IAC-04-A.6.02 - IAC-04-A.6.02 Design of Low-Thrust...

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1 IAC-04-A.6.02 Design of Low-Thrust Gravity-Assist Trajectories to the Outer Planets Chit Hong Yam, * T. Troy McConaghy, K. Joseph Chen and James M. Longuski § School of Aeronautics and Astronautics, Purdue University, West Lafayette, Indiana 47907-2023, USA A Nuclear electric propulsion engine is being designed for the Jupiter Icy Moons Orbiter (JIMO) mission. In this paper, we consider other missions—to the outer planets—that could be achieved with this propulsion system. We incorporate gravity assists at Venus and Earth to deliver greater mass (to Jupiter, Saturn, Uranus, Neptune and Pluto) than achievable with the JIMO engine alone. For example, we have found a trajectory to Pluto via gravity assist with Earth and Jupiter that launches in the year 2015 and rendezvouses with Pluto in 9.7 years. We also investigate the trade off in which final mass increases as the time-of-flight increases for three families of trajectories to Pluto (Earth-Earth-Jupiter-Pluto, Earth- Venus-Earth-Jupiter-Pluto and Earth-Venus-Venus-Jupiter-Pluto). Nomenclature a 0 = initial acceleration of the spacecraft, mm/s 2 g = standard acceleration due to gravity, m/s 2 I sp = specific impulse, s m ± = propellant mass flow rate, mg/s m f = final spacecraft mass, kg m 0 = initial spacecraft mass, kg P = power, kW R J = radius of Jupiter T = engine thrust, N V = hyperbolic excess speed, km/s V = magnitude of a change in velocity, km/s η = overall engine efficiency I. Introduction N ambitious mission to Jupiter is being planned—the Jupiter Icy Moons Orbiter 1,2 (JIMO) mission. Although the details are uncertain, the JIMO spacecraft will be massive (as much as 20,000 kg after escape from Earth) and will use nuclear electric propulsion 3 (having a total engine power of about 100 kW) with a high specific impulse (about 6,000 s). The launch is expected in 2011. 1 Upon arrival at Jupiter, the spacecraft will spiral into orbit around Callisto, then Ganymede, and finally Europa—the Icy Moons of Jupiter. If such a potent propulsive system is built, then a natural question to ask is what other missions might be flown. In this paper we will focus not on the Jupiter Icy Moons Orbiter Mission, but instead on innovative missions to the outer planets that are made possible by this new propulsion technology. Our principal goal is to consider how a massive nuclear electric propulsion (NEP) engine, used in conjunction with gravity assists from the inner planets, can deliver a spacecraft to the outer planets (Jupiter, Saturn, Uranus, * Graduate Student, email: [email protected] Doctoral Candidate, email: [email protected] Graduate Student, email: [email protected] § Professor, email: [email protected] A
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2 Neptune and Pluto). The technique of reaching the outer planets via gravity assists (but without electric propulsion) has been discussed for many decades beginning in the 1960’s with the pioneering work of Minovitch, 4,5 Flandro, 6 Deerwester, 7 and Niehoff.
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This note was uploaded on 01/15/2012 for the course AAE 490 taught by Professor Andrisani during the Fall '09 term at Purdue.

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IAC-04-A.6.02 - IAC-04-A.6.02 Design of Low-Thrust...

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