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Cape Canaveral, FL, United States

Toleman B.M.,United Space Alliance
AIAA Atmospheric Flight Mechanics Conference 2011 | Year: 2011

Destruction of a solid rocket stage of a launch vehicle can create a thermal radiation hazard for an aborting crew module. This hazard was assessed for the Constellation Program (Cx) crew and launch vehicle concept. For this concept, if an abort was initiated in first stage flight, the Crew Module (CM) would separate and be pulled away from the malfunctioning launch vehicle via a Launch Abort System (LAS). Having aborted the mission, the launch vehicle would likely be destroyed via a Flight Termination System (FTS) in order to prevent it from errantly traversing back over land and posing a risk to the public. The resulting launch vehicle debris field, composed primarily of first stage solid propellant, poses a threat to the CM. The harsh radiative thermal environment, caused by surrounding burning propellant debris, may lead to CM parachute failure. A methodology, detailed herein, has been developed to address this concern and to quantify the risk of first stage propellant debris leading to the thermal demise of the CM parachutes. Utilizing basic thermal radiation principles, a software program was developed to calculate parachute temperature as a function of time for a given abort trajectory and debris piece trajectory set. Two test cases, considered worst case aborts with regard to launch vehicle debris environments, were analyzed using the simulation: an abort declared at Mach 1 and an abort declared at maximum dynamic pressure (Max Q). For both cases, the resulting temperature profiles indicated that thermal limits for the parachutes were not exceeded. However, short duration close encounters by single debris pieces did have a significant effect on parachute temperature. Therefore while these two test cases did not indicate exceedance of thermal limits, in order to quantify the risk of parachute failure due to radiative effects from the abort environment, a more thorough probability-based analysis using the methodology demonstrated herein must be performed. © 2011 by the American Institute of Aeronautics and Astronautics, Inc. Source

Boehlert C.J.,Michigan State University | Li H.,Michigan State University | Wang L.,Michigan State University | Bartha B.,United Space Alliance
Advanced Materials and Processes | Year: 2010

In situ scanning electron microscopy (SEM) was applied on Inconel alloy 718 (IN 718) for slip system characterization and identification of the stress at which the slip systems were activated. Image acquisition time, which ranged between 60 and 90 seconds, revealed the displacement rate of 0.004 mm/s, which corresponds to a strain rate of approximately 10-3/s. Surface grain orientations with respect to the tensile direction identified using EBSD allowed for identification of the orientation of the slip planes. A Schmid factor, a geometrical measurement indicating the resolved shear stress on a specific slip system with respect to loading direction, of approximately zero indicates that a crystal is in a difficult orientation for activation of a particular slip system. The slip bands in grain 17 are found to have the highest Schmid factor of 0.46. Two activated slip systems are identified in grain 52 and grain 64. Source

Muravyov A.A.,United Space Alliance
World Academy of Science, Engineering and Technology | Year: 2011

A minimal complexity version of component mode synthesis is presented that requires simplified computer programming, but still provides adequate accuracy for modeling lower eigenproperties of large structures and their transient responses. The novelty is that a structural separation into components is done along a plane/surface that exhibits rigid-like behavior, thus only normal modes of each component is sufficient to use, without computing any constraint, attachment, or residual-attachment modes. The approach requires only such input information as a few (lower) natural frequencies and corresponding undamped normal modes of each component. A novel technique is shown for formulation of equations of motion, where a double transformation to generalized coordinates is employed and formulation of nonproportional damping matrix in generalized coordinates is shown. Source

Holt G.N.,NASA | Getchius J.,On Orbit GNC | Tracy W.H.,United Space Alliance
Advances in the Astronautical Sciences | Year: 2011

A crewed mission to a Near-Earth Object (NEO) was recently identified as a NASA Space Policy goal and priority. In support of this goal, a study was conducted to identify the initial considerations and performing the navigation and flight dynamics talks of this mission class. Although missions to a NEO are not new, the unique factors involved in human spaceflight present challenges that warrant special examination. During the cruise phase of the mission, one of the moist challenging factors is the noisy acceleration environment associated with a crewed vehicle. Additionally, the presence of a human crew necessitaies a timely return trip, which may need to be expedited in an emergency situation where the mission is aborted. Tracking, navigation, and targeting results are shown for sample human-class trajectories to NEOs. Additionally, the benefit of in-situ navigation beacons on robodic precursor missions is presented. This mission class will require a longer duration flight than Apollo and, unlike previous human missions, there will likely be limited communication and tracking avalability. Thus will necessitate the use of more onboard navigation and targeaing capabilities. Finally, the rendezveue and proximity operations near an esteroid will be unlike anything previously attempted in a crewed spaceflight. The unknown gravitational environment and physical surface properties of the NEO may cause the rendezvous to behave differently than expected. Symoiosis of the human pilot and onboard navigation/targeting are presented which give additional robustness to unforeseen perturbations. Source

Rohrkaste G.R.,United Space Alliance
AIAA SPACE Conference and Exposition 2011 | Year: 2011

This paper summarizes recent research and trade studies of the considerations for using a body of water (ocean) as a spaceport of operations for returning capsules. It will discuss several platforms (ships) that are commercially available to conduct the operations from. Discuss the results of trade studies on alternate methods of recovering the capsule from the water's surface on to the vessel. It will also review tests of various support equipment for towing, lifting and righting the capsule. These considerations are independent of capsule shape but a review of the hydrodynamic considerations of three capsule shapes (gumdrop, headlight and scram) will be briefly discussed as they influence water recovery. © 2011 by United Space Alliance, LLC. Source

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