Ignition delay times of methane-n-hexane-oxygen mixtures were studied experimentally and numerically in a wide temperature range (640-2335 K) using both a rapid compression machine (RCM) and a shock tube (ST). The RCM results demonstrated a two-stage ignition and negative temperature coefficient (NTC) behavior. Increasing n-hexane concentration, pressure and equivalence ratio shortened the ignition delay time. For the ST experiments, the addition of 10% n-hexane (relative to methane) can reduce the ignition delay time dramatically. However, no further reduction effect can be achieved with increasing addition of n-hexane from 10% to 20%. In addition, increasing equivalence ratio reduces the effect of n-hexane addition on ignition delay time. Three detailed chemical mechanisms, CaltechMech, GalwayMech and LLNLMech, were evaluated based on a quantitative error analysis. LLNLMech and CaltechMech demonstrated the best performance in the RCM and ST temperature ranges, respectively. Chemical kinetic analyses showed that the addition of n-hexane to methane provides some chemical pathways not available for methane oxidation which result in the production of active radicals and eventually accelerate the ignition of the methane-oxygen mixtures. The crucial intermediate species for the ignition process are H 2 O 2 and H under RCM and ST conditions, respectively.

The present paper focuses on the chemical kinetics of the ignition of premixed nhexane-air atmospheres by a moving hot sphere with emphasis on the role of lowtemperature chemistry (T<1000 K). Experiments were performed to measure the minimum surface temperature for ignition of a propagating flame and non-reactive two-dimensional simulations were performed to estimate the temperature a parcel of fluid experiences as it travels within the thermal boundary layer near the surface of the sphere. Reactive simulations using detailed reaction models and a one-step model were used to investigate the chemical reaction dynamics in a constant pressure reactor with a variable heat transfer coefficient which reproduces the temperature history. It was found that, under the specific conditions studied, the chemistry is activated at T>1000 K with no noticeable impact of the low-temperature chemical pathways.

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In 2011, the Keck Institute for Space Studies hosted the Caltech Space Challenge, a week long workshop/competition directed towards the President's initiative of sending astronauts to an asteroid by 2025. Two teams composed of 16 students each, representing 12 different nations, competed to prepare a mission proposal by the end of the week. This report highlights some of the work done by Team Voyager. Not only is this work useful in showing that a manned mission to a Near-Earth Object is feasible by 2025, but it also demonstrates the utility of intense, relatively short student competitions. This study is an outline of Vault-1, a proposed human mission to a Near-Earth Object. In addition to continuing human exploration, Vault-1 aims to make new discoveries about the origins of the Solar System, to develop technologies geared towards deep space exploration and a manned Mars mission, and to gain critical knowledge and experience to better protect Earth from future asteroid impacts. The primary target of this endeavor is 1999AO10, an asteroid that is larger than 30 m that also has an achievable mission duration of less than 200 days. 2000SG344 is a viable secondary target. Vault-1 will nominally carry 3 crew members to 1999AO10; after 14 days at the asteroid, the astronauts will return safely to the Earth with samples from the asteroid.