141–150 of 150 posts
That being said, the project itself was a disaster and I'm glad to have escaped the class with a decent grade despite it.
My understanding of what's going on here is that the light sail isn't aiming or changing at all. It's just a big sail, in orbit. When it's moving away from the sun, the sail is being pushed "forward", which adds to it's velocity- this increases the apogee on the opposite side of the orbit. When it's moving towards the sun, the sail is being pushed "backwards", lowering it's current velocity and reducing the perigee.…
A minor note: the LightSail team says the perigee is lowering due to atmospheric drag not due to the sun slowing it down: > The perigee, or low point of its orbit, has dropped by a similar amount, which is consistent with pre-flight expectations for the effects of atmospheric drag on the spacecraft. That's not to say the solar pressure isn't potentially slowing it down too, but it sounds like the main driver is drag…
Earlier quoted context omitted.
Unlike Lightsail 1, Lightsail 2 operates at an altitude where the atmosphere is negligible.
It's not quite negligible at 700km. The effects of the atmosphere are also proportional to the craft's B* value (atmospheric drag coefficient), which is partially based on the surface area/mass ratio. Id imagine that a sail's effectiveness probably increases as its area increases and mass decreases so it should have have a relatively high B* compared to similar objects. Looking at the published TLE's seems to back th…
Earlier quoted context omitted.
A minor note: the LightSail team says the perigee is lowering due to atmospheric drag not due to the sun slowing it down: > The perigee, or low point of its orbit, has dropped by a similar amount, which is consistent with pre-flight expectations for the effects of atmospheric drag on the spacecraft. That's not to say the solar pressure isn't potentially slowing it down too, but it sounds like the main driver is drag…
I wonder if it'd be feasible to just have the sail be a one way mirror? Transparent on the "front".
If a photon hits the sail and is reflected, it must transfer two photon momentums to the sail. The energy should be less than before it the sail. Is it redshifted?
Yes, but by a tiny amount. This reddit comment [1] explains in better detail than I can. [1] https://www.reddit.com/r/askscience/comments/4anry6/does_lig...
We need more of this, and more spending and results in space research. Not only because we are destroying our own planet, but also because we as a species have been stagnating for quite some time.
What about https://en.wikipedia.org/wiki/IKAROS ? The only new part, is that Lightsail is a cubesat, right? (IKAROUS was 315 kg.) From article: "Our criteria was to demonstrate controlled solar sailing in a CubeSat by changing the spacecraft’s orbit using only the light pressure of the Sun, something that’s never been done before. I'm enormously proud of this team. It's been a long road and we did it."
Very cool! I know nothing about solar sails, but I wonder if the craft could have LEDs mounted to it so it could bombard different regions of the sail with photons to make it turn appropriately.
I'm curious if you could selectively turn off the reflective effect in different regions of the material and steer it that way.
Gloriously over-engineered.
Earlier quoted context omitted.
I wonder if it'd be feasible to just have the sail be a one way mirror? Transparent on the "front".
There are no known materials that act as a one way mirror. We don't expect to find any such material. With a one way mirror it would be easy to lower global entropy.
EDIT: this matters because full 180° reflection is like "bouncing" the photon to opposite velocity, can up to double exchanged momentum vs absorption. (This is why reflective mylar is nice)
Earlier quoted context omitted.
I have to admit, I got the idea from the beginning of the book Abaddon’s Gate . Solar sails might not be required but I think there’s a future in people plotting slingshot trajectories and sending packages around the solar system as fast and as cheap as possible. One day it will be manned missions, the space equivalent of people that fly hot air balloons around the world.
The novels of the James S. A. Corey authors are very inspiring given our recent space achievements. A highly recommended sci-fi series.