Effect stems from cumulative push of light photons striking probe
Article Source: msnbc.com
from:msnbc.comJapanese solar sail successfully rides sunlight
Seeded on Tue Jul 13, 2010 10:35 AM EDT (msnbc.com)
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2/10,000ths of a pound of pressure? Wheeeeeeeeeee! We're movin' now. But if you multiply that by several years ....... bacterial flattice would still be faster. Milestone? Not hardly, rather expensive demonstration of already proven theory.
Run the numbers. Direct acceleration at that force/mass will nominally move the craft 1 million km in 28.3 days or 1 billion km in 896 days. Actual case is more complicated that that since it's sailing and needs to manuever about. Maybe 3 times these numbers of days in actual practice?
My numbers tell me this kind of acceleration will move the craft 1.7 million km in one year.
a (acceleration) = F (force)/m (mass) = (1.2/1000) x (1/315) = 3.8 10 -6 m/s2.
s(Distance) = 1/2 x a (acceleration) x t (time) x t (time)
If the craft travels at this acceleration for one year (86400 x 365 seconds), then distance travelled:-
= 1/2 x 3.8 x 10-6 x (86400 x 365) x (86400 x 365) meters
= 1. 9 million km.
Enough to cover the distance between Earth and Sun.
I admire the calculations and the overall explanation you provided Rakesh.
There's only one problem with your reasoning. The distance from the Earth to the Sun is on average 150 million km - not 1.5.
At this rate, assuming a constant rate of speed and no further acceleration, it would take close to 100 years to make the journey between the sun and earth.
I acknowledge that my own reply here is flawed because of the statement 'no further acceleration' since the entire idea of solar sails is the same concept as Ion propulsion where a tiny but continuous force causes gradual but constant acceleration which will eventually catch and even exceed the velocities achieved by more conventional propulsion systems. But THAT math is WAY out of my league.
My bad, jmp9633. Thanks for the correction.
The distance between Earth and Sun is 150 million kms. Which means, as you said, it will take close to 100 years to reach the Sun.
As the story stated, it is accelerating. What I'm wondering is as the distance between the source and the spacecraft increases will there be an eventual decrease in acceleration. At any rate this is some pretty cool science.
The acceleration the sail gets is directly proportional to the flux of solar radiation where the craft is. The farther it gets away from the sun, the more the sun's light will be spread out so the flux will go down and so will the acceleration of the craft. It will still have all the speed it has already built up though.
think about the improvements in hibachi cooking. the japanese are going to tech themselves to another plane of existence
I don't think this is an "interstellar" mission - this probe won't be traveling from one star to another.
I'm glad someone said this... No, it won't be interstellar. It's heading to Venus. Although I don't remember if it said it would go into orbit around Venus or not.
Well unless the craft crashes into one of the outer planets like the Galileo mission did it has to go somewhere. Further, since the craft is constantly accelerating it should be moving pretty fast when it eventually does leave the solar system. That said it doesn't sound like they've aimed it Proxima Centauri or any other close star and it would still take way to long for the craft to get there. We already have interstellar spacecraft though at least one of the voyager probes and probably both have passed outside of the sun's heliopause, the line separting the solar system from interstellar space.
I would like to point out something in the text. The IKAROS was not the only one launched. There was a second shuttle launched just before IKAROS. It is that one that is on its way to Venus.
It's traveling away from us and never going to return, and the suns rays reach very,very far, as well as other radiation that it might catch, it just might be the first interstellar solar powered craft, it's possible.
according to wikipedia Ikaros will spend six months traveling to Venus, and then it will begin a three-year journey to the far side of the Sun. the wiki page doesn't mention anything of the mission after it reaches the far side of the sun. If successful, IKAROS is to be followed by a 50 m (160 ft) sail, intended to journey to Jupiter and the the Jupiter Trojans, later in the decade.
As Ikaros get closer to the sun it will gain speed, and this speed will not decrease. there will only be an increase in speed of the crafts lifetime. very exciting!
and yes as far as the mission outlines i have read for Ikaros it is only an "interplanetary" craft. not interstellar. but there is no plan to get Ikaros back so unless it's gobbled up by the sun or the planets it will likely follow in voyager footsteps and just keep on goin'.
I would like to point out that wikipedia is an unreliable source as it allows anyone to edit information.
a sufficiently sized solar sail will allow near light-speed travel. it will take a very long time to reach that speed though.
I'm no expert on this, what so ever, but my curiosity is running wild. Could the solar sails be made of such a material that it not only propels the spacecraft, but also generates some electricity for it? Wouldn't that be even better? Possible uses would include power for the on-board electronics, additional means of propulsion using ion propulsion engines so you can use it in emergencies, steering of the spacecraft, maneuvers and such? Like I said, I'm no expert on the subject, but it seems to me that if such material does exist, having it do a "double duty" of a sort, would be very beneficial for the overall usefulness of the spacecraft.
nice idea! could also be used in growing food!
Croatian, follow this link http://en.wikipedia.org/wiki/IKAROS and you'll see a good description of the solar sail. but yes, solar cells are included within the design to allow for electricity generation. steering the spacecraft for "solar sailing" would be an excellent article in and of itself, the wiki link has a little info on that but a little google searching of Ikaros will yield all your answers.
Mana, yes -theoretically- you could reach near light speed. the quickest way to accomplish this would be to have (in essence) the photon radiation source at the optimal distance (closer the better) to the solar sail and if that distance remained constant you'd have a constant increase in speed (as long as no other forces acted against it). but since you can't drag the sun behind you this isn't a likely scenario.
That's definitely not an interstellar mission. Being generous, we could call it one if the plan is for it to gain enough speed to leave solar orbit, which is 42,100 m/s. At 1.12 mN on a 315Kg object, it would take about 375 years to get up to that velocity. It would be neat if over the next couple of years they can raise the orbit by several Km, which would retire some thermordynamic objections, but there's not way this is an interstellar mission.
fair enough on the math, but the practical definition of an escape velocity is lost. i could eventually leave the solar system at 55mph, if i had a constant source of thrust.
Why is this described as an "interstellar" mission? To what star system is this demo craft moving towards? Really, MSNBC should get better science writers (or editors) than this. Actually, I would like to volunteer! MSNBC please contact me vial email (-: ... seriously
The article and comments are very informative . I'm going to say this just as a joke ,and don't want to take away from the article or the comments .
What are they doing ? Adding more space junk for us to keep up with , for the next hundred years .
But really I'm very glad they've proven this works .
"It is the first solar sail to actual fly on an interstellar mission."
A trip to Venus is NOT an "interstellar" mission. It is INTERPLANETARY. It behooves an editor to assign people who know a little science to write stories on the subject.
I think the intent is for the solar sail to be interstellar. It just was launched on the same rocket as the Venus orbiter. But, I think they have gone their separate ways.
Ikaros has 4 objectives. 1.) Deployment and control of a large, thin solar sail membrane. 2.) Thin-film solar cells integrated into the sail to power the payload. 3.) Measurement of acceleration due to radiation pressure on the solar sail. 4.) Attitude control via variable reflectance liquid crystal panels.
that info comes from wikipedia. in 6 months it will pass Venus but it will not conduct any "venus science". after it passes Venus it will begin it's 3 year journey "to the other side of the sun".
JAXA (obviously) has more info about their craft.. http://www.jaxa.jp/projects/sat/ikaros/index_e.html
OK , this is a simple question . When it gets to the other side of the Sun . How will we know it's still where ? Then in another 3 or 4 years from then will it come back around to this side ? How fast might it be going by then ?
I don't know. that's a good question. presumably with the liquid crystal system they will be able to steer this thing. and with the thin film solar cells it'll have power. so providing JAXA is intent on controlling this craft from mission control they should (i would assume) be able to steer this thing where ever they want (keeping in mind they need the photon pressure on the sail to steer it). I may have that wrong but that's what it seems like the plan is. also it appears that it will be picking up speed all the while. so i'm sure some mathematician can give you a better idea than i can about how fast this puppy is going, but i would guess it's safe to say Ikaros started out at least at 27,000 kilometers per hour (low earth orbit - 8km/s=8,000m/s). by now it's traveling considerably faster (since it's not in orbit and has it's sail open). I don't know where CDH CDH got this number but he (or she) stated that to escape solar orbit is 42,100 m/s. i don't know whether that is mile or meters per second. but the speed of light is 186,000 miles per second (299,792,458 meters per second). So, I would guess (and i'm no scientist) the "42,100 m/s" number is in meters per second (since the majority of the world operates in metric).
Okay okay okay. 1.2 milliNewtons, by light from the sun, is pushing Ikaros away from the sun. Lets think about this.
Ignoring the effects of general relativity, we can use the law of universal gravitation to find out the force towards the sun.
F = m1 * m2 * G / r^2
m1 = 315 (Ikaros weight)
m2 = 1.98892E30 (Solar weight)
G = 6.67428E-11 (Universal gravitiational constant
r = 1.4E11 (a guess of 140 million km, 10 million km closer to the sun than earth, since it's going towards venus)
F = 315 * 1.98892E30 * 6.67428E-11 / 1.96E22
= 2.13 Newtons
So, the force this craft is getting from the sun's light is 0.056% of the force pulling it towards the sun. Call off the party lads, this thing isn't going anywhere any time soon, unless they can make it 1800 times lighter (or my calculations are out by 3 orders of magnitude).
Accelerate/decelerate at right angles to the sun to change orbital distance instead of fighting solar gravity directly. Since propulsion mass isn't an issue, may be able to do unlimited # of slingshot manuevers to boost speed. Question is whether or not can manuever fast enough/often enough to make make multiple slingshots realistic, and how often planets are in a good alignment to be effective.
Another scenario, being able to launch un-manned supplies to an inhabited martian base at any time, instead of waiting for practical launch window due to fuel limitations. This would allow the manned mission to be lighter and/or faster and/or larger, with supplies being sent both before and after the manned launch.
Yeah that makes sense I guess.
Not so much a greater velocity - since the thing is already orbitting the sun and thus must have enough velocity to not be pulled in - but a change in energy which moves it out to a greater orbit.
What a n00b mistake :(
This is a novel idea but is impractical. The light from the sun has little effect past the asteroid belt, probes that visit the outer planets cannot rely on solar panels to generate electricity. They rely on nuclear power cells utilizing Plutonium 238 by generating power through nuclear decay. The money being spent on this technology, in my opinion, is a waste and should be used for nuclear propulsion which is the only way we can accelerate spacecraft fast enough to make a manned mission to Mars or the outer planets feasible.
you say that as if you've invented the technology that will accelerate spacecraft fast enough to make a manned mission to Mars or the outer planets feasible. so if you wouldn't mind i'd love to here a description of your nuclear propulsion device. since it's "the only" way to do it, i'd love it if you'd share your vast knowledge of the subject with the group.
Just like a wind sail, a light sail can be adjusted to either gain speed if angled away from the wind/light source or lose speed if directed into the wind/light source.
Some of the commenters above seem to assume that a spacecraft leaving Earth, fly's in a straight line to it's objective. That is not the case. Even while flying away from the Earth, it is still in orbit around the Sun. To go to the orbit of an inner planet, the spacecraft has to lose speed in relation to the Sun. It then spirals in to a closer orbit. To go to an outer planet, conversly, it has to speed up in relation to its orbital speed around the Sun.
and centrifugal force would "slingshot" the craft after it "passes" the sun (or other massive body)... that reminds me of a rush limbaugh joke.
Rush Limbaugh is a fool who needs to check his "facts" before he goes spreading them to the general populace of the US who take his word for it.
I'm wondering just how a space craft might accelerate and decelerate in a controlled manner by turning the space craft. Sunlight travels in just one direction, outward from the sun. I don't believe that "tacking" into the solar wind would be possible. Can anybody explain this further?
Also, how would interstellar travel be possible using solar sailing? Any significant propulsion would be gone after leaving the inner solar system.
first and foremost your comment about sunlight is wrong, or at least ill-conceived. sunlight does not travel "in just one direction". it's true the photon moves at the speed of light away from the source of the photon. some may think of that as a straight line. and for the most part that is correct. but to be accurate in your statement, Sunlight radiates in all directions from the sun. the big idea with solar sailing is to build up speed. once the necessary speed is built up (within the inner solar system) the momentum will carry it the rest of its journey. add into that precisely calculated trajectories and "slingshots" wherever possible and these things will be cruising out of the solar system without the further need of it's solar sail.
How many solar sails from far, far away have passed be us ? Now that we have one of our own .
Now we'll know what to look for . A new form of U F O . Bubba will tell you he's been seeing then for years .
Tell me the truth , I won't tell anybody . Have you seen any U F O's ? They'll only keep you in the rubber room for a week or two , if you've seen one . The food isn't that bad there , but don't take their drugs . You'll start seeing things , those snakes and spiders are not real , it's just the drugs .
Come on , tell us . Me and Bubba won't tell nobody . --- RON
I just have one question. Yeah, it's all well and good that people can use solar sails, but what are the disadvantages? Every plan has them, and reports such of this usually tell only one side of the story. Why haven't scientists used them before now, if they are so handy?