Finnish Electric Solar Sail Nears Implementation

eldavojohn writes "A recent meeting held by the Finnish Meteorological Institute has resulted in plans to build an electric solar sail that will circle the Earth, gaining speed to test its acceleration. The purpose? 'A flight out of the solar system to measure the gas, dust, plasma and magnetic field in the undisturbed interstellar space would perhaps be the "flagship" thing to do,' said Pekka Janhunen, a researcher developing the sail at the FMI. The details and papers of this project (over two years in the making) are also available. I certainly hope it will show more success than the launch of the similar U.S.-Russian venture and its subsequent complete failure."

Comments

Major problem with this

[Kentercat]

So it's a 10 mile across array in an orbit that crosses the altitude of most other satellites, and it crosses the path of the bulk of those satellites at the low point in its orbit when it's moving the fastest. Um. NOTHING COULD POSSIBLY GO WRONG, COULD IT??? They should put it at the Earth-Moon L4 or L5 liberation point instead - no traffic, ample unobstructed solar wind most of the month, and close communications with Earth. That's where a responsible group would put it.

Re:Major problem with this

[Kentercat]

True, but it won't rotate edge-on without a stablization system that can pitch a spun-out array of wires once every orbit, at a variable rate (since in a non-circular orbit the velocity will change radically depending on the position in orbit at a given moment). It's meant to be a solar sail, so it will be oriented to the sun regardless of orbital position. Even if it were edge-on, it would still be 10 miles across. And even if the array consists of thin wires, anything this size can take out satellites, and the fragments can take out other satellites. Ironically, the closer it is to edge-on, the less likely it is that a satellite or space junk component will be able to slip between the wires. Older ABM systems used arrays that unfurled like this to increase the likelihood of taking out the targeted warhead or satellite. Just because the intention of this array is different doesn't mean the result would not be the same.

They could pull it off.

[blind biker]

I have known Finland and Finns for almost 10 years - though I don't know the specifics of this project, I have a strong faith in the finnish high-tech (did you know atomic layer deposition was developed in Finland? And then there's Nokia, and a lot of nanotech research, and their contribution to the ESA and...) plus Finns are quite pedantic, and I mean this in the best possible way. Part of Nokia's success is definitely down to this scholarly approach to technological projects.

Making a better solar sail

[Kim0]

This should make the solar sail about 100 times lighter,
and therefore faster:

http://kim.oyhus.no/Solar_sail.html

Kim Øyhus, the inventor.

Re:Not quite the same thing really

[Anonymous Coward]

Correction: As someone pointed out, the membrane type sails gather momentum from photons rather than ionized solar wind particles. The point still stands that the Finnish sail is a momentum-gathering device that requires no reaction mass. (Unlike a solar-electric ion drive or whatever the GP was thinking about)

The low volume and speed of solar wind particles in comparison to sunlight does limit the performance. For example, you obviously can't go any faster than the solar wind, approx 500km/s near Earth. This is still a lot faster than previous deep space probes (the record is ~15km/s) so if they can get it to approach even 10% of the theoretical limit it'll be great for outer solar system studies.

Re:Not quite the same thing really

[Chrontius]

The solar system is in the middle of something called the "local bubble" - this region was created by an ancient supernova, and is defined by low-density interstellar medium. Also, the ram field generates drag - consider that this is going to look a lot like a giant parachute of magnetic force in front of the ship, that's not very aerodynamic. The drag and the thrust for a conventional Bussard fusion ramjet limit top speed to about 12-14% of lightspeed, which is just about as doable using a conventional fusion rocket design without the ram field. Also, the minimum operating speed of a ramjet is 1-6% of c.

A proton-proton fusion drive has an exhaust velocity of 12% c, so a proton-proton fusion Bussard Ramjet would have a maximum speed of 12% c. You may remember that a spacecraft with a mass ratio that equals e (that is, 2.71828...) will have a total deltaV is exactly equal to the exhaust velocity. So if a conventional fusion rocket with a mass ratio of 3 or more has a better deltaV than a Bussard Ramjet, what's the point of using a ramjet?

Some good reading for you over at Atomic Rocket Ship.

Re:Not quite the same thing really

[Nefarious Wheel]

I doubt any solar sail, no matter the design, is going to take you much further than the termination shock, let alone between stars.

Do you mean that once having achieved the velocity it can from the flux-rich area near our star, it will simply stop? I doubt that gravity at termination shock is going to be enough to slow it down much. Remember that it will have felt that very minor push for quite a few years by then. A few grams thrust isn't very much, but that much continuous per second x60x60x24x365 x however many years it takes to get there, it's likely to be travelling at quite a clip by the time it reaches that point. It will eventually get somewhere between the stars.