Orbital Flight Test Research Articles

Options for coordinated multi-point sensing in the lower thermosphere

A satellite mission for synchronized multi point measurements over tens of km in the lower thermosphere is possible at low cost and in a short time frame. This paper offers three options for providing coordinated multi-point sensing in the lower thermosphere. The options have quite different implications and idiosyncrasies, and possibly quite different costs and values. We invite members of the thermospheric research community to provide feedback on these concepts and how they might be used to best advantage.The authors have experience with proposing and pursuing small satellite missions, especially using space tether technology. Tether Applications has developed and delivered SEDS hardware for 3 successful orbital flight tests of tethers. Delta-Utec is specialized in deployment algorithms and has proposed and developed the tethered YES satellite.

A Test to Verify the Biocompatibility of a Method for Plant Culture in a Microgravity Environment

We report a pioneering attempt to use the NASA Shuttle Orbiter Middeck locker facility to acquire data on plant growth in near weightlessness. The information was needed to confirm the suitability of a plant culture system to be used in an experiment scheduled for the first Spacelab mission. The test was designed to measure germination and early seedling growth in a series of soil mixtures covering a range of water contents. Empirical determination of growth dependence on moisture content was required because both in theory and from Soviet flight experience it seemed possible that the dependence function in near weightlessness could be critically different from what we had measured on Earth. Such a difference could invalidate the future test in Spacelab 1 of gravity dependence of the differential growth process, circumnutation. After two failed attempts sufficient measurements were obtained from the third Shuttle Orbiter flight test to confirm the biocompatibility of the plant culture system--viz. soil moisture content variations had the same effect in near weightlessness as at 1 g. A number of supplemental observations about middeck locker conditions in Shuttle flight are presented. These may prove helpful to would-be experimenters who will plan to take advantage of future Shuttle flight opportunities for biological research.

Space Shuttle contamination measurements from flights STS-1 through STS-4

Successful completion of many scientific/technical measurements and safe Orbiter/payload operations during Space Shuttle flights requires limitations on the Orbiter-induced molecular and particulate environment. Four orbital flight tests have provided the opportunity to verify the results of efforts to keep the Orbiter contamination levels within defined goals. Contamination measurements were performed using various instruments on the induced environment contamination monitor. Results of these measurements indicate that, with the exception of special circumstances related to the Space Shuttle development, molecular contamination density and deposition as well as particulate contamination generally are within the requirements and are close to predicted levels.

Space Shuttle entry longitudinal aerodynamic comparisons of flight 2with preflight predictions

The Space Shuttle orbiter flight test program has required the aerodynamicist to take a new approach in determining flight characteristics. A conventional flight test program of slowly and cautiously approaching more severe flight conditions was not possible with the orbiter. On the first four orbital flights, The orbiter entered the atmosphere at approximately Mach 29 and decelerated through the Mach range (the subsonic portion of flight had also been flown by another orbiter vehicle during the Approach and Landing Test Program). Certification for these flights was achieved by an extensive wind tunnel test and analysis program. The initial series of flights of the orbiter were heavily instrumented for the purpose of obtaining accurate aerodynamic data. The flight data derived from the entry Mach range provided comparisons between flight and wind tunnel derived predicted data in the areas of both aerodynamic performance and longitudinal trim.

The Ocean Color Experiment (OCE) on the Second Orbital Flight Test of the Space Shuttle (OSTA-I)

The Ocean Color Experiment was one of the six remote-sensing experiments which for the first time were launched and success fully operated on board of the second flight of the Space Shuttle during November 1981. The experiment consists of a multispectral image scanner dedicated to the measurement of water color and its interpretation in terms of major water constituents and circulation patterns. The objectives of the experiment, the test site selection, and associated activities are described. The actual mission and results of an initial data analysis is discussed.

Space Shuttle primary onboard software - STS-1 to operational use

The Shuttle primary onboard software and associated computer hardware comprise a data processing complex responsible for virtually all inters}stem data flow and vehicle external interfaces. Onboard functions related to guidance, navigation, flight control, systems monitoring, and management, as well as vehicle/crew/ ground interfaces, are handled by this primary system. The organization that prepared the software for the Shuttle orbital flight tests emphasized a disciplined design and development phase coupled with a thorough independent verification activity. Current focus is centered on tailoring the software organization, test philosophy, and maintenance and test facilities to the high flight frequencies and diverse missions expected during the Shuttle operational era. Shuttle Software Overview T HE successful completion of the first orbital flight of the Shuttle (STS-1) in April of 1981 marked the culmination of one of the most complex software development and integration activities ever undertaken. The evolution of the Shuttle's data processing system (DPS) has spanned more than eight years. Along with the orbital flight tests, the development program also included the approach and landing test (ALT) project during which a Shuttle vehicle was launched from a Boeing 747 aircraft and performed the terminal approach and landing portions of the Shuttle mission. Five such ALT flights were performed during August through October of 1977 providing an early test bed for both the DPS hardware and basic software architecture that would eventually be used for the orbital test missions. With respect to size and complexity, the software for the first orbital flight test of the Shuttle involved eight separately executable programs or memory configurations sharing a common operating system (see Fig. 1). These programs were stored on a mass memory tape device and were loaded into the onboard computers on crew request. One of the eight performed all functions necessary to the launch, ascent, and orbit insertion phases of the mission. Two others provided software to be used during on-orbit operations and included both navigation and control functions as well as system monitoring and management functions. Another memory configuration performed all functions necessary to the de-orbit, entry, and landing mission phases. The remaining four were designed to perform critical prelaunch and on-orbit vehicle checkout procedures. In all, these eight programs, including the software operating system, comprised approximately one-half million 32-bit words of data and executable instructions. All Shuttle applications software modules and a large part of the operating system included in these memory configurations were implemented in the HAL/S high-order language. The language and associated compiler, specifically developed for aerospace applications, are scientifically oriented and especially suited to real-time systems. The criticality of the software to the Shuttle is emphasized by its numerous interfaces with other vehicle subsystems. There are few functions integral to the Shuttle operation for

Shuttle Orbiter acoustic fatigue certification testing

The Space Shuttle Orbiter is designed to a unique combination of loads and environments not previously encountered in aerospace practice because the reusable Shuttle is launched like an expendable space vehicle and the Orbiter lands horizontally like a conventional aircraft for the specified 100 mission-life of the Orbiter. The Orbiter is subjected to structural vibration caused by engine exhaust-generated acoustic noise during liftoff and aerodynamic noise during atmospheric flight. A requirement was established to certify the Orbiter structure, Thermal Protection Subsystem (TPS), mechanisms, equipment, etc. and to gather empirical data to support fatigue analyses and update vibration and internal noise criteria before the completion of the Orbiter flight test program (OFT). The requirement has largely been satisfied by completing a comprehensive acoustic fatigue development and certification test program. This paper addresses the certification portion of the program including test article selection, objectives, results, and conclusions. Also included are comparisons of ground and flight test data.

The Shuttle Orbiter DI-19 multienvironmental test program

DI-19 testing is presently in progress at NASA/LaRC to certify a critical section of the Orbiter lower forward fuselage structure/Thermal Protection Subsystem (TPS) to a combination/sequence of multienvironments simulating shuttle flight conditions. These environments and/or loads, and the flight events which are simulated, include: (a) rain as found on the pad, (b) combined acoustic noise and inplane static loading, (c) combined acoustic noise and inplane and differential pressure (ΔP) static loading in simulation of the ascent transonic/qmax period, (d) combined ascent heating and vacuum, (e) combined orbit cold soak and vacuum, (f) entry heating/vacuum profile, (g) combined acoustic noise and inplane and ΔP static loads in simulation of the post-entry qmax period, and (h) landing inplane static loading. The unique test facilities and procedures are described, as well as some of the results obtained during the first 16 mission exposure used to certify the structure/TPS for the four-mission Orbiter Flight Test Program. The relationship of DI-19 to the Orbiter Acoustic Fatigue Certification Test Program, which is performed at ambient atmospheric conditions and no static loads, is also described.

Orbital flight test program extended

NASA has extended the date for completion of the first four space shuttle orbital flight tests to April 1982. The extension of the flight test program has made it necessary to reschedule the first operational flight of the Columbia (STS‐5) from March 1 982 to September 1 982.The decision to extend the flight test program and reschedule STS‐5 is the result of several factors, the major one being the continuing engineering assessment and improvement of the thermal protection system.

Verification of the Space Shuttle Ascent Flight Control

The Space Shuttle vehicle consists of a reusable Orbiter vehicle, reusable SRB's (solid rocket boosters) that burn in parallel with the Orbiter main engines, and an expendable main propellant tank (external tank).During the critical flight phases such as ascent, primary flight control is provided by four onboard digital computers operating as a redundant set with each computer processing the same sensor data set, solving the same set of flight control algorithms, and independently driving via a digital data bus a secondary servo valve on each hydraulic actuator employed in gimballing the propulsion engines.This paper describes the unique avionics design features associated with Space Shuttle ascent flight control, and the test article, test equipment, and test techniques used to verify the ascent flight control prior to commitment to the first orbital flight test.

Space Shuttle Program Description and Status

The Space Shuttle Program objective is to establish a national space transportation capability that will substantially reduce the cost of space operations and support a wide range of scientific, defense, and commerical uses. The Space Shuttle Program has successfully completed its first phase-the Approach and Landing Test (ALT) Program. Testing is currently underway on all major components of the Space Shuttle. The first Space Shuttle orbital flight is scheduled for next year. This flight will be the first of six Orbital Flight Test (OFT) missions. Following the OFT phase, which will last approximately one year, the Space Shuttle will enter operational service.