3 ms·

While the solar wind gets stronger closer to the sun, it's an r-square law that balances the r-squared force of gravity. Fun fact: If a solar sail could be in a

by dalke 12y ago

While the solar wind gets stronger closer to the sun, it's an r-square law that balances the r-squared force of gravity. Fun fact: If a solar sail could be in a fixed position at Mercury orbit then it could also be in fixed position a Neptune orbit. Quoting from http://en.wikipedia.org/wiki/Solar_sail http://en.wikipedia.org/wiki/Solar_sail, the "total force exerted on an 800 by 800 meter solar sail, for example, is about 5 newtons (1.1 lbf) at Earth's distance from the Sun". The Orion space capsule is ~25 sq meters. I'll round that up to 100 sq meters (I'm being generous), giving a breaking force of 5/64 N on the waste barge. The capsule mass is 20 tons. Assuming the waste barge were the same mass (I'm being generous) gives a solar gravitational force in Earth orbit of 120 newtons. This far exceeds the push from solar wind, even with wildly optimistic numbers. (Note: there's some 50,000 tons of high-level nuclear waste in the US.) So no, you couldn't lose a lot of velocity just braking against the solar wind. Not unless you've also developed effective solar sail technology.

exDM69 12y ago
Your calculations seem sensible, but you're only talking about radial forces, ie. countering the "downward" force of gravity with "upward" thrust of a solar sail. But space flight maneuvers typically use tangential or almost tangential thrust. Slowing down or accelerating the orbital motion will cause the altitude to vary, preserving the orbital energy and angular momentum. Placing a solar sail in a 45 degree angle from the sun will change the orbit slowly but surely, as there will be a little tangential and radial thrust. I still don't think it's viable for throwing anything into the sun, though.
- lmm 12y ago
  I think it's viable. There are no other forces acting on you. Set up the solar sail at 45 degrees "against" your orbit. You will slowly but inevitably spiral into the sun without burning any fuel.
  - dalke 12y ago
    If you have effective solar sail technology then all my calculations are thrown out the window. If you don't, then the time to spiral into the sun is large. Figuring 5/64 N on 20 tons and an orbital velocity of 30km/s gives t = v / a = 30 km/s / ((5/64) N / 20000 kg) = 245 years to cut the orbital velocity This assumes all of the force could be used to slow the waste hauler. As http://en.wikipedia.org/wiki/Solar_sail http://en.wikipedia.org/wiki/Solar_sail points out, the force is cos^2(theta) so the actual time at 45 degrees is t = 245 * (sqrt(2)/2)^2 = 490 years. The actual time will be smaller because you only need to hit the sun, and solar wind will get stronger. So, 350 years? As a wild-ass guess. That same page points out that sails don't work much inside of 0.25 AU, because the temperature can exceed the material properties of the sail. Though I think if the apogee is inside of 0.20 AU it's good enough. To make it worse, the solar wind fluctuates, so unless there's active control on the rocket, its orbit will be unpredictable over the centuries. When it's still near Earth orbit, or when it approaches Venus orbit, what are the chances of a gravitational assist leading to an Earth-return? With 50,000 tons of high-level waste, and 15 tons per rocket => 3,333 rockets in uncertain orbits, the chances become much higher.

by dalke 12y ago

exDM69 12y ago

Your calculations seem sensible, but you're only talking about radial forces, ie. countering the "downward" force of gravity with "upward" thrust of a solar sail. But space flight maneuvers typically use tangential or almost tangential thrust. Slowing down or accelerating the orbital motion will cause the altitude to vary, preserving the orbital energy and angular momentum. Placing a solar sail in a 45 degree angle from the sun will change the orbit slowly but surely, as there will be a little tangential and radial thrust. I still don't think it's viable for throwing anything into the sun, though.

lmm 12y ago
I think it's viable. There are no other forces acting on you. Set up the solar sail at 45 degrees "against" your orbit. You will slowly but inevitably spiral into the sun without burning any fuel.
- dalke 12y ago
  If you have effective solar sail technology then all my calculations are thrown out the window. If you don't, then the time to spiral into the sun is large. Figuring 5/64 N on 20 tons and an orbital velocity of 30km/s gives t = v / a = 30 km/s / ((5/64) N / 20000 kg) = 245 years to cut the orbital velocity This assumes all of the force could be used to slow the waste hauler. As http://en.wikipedia.org/wiki/Solar_sail http://en.wikipedia.org/wiki/Solar_sail points out, the force is cos^2(theta) so the actual time at 45 degrees is t = 245 * (sqrt(2)/2)^2 = 490 years. The actual time will be smaller because you only need to hit the sun, and solar wind will get stronger. So, 350 years? As a wild-ass guess. That same page points out that sails don't work much inside of 0.25 AU, because the temperature can exceed the material properties of the sail. Though I think if the apogee is inside of 0.20 AU it's good enough. To make it worse, the solar wind fluctuates, so unless there's active control on the rocket, its orbit will be unpredictable over the centuries. When it's still near Earth orbit, or when it approaches Venus orbit, what are the chances of a gravitational assist leading to an Earth-return? With 50,000 tons of high-level waste, and 15 tons per rocket => 3,333 rockets in uncertain orbits, the chances become much higher.