Your final semester project papers are due in ONE WEEK, Thu April 28th (last day of class). Please return your marked-up First draft.

Transcription

1 The Home Stretch Your final semester project papers are due in ONE WEEK, Thu April 28th (last day of class). Please return your marked-up First draft. Final Exam: 12:30pm, Friday May 6th, 2hrs. Any homework/drafts/etc. you still have not turned it, do so immediately!

2 Getting to the Stars Space Flight

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4 History of Spaceflight The three Fathers of Spaceflight: 1903 Konstantin Tsiolkovsky The Exploration of Cosmic Space by Means of Reaction Devices 1919 Robert H. Goddard A Method for Reaching Extreme Altitudes 1922 Hermann J. Oberth By Rocket into Interplanetary Space

5 History First rocket to reach space: V2 (German), Oct. 3, 1942 First artificial orbiting satellite: Sputnik 1, Oct. 4, 1957, launched by USSR First human spaceflight: Vostok 1, Yuri Gagarin, launched by USSR on April 12, 1961 First humans land on the Moon: Apollo 11, Neil Armstrong and Eugene (Buzz) Aldrin, July 20, 1969 First soft landing (unmanned) on another planet: Viking 1 lands on Mars, 20 July, 1976

6 Hard Impacts Luna 2, USSR, crashed into moon Sept 13, 1959 Venera 3, USSR, crashed into Venus, Mar 1, 1966 Mars 2 Lander, USSR, crashed into Mars Nov 27th, 1971

7 Images from Venera Radar mapping

8 Rocket Propulsion Rocket: A device that can apply acceleration to itself by expelling part of its mass at high speed in the opposite direction. This change in momentum does not need anything to push on (like the air). v = v exhaust ln( m 0 m 1 )

9 Velocity To put a satellite in low- Earth orbit To escape Earth s gravity To escape the sun s gravity (leave the solar system): 7.8km/sec 11.2km/sec ~42 km/sec Typical velocity of exhaust: 4km/s. Thus m0/m1 ~ 7, 16, 36,000 for these three cases!

10 The problem There are no re-fueling stations where you are going. If you are using combustion of fuel (a chemical rocket), you need to take all the propellant and oxidizer you ll need for your trip. Most of the mass of the rocket at launch is fuel!!! Using stages which separate helps somewhat.

11 Types of Propulsion Chemical Propulsion: Burning Stuff. The exhaust velocity increases with temperature: hotter burn temperatures. Thus far, our only successful method to lift rockets from the Earth.

12 Example

13 Example

14 Stages

15 Types of Propulsion Ion Drive: Accelerate charged particles using electric fields. Tested in space (using Xenon atoms), but far too weak to lift off Earth!

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18 Types of Propulsion Nuclear Propulsion: Instead of heating by combustion, heat using a small nuclear reactor. Used for submarines. Some concept designs for pulsed nuclear rockets: a stream of nuclear detonations just behind the rocket. Concerns from Fallout have mostly killed this class of propulsion.

19 Types of Propulsion Fusion Drive: Use fusion instead of fission, controlled microexplosions could yield exhaust speeds of 12% the speed of light!

20 Types of Propulsion Photon Drive: Sending out a powerful beam of light would give you exhaust velocity the speed of light. Problem: no way to make it.

21 Types of Propulsion Space Sails: Ultra light reflective sails can get pushed by the sun s radiation, or perhaps groundmounted lasers. Several test in space: recently the NanoSail-D orbited the Earth. Low Thrust. Useful for cleaning up junk in Earth orbit?

22 Types of Propulsion Warp Drive: Sadly we haven t invented yet.

23 Living in Space Space is a hostile environment. Cosmic rays cause damage at the cellular level. Weightlessness causes rapid degradation of musculature. Life support systems are the dominant part of the cost and weight budget.

24 Getting There: Optimistic Suppose we identify a perfect, habitable Earth-Like planet 100 lightyears away (optimistic). we invent a super-rocket which can accelerate at the comfortable rate of 1G all the way there. You very quickly approach the speed of light. It would take just over 100 years to get there, in Earth time. Thanks to time dilation, the trip would seem to you to have taken only 5.1 years!

25 Getting There: Realistic Suppose we have a rocket which can accelerate up to 100km/s (~100 faster than a speeding bullet), escaping the Sun s pull. Pioneer 10: 48km/s. It would take 300,000 years to get there. This is much longer than the timescale for humanity to have evolved from proto-humans!

26 The Waiting Game Suppose you design a spacecraft that gets you somewhere interesting in 100 years. 50 years later, someone will invent a spacecraft that can make the same journey in 25 years. You are better off waiting. Something like this logic is currently limiting our drive to return to the Moon or visit mars.

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28 Assignment Watch three short talks on human spaceflight: TED Blog 50 years of human spaceflight: A TEDTalks playlist Reminder: Final Project paper due in One Week (last day of classes). Two presentations left: Matt & Anas.