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  • 1
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    Aerobraking for capture into Martian orbit (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A summary is given of several studies into problems associated with aerobraking a manned vehicle into a Martian capture orbit. The problems investigated are the establishment of entry flight path angle windows that allow aerocapture; the determination of the sensitivity of the entry trajectory to initial flight path angle; the determination of the effect on aerocapture of the assumed Martian atmosphere model; and the determination of the effect of random atmosphere disturbances on adaptive guidance systems that may be used for aerocapture. As a result of investigating the above problem areas, entry windows were established for three different vehicle configurations. Sensitivities to changes in initial flight path angle were also obtained for these three configurations. One configuration was chosen to determine the effect of Martian atmospheric model changes and random variations of density within a specific atmospheric model. Of particular interest was the effect of random density variations on adaptive guidance techniques. The effect of entry velocity on the size of the entry window was also examined.
    Keywords: ASTRODYNAMICS
    Type: NASA, Goddard Space Flight Center, Flight Mechanics(Estimation Theory Symposium, 1990; p 491-510
    Format: application/pdf
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  • 2
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    Technology development program for twenty-first century aerospace vehicles (1987)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: A program to meet the avionics technology needs for the design of future space transportation systems is presented. The program is designed to meet as many technology goals as possible by 1996 so decisions can be made as to which vehicles are feasible and which should be constructed.
    Keywords: AIRCRAFT INSTRUMENTATION
    Type: AGARD, The Design, Development and Testing of Complex Avionics Systems; 6 p
    Format: text
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  • 3
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    Summary of longitudinal stability and control parameters as determined from Space Shuttle Challenger flight test data (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Estimates of longitudinal stability and control parameters for the space shuttle were determined by applying a maximum likelihood parameter estimation technique to Challenger flight test data. The parameters for pitching moment coefficient, C(m sub alpha), (at different angles of attack), pitching moment coefficient, C(m sub delta e), (at different elevator deflections) and the normal force coefficient, C(z sub alpha), (at different angles of attack) describe 90 percent of the response to longitudinal inputs during Space Shuttle Challenger flights with C(m sub delta e) being the dominant parameter. The values of C(z sub alpha) were found to be input dependent for these tests. However, when C(z sub alpha) was set at preflight predictions, the values determined for C(m sub delta e) changed less than 10 percent from the values obtained when C(z sub alpha) was estimated as well. The preflight predictions for C(z sub alpha) and C(m sub alpha) are acceptable values, while the values of C(z sub delta e) should be about 30 percent less negative than the preflight predictions near Mach 1, and 10 percent less negative, otherwise.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA-TM-101605 , NAS 1.15:101605
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  • 4
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    Aeroassist flight experiment guidance Quiet Time (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The science experiments for the Aeroassist Flight Experiment (AFE) will be greatly enhanced by taking measurements with no Reaction Control System (RCS) contamination just before perigee. Methods of modifying the AFE guidance to accomplish this are discussed. Several methods that could give up to 30 seconds of quiet time were investigated and the results of these guidance modifications shown. A 20 second quiet time is definitely possible and a 30 second quiet time may be possible if the guidance can be inactive past perigee. Some of the most significant being the criterion for determining if the mission is threatened. A limited follow-on test program is outlined.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-100556 , NAS 1.26:100556
    Format: application/pdf
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  • 5
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    Lateral and longitudinal stability and control parameters for the space shuttle discovery as determined from flight test data (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The Discovery vehicle was found to have longitudinal and lateral aerodynamic characteristics similar to those of the Columbia and Challenger vehicles. The values of the lateral and longitudinal parameters are compared with the preflight data book. The lateral parameters showed the same trends as the data book. With the exception of C sub l sub Beta for Mach numbers greater than 15, C sub n sub delta r for Mach numbers greater than 2 and for Mach numbers less than 1.5, where the variation boundaries were not well defined, ninety percent of the extracted values of the lateral parameters fell within the predicted variations. The longitudinal parameters showed more scatter, but scattered about the preflight predictions. With the exception of the Mach 1.5 to .5 region of the flight envelope, the preflight predictions seem a reasonable representation of the Shuttle aerodynamics. The models determined accounted for ninety percent of the actual flight time histories.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA-TM-100555 , NAS 1.15:100555
    Format: application/pdf
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  • 6
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    Aeroassisted orbit transfer vehicle trajectory analysis (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The emphasis in this study was on the use of multiple pass trajectories for aerobraking. However, for comparison, single pass trajectories, trajectories using ballutes, and trajectories corrupted by atmospheric anomolies were run. A two-pass trajectory was chosen to determine the relation between sensitivity to errors and payload to orbit. Trajectories that used only aerodynamic forces for maneuvering could put more weight into the target orbits but were very sensitive to variations from the planned trajectors. Using some thrust control resulted in less payload to orbit, but greatly reduced the sensitivity to variations from nominal trajectories. When compared to the non-thrusting trajectories investigated, the judicious use of thrusting resulted in multiple pass trajectories that gave 97 percent of the payload to orbit with almost none of the sensitivity to variations from the nominal.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-89138 , NAS 1.15:89138
    Format: application/pdf
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  • 7
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    An analysis of the effect of aeroassist maneuvers on orbital transfer vehicle performance (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This paper summarizes a Langley Research Summer Scholars (LARSS) research project (Summer 1986) dealing with the topic of the effectiveness of aeroassist maneuvers to accomplish a change in the orbital inclination of an Orbital Transfer Vehicle (OTV). This task was subject to OTV design constraints, chief of which were the axial acceleration and the aerodynamic heating rate limits of the OTV. The use of vehicle thrust to replace lost kinetic energy and, thereby, to increase the maximum possible change in orbital inclination was investigated. A relation between time in the hover orbit and payload to LEO was established. The amount of plane change possible during this type of maneuver was checked for several runs and a possible thrusting procedure to increase the plane change and still get to LEO was suggested. Finally, the sensitivity of various target parameters to controllable independent variables was established, trades between the amount of control allowed, and payload to LEO suggested.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-89117 , NAS 1.15:89117
    Format: application/pdf
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  • 8
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    Effect of Transition Aerodynamics on Aeroassist Flight Experiment Trajectories (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Various transition methods are used here to study the viscous effects encountered in low density, hypersonic flight, through the transition from free molecular to continuum flow. Methods utilizing Viking data, Shuttle Orbiter data, a Potter number parameter, and a Shock Reynolds number were implemented in the Program to Optimize Simulated Trajectories (POST). Simulations of the Aeroassist Flight Experiment (AFE) using open loop guidance were used to assess the aerodynamic performance of the vehicle. A bank angle was found for each transition method that would result in a 200 nautical-mile apogee. Once this was done, the open loop guidance was replaced by the proposed guidance algorithm for the AFE. Simulations were again conducted using that guidance and the different transitions for comparison. For the gains used, the guidance system showed some sensitivity in apogee altitude to the transition method assumed, but the guidance was able to successfully complete the mission.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-100546 , NAS 1.15:100546
    Format: application/pdf
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  • 9
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    Preliminary investigation of parameter sensitivities for atmospheric entry and aerobraking at Mars (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The proposed manned Mars mission will need to be as weight efficient as possible. A way of lowering the weight of the vehicle by using aeroassist braking instead of retro-rockets to slow a craft once it reaches its destination is discussed. The two vehicles studied are a small vehicle similar in size to the Mars Rover Sample Return (MRSR) vehicle and a larger vehicle similar in size to a six-person Manned Mars Mission (MMM) vehicle. Simulated entries were made using various coefficients of lift (C sub L), coefficients of drag (C sub D), and lift-to-drag ratios (L/D). A range of acceptable flight path angles with their corresponding bank angle profiles was found for each case studied. These ranges were then compared, and the results are reported here. The sensitivity of velocity and acceleration to changes in flight path angle and bank angle is also included to indicate potential problem areas for guidance and navigation system design.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-101607 , NAS 1.15:101607
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  • 10
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    Aerobraking characteristics for several potential manned Mars entry vehicles (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: While a reduction in weight is always desirable for any space vehicle, it is crucial for vehicles to be used in the proposed Manned Mars Mission (MMM). One such way to reduce a spacecraft's weight is through aeroassist braking which is an alternative to retro-rockets, the traditional method of slowing a craft approaching from a high energy orbit. In this paper aeroassist braking was examined for two blunt vehicle configurations and one streamlined configuration. For each vehicle type, a range of lift-to-drag ratios was examined and the entry angle windows, bank profiles, and trajectory parameters were recorded here. In addition, the sensitivities of velocity and acceleration with respect to the entry angle and bank angles were included. Also, the effect of using different atmosphere models was tested by incorporating several models into the simulation program.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-101669 , NAS 1.15:101669
    Format: application/pdf
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