Engineering topics

Lindberg, Robert E.

Publications and source records attributed to Lindberg, Robert E..

5 records

NASA NTRS2008

Deflection Analysis of the Space Shuttle External Tank Door Drive Mechanism

Upon observing an abnormal closure of the Space Shuttle s External Tank Doors (ETD), a dynamic model was created in MSC/ADAMS to conduct deflection analyses for assessing whether the Door Drive Mechanism (DDM) was subjected to excessive additional stress, and more importantly, to evaluate the magnitude of the induced step or gap with respect to shuttle s body tiles. To model the flexibility of the DDM, a lumped parameter approximation was used to capture the compliance of individual parts within the drive linkage. These stiffness approximations were then validated using FEA and iteratively updated in the model to converge on the actual distributed parameter equivalent stiffnesses. The goal of the analyses is to determine the deflections in the mechanism and whether or not the deflections are in the region of elastic or plastic deformation. Plastic deformation may affect proper closure of the ETD and would impact aero-heating during re-entry.

Tosto, Michael A.↗

NASA NTRS2008

Deflection Analysis of the Space Shuttle External Tank Door Drive Mechanism

Upon observing an abnormal closure of the Space Shuttle s External Tank Doors (ETD), a dynamic model was created in MSC/ADAMS to conduct deflection analyses of the Door Drive Mechanism (DDM). For a similar analysis, the traditional approach would be to construct a full finite element model of the mechanism. The purpose of this paper is to describe an alternative approach that models the flexibility of the DDM using a lumped parameter approximation to capture the compliance of individual parts within the drive linkage. This approach allows for rapid construction of a dynamic model in a time-critical setting, while still retaining the appropriate equivalent stiffness of each linkage component. As a validation of these equivalent stiffnesses, finite element analysis (FEA) was used to iteratively update the model towards convergence. Following this analysis, deflections recovered from the dynamic model can be used to calculate stress and classify each component s deformation as either elastic or plastic. Based on the modeling assumptions used in this analysis and the maximum input forcing condition, two components in the DDM show a factor of safety less than or equal to 0.5. However, to accurately evaluate the induced stresses, additional mechanism rigging information would be necessary to characterize the input forcing conditions. This information would also allow for the classification of stresses as either elastic or plastic.

Tosto, Michael A.↗

NASA NTRS2008

Sense and Sensibility: The Case for the Nationwide Inclusion of Engineering in the K-12 Curriculum

The competitive status of the United States is inextricably linked to innovation just as innovation is inseparable from science, technology, engineering, and mathematics. To stay competitive in innovation requires that the United States produce a 21st century workforce complete with requisite education, training, skills, and motivation. If we accept a priori that science, technology, engineering, and mathematics education are crucial to competitiveness and innovation and that, in terms of innovation, mathematics, science, and engineering are interdependent, why are mathematics and science uniformly ubiquitous in the K-12 curriculum while engineering is conspicuously absent? We are passionate in our belief that the uniform addition of engineering to the K-12 curriculum will help ensure that the nation has "the right" 21st Century workforce. Furthermore, we believe that a nationwide effort, led by a coalition of engineering academics, practitioners, and societies is required to turn this goal into reality. However, accomplishing this goal necessitates, as we are reminded by the title of Jane Austen's timeless novel, "Sense and Sensibility", a workable solution that seeks the "middle ground" between passion and reason. We begin our paper by making two essential points: Engineers are not scientists. Engineering exists separate from science, has its own specialized knowledge community apart from science, and it is largely responsible for many of the most significant advancements and improvements in the quality of our life. Our workable solution requires that K-12 education, nationwide, accommodate the inclusion of engineering as a stand alone curriculum and we offer three reasons to support our position: (1) workforce development, (2) stimulating interest in STEM (science, technology, engineering, and mathematics) courses and careers, and (3) creating a technologically literate society. We conclude with some thoughts on how this important goal can be accomplished.

Lindberg, Robert E.↗

NASA NTRS2006

Titan Explorer Entry, Descent and Landing Trajectory Design

The Titan Explorer mission concept includes an orbiter, entry probe and inflatable airship designed to take remote and in-situ measurements of Titan's atmosphere. A modified entry, descent and landing trajectory at Titan that incorporates mid-air airship inflation (under a parachute) and separation is developed and examined for Titan Explorer. The feasibility of mid-air inflation and deployment of an airship under a parachute is determined by implementing and validating an airship buoyancy and inflation model in the trajectory simulation program, Program to Optimize Simulated Trajectories II (POST2). A nominal POST2 trajectory simulation case study is generated which examines different descent scenarios by varying airship inflation duration, orientation, and separation. The buoyancy model incorporation into POST2 is new to the software and may be used in future trajectory simulations. Each case from the nominal POST2 trajectory case study simulates a successful separation between the parachute and airship systems with sufficient velocity change as to alter their paths to avoid collision throughout their descent. The airship and heatshield also separate acceptably with a minimum distance of separation from the parachute system of 1.5 km. This analysis shows the feasibility of airship inflation on a parachute for different orientations, airship separation at various inflation times, and preparation for level-flight at Titan.

Fisher, Jody L.↗

NASA NTRS1986

N-ROSS: The dynamics and control issues

The Navy Remote Ocean Sensing System (N-ROSS) Dynamic Stability Study team concluded that the frozen April 1985 design was viable and contained no show stoppers, although it was also clear from the study results that the configuration required further optimization. While the frozen N-ROSS configuration used has since been superceded, and the vehicle is now under competitive procurement, several other results remain from the study that will have lasting value to the N-ROSS program. The importance of constructing an integrated simulation, to serve as a design and verification aid, has been clearly established. The two team approach to the study afforded the Navy a higher degree of confidence in the results than could have been accomplished by a single simulation, and the approach led to results that highlighted subtleties in the model and simulation development that surely would have been overlookded without the benefit of an independent companion simulation with which to compare it.

Lindberg, Robert E.↗