1. AAE450 Spring 2009 Low Thrust Spiral Transfer Maneuvers and Analysis [Andrew Damon] [Mission Ops] February 5, 2009 1

2. AAE450 Spring 2009 [Andrew Damon] [Mission Ops] TLI and Lunar Capture Scenarios Delta V breakdown for EP system Spiral transfer from 200 km Earth parking orbit to edge of moon’s sphere of influence (~66,000 km from moon – L1) ΔV 1 = 6.70 km/s to L1 (Lagrange point 1) Spiral Transfer from L1 to 110 km lunar orbit ΔV 2 = 0.50 km/s = 500 m/s ΔV tot = 7.2 km/s Compare to: ΔV 2 for impulsive maneuver to put periapsis at 110 km lunar orbit, with apoapsis near L1 ΔV 2 = 1.10 km/s ΔV tot = 7.8 km/s 2

3. AAE450 Spring 2009 Higher Precision Spiral Model Based on:  Herman and Conway: “Optimal, Low-Thrust, Earth–Moon Orbit Transfer”  Constant thrust accelerations on the order of 10 -4 g –Time of flights on the order of 30 days  Our thrust half of this value, at most –Time of flights on the order of 2+ months  Equations of motion based on modifed Keplerian elements  Perturbing accelerations accounted for, from Earth, Moon, s/c thrust  Will give more accurate trajectory and time of flight data [Andrew Damon] [Mission Ops] 3