Slashdot Mirror
Solar Sail Fails Again
LtFiend writes: "It seems that they've failed at sending up the solar sail prototype again. This time the unit crashed to earth after the final separation of the rocket didn't execute. What a shame. I really hope this project can get back on track quickly."
Well, the problem is they didn't fail in the new part (the solar sail). The failed in what should be a routine part of the expedition (detaching from the launch rocket). So, in that sense, it was quite the failure.
It would be like developing a new car engine and then driving it off a cliff. There's a difference between meaningful and meaningless failures.
Photons can quite easily propel a solar sail, since they do carry momentum. I don't know which would provide more thrust though, photons or the solar wind.
"It seems to me it wouldn't matter what color, etc., the reverse side was, you'd still get a pressure front pushing you away." The sail could always be folded in again. It also would be possible (using segmented sails as in the illustration from the article) to rotate the sail surface so that it is tangent to the photons/protons being emitted from the other sun and thus avoid its pressure almost completely (if that's what's desired. Probably the pressure from another sun would be used to assist in deceleration) BTW: "KE=mv^2" isn't really the equation. "KE=(1/2)mv^2" is the (non-relatavistic) equation for kinetic energy, and is only partially related to momentum. The real momentum equation is just "p=mv".
And, by briefcase nukes, I don't literally mean a conventional briefcase-sized nukes, but something a bit bigger and still managable by one person--like the ones Russia has 'misplaced'.
I think it would spin to generate rotational momentum - harder to push off course once it gets going.
Don Negro
Don Negro
Perl 6 will give you the big knob. -- Larry Wall
The idea of using geosynchronous satellites has been around at least since Clarke back around WWII, but if there had never been the government funded Soviet and U.S. space programs, do you really think that the companies who make money uplinking to and downlinking from those satellites would have financed and developed a way to get them into orbit all by themselves as quickly as it happened with all that previous government funded work to piggyback on?
Institutions whose function is to earn a return on investment will usually spend a lot more on applied science research than "pure" science research.
I see even classic Slashdot is now pretty much unusable on dial up anymore.
Agreed. It would be interesting to know what can be learned from this particular failure, since it was a failure of the rocket, not of the sail.
After 50 years of messing around with rockets, you'd think we'd know how to build them to be cheap and reliable. That we're still struggling with this means that it's probably a very difficult problem.
Makes me wonder what the actual launch success rate of modern rockets is...
--
Use 'slashdot stuff' in the subject line in any email you send me if you want to get past the spam filter.
When you arrive at the destination star with the strong solar wind, you have a lot of speed built up from when you left the source star. The source star will be far away, so its wind will be negligible. Therefore you just fold your sails, and suddenly the wind from the destination star will not affect you all that much. Just unfold them a little if you need to brake.
Finally! A year of moderation! Ready for 2019?
Yes, if it's not going to work, and it *can't* work. It simply can't defend against the most likely nuclear attack by a terrorist group or "rogue nation" - a smuggled weapon. Not to mention the many possibilities for countermeasures that can never be properly tested agsinst.
It's possible, but unlikely. As I understand it, the research involves building expendable rockets that are precisely guided by computers and radar. None of those seem particularly promising areas for civilian application. In any case, aren't most of of the interesting technologies are likely to be classified and take many years to reach civilian applications?
Research projects are cool. The US would be wise to spend even more on them. There are plenty, however, that are more pressing and more interesting than trying to shoot down ICBMs. Fusion power, fuel cells, technologies related orbiting solar power stations, AIDS vaccines, malaria vaccines, and so on, are more likely to produce things that contribute positively to peace and security for US citizens than a multi-billion-dollar boondoggle that won't work and is pissing off both your allies and the two countries that actually *do* have the ability to turn America's cities into smouldering ruins, missile shield or no missile shield.
Go you big red fire engine!
Any sufficiently advanced technology is indistinguishable from a rigged demo
--Andy Finkel (J. Klass?)
I can cope with comments asking people to check the links before they post, but asking them to go read a physics book before posting? The question was well thought out and well-worded. It was a reasonable question, and it had a reasonable answer.
Geek != Physics Geek
~ Leilah
Or maybe think a little more before posting.
Oh BTW polarisation and momentum are quite different things
The solar sail did not fail, the system for getting it to orbit did. The title should read "Conventional Rocketry Fails Again".
--
But then again, I could be wrong.
Read The Curve of Binding Energy The author was one of the leading nuclear weapons designers durring the cold war. He designed a tactical nuclear weapon that weighed under 50lbs. He also claims that the minimum critical mass of PU printed in your physics book is much larger than the real, classified value (highly dependant on how you shape the fissionables/charges).
Sorry, author is not the subject of the book, been a while since I've read it.
It's a fair bit less than 35 kg, and do you think 35kg of plutonium takes up much space?
--Gfunk
Send lawyers, guns, and money!
Life for those remaining 5000 might seem to suck to you, but I'd rather let them decide. After all, if the planet is gone what does it matter how much we spent on a shield that didn't work?
I'd argue against an ABM shield being destabilizing in the way that you think. What if it starts a competition to see who can build the most effective missile shield? I'd rather see multiple contries frutilessly expending efforts in ABM research than in productive weapons research.
Besides, if an ABM shiled truly cannot work then how can it bring any instability? Either aargue that it will be effective and thus make everyone distrust us, or it will not work and everyone will just laugh at us. You can't have it both ways.
"There is more worth loving than we have strength to love." - Brian Jay Stanley
Of course it can't work against a likley terrorist attack scenario, but I think that's beside the point as that's not the problem it's trying to solve. I imagine they have other programs in place to help combat threats like that (and it seems like a lot easier problem to solve).
As I said in my other reply I'd rather see countries fruitlessly expending efforts racing to build missile shields than missiles. The way I figure it, you can have one or the other - saying you can divert all funds from programs like this to other more peacefuul research is a nice idea but simply not practical due to huamn nature. If the money were not being spent here, it would be spent on exotic weapons research or something along those lines.
Personally, I don't see that other contries would get pissed off enough to actually fire nukes at us. And there are plenty of other things they are more pissed about already.
As for side benefits, it might take a while for something to trickle down to us but you never know. What about advanced collision detection in cars (or better yet, airplanes), or more advanced missile defense systems for combat ships? How about super advanced insect killing machines that can dispatch mosquitos at a distance of ten feet with carefully controlled jets of water? Or for a more practical angle, electronics that can resist heavy G's or much better rocket engines. I have no idea, but look forward to the results. Besides, it seems like an interesting problem to solve.
"There is more worth loving than we have strength to love." - Brian Jay Stanley
Forgetting the numbers dead for a moment, lets say 8 nukes get through - that's eight cities gone (possibly less depending on how many were trying for a single target). I'll avoid the argument that some small terrorist group would send up just a few nukes as I agree with others that would be pretty stupid for anyone to try.
But take the other side of that argument, what if the ABM stopped the single nuke that was targeting some out of the way place (like somewhere in Montana or Wyoming). Would you say it's a waste of time to try and protect at least some people? Perhaps you just want to be offed in the first round of an exchange, but there might be a few people who would actually want to live. Rather cold of you just to kill them all with numbers. Would you really rather kill everyone in the US than leave 5000 people alive?
One last side argument - from space research, we get unrelated spinoff technologies that help us in our everyday lives (like frozen ice-cream). Might there not be some side benefits from ABM research as well? Or are you also for shutting down NASA and all space research.
I myself am not sure how effective such a system would be, but in general I'm all for research projects. I don't understand why people feel it to be such a waste of money when it could lead to other interesting results and possbily to a useful missile shield. I agree with the orignal poster that people shouting about ABM test failures look to me like the same sort of people that laughed at the Wright Brothers and held up every failed test as absolute proof of the impossibility to succeed.
"There is more worth loving than we have strength to love." - Brian Jay Stanley
Using energy from the star which you're approaching is no problem. Your approach will take decades, so you turn the sail to drag your speed down during that time -- and the closer you get, the stronger the deceleration.
And if "simple thrusters" could reach the expected high speeds, they would be used during launch as well. The advantage of a solar sail ship is that it does not have to include the mass of rocket fuel for deceleration, fuel for accelerating that fuel, fuel for accelerating the fuel for deceleration, fuel for accelerating that fuel...
I think that it's not just whether individual trials work but the combination of political destabilisation (We've got nukes and you can't hit us can sound fairly threatening if you are on the wrong end of it) and economic flaws. Even if you can solve the problem as it stands, the economic model is unhelpful. The cost of doubling the number of targets for the system is much cheaper than adjusting the system to compensate.
Funny. Russia has way more reliable rockets over all. The number of failures to launches is greater for NASA and the ESA than it is for Russia. You have a serious NIH syndrome. suggest looking into it or maybe checking facts before actually saying that NASA builds more reliable rockets.
How much government funding did Edison receive?
what happens if we need to approach a star that has a higher strength solar wind than the one propelling the craft? It seems to me it wouldn't matter what color, etc., the reverse side was, you'd still get a pressure front pushing you away
That's actually exactly what you WANT if you're trying to approach another star.
These things depend on acceleration, not velocity. That is, they don't move very fast at all at first, but each new photon bumps the speed up a little. By the time this craft is halfway between two stars, it's moving at a respectable clip.
Now, as the craft is closer to the target sunthan it is to the source sun, it might be time to put on the "brakes" as it were. How would you do that with a rocket? Turn around and THRUST back toward home. How do you do it with a sail? Turn around and let the target sun push against you. If the target sun is larger, you just fold the wings in a little bit to regulate the effectiveness of the thrust.
When the craft is slowed to a safe approach speed, fold the wings to reduce their effectiveness. Let the sun's gravity pull the craft in more, and regulate the speed with the wings so you don't just get sucked all the way in.
Now it's time to start taking pictures or finding something to orbit safely.
[
... and saw the blueprints back in the 80s. These things can be built small. I'd like to say I could tell you more but then I'd have to kill you, but the fact is, I'm gettin' old and I've just plain forgotten most of it...
The invisible hand of the Alpha Centaurians is trying to tell you something!
rights are only "taken away" from people who do not know how to demand them (and I don't use "demand" in a "protester in front of the capital building with a sign" sorta way, but rather knowing how to respond when some terrorist burreacrat shows up making demands of you). "the feds" are like the wizard of oz - big and scarry until toto draws back the curtain.
---
Learn the rules so you know how to break them properly.
www.teslabox.com
If you "bend and stretch [the rules] to your will", you are certainly breaking the intent of the rule. So in canada, you're breaking the legislature's intent to steal 30% or 40% or 80% (whatever the rate may be) of your "income", but having learned the rules, you've "done it properly."
The Dalai Lama's Instructions for Life
- Respect for self.
- Respect for others.
- Responsibility for all of your actions.
---
Learn the rules so you know how to break them properly.
www.teslabox.com
Cost of Solar Sails - $4,000,000;
Cost of clean up mission - $never revealed;
Trusting Russian Space Technology - WTF?
The Planetary Society Page
More info on Solar Sails
I think the more precise way to say it is, the upper stage of the rocket did not separate correctly. From what I'm reading, this is a launch vehicle failure, not a solar sail failure. Launch vehicles fail from time to time. The public should not read this news item and say "Solar sails don't work."
Travis
Well - forget about other stars for a moment. The same problem occurs when you want to travel sunwards in our own solar system. Can you use a sail to do that?
Yes you can. Solar sails can provide lateral thrust. This enables you to do swingby maneuvers and decelerate.
Personally I think that magnetic sails are far more promising than mechanical ones.
Recent research shows that a small amount of plasma can extend a magnetic field tremendously.
This was a project funded by a private entity, the Planetary Society, NOT by NASA or any other agency of the U.S. governement.
However, I WOULD like to point out that the first two or three attempts by the US to launch an artificial earth satellite were failures too, not to mention Apollo 13 and Challenger.
Space exploration is dangerous, and it really DOES take rocket science to get there.
Do not meddle in the affairs of sysadmins,
utter rubbish
How much government funding did Edison receive?
... zero. Find something else to troll with.
About the same amount the Planetary Society did
Do not meddle in the affairs of sysadmins,
utter rubbish
Could it be becuse a defense against ICBM has to work perfectly the first time it's ever used?
... say ... 99.9% effective, you're still taking about 8 nukes getting to their targets, with an approximate yield of (take the US value) 100 kt each, on average. Using Hiroshima as the best model that comes to mind, "Fat Boy", at less than 30 kt killed 350,000 people.
If the ABM system was
Do not meddle in the affairs of sysadmins,
utter rubbish
This comment was both thoughtful and thought-provoking ... mod it up!
Do not meddle in the affairs of sysadmins,
utter rubbish
ONE nuke is enough to wipe the US off the map
... in fact, it's likely that a single nuke powerful enough to wipe out the US would probably be enough to shatter the planet.
... IIRC, it requires 35 kg of fissionables just to get supercritical. The only credible radiological threat that a briefcase could transport is an area denial attack, where you would mix explosives and radioactive material to contaminate an area.
Better be one HELL of a nuke then
and its FAR easier to transport it in a briefcase anyway.
Briefcase nukes are an urban legend on a par with alligators in the sewers of New York. Nukes are HEAVY
Do not meddle in the affairs of sysadmins,
utter rubbish
little info about planetary society :)
"The Planetary Society was founded in 1980 by Carl Sagan, Bruce Murray, and Louis Friedman to encourage the exploration of our solar system and the search for extraterrestrial life.
The Society is a nonprofit, nongovernmental organization, funded by dues and donations from individuals around the world. With more than 100,000 members from over 140 countries, we are the largest space interest group on Earth. Membership is open to all people interested in our mission."
so go to their site and apply for a membership. it costs only 40$ (30$ for students) for us in europe. its even cheaper for north americans. most of the money goes to various space related projects. as a member you will also recieve their magazine planetary report which is really educational and entertaining to read.
-- http://electronicintifada.net --
The project was launched on a converted Russian ICBM. The fact that the rocket failed is SOME good news at least - maybe all those nukes would just fall into the arctic instead of turning North America into the world's second largest (second after Eurasia, of course, in such a scenario) glass bowl. ;P
Derek
They did build a shuttle, but fundings to use it didn't follow up.
I think that shuttle is now somewhere posing as an attraction.
Idealy the star your approaching is your destination, so you turn the craft around and use its energy to slow you down.
The Kruger Dunning explains most post on
New technology.
failing.
because of old technology that we used to have working 30 years ago but can no longer manage.
Need help treating your acne? Come here!
So then if photons have energy (obvious), then they have mass.
And it is well demonstrated that reflecting a photon tranfers momentum. Convert electron volts to grams in your equations and it'll all work out :)
As I understood it, the launch was a sub-orbital parabola, to test the deployment of the sails. So it was going to crash back to earth by design, the failure is in that the sails did not separate and deploy correctly.
"Open the pod by doors, Hal" > "I'm afraid I can't do that, Dave" sudo "Open the pod bay doors, Hal" > alright
When exactly was it on track? They've failed everytime they've sent it haven't they?
You're nothing; like me.
It is an interesting idea -- if it can be made to work...
i am a soviet space shuttle
Partially true. While it is indeed correct that the "thrust" that a solar sail can take advantage of (photons striking the sail surface) decreases as the vessel moves away from a star (our sun, for instance), one must remember that according to the Laws of Motion, an object that is in motion will remain in motion unless an external force acts on it. This means that even after there is relatively little motive force (photons) to be used to accelerate the craft, it will not decelerate either as it passes through interstellar space. Essentially, there would be no positive or negative acceleration during the cruise phase to another star, but as the craft approached that star, the photons that it emits can be used to slow the craft down -- and final deceleration and orbital entry could be accomplished by nuclear or chemical rockets (or even ion propulsion.)
i am a soviet space shuttle
"We choose to go to the moon. We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win, and the others, too."
It is from an address given at Rice University in Houston (where Mission Control is located) on September 12, 1962. This is also the speech that contains the phrase "We set sail on this new sea because there is new knowledge to be gained, and new rights to be won, and they must be won and used for the progress of all people."
I look up to Kennedy because he was so truly enthusiastic about the space program like no President since has had the guts to be.
i am a soviet space shuttle
First, it helps to bring the concept of the solar sail as a valid idea to the public eye. Solar sails have been something of a mainstay in some science fiction series as a way of getting to other planets and have even shown up in some popular sci-fi series (one episode of Deep Space Nine, for instance, showed an old Bajoran solar sail vessel, albeit with far too little sail area to accelerate as "fast" as more serious concepts would). However, other more conventional systems (by far the chemical rocket, but followed to a lesser extent by nuclear rockets (does anyone recall the NERVA program that might have sent humans to Mars by the 1980s?) and ion propulsion: how many of you knew that the term TIE Fighter from Star Wars stands for "Twin Ion Engine"? Star Wars never stated what gas was used in those systems, but the gas that has been used in the Deep Space 1 mission and in the Artemis commercial spacecraft. Now that the Planetary Society, which is a well-respected organization, has attempted to actually fly a solar sail, the public will become aware of the possibility.
It helps to bring the existence of such organizations into the spotlight as well. The Planetary Society has been active for decades -- it was founded by Carl Sagan -- and there are others, including what is perhaps the best-known of these groups: the National Space Society. Others, far less well known, exist, ranging from fan clubs for shows like Babylon 5 (which I applaud for showing what space exploration will be like in perhaps a few decades once we've gotten the hang of building spacecraft with rotating gravity sections to avoid the problems that long stays in microgravity cause) to other grassroots groups that give more or less anonymously (that is, they don't get press coverage) to serious efforts.
And it also helps to give people like us the idea that we might eventually actually get to go to space ourselves. If someone can spend $20 million for a ride on a Soyuz capsule, and if a non-profit organization can launch a solar sail, then what could happen in fifty years?
This was, like Apollo 13, a "successful failure".
i am a soviet space shuttle
Well, actually, solar sails don't work in just a bee-line method... they travel in orbits around suns, using different angles of photons hitting the sail to keep in orbit.
To move into a farther away orbit, they just tilt the sails more towards the sun. To move closer, they just tilt the sails away and let gravity take over for a bit. A way to travel large distances would be to just remain in a very close orbit with the sun, gaining speed, and then suddenly tilt the sail at the desired angle to propel the craft in the right direction.
After reaching another star, the speed will be very fast, and it can be slowed down by just tilting the sail towards the other star and entering into its orbit, perhaps.
...if the supplier of ballistic missles to the worlds crackpots cant even hit space, which you have to agree is pretty bloody big, with a giant inflatable sail... then there is no chance they are going to hit a city they cant even see with a tiny little warhead!!! :)
:)
I knew I should have kept my mind shut
err!
jak.
---
"I have gravel rash..." Rachael Howard, c1999
Solar sails aren't all that good anyway. Sure, you don't need to bring any fuel, but they'd take forever to accelerate, and wouldn't work as well when they're farther from the sun! If you want a real efficient drive, nuclear pulse propulsion is the way to go. Exploding nuclear bombs behind the spaceship to push it forward, basically.
Too bad it's illegal.
All it takes is nukes and nerves.
Please do some research before stating what you believe to be fact.
l .h tml
Radiometers can operate either using light pressure or thermal transpiration, depending on the construction. However, every radiometer you are likely to see operates on thermal transpiration.
If you actually had a clue and could recall playing with one of these, you would know that they turn AWAY from the black side, which is opposite what you describe.
Had you ever played with a true solar-sail type that turns TOWARD the black side, you would have broken it, as they are extremely delicate.
Please refer to the URL below for a more in depth discussion.
http://math.ucr.edu/home/baez/physics/light-mil
So we finish the eighteenth and he's gonna stiff me. And I say, "Hey, Lama, hey, how about a little something, you know, for the effort, you know." And he says, "Oh, uh, there won't be any money, but when you die, on your deathbed, you will receive total consciousness." So I got that goin' for me, which is nice.
Not A Sig
Comment removed based on user account deletion
Using lasers to boost it would be wildly inefficient
No, the theoretical maximum would be close to the speed of light, since your propulsion source is traveling at light speed. A laser can actually provide quite a bit of thrust and can be powered by more efficient means than a reaction-based spacecraft. For example, you could set up a solar array on the moon to power the laser. You can then add thrust to the spacecraft without it having to carry fuel. You could use the same solar array to power a mass driver to launch minerals (and perhaps water) out of the moon's gravity well. We need to start prospecting the moon and asteroid belt and quit tearing the earth apart.
Enigma
Enigma
It may have failed as a solar sail, but it did work perfectly as a drogue chute.
He put his boots up on the table and made a face. "The sig," he smirked. "You can waste your life in search of the sig."
the momentum of a photon is planks constant * frequency therefore, a high frequency photon has high momentum. also, you have a little classical physics wrong, too. p=mv E=antiderivitive(p) = MV^2/2
Spring is here. Don't believe me, look outside!
Could you "tack" in an orbit around the sun to build up speed, then break away? I'm pretty sure this would work.
Imagine having the sail at an angle to the sun, the craft placed in orbit around the sun, and the solar wind coming out radially. The path of the spacecraft would be perpendicular to the solar wind, so with the sail angled correctly, you'd accelerate in orbit.
Or something.
We take it as a loss and move on to try again. $4 million can be raised again and could be raised many times over for the amount of money spent on many other space related projects.
Something like solar sails, which can have an immediate return when demonstrated as a proof of concept, should have higher priority over things like missions to Mars, which can not only benefit from the solar sails, but which also provide a return much later. Giving it that type of priority, it could be ready in a couple of months.
In 400 years someone will be sitting on Mars sipping wine in a city and not even remember that a solar sail project in 2001 failed.
"Beware of he who would deny you access to information, for in his heart, he dreams himself your master."
How much government funding did Edison receive?
How much government funding did ARPANET receive?
Kill, Tux, kill!
Use two counter-rotating windmills, one on the generator's armature, the other on the rotor.
On the other hand, you could use solar cells. For either one to work, you'd still need sufficient numbers of photons, leaving you powerless between stars.
I wonder if the original intent for the windmill design was to provide propulsionless spin for keeping the sails taunt. After sufficent RPMs have been achieved, the pitch on the "blades" could be flattened out to stabalize the spin rate.
science is a religion
Yes, Offtopic....
Brings back memories of myself in gradeschool trying to work out the physics of solar sails...Remember well my dad explaining that the thrust would be extremely low, otherwise "Whenever you turn on a flashlight it would blow your ass out the window" (Yes he is twisted also)
Gah, the technology is already there, I worked on and did research for a thermonuclear propulsion project, pellet bed plutonium reactors (using WEAPONS grade plutonium no less) provide a wonderfully high impulse, with hydrogen as the moderator for the core (Bussard Ramjet anyone?). Unfortunately the fightback from the green groups have basically stoppped large scale projects like this in their tracks.......*sob*
You're Alex Chiu and I claim my $5!
One line blog. I hear that they're called Twitters now.
I agree. Our society has slipped to the level that we don't bother trying because somebody decides that it cannot be done. The space prgram shows what we as a species can do when we put enough effort into it.
IANARS, (I am not a rocker scientest) but since there isnt much in deep space to push off of, how would a windmill help?
Unless, they plan on spinning some sort of generator, to power other parts of the ship (Lights, air scrubbers, ion thrusters, whatever floats your boat). Damn. that would be a good idea. leme go patent that.
The opinions in this post are ficticious. Any similarity to actual opinions, real or imagined, is purely coincidental.
This is perfectly alright and all, except what happens if we need to approach a star that has a higher strength solar wind than the one propelling the craft? It seems to me it wouldn't matter what color, etc., the reverse side was, you'd still get a pressure front pushing you away. Thus, wouldn't some stars be impossible to approach with this technology? Kinda like a one way ticket to the moon; you can get there rather elegantly, but you just can't come back using the solar sail. I realize that I'm not an expert, and perhaps someone can clarify.
I did see an article, I'm not sure whether it was a magazine article or on Slashdot (or both), about a similar idea and application being used as a method to get to the moon. In essence, you make a space craft with a mirror on the bottom. Then you construct a really friggin' powerful laser, aim it at the bottom of the spacesraft (the mirror), and off you go. Darwin award, anyone?To hope, though, there is my favorite engineering saying: It works in reality, but will it work in theory? Just my two cents.Way to steal from a Larry Niven short story.. the one about the teachers from another planet who gave people pills to learn skills.
Why don't you suggest that we make our sun go nova instead?
you should find something more esoteric to plagarize in this arena.. I'm just shocked that nobody has commented on this yet.
Brant
Brant
Argle. Bargle.
is it just me or are the space projects of the last few years getting cheaper and less productive? What happened to the geniuses that all went to work for Nasa? Since Challenger i haven't seen anything from the space programs that got the entire country excited. sure the mars lander was decent- but it broke. i mean, really, who are these people?
Alcohol doesn't affect your judgement as much if you know exactly where you stand.
Indeed. It's easy to do the things we're pretty sure will work. Chances our we will suceed, but nothing will really be learned. It's only when we do things we're not positive about do we learn.
I'm paraphrasing, but I'm reminded of JFK's quote:
We do this not because it is easy, but because it is hard.
(something close to that).
I wish more people would adopt that attitude.
If the press notices at all, I'm sure we'll get to hear how much money was "wasted" on this failure. I wish people would accept that failures are part of learning. This is true of all aspects of human life. As long as they find and correct, and learn from, the problem, then nothing was wasted.
I think you use the lasers at the start, when the sail is still reasonably close in. Unless you're a Motie, of course - but I bet Motie Engineers could hold a beam within 10exp-10 degrees. (Niven/Pournelle reference).
In any case, the sail would be not 1 metre, but more like 1-10 km across. And course would be fairly easy to predict; virtually no forces acting except the laser, once you're outside the solar system.
...sometimes comes down. I hope this project succeeds, and I think it or one like it will ultimately, but aren't they a little worried about their spacecraft hitting the ground? While not densely populated, the Kamchatka Peninsula does have people living there, not to mention lots of wildlife. I thought the launch from the sub was part of making sure when it came down it did so in the ocean.
Although photons do carry the electropmagnetic force, light is made up of randomly polarized photons and therefore cannot provide propulsive force. Also, since photons have no mass, they cannot have momentum, because momentum=mass*velocity^2 Only particles with mass can propel a solar sail.
Hmmm...you might want to explain that to the folks over at the Interplanetary Society before they send up another one of these things, as they seem to have different ideas:
JPL and NASA seem to be under similar delusions.--
--
$ chown -R us:us yourbase
Here's a good site on how these babys are proposed to work.
---
I got nothin'.
Earth-based lasars can be used once the push from the sun becomes null. I don't know to what distance a lasar keeps its integrity, but I know it's alot farther than the sun can.
I hope this solar sail can be reconstructed soon so that we might live in a future much like the one portrayed in the movie "Tron". However, if it continues to fail, its chances of succeeding are going to be much slimmer ..
Can someone explain to me if, how, and why we use different rockets for manned vs. unmanned missions? Why not just use the most reliable types? Is it a cost issue? Are the manned rockets really safer?
Ok... enough of that. Just a little joke to relax the people (including me) who are infuriated with the Sklyarov thing.
How come they don't just give this sail to some guy who's about to visit the ISS and just have him toss if overboard from ISS?
DUH!!!
The problem is, it would have to stay close to the sun to get much thrust. To stay close to the sun, it would have to maintain a low speed. It could never get going fast enough to travel interstellar distances any faster than the rockets we already have.
Repeal the DMCA!
Light (photons) have no propulsive force, because they have no mass. The propulsive force of the solar sail will come from Protons and Helium nuclei that are ejected from the sun at high sub-light speeds.
Repeal the DMCA!
Well, the way for it to achieve the maximum possible velocity would be to maneuver into a highly eliptical orbit around the sun, and then after passing the closest point of it's orbit, align the solar sails to create the maximum thrust. Even then, it would only be able to slightly exceed escape velocity from the sun. Conventional rockets can (and have) already done that. Solar sails are wildly impractical except for travel within 1 or 2 AU of the sun.
Repeal the DMCA!
Nevertheless, the fact remains that it is physically impossible for it to get going more that slightly faster than escape velocity from the sun, because as it builds up speed, it would migrate to a larger orbit. Using lasers to boost it would be wildly inefficient, because the momentum imparted by the light would only be an infinitesimal fraction of it's energy.
Repeal the DMCA!
no, that is a thermal effect on the low pressure gas in the bulb, which is a hell of a lot stronger that what the solar sail will use.
Repeal the DMCA!
Nevertheless, it would be impossible to significantly exceed the sun's escape velocity, because as the speed increases it would spiral away from the sun and lose thrust. Several probes running on concentional rockets have already achieved escape velocity from the solar system. Solar sails are only good for saving fuel on intrastellar travel within an AU or two of the sun.
Repeal the DMCA!
...your laser pen would push itself across your desk.
The propulsive force of light is only a tiny fraction of the energy carried by it. Therefore, using an orbital laser to push the solar sail once it got out of the sun's range would be wildly inefficient.
It would also be extremely difficult to develop the proper targeting mechanism. Do you haver any idea how hard it is to hit a 1 meter cross section from a light year away?
tan^-1(1/(9.46*10^12))= 1.057*10^-13
The laser would have to be accurate to within a ten trillionth of a degree. The earth's own gravitational field bends light more than that. And, since it would take a year for its image to reach us, and another year+ for the laser to reach it, the course would have to be extrapolated 2+ years ahead. That could create major problems.
Repeal the DMCA!
Why do we need interstellar travel? Dont we have enough problems here to fix? Is this a Microsoft thing? To "fix" it, just wipe the slate and start over? (refering to fixing Win installs by re-installing)
Aside from that, space travel would be pretty damn nifty.
Carpe Noctem -=- Seize The Night
No. What kinda thermal effect makes two different pressures in the same chamber of gas? Besides, the light bulb is evacuated. There's no gas to work with anyway.
The anonymous guy with the good memory of grade-school science is absolutely right. The photons are reflected off the shiny sides of the metal, and simply absorbed by the black sides. Thus, the shiny sides are "pushed" rougly twice as hard as the black sides, and the whole apparatus (which is pretty substantial compared to the photons pushing it) is accelerated.
This is the same principle applied with solar sails, the old "Star Wars" missle defense project, and any other tech using the same principle of imparting light's momentum to something else. Of course photons don't have a lot of momentum indivdually. The key is in the NUMBER of photons hitting your target. Stay in school.
"F***in' with your theology like Darwinism in the Bible Belt..." --El-P
"F***in' with your theology like Darwinism in the Bible Belt..." --El-P