Solar Sails

Re:Tiny bubbles... by Anonymous Coward · 2001-02-26 21:56 · Score: 3

Normal sized spacecraft in Earth orbit have to correct their position and attitude for the effects of solar pressure, along with other disturbances from gravity gradients and residual atmosphere. The solar influence is usually small, we are talking about micro-Newtons, but because the duration is long, it can have a significant affect. Since the largest component area-wise of most satellites are the solar arrays, which are normally about 20 m x 1 m x 2 (satellites are normally symmetrical to avoid rotational disturbance torques) they only have an area of around 40 m^2, compared to over 700 m^2 for the solar sail proposed. I'd suggest this is more than big enough for a proof-of-concept vehicle!

Re:Better technologies out there by dair · 2001-02-26 21:35 · Score: 3

it's not that practical for planetary travel, or even interplanetary travel

This is exactly what it's good for - the speed builds up extremely slowly (it only has the pressure of the solar wind driving it), and so the further you need to travel the more effective it is.

You need a more maneuvourable (sp?), or faster reacting, engine for that when it comes to landing, emergency procedures, etc.

You certainly do, but that's not what you would use a sail for. They're intended as a replacement for the long slow burn you need to get to your destination, so you don't need to carry a huge mass of fuel just to get there (instead you can save most of it for the final manoeuvres).

-dair

Small question... by Psiren · 2001-02-26 21:26 · Score: 3

But get how they plan to launch it: on a Russian submarine ICBM.

Why is that particular point made? Because its Russian, or because it's an ICBM? Neither seem overly unusual to me. Russians have a good deal of expertise when it comes to space technology, arguably more so than the US. And using an ICBM kinda makes sense. I believe they've been bandying this idea around for quite a few years.

Re:Small question... by vidarh · 2001-02-26 22:36 · Score: 5

Launching from a sub does make sense for several reasons:
First of all, the Russians do their land based launches from Baikonur, which is relatively far north. Normally, you'd prefer to do launches close to equator to get the maximal benefit of earth rotation. The Russians incur a lot of extra costs because of the position of Baikonur. (and this is also one of the reasons for the orbit MIR is in - they need to get it far enough north to be able to reach it cheaply from Baikonur). Launching from sea means they'll be able to launch from international waters and be independent of having their own land based launch areas near equator.
Second, there's strict international regulations on such launches, to prevent interference with aircraft. Which you should be happy about the next time you're flying anywhere... :) Launching from sea simplifies things, because most traffic is clustered around or between big cities, and the further out at sea you go, the less flights will pass through the area. So it reduces the administrational issues of ensuring no passenger flights or other aircrafts pass right overhead during the launch.
Environmental effects and other hazards are always an issue during rocket launches. The rocket can misfire, or explode. Parts may be hurtled through the area in the case of an accident. Dangerous materials or toxic gases may be released as a result of fire etc. Tons of things can go wrong. While it won't be good at sea either, at least you face less immediate threats to human life.
You also lessen the environmental impact of indigneous animals etc. (which has been a major concern with ESAs Ariane launch site in Central America).

Re:Tiny bubbles... by wmoore · 2001-02-26 22:31 · Score: 3

The tubes wouldn't have to be that strong if only small pressures are used inside of them. Because space is essentially a vacuum, you can use a very low pressure inside the tubes to accomplish the same thing. It's the difference in pressure that matters.

Re:This is part of our destiny. by Hard_Code · 2001-02-26 22:43 · Score: 3

"conquer space"

Oops, you have pushed my critique-of-western-thought button! What is it with "conquering" everything? We have to "conquer" the New World. We have to "conquer" nature. We have to "conquer" space.

"Einstein irrefutably proved that travelling faster than the speed of light is utterly impossible"

Well, it was a postulate that has been held up so far, but recent experiments throw inklings of doubt. Beware of absolutes. I don't think much in physics is "irrefutably proved".

"When the singularity comes, as predicted by Vernor Vinge, I shall be among the first to upload."

Yes, drink the kool aid...

It's unfortunate that the west is so fatalistic. I took a look into transhumanism and was at first intrigued, but then got disgusted with its arrogance, fatalism, and irresponsibility. I'm happy being just a plain ol' human. It's this urge to "conquer" to escape and be something else that leads us down all sorts of wrong paths in search of some mythical salvation. bleh

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It's 10 PM. Do you know if you're un-American?

Re:A Clean Alternative by istartedi · 2001-02-26 23:23 · Score: 3

Sailing was the most environmentally healthy way mankind ever developed to traverse large distances

I beg to differ about sailing being environmentally clean.

The forests of North Carolina were decimated for masts and pitch to build English ships back in colonial times. The interior environment aboard ship was notoriously bad. The name "horse latitudes" comes from the fact that when ships were becalmed, they had to kill horses and dump them into the ocean. Not a pretty site.

True, oil tankers occasionally befoul beaches. OTOH, the US has more forest today than it did in the 1800s, and that's because we rely on oil and steel, not canvas and trees.

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For all intensive purposes, "whom" is no longer a word. That begs the question, "who cares"?

Re:This is part of our destiny. by Enigma2175 · 2001-02-26 21:39 · Score: 3

As Einstein irrefutably proved that travelling faster than the speed of light is utterly impossible

Nobody has ever irrefutably proved that it is impossible to travel faster than c. That it is why it is called the theory of relativity, not the fact of relativity. In fact, I have recently seen articles about scientists accelerating (admittedly massless) particles faster than the speed of light. And the speed of light may actually have a higher limit, check out this article. Hardly anything is ever proved, we just refine our theories by observation and hypothesis and we get closer and closer to the truth.

Enigma

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Enigma

Homer's response by OlympicSponsor · 2001-02-26 21:43 · Score: 3

"...Solar Sail powered by light."

Homer: So, they have solar sails powered by light now.
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Non-meta-modded "Overrated" mods are killing Slashdot

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Non-meta-modded "Overrated" mods are killing Slashdot
(Hey Ryan! Here's your proof!)

ICBM==Earth-Earth Payload, not Earth-Space by daveym · 2001-02-26 21:54 · Score: 3

It seems that this point was made because this is highly unusual:

#1) It is a Russian weapon system.

#2) It uses a submarine as a launch platform. How many satellites get launched from submarines?? That is extremely unusual.

#3) An ICBM is not designed to loft a large-size payload. A set of MIRVs, while very heavy, is relatively compact.

#4) More to the point, an ICBM is not designed to deliver a payload to space. It is designed to deliver a payload to earth. Why do you think that Alan Shepard's flight lasted only 15 minutes? Because he was sitting on top of a Redstone ICBM.

So yes, it is overly unusual.

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"Chill, Orrin!"---Trent Lott

Tiny bubbles... by banuaba · 2001-02-26 21:29 · Score: 3

Pretty nifty.. But I have a couple of problems/questions..
It says that the sail is only 30m in diameter. I was under the impression (from reading Omni magazine and Larry Niven, admittedly not the most reliable of sources) that one needed a sail of huge (kilometers) size to be able to get a noticeable boost from the solar sails. Also, the article says that they're using inflatable tubes to unfurl/stabilize the sail. IANAP (IANA Physicist) but wouldn't that make those inflatable tubes have to be tremendously strong to be able to survive in the low-pressure environs of space?

Those thoughts aside... It's pretty cool. And I wish I could launch my girlfriends cat out of a goshdarned ICBM tube.

Brant

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Brant

Argle. Bargle.

I can see the exchange now... by Chris+Burke · 2001-02-26 23:21 · Score: 4

Norad: Umm... We just detected a ICBM launch from the Russian submarine Smirnof.

Kremlin: Not a problem, comrad! Is just launch of solar-sail you may have been reading about on slashdot.

Norad: Okay... Umm... Our projected trajectory puts it landing in Washington, DC.

Kremlin: Is normal! It will separate at high altitude and booster will fire sail into space. Missile will fall harmlessly into Atlantic.

Norad: Okay... Umm... The ICBM appears to have landed in the capitol, exploded, and wiped out our entire government...

Kremlin: Is this a problem, comrad?

Norad: No, not really. Just commenting.

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The enemies of Democracy are

Wrong one! by Wog · 2001-02-27 00:05 · Score: 4

But get how they plan to launch it: on a Russian submarine ICBM.

(Jump forward 4 years, under the sea, in a Russian sub.)

Weapons Officer: Missile number five has been launched. That's one small step for man, one giant-

Captain: Gustov! You mean missile number nine, right?

Weapons Officer: Shazbot!

Re:This is part of our destiny. by JCMay · 2001-02-26 22:19 · Score: 4

I read that link you posted, and I am unimpressed. All they did was prove that the phase velocity of a propagating EM field can indeed go faster than c. The article even mentions the sweeping beam of a lighthouse. If we assume that the beam is rotating with an angular velocity P, then at some point away from the lighthouse r, the linear velocity of the beam v will be equal to c: v = Pr. That's easily determined: r = c/P. Beyond this radius the linear velocity of the beam will be greater than c even though the beam propigation in the r direction will be only equal to c.

Of course, if you wanted to send a signal faster than c, the group velocity of that EM field would have to exceed c, which it doesn't.

Since the speed of light, c, is determined by whatever the substance is that the EM field is propagating through by the equation

c = 1/sqrt(u*e)

Where u is the permeability of the substance and e is the permittivity. Each of these values is made up of two parts, the intrinsic value and the relative value. The intrinsic permeability of free space (u0) is 1.257e-6 H/m. The intrinsic permittivity of free space (e0) is 8.854e-12 F/m. In a vacuum the relative permeability and the relative permittivity are both 1. This gives a free-space value for c of 2.998e8 meters/sec.

In a non-vacuuum, either or both of the relative terms will be greater than 1, and the value of c in those mediums will be less than the free-space value.

The key to propagating signals faster than 3e8 m/sec is to find a material with a dielectric constant (relative permittivity) between zero and 1. These materials don't exist, however.

The Father of the Solar Sail.... by GeneralEmergency · 2001-02-27 00:28 · Score: 4

I was fortunate enough to be in Russia several years ago (as part of a NASA contract) and got to meet and work with Professor Vladimir Syromyatnikov, the father of the Solar Sail, who is one of the most gracious and intelligent men I have ever met. He is truly a brilliant mechanical engineer. His genderless docking collar design is a work of poetry in steel.

The good professor was kind enough to invite me up to his apartment one day to talk over lunch and meet his wife and family.

I often think about that afternoon and in particular, one corner of his living room where his television set was placed. There, atop the tv was a VCR and yup, you guessed it, the clock was blinking "12:00". To this day, whenever I need to assess my own failings, I just remind myself "Even Rocket Scientists can't do everything".

You can email the professor at:
vladimir.syromyatnikov@rsce.nasa.ru

"A microprocessor... is a terrible thing to waste." --

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"A microprocessor... is a terrible thing to waste." --
GeneralEmergency

Space.com by Eoli · 2001-02-26 21:15 · Score: 4

Space.com has more on the subject here.

There's a better way.. by Blind+RMS+Groupie · 2001-02-26 21:29 · Score: 5

This is certainly interesting, especially in that it's being done by a private firm, but I find the idea of Mini-Magnetospheric Plasma Propulsion (M2P2) much more fascinating. The idea is that you replicate a miniature version of the Earth's magnetosphere around a spacecraft and let the plasma push against that instead. The beauty of it is that thrust remains relatively constant because as the craft moves farther away from the sun the reduced plasma pressure results in a correspondingly larger artifical magnetosphere. Also the thrust can be varied electronically instead of mechanically and there's no moving parts.

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