Engineering topics

Shepard, Kyle M.

Publications and source records attributed to Shepard, Kyle M..

3 records

NASA NTRS1990

High and low thrust mission analysis for a Mars exploration program

The purpose of the study is to identify limits, trends, and sensitivities of Mars Transportation System performance over several Mars mission opportunities. Two Mars Transfer Vehicle (MTV) configurations utilizing different propulsion systems (Chemical/Aerobrake and NEP - Nuclear Electric Propulsion) are outlined. The trades involved in comparing two MTS candidate designs are assessed. Mission analysis for mission opportunities beginning in around 2010 and continuing past 2030 is performed, and a Mars mission model is covered, along with orbit selection and NEP and Chemical/Aerobrake performance. The results of several sensitivity studies are given in order to allow for contingency planning in design and performance. It is concluded that the low-thrust system perform best, its vehicle mass is lower and its trip times are more stable.

Shepard, Kyle M.↗

NASA NTRS1990

An infrastructure assessment of alternative Mars Transfer Vehicles

Development and evolutionary paths for many space transportation elements must be considered as the United States space program embarks on the Space Exploration Initiative (SEI). A central element of the space transportation infrastructure necessary to support the SEI is Mars Transportation System (MTS). This system consists of the Mars Transfer Vehicle (MTV) and Mars Excursion Vehicle. This paper describes the process and results in evaluating the alternate MTV propulsion concepts. Primary discriminators in evaluating different options for the MTV alternatives are: requirements for earth-to-orbit delivery, on-orbit facility and assembly requirements, and mission performance. Propulsion candidates assessed in this paper include nuclear thermal propulsion, nuclear electric propulsion, solar electric propulsion, and cryogenic chemical propulsion (LO2/LH2). The primary discriminators as well as additional selection criteria will be discussed for each MTS alternative.

Holdridge, Jeffrey D.↗

NASA NTRS1990

A comparison of transportation node costs and their primary drivers

This paper describes the process for defining and evaluating the costs of alternative transportation node concepts for Space Station Freedom. A cost estimating methodology including costs of development, production, delivery, assembly, steady state operations, and mission-specific operations is described in detail. The primary drivers of transportation node costs are identified and discussed.

Comstock, Douglas A.↗