| Author |
Message |
    
Cavebear
cave painter
Username: Cavebear
Post Number: 2692
Registered: 9-2003
| | Posted on Saturday, June 24, 2006 - 4:25 am: |     |
I happened to see an idea for a solar flare detection satellite (to warn of serious incoming solar flares) that intrigued me. Such a satellite would have to be in solar orbit closer to the Sun than Earth, yet stay near Earth. The solution was a solar sail that would match the sun's gravity pull.
I thought it was an interesting idea, but they didn't explain how that would stay near Earth (maybe "Trojan Points"?) Any thoughts?
Machiavelli was pretty devious. For a guy... |
Thales
gatherer
Username: Thales
Post Number: 102
Registered: 9-2003
| | Posted on Saturday, June 24, 2006 - 1:28 pm: | |
I assume the spacecraft would have to be between Earth and Sun. Trojan points (Lagrange 4 and 5 points) probably don't work in this case, since they are on Earth's orbit, 60 degrees from Earth. Besides, you don't need a solar sail to stay there.
There are already spacecraft in or actually in orbit around Lagrange 1, between Earth and Sun, 1.5 million kilometers from Earth, but that is too close to Earth, if the idea is that a flare is detected when it passes the spacecraft - there would not be enough time for an early warning.
A spacecraft closer to Sun than Lagrange 1 would move too quickly on its orbit around Sun, but a solar sail could force it to an unnaturally slow speed, keeping it between Earth and Sun. Still, there are limits to what such a sail can do, and the spacecraft can't be *very* close to Sun, and I wonder if it would really be useful as an early warning system, especially considering that we already have reasonably good detection systems on Earth and in Earth orbit.
Heisenberg was here ... or over there ... well, maybe somwhere else ... |
Thales
gatherer
Username: Thales
Post Number: 103
Registered: 9-2003
| | Posted on Saturday, June 24, 2006 - 1:49 pm: | |
Thinking the effects in more detail, simply slowing the spacecraft down would not work. Perhaps the idea was to use a solar sail to keep the spacecraft on orbit around Lagrange 1? Either you need a sail or engines. While Lagrange 1 (as well as 2 and 3) is nearly stable (unlike 4 and 5 which are stable), a spacecraft will slowly drift away without orbit corrections, and since engines need fuel, a sail might last longer. But then the idea must be that a flare is detected before it reaches the spacecraft, and this offers little advantage over a satellite on Earth's orbit.
Heisenberg was here ... or over there ... well, maybe somwhere else ... |
Cavebear
cave painter
Username: Cavebear
Post Number: 2697
Registered: 9-2003
| | Posted on Saturday, June 24, 2006 - 4:50 pm: | |
"Lagrange" was the term I was trying to recall... Couldn't bring it to mind at all.  So thanks for that help. I think they did mention 1.5 million km. 
The idea was to allow enough warning to adjust major Earth-bound electrical power grids to compensate for surges, get any astronauts to the best-shielded areas, and turn off certain satellite functions.
Solar flares travel quickly, but it seems the radio transmission speed advantage is enough to prevent some serious problems. BTW, the solar flare warning satellite was about the size of a football (American or European)and encased in a cube frame just a bit larger. That was all the size they could use to match the solar sail they could pack into a mission.
Machiavelli was pretty devious. For a guy... |
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