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Commercial Human Spaceflight Working Group -The Space Medicine Association (SMA) been asked by Dr. Rayman and the President of AsMA, Andy Belenkes, to form a working group to address medical issues related to Commercial Human Spaceflight. The following participants have agreed to participate in the working group from commercial spaceflight industry and AsMA: Several principles were agreed upon at the first meeting in Los Angeles in May 2009: - Issues for consideration must be directly relevant to the emerging commercial spaceflight industry. - The participation of the providers of future commercial spaceflight (the industry) is critical and demonstrated itself during this meeting. The industry participants now have a better idea of what the Working Group can offer them to facilitate the further development of commercial spaceflight especially in the area of risk evaluation and delineation of threats with possible suggestions on mitigation strategies. It was emphasized that the goal is not to generate suggestions that would be harmful to the industry, but to find out what the industry needs and how the Working Group can facilitate further development of commercial spaceflight by industry. The industry was also helpful in communicating what they specifically need and want. They were able to better detail to the Working Group what would be harmful and non-beneficial. It was also apparent that different corporations will have different needs and desire for help. - It was suggested that the Working Group would not focus on recommendations for standards or certification, but instead develop evidence-based, referenced evaluations and guidelines of the risks and ways to mitigate those risks to improve safety. Where there is insufficient evidence concerning a particular issue, then a recommendation will be made on what level of evidence is needed and how to obtain that evidence. A goal is to better articulate what are the gaps in the present knowledge of commercial spaceflight issues. - It was felt to be important to develop a process of determining risk assessment for participants (instead of standards or certification) with the goal of being able to provide informed consent to individuals prior to flight. This would be protective not only to the individual participant who would be better informed, but also to the industry which is also taking risk with each participant. - The issues to be discussed would include all aspects of commercial spaceflight, such as specific environmental threats (enclosed cabin environment, hyper G, hypo G, remote medical care). It would involve primarily crew issues, but would also address passenger safety. Mitigation strategies might include training issues as well as suggested countermeasures. The goal is to both identify and assess risk and then to suggest ways to mitigate risk. - There is difficulty in that the design reference missions for suborbital commercial spaceflight are different with different corporations and are still evolving. One deficiency in the recent Suborbital Commercial Spaceflight Pilot Medical Standards produced by AsMA was that there was no link between a specific design reference mission and the proposed standards. - It was decided that the next step was to focus on a single reference missions, Virgin Galactic, and to initially confine ourselves to crew issues in suborbital flight. We will develop guidelines concerning medical issues and training with the goal of identifying risks with risk mitigation. Guidelines will be evidenced-based and referenced. Knowledge gaps will be identified and articulated. Issues for Discussion Stresses of Suborbital Flight There are currently a number of companies throughout the world in varying stages of development of space vehicles to provide suborbital flights for tourists. The duration of the flight is expected to be 1.5 – 2.5 hours with 3 – 4 minutes in microgravity. Depending upon the type of space vehicle, there will be 1 or 2 pilots. Although most suborbital flights will be dedicated to space tourism, there will be some for other commercial purposes such as satellite insertion, reconnaissance, weather observation, research, etc. Because the companies are building space vehicles of different design, capability, and flight profile, the stresses will be somewhat different. Therefore, the recommendations for medical standards and for the medical examination must be flexible giving allowance for these differences. The stresses of suborbital flight include:
After liftoff, acceleration will be about 2.5 Gx although there could be some low level Gz forces as the space vehicle climbs to suborbital altitude. On reentry, 5.7 – 5.8 G’s will be imposed predominantly in the X-axis although some space vehicles are being designed to impose only 2.2 – 2.5 G’s in the X-axis. Because of tilt-back seating and the flight profile, most of the acceleration on launch and reentry will be in the Gx axis with a duration expected to be no longer than 30 seconds. The onset rate of the accelerative forces has not yet been defined. There are currently no plans to utilize anti-g-suits during these flights.
While the microgravity exposure will have a short duration, it is possible that non-adapted, sensitive individuals can experience symptoms associated with even short exposures to the space environment. The likelihood and severity of SAS/SMS symptoms on these missions, while undoubtedly less than what is observed in orbital spaceflight, still must be considered, especially when considering standards and minimal pilot complement requirements. SAS/SMS symptoms early in the course can include back pain, nasal congestion, headache, nausea, visual alterations and can progress to vomiting; however the full symptom constellation would be unusual with a short flight duration as anticipated.
Although the effects of microgravity are well known, this is not considered a significant factor in that exposure to microgravity will only be of 3 to 4 minutes in duration for each flight. However, there have been neurovestibular alterations observed in even short exposures to altered gravity environments in highly sensitive individuals. Of concern, is pilot performance after brief 0-G exposure and readaptation back to a hyper-G environment without the usual period of adaptation as in orbital flights.
There are differences in that some companies are planning a sea-level, mixed gas atmosphere while others are planning on a pure oxygen hypobaric environment allowing a maximum cabin altitude equivalent of 8,000 ft., similar to that of current commercial airline flight operations. There are currently no plans regarding the use of pressure suits, however pressure suit use for these flights, might be chosen as an additional safety/ risk mitigation approach for the cabin depressurization/ hypopressurization hazard.
For the most part, there is no concern regarding ionizing radiation because of the short duration of the flight and the fact that launch can be controlled depending upon atmospheric conditions. Also, this is considered an occupational health rather than a medical certification issue. However all flight crew should be required to wear personal dosimeters, as do radiation and medical imaging personnel, to ensure compliance with OSHA standards.
Non-ionizing radiation is not considered a significant factor for medical certification.
Some of the space vehicles do generate loud noise for brief periods although the exact decibel level is not known. Hearing standards congruent with current FAA class I pilots, seem reasoanable, although hearing protection requirements may need to be more robust for some of these vehicles.
The vibration associated with launch and aerodynamic loading of a space vehicle, is significantly greater than standard aircraft operations. Transient vibrational loads of >0.5 g peak for < 1 minute, and both immediate and cumulative vibration loads that can interfere with the ability of the pilot to track displays, maintain situational awareness of the vehicle and could possibly transiently interefere with the pilot’s ability to promptly institute corrective actions. However it is felt that vibration tolerance is not considered an specific standard required for medical certification.
The cabin will be sealed with recirculated air. Although there could be some concerns regarding off gassing, this is not considered a significant medical certification issue. Temperature and humidity factors should not be an issue. Additional Issues for Suborbital Commercial Spaceflight Training aerospace medical issues such as parabolic flight, physiological training, and centrifuge Orbital Commercial Spaceflight Pilot Medical Standards The goal is the development of a future position paper although it is currently felt that commercial orbital flights are still several years away in implementation. References 1. AsMA Task Force on Space Travel. Medical Guidelines for Space Passengers. Aviat Space Environ Med 72:948-950. 2001. 2. Antuñano, M. Hobe, S. Gerzer, R. (Editors). Position Paper on Medical Safety and Liability Issues for Short-Duration Commercial Orbital Space Flights produced by the International Academy of Astronautics. 2009. 3. AsMA Ad Hoc Committee. Medical Certification for Pilots of Commercial Suborbital Spaceflights. Aviat Space Environ Med 80: 824-826. 2009. |
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