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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Spaceflight Medical Evacuation Risk Assessment Principles - A Qualitative Investigation

BACKGROUND Future human space exploration beyond Low Earth Orbit (LEO) will require innovative solutions in many areas, primarily those that provide direct medical support to crew on long-duration missions and optimize their health and performance. The associated challenges therein will be numerous, including but not necessarily limited to extended one-way or "asynchronous" communication delays, minimal to non-existent resupply, and a prolonged transit time to "definitive care" ranging from 3-days to 9-months. At the same time, long-duration exploration spacecraft and crew will face restrictions on mass, power, volume, and data far more significant than that seen in current LEO settings. Given these limitations, medical risk assessment is of primary importance, especially evaluating the implications of a medical evacuation of an ill or injured crewmember. Such evacuations are complicated, potentially dangerous, and well may be impossible in certain phases of the mission. Regardless, such issues must be weighed against the risks of the injured crew remaining aboard a spacecraft with limited medical resources. OBJECTIVE This qualitative study drew from the experiences of subject matter experts (SMEs) in spaceflight and appropriate analog environments (i.e., military, disaster, and extreme environment fields) to identify unique principles common amongst medical evacuation considerations helpful in informing future risk assessment tools. Appropriate analog environments included austere operational settings where multiple factors (weather, logistics/limited resupply, denied/extreme environments, and patient condition) resulted in a limited ability to provide definitive local medical care. The fundamental principles in question revolved around scenarios where evacuation became a complicating yet necessary consideration and where life-threatening medical concerns had to be weighed against critical mission objective(s). The primary authors collected semi-structured data gathered through in-depth interviews with 16 subject matter experts (SMEs). Interview questions investigated how these SMEs consider and weigh the attendant risks present in medical evacuation scenarios. Among the critical questions posed were those that sought to understand how the SME balanced the challenges and requirements of medical evacuation (or keeping an injured patient "on-site" aka: "prolonged field care") against the evacuation operation's risks on impacting overarching mission success. The team analyzed interview transcripts for common themes and principles using the qualitative methods of thematic analysis based on consensus, co-occurrence, and comparison. As a result, nine primary risk consideration themes and nine contributing factor themes emerged, all of which will ideally inform future medical evacuation decision-making tools and operational decision-making for exploration class missions. Specific aims for this study included: 1. Identification of common principles used to assess risks and benefits of medical evacuations in extreme environments 2. Identification of common points of friction or complication and challenges in extreme environment evacuations

A T Almand↗
NASA NTRS2011

Fluid Line Evacuation and Freezing Experiments for Digital Radiator Concept

The digital radiator technology is one of three variable heat rejection technologies being investigated for future human-rated NASA missions. The digital radiator concept is based on a mechanically pumped fluid loop with parallel tubes carrying coolant to reject heat from the radiator surface. A series of valves actuate to start and stop fluid flow to di erent combinations of tubes, in order to vary the heat rejection capability of the radiator by a factor of 10 or more. When the flow in a particular leg is stopped, the fluid temperature drops and the fluid can freeze, causing damage or preventing flow from restarting. For this reason, the liquid in a stopped leg must be partially or fully evacuated upon shutdown. One of the challenges facing fluid evacuation from closed tubes arises from the vapor generated during pumping to low pressure, which can cause pump cavitation and incomplete evacuation. Here we present a series of laboratory experiments demonstrating fluid evacuation techniques to overcome these challenges by applying heat and pumping to partial vacuum. Also presented are results from qualitative testing of the freezing characteristics of several different candidate fluids, which demonstrate significant di erences in freezing properties, and give insight to the evacuation process.

human space flight↗
NASA NTRS2018

Evacuated Airship for Mars Missions: NIAC Phase I, 2017

An evacuated or vacuum airship relies on the same principle of buoyancy used by standard balloons. However, unlike a balloon which uses a lighter than air gas to displace air and provide lift, the vacuum airship leverages a rigid structure to maintain a vacuum and displace air, thereby providing buoyancy. This method is similar to how a ship uses a rigid structure to displace water and fill the space with air; an evacuated airship uses the same mechanism, except air is displaced and the space remains vacant. Using this method, the evacuated airship is capable of utilizing the full potential of the displaced mass of air, which has interesting implications in the Martian atmosphere. Unlike other aerial vehicles, which are at a disadvantage in Martian atmospheric conditions, the evacuated airship benefits from the Martian atmosphere by virtue of the temperature and molecular composition. As a result, the evacuated airship offers an unprecedented payload capacity and, if implemented, may be used to transport current and future scientific instruments, other vehicles, rovers, and possibly even human habitations. A standard dirigible or balloon for Mars would have a severely limited span of operation and a very narrow field of study, nearly exclusively the atmosphere, but a vacuum airship can be used as a long term tool for many different missions: transportation, ground study, communications, atmospheric study, etcetera, thereby making it a far more economically sensible choice

Clarke, John-Paul↗
NASA NTRS1972

A method for defining down-wind evacuation areas for transportation accidents involving toxic propellant spills

Evacuation areas for accidental spills of toxic propellants along rail and highway shipping routes are defined to help local authorities reduce risks to people from excessive vapor concentrations. These criteria along with other emergency information are shown in propellant spill cards. The evacuation areas are based on current best estimates of propellant evaporation rates from various areas of spill puddles. These rates are used together with a continuous point-source, bi-normal model of plume dispersion. The rate at which the toxic plume disperses is based on a neutral atmospheric condition. This condition, which results in slow plume dispersion, represents the widest range of weather parameters which could occur during the day and nighttime periods. Evacuation areas are defined by the ground level boundaries of the plume within which the concentrations exceed the toxic Threshold Limit Value (TLV) or in some cases the Emergency Exposure Limit (EEL).

Siewert, R. D.↗
NASA NTRS1983

A computer simulation of aircraft evacuation with fire

A computer simulation was developed to assess passenger survival during the post-crash evacuation of a transport category aircraft when fire is a major threat. The computer code, FIREVAC, computes individual passenger exit paths and times to exit, taking into account delays and congestion caused by the interaction among the passengers and changing cabin conditions. Simple models for the physiological effects of the toxic cabin atmosphere are included with provision for including more sophisticated models as they become available. Both wide-body and standard-body aircraft may be simulated. Passenger characteristics are assigned stochastically from experimentally derived distributions. Results of simulations of evacuation trials and hypothetical evacuations under fire conditions are presented.

Middleton, V. E.↗
NASA NTRS1984

Methods to recover the narrow Dicke sub-Doppler feature in evacuated wall-coated cells without restrictions on cell size

The hyperfine resonance observed in evacuated wall-coated cells with dimensions lambda/2 (lambda is the hyperfine resonance wavelength) consists of a narrow Dicke sub-Doppler linewidth feature, the spike, superimposed on a broad pedestal. The hydrogen maser provides a classic example of this lineshape. As cell size is increased, an effect unique to evacuated wall-coated cells occurs. Certain combinations of microwave field distribution and cell size result in a lineshape having a pedestal with a small spike feature or only the broad pedestal with no spike. Such conditions are not appropriate for atomic frequency standard applications. The cause of the evacuated wall-coated cell lineshape is reviewed and methods to recover the narrow spike feature without restrictions on cell size is discussed. One example is a cell with dimensions having equal volumes of exposure to opposite phases of the microwave magnetic field.

Robinson, H. G.↗
NASA NTRS2007

Haughton-Mars Project/NASA 2006 Lunar Medical Contingency Simulation: Equipment and Methods for Medical Evacuation of an Injured Crewmember

Introduction: Achieving NASA's Space Exploration Vision scientific objectives will require human access into cratered and uneven terrain for the purpose of sample acquisition to assess geological, and perhaps even biological features and experiments. Operational risk management is critical to safely conduct the anticipated tasks. This strategy, along with associated contingency plans, will be a driver of EVA system requirements. Therefore, a medical contingency EVA scenario was performed with the Haughton-Mars Project/NASA to develop belay and medical evacuation techniques for exploration and rescue respectively. Methods: A rescue system to allow two rescuer astronauts to evacuate one in incapacitated astronaut was evaluated. The systems main components were a hard-bottomed rescue litter, hand-operated winch, rope, ground picket anchors, and a rover-winch attachment adapter. Evaluation was performed on 15-25deg slopes of dirt with embedded rock. The winch was anchored either by adapter to the rover or by pickets hammered into the ground. The litter was pulled over the surface by rope attached to the winch. Results: The rescue system was utilized effectively to extract the injured astronaut up a slope and to a waiting rover for transport to a simulated habitat for advanced medical care, although several challenges to implementation were identified and overcome. Rotational stabilization of the winch was found to be important to get maximize mechanical advantage from the extraction system. Discussion: Further research and testing needs to be performed to be able to fully consider synergies with the other Exploration surface systems, in conducting contingency operations. Structural attachment points on the surface EVA suits may be critical to assist in incapacitated evacuation. Such attach points could be helpful in microgravity incapacitated crewmember transport as well. Wheeled utility carts or wheels that may be attachable to a litter may also aid in extraction and transport. Utilizing parts of the rover (e.g. seats) to deploy as a litter may be considered. Testing in simulated 1/6-g to determine feasibility of winch operation and anchor establishment will further reduce implementation uncertainties.

Chappell, S. P.↗
NASA NTRS2017

Fluid Transient Analysis during Priming of Evacuated Line

Water hammer analysis in pipe lines, in particularly during priming into evacuated lines is important for the design of spacecraft and other in-space application. In the current study, a finite volume network flow analysis code is used for modeling three different geometrical configurations: the first two being straight pipe, one with atmospheric air and other with evacuated line, and the third case is a representation of a complex flow network system. The numerical results show very good agreement qualitatively and quantitatively with measured data available in the literature. The peak pressure and impact time in case of straight pipe priming in evacuated line shows excellent agreement.

Bandyopadhyay, Alak↗
NASA NTRSDate not supplied

Improving Quantification of Medical Evacuation Risk for Human Spaceflight in the IMPACT Model

Traditionally, mission planners have used a heuristic and qualitative approach to design medical systems based on prior experience however this approach may result in high variability and implicit bias to design and could put missions and crewmembers at risk. The Informing Mission Planning through Analysis of Complex Tradespaces (IMPACT) tool is a probabilistic risk assessment tool designed by NASA to model medical risk in long duration missions outside of low earth orbit (LEO). This tool can quantify risk metrics such as risk of crewmember death, loss of crew task time, and the need for medical evacuation to better inform and augment the more traditional approach to medical system design. The risk metric of Return to Definitive Care (RTDC) represents the likelihood of requiring medical evacuation and has been difficult to quantify in a reliable and standardized manner. Initial development of the RTDC metric was constrained due to the complexity of a medical evacuation decision and the lack of prior spaceflight data and this presentation will discuss the review and improvement process used to increase model accuracy and fidelity.

Prashant Parmar↗
NASA NTRS2023

A Qualitative Investigation of Space Exploration Medical Evacuation Risks

Exploration beyond low Earth orbit requires innovative solutions to support the crew medically, especially as the opportunity for timely evacuation to Earth diminishes. This includes assessing the risks and benefits that a complicated medical evacuation (MEDEVAC) poses to the injured crewmember and crew and to accomplishing the mission. This qualitative study identifies common MEDEVAC risk assessment principles used in spaceflight and other extreme environments to better inform future risk assessment tools and exploration mission concepts.

cislunar↗
NASA NTRS1966

Seal-off assembly permits rapid evacuation of air from containers

Seal-off assembly which permits rapid container evacuation using large diameter tubing has a vacuum valve that permits sealing plate transfer from the vacuum valve stem to the container after evacuation. The sealing plate can be reused repeatedly. This device can repump in case of a small leak without exposing the container to the atmosphere.

Demers, R. R.↗
NASA NTRS1972

Prediction of pressure during evacuation of multilayer insulation.

Description of an improved analytical procedure for predicting the pressure time history during evacuation of multilayer-insulation thermal-protection systems. To evaluate the performance of the proposed analysis and to demonstrate its usefulness as a design tool, a comparison is presented of the experimentally measured and predicted evacuation pressure histories for a laboratory-scale model multilayer insulation blanket.

Glassford, A. P. M.↗
NASA NTRS1972

Evacuation areas for transportation accidents involving propellant tank pressure bursts

Evacuation areas are defined for those transportation accidents where volatile chemical propellant tanks are exposed to fire in the wreckage and eventually explode with consequent risks from fragments in surrounding populated areas. An evacuation area with a minimum radius of 600 m (2000 ft) is recommended to limit the statistical probability of fatality to one in 100 such accidents. The result was made possible by the derivation of a distribution function of distances reached by fragments from bursting chemical car tanks. Data concerning fragments was obtained from reports or tank car pressure bursts between 1958 and 1971.

Siewert, R. D.↗
NASA NTRS1972

Evacuation areas for transportation accidents involving propellant tank pressure bursts

Evacuation areas are defined for those transportation accidents where volatile chemical propellant tanks are exposed to fire in the wreckage and eventually explode with consequent risks from fragments in surrounding populated areas. An evacuation area with a minimum radius of 600 m is recommended to limit the statistical probability of fatality to one in 100 such accidents. The result of this study was made possible by the derivation of a distribution function of distances reached by fragments from bursting chemical car tanks. Data concerning fragments were obtained from reports of tank car pressure bursts between 1958 and 1971.

Siewert, R. D.↗
NASA NTRS1979

Low cost vee-trough evacuated tube collector module

A low cost solar collector capable of operating at 150-200 C is described. An evacuated tube receiver is combined with asymmetric vee-trough concentrators. Peak efficiencies of about 40% at 120 C and 30% at 180 C are expected. Predicted future collector cost is $70/sq m which yields an energy cost of $4.20/GJ at 120 C. During the development of the vee trough/evacuated tube collector both mathematical models to predict thermal and optical performance were developed and tests run to verify theory. The asymmetric vee trough concentrator increases the solar flux intensity for an average value of 2 for year-round performance. Optimized collector module has reflector angles of 55 deg/85 deg. The aperture plane is tilted to the latitude. The reflector is made of electropolished aluminum. The supporting frame is formed by bending sheet metal. Evacuated tube receivers are Pyrex, 15 cm diam and 2.4 m long. The module has 12 tubes on right and left sides altogether. Attainable operation at temperatures on the order of 150-200 C are suitable for absorption refrigeration and power generation via Rankine engines.

Selcuk, M. K.↗
NASA NTRS1981

Evacuation-induced pressure differentials in multilayer insulation systems

The pressure differentials induced across three types of multilayer insulation systems during evacuation have been measured and compared with values predicted using an idealized parallel plate geometric model. The systems tested were double-aluminized Mylar with a Tissuglas or silk net spacer and crinkled single-aluminized Mylar. Test samples were circular. The influence of purge gas type, layer density, sample diameter, and temperature was systematically investigated. The experimental approach was to measure the absolute pressure history and corresponding pressure differential induced across the insulation during evacuation. The measured pressure differentials were nondimensionalized and compared with those predicted by the parallel plate model as a function of Knudsen number. It was concluded that the parallel plate model is adequate for making engineering analyses. The influence of all parameters, except layer density, is well represented by the model. Representation of the influence of layer density is less satisfactory, but can be improved by modification of the flat plate model to allow for the more obvious practical nonidealities, such as crinkling, or the presence of a net spacer.

Glassford, A. P. M.↗
NASA NTRS1984

Diode laser 87Rb optical pumping in an evacuated wall-coated cell

The evacuated wall coated sealed cell coupled with diode laser optical pumping offers a number of attractive potential advantages for use in Rb or Cs atomic frequency standards. An investigation of systematic effects is required to explore possible limitations of the technique. The use of diode laser optical pumping of 87 Rb in an evacuated wall coated sealed cell is presented. Experimental results/discussion to be presented include the signal strength and line broadening of the 0 - 0 hyperfine resonance as a function of light intensity for the D1 optical transitions (F - F prime) - (2 1 prime) and (2 - 2 prime), shift of the 0 - 0 hyperfine frequency as a function of laser intensity and de-tuning from optical resonance, and diode laser frequency stabilization techniques.

Lee, W. K.↗