Lecture.14 - AE 1350 Lecture#14 Introduction to...

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AE 1350 Lecture #14 Introduction to Astronautics
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Astronautics is a broad field It includes a study of Payload Design and Integration (e.g. satellites, space lab, Mars rover, etc.) Mission Design and Analysis (Selection of Trajectories) Launch Vehicle Design and Analysis (Rockets, space shuttle, X- vehicles, etc.) Reentry Systems Here, we will briefly look at rockets as launch vehicles, and some simple missions.
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Rockets Thrust depends on two factors: rate at which momentum leaves the rocket through the nozzle – Exit pressure p exit • T = -dm/dt V jet + (p exit -p atmosphere ) A exit • In well designed rockets, p exit = p atmosphere • T = -dm/dt V jet Notice the negative sign. The mass m of the rocket decreases. dm/dt is thus a negative quantity. V Jet
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Velocity of the Rocket From the previous slide, Thrust T = - dm/dt V jet This thrust is used to accelerate the rocket, and the payload it carries. From Newton’s second law, m dV/dt = T = - dm/dt V jet We can write the above equation as: dV = - V jet dm/m Integrate : V rocket = V jet log e {m start /m end }
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How can the velocity of the rocket be maximized? From the previous slide: Change in the speed of the rocket (and payload it carries is given by): V rocket = V jet log e {m start /m end } We must increase mass of the rocket at the start by loading it up with fuel. We must decrease the mass of the rocket at the end of each stage or leg of the the mission by discarding used up stages of the rocket.
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Single Stage vs. Multistage A multi-stage rocket discards earlier stages as soon as they are used up. This decreases mass of the rocket and the end of each
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This note was uploaded on 08/17/2011 for the course AE 1350 taught by Professor Johnson during the Spring '07 term at Georgia Tech.

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Lecture.14 - AE 1350 Lecture#14 Introduction to...

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