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York University
Natural Science
NATS 1880
Paul Delaney

Interstellar travel is difficult because (i) Distance (ii) Energy (iii) Technology (i) Distance -Very large distances -Most distant planetary probes (PIONEER 10 & 11 (has plaques for ET) -- VOYAGER (1and 2) (has complicated messages such as pictures and messages) have travelled 8-120 AU. - Alpha Centuri (The nearest star to sun) is about 2,700 AU; 4.4 light years away. -Speed/Cosmic Speed Limit (c=300,000km/s) according to Einstein’s theory of relativity. (ii) Energy -dependant on object’s (mass and speed ) 2 -Star-ship with few thousand people would have mass of 100 million kg; and if moved 10% at speed of light would take 40 years to reach nearest star. -Energy would be 100X the world’s current annual energy use. -Would take about 2.5 Quintillion dollars (about 400,000 times the world’s current GDP) -As the ship speed increases, mass increases, and requires greater Energy for acceleration. (iii) Technology -Newton’s 3 Law of Motion (Conservation of Momentum) “For Every Action there is an opposite and equal reaction”. -A rocket vaporizes on-board fuel at the back which moves the rocket forward -Can work in a vacuum of space (unlike jet or aircraft) -Concept of Rockets [ Tsiolkovsky (Russia) , Herman Oberth(Germany) ,Goddard (USA) ] M=mass after velocity Mo= Launch Mass V=Velocity attained Ve=Exhaust Velocity of gasses (Ve=~2-4km/s) -multistage rockets are used. -WWII German Rocket (V2) ; Soviet/Russian (Proton) ; America(Saturn V); used to carry Apollo Astronauts to the Moon, the most powerful rocket yet built. Chemical Rocket: uses the energy binding electrons to the nucleus Nuclear-Power Rocket: EFFICIENT) Nuclear energy of 1kg of matter= Chemical energy from 8 billion liters of gasoline Nuclear Fission: involves splitting of the large nuclei into parts (uranium and plutonium) Nuclear Fusion: efficient) 0.07%of mass is lost to energy; results in unprotect waste, needs a special fuel source 0.7% of mass is lost to energy; not dangerous waste; uses -PROJECT ROVER (1955): Project on using nuclear energy to power spacecraft. -NASA cancelled the mission to send manned mission to Mars in 1973. -PROJECT ORION (1960s): was the first real starship and was propelled by mini-nuclear bombs detonated just behind the rocket. -PROJECT DAEDALUS (1970s): used the nuclear fusion for propulsion . (Could reach 10% speed of light) ION ENGINE: could be used instead of chemical or solid fuel. It emits charged particles as exhaust and has very high exhaust velocity. It has continuous acceleration. (Could reach 1% of the speed of light) SOLAR SAIL: very thin sail, that could accelerate a craft through radiation pressure from a star. -inexpensive (could reach a few percentage the speed of light and then coast to target) Limitations: solar intensity decreases with the distance. INTERSTELLAR ARKS: conventional technology to reach to nearest stars. Limitations: Would require large crew. Humans cannot hibernate, great leaps in medicine and sociological effects. INTERSTELLAR RAMJETS: Interstellar space contains some hydrogen. This ship can scoop this hydrogen as a fuel and can expel to high velocity. Limitations: (i) The scoop would have to be hundreds of km across to collect sufficient fuel (ii) The impact of any debris at near light speed could destroy the ship. Time Dilation: As speed increases; Time slows down (relative to Earth) v=speed at which the rocket is moving c=speed of light -While time slows down it causes the length and distances to contract called “Length Contractions”. There are two twin brothers. On their thirtieth birthday, one of the brothers goes on a space journey in a superfast rocket that travels at 99% of the speed of light and comes back after a year for his 31 birthday, the other brother will be 37 years olTime is stretched by factor 7. People on Earth would have aged NORMALY. Time elapsed for people travelling near th
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