LightSail Test Mission Declared Success; First Image Complete
planetary.org
planetary.org
"for me it's [lightsail is] really personal. i had carl sagan for one class, and it changed my life. and so i'm really excited to get this thing working. if not this mission, the next mission. oh god, the concept is just cool, to just be sailing around the solar system essentially for free. It's elegant."
"there are two questions we all ask, and if you meet somebody who claims they've never asked these questions they're lying and that's all there is to it: where did we come from and are we alone in the universe? if you want to answer those questions, you have to look at the past and the future. You have to look at paleontological evidence, and you have to explore space."
"talk to younger people. they expect great things from technology. that expectation i believe will carry over to every aspect of life - that we can do technological things to prevent climate change. that for any problem there's a technological solution."
"this is what we talk about all the time in science ed. we want science every day in every grade. this is obvious to me and my colleagues in science ed. what's amazing is it's not amazing to everybody. science is as important a topic as writing and reading and arithmetic. if you want to have innovation, if you want to have the engineers of tomorrow, you have to have science."
"kids have no trouble understanding climate change - it's grown-ups that are confused. climate change denial is almost entirely a generational issue."
[1] http://www.nbcnews.com/science/science-news/bill-nye-boosts-...
I do wonder if this is a US thing. I've not seen a denier over here in the UK. Sure, on the TV they have debates about climate change with scientists. They argue and present data and talk about change. They may argue about the rate of change and the potential effects. But everyone agrees that change is happening.
Just take a look at the G7 fossil fuel pledge by the Germans. That's pressure from everyday people over here in Europe, that's millions of us who understand.
It seems it mostly depends on interests.
Global warming wouldn't really be bad for Poland, and CO2 tax is very bad for Polish economy, so there's more people choosing to belive it's all a scam.
Oddly, in the back of many people's head that I've spoken with is the Cambrian period. They have a vague remembrance that Earth was hotter and more swap like. Since there were no men then, it is possible for the planet to heat up on its own. They latch onto this thought and back their view that modern peoples can't be causing this much damage.
The article doesn't seem to mention it, just the details of this successful mission.
Solar sails mostly capture the momentum of sunlight, not the solar wind.
(Solar wind is the plasma of electrons, protons (hydrogen nuclei), and alpha particles (helium nuclei) that come off the sun.)
edit: as others point out, this isn't quite the first time. but it is the first time in a long time!
So this doesn't validate the theory, correct? (Is it actually validated yet?)
Is this a viable method for long-distance traveling? Is it limited in direction (like the photons only push one way, and it's not like you can use a rudder in space, right?)
Yes, it's viable. http://en.wikipedia.org/wiki/Solar_sail
not very general-purpose, but sound in principal.
Orbital mechanics is fun :).
If you are at rest 1 au from the sun, and you deploy your sail perpendicular to sunlight, which direction will you accelerate in?
Of course, no spacecraft will ever be at rest with regards to the Sun -- it would take 30km/s of delta-v to get there, and there's rather little point. They will be orbiting, starting from leo, which means that the meagre acceleration from a sail is more than enough to get basically anywhere.
If you angle the sail to send light in front of you, you will speed up and fall towards the Sun. If you angle the sail to send light behind you, you will slow down and move away from the Sun. Aim to either side and you will move away from the light and also move up slightly. Between these effects you can manage to get from any orbit you might be in to any other possible orbit. It will just take a while.
This is all assuming that there is not enough force from reflecting the light back into the Sun to beat the Sun's gravity.
Don't you mean slow down and fall towards the sun?
If the reference frame is initially rotating at with your orbit or a closer one, "speed up" is accurate. If it's rotating with some more distant orbit, "slow down" is accurate.
This, by the way, is one reason why physicists tend to just say "accelerate" in both cases: then, it's technically true for any external reference frame.
If you have 2 objects in the same orbit and one accelerates backwards, that one winds up below and in front of the first. This happens because accelerating backwards causes it to lose energy, so it falls, and in falling picks up more kinetic energy than it had before.
Please consider implementing gravity for the planet and perhaps a time scale option.
There's gravity from the sun but not the planet, and yes, that ought to be worth adding. I'm not sure what'd help the most to turn this into a fun game, though, so I'm working on other things. Thanks for the suggestion; a time control's probably a good idea too.
Some important limitations to keep in mind with solar sails are that the momentum imparted on them tails off according to an inverse square law, and also that since they have no medium like water to push against (hence no rudder), you can't "tack into the wind" like a sailboat can. However, and this is a very important point, because of the way orbital mechanics works out, and assuming you can adjust your orientation of the sail on the fly, this matters less than you might think, e.g. imagine orienting your sail at apoapsis so that you create a net thrust in the retrograde direction, then you furl or orientate your sail edge-on to the Sun. You end up with an orbit that has a periapsis closer to the Sun (with an apoapsis further out), so you're still traveling inward in some sense, at least for part of your orbit.
http://www.isas.jaxa.jp/e/enterp/missions/ikaros/index.shtml
IKAROS, launched by JAXA in 2010, passed Venus six months later in is still accelerating (slowly; it's getting about 1mN of thrust). It's even steerable, by using LCD panels in the sails to change the albedo. It was last contacted early this year. IKAROS' sail is 20m diagonal, which makes it considerably larger than LightSail1.
There are even pictures of it --- it ejected a camera after deployment.
Long story short, photons (and solar wind) impart a small amount of momentum on the sail. This can be used instead of rockets - as long as you don't mind it taking an absurd amount of time to get you anywhere, that is. And its a whole lot lighter.
Historically, both thrust and delta-V have been sorely constrained on spacecraft. This is trading a lot of thrust for an infinite* amount of dV, which is a really valuable trade.
(*Practically infinite. It runs out when the sun stops giving solar pressure ;) ).
I'm just saying they aren't the be-all and end-all. There are many things where they aren't particularly useful (for instance: anything time-constrained. Or anything that requires largeish maneuvers to be done in the outer solar system. And there are certain maneuvers that are... difficult... with a solar sail.)
Also, it's not infinite, nowhere near. Among other things, solar radiation and solar wind will degrade the sail over time. Especially with a lot of the materials they suggest using (mylar, etc.)
It is not meant to carry men to Mars.
There's enough atmosphere in LEO that I am surprised that it's a net positive, frankly. I mean: the ISS requires a reboost every few months.
But the grandparent comment said "It's mainly targeted at cube sats".
And cubesats tend to be LEO-based. (They tend to be the cheapest thing possible - and its harder to get into a higher orbit. And they tend to be launched parasitically to boot.)
Hence, talking about LEO.
Also, that you are restricted in how you can maneuver - you cannot just burn in any old random direction at any time.
Nevertheless, it made me happy to read it, and I welcome it :-)
(One could note the pleasing irony of the comment itself being an instance of the type of communication-by-reference-to-shared-myth that occurs in the episode. However, since its contribution to this conversation is not about that mode of communication, it's ultimately a distraction .)
[1] http://www.theatlantic.com/entertainment/archive/2014/06/sta...
The river Temarc in winter. Kiteo, his eyes closed.
;).
Honestly, this "familiar pop culture touchpoint" inspired a big part of a generation of scientists and engineers. As someone who thinks it has a significant impact on his life, I too appreciated the comment :).
> Picard, his head in hand. [1]
> [1] http://i.imgur.com/iWKad22.jpg
(Also, a second example of the communication-by-shared-myth idea, made more interesting by the evolution of what the images usage in culture.)
https://soundcloud.com/startalk/cosmic-queries-lightsail-wit...