continuously for 4800hrs ~ 200days)The ion propulsion system enabled the spacecraft to close in on the comet Borrelly at a rate of 750,000 miles per day.It only consumes about 3.5 ounces (100 g) of Xenon per day.*Cosmos 1 (2005) failed to reach orbit [this was a private project]Doesnt need to carry fuelSails must be very thin (low mass compared to craft)Small ones have been testing in vacuum chambers and used in some satellites*Approximately 10 grams of antiprotons would be enough fuel to send a manned spacecraft to Mars in one month.H Fusion: 0.7% of mass to energyAntimatter: 100% of mass to energy*****You cannot tell if you are moving at a constant speed or stationaryIn order to move at the speed of light, you would need to apply an infinite amount of energy since the object would be infinitely massive**In these images, physical space is 2D.The curved space is in an additional dimension that we cannot perceive*The distance through a wormhole is much less than the physical distanceIf set up correctly, you could enter one wormhole reach a distant star then get on another wormhole and return to Earth BEFORE you left*Generation-ship vs. Sleeper-ship*</p></li></ul>

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