ALBERT

Description: A recent study by NASA indicates that the implementation of international orbital debris mitigation measures alone will not prevent a significant increase in the artificial Earth satellite population, beginning in the second half of this century. Whereas the focus of the aerospace community for the past 25 years has been on the curtailment of the generation of long-lived orbital debris, active remediation of the current orbital debris population should now be reconsidered to help preserve near-Earth space for future generations. In particular, we show in this paper that even if launch operations were to cease today, the population of space debris would continue to grow. Further, proposed remediation techniques do not appear to offer a viable solution. We therefore recommend that, while the aerospace community maintains the current debris-limiting mission regulations and postmission disposal procedures, future emphasis should be placed on finding new remediation technologies for solving this growing problem. Since the launch of Sputnik 1, space activities have created an orbital debris environment that poses increasing impact risks to existing space systems, including human space flight and robotic missions (1, 2). Currently, more than 9,000 Earth orbiting man-made objects (including many breakup fragments), with a combined mass exceeding 5 million kilograms, are tracked by the US Space Surveillance Network and maintained in the US satellite catalog (3-5). Three accidental collisions between cataloged satellites during the period from late 1991 to early 2005 have already been documented (6), although fortunately none resulted in the creation of large, trackable debris clouds. Several studies conducted during 1991-2001 demonstrated, with assumed future launch rates, the unintended growth potential of the Earth satellite population, resulting from random, accidental collisions among resident space objects (7-13). In some low Earth orbit (LEO) altitude regimes where the number density of satellites is above a critical spatial density, the production rate of new satellites (i.e., debris) due to collisions exceeds the loss of objects due to orbital decay. NASA s evolutionary satellite population model LEGEND (LEO-to-GEO Environment Debris model), developed by the Orbital Debris Program Office at the NASA Lyndon B. Johnson Space Center, is a high fidelity three-dimensional physical model that is capable of simulating the historical satellite environment, as well as the evolution of future debris populations (14, 15). The subject study assumed no rocket bodies and spacecraft were launched after December 2004, and no future disposal maneuvers were allowed for existing spacecraft, few of which currently have such a capability. The rate of satellite explosions would naturally decrease to zero within a few decades as the current satellite population ages. The LEGEND future projection adopts a Monte Carlo approach to simulate future on-orbit explosions and collisions. Within a given projection time step, once the explosion probability is estimated for an intact object, a random number is drawn and compared with the probability to determine if an explosion would occur. A similar procedure is applied to collisions for each pair of target and projectile involved within the same time step. Due to the nature of the Monte Carlo process, multiple projection runs must be performed and analyzed before one can draw reliable and meaningful conclusions from the outcome. A total of fifty, 200-year future projection Monte Carlo simulations were executed and evaluated (16).

Description: In January 2006, the Stardust spacecraft returned the first in situ collection of samples from a comet, and the first samples of contemporary interstellar dust. Stardust is the first US sample return mission from a planetary body since Apollo, and the first ever from beyond the moon. This handbook is a basic reference source for allocation procedures and policies for Stardust samples. These samples consist of particles and particle residues in aerogel collectors, in aluminum foil, and in spacecraft components. Contamination control samples and unflown collection media are also available for allocation.

Description: This chapter reviews the past and current projects on artificial gravity during space missions. The idea of a rotating wheel-like space station providing artificial gravity goes back in the writings of Tsiolkovsky, Noordung, and Wernher von Braun. Its most famous fictional representation is in the film 2001: A Space Odyssey, which also depicts spin-generated artificial gravity aboard a space station and a spaceship bound for Jupiter. The O Neill-type space colony provides another classic illustration of this technique. A more realistic approach to rotating the space station is to provide astronauts with a smaller centrifuge contained within a spacecraft. The astronauts would go into it for a workout, and get their gravity therapeutic dose for a certain period of time, daily or a few times a week. This simpler concept is current being tested during ground-based studies in several laboratories around the world.

Description: In 2004 NASA began investigation of a robotic servicing mission for the Hubble Space Telescope (HST). Such a mission would require estimates of the HST attitude and rates in order to achieve a capture by the proposed Hubble robotic vehicle (HRV). HRV was to be equipped with vision-based sensors, capable of estimating the relative attitude between HST and HRV. The inertial HST attitude is derived from the measured relative attitude and the HRV computed inertial attitude. However, the relative rate between HST and HRV cannot be measured directly. Therefore, the HST rate with respect to inertial space is not known. Two approaches are developed to estimate the HST rates. Both methods utilize the measured relative attitude and the HRV inertial attitude and rates. First, a nonlinear estimator is developed. The nonlinear approach estimates the HST rate through an estimation of the inertial angular momentum. The development includes an analysis of the estimator stability given errors in the measured attitude. Second, a linearized approach is developed. The linearized approach is a pseudo-linear Kalman filter. Simulation test results for both methods are given, including scenarios with erroneous measured attitudes. Even though the development began as an application for the HST robotic servicing mission, the methods presented are applicable to any rendezvous/capture mission involving a non-cooperative target spacecraft.

Description: Surface Thermal Profiles of Eagle Picher rabbit-ear 50Ah NiH2 and of Saft 40 Ah Li-ion cylindrical cells have been studied using ThermCAM S60 FLIR Systems. Popping Phenomenon in NiH2 cell is demonstrated Temperature gradient in NiH2 is slightly higher than normally considered, for example. Middle of stack to top or bottom is about 12.9 C compared to 〈7 C (may be due to passive cooling). Less than 1 C thermal gradient on the Li-Ion cell vessel surface. Significantly lower heat generation in Li-Ion cell compared to NiH2 cell. -May be due to a favorable charge method used for Li-Ion cell.

Description: Rechargeable Lithium-ion batteries have been operating successfully on both Spirit and Opportunity rovers for the last two years, which includes six months of Assembly Launch and Test Operations (ATLO), seven months of cruise and about eleven months of surface operations. The Battery Control Boards designed and fabricated in-house would protect cells against overcharge and over-discharge and provide cell balance. Their performance has thus far been quite satisfactory. The ground data o the mission simulation battery project little capacity loss of less than 3% during cruise and 180 sols. Batteries are poised to extend the mission beyond six months, if not a couple of years.

Description: AEA selection and successful Interim Design Review for AHPS proves maturity of small cell approach for very large batteries. Cells show excellent opportunity for battery mass reduction for AHPS and other low cycle applications. Lack of cycle and extended calendar life make EOL battery performance difficult (AHPS 8 year mission). Preliminary design, AEA retained SONY 18650HC cell as baseline: a) Well characterized performance; b) Wealth of safety test data.

Description: Positive Temperature Coefficient (PTC) provides adequate sustained hard short protection for AEA batteries with up to 8 cells in series. PTC cannot protect against sustained hard short in AEA batteries with 10 cells or more in series. Protective fused connector is a proven way to protect larger batteries from hard short damage: a) Hard short not credible in unmanned missions; b) However, recommended during ground handling; c) Inexpensive item. Preliminary diode protection scheme has passed manned space safety requirements for high voltage batteries. SCM confirmed fused connector did not affect battery health, however, this affect of hard short on the its long calendar and cycle life performance needs to be verified.

Description: Need for technology verification for aerospace applications. Structure flexible program that will allow assessment of current technology capabilities. Provide information about various vendors. Provide for assessment of technology developments. Developed statistical DOE to interpret relationships in data and to address program test goals and resource limitations. Data will be used to develop a model to predict life of cells as a function of DOD, temperature, and EOCV.

Description: Battery cell wear out mechanisms and signatures are examined and compared to orbital data from the six on-orbit Hubble Space Telescope (HST) batteries, and the Flight Spare Battery (FSB) Test Bed at Marshall Space Flight Center (MSFC), which is instrumented with individual cell voltage monitoring. The on-orbit HST batteries were manufactured on an expedited basis after the Challenger Shuttle Disaster in 1986. The original design called for the HST to be powered by six 50 Ah Nickel Cadmium batteries, which would have required a shuttle mission every 5 years for battery replacement. The decision to use NiH2 instead has resulted in a longer life battery set which was launched with HST in April 1990, with a design life of 7 years that has now exceeded 14+ years of orbital cycling. This chart details the specifics of the original HST NiH2 cell design. The HST replacement batteries for Service Mission 4, originally scheduled for Spring 2005, are currently in cold storage at NASA Goddard Space Flight Center (GSFC). The SM4 battery cells utilize slurry process electrodes having 80% porosity.