Shuttle Flight Research Articles

Controlling and predicting the quality of space shuttle software using metrics

Software quality metrics have potential for helping to assure the quality of software on large projects such as the Space Shuttle flight software. It is feasible to validate metrics for controlling and predicting software quality during design by validating metrics against a quality factor. Quality factors, like reliability, are of more interest to customers than metrics, like complexity. However quality factors cannot be collected until late in a project. Therefore the need arises to validate metrics, which developers can collect early in a project, against a quality factor. We investigate the feasibility of validating metrics for controlling and predicting quality on the Space Shuttle. The key to the approach is the use of validated metrics for early identification and resolution of quality problems.

Altered skeletal pattern of gene expression in response to spaceflight and hindlimb elevation.

Spaceflight leads to osteopenia, in part by inhibiting bone formation. Using an animal model (hindlimb elevation) that simulates the weightlessness of spaceflight, we and others showed a reversible inhibition of bone formation and bone mineralization. In this study, we have measured the mRNA levels of insulin-like growth factor I (IGF-I), IGF-I receptor (IGF-IR), alkaline phosphatase, and osteocalcin in the tibiae of rats flown aboard National Aeronautics and Space Administration Shuttle Flight STS-54 and compared the results with those obtained from their ground-based controls and from the bones of hindlimb-elevated animals. Spaceflight and hindlimb elevation transiently increase the mRNA levels for IGF-I, IGF-IR, and alkaline phosphatase but decrease the mRNA levels for osteocalcin. The changes in osteocalcin and alkaline phosphatase mRNA levels are consistent with a shift toward decreased maturation, whereas the rise in IGF-I and IGF-IR mRNA levels may indicate a compensatory response to the fall in bone formation. We conclude that skeletal unloading during spaceflight or hindlimb elevation resets the pattern of gene expression in the osteoblast, giving it a less mature profile.

Effects of Space Shuttle flight on the reflectance characteristics of diffusers in the near-infrared, visible, and ultraviolet regions

Many remote sensing instruments employ diffuse targets for calibration. These targets usually consist of diftusers with high Lambertian characteristics illuminated by a calibrated irradiance source. There is increasing interest in conducting in-orbit radiance calibration checks of remote sensing instruments using sunlight reflected off a diffuser. We report on the effects of space flight on the reflectance properties of polytetrafluoroethylene (PTFE) and aluminum diffuser samples flown on three Space Shuttle flights. These experiments showed good stability of both diffuser types in the visible and near infrared but experienced measurable degradation in the ultraviolet. Degradation varied from flight to flight and seemed to be related to different levels of contamination experienced on the three flights.

Measurements of trapped protons and cosmic rays from recent shuttle flights

We have flown two new charged particle detectors in five recent Shuttle flights. In this paper we report on the dose rate, equivalent dose rate, and radiation quality factor for trapped protons and cosmic radiation separately. A comparison of the integral linear energy transfer (LET) spectra with recent transport code calculations show significant disagreement. Using the calculated dose rate from the omni-directional AP8MAX model with IGRF reference magnetic field epoch 1970, and observed dose rate as a function of (averaged over all geographic latitude) and longitude, we have determined the westward drift of the South Atlantic anomaly. We have also studied the east-west effect, and observed a ‘second’ radiation belt. A comparison of the galactic cosmic radiation lineal energy transfer spectra with model calculations shows disagreement comparable to those of the trapped protons.

Formation and vesiculation of biomembranes during spaceflight

Shuttle flight, sounding rocket flight, and parabolic flight experiments demonstrate the formation of bilayer membrane vesicles (liposomes) in reduced gravity, following the dilution of detergent from detergent-phospholipid mixed micelles. The reduction in detergent concentration initiates assembly of bilayer membrane sheets, which are sensitive to solution distrubances. An increase in distrubances by forced dilution results in small diameter liposomes (< 150 nm), in both ground and flight samples. In the absence of forced dilution, liposomes remain small at 1-g, but exhibit much larger diameters at 0-g (1000–2000 nm). Our spaceflight data reveal that membrane assembly and vesiculation are strongly influenced by gravity-induced solution disturbances (e.g., convection currents), which limit vesicle diameter.

Validating metrics for ensuring Space Shuttle flight software quality

In this article, we cover the validation of software quality metrics for the Space Shuttle. Experiments with Space Shuttle flight software show that the Boolean OR discriminator function can successfully validate metrics for controlling and predicting quality. Further, we found that statement count and node count are the metrics most closely associated with the discrepancy reports count, and that with data smoothing their critical values can be used as predictors of software quality. We are continuing our research and comparing validated metrics with actual results in an attempt to determine whether the use of additional metrics provides sufficiently greater discriminative power to justify the increased inspection costs. >

NASA's space life sciences training program

The Space Life Sciences Training Program (SLSTP) is an intensive, six-week training program held every summer since 1985 at the Kennedy Space Center (KSC). A major goal of the SLSTP is to develop a cadre of qualified scientists and engineers to support future space life sciences and engineering challenges. Hand-picked, undergraduate college students participate in lectures, laboratory sessions, facility tours, and special projects: including work on actual Space Shuttle flight experiments and baseline data collection. At NASA Headquarters (HQ), the SLSTP is jointly sponsored by the Life Sciences Division and the Office of Equal Opportunity Programs: it has been very successful in attracting minority students and women to the fields of space science and engineering. In honor of the International Space Year (ISY), 17 international students participated in this summer's program. An SLSTP Symposium was held in Washington D.C., just prior to the World Space Congress. The Symposium attracted over 150 SLSTP graduates for a day of scientific discussions and briefings concerning educational and employment opportunities within NASA and the aerospace community. Future plans for the SLSTP include expansion to the Johnson Space Center in 1995.

Summary of Lower Body Negative Pressure Experiments During Space Flight

This paper summarizes the lower body negative pressure experiments performed in space, beginning with the experiments conducted on Skylab, because this program provided the most cardiovascular physiology data for United States space flight. Data obtained during studies of lower body negative pressure for use as a countermeasure after months of Russian space flight are also presented. Lower body negative pressure experiments conducted aboard Space Shuttle flights provide data about the deadaptation response of the cardiovascular system to orthostatic stress occurring during periods of zero gravity, and about protection against postflight orthostatic intolerance. Data obtained using Russian and American lower body negative pressure devices indicate that, when a crew member stands, as opposed to being supported by a seat or saddle as in the American device, there may be a slight detrimental effect in terms of the cardiovascular response to this orthostatic stress. Comparison of heart rate and blood pressure response to entry and landing of the Shuttle indicate that, although lower body negative pressure is a different stress and is applied in a different manner, the maximum heart rates during lower body negative pressure are reached at approximately the same point that the maximum heart rates are reached during entry and landing. Thus, the use of a lower body negative pressure stress in flight is a fairly good predictor of the cardiovascular response to the actual entry and landing of the Shuttle.

Strategies for the Preflight Circadian Shifting of Space Shuttle Crews

In June, 1990, a workshop was put together at NASA/Johnson Space Center to address difficulties the astronauts were having in adjusting their wake and sleep schedule, both immediately before and during Space Shuttle missions. The workshop members, prominent investigators in human circadian research, developed a number of strategies by which astronauts could tackle the problem of circadian adaptation within the demanding timetable of a Space Shuttle mission. The strategies included both abrupt and gradual methods, and some approaches used artificial "very bright lights" to reset the physiologic circadian pacemaker. The strategies have since been operationally implemented on Space Shuttle flights, with good success. This is a report of the problems addressed by the workshop and its recommendations.

Measurements of Trapped Protons and Cosmic Rays from Recent Shuttle Flights

Two new charged particle detectors have been flown in five recent Shuttle flights. The tissue-equivalent proportional counter measures the lineal energy spectrum of space radiation in the 0.26-300 keV micrometer-1 range. The charged particle spectrometer is a double dE/dx x E and dE/dx x Chrenekov detector system which provides a measurement of the differential energy spectrum of protons from 13 to 350 MeV and dose rate in silicon. In this paper the dose rate, equivalent dose rate, and radiation, quality factor for trapped protons and cosmic radiation are reported on separately. A comparison of the integral LET spectra with recent transport code calculations shows significant disagreement. Using the calculated dose rate from the omnidirectional AP8MAX model with IGRF reference magnetic field epoch 1970, and observed dose rate as a function of geographic latitude and longitude, the westward drift of the south Atlantic anomaly has been determined. The east-west effect has also been studied and a 'second' radiation belt observed. A comparison of the galactic cosmic radiation (GCR) lineal energy transfer spectra with model calculations shows disagreement comparable with those of the trapped protons.

Measurements of Trapped Protons and Cosmic Rays from Recent Shuttle Flights

Measurements of Trapped Protons and Cosmic Rays from Recent Shuttle Flights

Shuttle flight succeeds despite some glitches

Completing a mission hailed by its sponsors as a success despite some glitches, space shuttle Discovery landed Feb. 11 at Kennedy Space Center in Florida. During eight days in Earth orbit, the six-member crew carried out materials processing and biotechnology experiments under microgravity and high-vacuum conditions. One largely successful test could lead to production of highly pure, thin semiconductor films in space. The mission also initiated a new era of joint space efforts by the U.S. and Russia. On board was the first Russian cosmonaut to fly on a U.S. shuttle—Sergei K. Krikalev, 35. His flight will be followed by additional U.S.-Russia space missions, leading ultimately to U.S.-Russian cooperation in building an international space station (C&EN, Nov. 22,1993, page 29). The mission had two major objectives: to conduct the first test in space of the Wake Shield Facility to generate an ultravacuum for epitaxial growth of highly pure, thin semiconductor films (growing the films one ...

The influence of microgravity on the dendritic growth rates of NH 4Cl-H 2O: an international microgravity laboratory experiment

Ten NH 4 Cl- H 2 O Bridgman directional solidification experiments were run on an International Microgravity Laboratory Space Shuttle flight in January 1992 using a matrix of temperature gradients and cooling rates. Ground-based experiments using otherwise duplicate conditions were conducted on earth in the flight science modules. Dendritic front growth rates were obtained using reconstruction holograms taken periodically during the runs. The ground-based growth rates of the dendritic fronts were approximately one-half those of the flight growth rates. This is attributed primarily to changes in the concentration of the bulk fluid supplying NH 4Cl to the tips as a result of the onset of convective flow and the concomitant dendritic coarsening. Reduced transparency of the overall mushy zone on earth is attributed to the increased ammonium chloride concentration within the interdendritic fluid. These results indicate that microgravity is a valid experimental platform for minimizing flow effects and therefore ennabling the optimum production of directional materials.

HL-20 subsystem design

The NASA Langley Research Center has been developing a lifting-body configuration called the HL-20 for potential application as a personnel launch system orbiter that will provide the crew changeout at the Space Station Freedom. The objectives have been to provide an alternate manned access to space with a more cost-effective, efficient, reliable, and safer system for the routine transportation of people to LEO. The detailed study of this concept includes the subsystem design, flight software sizing, and mass properties that are discussed in this paper. The goals were to develop a subsystem complement to maximize operational efficiency with minimum development costs while using current technology. Subsystem selection and trade studies showed that current technology components will provide the required performance and operational effectiveness. Many of the selected components have Shuttle flight histories or considerable development heritage from other programs that will help minimize development costs.

Comparison of treatment strategies for Space Motion Sickness

Treatment strategies for Space Motion Sickness (SMS) were compared using the results of postflight oral debriefings. Standardized questionnaires were administered to all crewmembers immediately following Space Shuttle flights by NASA flight surgeons. Cases of SMS were graded as mild, moderate, or severe based on published criteria, and medication effectiveness was judged based on subjective reports of symptom relief. Since October 1989, medication effectiveness is reported inflight through Private Medical Conferences with the crew. A symptom matrix was analyzed for 19 crewmembers treated with oral combination of scopolamine and dextroamphetamine (scopdex) and 15 crewmembers treated with promethazine delivered by intramuscular i.m. or suppository routes. Scopdex has been given preflight as prophylaxis for SMS, but analysis showed delayed symptom presentation in 9 crewmembers or failed to prevent symptoms in 7. Only 3 crewmembers who took scopdex had no symptoms inflight. Fourteen out of 15 crewmembers treated with i.m. promethazine and 6 of 8 treated with promethazine suppositories after symptom development had immediate (within 1–2h) symptom relief and required no additional medication. There were no cases of delayed symptom presentation in the crewmembers treated with promethazine. This response is in contrast to untreated crewmembers who typically have slow symptom resolution over 72–96h. We conclude that promethazine is an effective treatment of SMS symptoms inflight. NASA policy currently recommends treating crewmembers with SMS after symptom development, and no longer recommends prophylaxis with scopdex due to delayed symptom development and apparent variable absorption of oral medications during early flight days.

Calibration and Radiometric Stability of the Shuttle Solar Backscatter Ultraviolet (SSBUV) Experiment

The SSBUV is part of the National Plan for monitoring the stratosphere. Ozone monitoring from space employs backscatter ultraviolet-type instruments on NOAA operational, NASA research and foreign environmental satellites. The SSBUV provides calibration data for these instruments using nearly coincident observations of the Earth's ultraviolet albedo from a series of Space Shuttle flights. The SSBUV also measures the middle ultraviolet solar irradiance as part of the ozone measurement. A major requirement for the SSBUV is that its calibration be known to about 1% from one flight to the next. To achieve this, the SSBUV conducts a rigorous calibration program involving multiple standard sources and detectors. The SSBUV has now flown four times, over a thirty-month period beginning in October 1989. This paper deals with the calibration and radiometric stability before and after each of four Shuttle flights and is an update to the results reported after the first SSBUV flight. For the more recent flights, laboratory calibration precision continues to be better than 1%. Instrument sensitivity continued to degrade by 1% to 3% after each flight, and is wavelength dependent. Measurements of the solar irradiance in the wavelength region 200 nm to 400 nm have a precision of 1% to 2% from one flight to the next. Comparison of the SSBUV and the NOAA-11 SBUV-2 solar irradiance measurements indicates that the SBUV-2 instrument is degrading less than 1% per year at wavelengths longer than 300 nm and by as much as 6% per year at wavelengths shorter than 250 nm.

Space shuttle data and atmospheric models

Atmospheric density data obtained during the reentry of 22 Shuttle flights have been analyzed and compared with models. It was found that the density values from two flights that reentered through high latitudes were quite different from the values obtained from low and mid latitude flights. Data from a December high latitude flight agreed with models, although as low as 60% of the U.S. Standard Atmosphere, but the data from an October flight were as much as 25% below the October models, although 57% of the U.S. Standard. The difference was possibly due to the effects of particle precipitation. Data from the mid and low latitude flights, in general, agreed well with the models, with a mean deviation of −2.3% at 50km and −11% at 85km. The maximum variability at these altitudes was 8% and 22%, respectively. Most flights showed evidence of gravity waves above 70km, with largest amplitudes in summer, and little activity in the winter or at high latitudes. Data from three flights that reentered at a constant latitude of 27°N are close to the models near 50km, but are generally lower at higher altitudes and exhibit major variability above 70km, probably due to storm and convective activity. The results from three high inclination flights that reentered over the southern tropics agree with the models at 50km altitude, but at higher altitudes all the data are below the models. The conclusion is that the models for latitudes between 20°N and 20°S need to be revised.

Test and Evaluation of a Zero-G Treadmill Restraint System

Manned spaceflight missions result in human exposure to reduced gravity environments, during which the human body undergoes some pronounced physiological changes. Exercise has been identified as a practical and operationally acceptable countermeasure to the physiological responses to “zero-gravity”. At the National Aeronautics and Space Administration's Johnson Space Center, a new treadmill is under development for use on Shuttle flights. One of the main challenges of this project is the development of an effective restraint system. The restraint system must place a body weight load on the subject while the subject exercises in zero-gravity. Additionally, the restraint system must allow the subject to exercise in zero-gravity at various percent grades (treadmill slopes). This paper discusses the restraint system of a prototype treadmill and zero-gravity test results. The results indicate the manually operated, prototype restraint system has some limitations and that a real-time feedback system utilizing a servo operated adjustment mechanism would significantly enhance performance.

Shuttle entry air data system — An experimental investigation of calibration for ascent flight

An investigation into the calibration of the Shuttle Entry Air Data System (SEADS) has been conducted for the purpose of obtaining angle of attack and sideslip during ascent powered flight. The calibration methodology involves modeling a modified newtonian pressure distribution, corrected for interference, around the orbiter nosecap. Due to the lack of ascent configuration wind tunnel data resolution near the nosecap, the Ascent Air Data System (AADS) was used as a calibrator. The calibration curves were then used to reduce data from future Shuttle flights. Results from this calibration show that vehicle attitude can be determined to within six-tenths degree of pitch and sideslip when compared with the AADS. Calibration curves were then developed using data from two SEADS flights, and the comparison with the AADS system was improved to within one-half degree. Additional flights of the SEADS system should provide more flight calibration data and increase the accuracy of the ascent data reduction method. This paper details the calibration methodology and also presents the results of the calibration when applied to STS-28 and STS-32.

Shuttle flight to probe atmospheric chemistry

Shuttle flight to probe atmospheric chemistry