6 ms·

The article says that since the thrust is always away from the Sun, it can't be used for inward journeys. But if I'm thinking correctly, this isn't necessarily

The article says that since the thrust is always away from the Sun, it can't be used for inward journeys. But if I'm thinking correctly, this isn't necessarily true. If you're in a circular orbit, and run this for a while (short compared to orbital period), then turn it off, I think you'll be in an elliptical orbit with perihelion lower than your initial orbit. If when you reach perihelion there happens to be a convenient planet with an atmosphere, you could aerobrake and either land or maybe continue in a circular orbit closer to the sun than your original orbit.

TeMPOraL 9y ago
Still reading up how it works, but if we could somehow bend the direction of the resulting force, ever so slightly, it would be enough to enable the spacecraft to thrust partially retrograde, which achieves lowering of the orbit.
hughes 9y ago
At the very least, thrusting radially away from the sun while moving towards it during an elliptical orbit would reduce the energy of the orbit.
mLuby 9y ago
Figure 5 demonstrates how an array of two or more plasma magnets can deflect solar wind to achieve the same maneuverability as a solar sail. Can't wait to see a cubesat demonstration vehicle blow past Mars!
clort 9y ago
Or perhaps, if you can only accelerate away from the sun, you just aim for a gravity well at aphelion and turn off as you approach, swing round it and float back towards where you want to go. You then turn the engine on to decelerate when you near your destination? (full disclosure: never played KSP)
- ethbro 9y ago
  I'd imagine this is the easiest solution for improving mission flexibility. If the only rules are "only accelerate away from the nearest star", that doesn't preclude using a planetary gravity field to also adjust your orbit. E.g. Making small course corrections in interstellar space (or simply mission planning exactly enough) so that you hit a planet's gravity well on insertion into the destination solar system, thereby slinging yourself into a more manageable eliptical orbit (and potentially burning something else at the right point to change your orbit) I'd also be really curious on how something like this works in the area of interaction between a planetary magnetosphere and the "sail" (e.g: https://en.m.wikipedia.org/wiki/Magnetosphere#/media/File%3AStructure_of_the_magnetosphere-en.svg https://en.m.wikipedia.org/wiki/Magnetosphere#/media/File%3A... ). Looks complicated!
  - QAPereo 9y ago
    The field generated by the drive is in the realm of 50 nanoteslas, and Earth’s geomagnetic field for example is in the microtesla range. I don’t think it really matters though, because the magnetic field around a planet redirects solar wind, and that alone would be enough to screw up this drive. In my opinion this is something you use for the interstellar leg of the journey, and you would avoid planets while the drive is on. That isn’t really a problem though, because other than a relatively short trip away from Earth, you’d be avoiding planets and building up momentum. To make this work, you’d be going at a hell of s clip relative to any other planets you’d come across, and you’d be a tiny mass to boot. You’d probably just sail on past, with a deviation in course, but not orbit or a 180. For any gravitational maneuver, you could rely on momentum and shut down the drive, restarting for the return leg.
dnautics 9y ago
Instead of aerobraking, you're probably better off doing a momentum transfer gravitational "negative" assist - transfer a chunk of your momentum back to the planet. I'm not an expert on plasma physics, but - couldn't do the solar equivalent of "tacking" - deform your magnetic field so that the solar wind flux in front is less than the flux behind, leading to a tangential acceleration, which could be used to achieve orbits that fall back into the sun?
- Cerium 9y ago
  I don't think that would work. Sailboats can sail into the wind similarly to how an airplane can have a glide ratio greater than one. The wind presses on the sail, and the boat transfers that to the water in such a way that it is easier for the boat to go forward than be pushed backwards. Of course it still slips back some, but it goes forward faster than it slips backwards.
  - dnautics 9y ago
    why wouldn't this work with a plasma field? If you inflate your leading edge to be larger, your net solar wind flux is going to be larger and a greater amount of force will be transferred to the craft from the leading edge, slowing you down. Even though you're being pushed OUT by the solar wind, your tangential velocity relative to the sun will be reduced, which, even if it results in a greater net orbital energy, will result in a more elliptical orbit (and thus a trajectory that sends you inwards).
  - foxylad 9y ago
    I agree. Tacking requires "levering" against a fulcrum (the the centerboard on a water yacht and the skates on an ice yacht. Imaging trying to tack on a frictionless surface - you'd simply get swept away from the wind.
    - hinkley 9y ago
      Anything we can get out of our gravity well will have an orbit around the sun. If it didn’t you wouldn’t bother with a high impulse/low thrust engine like this. Your momentum is what you’d be pushing against. Specifically, using a force vector with a substantial component (greater than 50%) in the opposite direction of travel. It would push you out but also slow you down. This kind of vectoring should be straightforward with a solar sail because it is flat. But if a magnetic field is perfectly spherical then there aren’t any angles. You’d have to make a fairly flat magnetic field to pull that off.

TeMPOraL 9y ago

Still reading up how it works, but if we could somehow bend the direction of the resulting force, ever so slightly, it would be enough to enable the spacecraft to thrust partially retrograde, which achieves lowering of the orbit.

hughes 9y ago

At the very least, thrusting radially away from the sun while moving towards it during an elliptical orbit would reduce the energy of the orbit.

mLuby 9y ago

Figure 5 demonstrates how an array of two or more plasma magnets can deflect solar wind to achieve the same maneuverability as a solar sail. Can't wait to see a cubesat demonstration vehicle blow past Mars!

clort 9y ago

Or perhaps, if you can only accelerate away from the sun, you just aim for a gravity well at aphelion and turn off as you approach, swing round it and float back towards where you want to go. You then turn the engine on to decelerate when you near your destination? (full disclosure: never played KSP)

ethbro 9y ago
I'd imagine this is the easiest solution for improving mission flexibility. If the only rules are "only accelerate away from the nearest star", that doesn't preclude using a planetary gravity field to also adjust your orbit. E.g. Making small course corrections in interstellar space (or simply mission planning exactly enough) so that you hit a planet's gravity well on insertion into the destination solar system, thereby slinging yourself into a more manageable eliptical orbit (and potentially burning something else at the right point to change your orbit) I'd also be really curious on how something like this works in the area of interaction between a planetary magnetosphere and the "sail" (e.g: https://en.m.wikipedia.org/wiki/Magnetosphere#/media/File%3AStructure_of_the_magnetosphere-en.svg https://en.m.wikipedia.org/wiki/Magnetosphere#/media/File%3A... ). Looks complicated!
- QAPereo 9y ago
  The field generated by the drive is in the realm of 50 nanoteslas, and Earth’s geomagnetic field for example is in the microtesla range. I don’t think it really matters though, because the magnetic field around a planet redirects solar wind, and that alone would be enough to screw up this drive. In my opinion this is something you use for the interstellar leg of the journey, and you would avoid planets while the drive is on. That isn’t really a problem though, because other than a relatively short trip away from Earth, you’d be avoiding planets and building up momentum. To make this work, you’d be going at a hell of s clip relative to any other planets you’d come across, and you’d be a tiny mass to boot. You’d probably just sail on past, with a deviation in course, but not orbit or a 180. For any gravitational maneuver, you could rely on momentum and shut down the drive, restarting for the return leg.

dnautics 9y ago

Instead of aerobraking, you're probably better off doing a momentum transfer gravitational "negative" assist - transfer a chunk of your momentum back to the planet. I'm not an expert on plasma physics, but - couldn't do the solar equivalent of "tacking" - deform your magnetic field so that the solar wind flux in front is less than the flux behind, leading to a tangential acceleration, which could be used to achieve orbits that fall back into the sun?

Cerium 9y ago
I don't think that would work. Sailboats can sail into the wind similarly to how an airplane can have a glide ratio greater than one. The wind presses on the sail, and the boat transfers that to the water in such a way that it is easier for the boat to go forward than be pushed backwards. Of course it still slips back some, but it goes forward faster than it slips backwards.
- dnautics 9y ago
  why wouldn't this work with a plasma field? If you inflate your leading edge to be larger, your net solar wind flux is going to be larger and a greater amount of force will be transferred to the craft from the leading edge, slowing you down. Even though you're being pushed OUT by the solar wind, your tangential velocity relative to the sun will be reduced, which, even if it results in a greater net orbital energy, will result in a more elliptical orbit (and thus a trajectory that sends you inwards).
- foxylad 9y ago
  I agree. Tacking requires "levering" against a fulcrum (the the centerboard on a water yacht and the skates on an ice yacht. Imaging trying to tack on a frictionless surface - you'd simply get swept away from the wind.
  - hinkley 9y ago
    Anything we can get out of our gravity well will have an orbit around the sun. If it didn’t you wouldn’t bother with a high impulse/low thrust engine like this. Your momentum is what you’d be pushing against. Specifically, using a force vector with a substantial component (greater than 50%) in the opposite direction of travel. It would push you out but also slow you down. This kind of vectoring should be straightforward with a solar sail because it is flat. But if a magnetic field is perfectly spherical then there aren’t any angles. You’d have to make a fairly flat magnetic field to pull that off.