Page:Project Longshot - Advanced Design Program Project Report.pdf/22



2.3 Orbits
Once the probe is assembled in orbit at the space station, it will be nudged into an independent but similar orbit to prevent damage to the station due to the exhaust from the first upper-stage burn (see Fig. 2.3a). This burn will be made to increase the inclination of the probe orbit from 28.5 degrees to 37.5 degrees so that it will sum with the obliquity and result in an orbit inclined 61 degrees relative to the ecliptic. This stage will be jettisoned, and the spacecraft will then escape Earth with a second burn which occurs at the ascending node of the probe's orbit about the earth (see Fig. 2.3b). This point then becomes the ascending node of the probe's heliocentric orbit, which is a circular orbit at 1 AU and at an inclination of 61 degrees. The second stage will then separate, and three months (i.e. one-fourth of an orbit) later, the third and final upper-stage will burn. This will send the spacecraft on an escape trajectory toward the Centauri system (see Fig. 2.3c), which is located at a declination of −61 degrees to the ecliptic. Upon completion of the interstellar phase of the mission the probe will be inserted into an eccentric orbit about Beta (see Figs. 2.3d and 2.3e).

Assuming a space station orbit of 300 kilometers at an inclination of 28.5 degrees, the following values were determined for required velocity changes for the probe. The Alpha Centauri star system is at a