Radiation exposure during suborbital commercial spaceflight

We are all constantly exposed to radiation, in a variety of forms and to varying degrees. The crew and passengers of suborbital commercial space flight will experience enhanced exposure to cosmic radiation as they reach altitudes up to 100 km above the Earth. However, because of the short duration of suborbital missions, they will likely get a lower dose than the crew and passengers of long duration commercial air flights. Nonetheless, it will be prudent to require the providers of commercial suborbital missions to provide passengers with a detailed briefing of the effects of radiation and the anticipated exposure the crew and passengers will accumulate from their mission(s). In addition, the providers should have the tools and expertise to predict and subsequently to monitor the exposure.

The radiation model used was the QinetiQ Atmospheric Radiation Model (QARM). It is a comprehensive atmospheric radiation model constructed using Monte Carlo simulations of particle transport through the atmosphere. It uses atmospheric response matrices containing the response of the atmosphere to incident particles on the upper atmosphere. It was run through the internet-accessible interface at: http://geoshaft.space.qinetiq.com/qarm/index.jsp?URL=start.jsp

This model is optimized for calculation of the radiation environment at aircraft altitudes, and has been validated up to 40 km. An alternative model considered was the CREME96 model, but it provides orbit-average doses, not point doses, and it is optimized for orbital altitudes. Since less than five minutes on each trajectories is above 40 km, it was decided that QARM would provide a good initial representation of the exposure. It is important to note that QARM does not include vehicle shielding in its calculations.

Solar storm exposure can be orders of magnitude greater than experienced during quiet geomagnetic and solar conditions. QARM was used to estimate the impact of a solar storm on suborbital missions at high latitude. To do this, the dose equivalent versus altitude was generated for two representative storms, one from 29 September 1989 and one from 24 October 1989. The September storm represents a severe storm. The October 89 storm was also large, but did not have the impact of the September 89 storm. It is important to note that these cases were used because they were readily available with the internet accessible interface to QARM. It would be highly advisable to do similar analysis for other storms, particularly the August 1972 storm and the January 2007 storm, which had a very rapid increase in flux from event onset. It would also be important to model the impact with other radiation transport codes and with vehicle shielding.159891 modified by 155.2.0.50 on 8-10-2009-->