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Results for “CNSR”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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10 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Thermal evolution of Comet P/Tempel 1 - Representing the group of targets for the CRAF and CNSR missions

A numerical definition of the thermal evolution of spherically symmetric models of the nucleus in the orbit of Comet P/Tempel-1 is presently used to ascertain the properties of the outer layers of comets under consideration for the future Comet Rendezvous and Asteroid Flyby and the Comet Nucleus Sample Return missions. Evolutionary sequences are computed for different values of density, dust/ice mass ratio, and the dust fraction not lost with ice sublimation. It is found that inner and outer surface temperatures of the dust mantle are comparatively insensitive to parameter changes, and that the total thickness of the crystalline ice layer between the dust mantle and the amorphous ice core will make it difficult for the comet-mission probes to sample pristine ice.

Bar-Nun, Akiva↗
NASA NTRS1987

Application of solar electric propulsion to future planetary missions

Application of solar electric propulsion (SEP) to several near term planetary missions has been investigated and is described in this paper. The missions under consideration include a comet rendezvous-asteroid flyby mission (CRAF), an orbiter mission to Saturn (CASSINI) and a comet nucleus sample return mission (CNSR). Advances in both thruster and solar array technology indicate that these missions could benefit by use of a moderate size solar electric propulsion system. The trajectory scenarios considered in this paper include a solar electric earth gravity assist (SEEGA) mode for all three missions and a SEP rendezvous mode for both the CRAF and CNSR missions. In addition an all SEP propulsion mode and a hybrid SEP-chemical propulsion mode is described for the CNSR mission.

Sauer, Carl G., Jr.↗
NASA NTRS1989

Candidate sample acquisition systems for the Rosetta

The Comet Nucleus Sample Return (CNSR) mission, one of the four cornerstones of the ESA scientific program, is one of the most complex space ventures within the next century, both from technological and deep space exploration point of view. In the Rosetta scenario the sample acquisition phase represents the most critical point for the global mission's success. The proposed paper illustrates the main results obtained in the context of the CNSR-SAS ongoing activity. The main areas covered are related to: (1) sample properties characterization (comet soil model, physical/chemical properties, reference material for testing); (2) concepts identification for coring, shovelling, harpooning and anchoring; (3) preferred concept (trade off among concepts, identification of the preferred configuration); and (4) proposed development activity for gaining the necessary confidence before finalizing the CNSR mission. Particular emphasis will be given to the robotic and flexibility aspects of the identified sample acquisition systems (SAS) configuration, intended as a means for the overall system performance enhancement.

Magnani, P. G.↗
NASA NTRS2000

Ion propulsion system design for the Comet Nucleus Sample Return mission

One of the first science missions to use solar electric propulsion (SEP) may be the Comet Nucleus Sample Return (CNSR) mission which is designed to return samples of volatiles and dust from the nucleus of a comet. The use of SEP for CNSR makes the mission affordable and scientifically more attractive because it enables the use of a smaller, lower cost launch vehicle and it significantly reduces the time required to return samples to the Earth.

CNSR↗
NASA NTRS1989

Planetary protection issues for sample return missions

Planetary protection (PP) issues for both a comet nucleus sample return (CNSR) mission and a Mars rover sample return (MRSR) mission are discussed, with special attention given to the PP requirements for such missions, the exobiology science objectives for the CNSR and MRSR missions, and a qualitative PP risk assessment for both mission types. A set of contamination control procedures for both missions is presented, which identify procedures for each of the mission phases (i.e., the prelaunch, launch, sample handling, transit vehicle, and earth return). Recommendations for further research and technology development are discussed.

Devincenzi, D. L.↗
NASA NTRS1988

Ion propulsion system design and throttling strategies for planetary missions

This paper describes recent advances in ion propulsion system design which promise to increase the propulsion system reliability by reducing the overall system complexity. The greatest simplification in the overall propulsion system operation is accomplished through a change in the ion engine throttling strategy. By using three grid optics it is possible to effect engine throttling at a constant beam curent over at least a 3.8 to 1 variation in input power. Throttling at a constant beam current results in a single discharge chamber operating point and eliminates the need for active propellant flow controllers and complex engine throttling software. Detailed mission analysis calculations for a CNSR mission performed using this constant beam current throttling strategy indicate only a small reduction in delivered payload and increase in required propellant relative to a conventional throttling profile based on varying the beam curent.

Garner, Charles E.↗
NASA NTRS1989

Experimental studies of gas trapping in amorphous ice and thermal modelling of comets: Implications for Rosetta

The trapping of mixtures of CO, CH4, N2 and Ar in amorphous water ice was studied experimentally. It is shown that the ice particles could not have been formed at a higher temperature and, subsequently, cool down. Experiments where ice was deposited at elevated temperatures, then cooled down and gas was flowed into the ice, showed that the amount of trapped gas depends only on the highest temperature at which the ice was formed, or resided, prior to cooling and gas flow into it. Consequently, the cometary ice had to be formed at approx. 48 K and the ice is therefore amorphous. The thermal profile of a comet in Halley's orbit was calculated, including the build-up of an insulating dust layer. It was found that an insulating dust layer a few cm thick is enough to choke most of the water emission from the surface. A similar thermal model was calculated for comet P/Temple-1, a candidate for both CRAF and Rosetta (CNSR) missions. The temperature at a depth of 10 m is approx. 160 K for all models considered and, hence, the ice at this depth is crystalline. A crystalline ice layer 40 to 240 m thick was found to overly the gas-laden amorphous ice. Consequently, it should be difficult for the probes of the two comet missions to sample pristine amorphous ice, unless they are aimed at the bottom of an active crater.

Bar-Nun, Akiva↗
NASA NTRS1992

Comet nucleus and asteroid sample return missions

Three Advanced Design Projects have been completed this academic year at Penn State. At the beginning of the fall semester the students were organized into eight groups and given their choice of either a comet nucleus or an asteroid sample return mission. Once a mission had been chosen, the students developed conceptual designs. These were evaluated at the end of the fall semester and combined into three separate mission plans, including a comet nucleus same return (CNSR), a single asteroid sample return (SASR), and a multiple asteroid sample return (MASR). To facilitate the work required for each mission, the class was reorganized in the spring semester by combining groups to form three mission teams. An integration team consisting of two members from each group was formed for each mission so that communication and information exchange would be easier among the groups. The types of projects designed by the students evolved from numerous discussions with Penn State faculty and mission planners at the Johnson Space Center Human/Robotic Spacecraft Office. Robotic sample return missions are widely considered valuable precursors to manned missions in that they can provide details about a site's environment and scientific value. For example, a sample return from an asteroid might reveal valuable resources that, once mined, could be utilized for propulsion. These missions are also more adaptable when considering the risk to humans visiting unknown and potentially dangerous locations, such as a comet nucleus.

Source record↗
NASA NTRS2012

Autonomous Onboard Science Data Analysis for Comet Missions

Coming years will bring several comet rendezvous missions. The Rosetta spacecraft arrives at Comet 67P/Churyumov-Gerasimenko in 2014. Subsequent rendezvous might include a mission such as the proposed Comet Hopper with multiple surface landings, as well as Comet Nucleus Sample Return (CNSR) and Coma Rendezvous and Sample Return (CRSR). These encounters will begin to shed light on a population that, despite several previous flybys, remains mysterious and poorly understood. Scientists still have little direct knowledge of interactions between the nucleus and coma, their variation across different comets or their evolution over time. Activity may change on short timescales so it is challenging to characterize with scripted data acquisition. Here we investigate automatic onboard image analysis that could act faster than round-trip light time to capture unexpected outbursts and plume activity. We describe one edge-based method for detect comet nuclei and plumes, and test the approach on an existing catalog of comet images. Finally, we quantify benefits to specific measurement objectives by simulating a basic plume monitoring campaign.

comets↗