Masters Theses

Date of Award

8-2000

Degree Type

Thesis

Degree Name

Master of Science

Major

Aerospace Engineering

Major Professor

Remi Engels

Committee Members

Roy J. Schultz, U. Peter Solies

Abstract

Optimal ascent and booster glide back trajectories were determined for NASA Langley's proposed small satellite launcher, SSL-1, for a given polar mission, vehicle configuration, propulsion system, aerodynamic characteristics, structural characteristics and trajectory constraints. The optimal ascent and glide back trajectories were determined for a launch from Vandenberg Air Force Base launch pad SLC-2W and booster glide back to Vandenberg Air Force Base runway 30. The SSL-1 ascent and glide back trajectories were simulated and optimized in POST, Program to Optimize Simulated Trajectories. Inertial pitch angles relative to a inertial launch frame were specified as independent variables in the ascent trajectory and optimized to yield maximum weight to orbit. Aerodynamic angles were specified as independent variables in the booster glide back trajectory and optimized to yield maximum altitude at a heading alignment cylinder six nautical miles south of runway 30. The SSL-1 could not perform an ascent trajectory that satisfies the constraint of gliding the booster back to a heading alignment cylinder for runway 30. The optimal SSL-1 ascent trajectory results in 1022 lb of total weight and 384 lb of payload being inserted into a 150 nautical mile polar orbit. However, a booster glide back that achieves a desired altitude goal of 18800 ft at a heading alignment cylinder for runway 30 could not be performed from the separation point of the optimal ascent for the given aerodynamic and structural limits. The separation Mach number could not be reduced to a point where the booster could attain a desired glide back altitude using reductions in booster size alone since the booster size could not be reduced more than 3% and meet the dynamic pressure at separation constraint of 300 Ib/ft2. The glide back altitude goal can be obtained if the structural normal force limit is increased to 3g loads or the aerodynamic constraint on dynamic pressure at separation is increased to 400 Ib/ft2. The altitude goal will likely be obtained if a high angle of attack drag maneuver is performed between Mach numbers 3.2 and 1.2. The maximum allowable angle of attack for stable flight in this speed range and the corresponding lift/drag characteristics are needed to quantify the obtainable altitude. To achieve the desired altitude goal, modifications in the aerodynamic and/or structural limitations are needed. Weight to orbit performance is influenced by the dynamic pressure at separation constraint but is not sensitive to it. The weight to orbit ranges from 384 lb to 400 lb for dynamic pressure limits of 300 Ib/ft2 to 500 Ib/f2. The glide back altitude is sensitive to the dynamic pressure at separation constraint. Glide back altitude at the HAC ranges from 11995 ft to 24600 ft for dynamic pressure limits of 300 Ib/ft2 to 500 Ib/ft2. Both ascent and glide back performance is insensitive to atmospheric winds. Mean winds reduce payload by 2 lb and increase altitude at the heading alignment cylinder 515 ft. The SSL-1 weight to orbit performance is insensitive to movements in the vehicle's C.G. Movements up to 7% of the reference length result in a 2 lb change in payload. The glide back is sensitive to structural normal force limits Increasing the limit from 2.5g to 5.0g increases altitude at the heading alignment cylinder from 11995 ft to 23410 ft.

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