8. NASA's career equivalent doseages for astronauyts is computes as follows:
200 + 7.5 ( age - 30) rems ( males up to 400 maximum rems)
200 + 7.5( age - 38) rems (females up to 400 maximum rems)

Using these formulas, answer the following questions:

How many trips to Mars could a 40 year old man take before reaching the maximum amount of career radiation exposure recommended by NASA?
Total recommended dose = 200 + 7.5(40-30) = 275.0 rems
Mars trip dose = 117.0 rems so the number of trips is 2

How many trips to Mars could a 40 year old woman take before reaching the maximum amount of career radiation exposure recommended by NASA?
Total recommended dose = 200 + 7.5(40-33) = 215.0 rems
Total trips = 215/117 = 1.8 This could either be stated as 1 or 2 trips.

Name some ways that the amount of radiation you received on this trip could vary.
Higher SPE exposure; more solar storms; defective shielding; less solar activity; better shielding. These are all possible answers.

Which of the two sources of radiation, cosmic rays and SPES., are the most hazardous and how would you try to minimize its risk to the crew?
SPEs are unpredictable and can deliver significant doses, especially if an astronaut is 'spacewalking' during which time little shielding is available. Some type of early warning system is required to anticipate when these storms may be starting on the solar surface. Either constant telescopic monitoring is needed, or some other method to sense the buildup of SPE conditions.

Based on what you have learned, what are some things you could do to minimize the amount of radiation that you would receive on a trip to Mars?
Stay in the spacecraft. Staying on Mars less than 2 years is not an option because you can only return when Mars and Earth are closest to each other every 2.1 years. It is not the stay on Mars that hurts you, it is the changing cosmic my conditions during solar maximum and solar minimum. One possibility is to start and end your trip during the time that the sun is near its maximum in the solar cycle. This would reduce your non-SPE cumulative dose, which is the factor that dominates the total dosage. Start the trip 2 years before solar maximum, and end it 2 years after solar maximum would be a better strategy, provided you can reduce your risk for SPE events.