4 research outputs found
A METHODOLOGY FOR CONDUCTING DESIGN TRADES FOR A SMALL SATELLITE LAUNCH VEHICLE WITH HYBRID ROCKET PROPULSION
The commercial space industry has recently seen a paradigm shift related to the launch
of a small satellite into Low Earth Orbit. In the past, a small satellite was launched as
a secondary payload with a medium or heavy launch vehicle where the primary payload
placed a constraint on the orbit and schedule. Today, a dedicated launch of a small launch
vehicle is the main operational concept to launch a small payload. Many Smallsat Launch
Vehicles (SLV) have been under development by the commercial space industry to improve
these launch services in recent years. Despite these efforts, the specific prices per launch
are still high, and reducing these prices further remains a challenge.
One promising technology candidate to reduce costs for SLV is hybrid rocket propulsion
which has matured recently with some cost and safety advantages. Although hybrid
rocket propulsion faces a number of challenges, including a low regression rate and
combustion instabilities, academia and commercial companies have invested significant resources in developing this technology. With this motivation, this thesis has focused on the
conceptual design of SLV with hybrid rocket propulsion. Moreover, a cost reduction strategy
currently used by the commercial space industry was observed to be the development
of a unique engine and using multiple of them in a launch vehicle. Following this trend,
the vehicle concept investigated in this thesis was an expendable ground-launched vehicle
with some architectural variables such as the number of stages and the number of hybrid
motors in each stage.
The design trade-off studies of such a small multistage launch vehicle with multiple hybrid
motors in each stage require very long times especially when traditional point design
approaches are used. As the number of design variables increase, the design space exploration
becomes even more challenging. To provide a solution to this problem, a methodology
for rapid conceptual design of such a vehicle was presented in this thesis.
A physics-based conceptual design approach was followed in this study since SLV are relatively new concepts without much historical performance data. To conduct a multidisciplinary
analysis, a physics-based, integrated modeling and simulation environment
was constructed with four core disciplines: trajectory analysis, aerodynamics, propulsion,
and weight. Aerodynamics and propulsion analysis were conducted using a first-principles
approach, which was based on fundamental theories. A 3 Degree of Freedom (DOF) industrial,
transparent, physics-based trajectory analysis software was used in this study based
on availability. However, any other trajectory analysis software that a system designer is
familiar with can be used in its place. In other words, the methodology developed in this
thesis would remain unchanged if another trajectory analysis software were used. The
weight discipline was represented at a high level by using Propellant Mass Fraction (PMF)
design variable.
A multidisciplinary modeling and simulation environment for launch vehicles may be
computationally expensive depending on the fidelity levels of each discipline. Moreover,
trajectory optimization is included in a launch vehicle design process conventionally which
may be also computationally expensive depending on the optimization method. This expense
poses a difficulty in performing a trade-off study for hundreds of vehicle design alternatives
within the constraints of the schedule in the conceptual design phase. Because of
this, trajectory optimization was removed from the design process to speed up the process
by selecting a constant controller design.
The methodology developed in this thesis consisted of two sequential steps. In the first
step, a surrogate modeling approach was followed to replace the Modeling and Simulation
(M&S) environment. A DOE method and a surrogate modeling method suitable to this
problem were searched in this part. To cover the design space, a hybrid DOE consisting
of a Fast Flexible Filling DOE and a three-level Full Factorial DOE was chosen. Artificial
Neural Networks method was selected to fit approximation models because of the type of
design variables (both continuous and discrete variables) and nonlinearity of the problem.
The first experiment was conducted to test this hypothesis. As a result, it was demonstrated that this approach can provide accurate surrogate models for any desired response.
In the second step, the specific mechanical energy-based design trade-off method was
developed using some statistical methods. This method estimates the lower bound of the
vehicles’ actual specific mechanical energy where the vehicles can be rapidly designed by
using surrogate models. This lower bound was predicted with the help of the prediction
interval of the specific mechanical energy’s model fit error. To fit the surrogate models,
the necessary data were gathered by running the DOE in the integrated M&S environment
while imposing some terminal conditions on the altitude of the vehicles analyzed in this
environment. Specifically, the surrogate models of specific mechanical energy and flight
path angle were used to design the vehicles rapidly. The second experiment was conducted
to test this hypothesis. As a result, the actual specific mechanical energies computed via
trajectory optimization were found to be consistent with the predictions. Overall, it was
demonstrated that the proposed method enables a system designer to rapidly design some
feasible vehicles, which can then proceed to the next design phase for further comparison,
analysis, and design.M.S
NASA Tech Briefs, November/December 1987
Topics include: NASA TU Services; New Product Ideas; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Fabrication Technology; Machinery; Mathematics and Information Sciences; Life Sciences
Mathematical surfaces models between art and reality
In this paper, I want to document the history of the mathematical surfaces models used for the didactics of pure and applied “High Mathematics” and as art pieces. These models were built between the second half of nineteenth century and the 1930s. I want here also to underline several important links that put in correspondence conception and construction of models with scholars, cultural institutes, specific views of research and didactical studies in mathematical sciences and with the world of the figurative arts furthermore. At the same time the singular beauty of form and colour which the models possessed, aroused the admiration of those entirely ignorant of their mathematical attraction
Recommended from our members
1995 BRAC Commission
ARD Detachment, Naval Surface Warfare Center Carderock Division, Naval Surface Warfare Center Carderock Division Detachment Annapolis, Naval Surface Warfare Center Carderock Philadelphia Detachment. Data Call 64. Box 181, L-113