Quote:
Originally Posted by Steve McDonald
I have read that it would take about 15 feet of lead on all sides, to provide an effective, passive shield from cosmic and solar rays. There is a possibility of an active, magnetic shield being developed for spacecraft, but if it ever failed, even for a short time, the occupants would be snuffed-out. It would take a lot (two separate words) of energy to power it and that would be a scarce resource in space, unless the sun was close enough to generate solar energy. Once astronauts arrived at a destination, a shield would have to exist for everywhere living things would go. It's hard enough to scratch out a living here on the friendly surface of earth and the handicaps in space would not permit it. Spaceship Earth is likely the only home we will know in our mortal lives.
|
A 3 Tesla magnet uses 96kW (that's about the biggest MRI machine ever), the kind you can't use on people with ferrous dental implants, or orthopedic pins. That's pretty much all you need to cover a wide enough area to provide a safe zone. Probably significantly less if you build toroids around a cylindrical hull, the safe zone being inside those toroids. Think of it like a magnetic Faraday cage, keeping protons away. Further low energy protons aren't an issue (they're known as hydrogen) and high energy protons experience magnetic forces proportional to their velocity (Lorentz Force), thus the higher the velocity proportionally the less field you'd need to deflect it.
The insolence extra-atmosphere is 1365 W/m^2. To put that into perspective, at noon on the equinox at the equator the insolence is 1000 W/m^2. So say a 1.5 square meter solar panel that has peak generating of 300W will generate 450W out of atmosphere, maybe significantly more if the rating is typical peak output, not maximum peak output..
The Apollo capsule was basically a 12 x 32 cylinder, covering that with 300W polycrystal PV panels (low efficiency) would generate 100kW (it actually generates 200kW, but only half can receive sunlight at any time). However that capsule was designed to maintain 3 men for up to 10 days. Using a Hohmann orbital path (lowest energy path) the trip to mars would take 9 months there, 500 days on Mars, 9 months return. So the vehicle would need to be significantly larger than 12x32 therefore more area for panels, also monocrystal panels are more efficient increasing energy harvesting per square meter.
It's a simple engineering problem.
Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
